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Sample records for silicone microelectrode array

  1. Silicon-substrate microelectrode arrays for parallel recording of neural activity in peripheral and cranial nerves.

    PubMed

    Kovacs, G T; Storment, C W; Halks-Miller, M; Belczynski, C R; Della Santina, C C; Lewis, E R; Maluf, N I

    1994-06-01

    A new process for the fabrication of regeneration microelectrode arrays for peripheral and cranial nerve applications is presented. This type of array is implanted between the severed ends of nerves, the axons of which regenerate through via holes in the silicon and are thereafter held fixed with respect to the microelectrodes. The process described is designed for compatibility with industry-standard CMOS or BiCMOS processes (it does not involve high-temperature process steps nor heavily-doped etch-stop layers), and provides a thin membrane for the via holes, surrounded by a thick silicon supporting rim. Many basic questions remain regarding the optimum via hole and microelectrode geometries in terms of both biological and electrical performance of the implants, and therefore passive versions were fabricated as tools for addressing these issues in on-going work. Versions of the devices were implanted in the rat peroneal nerve and in the frog auditory nerve. In both cases, regeneration was verified histologically and it was observed that the regenerated nerves had reorganized into microfascicles containing both myelinated and unmyelinated axons and corresponding to the grid pattern of the via holes. These microelectrode arrays were shown to allow the recording of action potential signals in both the peripheral and cranial nerve setting, from several microelectrodes in parallel.

  2. Dual-side and three-dimensional microelectrode arrays fabricated from ultra-thin silicon substrates

    NASA Astrophysics Data System (ADS)

    Du, Jiangang; Roukes, Michael L.; Masmanidis, Sotiris C.

    2009-07-01

    A method for fabricating planar implantable microelectrode arrays was demonstrated using a process that relied on ultra-thin silicon substrates, which ranged in thickness from 25 to 50 µm. The challenge of handling these fragile materials was met via a temporary substrate support mechanism. In order to compensate for putative electrical shielding of extracellular neuronal fields, separately addressable electrode arrays were defined on each side of the silicon device. Deep reactive ion etching was employed to create sharp implantable shafts with lengths of up to 5 mm. The devices were flip-chip bonded onto printed circuit boards (PCBs) by means of an anisotropic conductive adhesive film. This scalable assembly technique enabled three-dimensional (3D) integration through formation of stacks of multiple silicon and PCB layers. Simulations and measurements of microelectrode noise appear to suggest that low impedance surfaces, which could be formed by electrodeposition of gold or other materials, are required to ensure an optimal signal-to-noise ratio as well a low level of interchannel crosstalk.

  3. Fabrication of implantable microelectrode arrays by laser cutting of silicone rubber and platinum foil

    NASA Astrophysics Data System (ADS)

    Schuettler, M.; Stiess, S.; King, B. V.; Suaning, G. J.

    2005-03-01

    A new method for fabrication of microelectrode arrays comprised of traditional implant materials is presented. The main construction principle is the use of spun-on medical grade silicone rubber as insulating substrate material and platinum foil as conductor (tracks, pads and electrodes). The silicone rubber and the platinum foil are patterned by laser cutting using an Nd:YAG laser and a microcontroller-driven, stepper-motor operated x-y table. The method does not require expensive clean room facilities and offers an extremely short design-to-prototype time of below 1 day. First prototypes demonstrate a minimal achievable feature size of about 30 µm. The work presented here was carried out at The University of Newcastle, Australia.

  4. Microfabrication of an Implantable silicone Microelectrode array for an epiretinal prosthesis

    SciTech Connect

    Maghribi, Mariam Nader

    2003-06-10

    Millions of people suffering from diseases such as retinitis pigmentosa and macular degeneration are legally blind due to the loss of photoreceptor function. Fortunately a large percentage of the neural cells connected to the photoreceptors remain viable, and electrical stimulation of these cells has been shown to result in visual perception. These findings have generated worldwide efforts to develop a retinal prosthesis device, with the hope of restoring vision. Advances in microfabrication, integrated circuits, and wireless technologies provide the means to reach this challenging goal. This dissertation describes the development of innovative silicone-based microfabrication techniques for producing an implantable microelectrode array. The microelectrode array is a component of an epiretinal prosthesis being developed by a multi-laboratory consortium. This array will serve as the interface between an electronic imaging system and the human eye, directly stimulating retinal neurons via thin film conducting traces. Because the array is intended as a long-term implant, vital biological and physical design requirements must be met. A retinal implant poses difficult engineering challenges due to the size of the intraocular cavity and the delicate retina. Not only does it have to be biocompatible in terms of cytotoxicity and degradation, but it also has to be structurally biocompatible, with regard to smooth edges and high conformability; basically mimicking the biological tissue. This is vital to minimize stress and prevent physical damage to the retina. Also, the device must be robust to withstand the forces imposed on it during fabrication and implantation. In order to meet these biocompatibility needs, the use of non-conventional microfabrication materials such as silicone is required. This mandates the enhancement of currently available polymer-based fabrication techniques and the development of new microfabrication methods. Through an iterative process, devices

  5. Failure mode analysis of silicon-based intracortical microelectrode arrays in non-human primates

    NASA Astrophysics Data System (ADS)

    Barrese, James C.; Rao, Naveen; Paroo, Kaivon; Triebwasser, Corey; Vargas-Irwin, Carlos; Franquemont, Lachlan; Donoghue, John P.

    2013-12-01

    Objective. Brain-computer interfaces (BCIs) using chronically implanted intracortical microelectrode arrays (MEAs) have the potential to restore lost function to people with disabilities if they work reliably for years. Current sensors fail to provide reliably useful signals over extended periods of time for reasons that are not clear. This study reports a comprehensive retrospective analysis from a large set of implants of a single type of intracortical MEA in a single species, with a common set of measures in order to evaluate failure modes. Approach. Since 1996, 78 silicon MEAs were implanted in 27 monkeys (Macaca mulatta). We used two approaches to find reasons for sensor failure. First, we classified the time course leading up to complete recording failure as acute (abrupt) or chronic (progressive). Second, we evaluated the quality of electrode recordings over time based on signal features and electrode impedance. Failure modes were divided into four categories: biological, material, mechanical, and unknown. Main results. Recording duration ranged from 0 to 2104 days (5.75 years), with a mean of 387 days and a median of 182 days (n = 78). Sixty-two arrays failed completely with a mean time to failure of 332 days (median = 133 days) while nine array experiments were electively terminated for experimental reasons (mean = 486 days). Seven remained active at the close of this study (mean = 753 days). Most failures (56%) occurred within a year of implantation, with acute mechanical failures the most common class (48%), largely because of connector issues (83%). Among grossly observable biological failures (24%), a progressive meningeal reaction that separated the array from the parenchyma was most prevalent (14.5%). In the absence of acute interruptions, electrode recordings showed a slow progressive decline in spike amplitude, noise amplitude, and number of viable channels that predicts complete signal loss by about eight years. Impedance measurements showed

  6. Failure mode analysis of silicon-based intracortical microelectrode arrays in non-human primates

    PubMed Central

    Barrese, James C; Rao, Naveen; Paroo, Kaivon; Triebwasser, Corey; Vargas-Irwin, Carlos; Franquemont, Lachlan; Donoghue, John P

    2016-01-01

    Objective Brain–computer interfaces (BCIs) using chronically implanted intracortical microelectrode arrays (MEAs) have the potential to restore lost function to people with disabilities if they work reliably for years. Current sensors fail to provide reliably useful signals over extended periods of time for reasons that are not clear. This study reports a comprehensive retrospective analysis from a large set of implants of a single type of intracortical MEA in a single species, with a common set of measures in order to evaluate failure modes. Approach Since 1996, 78 silicon MEAs were implanted in 27 monkeys (Macaca mulatta). We used two approaches to find reasons for sensor failure. First, we classified the time course leading up to complete recording failure as acute (abrupt) or chronic (progressive). Second, we evaluated the quality of electrode recordings over time based on signal features and electrode impedance. Failure modes were divided into four categories: biological, material, mechanical, and unknown. Main results Recording duration ranged from 0 to 2104 days (5.75 years), with a mean of 387 days and a median of 182 days (n = 78). Sixty-two arrays failed completely with a mean time to failure of 332 days (median = 133 days) while nine array experiments were electively terminated for experimental reasons (mean = 486 days). Seven remained active at the close of this study (mean = 753 days). Most failures (56%) occurred within a year of implantation, with acute mechanical failures the most common class (48%), largely because of connector issues (83%). Among grossly observable biological failures (24%), a progressive meningeal reaction that separated the array from the parenchyma was most prevalent (14.5%). In the absence of acute interruptions, electrode recordings showed a slow progressive decline in spike amplitude, noise amplitude, and number of viable channels that predicts complete signal loss by about eight years. Impedance measurements showed

  7. Stretchable Micro-Electrode Array

    SciTech Connect

    Maghribi, M; Hamilton, J; Polla, D; Rose, K; Wilson, T; Krulevitch, P

    2002-03-08

    This paper focuses on the design consideration, fabrication processes and preliminary testing of the stretchable micro-electrode array. We are developing an implantable, stretchable micro-electrode array using polymer-based microfabrication techniques. The device will serve as the interface between an electronic imaging system and the human eye, directly stimulating retinal neurons via thin film conducting traces and electroplated electrodes. The metal features are embedded within a thin ({approx}50 micron) substrate fabricated using poly (dimethylsiloxane) (PDMS), a biocompatible elastomeric material that has very low water permeability. The conformable nature of PDMS is critical for ensuring uniform contact with the curved surface of the retina. To fabricate the device, we developed unique processes for metalizing PDMS to produce robust traces capable of maintaining conductivity when stretched (5%, SD 1.5), and for selectively passivating the conductive elements. An in situ measurement of residual strain in the PDMS during curing reveals a tensile strain of 10%, explaining the stretchable nature of the thin metalized devices.

  8. Revealing neuronal function through microelectrode array recordings

    PubMed Central

    Obien, Marie Engelene J.; Deligkaris, Kosmas; Bullmann, Torsten; Bakkum, Douglas J.; Frey, Urs

    2015-01-01

    Microelectrode arrays and microprobes have been widely utilized to measure neuronal activity, both in vitro and in vivo. The key advantage is the capability to record and stimulate neurons at multiple sites simultaneously. However, unlike the single-cell or single-channel resolution of intracellular recording, microelectrodes detect signals from all possible sources around every sensor. Here, we review the current understanding of microelectrode signals and the techniques for analyzing them. We introduce the ongoing advancements in microelectrode technology, with focus on achieving higher resolution and quality of recordings by means of monolithic integration with on-chip circuitry. We show how recent advanced microelectrode array measurement methods facilitate the understanding of single neurons as well as network function. PMID:25610364

  9. Dielectrophoretic immobilisation of antibodies on microelectrode arrays.

    PubMed

    Otto, Saskia; Kaletta, Udo; Bier, Frank F; Wenger, Christian; Hölzel, Ralph

    2014-03-07

    A silicon based chip device with a regular array of more than 100,000 cylindrical sub-microelectrodes has been developed for the dielectrophoretic (DEP) manipulation of nanoparticles and molecules in solution. It was fabricated by a standard CMOS (complementary metal oxide semiconductor) compatible process. The distribution of the electrical field gradient was calculated to predict the applicability of the setup. Heating due to field application was determined microscopically using a temperature sensitive fluorescent dye. Depending on voltage and frequency, temperature increase was found to be compatible with protein function. Successful field controlled immobilisation of biomolecules from solution was demonstrated with the autofluorescent protein R-phycoerythrin (RPE) and with fluorescently labelled IgG antibodies. Biological activity after DEP application was proven by immobilisation of an anti-RPE antibody and subsequent binding of RPE. These results demonstrate that the developed chip system allows the directed immobilisation of proteins onto microelectrodes by dielectrophoresis without the need for any chemical modification and that protein function is preserved. Being based on standard lithographical methods, further miniaturisation and on-chip integration of electronics towards a multiparameter single cell analysis system appear near at hand.

  10. Chronic neural recordings using silicon microelectrode arrays electrochemically deposited with a poly(3,4-ethylenedioxythiophene) (PEDOT) film.

    PubMed

    Ludwig, Kip A; Uram, Jeffrey D; Yang, Junyan; Martin, David C; Kipke, Daryl R

    2006-03-01

    Conductive polymer coatings can be used to modify traditional electrode recording sites with the intent of improving the long-term performance of cortical microelectrodes. Conductive polymers can drastically decrease recording site impedance, which in turn is hypothesized to reduce thermal noise and signal loss through shunt pathways. Moreover, conductive polymers can be seeded with agents aimed at promoting neural growth toward the recording sites or minimizing the inherent immune response. The end goal of these efforts is to generate an ideal long-term interface between the recording electrode and surrounding tissue. The goal of this study was to refine a method to electrochemically deposit surfactant-templated ordered poly(3,4-ethylenedioxythiophene) (PEDOT) films on the recording sites of standard 'Michigan' probes and to evaluate the efficacy of these modified sites in recording chronic neural activity. PEDOT-coated site performance was compared to control sites over a six-week evaluation period in terms of impedance spectroscopy, signal-to-noise ratio, number of viable unit potentials recorded and local field potential recordings. PEDOT sites were found to outperform control sites with respect to signal-to-noise ratio and number of viable unit potentials. The benefit of reduced initial impedance, however, was mitigated by the impedance contribution of typical silicon electrode encapsulation. Coating sites with PEDOT also reduced the amount of low-frequency drift evident in local field potential recordings. These findings indicate that electrode sites electrochemically deposited with PEDOT films are suitable for recording neural activity in vivo for extended periods. This study also provided a unique opportunity to monitor how neural recording characteristics develop over the six weeks following implantation.

  11. Chronic in vivo stability assessment of carbon fiber microelectrode arrays

    NASA Astrophysics Data System (ADS)

    Patel, Paras R.; Zhang, Huanan; Robbins, Matthew T.; Nofar, Justin B.; Marshall, Shaun P.; Kobylarek, Michael J.; Kozai, Takashi D. Y.; Kotov, Nicholas A.; Chestek, Cynthia A.

    2016-12-01

    Objective. Individual carbon fiber microelectrodes can record unit activity in both acute and semi-chronic (∼1 month) implants. Additionally, new methods have been developed to insert a 16 channel array of carbon fiber microelectrodes. Before assessing the in vivo long-term viability of these arrays, accelerated soak tests were carried out to determine the most stable site coating material. Next, a multi-animal, multi-month, chronic implantation study was carried out with carbon fiber microelectrode arrays and silicon electrodes. Approach. Carbon fibers were first functionalized with one of two different formulations of PEDOT and subjected to accelerated aging in a heated water bath. After determining the best PEDOT formula to use, carbon fiber arrays were chronically implanted in rat motor cortex. Some rodents were also implanted with a single silicon electrode, while others received both. At the end of the study a subset of animals were perfused and the brain tissue sliced. Tissue sections were stained for astrocytes, microglia, and neurons. The local reactive responses were assessed using qualitative and quantitative methods. Main results. Electrophysiology recordings showed the carbon fibers detecting unit activity for at least 3 months with average amplitudes of ∼200 μV. Histology analysis showed the carbon fiber arrays with a minimal to non-existent glial scarring response with no adverse effects on neuronal density. Silicon electrodes showed large glial scarring that impacted neuronal counts. Significance. This study has validated the use of carbon fiber microelectrode arrays as a chronic neural recording technology. These electrodes have demonstrated the ability to detect single units with high amplitude over 3 months, and show the potential to record for even longer periods. In addition, the minimal reactive response should hold stable indefinitely, as any response by the immune system may reach a steady state after 12 weeks.

  12. Characterization of a light switchable microelectrode array for retinal prosthesis

    NASA Astrophysics Data System (ADS)

    Zhang, Xinyi; Xiong, Tao; Chiou, Pei-Yu; Li, Zhihong

    2011-12-01

    A light switchable microelectrode array for retinal prosthesis, which is performed with the photosensitive conductivity of hydrogenated amorphous silicon (a-Si:H) and of more advantages over the two major current retinal prosthetic categories, is characterized. Sensitivity to different visible wavelengths and light intensities are verified as well. Preliminary impedance test invitro shows appropriate impedance for neuron stimulation applications. It is indicated that such device provides a promising potential to restore a certain degree of visual function.

  13. Fabrication of a flexible penetrating microelectrode array for use on curved surfaces of neural tissues

    NASA Astrophysics Data System (ADS)

    Byun, Donghak; Cho, Sung Joon; Kim, Sohee

    2013-12-01

    Conventionally, invasive neural microelectrodes for recording neuronal signals or stimulating the nervous system have been fabricated based on silicon substrate mainly due to well-established manufacturing processes. However, these silicon-based microelectrode devices have an issue of mechanical stability caused by the absence of flexibility when implanted onto curved surfaces of tissues. In this paper, a flexible and penetrating microelectrode array, a hybrid structure composed of silicon and elastomer, was devised and fabricated by bulk micromachining technologies. The structure uses individual silicon needles as independent electrodes in a square array and polydimethysiloxane (PDMS) as a base to support the needles. The dimensions of the electrode array and the needles are adjustable, depending on the number of needles, the pitch between the needles and the targeted penetration depth of the neural tissue. For mechanical characterization, the adhesion between PDMS and silicon was evaluated and the flexibility and integrity of the fabricated structure were investigated through flexural test and insertion test. Also, the electrochemical impedance spectroscopy of the electrodes was measured. The results suggest that the proposed microelectrode array is promising for use in neuronal recording and stimulation over curved surfaces such as cortical surface and peripheral nerves with larger curvatures.

  14. Microelectrode array fabrication by electrical discharge machining and chemical etching.

    PubMed

    Fofonoff, Timothy A; Martel, Sylvain M; Hatsopoulos, Nicholas G; Donoghue, John P; Hunter, Ian W

    2004-06-01

    Wire electrical discharge machining (EDM), with a complementary chemical etching process, is explored and assessed as a method for developing microelectrode array assemblies for intracortically recording brain activity. Assembly processes based on these methods are highlighted, and results showing neural activity successfully recorded from the brain of a mouse using an EDM-based device are presented. Several structures relevant to the fabrication of microelectrode arrays are also offered in order to demonstrate the capabilities of EDM.

  15. Graphene microelectrode arrays for neural activity detection.

    PubMed

    Du, Xiaowei; Wu, Lei; Cheng, Ji; Huang, Shanluo; Cai, Qi; Jin, Qinghui; Zhao, Jianlong

    2015-09-01

    We demonstrate a method to fabricate graphene microelectrode arrays (MEAs) using a simple and inexpensive method to solve the problem of opaque electrode positions in traditional MEAs, while keeping good biocompatibility. To study the interface differences between graphene-electrolyte and gold-electrolyte, graphene and gold electrodes with a large area were fabricated. According to the simulation results of electrochemical impedances, the gold-electrolyte interface can be described as a classical double-layer structure, while the graphene-electrolyte interface can be explained by a modified double-layer theory. Furthermore, using graphene MEAs, we detected the neural activities of neurons dissociated from Wistar rats (embryonic day 18). The signal-to-noise ratio of the detected signal was 10.31 ± 1.2, which is comparable to those of MEAs made with other materials. The long-term stability of the MEAs is demonstrated by comparing differences in Bode diagrams taken before and after cell culturing.

  16. Neurotoxicity testing using Microelectrode Arrays (MEAs): a growing trend

    EPA Science Inventory

    Microelectrode arrays (MEAs) are groups of extracellular electrodes that are 10-30 microns in diameter and can be utilized in vivo or in vitro. For in vitro uses, an MEA typically contains up to 64 electrodes and can be utilized to measure the activity of cells and tissues that a...

  17. Highly sensitive reduced graphene oxide microelectrode array sensor.

    PubMed

    Ng, Andrew M H; Kenry; Teck Lim, Chwee; Low, Hong Yee; Loh, Kian Ping

    2015-03-15

    Reduced graphene oxide (rGO) has been fabricated into a microelectrode array (MEA) using a modified nanoimprint lithography (NIL) technique. Through a modified NIL process, the rGO MEA was fabricated by a self-alignment of conducting Indium Tin Oxide (ITO) and rGO layer without etching of the rGO layer. The rGO MEA consists of an array of 10μm circular disks and microelectrode signature has been found at a pitch spacing of 60μm. The rGO MEA shows a sensitivity of 1.91nAμm(-1) to dopamine (DA) without the use of mediators or functionalization of the reduced graphene oxide (rGO) active layer. The performance of rGO MEA remains stable when tested under highly resistive media using a continuous flow set up, as well as when subjecting it to mechanical stress. The successful demonstration of NIL for fabricating rGO microelectrodes on flexible substrate presents a route for the large scale fabrication of highly sensitive, flexible and thin biosensing platform.

  18. Highly doped polycrystalline silicon microelectrodes reduce noise in neuronal recordings in vivo.

    PubMed

    Saha, Rajarshi; Jackson, Nathan; Patel, Chetan; Muthuswamy, Jit

    2010-10-01

    The aims of this study are to 1) experimentally validate for the first time the nonlinear current-potential characteristics of bulk doped polycrystalline silicon in the small amplitude voltage regimes (0-200 μV) and 2) test if noise amplitudes ( 0-15 μV ) from single neuronal electrical recordings get selectively attenuated in doped polycrystalline silicon microelectrodes due to the above property. In highly doped polycrystalline silicon, bulk resistances of several hundred kilo-ohms were experimentally measured for voltages typical of noise amplitudes and 9-10 kΩ for voltages typical of neural signal amplitudes ( > 150-200 μV). Acute multiunit measurements and noise measurements were made in n=6 and n=8 anesthetized adult rats, respectively, using polycrystalline silicon and tungsten microelectrodes. There was no significant difference in the peak-to-peak amplitudes of action potentials recorded from either microelectrode (p > 0.10). However, noise power in the recordings from tungsten microelectrodes (26.36 ±10.13 pW) was significantly higher than the corresponding value in polycrystalline silicon microelectrodes (7.49 ±2.66 pW). We conclude that polycrystalline silicon microelectrodes result in selective attenuation of noise power in electrical recordings compared to tungsten microelectrodes. This reduction in noise compared to tungsten microelectrodes is likely due to the exponentially higher bulk resistances offered by highly doped bulk polycrystalline silicon in the range of voltages corresponding to noise in multiunit measurements.

  19. Boron doped diamond microelectrodes arrays for electrochemical detection in HPLC.

    PubMed

    Mahé, Eric; Devilliers, Didier; Dardoize, François

    2015-01-01

    Boron doped diamond microelectrodes arrays (MEA) have been prepared in order to be used as new amperometric sensors in electrochemical cells for HPLC detectors. The following parameters were studied: number and diameter (15-40 µm) of the electrodes, distance between them (50-240 µm), and effect of the flow rate (0.1-3 mL/min). It was thus possible to find the optimum value of the parameters which give a good signal/noise ratio in the chronoamperometric responses, with a size of the electrochemical sensors as small as possible.

  20. Interdigitated array microelectrode capacitive sensor for detection of paraffinophilic mycobacteria

    NASA Astrophysics Data System (ADS)

    Sampson, Andrew M.; Peterson, Erik T. K.; Papautsky, Ian

    2008-02-01

    Mycobacterium Avium Complex (MAC) is an opportunistic pathogen that threatens public health and has high clinical relevance. While culture-based and molecular biology techniques for identification are available, these methods are prone to error and require weeks to perform. There is a critical need for improved portable lab-on-a-chip sensor technology which will enable accurate and rapid point-of-care detection of these microorganisms. In this work, a new capacitive sensing strategy is explored utilizing interdigitated array (IDA) microelectrodes and exploiting the paraffinophilic nature of MAC. In this approach, paraffin wax is deposited over IDA microelectrodes to selectively extract these microorganisms from samples. As bacteria consume the dielectric paraffin layer, the charging current of the IDA capacitor changes to facilitate detection. Several IDA geometries were designed and simulated using CFD-ACE+ modeling software and compared with mathematical models. Capacitance of fabricated devices was determined using a charge-based capacitance measurement (CBCM) technique. Modeling and experimental results were in good agreement. Detection of femto-Farad changes in capacitance is possible, making this a feasible technique for sensing small changes in the paraffin for detection of paraffinophilic MAC.

  1. Digital microfluidic operations on micro-electrode dot array architecture.

    PubMed

    Wang, G; Teng, D; Fan, S-K

    2011-12-01

    As digital microfluidics-based biochips find more applications, their complexity is expected to increase significantly owing to the trend of multiple and concurrent assays on the chip. There is a pressing need to deliver a top-down design methodology that the biochip designer can leverage the same level of computer-aided design support as the semi-conductor industry now does. Moreover, as microelectronics fabrication technology is scaling up and integrated device performance is improving, it is expected that these microfluidic biochips will be integrated with microelectronic components in next-generation system-on-chip designs. This study presents the analysis and experiments of digital microfluidic operations on a novel electrowetting-on-dielectric-based 'micro-electrode dot array architecture' that fosters a development path for hierarchical top-down design approach for digital microfluidics. The proposed architecture allows dynamic configurations and activations of identical basic microfluidic unit called 'micro-electrode cells' to design microfluidic components, layouts, routing, microfluidic operations and applications of the biochip hierarchically. Fundamental microfluidic operations have been successfully performed by the architecture. In addition, this novel architecture demonstrates a number of advantages and flexibilities over the conventional digital microfluidics in performing advanced microfluidic operations.

  2. BioMEA: a versatile high-density 3D microelectrode array system using integrated electronics.

    PubMed

    Charvet, Guillaume; Rousseau, Lionel; Billoint, Olivier; Gharbi, Sadok; Rostaing, Jean-Pierre; Joucla, Sébastien; Trevisiol, Michel; Bourgerette, Alain; Chauvet, Philippe; Moulin, Céline; Goy, François; Mercier, Bruno; Colin, Mikael; Spirkovitch, Serge; Fanet, Hervé; Meyrand, Pierre; Guillemaud, Régis; Yvert, Blaise

    2010-04-15

    Microelectrode arrays (MEAs) offer a powerful tool to both record activity and deliver electrical microstimulations to neural networks either in vitro or in vivo. Microelectronics microfabrication technologies now allow building high-density MEAs containing several hundreds of microelectrodes. However, dense arrays of 3D micro-needle electrodes, providing closer contact with the neural tissue than planar electrodes, are not achievable using conventional isotropic etching processes. Moreover, increasing the number of electrodes using conventional electronics is difficult to achieve into compact devices addressing all channels independently for simultaneous recording and stimulation. Here, we present a full modular and versatile 256-channel MEA system based on integrated electronics. First, transparent high-density arrays of 3D-shaped microelectrodes were realized by deep reactive ion etching techniques of a silicon substrate reported on glass. This approach allowed achieving high electrode aspect ratios, and different shapes of tip electrodes. Next, we developed a dedicated analog 64-channel Application Specific Integrated Circuit (ASIC) including one amplification stage and one current generator per channel, and analog output multiplexing. A full modular system, called BIOMEA, has been designed, allowing connecting different types of MEAs (64, 128, or 256 electrodes) to different numbers of ASICs for simultaneous recording and/or stimulation on all channels. Finally, this system has been validated experimentally by recording and electrically eliciting low-amplitude spontaneous rhythmic activity (both LFPs and spikes) in the developing mouse CNS. The availability of high-density MEA systems with integrated electronics will offer new possibilities for both in vitro and in vivo studies of large neural networks.

  3. Piezo-Driven Vibrating Insertion Device for Microelectrode Array

    NASA Astrophysics Data System (ADS)

    Noda, Takahiro; Kanzaki, Ryohei; Takahashi, Hirokazu

    Microelectrode arrays are commonly used to measure neural activities in the brain, and arrays with some 100 electrodes are commercially available to date. However, insertion of a dense grid array deforms the brain, resulting in deterioration of the measurements. In order to overcome this problem, we propose a piezo-driven vibrating insertion device to reduce the insertion-induced deformation of the brain. We attempted under various conditions to insert the array into an agarose substrate, whose hardness was adjusted to that of the cerebral cortex of rats. Our experiments demonstrated that inverse-sawtooth vibration reduced the insertion-induced deformation of the substrate in proportion to the logarithm of an upstroke velocity when the velocity was higher than 10 mm/s, and vibrating insertion of the maximum velocity at 36.7 mm/s reduced the deformation by up to 40% as compared to insertion without vibration. In addition, we tested the vibrating insertion device in an electrophysiological experiment in the rat auditory cortex in vivo, and successfully measured tone-evoked neuronal activities.

  4. Acetylcholinesterase biosensor for carbaryl detection based on interdigitated array microelectrodes.

    PubMed

    Gong, Zhili; Guo, Yemin; Sun, Xia; Cao, Yaoyao; Wang, Xiangyou

    2014-10-01

    In this study, an acetylcholinesterase (AChE) biosensor with superior accuracy and sensitivity was successfully developed based on interdigitated array microelectrodes (IAMs). IAMs have a series of parallel microband electrodes with alternating microbands connected together. Chitosan was used as the enzyme immobilization material, and AChE was used as the model enzyme for carbaryl detection to fabricate AChE biosensor. Electrochemical impedance spectroscopy was used in conjunction with the fabricated biosensor to detect pesticide residues. Based on the inhibition of pesticides on the AChE activity, using carbaryl as model compounds, the biosensor exhibited a wide range, low detection limit, and high stability. Moreover, the biosensor can also be used as a new promising tool for pesticide residue analysis.

  5. Highly Doped Polycrystalline Silicon Microelectrodes Reduce Noise in Neuronal Recordings In Vivo

    PubMed Central

    Saha, Rajarshi; Jackson, Nathan; Patel, Chetan; Muthuswamy, Jit

    2013-01-01

    The aims of this study are to 1) experimentally validate for the first time the nonlinear current-potential characteristics of bulk doped polycrystalline silicon in the small amplitude voltage regimes (0–200 μV) and 2) test if noise amplitudes (0–15 μV) from single neuronal electrical recordings get selectively attenuated in doped polycrystalline silicon microelectrodes due to the above property. In highly doped polycrystalline silicon, bulk resistances of several hundred kilo-ohms were experimentally measured for voltages typical of noise amplitudes and 9–10 kΩ for voltages typical of neural signal amplitudes (>150–200 μV). Acute multiunit measurements and noise measurements were made in n = 6 and n = 8 anesthetized adult rats, respectively, using polycrystalline silicon and tungsten microelectrodes. There was no significant difference in the peak-to-peak amplitudes of action potentials recorded from either microelectrode (p > 0.10). However, noise power in the recordings from tungsten microelectrodes (26.36 ± 10.13 pW) was significantly higher (p < 0.001) than the corresponding value in polycrystalline silicon microelectrodes (7.49 ± 2.66 pW). We conclude that polycrystalline silicon microelectrodes result in selective attenuation of noise power in electrical recordings compared to tungsten microelectrodes. This reduction in noise compared to tungsten microelectrodes is likely due to the exponentially higher bulk resistances offered by highly doped bulk polycrystalline silicon in the range of voltages corresponding to noise in multiunit measurements. PMID:20667815

  6. An array of microactuated microelectrodes for monitoring single-neuronal activity in rodents.

    PubMed

    Muthuswamy, Jit; Okandan, Murat; Gilletti, Aaron; Baker, Michael S; Jain, Tilak

    2005-08-01

    Arrays of microelectrodes used for monitoring single- and multi-neuronal action potentials often fail to record from the same population of neurons over a period of time for several technical and biological reasons. We report here a novel Neural Probe chip with a 3-channel microactuated microelectrode array that will enable precise repositioning of the individual microelectrodes within the brain tissue after implantation. Thermal microactuators and associated microelectrodes in the Neural Probe chip are microfabricated using the Sandia's Ultraplanar Multi-level MEMS Technology (SUMMiTV) process, a 5-layer polysilicon micromachining technology of the Sandia National labs, Albuquerque, NM. The Neural Probe chip enables precise bi-directional positioning of the microelectrodes in the brain with a step resolution in the order of 8.8 microm. The thermal microactuators allow for a linear translation of the microelectrodes of up to 5 mm in either direction making it suitable for positioning microelectrodes in deep structures of a rodent brain. The overall translation in either direction was reduced to approximately 2 mm after insulation of the microelectrodes with epoxy for monitoring multi-unit activity. Single unit recordings were obtained from the somatosensory cortex of adult rats over a period of three days demonstrating the feasibility of this technology. Further optimization of the microelectrode insulation and chip packaging will be necessary before this technology can be validated in chronic experiments.

  7. An Array of Microactuated Microelectrodes for Monitoring Single-Neuronal Activity in Rodents

    PubMed Central

    Okandan, Murat; Gilletti, Aaron; Baker, Michael S.; Jain, Tilak

    2006-01-01

    Arrays of microelectrodes used for monitoring single-and multi-neuronal action potentials often fail to record from the same population of neurons over a period of time for several technical and biological reasons. We report here a novel Neural Probe chip with a 3-channel microactuated microelectrode array that will enable precise repositioning of the individual microelectrodes within the brain tissue after implantation. Thermal microactuators and associated microelectrodes in the Neural Probe chip are microfabricated using the Sandia’s Ultraplanar Multi-level MEMS Technology (SUMMiTV) process, a 5-layer polysilicon microma-chining technology of the Sandia National labs, Albuquerque, NM. The Neural Probe chip enables precise bi-directional positioning of the microelectrodes in the brain with a step resolution in the order of 8.8μm. The thermal microactuators allow for a linear translation of the microelectrodes of up to 5 mm in either direction making it suitable for positioning microelectrodes in deep structures of a rodent brain. The overall translation in either direction was reduced to approximately 2 mm after insulation of the microelectrodes with epoxy for monitoring multi-unit activity. Single unit recordings were obtained from the somatosensory cortex of adult rats over a period of three days demonstrating the feasibility of this technology. Further optimization of the microelectrode insulation and chip packaging will be necessary before this technology can be validated in chronic experiments. PMID:16119243

  8. Single nucleotide polymorphism (SNP) detection using microelectrode biochip array

    NASA Astrophysics Data System (ADS)

    Choi, Yong-Sung; Lee, Kyung-Sup; Park, Dae-Hee

    2005-10-01

    In this paper, a microelectrode array DNA chip was fabricated on a glass slide using photolithography technology. Several probe DNAs with mercaptohexyl moiety at their 5' end were immobilized on the gold electrodes by a DNA arrayer utilizing the affinity between gold and sulfur. Then target DNAs were hybridized and reacted with Hoechst 33258, which is a DNA minor groove binder and electrochemically active dye. Cyclic voltammetry in a 5 mM ferricyanide/ferrocyanide solution at 100 mV s-1 confirmed the immobilization of probe DNA on the gold electrodes. Linear sweep voltammetry or cyclic voltammetry showed a difference between target DNA and control DNA in the anodic peak current values. This was derived from Hoechst 33258 concentrated at the electrode surface through association with formed hybrids. It is suggested that this DNA chip could recognize sequence specific genes. It is also suggested that a multichannel electrochemical DNA microarray is useful to develop a portable device for a clinical gene diagnostic system.

  9. A MULTIPLEXED ASSAY FOR DETERMINATION OF NEUROTOXICANT EFFECTS ON SPONTANEOUS NETWORK ACTIVITY AND CELL VIABILITY FROM MICROELECTRODE ARRAYS

    EPA Science Inventory

    AbstractTITLE: A MULTIPLEXED ASSAY FOR DETERMINATION OF NEUROTOXICANT EFFECTS ON SPONTANEOUS NETWORK ACTIVITY AND CELL VIABILITY FROM MICROELECTRODE ARRAYSABSTRACT BODY: Microelectrode array (MEA) recordings are increasingly being used as an in vitro method to detect and characte...

  10. Close-Packed Silicon Microelectrodes for Scalable Spatially Oversampled Neural Recording

    PubMed Central

    Scholvin, Jörg; Kinney, Justin P.; Bernstein, Jacob G.; Moore-Kochlacs, Caroline; Kopell, Nancy; Fonstad, Clifton G.; Boyden, Edward S.

    2015-01-01

    Objective Neural recording electrodes are important tools for understanding neural codes and brain dynamics. Neural electrodes that are close-packed, such as in tetrodes, enable spatial oversampling of neural activity, which facilitates data analysis. Here we present the design and implementation of close-packed silicon microelectrodes, to enable spatially oversampled recording of neural activity in a scalable fashion. Methods Our probes are fabricated in a hybrid lithography process, resulting in a dense array of recording sites connected to submicron dimension wiring. Results We demonstrate an implementation of a probe comprising 1000 electrode pads, each 9 × 9 μm, at a pitch of 11 μm. We introduce design automation and packaging methods that allow us to readily create a large variety of different designs. Significance Finally, we perform neural recordings with such probes in the live mammalian brain that illustrate the spatial oversampling potential of closely packed electrode sites. PMID:26699649

  11. A low noise multichannel integrated circuit for recording neuronal signals using microelectrode arrays.

    PubMed

    Dabrowski, W; Grybos, P; Litke, A M

    2004-02-15

    This paper reports on the development of a fully integrated 32-channel integrated circuit (IC) for recording neuronal signals in neurophysiological experiments using microelectrode arrays. The IC consists of 32 channels of low-noise preamplifiers and bandpass filters, and an output analog multiplexer. The continuous-time RC active filters have a typical passband of 20-2000 Hz; the low and the high cut-off frequencies can be separately controlled by external reference currents. This chip provides a satisfactory signal-to-noise ratio for neuronal signals with amplitudes greater than 50 microV. For the nominal passband setting, an equivalent input noise of 3 microV rms has been achieved. A single channel occupies 0.35 mm(2) of silicon area and dissipates 1.7 mW of power. The chip was fabricated in a 0.7 microm CMOS process.

  12. Fabrication and testing of polyimide-based microelectrode arrays for cortical mapping of evoked potentials.

    PubMed

    Myllymaa, Sami; Myllymaa, Katja; Korhonen, Hannu; Töyräs, Juha; Jääskeläinen, Juha E; Djupsund, Kaj; Tanila, Heikki; Lappalainen, Reijo

    2009-06-15

    Modern microfabrication techniques make it possible to develop microelectrode arrays that may be utilized not only in neurophysiological research but also in the clinic, e.g. in neurosurgery and as elements of neural prostheses. The aim of this study was to test whether a flexible microelectrode array is suitable for recording cortical surface field potentials in rats. Polyimide-based microelectrode arrays were fabricated by utilizing microfabrication techniques e.g. photolithography and magnetron sputter deposition. The present microelectrode array consists of eight platinum microelectrodes (round-shaped, Ø: 200 microm), transmission lines and connector pads sandwiched between two thin layers of biocompatible polyimide. The microelectrode arrays were electrochemically characterized by impedance spectroscopy in physiological saline solution and successfully tested in vivo by conducting acute and chronic measurements of evoked potentials on the surface of rat cortex. The arrays proved excellent flexibility and mechanical strength during handling and implantation onto the surface of cortex. The excellent electrochemical characteristics and stable in vivo recordings with high spatiotemporal resolution highlight the potential of these arrays. The fabrication protocol described here allows implementation of several other neural interfaces with different layouts, material selections or target areas either for recording or stimulation purposes.

  13. Evaluation of a Microelectrode Arrays for Neurotoxicity Testing Using a Chemical Training Set

    EPA Science Inventory

    Microelectrode array (MEA) approaches have been proposed as a tool for detecting functional changes in electrically active cells, including neurons, exposed to drugs, chemicals, or particles. However, conventional single well MEA systems lack the throughput necessary for screenin...

  14. Microelectrode Arrays: A Physiologically-based Neurotoxicity Testing Platform for the 21st Century

    EPA Science Inventory

    Microelectrode Arrays (MEAs) have been in use over the past decade and a half to study multiple aspects ofelectrically excitable cells. Inparticular, MEAs have been applied to explore the pharmacological and toxicological effects ofnumerous compounds on spontaneous activity ofneu...

  15. Evaluation of Multi-Well Microelectrode Arrays for Neurotoxicity Screening Using a Chemical Training Set

    EPA Science Inventory

    Microelectrode array (MEA) approaches have been proposed as a tool for detecting functional changes in electrically-excitable cells, including neurons, exposed to drugs, chemical or particles. However, conventional single well-MEA systems lack the throughput necessary for screen...

  16. Low Frequency Activity of Cortical Networks on Microelectrode Arrays is Differentially Altered by Bicuculline and Carbaryl

    EPA Science Inventory

    Thousands of chemicals need to be characterized for their neurotoxicity potential. Neurons grown on microelectrode arrays (MEAs) are an in vitro model used to screen chemicals for functional effects on neuronal networks. Typically, after removal of low frequency components, effec...

  17. A Tapered Aluminium Microelectrode Array for Improvement of Dielectrophoresis-Based Particle Manipulation

    PubMed Central

    Buyong, Muhamad Ramdzan; Larki, Farhad; Faiz, Mohd Syafiq; Hamzah, Azrul Azlan; Yunas, Jumrail; Majlis, Burhanuddin Yeop

    2015-01-01

    In this work, the dielectrophoretic force (FDEP) response of Aluminium Microelectrode Arrays with tapered profile is investigated through experimental measurements and numerical simulations. A standard CMOS processing technique with a step for the formation of a tapered profile resist is implemented in the fabrication of Tapered Aluminium Microelectrode Arrays (TAMA). The FDEP is investigated through analysis of the Clausius-Mossotti factor (CMF) and cross-over frequency (fxo). The performance of TAMA with various side wall angles is compared to that of microelectrodes with a straight cut sidewall profile over a wide range of frequencies through FEM numerical simulations. Additionally, electric field measurement (EFM) is performed through scanning probe microscopy (SPM) in order to obtain the region of force focus in both platforms. Results showed that the tapered profile microelectrodes with angles between 60° and 70° produce the highest electric field gradient on the particles. Also, the region of the strongest electric field in TAMA is located at the bottom and top edge of microelectrode while the strongest electric field in microelectrodes with straight cut profile is found at the top corner of the microelectrode. The latter property of microelectrodes improves the probability of capturing/repelling the particles at the microelectrode’s side wall. PMID:25970255

  18. Polycrystalline-Diamond MEMS Biosensors Including Neural Microelectrode-Arrays.

    PubMed

    Varney, Michael W; Aslam, Dean M; Janoudi, Abed; Chan, Ho-Yin; Wang, Donna H

    2011-08-15

    Diamond is a material of interest due to its unique combination of properties, including its chemical inertness and biocompatibility. Polycrystalline diamond (poly-C) has been used in experimental biosensors that utilize electrochemical methods and antigen-antibody binding for the detection of biological molecules. Boron-doped poly-C electrodes have been found to be very advantageous for electrochemical applications due to their large potential window, low background current and noise, and low detection limits (as low as 500 fM). The biocompatibility of poly-C is found to be comparable, or superior to, other materials commonly used for implants, such as titanium and 316 stainless steel. We have developed a diamond-based, neural microelectrode-array (MEA), due to the desirability of poly-C as a biosensor. These diamond probes have been used for in vivo electrical recording and in vitro electrochemical detection. Poly-C electrodes have been used for electrical recording of neural activity. In vitro studies indicate that the diamond probe can detect norepinephrine at a 5 nM level. We propose a combination of diamond micro-machining and surface functionalization for manufacturing diamond pathogen-microsensors.

  19. Polycrystalline-Diamond MEMS Biosensors Including Neural Microelectrode-Arrays

    PubMed Central

    Varney, Michael W.; Aslam, Dean M.; Janoudi, Abed; Chan, Ho-Yin; Wang, Donna H.

    2011-01-01

    Diamond is a material of interest due to its unique combination of properties, including its chemical inertness and biocompatibility. Polycrystalline diamond (poly-C) has been used in experimental biosensors that utilize electrochemical methods and antigen-antibody binding for the detection of biological molecules. Boron-doped poly-C electrodes have been found to be very advantageous for electrochemical applications due to their large potential window, low background current and noise, and low detection limits (as low as 500 fM). The biocompatibility of poly-C is found to be comparable, or superior to, other materials commonly used for implants, such as titanium and 316 stainless steel. We have developed a diamond-based, neural microelectrode-array (MEA), due to the desirability of poly-C as a biosensor. These diamond probes have been used for in vivo electrical recording and in vitro electrochemical detection. Poly-C electrodes have been used for electrical recording of neural activity. In vitro studies indicate that the diamond probe can detect norepinephrine at a 5 nM level. We propose a combination of diamond micro-machining and surface functionalization for manufacturing diamond pathogen-microsensors. PMID:25586924

  20. Human Islets Exhibit Electrical Activity on Microelectrode Arrays (MEA).

    PubMed

    Schönecker, S; Kraushaar, U; Guenther, E; Gerst, F; Ullrich, S; Häring, H-U; Königsrainer, A; Barthlen, W; Drews, G; Krippeit-Drews, P

    2015-05-01

    This study demonstrates for the first time that the microelectrode array (MEA) technique allows analysis of electrical activity of islets isolated from human biopsies. We have shown before that this method, i.e., measuring beta cell electrical activity with extracellular electrodes, is a powerful tool to assess glucose responsiveness of isolated murine islets. In the present study, human islets were shown to exhibit glucose-dependent oscillatory electrical activity. The glucose responsiveness could be furthermore demonstrated by an increase of insulin secretion in response to glucose. Electrical activity was increased by tolbutamide and inhibited by diazoxide. In human islets bursts of electrical activity were markedly blunted by the Na(+) channel inhibitor tetrodotoxin which does not affect electrical activity in mouse islets. Thus, the MEA technique emerges as a powerful tool to decipher online the unique features of human islets.Additionally, this technique will enable research with human islets even if only a few islets are available and it will allow a fast and easy test of metabolic integrity of islets destined for transplantation.

  1. Investigating brain functional evolution and plasticity using microelectrode array technology.

    PubMed

    Napoli, Alessandro; Obeid, Iyad

    2015-10-01

    The aim of this work was to investigate long and short-term plasticity responsible for memory formation in dissociated neuronal networks. In order to address this issue, a set of experiments was designed and implemented in which the microelectrode array electrode grid was divided into four quadrants, two of which were chronically stimulated, every two days for one hour with a stimulation paradigm that varied over time. Overall network and quadrant responses were then analyzed to quantify what level of plasticity took place in the network and how this was due to the stimulation interruption. The results demonstrate that there were no spatial differences in the stimulus-evoked activity within quadrants. Furthermore, the implemented stimulation protocol induced depression effects in the neuronal networks as demonstrated by the consistently lower network activity following stimulation sessions. Finally, the analysis demonstrated that the inhibitory effects of the stimulation decreased over time, thus suggesting a habituation phenomenon. These findings are sufficient to conclude that electrical stimulation is an important tool to interact with dissociated neuronal cultures, but localized stimuli are not enough to drive spatial synaptic potentiation or depression. On the contrary, the ability to modulate synaptic temporal plasticity was a feasible task to achieve by chronic network stimulation.

  2. Editor's highlight: Evaluation of a Microelectrode Array-based ...

    EPA Pesticide Factsheets

    Thousands of compounds in the environment have not been characterized for developmental neurotoxicity (DNT) hazard. To address this issue, methods to screen compounds rapidly for DNT hazard evaluation are necessary and are being developed for key neurodevelopmental processes. In order to develop an assay for network formation, the current study evaluated effects of a training set of chemicals on network ontogeny by measuring spontaneous electrical activity in neural networks grown on microelectrode arrays (MEA). Rat (0-24 h old) primary cortical cells were plated in 48 well MEA plates and exposed to six compounds: acetaminophen, bisindolylmaleimide-1 (Bis-1), domoic acid, mevastatin, sodium orthovanadate, and loperamide for a period of 12 days. Spontaneous network activity was recorded on days 2, 5, 7, 9, and 12 and viability was assessed using the Cell Titer Blue® assay on day 12. Network activity (e.g. mean firing rate (MFR), burst rate (BR), etc), increased between days 5 and 12. Random Forest analysis indicated that across all compounds and times, temporal correlation of firing patterns (r), MFR, BR, #of active electrodes and % of spikes in a burst were the most influential parameters in separating control from treated wells. All compounds except acetaminophen (≤ 30 µM) caused concentration-related effects on one or more of these parameters. Domoic acid and sodium orthovanadate altered several of these parameters in the absence of cytotoxicity. Although

  3. Electrophysiological characterization of Nsc-34 cell line using Microelectrode Array.

    PubMed

    Sabitha, K R; Sanjay, D; Savita, B; Raju, T R; Laxmi, T R

    2016-11-15

    Neurons communicate with each other through intricate network to evolve higher brain functions. The electrical activity of the neurons plays a crucial role in shaping the connectivity. With motor neurons being vulnerable to neurodegenerative diseases, understanding the electrophysiological properties of motor neurons is the need of the hour, in order to comprehend the impairment of connectivity in these diseases. NSC-34 cell line serves as an excellent model to study the properties of motor neurons as they express Choline acetyltransferase (ChAT). Although NSC-34 cell lines have been used to study the effect of various toxicological, neurotrophic and neuroprotective agents, the electrical activity of these cells has not been elucidated. In the current study, we have characterized the electrophysiological properties of NSC-34 cell lines using Micro-Electrode Array (MEA) as a tool. Based on the spike waveform, firing frequency, auto- and cross-correlogram analysis, we demonstrate that NSC-34 cell culture has >2 distinct types of neuronal population: principal excitatory neurons, putative interneurons and unclassified neurons. The presence of interneurons in the NSC-34 culture was characterized by increased expression of GAD-67 markers. Thus, finding an understanding of the electrophysiological properties of different population of neurons in NSC-34 cell line, will have multiple applications in the treatment of neurological disorders.

  4. Modelling small-patterned neuronal networks coupled to microelectrode arrays

    NASA Astrophysics Data System (ADS)

    Massobrio, Paolo; Martinoia, Sergio

    2008-09-01

    Cultured neurons coupled to planar substrates which exhibit 'well-defined' two-dimensional network architectures can provide valuable insights into cell-to-cell communication, network dynamics versus topology, and basic mechanisms of synaptic plasticity and learning. In the literature several approaches were presented to drive neuronal growth, such as surface modification by silane chemistry, photolithographic techniques, microcontact printing, microfluidic channel flow patterning, microdrop patterning, etc. This work presents a computational model fit for reproducing and explaining the dynamics exhibited by small-patterned neuronal networks coupled to microelectrode arrays (MEAs). The model is based on the concept of meta-neuron, i.e., a small spatially confined number of actual neurons which perform single macroscopic functions. Each meta-neuron is characterized by a detailed morphology, and the membrane channels are modelled by simple Hodgkin-Huxley and passive kinetics. The two main findings that emerge from the simulations can be summarized as follows: (i) the increasing complexity of meta-neuron morphology reflects the variations of the network dynamics as a function of network development; (ii) the dynamics displayed by the patterned neuronal networks considered can be explained by hypothesizing the presence of several short- and a few long-term distance interactions among small assemblies of neurons (i.e., meta-neurons).

  5. An active, flexible carbon nanotube microelectrode array for recording electrocorticograms

    NASA Astrophysics Data System (ADS)

    Chen, Yung-Chan; Hsu, Hui-Lin; Lee, Yu-Tao; Su, Huan-Chieh; Yen, Shiang-Jie; Chen, Chang-Hsiao; Hsu, Wei-Lun; Yew, Tri-Rung; Yeh, Shih-Rung; Yao, Da-Jeng; Chang, Yen-Chung; Chen, Hsin

    2011-06-01

    A variety of microelectrode arrays (MEAs) has been developed for monitoring intra-cortical neural activity at a high spatio-temporal resolution, opening a promising future for brain research and neural prostheses. However, most MEAs are based on metal electrodes on rigid substrates, and the intra-cortical implantation normally causes neural damage and immune responses that impede long-term recordings. This communication presents a flexible, carbon-nanotube MEA (CMEA) with integrated circuitry. The flexibility allows the electrodes to fit on the irregular surface of the brain to record electrocorticograms in a less invasive way. Carbon nanotubes (CNTs) further improve both the electrode impedance and the charge-transfer capacity by more than six times. Moreover, the CNTs are grown on the polyimide substrate directly to improve the adhesion to the substrate. With the integrated recording circuitry, the flexible CMEA is proved capable of recording the neural activity of crayfish in vitro, as well as the electrocorticogram of a rat cortex in vivo, with an improved signal-to-noise ratio. Therefore, the proposed CMEA can be employed as a less-invasive, biocompatible and reliable neuro-electronic interface for long-term usage.

  6. Alternative post-processing on a CMOS chip to fabricate a planar microelectrode array.

    PubMed

    López-Huerta, Francisco; Herrera-May, Agustín L; Estrada-López, Johan J; Zuñiga-Islas, Carlos; Cervantes-Sanchez, Blanca; Soto, Enrique; Soto-Cruz, Blanca S

    2011-01-01

    We present an alternative post-processing on a CMOS chip to release a planar microelectrode array (pMEA) integrated with its signal readout circuit, which can be used for monitoring the neuronal activity of vestibular ganglion neurons in newborn Wistar strain rats. This chip is fabricated through a 0.6 μm CMOS standard process and it has 12 pMEA through a 4 × 3 electrodes matrix. The alternative CMOS post-process includes the development of masks to protect the readout circuit and the power supply pads. A wet etching process eliminates the aluminum located on the surface of the p+ -type silicon. This silicon is used as transducer for recording the neuronal activity and as interface between the readout circuit and neurons. The readout circuit is composed of an amplifier and tunable bandpass filter, which is placed on a 0.015 mm2 silicon area. The tunable bandpass filter has a bandwidth of 98 kHz and a common mode rejection ratio (CMRR) of 87 dB. These characteristics of the readout circuit are appropriate for neuronal recording applications.

  7. Alternative Post-Processing on a CMOS Chip to Fabricate a Planar Microelectrode Array

    PubMed Central

    López-Huerta, Francisco; Herrera-May, Agustín L.; Estrada-López, Johan J.; Zuñiga-Islas, Carlos; Cervantes-Sanchez, Blanca; Soto, Enrique; Soto-Cruz, Blanca S.

    2011-01-01

    We present an alternative post-processing on a CMOS chip to release a planar microelectrode array (pMEA) integrated with its signal readout circuit, which can be used for monitoring the neuronal activity of vestibular ganglion neurons in newborn Wistar strain rats. This chip is fabricated through a 0.6 μm CMOS standard process and it has 12 pMEA through a 4 × 3 electrodes matrix. The alternative CMOS post-process includes the development of masks to protect the readout circuit and the power supply pads. A wet etching process eliminates the aluminum located on the surface of the p+-type silicon. This silicon is used as transducer for recording the neuronal activity and as interface between the readout circuit and neurons. The readout circuit is composed of an amplifier and tunable bandpass filter, which is placed on a 0.015 mm2 silicon area. The tunable bandpass filter has a bandwidth of 98 kHz and a common mode rejection ratio (CMRR) of 87 dB. These characteristics of the readout circuit are appropriate for neuronal recording applications. PMID:22346681

  8. A High Aspect Ratio Microelectrode Array for Mapping Neural Activity in-vitro

    PubMed Central

    Kibler, Andrew B.; Jamieson, Brian G.; Durand, Dominique M.

    2011-01-01

    A novel high-aspect-ratio penetrating microelectrode array was designed and fabricated for the purpose of recording neural activity. The array allows two dimensional recording of 64 sites in vitro with high aspect ratio penetrating electrodes. Traditional surface electrode arrays, although easy to fabricate, do not penetrate to the viable tissue such as central hippocampus slices and thus have a lower signal/noise ratio and lower selectivity than a penetrating array. In the unfolded hippocampus preparation, the CA1–CA3 pyramidal cell layer in the whole unfolded rodent hippocampus preparation is encased by the alveus on one side and the Schaffer tract on the other and requires penetrating electrodes for high signal to noise ratio recording. An array of 64 electrode spikes, each with a target height of 200 μm and diameter of 20μm, was fabricated in silicon on a transparent glass substrate. The impedance of the individual electrodes was measured to be approximately 1.5MΩ± 497kΩ. The signal to noise ratio was measured and found to be 19.4 ± 3 dB compared to 3.9 ± 0.8 dB S/N for signals obtained with voltage sensitive dye RH414. A mouse unfolded hippocampus preparation was bathed in solution containing 50 micro-molar 4-Amino Pyridine and a complex two dimensional wave of activity was recorded using the array. These results indicate that this novel penetrating electrode array is able to obtain data superior to that of voltage sensitive dye techniques for broad field two-dimensional neuronal activity recording. When used with the unfolded hippocampus preparation, the combination forms a uniquely capable tool for imaging hippocampal network activity in the entire hippocampus. PMID:22179041

  9. Quantification of zinc toxicity using neuronal networks on microelectrode arrays.

    PubMed

    Parviz, M; Gross, G W

    2007-05-01

    Murine neuronal networks, derived from embryonic frontal cortex (FC) tissue grown on microelectrode arrays, were used to investigate zinc toxicity at concentrations ranging from 20 to 2000 microM total zinc acetate added to the culture medium. Continual multi-channel recording of spontaneous action potential generation allowed a quantitative analysis of the temporal evolution of network spike activity generation at specific zinc acetate concentrations. Cultures responded with immediate concentration-dependent excitation lasting from 5 to 50 min and consisting of increased spiking and enhanced, coordinated bursting, followed by irreversible activity decay. The time to 50% and 90% activity loss was concentration dependent, highly reproducible, and formed linear functions in log-log plots. Above 100 microM total zinc acetate, the activity loss was associated with massive cell swelling, blebbing, and even vigorous neuronal cell lysing. Glia showed stress, but did not participate in the extensive cell swelling. Network activity loss generally preceded morphological changes. Cultures pretreated with the GABA(A) receptor antagonists bicuculline (40 microM) and picrotoxin (1mM) lacked the initial excitation phase. This suggests that zinc-induced excitation may be mediated by interfering with GABA inhibition. Partial network protection was achieved by stopping spontaneous activity with either tetrodotoxin (200 nM) or lidocaine (250 microM). However, recovery was not complete and slow deterioration of network activity continued over 6-h periods. Removal of zinc by early medium changes showed irreversible, catastrophic network failure to develop in a concentration-dependent time window between 50% and 90% activity loss.

  10. Fabrication and mechanical characterization of long and different penetrating length neural microelectrode arrays

    NASA Astrophysics Data System (ADS)

    Goncalves, S. B.; Peixoto, A. C.; Silva, A. F.; Correia, J. H.

    2015-05-01

    This paper presents a detailed description of the design, fabrication and mechanical characterization of 3D microelectrode arrays (MEA) that comprise high aspect-ratio shafts and different penetrating lengths of electrodes (from 3 mm to 4 mm). The array’s design relies only on a bulk silicon substrate dicing saw technology. The encapsulation process is accomplished by a medical epoxy resin and platinum is used as the transduction layer between the probe and neural tissue. The probe’s mechanical behaviour can significantly affect the neural tissue during implantation time. Thus, we measured the MEA maximum insertion force in an agar gel phantom and a porcine cadaver brain. Successful 3D MEA were produced with shafts of 3 mm, 3.5 mm and 4 mm in length. At a speed of 180 mm min-1, the MEA show maximum penetrating forces per electrode of 2.65 mN and 12.5 mN for agar and brain tissue, respectively. A simple and reproducible fabrication method was demonstrated, capable of producing longer penetrating shafts than previously reported arrays using the same fabrication technology. Furthermore, shafts with sharp tips were achieved in the fabrication process simply by using a V-shaped blade.

  11. Microelectrode Arrays with Overlapped Diffusion Layers as Electroanalytical Detectors: Theory and Basic Applications

    PubMed Central

    Tomčík, Peter

    2013-01-01

    This contribution contains a survey of basic literature dealing with arrays of microelectrodes with overlapping diffusion layers as prospective tools in contemporary electrochemistry. Photolithographic thin layer technology allows the fabrication of sensors of micrometric dimensions separated with a very small gap. This fact allows the diffusion layers of single microelectrodes to overlap as members of the array. Various basic types of microelectrode arrays with interacting diffusion layers are described and their analytical abilities are accented. Theoretical approaches to diffusion layer overlapping and the consequences of close constitution effects such as collection efficiency and redox cycling are discussed. Examples of basis applications in electroanalytical chemistry such as amperometric detectors in HPLC and substitutional stripping voltammetry are also given. PMID:24152927

  12. A PARYLENE-BASED MICROELECTRODE ARRAY IMPLANT FOR SPINAL CORD STIMULATION IN RATS

    PubMed Central

    Nandra, Mandheerej. S.; Lavrov, Igor A.; Edgerton, V. Reggie; Tai, Yu-Chong

    2011-01-01

    The design and fabrication of an epidural spinal cord implant using a parylene-based microelectrode array is presented. Rats with hindlimb paralysis from a complete spinal cord transection were implanted with the device and studied for up to eight weeks, where we have demonstrated recovery of hindlimb stepping functionality through pulsed stimulation. The microelectrode array allows for a high degree of freedom and specificity in selecting the site of stimulation compared to wire-based implants, and triggers varied biological responses that can lead to an increased understanding of the spinal cord and locomotion recovery for victims of spinal cord injury. PMID:21841938

  13. A PARYLENE-BASED MICROELECTRODE ARRAY IMPLANT FOR SPINAL CORD STIMULATION IN RATS.

    PubMed

    Nandra, Mandheerej S; Lavrov, Igor A; Edgerton, V Reggie; Tai, Yu-Chong

    2011-01-23

    The design and fabrication of an epidural spinal cord implant using a parylene-based microelectrode array is presented. Rats with hindlimb paralysis from a complete spinal cord transection were implanted with the device and studied for up to eight weeks, where we have demonstrated recovery of hindlimb stepping functionality through pulsed stimulation. The microelectrode array allows for a high degree of freedom and specificity in selecting the site of stimulation compared to wire-based implants, and triggers varied biological responses that can lead to an increased understanding of the spinal cord and locomotion recovery for victims of spinal cord injury.

  14. Spirally oriented Au microelectrode array sensor for detection of Hg (II).

    PubMed

    Huan, Tran Ngoc; Hung, Le Quoc; Ha, Vu Thi Thu; Anh, Nguyen Hoang; Van Khai, Tran; Shim, Kwang Bo; Chung, Hoeil

    2012-05-30

    A simple and reproducible carbon microelectrode array (CMA), designed to eliminate diffusive interference among the microelectrodes, has been fabricated and used as a frame to build a gold (Au) microelectrode array (GMA) sensor. To prepare the CMA initially, rather than use an uncontrollable large number of carbon fibers, only 60 carbon fibers of regular size were used to ensure manageable and reproducible arrangement for array construction. In addition, for efficient spatial arrangement of the microelectrode and easy sensor preparation, carbon fibers were oriented in a spiral fashion by rolling around a Cu wire. The distance between carbon fibers was carefully determined to avoid overlap among individual diffusion layers, one of the important factors governing steady-state current response and sensor-to-sensor reproducibility. After the preparation of a spirally arranged CMA, Au was electrochemically deposited on the surface of individual carbon electrodes to build a final GMA sensor. Then, the GMA sensor was used to measure Hg(2+) in a low concentration range. Simultaneously, multiple GMA sensors were independently prepared to examine reproducibility in sensor fabrication as well as electrochemical measurement (sensor-to-sensor reproducibility). Overall, highly sensitive detection of Hg(2+) was possible using the proposed GMA sensor due to efficient arrangement of microelectrodes and the sensor-to-sensor reproducibility was superior owing to simplicity in sensor fabrication.

  15. Nanostructuration strategies to enhance microelectrode array (MEA) performance for neuronal recording and stimulation.

    PubMed

    Heim, Matthias; Yvert, Blaise; Kuhn, Alexander

    2012-01-01

    Microelectrode arrays (MEAs) are widely used tools for recording and stimulating extracellular neuronal activity. Major limitations when decreasing electrode size in dense arrays are increased noise level and low charge injection capability. Nanostructuration of the electrode sites on MEAs presents an efficient way to overcome these problems by decreasing the impedance of the electrode/solution interface. Here, we review different techniques used to achieve this goal including template assisted electrodeposition for generating macro- and mesoporous films, immobilization of carbon nanotubes (CNTs) and deposition of conducting polymers onto microelectrodes. When tested during in vitro and in vivo measurements, nanostructured MEAs display improved sensitivity during recording of neuronal activity together with a higher efficiency in the stimulation process compared to conventional microelectrodes.

  16. Monitoring Hippocampus Electrical Activity In Vitro on an Elastically Deformable Microelectrode Array

    PubMed Central

    Yu, Zhe; Graudejus, Oliver; Tsay, Candice; Lacour, Stéphanie P.; Wagner, Sigurd

    2009-01-01

    Abstract Interfacing electronics and recording electrophysiological activity in mechanically active biological tissues is challenging. This challenge extends to recording neural function of brain tissue in the setting of traumatic brain injury (TBI), which is caused by rapid (within hundreds of milliseconds) and large (greater than 5% strain) brain deformation. Interfacing electrodes must be biocompatible on multiple levels and should deform with the tissue to prevent additional mechanical damage. We describe an elastically stretchable microelectrode array (SMEA) that is capable of undergoing large, biaxial, 2-D stretch while remaining functional. The new SMEA consists of elastically stretchable thin metal films on a silicone membrane. It can stimulate and detect electrical activity from cultured brain tissue (hippocampal slices), before, during, and after large biaxial deformation. We have incorporated the SMEA into a well-characterized in vitro TBI research platform, which reproduces the biomechanics of TBI by stretching the SMEA and the adherent brain slice culture. Mechanical injury parameters, such as strain and strain rate, can be precisely controlled to generate specific levels of damage. The SMEA allowed for quantification of neuronal function both before and after injury, without breaking culture sterility or repositioning the electrodes for the injury event, thus enabling serial and long-term measurements. We report tests of the SMEA and an initial application to study the effect of mechanical stimuli on neuron function, which could be employed as a high-content, drug-screening platform for TBI. PMID:19594385

  17. Characterization of Early Cortical Neural Network Development in Multiwell Microelectrode Array Plates

    EPA Science Inventory

    We examined the development of neural network activity using microelectrode array (MEA) recordings made in multi-well MEA plates (mwMEAs) over the first 12 days in vitro (DIV). In primary cortical cultures made from postnatal rats, action potential spiking activity was essentiall...

  18. Effects of Organophosphorus Flame Retardants on Spontaneous Activity in Neuronal Networks Grown on Microelectrode Arrays

    EPA Science Inventory

    EFFECTS OF ORGANOPHOSPHORUS FLAME RETARDANTS ON SPONTANEOUS ACTIVITY IN NEURONAL NETWORKS GROWN ON MICROELECTRODE ARRAYS TJ Shafer1, K Wallace1, WR Mundy1, M Behl2,. 1Integrated Systems Toxicology Division, NHEERL, USEPA, RTP, NC, USA, 2National Toxicology Program, NIEHS, RTP, NC...

  19. Development of a Microelectrode Array Sensing Platform for Combination Electrochemical and Spectrochemical Aqueous Ion Testing

    PubMed Central

    Gardner, Robert D.; Zhou, Anhong; Zufelt, Nephi A.

    2009-01-01

    A microelectrode array sensor platform was designed and fabricated to increase diversity, flexibility, and versatility of testing capabilities over that of traditionally reported sensor platforms. These new sensor platforms consist of 18 individual addressable microelectrodes, photolithography fabricated, that employ a glass base substrate and a resist polymer layer that acts as an insulating agent to protect the circuitry and wiring of the sensor from undesired solution interactions. Individually addressable microelectrodes increase diversity by allowing isolated electrochemical testing between electrodes, global array testing, or some combination of electrodes to perform electrochemical methods. Furthermore, because of the optical transparency of the glass base substrate and the resist mask layer, along with the small size of the electrode array, spectrochemical analysis is possible within the sample area that acts as electrochemical cell and cuvette, while the microelectrode array passively resides within the optical path length during spectrochemical testing. This unique arrangement offers improved testing possibilities for various applications, including simultaneous electrochemical and spectrochemical analysis in environmental testing, identification or quantification of possible species for bioavailability in the biotechnology field, and process control in industrial applications. Electrochemical characteristics and spectrochemcial use of the sensor platform are proven with potassium ferricyanide, an electrochemical standard analyte, and electrochemical measurements are compared against a commercially available working electrode of similar size. Additionally, the electrochemical method of differential pulse anodic stripping voltammetry is performed with the sensor platform to detect copper and lead heavy metal ions in aqueous solution, demonstrating the potential for use with environmental samples. PMID:20130752

  20. Microelectrode arrays: a general strategy for using oxidation reactions to site selectively modify electrode surfaces.

    PubMed

    Nguyen, Bichlien H; Kesselring, David; Tesfu, Eden; Moeller, Kevin D

    2014-03-04

    Oxidation reactions are powerful tools for synthesis because they allow for the functionalization of molecules. Here, we present a general method for conducting these reactions on a microelectrode array in a site-selective fashion. The reactions are run as a competition between generation of a chemical oxidant at the electrodes in the array and reduction of the oxidant by a "confining agent" in the solution above the array. The "confining agent" does not need to be more reactive than the substrate fixed to the surface of the array. In many cases, the same substrate placed on the surface of the array can also be used in solution as the confining agent.

  1. Low cost silicon solar arrays

    NASA Technical Reports Server (NTRS)

    Goldsmith, J. V.; Cleland, J. W.; Westbrook, R. D.; Davis, H. L.; Wood, R. F.; Lindmayer, J.; Wakefield, G. F.

    1975-01-01

    The economic production of silicon solar cell arrays circumvents p-n junction degradation by nuclear doping, in which the Si-30 transmutes to P-31 after thermal neutron capture. Also considered are chemical purity specifications for improved silicon bulk states, surface induced states, and surface states.

  2. Silicon Heat Pipe Array

    NASA Technical Reports Server (NTRS)

    Yee, Karl Y.; Ganapathi, Gani B.; Sunada, Eric T.; Bae, Youngsam; Miller, Jennifer R.; Beinsford, Daniel F.

    2013-01-01

    Improved methods of heat dissipation are required for modern, high-power density electronic systems. As increased functionality is progressively compacted into decreasing volumes, this need will be exacerbated. High-performance chip power is predicted to increase monotonically and rapidly with time. Systems utilizing these chips are currently reliant upon decades of old cooling technology. Heat pipes offer a solution to this problem. Heat pipes are passive, self-contained, two-phase heat dissipation devices. Heat conducted into the device through a wick structure converts the working fluid into a vapor, which then releases the heat via condensation after being transported away from the heat source. Heat pipes have high thermal conductivities, are inexpensive, and have been utilized in previous space missions. However, the cylindrical geometry of commercial heat pipes is a poor fit to the planar geometries of microelectronic assemblies, the copper that commercial heat pipes are typically constructed of is a poor CTE (coefficient of thermal expansion) match to the semiconductor die utilized in these assemblies, and the functionality and reliability of heat pipes in general is strongly dependent on the orientation of the assembly with respect to the gravity vector. What is needed is a planar, semiconductor-based heat pipe array that can be used for cooling of generic MCM (multichip module) assemblies that can also function in all orientations. Such a structure would not only have applications in the cooling of space electronics, but would have commercial applications as well (e.g. cooling of microprocessors and high-power laser diodes). This technology is an improvement over existing heat pipe designs due to the finer porosity of the wick, which enhances capillary pumping pressure, resulting in greater effective thermal conductivity and performance in any orientation with respect to the gravity vector. In addition, it is constructed of silicon, and thus is better

  3. Scanning electron microscopy of chronically implanted intracortical microelectrode arrays in non-human primates

    PubMed Central

    Barrese, James C; Aceros, Juan; Donoghue, John P

    2016-01-01

    Objective Signal attenuation is a major problem facing intracortical sensors for chronic neuroprosthetic applications. Many studies suggest that failure is due to gliosis around the electrode tips, however, mechanical and material causes of failure are often overlooked. The purpose of this study was to investigate the factors contributing to progressive signal decline by using scanning electron microscopy (SEM) to visualize structural changes in chronically implanted arrays and histology to examine the tissue response at corresponding implant sites. Approach We examined eight chronically implanted intracortical microelectrode arrays (MEAs) explanted from non-human primates at times ranging from 37 to 1051 days post-implant. We used SEM, in vivo neural recordings, and histology (GFAP, Iba-1, NeuN). Three MEAs that were never implanted were also imaged as controls. Main results SEM revealed progressive corrosion of the platinum electrode tips and changes to the underlying silicon. The parylene insulation was prone to cracking and delamination, and in some instances the silicone elastomer also delaminated from the edges of the MEA. Substantial tissue encapsulation was observed and was often seen growing into defects in the platinum and parylene. These material defects became more common as the time in vivo increased. Histology at 37 and 1051 days post-implant showed gliosis, disruption of normal cortical architecture with minimal neuronal loss, and high Iba-1 reactivity, especially within the arachnoid and dura. Electrode tracts were either absent or barely visible in the cortex at 1051 days, but were seen in the fibrotic encapsulation material suggesting that the MEAs were lifted out of the brain. Neural recordings showed a progressive drop in impedance, signal amplitude, and viable channels over time. Significance These results provide evidence that signal loss in MEAs is truly multifactorial. Gliosis occurs in the first few months after implantation but does not

  4. Scanning electron microscopy of chronically implanted intracortical microelectrode arrays in non-human primates

    NASA Astrophysics Data System (ADS)

    Barrese, James C.; Aceros, Juan; Donoghue, John P.

    2016-04-01

    Objective. Signal attenuation is a major problem facing intracortical sensors for chronic neuroprosthetic applications. Many studies suggest that failure is due to gliosis around the electrode tips, however, mechanical and material causes of failure are often overlooked. The purpose of this study was to investigate the factors contributing to progressive signal decline by using scanning electron microscopy (SEM) to visualize structural changes in chronically implanted arrays and histology to examine the tissue response at corresponding implant sites. Approach. We examined eight chronically implanted intracortical microelectrode arrays (MEAs) explanted from non-human primates at times ranging from 37 to 1051 days post-implant. We used SEM, in vivo neural recordings, and histology (GFAP, Iba-1, NeuN). Three MEAs that were never implanted were also imaged as controls. Main results. SEM revealed progressive corrosion of the platinum electrode tips and changes to the underlying silicon. The parylene insulation was prone to cracking and delamination, and in some instances the silicone elastomer also delaminated from the edges of the MEA. Substantial tissue encapsulation was observed and was often seen growing into defects in the platinum and parylene. These material defects became more common as the time in vivo increased. Histology at 37 and 1051 days post-implant showed gliosis, disruption of normal cortical architecture with minimal neuronal loss, and high Iba-1 reactivity, especially within the arachnoid and dura. Electrode tracts were either absent or barely visible in the cortex at 1051 days, but were seen in the fibrotic encapsulation material suggesting that the MEAs were lifted out of the brain. Neural recordings showed a progressive drop in impedance, signal amplitude, and viable channels over time. Significance. These results provide evidence that signal loss in MEAs is truly multifactorial. Gliosis occurs in the first few months after implantation but does

  5. Flexible complementary metal oxide semiconductor microelectrode arrays with applications in single cell characterization

    NASA Astrophysics Data System (ADS)

    Pajouhi, H.; Jou, A. Y.; Jain, R.; Ziabari, A.; Shakouri, A.; Savran, C. A.; Mohammadi, S.

    2015-11-01

    A highly flexible microelectrode array with an embedded complementary metal oxide semiconductor (CMOS) instrumentation amplifier suitable for sensing surfaces of biological entities is developed. The array is based on ultrathin CMOS islands that are thermally isolated from each other and are interconnected by meandered nano-scale wires that can adapt to cellular surfaces with micro-scale curvatures. CMOS temperature sensors are placed in the islands and are optimally biased to have high temperature sensitivity. While no live cell thermometry is conducted, a measured temperature sensitivity of 0.15 °C in the temperature range of 35 to 40 °C is achieved by utilizing a low noise CMOS lock-in amplifier implemented in the same technology. The monolithic nature of CMOS sensors and amplifier circuits and their versatile flexible interconnecting wires overcome the sensitivity and yield limitations of microelectrode arrays fabricated in competing technologies.

  6. Design, Fabrication, Simulation and Characterization of a Novel Dual-Sided Microelectrode Array for Deep Brain Recording and Stimulation.

    PubMed

    Zhao, Zongya; Gong, Ruxue; Huang, Hongen; Wang, Jue

    2016-06-15

    In this paper, a novel dual-sided microelectrode array is specially designed and fabricated for a rat Parkinson's disease (PD) model to study the mechanisms of deep brain stimulation (DBS). The fabricated microelectrode array can stimulate the subthalamic nucleus and simultaneously record electrophysiological information from multiple nuclei of the basal ganglia system. The fabricated microelectrode array has a long shaft of 9 mm and each planar surface is equipped with three stimulating sites (diameter of 100 μm), seven electrophysiological recording sites (diameter of 20 μm) and four sites with diameter of 50 μm used for neurotransmitter measurements in future work. The performances of the fabricated microelectrode array were characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. In addition, the stimulating effects of the fabricated microelectrode were evaluated by finite element modeling (FEM). Preliminary animal experiments demonstrated that the designed microelectrode arrays can record spontaneous discharge signals from the striatum, the subthalamic nucleus and the globus pallidus interna. The designed and fabricated microelectrode arrays provide a powerful research tool for studying the mechanisms of DBS in rat PD models.

  7. Design, Fabrication, Simulation and Characterization of a Novel Dual-Sided Microelectrode Array for Deep Brain Recording and Stimulation

    PubMed Central

    Zhao, Zongya; Gong, Ruxue; Huang, Hongen; Wang, Jue

    2016-01-01

    In this paper, a novel dual-sided microelectrode array is specially designed and fabricated for a rat Parkinson’s disease (PD) model to study the mechanisms of deep brain stimulation (DBS). The fabricated microelectrode array can stimulate the subthalamic nucleus and simultaneously record electrophysiological information from multiple nuclei of the basal ganglia system. The fabricated microelectrode array has a long shaft of 9 mm and each planar surface is equipped with three stimulating sites (diameter of 100 μm), seven electrophysiological recording sites (diameter of 20 μm) and four sites with diameter of 50 μm used for neurotransmitter measurements in future work. The performances of the fabricated microelectrode array were characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS) and cyclic voltammetry. In addition, the stimulating effects of the fabricated microelectrode were evaluated by finite element modeling (FEM). Preliminary animal experiments demonstrated that the designed microelectrode arrays can record spontaneous discharge signals from the striatum, the subthalamic nucleus and the globus pallidus interna. The designed and fabricated microelectrode arrays provide a powerful research tool for studying the mechanisms of DBS in rat PD models. PMID:27314356

  8. Characterization of surface modification on microelectrode arrays for in vitro cell culture.

    PubMed

    Lin, Shu-Ping; Chen, Jia-Jin J; Liao, Jiunn-Der; Tzeng, Shun-Fen

    2008-02-01

    This study aims to investigate surface-modified microelectrodes on the microelectrode arrays (MEAs) for neuronal interfaces with in vitro cell culture. The polyimide (PI) MEA was fabricated by using micro-electro-mechanical systems (MEMS) techniques. Self-assembled monolayers (SAMs) of 11-mercaptoundecanoic acid (MUA) were utilized to modify the microelectrode surface of the MEA. The SAMs' modified surface of microelectrodes offered a reliable interface to immobilize biological ligands through covalent bonding. To increase biocompatibility, the poly-D-lysine (PDL) was immobilized on the SAMs' modified microelectrodes. Several analytical techniques were used to define the physical structure and functional groups of surface-modified gold microelectrodes on the MEA. Spectra of the Fourier transform infrared reflection (FTIR) were applied to characterize the molecular structure of MUA-SAMs and PDL on the microelectrodes. The spectra, two peaks of amide I (at 1,613 cm(-1)) and amide II (at 1,548 cm(-1)), revealed that covalent amide bonding existed in PDL-MUA-SAMs modified surfaces. The thickness and formation of the MUA and PDL were also observed and quantified by using an atomic force microscope (AFM). The impedance measurement of PDL-MUA-SAMs modified MEA only increased slightly to an average of 524.6 +/- 55.8 kOmega from 352.9 +/- 34.4 kOmega of bare gold microelectrode (p < 0.05, N = 20). In addition, the time-course changes of total impedance resulting from cell sealing resistance and gap reactance were recorded for 7 days for inferring the growth of cell lines on the electrode contact of modified MEA. The experiment of 3T3 fibroblasts, PC12 cells, primary glial cells, and primary cortical neurons cultured on the modified MEAs displayed a good adhesion rate. These biocompatibility assays demonstrated that the neuronal cells are able to grow in a proximity to PDL-MUA-SAMs modified microelectrodes of the MEAs for effective electrophysiological stimulation

  9. A novel AC electrothermal micropump for biofluid transport using circular interdigitated microelectrode array

    NASA Astrophysics Data System (ADS)

    Salari, Alinaghi; Dalton, Colin

    2015-03-01

    Electrokinetic micropumps have been widely used in lab-on-a-chip devices. The AC electrothermal (ACET) effect is highly efficient for biofluidic micropumping, but is unable to generate high flow rates. Attempts to increase ACET flows, such as applying a wide range of actuation voltages, using asymmetric microelectrode arrays and using 3D microelectrodes have been reported. In this paper a novel idea of employing circular coplanar asymmetric microelectrodes placed on the perimeter of a microchannel is explored. An array of microelectrodes is simulated using COMSOL Multiphysics software. The micropump output shows relatively high flow rates compared to other ACET micropumps which have the same electrode dimensions. Moreover, the idea of using different micropumps with scaled dimensions is investigated. The results show that a highly efficient ACET micropump can be achieved if an appropriate electrode size-to-channel dimension ratio is selected. The results also show that a micropump with a scale of 0.2 can show negligible flow rate, but if the electrodes are used in a micropump with the scale of 1, a flow rate of 15 ×106 μm3/s can be generated. This new ACET pump design can be utilized for lab-on-a-chip applications, specifically in biofluid delivery systems.

  10. A nanoporous alumina microelectrode array for functional cell-chip coupling

    NASA Astrophysics Data System (ADS)

    Wesche, Manuel; Hüske, Martin; Yakushenko, Alexey; Brüggemann, Dorothea; Mayer, Dirk; Offenhäusser, Andreas; Wolfrum, Bernhard

    2012-12-01

    The design of electrode interfaces has a strong impact on cell-based bioelectronic applications. We present a new type of microelectrode array chip featuring a nanoporous alumina interface. The chip is fabricated in a combination of top-down and bottom-up processes using state-of-the-art clean room technology and self-assembled generation of nanopores by aluminum anodization. The electrode characteristics are investigated in phosphate buffered saline as well as under cell culture conditions. We show that the modified microelectrodes exhibit decreased impedance compared to planar microelectrodes, which is caused by a nanostructuring effect of the underlying gold during anodization. The stability and biocompatibility of the device are demonstrated by measuring action potentials from cardiomyocyte-like cells growing on top of the chip. Cross sections of the cell-surface interface reveal that the cell membrane seals the nanoporous alumina layer without bending into the sub-50 nm apertures. The nanoporous microelectrode array device may be used as a platform for combining extracellular recording of cell activity with stimulating topographical cues.

  11. Robust Functionalization of Large Microelectrode Arrays by Using Pulsed Potentiostatic Deposition

    PubMed Central

    Rothe, Joerg; Frey, Olivier; Madangopal, Rajtarun; Rickus, Jenna; Hierlemann, Andreas

    2016-01-01

    Surface modification of microelectrodes is a central step in the development of microsensors and microsensor arrays. Here, we present an electrodeposition scheme based on voltage pulses. Key features of this method are uniformity in the deposited electrode coatings, flexibility in the overall deposition area, i.e., the sizes and number of the electrodes to be coated, and precise control of the surface texture. Deposition and characterization of four different materials are demonstrated, including layers of high-surface-area platinum, gold, conducting polymer poly(ethylenedioxythiophene), also known as PEDOT, and the non-conducting polymer poly(phenylenediamine), also known as PPD. The depositions were conducted using a fully integrated complementary metal-oxide-semiconductor (CMOS) chip with an array of 1024 microelectrodes. The pulsed potentiostatic deposition scheme is particularly suitable for functionalization of individual electrodes or electrode subsets of large integrated microelectrode arrays: the required deposition waveforms are readily available in an integrated system, the same deposition parameters can be used to functionalize the surface of either single electrodes or large arrays of thousands of electrodes, and the deposition method proved to be robust and reproducible for all materials tested. PMID:28025569

  12. Toward a comparison of microelectrodes for acute and chronic recordings.

    PubMed

    Ward, Matthew P; Rajdev, Pooja; Ellison, Casey; Irazoqui, Pedro P

    2009-07-28

    Several variations of microelectrode arrays are used to record and stimulate intracortical neuronal activity. Bypassing the immune response to maintain a stable recording interface remains a challenge. Companies and researchers are continuously altering the material compositions and geometries of the arrays in order to discover a combination that allows for a chronic and stable electrode-tissue interface. From this interface, they wish to obtain consistent quality recordings and a stable, low impedance pathway for charge injection over extended periods of time. Despite numerous efforts, no microelectrode array design has managed to evade the host immune response and remain fully functional. This study is an initial effort comparing several microelectrode arrays with fundamentally different configurations for use in an implantable epilepsy prosthesis. Specifically, NeuroNexus (Michigan) probes, Cyberkinetics (Utah) Silicon and Iridium Oxide arrays, ceramic-based thin-film microelectrode arrays (Drexel), and Tucker-Davis Technologies (TDT) microwire arrays are evaluated over a 31-day period in an animal model. Microelectrodes are compared in implanted rats through impedance, charge capacity, signal-to-noise ratio, recording stability, and elicited immune response. Results suggest significant variability within and between microelectrode types with no clear superior array. Some applications for the microelectrode arrays are suggested based on data collected throughout the longitudinal study. Additionally, specific limitations of assaying biological phenomena and comparing fundamentally different microelectrode arrays in a highly variable system are discussed with suggestions on how to improve the reliability of observed results and steps needed to develop a more standardized microelectrode design.

  13. Indirect voltammetric detection of fluoride ions in toothpaste on a comb-shaped interdigitated microelectrode array.

    PubMed

    Cernanská, Monika; Tomcík, Peter; Jánosíková, Zuzana; Rievaj, Miroslav; Bustin, Dusan

    2011-02-15

    A novel technique based on dynamic electrochemistry for the detection of fluoride ions was developed. It is based on its strong complexation with ferric ion. Formed fluoroferric complex is cathodically inactive at the potential of the reduction of free ferric aquo ion. The voltammetric and amperometric response of platinum comb-shaped interdigitated microelectrode array is decreased after fluoride addition. This decrease serves for the quantification of fluoride ions added to the solution. The detection limit of 4.5×10(-5) mol dm(-3) was achieved when one of the segments of interdigitated microelectrode array (IDA) was used as an indicating electrode. The detection limit is about one order of magnitude lower than in the case of conventional platinum macroelectrode. In comparison with ISE electrodes this method is faster and also avoiding large error resulting from the antilogarithmization of ISE Nerstian response. The method was applied to the analysis of toothpaste.

  14. Hygroscopic particle behavior studied by interdigitated array microelectrode impedance sensors.

    PubMed

    Schindelholz, Eric; Tsui, Lok-kun; Kelly, Robert G

    2014-01-09

    The hygroscopic behavior of soluble salts bears importance in many research fields including atmospheric sciences, corrosion, porous building materials, and pharmaceuticals. Several methods have been used to study deliquescence (solid to liquid) and efflorescence (liquid to solid) phase transitions of these salts. In this study, we measured the deliquescence and efflorescence RH values of single salt microparticles deposited on an interdigitated microelectrode sensor via electrical impedance. The salts examined were NaCl, LiCl, NaBr, KCl, and MgCl2. Measured values were in agreement with in situ optical microscopic observations and, with the exception of MgCl2, literature values. In the case of MgCl2, deliquescence occurred at 33% RH and 12-15% RH, with the latter range being previously unreported. The depressed deliquescence RH was hypothesized to be a result of the formation of a metastable MgCl2 hydrate. Incomplete efflorescence of MgCl2 was also observed after exposure to <1.5% RH for up to 22 h due to formation of solid shells which trapped fluid. The phenomena elucidated by these results provide an explanation for the anomalous water retention and uptake behavior of MgCl2 below 33% RH reported elsewhere in the literature. The results presented in this study validate the use of this method as an alternative or complementary method for study of bulk-phase transitions of substrate-deposited particles across a broad RH range. These findings also demonstrate the utility of this method for detection of fluid trapping which cannot be directly ascertained by gravimetric and line-of-sight techniques commonly used in the study of hygroscopic particles.

  15. Selective Stimulation and Measurement in the Cochlear Nucleus With the Spike Microelectrode Array

    DTIC Science & Technology

    2007-11-02

    Selective Stimulation and Measurement in the Cochlear Nucleus with the Spike Microelectrode Array F. MASE1, H. TAKAHASHI1, T. EJIRI1, M. NAKAO1, N...aren’t always effective, because we don’t have sufficient knowledge of the auditory pathways and the Cochlear Nucleus (CN) functions to stimulate the... Cochlear Nucleus functionally. Our goals are to enhance our understanding of such functions and to develop effective stimulating strategies of the CN

  16. An electrochemical immunosensor based on interdigitated array microelectrode for the detection of chlorpyrifos.

    PubMed

    Cao, Yaoyao; Sun, Xia; Guo, Yemin; Zhao, Wenping; Wang, Xiangyou

    2015-02-01

    An electrochemical immunosensor based on interdigitated array microelectrodes (IDAMs) was developed for sensitive, specific and rapid detection of chlorpyrifos. Anti-chlorpyrifos monoclonal antibodies were orientedly immobilized onto the gold microelectrode surface through protein A. Chlorpyrifos were then captured by the immobilized antibody, resulting in an impedance change in the IDAMs surface. Electrochemical impedance spectroscopy was used in conjunction with the fabricated sensor to detect chlorpyrifos. Under optimum conditions, the impedance value change of chlorpyrifos was proportional to its concentrations in the range of 10(0)-10(5) ng/mL. The detection limit was found to be 0.014 ng/mL for chlorpyrifos. The proposed chlorpyrifos immunosensor could be used as a screening method in pesticide determination for the analysis of environmental, agricultural and pharmaceutical samples due to its rapidity, sensitivity and low cost.

  17. Rigid spine reinforced polymer microelectrode array probe and method of fabrication

    DOEpatents

    Tabada, Phillipe; Pannu, Satinderpall S

    2014-05-27

    A rigid spine-reinforced microelectrode array probe and fabrication method. The probe includes a flexible elongated probe body with conductive lines enclosed within a polymeric material. The conductive lines connect microelectrodes found near an insertion end of the probe to respective leads at a connector end of the probe. The probe also includes a rigid spine, such as made from titanium, fixedly attached to the probe body to structurally reinforce the probe body and enable the typically flexible probe body to penetrate and be inserted into tissue, such as neural tissue. By attaching or otherwise fabricating the rigid spine to connect to only an insertion section of the probe body, an integrally connected cable section of the probe body may remain flexible.

  18. Electrical impedance characterization of cell growth on interdigitated microelectrode array.

    PubMed

    Lee, Gi Hyun; Pyun, Jae-Chul; Cho, Sungbo

    2014-11-01

    Electrical cell-substrate impedance sensing is a method for label-free and real-time monitoring of biological cells, which has been increasingly employed in the diagnostic and pharmaceutical industries. In this study, we fabricated an interdigitated electrode (IDE) array, which consists of 10 fingers, with a length of 1.2 mm, width of 50 μm, spacing of 50 μm, and thickness of 75 nm. The impedance spectra of the fabricated IDE were measured without or with cells in the frequency range of 100 Hz to 100 kHz using a lock-in amplifier based system and characterized by equivalent circuit modelling. Regarding the total impedance as a series resistance (R) and capacitance (C) model, R and C parameters were traced at a selected frequency during cell growth. It was able to monitor cell adherence and proliferation dependent on the behaviours and characteristics of cells on the fabricated IDE array by monitoring RC parameters. The degree of changes in RC value during cell growth was dependent on the type of cells used.

  19. Accurate resistivity mouse brain mapping using microelectrode arrays.

    PubMed

    Béduer, Amélie; Joris, Pierre; Mosser, Sébastien; Delattre, Vincent; Fraering, Patrick C; Renaud, Philippe

    2014-10-15

    Electrical impedance spectroscopy measurements were performed in post-mortem mice brains using a flexible probe with an embedded micrometric electrode array. Combined with a peak resistance frequency method this allowed obtaining intrinsic resistivity values of brain tissues and structures with submillimetric resolution. Reproducible resistivity measurements are reported, which allows the resistivity in the cortex, ventricle, fiber tracts, thalamus and basal ganglia to be differentiated. Measurements of brain slices revealed resistivity profiles correlated with the local density of cell bodies hence allowing to discriminate between the different cortical layers. Finally, impedance measurements were performed on a model of cauterized mouse brain evidencing the possibility to measure the spatial extent and the degree of the tissue denaturation due to the cauterization.

  20. Rapid odor perception in rat olfactory bulb by microelectrode array*

    PubMed Central

    Zhou, Jun; Dong, Qi; Zhuang, Liu-jing; Li, Rong; Wang, Ping

    2012-01-01

    Responses of 302 mitral/tufted (M/T) cells in the olfactory bulb were recorded from 42 anesthetized freely breathing rats using a 16-channel microwire electrode array. Saturated vapors of four pure chemicals, anisole, carvone, citral and isoamyl acetate were applied. After aligning spike trains to the initial phase of the inhalation after odor onset, the responses of M/T cells showed transient temporal features including excitatory and inhibitory patterns. Both odor-evoked patterns indicated that mammals recognize odors within a short respiration cycle after odor stimulus. Due to the small amount of information received from a single cell, we pooled results from all responsive M/T cells to study the ensemble activity. The firing rates of the cell ensembles were computed over 100 ms bins and population vectors were constructed. The high dimension vectors were condensed into three dimensions for visualization using principal component analysis. The trajectories of both excitatory and inhibitory cell ensembles displayed strong dynamics during odor stimulation. The distances among cluster centers were enlarged compared to those of the resting state. Thus, we presumed that pictures of odor information sent to higher brain regions were depicted and odor discrimination was completed within the first breathing cycle. PMID:23225857

  1. Synchronization of neurons in micro-electrode array cultures

    NASA Astrophysics Data System (ADS)

    Esposti, F.; Signorini, M. G.

    2008-12-01

    A lot of methods were created in last decade for the spatio-temporal analysis of multi-electrode array (MEA) neuronal data sets. In this paper we show how a new simple analysis approach that considers the total network activity, is able to show interesting neuronal network system dynamical features. In particular, we perform two different analyses: a neuronal connectivity examination studying networks at different days in vitro (div) and an analysis of the long per- iod effects of the administration of two common neuroactive drugs, Tetrodotoxin (TTX) and D-2-amino-5-phosphonovalerate (AP5), to spontaneously spiking mature neuronal networks. Our analysis is performed considering burst topology, i.e., cataloguing network bursts as Global (if they involve more than the 25% of the MEA channels) or Local (if less that 25%). In the first analysis, this division allows to understand the network connectivity developments. The networking increases from div 1 to 6 building up an undifferentiated highly connected network. From div 6 to 10 the networking decreases (pruning) till reaching a plateau in a small-world like organization. The second analysis highlights substantial differences between long period effects of TTX and AP5. Results show that AP5, selectively blocking NMDA receptors and inhibiting long term potentiation, is unable to produce activity twisting in a network that already reached a developmental plateau, but it is able to desynchronize sub-network (Local) activity. TTX, on the other side, blocking any type of electrical communication among neurons, acts on the whole network synchronization. The important activity increment in the post-TTX epoch (+66%), together with the Global activity explosion, suggests the possibility of a long-term inhibitory-synapse depression mechanism.

  2. Interdigitated microelectrode array-coupled bipolar semiconductor photodiode array (IMEA-PDA) microchip for on-chip electrochemiluminescence detection.

    PubMed

    Pal, Sukdeb; Kim, Min Jung; Tak, Yu Kyung; Kwon, Ho Taik; Song, Joon Myong

    2009-10-01

    This paper reports the design, fabrication and testing of a microchip wherein interdigitated microelectrode arrays (IMEA) were integrated with bipolar semiconductor photodiode array (PDA) chip to fabricate a highly compact embodiment for on-chip handling of solutions and electrochemiluminescence (ECL) detection. A 12 x 12 micro array of photodiodes, each coupled with an interdigitated microelectrode array (IMEA), an array of current amplifiers, and a photodiode element-addressing circuit were integrated into a single 2 x 2 cm² IC chip. Each photodiode had dimensions of 300 x 300 μm² and the photodiode-to-photodiode distance was 100 μm. The chip was successfully applied to the on-chip quantification of electro-chemiluminescing probe-labeled single stranded oligonucleotides. The minimum detectable limit at signal/noise ≥ 3 was found to be 5 x 10⁻¹⁴ moles of oligonucleotides with a sample volume as low as 5 microl (i.e., 10 fmole/μl). The attractive features of the developed IMEA-PDA microchip are that a plurality of samples can be analyzed simultaneously using a chip and that for a given sample the data can be averaged from values obtained from multiple, individually addressed pixels. These in turn bring in speed and statistical confidence in analysis. The IMEA-PDA microchip system has the potential to be used as a versatile and highly compact chemical analysis tool for chemical sensing and metrology applications.

  3. Field-programmable lab-on-a-chip based on microelectrode dot array architecture.

    PubMed

    Wang, Gary; Teng, Daniel; Lai, Yi-Tse; Lu, Yi-Wen; Ho, Yingchieh; Lee, Chen-Yi

    2014-09-01

    The fundamentals of electrowetting-on-dielectric (EWOD) digital microfluidics are very strong: advantageous capability in the manipulation of fluids, small test volumes, precise dynamic control and detection, and microscale systems. These advantages are very important for future biochip developments, but the development of EWOD microfluidics has been hindered by the absence of: integrated detector technology, standard commercial components, on-chip sample preparation, standard manufacturing technology and end-to-end system integration. A field-programmable lab-on-a-chip (FPLOC) system based on microelectrode dot array (MEDA) architecture is presented in this research. The MEDA architecture proposes a standard EWOD microfluidic component called 'microelectrode cell', which can be dynamically configured into microfluidic components to perform microfluidic operations of the biochip. A proof-of-concept prototype FPLOC, containing a 30 × 30 MEDA, was developed by using generic integrated circuits computer aided design tools, and it was manufactured with standard low-voltage complementary metal-oxide-semiconductor technology, which allows smooth on-chip integration of microfluidics and microelectronics. By integrating 900 droplet detection circuits into microelectrode cells, the FPLOC has achieved large-scale integration of microfluidics and microelectronics. Compared to the full-custom and bottom-up design methods, the FPLOC provides hierarchical top-down design approach, field-programmability and dynamic manipulations of droplets for advanced microfluidic operations.

  4. Selective Stimulation of the Spinal Cord Surface Using a Stretchable Microelectrode Array

    PubMed Central

    Meacham, Kathleen Williams; Guo, Liang; DeWeerth, Stephen P.; Hochman, Shawn

    2011-01-01

    By electrically stimulating the spinal cord, it is possible to activate functional populations of neurons that modulate motor and sensory function. One method for accessing these neurons is via their associated axons, which project as functionally segregated longitudinal columns of white-matter funiculi (i.e., spinal tracts). To stimulate spinal tracts without penetrating the cord, we have recently developed technology that enables close-proximity, multi-electrode contact with the spinal cord surface. Our stretchable microelectrode arrays (sMEAs) are fabricated using an elastomer polydimethylsiloxane substrate and can be wrapped circumferentially around the spinal cord to optimize electrode contact. Here, sMEAs were used to stimulate the surfaces of rat spinal cords maintained in vitro, and their ability to selectively activate axonal surface tracts was compared to rigid bipolar tungsten microelectrodes pressed firmly onto the cord surface. Along dorsal column tracts, the axonal response to sMEA stimulation was compared to that evoked by rigid microelectrodes through measurement of their evoked axonal compound action potentials (CAPs). Paired t-tests failed to reveal significant differences between the sMEA’s and the rigid microelectrode’s stimulus resolution, or in their ranges of evoked CAP conduction velocities. Additionally, dual-site stimulation using sMEA electrodes recruited spatially distinct populations of spinal axons. Site-specific stimulation of the ventrolateral funiculus – a tract capable of evoking locomotor-like activity – recruited ventral root efferent activity that spanned several spinal segments. These findings indicate that the sMEA stimulates the spinal cord surface with selectivity similar to that of rigid microelectrodes, while possessing potential advantages concerning circumferential contact and mechanical compatibility with the cord surface. PMID:21541256

  5. Pre-implantation electrochemical characterization of a Parylene C sheath microelectrode array probe.

    PubMed

    Hara, Seth A; Kim, Brian J; Kuo, Jonathan T W; Lee, Curtis; Gutierrez, Christian A; Hoang, Tuan; Meng, Ellis

    2012-01-01

    We present the preliminary electrochemical characterization of 3D Parylene C sheath microelectrode array probes towards realizing reliable chronic neuroprosthetic recordings. Electrochemical techniques were used to verify electrode integrity after our novel post-fabrication thermoforming process was applied to flat surface micromachined structures to achieve a hollow sheath probe shape. Characterization of subsequent neurotrophic coatings was performed and accelerated life testing was used to simulate six months in vivo. Prior to probe implantation, crosstalk was measured and electrode surface properties were evaluated through the use of electrochemical impedance spectroscopy.

  6. Microelectrode Array Recordings from the Ventral Roots in Chronically Implanted Cats

    PubMed Central

    Debnath, Shubham; Bauman, Matthew J.; Fisher, Lee E.; Weber, Douglas J.; Gaunt, Robert A.

    2014-01-01

    The ventral spinal roots contain the axons of spinal motoneurons and provide the only location in the peripheral nervous system where recorded neural activity can be assured to be motor rather than sensory. This study demonstrates recordings of single unit activity from these ventral root axons using floating microelectrode arrays (FMAs). Ventral root recordings were characterized by examining single unit yield and signal-to-noise ratios (SNR) with 32-channel FMAs implanted chronically in the L6 and L7 spinal roots of nine cats. Single unit recordings were performed for implant periods of up to 12 weeks. Motor units were identified based on active discharge during locomotion and inactivity under anesthesia. Motor unit yield and SNR were calculated for each electrode, and results were grouped by electrode site size, which were varied systematically between 25 and 160 μm to determine effects on signal quality. The unit yields and SNR did not differ significantly across this wide range of electrode sizes. Both SNR and yield decayed over time, but electrodes were able to record spikes with SNR >2 up to 12 weeks post-implant. These results demonstrate that it is feasible to record single unit activity from multiple isolated motor units with penetrating microelectrode arrays implanted chronically in the ventral spinal roots. This approach could be useful for creating a spinal nerve interface for advanced neural prostheses, and results of this study will be used to improve design of microelectrodes for chronic neural recording in the ventral spinal roots. PMID:25071697

  7. Development of Microelectrode Arrays Using Electroless Plating for CMOS-Based Direct Counting of Bacterial and HeLa Cells.

    PubMed

    Niitsu, Kiichi; Ota, Shoko; Gamo, Kohei; Kondo, Hiroki; Hori, Masaru; Nakazato, Kazuo

    2015-10-01

    The development of two new types of high-density, electroless plated microelectrode arrays for CMOS-based high-sensitivity direct bacteria and HeLa cell counting are presented. For emerging high-sensitivity direct pathogen counting, two technical challenges must be addressed. One is the formation of a bacteria-sized microelectrode, and the other is the development of a high-sensitivity and high-speed amperometry circuit. The requirement for microelectrode formation is that the gold microelectrodes are required to be as small as the target cell. By improving a self-aligned electroless plating technique, the dimensions of the microelectrodes on a CMOS sensor chip in this work were successfully reduced to 1.2 μm × 2.05 μm. This is 1/20th of the smallest size reported in the literature. Since a bacteria-sized microelectrode has a severe limitation on the current flow, the amperometry circuit has to have a high sensitivity and high speed with low noise. In this work, a current buffer was inserted to mitigate the potential fluctuation. Three test chips were fabricated using a 0.6- μm CMOS process: two with 1.2 μm × 2.05 μm (1024 × 1024 and 4 × 4) sensor arrays and one with 6- μm square (16 × 16) sensor arrays; and the microelectrodes were formed on them using electroless plating. The uniformity among the 1024 × 1024 electrodes arranged with a pitch of 3.6 μm × 4.45 μm was optically verified. For improving sensitivity, the trenches on each microelectrode were developed and verified optically and electrochemically for the first time. Higher sensitivity can be achieved by introducing a trench structure than by using a conventional microelectrode formed by contact photolithography. Cyclic voltammetry (CV) measurements obtained using the 1.2 μm × 2.05 μm 4 × 4 and 6- μm square 16 × 16 sensor array with electroless-plated microelectrodes successfully demonstrated direct counting of the bacteria-sized microbeads and HeLa cells.

  8. Spatially and Temporally Resolved Single-Cell Exocytosis Utilizing Individually Addressable Carbon Microelectrode Arrays

    PubMed Central

    Zhang, Bo; Adams, Kelly L.; Luber, Sarah J.; Eves, Daniel J.; Heien, Michael L.; Ewing, Andrew G.

    2009-01-01

    We report the fabrication and characterization of carbon microelectrode arrays (MEAs) and their application to spatially and temporally resolve neurotransmitter release from single pheochromocytoma (PC12) cells. The carbon MEAs are composed of individually addressable 2.5-μm-radius microdisks embedded in glass. The fabrication involves pulling a multibarrel glass capillary containing a single carbon fiber in each barrel into a sharp tip, followed by beveling the electrode tip to form an array (10−20 μm) of carbon microdisks. This simple fabrication procedure eliminates the need for complicated wiring of the independent electrodes, thus allowing preparation of high-density individually addressable microelectrodes. The carbon MEAs have been characterized using scanning electron microscopy, steady-state and fast-scan voltammetry, and numerical simulations. Amperometric results show that subcellular heterogeneity in single-cell exocytosis can be electrochemically detected with MEAs. These ultrasmall electrochemical probes are suitable for detecting fast chemical events in tight spaces, as well as for developing multifunctional electrochemical microsensors. PMID:18232712

  9. A Multimodal, SU-8 - Platinum - Polyimide Microelectrode Array for Chronic In Vivo Neurophysiology

    PubMed Central

    Márton, Gergely; Orbán, Gábor; Kiss, Marcell; Fiáth, Richárd; Pongrácz, Anita; Ulbert, István

    2015-01-01

    Utilization of polymers as insulator and bulk materials of microelectrode arrays (MEAs) makes the realization of flexible, biocompatible sensors possible, which are suitable for various neurophysiological experiments such as in vivo detection of local field potential changes on the surface of the neocortex or unit activities within the brain tissue. In this paper the microfabrication of a novel, all-flexible, polymer-based MEA is presented. The device consists of a three dimensional sensor configuration with an implantable depth electrode array and brain surface electrodes, allowing the recording of electrocorticographic (ECoG) signals with laminar ones, simultaneously. In vivo recordings were performed in anesthetized rat brain to test the functionality of the device under both acute and chronic conditions. The ECoG electrodes recorded slow-wave thalamocortical oscillations, while the implanted component provided high quality depth recordings. The implants remained viable for detecting action potentials of individual neurons for at least 15 weeks. PMID:26683306

  10. Tracking axonal action potential propagation on a high-density microelectrode array across hundreds of sites.

    PubMed

    Bakkum, Douglas J; Frey, Urs; Radivojevic, Milos; Russell, Thomas L; Müller, Jan; Fiscella, Michele; Takahashi, Hirokazu; Hierlemann, Andreas

    2013-01-01

    Axons are traditionally considered stable transmission cables, but evidence of the regulation of action potential propagation demonstrates that axons may have more important roles. However, their small diameters render intracellular recordings challenging, and low-magnitude extracellular signals are difficult to detect and assign. Better experimental access to axonal function would help to advance this field. Here we report methods to electrically visualize action potential propagation and network topology in cortical neurons grown over custom arrays, which contain 11,011 microelectrodes and are fabricated using complementary metal oxide semiconductor technology. Any neuron lying on the array can be recorded at high spatio-temporal resolution, and simultaneously precisely stimulated with little artifact. We find substantial velocity differences occurring locally within single axons, suggesting that the temporal control of a neuron's output may contribute to neuronal information processing.

  11. Quantifying long-term microelectrode array functionality using chronic in vivo impedance testing

    NASA Astrophysics Data System (ADS)

    Prasad, Abhishek; Sanchez, Justin C.

    2012-04-01

    Long-term acquisition of high-quality neural recordings is a cornerstone of neuroprosthetic system design. Mitigating the experimental variability of chronically implanted arrays has been a formidable task because the sensor recording sites can be influenced by biotic and abiotic responses. Several studies have implicated changes in electrical interface impedance as a preliminary marker to infer electrode viability. Microelectrode impedance plays an important role in the monitoring of low amplitude and high-resolution extracellular neural signals. In this work, we seek to quantify long-term microelectrode array functionality and derive an impedance-based predictor for electrode functionality that correlates the recording site electrical properties with the functional neuronal recordings in vivo. High temporal resolution metrics of this type would allow one to assess, predict, and improve electrode performance in the future. In a large cohort of animals, we performed daily impedance measurements and neural signal recordings over long periods (up to 21 weeks) of time in rats using tungsten microwire arrays implanted into the somatosensory cortex. This study revealed that there was a time-varying trend in the modulation of impedance that was related to electrode performance. Single units were best detected from electrodes at time points when the electrode entered into the 40-150 KΩ impedance range. This impedance trend was modeled across the full cohort of animals to predict future electrode performance. The model was tested on data from all animals and was able to provide predictions of electrode performance chronically. Insight from this study can be combined with knowledge of electrode materials and histological analysis to provide a more comprehensive predictive model of electrode failure in the future.

  12. [Finite element analysis of temperature field of retina by electrical stimulation with microelectrode array].

    PubMed

    Wang, Wei; Qiao, Qingli; Gao, Weiping; Wu, Jun

    2014-12-01

    We studied the influence of electrode array parameters on temperature distribution to the retina during the use of retinal prosthesis in order to avoid thermal damage to retina caused by long-term electrical stimulation. Based on real epiretinal prosthesis, a three-dimensional model of electrical stimulation for retina with 4 X 4 microelectrode array had been established using the finite element software (COMSOL Multiphysics). The steady-state temperature field of electrical stimulation of the retina was calculated, and the effects of the electrode parameters such as the distance between the electrode contacts, the materials and area of the electrode contact on temperature field were considered. The maximum increase in the retina steady temperature was about 0. 004 degrees C with practical stimulation current. When the distance between the electrode contacts was changed from 130 microm to 520 microm, the temperature was reduced by about 0.006 microC. When the contact radius was doubled from 130 microm to 260 microm, the temperature decrease was about 0.005 degrees C. It was shown that there were little temperature changes in the retina with a 4 x 4 epiretinal microelectrode array, reflecting the safety of electrical stimulation. It was also shown that the maximum temperature in the retina decreased with increasing the distance between the electrode contacts, as well as increasing the area of electrode contact. However, the change of the maximum temperature was very small when the distance became larger than the diameter of electrode contact. There was no significant difference in the effects of temperature increase among the different electrode materials. Rational selection of the distance between the electrode contacts and their area in electrode design can reduce the temperature rise induced by electrical stimulation.

  13. Platinum nanowire microelectrode arrays for neurostimulation applications: Fabrication, characterization, and in-vitro retinal cell stimulation

    NASA Astrophysics Data System (ADS)

    Whalen, John J., III

    Implantable electrical neurostimulating devices are being developed for a number of applications, including artificial vision through retinal stimulation. The epiretinal prosthesis will use a two-dimensional array microelectrodes to address individual cells of the retina. MEMS fabrication processes can produce arrays of microelectrodes with these dimensions, but there are two critical issues that they cannot satisfy. One, the stimulating electrodes are the only part of the implanted electrical device that penetrate through the water impermeable package, and must do so without sacrificing hermeticity. Two, As electrode size decreases, the current density (A cm-2 ) increases, due to increased electrochemical impedance. This reduces the amount of charge that can be safely injected into the tissue. To date, MEMS processing method, cannot produce electrode arrays with good, prolonged hermetic properties. Similarly, MEMS approaches do not account for the increased impedance caused by decreased surface area. For these reasons there is a strong motivation for the development of a water-impermeable, substrate-penetrating electrode array with low electrochemical impedance. This thesis presents a stimulating electrode array fabricated from platinum nanowires using a modified electrochemical template synthesis approach. Nanowires are electrochemically deposited from ammonium hexachloroplatinate solution into lithographically patterned nanoporous anodic alumina templates to produce microarrays of platinum nanowires. The platinum nanowires penetrating through the ceramic aluminum oxide template serve as parallel electrical conduits through the water impermeable, electrically insulating substrate. Electrode impedance can be adjusted by either controlling the nanowire hydrous platinum oxide content or by partially etching the alumina template to expose additional surface area. A stepwise approach to this project was taken. First, the electrochemistry of ammonium

  14. 3D-nanostructured boron-doped diamond for microelectrode array neural interfacing.

    PubMed

    Piret, Gaëlle; Hébert, Clément; Mazellier, Jean-Paul; Rousseau, Lionel; Scorsone, Emmanuel; Cottance, Myline; Lissorgues, Gaelle; Heuschkel, Marc O; Picaud, Serge; Bergonzo, Philippe; Yvert, Blaise

    2015-06-01

    The electrode material is a key element in the design of long-term neural implants and neuroprostheses. To date, the ideal electrode material offering high longevity, biocompatibility, low-noise recording and high stimulation capabilities remains to be found. We show that 3D-nanostructured boron doped diamond (BDD), an innovative material consisting in a chemically stable material with a high aspect ratio structure obtained by encapsulation of a carbon nanotube template within two BDD nanolayers, allows neural cell attachment, survival and neurite extension. Further, we developed arrays of 20-μm-diameter 3D-nanostructured BDD microelectrodes for neural interfacing. These microelectrodes exhibited low impedances and low intrinsic recording noise levels. In particular, they allowed the detection of low amplitude (10-20 μV) local-field potentials, single units and multiunit bursts neural activity in both acute whole embryonic hindbrain-spinal cord preparations and long-term hippocampal cell cultures. Also, cyclic voltammetry measurements showed a wide potential window of about 3 V and a charge storage capacity of 10 mC.cm(-2), showing high potentiality of this material for neural stimulation. These results demonstrate the attractiveness of 3D-nanostructured BDD as a novel material for neural interfacing, with potential applications for the design of biocompatible neural implants for the exploration and rehabilitation of the nervous system.

  15. Microfabrication, characterization and in vivo MRI compatibility of diamond microelectrodes array for neural interfacing.

    PubMed

    Hébert, Clément; Warnking, Jan; Depaulis, Antoine; Garçon, Laurie Amandine; Mermoux, Michel; Eon, David; Mailley, Pascal; Omnès, Franck

    2015-01-01

    Neural interfacing still requires highly stable and biocompatible materials, in particular for in vivo applications. Indeed, most of the currently used materials are degraded and/or encapsulated by the proximal tissue leading to a loss of efficiency. Here, we considered boron doped diamond microelectrodes to address this issue and we evaluated the performances of a diamond microelectrode array. We described the microfabrication process of the device and discuss its functionalities. We characterized its electrochemical performances by cyclic voltammetry and impedance spectroscopy in saline buffer and observed the typical diamond electrode electrochemical properties, wide potential window and low background current, allowing efficient electrochemical detection. The charge storage capacitance and the modulus of the electrochemical impedance were found to remain in the same range as platinum electrodes used for standard commercial devices. Finally we observed a reduced Magnetic Resonance Imaging artifact when the device was implanted on a rat cortex, suggesting that boron doped-diamond is a very promising electrode material allowing functional imaging.

  16. Hydrophilic modification of neural microelectrode arrays based on multi-walled carbon nanotubes

    NASA Astrophysics Data System (ADS)

    Chen, Chang-Hsiao; Su, Huan-Chieh; Chuang, Shih-Chang; Yen, Shiang-Jie; Chen, Yung-Chan; Lee, Yu-Tao; Chen, Hsin; Yew, Tri-Rung; Chang, Yen-Chung; Yeh, Shih-Rung; Yao, Da-Jeng

    2010-12-01

    To decrease the impedance of microelectrode arrays, for neuroscience applications we have fabricated and tested MEA based on multi-walled carbon nanotubes. With decreasing physical size of a microelectrode, its impedance increases and charge-transfer capability decreases. To decrease the impedance, the effective surface area of the electrode must generally be increased. We explored the effect of plasma treatment on the surface wettability of MWCNT. With a steam-plasma treatment the surface of MWCNT becomes converted from superhydrophobic to superhydrophilic; this hydrophilic property is attributed to -OH bonding on the surface of MWCNT. We reported the synthesis at 400 °C of MWCNT on nickel-titanium multilayered metal catalysts by thermal chemical vapor deposition. Applying plasma with a power less than 25 W for 10 s improved the electrochemical and biological properties, and circumvented the limitation of the surface reverting to a hydrophobic condition; a hydrophilic state is maintained for at least one month. The MEA was used to record neural signals of a lateral giant cell from an American crayfish. The response amplitude of the action potential was about 275 µV with 1 ms period; the recorded data had a ratio of signal to noise up to 40.12 dB. The improved performance of the electrode makes feasible the separation of neural signals and the recognition of their distinct shapes. With further development the rapid treatment will be useful for long-term recording applications.

  17. Evaluation of the Neuroactivity of ToxCast Compounds Using Multi-well Microelectrode Array Recordings in Primary Cortical Neurons

    EPA Science Inventory

    Evaluation of the Neuroactivity of ToxCast Compounds Using Multi-well Microelectrode Array Recordings in Primary Cortical Neurons P Valdivia1, M Martin2, WR LeFew3, D Hall3, J Ross1, K Houck2 and TJ Shafer3 1Axion Biosystems, Atlanta GA and 2NCCT, 3ISTD, NHEERL, ORD, US EPA, RT...

  18. Further Evaluation of DNT Hazard Screening using Neural Networks from Rat Cortical Neurons on Multi-well Microelectrode Arrays

    EPA Science Inventory

    Thousands of chemicals have not been characterized for their DNT potential. Due to the need for DNT hazard identification, efforts to develop screening assays for DNT potential is a high priority. Multi-well microelectrode arrays (MEA) measure the spontaneous activity of electr...

  19. Multielement microelectrode array sensors and compact instrumentation development at Lawrence Livermore National Laboratory

    SciTech Connect

    Glass, R.S.; Balazs, G.B.; Ciarlo, D.R.; Hargrove, D.L.

    1994-08-01

    The increasing emphasis on environmental issues, waste reduction, and improved efficiency for industrial processes has spurred the development of new chemical sensors for field, or in-plant use. Specifically, sensors are needed to gauge the effectiveness of remediation efforts for sites which have become contaminated, to effect waste minimization, and to detect the presence of toxic, hazardous, or otherwise regulated chemicals in waste effluents, drinking water, and other environmental systems. In this regard, electrochemical sensors are particularly useful for the measurement of inorganics in aqueous systems. Electrochemical sensors have the attractive features of high sensitivity, low cost, small size, versatility of use, and are capable of stand-alone operation. This paper reviews our work on the development of microelectrode array sensors and user-friendly, compact instrumentation which we have developed for environmental and process control applications.

  20. Boron-doped nanocrystalline diamond microelectrode arrays monitor cardiac action potentials.

    PubMed

    Maybeck, Vanessa; Edgington, Robert; Bongrain, Alexandre; Welch, Joseph O; Scorsone, Emanuel; Bergonzo, Philippe; Jackman, Richard B; Offenhäusser, Andreas

    2014-02-01

    The expansion of diamond-based electronics in the area of biological interfacing has not been as thoroughly explored as applications in electrochemical sensing. However, the biocompatibility of diamond, large safe electrochemical window, stability, and tunable electronic properties provide opportunities to develop new devices for interfacing with electrogenic cells. Here, the fabrication of microelectrode arrays (MEAs) with boron-doped nanocrystalline diamond (BNCD) electrodes and their interfacing with cardiomyocyte-like HL-1 cells to detect cardiac action potentials are presented. A nonreductive means of structuring doped and undoped diamond on the same substrate is shown. The resulting BNCD electrodes show high stability under mechanical stress generated by the cells. It is shown that by fabricating the entire surface of the MEA with NCD, in patterns of conductive doped, and isolating undoped regions, signal detection may be improved up to four-fold over BNCD electrodes passivated with traditional isolators.

  1. A Research on Sour Sensation Mechanism of Fungiform Taste Receptor Cells Based on Microelectrode Array

    NASA Astrophysics Data System (ADS)

    Zhang, Wei; Chen, Peihua; Xiao, Lidan; Liu, Qingjun; Wang, Ping

    2009-05-01

    Taste receptor cells as the fundamental units of taste sensation are not only passive receivers to outside stimulus, but some primary process for the signals and information. In this paper, an innovation on acquisition of taste receptor cells was introduced and larger amount of cells could be obtained. A multichannel microelectrode array (MEA) system was applied in signal recording, which is used in non-invasive, multiple and simultaneous extracellular recording of taste receptor cells. The cells were treated with sour solutions of different pHs, and the relations between concentration of hydrogen and firing rate were observed. Firing rates on pH 7, pH 4 and pH 2 were approximately 1.38±0.01 (MEAN±SE)/s, 1.61±0.07/s and 2.75+0.15/s.

  2. The potential of microelectrode arrays and microelectronics for biomedical research and diagnostics.

    PubMed

    Jones, Ian L; Livi, Paolo; Lewandowska, Marta K; Fiscella, Michele; Roscic, Branka; Hierlemann, Andreas

    2011-03-01

    Planar microelectrode arrays (MEAs) are devices that can be used in biomedical and basic in vitro research to provide extracellular electrophysiological information about biological systems at high spatial and temporal resolution. Complementary metal oxide semiconductor (CMOS) is a technology with which MEAs can be produced on a microscale featuring high spatial resolution and excellent signal-to-noise characteristics. CMOS MEAs are specialized for the analysis of complete electrogenic cellular networks at the cellular or subcellular level in dissociated cultures, organotypic cultures, and acute tissue slices; they can also function as biosensors to detect biochemical events. Models of disease or the response of cellular networks to pharmacological compounds can be studied in vitro, allowing one to investigate pathologies, such as cardiac arrhythmias, memory impairment due to Alzheimer's disease, or vision impairment caused by ganglion cell degeneration in the retina.

  3. Measurement of electrical conduction properties of intact embryonic murine hearts by extracellular microelectrode arrays.

    PubMed

    Taylor, David G; Natarajan, Anupama

    2012-01-01

    The study of the embryonic development of the cardiac conduction system and its congenital and toxicological defects requires protocols to measure electrical conduction through the myocardium. However, available methods either lack spatial information, necessitate the hearts to be sliced and mounted, or require specialized equipment. Microelectrode arrays (MEAs) are plates with embedded surface electrodes to measure localized extracellular ionic currents (field potentials) created by the depolarization and repolarization of cultured cells and tissue slices. Here we describe a protocol using MEAs to examine electrical conduction through intact and beating cultured hearts isolated from mouse embryos at 10.5 days postcoitus. This method allows measurements of conduction time, estimates of conduction velocity, atrioventricular conduction delay and block, and heart rate and rhythmicity.

  4. Iridium oxide microelectrode arrays for in vitro stimulation of individual rat neurons from dissociated cultures.

    PubMed

    Eick, Stefan; Wallys, Jens; Hofmann, Boris; van Ooyen, André; Schnakenberg, Uwe; Ingebrandt, Sven; Offenhäusser, Andreas

    2009-01-01

    We present the first in vitro extracellular stimulation of individual neurons from dissociated cultures with iridium oxide (IrO(x)) electrodes. Microelectrode arrays with sputtered IrO(x) films (SIROF) were developed for electrophysiological investigations with electrogenic cells. The microelectrodes were characterized with scanning electron and atomic force microscopy, revealing rough and porous electrodes with enlarged surface areas. As shown by cyclic voltammetry and electrochemical impedance spectroscopy, the large surface area in combination with the good electrochemical properties of SIROF resulted in high charge storage capacity and low electrode impedance. Thus, we could transfer the good properties of IrO(x) as material for in vivo stimulation electrodes to multi-electrode arrays with electrode diameters as small as 10 mum for in vitro applications. Single rat cortical neurons from dissociated cultures were successfully stimulated to fire action potentials using single or trains of biphasic rectangular voltage-controlled stimulation pulses. The stimulated cell's membrane potential was simultaneously monitored using whole-cell current-clamp recordings. This experimental configuration allowed direct evaluation of the influence of pulse phase sequence, amplitude, and number on the stimulation success ratio and action potential latency. Negative phase first pulses were more effective for extracellular stimulation and caused reduced latency in comparison to positive phase first pulses. Increasing the pulse amplitude also improved stimulation reliability. However, in order to prevent cell or electrode damage, the pulse amplitude is limited to voltages below the threshold for irreversible electrochemical reactions at the electrode. As an alternative to increasing the amplitude, a higher number of stimulation pulses was also shown to increase stimulation success.

  5. Iridium Oxide Microelectrode Arrays for In Vitro Stimulation of Individual Rat Neurons from Dissociated Cultures

    PubMed Central

    Eick, Stefan; Wallys, Jens; Hofmann, Boris; van Ooyen, André; Schnakenberg, Uwe; Ingebrandt, Sven; Offenhäusser, Andreas

    2009-01-01

    We present the first in vitro extracellular stimulation of individual neurons from dissociated cultures with iridium oxide (IrOx) electrodes. Microelectrode arrays with sputtered IrOx films (SIROF) were developed for electrophysiological investigations with electrogenic cells. The microelectrodes were characterized with scanning electron and atomic force microscopy, revealing rough and porous electrodes with enlarged surface areas. As shown by cyclic voltammetry and electrochemical impedance spectroscopy, the large surface area in combination with the good electrochemical properties of SIROF resulted in high charge storage capacity and low electrode impedance. Thus, we could transfer the good properties of IrOx as material for in vivo stimulation electrodes to multi-electrode arrays with electrode diameters as small as 10 μm for in vitro applications. Single rat cortical neurons from dissociated cultures were successfully stimulated to fire action potentials using single or trains of biphasic rectangular voltage-controlled stimulation pulses. The stimulated cell's membrane potential was simultaneously monitored using whole-cell current-clamp recordings. This experimental configuration allowed direct evaluation of the influence of pulse phase sequence, amplitude, and number on the stimulation success ratio and action potential latency. Negative phase first pulses were more effective for extracellular stimulation and caused reduced latency in comparison to positive phase first pulses. Increasing the pulse amplitude also improved stimulation reliability. However, in order to prevent cell or electrode damage, the pulse amplitude is limited to voltages below the threshold for irreversible electrochemical reactions at the electrode. As an alternative to increasing the amplitude, a higher number of stimulation pulses was also shown to increase stimulation success. PMID:19949459

  6. Reusable conductimetric array of interdigitated microelectrodes for the readout of low-density microarrays.

    PubMed

    Mallén, Maria; Díaz-González, María; Bonilla, Diana; Salvador, Juan P; Marco, María P; Baldi, Antoni; Fernández-Sánchez, César

    2014-06-17

    Low-density protein microarrays are emerging tools in diagnostics whose deployment could be primarily limited by the cost of fluorescence detection schemes. This paper describes an electrical readout system of microarrays comprising an array of gold interdigitated microelectrodes and an array of polydimethylsiloxane microwells, which enabled multiplexed detection of up to thirty six biological events on the same substrate. Similarly to fluorescent readout counterparts, the microarray can be developed on disposable glass slide substrates. However, unlike them, the presented approach is compact and requires a simple and inexpensive instrumentation. The system makes use of urease labeled affinity reagents for developing the microarrays and is based on detection of conductivity changes taking place when ionic species are generated in solution due to the catalytic hydrolysis of urea. The use of a polydimethylsiloxane microwell array facilitates the positioning of the measurement solution on every spot of the microarray. Also, it ensures the liquid tightness and isolation from the surrounding ones during the microarray readout process, thereby avoiding evaporation and chemical cross-talk effects that were shown to affect the sensitivity and reliability of the system. The performance of the system is demonstrated by carrying out the readout of a microarray for boldenone anabolic androgenic steroid hormone. Analytical results are comparable to those obtained by fluorescent scanner detection approaches. The estimated detection limit is 4.0 ng mL(-1), this being below the threshold value set by the World Anti-Doping Agency and the European Community.

  7. A novel stretchable micro-electrode array (SMEA) design for directional stretching of cells

    NASA Astrophysics Data System (ADS)

    Khoshfetrat Pakazad, S.; Savov, A.; van de Stolpe, A.; Dekker, R.

    2014-03-01

    Stretchable micro-electrode arrays (SMEAs) are useful tools to study the electrophysiology of living cells seeded on the devices under mechanical stimulation. For such applications, the SMEAs are used as cell culture substrates; therefore, the surface topography and mechanical properties of the devices should be minimally affected by the embedded stretchable electrical interconnects. In this paper, a novel design and micro-fabrication technology for a pneumatically actuated SMEA are presented to achieve stretchability with minimal surface area dedicated to the electrical interconnects and a well-defined surface strain distribution combined with integrated diverse micro-patterns to enable alignment and directional stretching of cells. The special mechanical design also enables the SMEA to have a prolonged electro-mechanical fatigue life time required for long-term cyclic stretching of the cell cultures (stable resistance of electrical interconnects for more than 160 thousand cycles of 20% stretching and relaxing). The proposed fabrication method is based on the state of the art micro-fabrication techniques and materials and circumvents the processing problems associated with using unconventional methods and materials to fabricate stretchable electrode arrays. The electrochemical impedance spectroscopy characterization of the SMEA shows 4.5 MΩ impedance magnitude at 1 kHz for a TiN electrode 12 um in diameter. Cell culture experiments demonstrate the robustness of the SMEAs for long-term culturing experiments and compatibility with inverted fluorescent microscopy.

  8. Neural Activity Propagation in an Unfolded Hippocampal Preparation with a Penetrating Micro-electrode Array

    PubMed Central

    Gonzales-Reyes, Luis E.; Durand, Dominique M.

    2015-01-01

    This protocol describes a method for preparing a new in vitro flat hippocampus preparation combined with a micro-machined array to map neural activity in the hippocampus. The transverse hippocampal slice preparation is the most common tissue preparation to study hippocampus electrophysiology. A longitudinal hippocampal slice was also developed in order to investigate longitudinal connections in the hippocampus. The intact mouse hippocampus can also be maintained in vitro because its thickness allows adequate oxygen diffusion. However, these three preparations do not provide direct access to neural propagation since some of the tissue is either missing or folded. The unfolded intact hippocampus provides both transverse and longitudinal connections in a flat configuration for direct access to the tissue to analyze the full extent of signal propagation in the hippocampus in vitro. In order to effectively monitor the neural activity from the cell layer, a custom made penetrating micro-electrode array (PMEA) was fabricated and applied to the unfolded hippocampus. The PMEA with 64 electrodes of 200 µm in height could record neural activity deep inside the mouse hippocampus. The unique combination of an unfolded hippocampal preparation and the PMEA provides a new in-vitro tool to study the speed and direction of propagation of neural activity in the two-dimensional CA1-CA3 regions of the hippocampus with a high signal to noise ratio. PMID:25868081

  9. Silicon Micromachined Microlens Array for THz Antennas

    NASA Technical Reports Server (NTRS)

    Lee, Choonsup; Chattopadhyay, Goutam; Mehdi, IImran; Gill, John J.; Jung-Kubiak, Cecile D.; Llombart, Nuria

    2013-01-01

    5 5 silicon microlens array was developed using a silicon micromachining technique for a silicon-based THz antenna array. The feature of the silicon micromachining technique enables one to microfabricate an unlimited number of microlens arrays at one time with good uniformity on a silicon wafer. This technique will resolve one of the key issues in building a THz camera, which is to integrate antennas in a detector array. The conventional approach of building single-pixel receivers and stacking them to form a multi-pixel receiver is not suited at THz because a single-pixel receiver already has difficulty fitting into mass, volume, and power budgets, especially in space applications. In this proposed technique, one has controllability on both diameter and curvature of a silicon microlens. First of all, the diameter of microlens depends on how thick photoresist one could coat and pattern. So far, the diameter of a 6- mm photoresist microlens with 400 m in height has been successfully microfabricated. Based on current researchers experiences, a diameter larger than 1-cm photoresist microlens array would be feasible. In order to control the curvature of the microlens, the following process variables could be used: 1. Amount of photoresist: It determines the curvature of the photoresist microlens. Since the photoresist lens is transferred onto the silicon substrate, it will directly control the curvature of the silicon microlens. 2. Etching selectivity between photoresist and silicon: The photoresist microlens is formed by thermal reflow. In order to transfer the exact photoresist curvature onto silicon, there needs to be etching selectivity of 1:1 between silicon and photoresist. However, by varying the etching selectivity, one could control the curvature of the silicon microlens. The figure shows the microfabricated silicon microlens 5 x5 array. The diameter of the microlens located in the center is about 2.5 mm. The measured 3-D profile of the microlens surface has a

  10. Spatial and temporal characteristics of V1 microstimulation during chronic implantation of a microelectrode array in a behaving macaque

    NASA Astrophysics Data System (ADS)

    Davis, T. S.; Parker, R. A.; House, P. A.; Bagley, E.; Wendelken, S.; Normann, R. A.; Greger, B.

    2012-12-01

    Objective. It has been hypothesized that a vision prosthesis capable of evoking useful visual percepts can be based upon electrically stimulating the primary visual cortex (V1) of a blind human subject via penetrating microelectrode arrays. As a continuation of earlier work, we examined several spatial and temporal characteristics of V1 microstimulation. Approach. An array of 100 penetrating microelectrodes was chronically implanted in V1 of a behaving macaque monkey. Microstimulation thresholds were measured using a two-alternative forced choice detection task. Relative locations of electrically-evoked percepts were measured using a memory saccade-to-target task. Main results. The principal finding was that two years after implantation we were able to evoke behavioural responses to electric stimulation across the spatial extent of the array using groups of contiguous electrodes. Consistent responses to stimulation were evoked at an average threshold current per electrode of 204 ± 49 µA (mean ± std) for groups of four electrodes and 91 ± 25 µA for groups of nine electrodes. Saccades to electrically-evoked percepts using groups of nine electrodes showed that the animal could discriminate spatially distinct percepts with groups having an average separation of 1.6 ± 0.3 mm (mean ± std) in cortex and 1.0° ± 0.2° in visual space. Significance. These results demonstrate chronic perceptual functionality and provide evidence for the feasibility of a cortically-based vision prosthesis for the blind using penetrating microelectrodes.

  11. Develop Silicone Encapsulation Systems for Terrestrial Silicon Solar Arrays

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The results for Task 3 of the Low Cost Solar Array Project are presented. Task 3 is directed toward the development of a cost effective encapsulating system for photovoltaic modules using silicon based materials. The technical approach of the contract effort is divided into four special tasks: (1) technology review; (2) generation of concepts for screening and processing silicon encapsulation systems; (3) assessment of encapsulation concepts; and (4) evaluation of encapsulation concepts. The candidate silicon materials are reviewed. The silicon and modified silicon resins were chosen on the basis of similarity to materials with known weatherability, cost, initial tangential modulus, accelerated dirt pick-up test results and the ratio of the content of organic phenyl substitution of methyl substitution on the backbone of the silicon resin.

  12. Penetrating microelectrode arrays with low-impedance sputtered iridium oxide electrode coatings.

    PubMed

    Cogan, Stuart F; Ehrlich, Julia; Plante, Timothy D; Van Wagenen, Rick

    2009-01-01

    Sputtered iridium oxide (SIROF) is a candidate low-impedance coating for neural stimulation and recording electrodes. SIROF on planar substrates has exhibited a high charge-injection capacity and impedance suitable for indwelling cortical microelectrode applications. In the present work, the properties of SIROF electrode coatings deposited onto multi-shank penetrating arrays intended for intracortical and intraneural applications were examined. The charge-injection properties under constant current pulsing were evaluated for a range of pulsewidths and current densities using voltage transients to determine maximum potential excursions in an inorganic model of interstitial fluid at 37 degrees C. The charge-injection capacity of the SIROFs was significantly improved by the use of positive potential biasing in the interpulse period, but even without bias, the SIROFs reversibly inject higher charge than other iridium oxides or platinum. Typical deliverable charge levels of 25 to 160 nC/phase were obtained with 2000 mum(2) electrodes depending on pulsewidth and interpulse bias. Similar sized platinum electrodes could inject 3 to 8 nC/phase.

  13. Establishment of a Long-Term Chick Forebrain Neuronal Culture on a Microelectrode Array Platform.

    PubMed

    Kuang, Serena Y; Huang, Ting; Wang, Zhonghai; Lin, Yongliang; Kindy, Mark; Xi, Tingfei; Gao, Bruce Z

    2015-01-01

    The biosensor system formed by culturing primary animal neurons on a microelectrode array (MEA) platform is drawing an increasing research interest for its power as a rapid, sensitive, functional neurotoxicity assessment, as well as for many other electrophysiological related research purposes. In this paper, we established a long-term chick forebrain neuron culture (C-FBN-C) on MEAs with a more than 5 month long lifespan and up to 5 month long stability in morphology and physiological function; characterized the C-FBN-C morphologically, functionally, and developmentally; partially compared its functional features with rodent counterpart; and discussed its pros and cons as a novel biosensor system in comparison to rodent counterpart and human induced pluripotent stem cells (hiPSCs). Our results show that C-FBN-C on MEA platform 1) can be used as a biosensor of its own type in a wide spectrum of basic biomedical research; 2) is of value in comparative physiology in cross-species studies; and 3) may have potential to be used as an alternative, cost-effective approach to rodent counterpart within shared common functional domains (such as specific types of ligand-gated ion channel receptors and subtypes expressed in the cortical tissues of both species) in large-scale environmental neurotoxicant screening that would otherwise require millions of animals.

  14. Modulation of cultured neural networks using neurotrophin release from hydrogel-coated microelectrode arrays

    NASA Astrophysics Data System (ADS)

    Jun, Sang Beom; Hynd, Matthew R.; Dowell-Mesfin, Natalie M.; Al-Kofahi, Yousef; Roysam, Badrinath; Shain, William; Kim, Sung June

    2008-06-01

    Polyacrylamide and poly(ethylene glycol) diacrylate hydrogels were synthesized and characterized for use as drug release and substrates for neuron cell culture. Protein release kinetics was determined by incorporating bovine serum albumin (BSA) into hydrogels during polymerization. To determine if hydrogel incorporation and release affect bioactivity, alkaline phosphatase was incorporated into hydrogels and a released enzyme activity determined using the fluorescence-based ELF-97 assay. Hydrogels were then used to deliver a brain-derived neurotrophic factor (BDNF) from hydrogels polymerized over planar microelectrode arrays (MEAs). Primary hippocampal neurons were cultured on both control and neurotrophin-containing hydrogel-coated MEAs. The effect of released BDNF on neurite length and process arborization was investigated using automated image analysis. An increased spontaneous activity as a response to the released BDNF was recorded from the neurons cultured on the top of hydrogel layers. These results demonstrate that proteins of biological interest can be incorporated into hydrogels to modulate development and function of cultured neural networks. These results also set the stage for development of hydrogel-coated neural prosthetic devices for local delivery of various biologically active molecules.

  15. Brain computer interface learning for systems based on electrocorticography and intracortical microelectrode arrays

    PubMed Central

    Hiremath, Shivayogi V.; Chen, Weidong; Wang, Wei; Foldes, Stephen; Yang, Ying; Tyler-Kabara, Elizabeth C.; Collinger, Jennifer L.; Boninger, Michael L.

    2015-01-01

    A brain-computer interface (BCI) system transforms neural activity into control signals for external devices in real time. A BCI user needs to learn to generate specific cortical activity patterns to control external devices effectively. We call this process BCI learning, and it often requires significant effort and time. Therefore, it is important to study this process and develop novel and efficient approaches to accelerate BCI learning. This article reviews major approaches that have been used for BCI learning, including computer-assisted learning, co-adaptive learning, operant conditioning, and sensory feedback. We focus on BCIs based on electrocorticography and intracortical microelectrode arrays for restoring motor function. This article also explores the possibility of brain modulation techniques in promoting BCI learning, such as electrical cortical stimulation, transcranial magnetic stimulation, and optogenetics. Furthermore, as proposed by recent BCI studies, we suggest that BCI learning is in many ways analogous to motor and cognitive skill learning, and therefore skill learning should be a useful metaphor to model BCI learning. PMID:26113812

  16. Low-Density Neuronal Networks Cultured using Patterned Poly-L-Lysine on Microelectrode Arrays

    PubMed Central

    Jun, Sang Beom; Hynd, Matthew R.; Dowell-Mesfin, Natalie; Smith, Karen L.; Turner, James N.; Shain, William; Kim, Sung June

    2009-01-01

    Synaptic activity recorded from low-density networks of cultured rat hippocampal neurons was monitored using microelectrode arrays (MEAs). Neuronal networks were patterned with poly-L-lysine (PLL) using microcontact printing (µCP). Polydimethysiloxane (PDMS) stamps were fabricated with relief structures resulting in patterns of 2 µm-wide lines for directing process growth and 20 µm-diameter circles for cell soma attachment. These circles were aligned to electrode sites. Different densities of neurons were plated in order to assess the minimal neuron density required for development of an active network. Spontaneous activity was observed at 10–14 days in networks using neuron densities as low as 200 cells/mm2. Immunocytochemistry demonstrated the distribution of dendrites along the lines and the location of foci of the presynaptic protein, synaptophysin, on neuron somas and dendrites. Scanning electron microscopy demonstrated that single fluorescent tracks contained multiple processes. Evoked responses of selected portions of the networks were produced by stimulation of specific electrode sites. In addition, the neuronal excitability of the network was increased by the bath application of high K+ (10–12 mM). Application of DNQX, an AMPA antagonist, blocked all spontaneous activity, suggesting that the activity is excitatory and mediated through glutamate receptors. PMID:17049614

  17. Characterization of Early Cortical Neural Network Development in Multiwell Microelectrode Array Plates

    PubMed Central

    Cotterill, Ellese; Hall, Diana; Wallace, Kathleen; Mundy, William R.; Eglen, Stephen J.; Shafer, Timothy J.

    2016-01-01

    We examined neural network ontogeny using microelectrode array (MEA) recordings made in multiwell MEA (mwMEA) plates over the first 12 days in vitro (DIV). In primary cortical cultures, action potential spiking activity developed rapidly between DIV 5 and 12. Spiking was sporadic and unorganized at early DIV, and became progressively more organized with time, with bursting parameters, synchrony, and network bursting increasing between DIV 5 and 12. We selected 12 features to describe network activity; principal components analysis using these features demonstrated segregation of data by age at both the well and plate levels. Using random forest classifiers and support vector machines, we demonstrated that four features (coefficient of variation [CV] of within-burst interspike interval, CV of interburst interval, network spike rate, and burst rate) could predict the age of each well recording with >65% accuracy. When restricting the classification to a binary decision, accuracy improved to as high as 95%. Further, we present a novel resampling approach to determine the number of wells needed for comparing different treatments. Overall, these results demonstrate that network development on mwMEA plates is similar to development in single-well MEAs. The increased throughput of mwMEAs will facilitate screening drugs, chemicals, or disease states for effects on neurodevelopment. PMID:27028607

  18. In vitro evaluation of pyrethroid-mediated changes on neuronal burst parameters using microelectrode arrays.

    PubMed

    Mohana Krishnan, Baskar; Prakhya, Balakrishna Murthy

    2016-12-01

    Effects of pyrethroids (beta-cyfluthrin, bifenthrin, cypermethrin, deltamethrin, lambda-cyhalothrin, and permethrin) on the burst parameters (mean burst rate [MBR], percent spikes in burst [PSB], mean burst duration [MBD], mean spikes in burst [MSB], mean interspike interval in burst [MISIB], and mean interburst interval [MIBI]) have been investigated using the microelectrode array technique. Rat cortical neuronal networks (between 24 and 35 DIV) were exposed to the five accumulative concentrations of pyrethroids (0.01μM, 0.1μM, 1μM, 10μM, and 100μM) after initially recording the baseline activity. When compared to the baseline, the burst parameter that had undergone the most change (either increase/decrease) at the initial concentrations was MBR, followed by MIBI and PSB. The other burst parameters (MSB, MBD, and MISIB) did not undergo much change (either increase/decrease) by the pyrethroids at the initial concentrations when compared to the baseline. The MBR of all pyrethroids rose at initial concentrations followed by decrease at higher concentrations. A drop in the MIBI accompanied the rise in the MBR. The rank orders of relative potency of pyrethroids on the IC50 of different burst parameters clearly distinguish type-1 pyrethroids (bifenthrin, permethrin) from the type-2 pyrethroids (beta-cyfluthrin, cypermethrin, deltamethrin, lambda-cyhalothrin), with type-2 being more potent. The rank order of relative potency of pyrethroids based on the IC50 of MBR was beta-cyfluthrin>lambda-cyhalothrin>deltamethrin>cypermethrin>bifenthrin>permethrin.

  19. Leptin Counteracts the Hypoxia-Induced Inhibition of Spontaneously Firing Hippocampal Neurons: A Microelectrode Array Study

    PubMed Central

    Gavello, Daniela; Rojo-Ruiz, Jonathan; Marcantoni, Andrea; Franchino, Claudio; Carbone, Emilio; Carabelli, Valentina

    2012-01-01

    Besides regulating energy balance and reducing body-weight, the adipokine leptin has been recently shown to be neuroprotective and antiapoptotic by promoting neuronal survival after excitotoxic and oxidative insults. Here, we investigated the firing properties of mouse hippocampal neurons and the effects of leptin pretreatment on hypoxic damage (2 hours, 3% O2). Experiments were carried out by means of the microelectrode array (MEA) technology, monitoring hippocampal neurons activity from 11 to 18 days in vitro (DIV). Under normoxic conditions, hippocampal neurons were spontaneously firing, either with prevailing isolated and randomly distributed spikes (11 DIV), or with patterns characterized by synchronized bursts (18 DIV). Exposure to hypoxia severely impaired the spontaneous activity of hippocampal neurons, reducing their firing frequency by 54% and 69%, at 11 and 18 DIV respectively, and synchronized their firing activity. Pretreatment with 50 nM leptin reduced the firing frequency of normoxic neurons and contrasted the hypoxia-induced depressive action, either by limiting the firing frequency reduction (at both ages) or by increasing it to 126% (in younger neurons). In order to find out whether leptin exerts its effect by activating large conductance Ca2+-activated K+ channels (BK), as shown on rat hippocampal neurons, we applied the BK channel blocker paxilline (1 µM). Our data show that paxilline reversed the effects of leptin, both on normoxic and hypoxic neurons, suggesting that the adipokine counteracts hypoxia through BK channels activation in mouse hippocampal neurons. PMID:22848520

  20. Brain computer interface learning for systems based on electrocorticography and intracortical microelectrode arrays.

    PubMed

    Hiremath, Shivayogi V; Chen, Weidong; Wang, Wei; Foldes, Stephen; Yang, Ying; Tyler-Kabara, Elizabeth C; Collinger, Jennifer L; Boninger, Michael L

    2015-01-01

    A brain-computer interface (BCI) system transforms neural activity into control signals for external devices in real time. A BCI user needs to learn to generate specific cortical activity patterns to control external devices effectively. We call this process BCI learning, and it often requires significant effort and time. Therefore, it is important to study this process and develop novel and efficient approaches to accelerate BCI learning. This article reviews major approaches that have been used for BCI learning, including computer-assisted learning, co-adaptive learning, operant conditioning, and sensory feedback. We focus on BCIs based on electrocorticography and intracortical microelectrode arrays for restoring motor function. This article also explores the possibility of brain modulation techniques in promoting BCI learning, such as electrical cortical stimulation, transcranial magnetic stimulation, and optogenetics. Furthermore, as proposed by recent BCI studies, we suggest that BCI learning is in many ways analogous to motor and cognitive skill learning, and therefore skill learning should be a useful metaphor to model BCI learning.

  1. High-density stretchable microelectrode arrays: An integrated technology platform for neural and muscular surface interfacing

    NASA Astrophysics Data System (ADS)

    Guo, Liang

    2011-12-01

    Numerous applications in neuroscience research and neural prosthetics, such as retinal prostheses, spinal-cord surface stimulation for prosthetics, electrocorticogram (ECoG) recording for epilepsy detection, etc., involve electrical interaction with soft excitable tissues using a surface stimulation and/or recording approach. These applications require an interface that is able to set up electrical communications with a high throughput between electronics and the excitable tissue and that can dynamically conform to the shape of the soft tissue. Being a compliant and biocompatible material with mechanical impedance close to that of soft tissues, polydimethylsiloxane (PDMS) offers excellent potential as the substrate material for such neural interfaces. However, fabrication of electrical functionalities on PDMS has long been very challenging. This thesis work has successfully overcome many challenges associated with PDMS-based microfabrication and achieved an integrated technology platform for PDMS-based stretchable microelectrode arrays (sMEAs). This platform features a set of technological advances: (1) we have fabricated uniform current density profile microelectrodes as small as 10 mum in diameter; (2) we have patterned high-resolution (feature as small as 10 mum), high-density (pitch as small as 20 mum) thin-film gold interconnects on PDMS substrate; (3) we have developed a multilayer wiring interconnect technology within the PDMS substrate to further boost the achievable integration density of such sMEA; and (4) we have invented a bonding technology---via-bonding---to facilitate high-resolution, high-density integration of the sMEA with integrated circuits (ICs) to form a compact implant. Taken together, this platform provides a high-resolution, high-density integrated system solution for neural and muscular surface interfacing. sMEAs of example designs are evaluated through in vitro and in vivo experimentations on their biocompatibility, surface conformability

  2. Modelling and Analysis of Electrical Potentials Recorded in Microelectrode Arrays (MEAs).

    PubMed

    Ness, Torbjørn V; Chintaluri, Chaitanya; Potworowski, Jan; Łęski, Szymon; Głąbska, Helena; Wójcik, Daniel K; Einevoll, Gaute T

    2015-10-01

    Microelectrode arrays (MEAs), substrate-integrated planar arrays of up to thousands of closely spaced metal electrode contacts, have long been used to record neuronal activity in in vitro brain slices with high spatial and temporal resolution. However, the analysis of the MEA potentials has generally been mainly qualitative. Here we use a biophysical forward-modelling formalism based on the finite element method (FEM) to establish quantitatively accurate links between neural activity in the slice and potentials recorded in the MEA set-up. Then we develop a simpler approach based on the method of images (MoI) from electrostatics, which allows for computation of MEA potentials by simple formulas similar to what is used for homogeneous volume conductors. As we find MoI to give accurate results in most situations of practical interest, including anisotropic slices covered with highly conductive saline and MEA-electrode contacts of sizable physical extensions, a Python software package (ViMEAPy) has been developed to facilitate forward-modelling of MEA potentials generated by biophysically detailed multicompartmental neurons. We apply our scheme to investigate the influence of the MEA set-up on single-neuron spikes as well as on potentials generated by a cortical network comprising more than 3000 model neurons. The generated MEA potentials are substantially affected by both the saline bath covering the brain slice and a (putative) inadvertent saline layer at the interface between the MEA chip and the brain slice. We further explore methods for estimation of current-source density (CSD) from MEA potentials, and find the results to be much less sensitive to the experimental set-up.

  3. Silicon ball grid array chip carrier

    DOEpatents

    Palmer, David W.; Gassman, Richard A.; Chu, Dahwey

    2000-01-01

    A ball-grid-array integrated circuit (IC) chip carrier formed from a silicon substrate is disclosed. The silicon ball-grid-array chip carrier is of particular use with ICs having peripheral bond pads which can be reconfigured to a ball-grid-array. The use of a semiconductor substrate such as silicon for forming the ball-grid-array chip carrier allows the chip carrier to be fabricated on an IC process line with, at least in part, standard IC processes. Additionally, the silicon chip carrier can include components such as transistors, resistors, capacitors, inductors and sensors to form a "smart" chip carrier which can provide added functionality and testability to one or more ICs mounted on the chip carrier. Types of functionality that can be provided on the "smart" chip carrier include boundary-scan cells, built-in test structures, signal conditioning circuitry, power conditioning circuitry, and a reconfiguration capability. The "smart" chip carrier can also be used to form specialized or application-specific ICs (ASICs) from conventional ICs. Types of sensors that can be included on the silicon ball-grid-array chip carrier include temperature sensors, pressure sensors, stress sensors, inertia or acceleration sensors, and/or chemical sensors. These sensors can be fabricated by IC processes and can include microelectromechanical (MEM) devices.

  4. Quantitative Analysis of Rat Dorsal Root Ganglion Neurons Cultured on Microelectrode Arrays Based on Fluorescence Microscopy Image Processing.

    PubMed

    Mari, João Fernando; Saito, José Hiroki; Neves, Amanda Ferreira; Lotufo, Celina Monteiro da Cruz; Destro-Filho, João-Batista; Nicoletti, Maria do Carmo

    2015-12-01

    Microelectrode Arrays (MEA) are devices for long term electrophysiological recording of extracellular spontaneous or evocated activities on in vitro neuron culture. This work proposes and develops a framework for quantitative and morphological analysis of neuron cultures on MEAs, by processing their corresponding images, acquired by fluorescence microscopy. The neurons are segmented from the fluorescence channel images using a combination of segmentation by thresholding, watershed transform, and object classification. The positioning of microelectrodes is obtained from the transmitted light channel images using the circular Hough transform. The proposed method was applied to images of dissociated culture of rat dorsal root ganglion (DRG) neuronal cells. The morphological and topological quantitative analysis carried out produced information regarding the state of culture, such as population count, neuron-to-neuron and neuron-to-microelectrode distances, soma morphologies, neuron sizes, neuron and microelectrode spatial distributions. Most of the analysis of microscopy images taken from neuronal cultures on MEA only consider simple qualitative analysis. Also, the proposed framework aims to standardize the image processing and to compute quantitative useful measures for integrated image-signal studies and further computational simulations. As results show, the implemented microelectrode identification method is robust and so are the implemented neuron segmentation and classification one (with a correct segmentation rate up to 84%). The quantitative information retrieved by the method is highly relevant to assist the integrated signal-image study of recorded electrophysiological signals as well as the physical aspects of the neuron culture on MEA. Although the experiments deal with DRG cell images, cortical and hippocampal cell images could also be processed with small adjustments in the image processing parameter estimation.

  5. Micro-field evoked potentials recorded from the porcine sub-dural cortical surface utilizing a microelectrode array.

    PubMed

    Kitzmiller, Joseph P; Hansford, Derek J; Fortin, Linda D; Obrietan, Karl H; Bergdall, Valerie K; Beversdorf, David Q

    2007-05-15

    A sub-dural surface microelectrode array designed to detect micro-field evoked potentials has been developed. The device is comprised of an array of 350-microm square gold contacts, with bidirectional spacing of 150 microm, contained within a polyimide Kapton material. Cytotoxicity testing suggests that the device is suitable for use with animal and human patients. Implementation of the device in animal studies revealed that reliable evoked potentials could be acquired. Further work will be needed to determine how these micro-field potentials, which demonstrate selectivity for one eye, relate to the distribution of the ocular dominance columns of the occipital cortex.

  6. Develop Silicone Encapsulation Systems for Terrestrial Silicon Solar Arrays

    NASA Technical Reports Server (NTRS)

    1979-01-01

    The results of a study for Task 3 of the Low Cost Solar Array Project, directed toward the development of a cost effective encapsulation system for photovoltaic modules using silicon based materials, are reported. Results of the following are discussed: (1) weather-ometer stressing vs. weathering history of silicon and silicon modified materials; (2) humidity/temperature cycling exposure; (3) exposure at high humidity/high temperature; (4) outdoor exposure stress; (5) thermal cycling stress; and (6) UV screening agents. The plans for the next quarter are outlined.

  7. Low cost silicon solar arrays

    NASA Technical Reports Server (NTRS)

    Ravi, K. V.; Serreze, H. B.; Bates, H. E.; Morrison, A. D.; Jewett, D. N.; Ho, J. C. T.; Schwuttke, G. H.; Ciszek, T. F.; Kran, A.

    1975-01-01

    Continuous growth methodology for silicon solar cell ribbons deals with capillary effects, die effects, thermal effects and crystal shape effects. Emphasis centers on the shape of the meniscus at the ribbon edge as a factor contributing to ribbon quality with respect to defect densities. Structural and electrical characteristics of edge defined, film-fed grown silicon ribbons are elaborated. Ribbon crystal solar cells produce AMO efficiencies of 6 to 10%.

  8. Long-term, multisite, parallel, in-cell recording and stimulation by an array of extracellular microelectrodes.

    PubMed

    Hai, Aviad; Shappir, Joseph; Spira, Micha E

    2010-07-01

    Here we report on the development of a novel neuroelectronic interface consisting of an array of noninvasive gold-mushroom-shaped microelectrodes (gMmicroEs) that practically provide intracellular recordings and stimulation of many individual neurons, while the electrodes maintain an extracellular position. The development of this interface allows simultaneous, multisite, long-term recordings of action potentials and subthreshold potentials with matching quality and signal-to-noise ratio of conventional intracellular sharp glass microelectrodes or patch electrodes. We refer to the novel approach as "in-cell recording and stimulation by extracellular electrodes" to differentiate it from the classical intracellular recording and stimulation methods. This novel technique is expected to revolutionize the analysis of neuronal networks in relations to learning, information storage and can be used to develop novel drugs as well as high fidelity neural prosthetics and brain-machine systems.

  9. Abiotic-biotic characterization of Pt/Ir microelectrode arrays in chronic implants

    PubMed Central

    Prasad, Abhishek; Xue, Qing-Shan; Dieme, Robert; Sankar, Viswanath; Mayrand, Roxanne C.; Nishida, Toshikazu; Streit, Wolfgang J.; Sanchez, Justin C.

    2014-01-01

    Pt/Ir electrodes have been extensively used in neurophysiology research in recent years as they provide a more inert recording surface as compared to tungsten or stainless steel. While floating microelectrode arrays (FMA) consisting of Pt/Ir electrodes are an option for neuroprosthetic applications, long-term in vivo functional performance characterization of these FMAs is lacking. In this study, we have performed comprehensive abiotic-biotic characterization of Pt/Ir arrays in 12 rats with implant periods ranging from 1 week up to 6 months. Each of the FMAs consisted of 16-channel, 1.5 mm long, and 75 μm diameter microwires with tapered tips that were implanted into the somatosensory cortex. Abiotic characterization included (1) pre-implant and post-explant scanning electron microscopy (SEM) to study recording site changes, insulation delamination and cracking, and (2) chronic in vivo electrode impedance spectroscopy. Biotic characterization included study of microglial responses using a panel of antibodies, such as Iba1, ED1, and anti-ferritin, the latter being indicative of blood-brain barrier (BBB) disruption. Significant structural variation was observed pre-implantation among the arrays in the form of irregular insulation, cracks in insulation/recording surface, and insulation delamination. We observed delamination and cracking of insulation in almost all electrodes post-implantation. These changes altered the electrochemical surface area of the electrodes and resulted in declining impedance over the long-term due to formation of electrical leakage pathways. In general, the decline in impedance corresponded with poor electrode functional performance, which was quantified via electrode yield. Our abiotic results suggest that manufacturing variability and insulation material as an important factor contributing to electrode failure. Biotic results show that electrode performance was not correlated with microglial activation (neuroinflammation) as we were able

  10. The use of microelectrode array (MEA) to study rat peritoneal mast cell activation.

    PubMed

    Yeung, Chi-Kong; Law, Jessica Ka-Yan; Sam, Sze-Wing; Ingebrandt, Sven; Lau, Hang-Yung Alaster; Rudd, John Anthony; Chan, Mansun

    2008-06-01

    We performed this study to demonstrate the applicability of the microelectrode array (MEA) to study electrophysiological changes of rat peritoneal mast cells in the presence of compound 48/80 under normal, Ca(2+)-free, Ca(2+)-free with EDTA, and Cl(-)-free conditions. The use of high extracellular K(+) (KCl, 150 mM), charybdotoxin (ChTX, 100 nM), and Cl(-)-free containing ChTX buffers verified that the hyperpolarizing signal was due to the activation of mainly K(+) and, to a lesser extent, Cl(-) channels. Compound 48/80 concentration-dependently shortened the latent periods (the onset of response) and increased both the spatial (the K(+) and Cl(-) hyperpolarizing field potentials, HFP) and temporal measurements (the duration of response). Ca(2+)-free buffer had no effect on the latent period of compound 48/80 but increased the HFP at high concentrations. The latent period increased while the HFP diminished when cells were equilibrated in Ca(2+)-free buffer containing EDTA. Durations of the HFP were generally longer when cells were in either Ca(2+)-free or Ca(2+)-free containing EDTA buffers than when cells were in normal buffer. The EC(50) values confirmed that effects were only affected in Ca(2+)-free buffer containing EDTA but not in Ca(2+)-free or Cl(-)-free buffers, further reinforcing the hypothesis that the presence of Ca(2+) is not essential to the action of compound 48/80. The present study is the first application of MEA to study rat peritoneal mast cells, and our results indicate that it could be of value in future pharmacological research on other non-excitable cells.

  11. Microelectrode array (MEA) platform as a sensitive tool to detect and evaluate Ostreopsis cf. ovata toxicity.

    PubMed

    Alloisio, Susanna; Giussani, Valentina; Nobile, Mario; Chiantore, Mariachiara; Novellino, Antonio

    2016-05-01

    In the last decade, the occurrence of harmful dinoflagellate blooms of the genus Ostreopsis has increased both in frequency and in geographic distribution with adverse impacts on public health and the economy. Ostreopsis species are producers of palytoxin-like toxins (putative palytoxin and ovatoxins) which are among the most potent natural non-protein compounds known to date, exhibiting extreme toxicity in mammals, including humans. Most existing toxicological data are derived from in vivo mouse assay and are related to acute effects of pure palytoxin, without considering that the toxicity mechanism of dinoflagellates can be dependent on the varying composition of complex biotoxins mixture and on the presence of cellular components. In this study, in vitro neuronal networks coupled to microelectrode array (MEA)-based system are proposed, for the first time, as sensitive biosensors for the evaluation of marine alga toxicity on mammalian cells. Toxic effect was investigated by testing three different treatments of laboratory cultured Ostreopsis cf. ovata cells: filtered and re-suspended algal cells; filtered, re-suspended and sonicated algal cells; conditioned growth medium devoid of algal cells. The great sensitivity of this system revealed the mixture of PTLX-complex analogues naturally released in the growth medium and the different potency of the three treatments to inhibit the neuronal network spontaneous electrical activity. Moreover, by means of the multiparametric analysis of neuronal network activity, the approach revealed a different toxicity mechanism of the cellular component compared to the algal conditioned growth medium, highlighting the potential active role of the first treatment.

  12. Real-time monitoring of extracellular adenosine using enzyme-linked microelectrode arrays.

    PubMed

    Hinzman, Jason M; Gibson, Justin L; Tackla, Ryan D; Costello, Mark S; Burmeister, Jason J; Quintero, Jorge E; Gerhardt, Greg A; Hartings, Jed A

    2015-12-15

    Throughout the central nervous system extracellular adenosine serves important neuroprotective and neuromodulatory functions. However, current understanding of the in vivo regulation and effects of adenosine is limited by the spatial and temporal resolution of available measurement techniques. Here, we describe an enzyme-linked microelectrode array (MEA) with high spatial (7500 µm(2)) and temporal (4 Hz) resolution that can selectively measure extracellular adenosine through the use of self-referenced coating scheme that accounts for interfering substances and the enzymatic breakdown products of adenosine. In vitro, the MEAs selectively measured adenosine in a linear fashion (r(2)=0.98±0.01, concentration range=0-15 µM, limit of detection =0.96±0.5 µM). In vivo the limit of detection was 0.04±0.02 µM, which permitted real-time monitoring of the basal extracellular concentration in rat cerebral cortex (4.3±1.5 µM). Local cortical injection of adenosine through a micropipette produced dose-dependent transient increases in the measured extracellular concentration (200 nL: 6.8±1.8 µM; 400 nL: 19.4±5.3 µM) [P<0.001]. Lastly, local injection of dipyridamole, which inhibits transport of adenosine through equilibrative nucleoside transporter, raised the measured extracellular concentration of adenosine by 120% (5.6→12.3 µM) [P<0.001]. These studies demonstrate that MEAs can selectively measure adenosine on temporal and spatial scales relevant to adenosine signaling and regulation in normal and pathologic states.

  13. Chronic intracortical microelectrode arrays induce non-uniform, depth-related tissue responses

    NASA Astrophysics Data System (ADS)

    Woolley, Andrew J.; Desai, Himanshi A.; Otto, Kevin J.

    2013-04-01

    Objective. Brain-implanted microelectrode arrays show promise as future clinical devices. However, biological responses to various designs, compositions and locations of these implants have not been fully characterized, and may impact the long-term functionality of these devices. In order to improve our understanding of the tissue conditions at the interface of chronic brain-implanted microdevices, we proposed utilizing advanced histology and microscopy techniques to image implanted devices and surrounding tissue intact within brain slices. We then proposed utilizing these methods to examine whether depth within the cerebral cortex affected tissue conditions around implants. Approach. Histological data was collected from rodent brain slices containing intact, intracortical microdevices four weeks after implantation surgery. Thick tissue sections containing the chronic implants were processed with fluorescent antibody labels, and imaged in an optical clearing solution using laser confocal microscopy. Main Results. Tissue surrounding microdevices exhibited two major depth-related phenomena: a non-uniform microglial coating along the device length and a dense mass of cells surrounding the implant in cerebral cortical layers I and II. Detailed views of the monocyte-derived immune cells improve our understanding of the close and complex association that immune cells have with chronic brain implants, and illuminated a possible relationship between cortical depth and the intensity of a chronic monocyte response around penetrating microdevices. The dense mass of cells contained vimentin, a protein not typically expressed highly in CNS cells, evidence that non-CNS cells likely descended down the face of the penetrating devices from the pial surface. Significance. Image data of highly non-uniform and depth-dependent biological responses along a device provides novel insight into the complexity of the tissue response to penetrating brain-implanted microdevices. The presented

  14. Nanophotonic ion production from silicon microcolumn arrays.

    PubMed

    Walker, Bennett N; Razunguzwa, Trust; Powell, Matthew; Knochenmuss, Richard; Vertes, Akos

    2009-01-01

    Nanoantennas for ions: Silicon microcolumn arrays harvest light from a laser pulse to produce ions. The system behaves like a quasi-periodic antenna array with ion yields that show profound dependence on the plane of polarization and the angle of incidence of the laser beam. Photonic ion sources promise to enable enhanced control of ion production on a micro- and nanometer scale and direct integration with miniaturized analytical devices.

  15. Brain machine interfaces combining microelectrode arrays with nanostructured optical biochemical sensors

    NASA Astrophysics Data System (ADS)

    Hajj-Hassan, Mohamad; Gonzalez, Timothy; Ghafer-Zadeh, Ebrahim; Chodavarapu, Vamsy; Musallam, Sam; Andrews, Mark

    2009-02-01

    Neural microelectrodes are an important component of neural prosthetic systems which assist paralyzed patients by allowing them to operate computers or robots using their neural activity. These microelectrodes are also used in clinical settings to localize the locus of seizure initiation in epilepsy or to stimulate sub-cortical structures in patients with Parkinson's disease. In neural prosthetic systems, implanted microelectrodes record the electrical potential generated by specific thoughts and relay the signals to algorithms trained to interpret these thoughts. In this paper, we describe novel elongated multi-site neural electrodes that can record electrical signals and specific neural biomarkers and that can reach depths greater than 8mm in the sulcus of non-human primates (monkeys). We hypothesize that additional signals recorded by the multimodal probes will increase the information yield when compared to standard probes that record just electropotentials. We describe integration of optical biochemical sensors with neural microelectrodes. The sensors are made using sol-gel derived xerogel thin films that encapsulate specific biomarker responsive luminophores in their nanostructured pores. The desired neural biomarkers are O2, pH, K+, and Na+ ions. As a prototype, we demonstrate direct-write patterning to create oxygen-responsive xerogel waveguide structures on the neural microelectrodes. The recording of neural biomarkers along with electrical activity could help the development of intelligent and more userfriendly neural prosthesis/brain machine interfaces as well as aid in providing answers to complex brain diseases and disorders.

  16. Needle-type environmental microsensors: design, construction and uses of microelectrodes and multi-analyte MEMS sensor arrays

    NASA Astrophysics Data System (ADS)

    Lee, Woo Hyoung; Lee, Jin-Hwan; Choi, Woo-Hyuck; Hosni, Ahmed A.; Papautsky, Ian; Bishop, Paul L.

    2011-04-01

    The development of environmental microsensor techniques is a revolutionary advance in the measurement of both absolute levels and changes in chemical species in the field of environmental engineered and natural systems. The tiny tip (5-15 µm diameter) of microsensors makes them very attractive experimental tools for direct measurements of the chemical species of interest inside biological samples (e.g., biofilm, flocs). Microelectrodes fabricated from pulled micropipettes (e.g., dissolved oxygen, oxidation-reduction potential, ion-selective microelectrode) have contributed to greater understanding of biological mechanisms for decades using microscopic monitoring, and currently microelectromechanical system (MEMS) microfabrication technologies are being successfully applied to fabricate multi-analyte sensor systems for in situ monitoring. This review focuses on needle-type environmental microsensor technology, including microelectrodes and multi-analyte MEMS sensor arrays. Design, construction and applications to biofilm research of these sensors are described. Practical methods for biofilm microprofile measurements are presented and several in situ applications for a biofilm study are highlighted. Ultimately, the developed needle-type microsensors combined with molecular biotechnology (such as microscopic observation with fluorescent probes) show the tremendous promise of micro-environmental sensor technology.

  17. Low cost silicon solar cell array

    NASA Technical Reports Server (NTRS)

    Bartels, F. T. C.

    1974-01-01

    The technological options available for producing low cost silicon solar cell arrays were examined. A project value of approximately $250/sq m and $2/watt is projected, based on mass production capacity demand. Recommendations are included for the most promising cost reduction options.

  18. Heterogeneous distribution of exocytotic microdomains in adrenal chromaffin cells resolved by high-density diamond ultra-microelectrode arrays

    PubMed Central

    Gosso, Sara; Turturici, Marco; Franchino, Claudio; Colombo, Elisabetta; Pasquarelli, Alberto; Carbone, Emilio; Carabelli, Valentina

    2014-01-01

    Here we describe the ability of a high-density diamond microelectrode array targeted to resolve multi-site detection of fast exocytotic events from single cells. The array consists of nine boron-doped nanocrystalline diamond ultra-microelectrodes (9-Ch NCD-UMEA) radially distributed within a circular area of the dimensions of a single cell. The device can be operated in voltammetric or chronoamperometric configuration. Sensitivity to catecholamines, tested by dose–response calibrations, set the lowest detectable concentration of adrenaline to ∼5 μm. Catecholamine release from bovine or mouse chromaffin cells could be triggered by electrical stimulation or external KCl-enriched solutions. Spikes detected from the cell apex using carbon fibre microelectrodes showed an excellent correspondence with events measured at the bottom of the cell by the 9-Ch NCD-UMEA, confirming the ability of the array to resolve single quantal secretory events. Subcellular localization of exocytosis was provided by assigning each quantal event to one of the nine channels based on its location. The resulting mapping highlights the heterogeneous distribution of secretory activity in cell microdomains of 12–27 μm2. In bovine chromaffin cells, secretion was highly heterogeneous with zones of high and medium activity in 54% of the cell surface and zones of low or no activity in the remainder. The ‘non-active’ (‘silent’) zones covered 24% of the total and persisted for 6–8 min, indicating stable location. The 9-Ch NCD-UMEA therefore appears suitable for investigating the microdomain organization of neurosecretion with high spatial resolution. PMID:24879870

  19. Fluid flow study of an AC electrothermal micropump consisting of multiple arrays of microelectrodes for biofluidic applications

    NASA Astrophysics Data System (ADS)

    Salari, Alinaghi; Dalton, Colin

    2015-03-01

    Electrokinetics has many applications in a wide range of areas, such as lab-on-a-chip and biomedical microdevices. The electrothermal effect has been used for biofluid delivery systems since it has high pumping efficiency for high conductive liquids (>0.1 S/m) compared to other electrokinetic techniques such as electroosmosis. AC electrothermal (ACET) micropumps are based on the temperature gradient caused by Joule heating or an external heat source, which generates permittivity and conductivity gradients in the bulk of the liquid. When the liquid is subjected to an electric field, the ACET force is created. Electrode geometry significantly affects the electric field distribution, which can yield stronger ACET forces. Previously electrode dimension optimization has been performed for a single-array coplanar asymmetric configuration in order to obtain maximum ACET velocities. In this paper we expand the study to other governing parameters in a multiple-row microelectrode array configuration consisting of microelectrodes placed on top, bottom, and/or side walls of a microchannel. The studied parameters are the substrate material and thickness, ambient temperature, fluid viscosity, and actuation frequency. Electrode dimensions remain constant during the study (120 μm wide and 20 μm thin electrodes, 20 μm gap). The study is performed using finite element analysis software for one pair of microelectrodes on each array with periodic boundary conditions. The simulation data is then compared with experimental data for a single combination of the aforementioned parameters. The results show that the effect of these parameters on ACET flow can be significant.

  20. Using Arrays of Microelectrodes Implanted in Residual Peripheral Nerves to Provide Dextrous Control of, and Modulated Sensory Feedback from, a Hand Prosthesis

    DTIC Science & Technology

    2015-10-01

    Design and drawings of micro-electrode arrays complete. 2 • Measure impedances on all electrodes in each array prior to sterilization, and if...allow them to compliantly move with the peripheral nerves and resist mechanical damage. Figure 1 – CAD drawings of the poly-LIFE. Top panel: A...week of implantation due to the array/ wire being crushed/broken by the patient likely during performance of their job. The second array failure

  1. Junction-side illuminated silicon detector arrays

    DOEpatents

    Iwanczyk, Jan S.; Patt, Bradley E.; Tull, Carolyn

    2004-03-30

    A junction-side illuminated detector array of pixelated detectors is constructed on a silicon wafer. A junction contact on the front-side may cover the whole detector array, and may be used as an entrance window for light, x-ray, gamma ray and/or other particles. The back-side has an array of individual ohmic contact pixels. Each of the ohmic contact pixels on the back-side may be surrounded by a grid or a ring of junction separation implants. Effective pixel size may be changed by separately biasing different sections of the grid. A scintillator may be coupled directly to the entrance window while readout electronics may be coupled directly to the ohmic contact pixels. The detector array may be used as a radiation hardened detector for high-energy physics research or as avalanche imaging arrays.

  2. Spectral Entropy Based Neuronal Network Synchronization Analysis Based on Microelectrode Array Measurements

    PubMed Central

    Kapucu, Fikret E.; Välkki, Inkeri; Mikkonen, Jarno E.; Leone, Chiara; Lenk, Kerstin; Tanskanen, Jarno M. A.; Hyttinen, Jari A. K.

    2016-01-01

    Synchrony and asynchrony are essential aspects of the functioning of interconnected neuronal cells and networks. New information on neuronal synchronization can be expected to aid in understanding these systems. Synchronization provides insight in the functional connectivity and the spatial distribution of the information processing in the networks. Synchronization is generally studied with time domain analysis of neuronal events, or using direct frequency spectrum analysis, e.g., in specific frequency bands. However, these methods have their pitfalls. Thus, we have previously proposed a method to analyze temporal changes in the complexity of the frequency of signals originating from different network regions. The method is based on the correlation of time varying spectral entropies (SEs). SE assesses the regularity, or complexity, of a time series by quantifying the uniformity of the frequency spectrum distribution. It has been previously employed, e.g., in electroencephalogram analysis. Here, we revisit our correlated spectral entropy method (CorSE), providing evidence of its justification, usability, and benefits. Here, CorSE is assessed with simulations and in vitro microelectrode array (MEA) data. CorSE is first demonstrated with a specifically tailored toy simulation to illustrate how it can identify synchronized populations. To provide a form of validation, the method was tested with simulated data from integrate-and-fire model based computational neuronal networks. To demonstrate the analysis of real data, CorSE was applied on in vitro MEA data measured from rat cortical cell cultures, and the results were compared with three known event based synchronization measures. Finally, we show the usability by tracking the development of networks in dissociated mouse cortical cell cultures. The results show that temporal correlations in frequency spectrum distributions reflect the network relations of neuronal populations. In the simulated data, CorSE unraveled the

  3. Neurotoxicity screening of (illicit) drugs using novel methods for analysis of microelectrode array (MEA) recordings.

    PubMed

    Hondebrink, L; Verboven, A H A; Drega, W S; Schmeink, S; de Groot, M W G D M; van Kleef, R G D M; Wijnolts, F M J; de Groot, A; Meulenbelt, J; Westerink, R H S

    2016-07-01

    Annual prevalence of the use of common illicit drugs and new psychoactive substances (NPS) is high, despite the often limited knowledge on the health risks of these substances. Recently, cortical cultures grown on multi-well microelectrode arrays (mwMEAs) have been used for neurotoxicity screening of chemicals, pharmaceuticals, and toxins with a high sensitivity and specificity. However, the use of mwMEAs to investigate the effects of illicit drugs on neuronal activity is largely unexplored. We therefore first characterised the cortical cultures using immunocytochemistry and show the presence of astrocytes, glutamatergic and GABAergic neurons. Neuronal activity is concentration-dependently affected following exposure to six neurotransmitters (glutamate, GABA, serotonin, dopamine, acetylcholine and nicotine). Most neurotransmitters inhibit neuronal activity, although glutamate and acetylcholine transiently increase activity at specific concentrations. These transient effects are not detected when activity is determined during the entire 30min exposure window, potentially resulting in false-negative results. As expected, exposure to the GABAA-receptor antagonist bicuculline increases neuronal activity. Exposure to a positive allosteric modulator of the GABAA-receptor (diazepam) or to glutamate receptor antagonists (CNQX and MK-801) reduces neuronal activity. Further, we demonstrate that exposure to common drugs (3,4-methylenedioxymethamphetamine (MDMA) and amphetamine) and NPS (1-(3-chlorophenyl)piperazine (mCPP), 4-fluoroamphetamine (4-FA) and methoxetamine (MXE)) decreases neuronal activity. MXE most potently inhibits neuronal activity with an IC50 of 0.5μM, whereas 4-FA is least potent with an IC50 of 113μM. Our data demonstrate the importance of analysing neuronal activity within different time windows during exposure to prevent false-negative results. We also show that cortical cultures grown on mwMEAs can successfully be applied to investigate the effects of

  4. Characterizing the Material Properties of Polymer-Based Microelectrode Arrays for Retinal Prosthesis

    SciTech Connect

    Park, Christina Soyeun

    2003-06-01

    The Retinal Prosthesis project is a three year project conducted in part at the Lawrence Livermore National Laboratory and funded by the Department of Energy to create an epiretinal microelectrode array for stimulating retinal cells. The implant must be flexible to conform to the retina, robust to sustain handling during fabrication and implantation, and biocompatible to withstand physiological conditions within the eye. Using poly(dimethyl siloxane) (PDMS), LLNL aims to use microfabrication techniques to increase the number of electrodes and integrate electronics. After the initial designs were fabricated and tested in acute implantation, it became obvious that there was a need to characterize and understand the mechanical and electrical properties of these new structures. This knowledge would be imperative in gaining credibility for polymer microfabrication and optimizing the designs. Thin composite microfabricated devices are challenging to characterize because they are difficult to handle, and exhibit non-linear, viscoelastic, and anisotropic properties. The objective of this research is to device experiments and protocols, develop an analytical model to represent the composite behavior, design and fabricate test structures, and conduct experimental testing to determine the mechanical and electrical properties of PDMS-metal composites. Previous uniaxial stretch tests show an average of 7% strain before failure on resistive heaters of similar dimensions deposited on PDMS. Lack of background information and questionable human accuracy demands a more sophisticated and thorough testing method. An Instron tensile testing machine was set up to interface with a digital multiplexor and computer interface to simultaneously record and graph position, load, and resistance across devices. With a compliant load cell for testing polymers and electrical interconnect grips designed and fabricated to interface the sample to the electronics, real-time resistance measurements

  5. Creation of defined single cell resolution neuronal circuits on microelectrode arrays

    NASA Astrophysics Data System (ADS)

    Pirlo, Russell Kirk

    2009-12-01

    The way cell-cell organization of neuronal networks influences activity and facilitates function is not well understood. Microelectrode arrays (MEAs) and advancing cell patterning technologies have enabled access to and control of in vitro neuronal networks spawning much new research in neuroscience and neuroengineering. We propose that small, simple networks of neurons with defined circuitry may serve as valuable research models where every connection can be analyzed, controlled and manipulated. Towards the goal of creating such neuronal networks we have applied microfabricated elastomeric membranes, surface modification and our unique laser cell patterning system to create defined neuronal circuits with single-cell precision on MEAs. Definition of synaptic connectivity was imposed by the 3D physical constraints of polydimethylsiloxane elastomeric membranes. The membranes had 20mum clear-through holes and 2-3mum deep channels which when applied to the surface of the MEA formed microwells to confine neurons to electrodes connected via shallow tunnels to direct neurite outgrowth. Tapering and turning of channels was used to influence neurite polarity. Biocompatibility of the membranes was increased by vacuum baking, oligomer extraction, and autoclaving. Membranes were bound to the MEA by oxygen plasma treatment and heated pressure. The MEA/membrane surface was treated with oxygen plasma, poly-D-lysine and laminin to improve neuron attachment, survival and neurite outgrowth. Prior to cell patterning the outer edge of culture area was seeded with 5x10 5 cells per cm and incubated for 2 days. Single embryonic day 7 chick forebrain neurons were then patterned into the microwells and onto the electrodes using our laser cell patterning system. Patterned neurons successfully attached to and were confined to the electrodes. Neurites extended through the interconnecting channels and connected with adjacent neurons. These results demonstrate that neuronal circuits can be

  6. Diamond coated silicon field emitter array

    SciTech Connect

    S. Albin; W. Fu; A. Varghese; A. C. Lavarias; G. R. Myneni

    1999-07-01

    Diamond coated silicon tip arrays, with and without a self-aligned gate, were fabricated, and current-voltage characteristics of 400 tips were measured. Diamond films were grown uniformly on Si tips using microwave plasma after nucleation with 10 nm diamond suspension and substrate bias. An emission current of 57 ?A was obtained at 5 V from the ungated array tips separated from an anode at 2 ?m. In the case of the gated arrays with 1.5 ?m aperture, an emission current of 3.4 ?A was measured at a gate voltage of 80 V for an anode separation of 200 ?m. The turn-on voltages for these two types of devices were 0.2 and 40 V, respectively. Diamond coated Si tip arrays have potential applications in field emission based low voltage vacuum electronic devices and microsensors.

  7. In Vivo Neural Recording and Electrochemical Performance of Microelectrode Arrays Modified by Rough-Surfaced AuPt Alloy Nanoparticles with Nanoporosity

    PubMed Central

    Zhao, Zongya; Gong, Ruxue; Zheng, Liang; Wang, Jue

    2016-01-01

    In order to reduce the impedance and improve in vivo neural recording performance of our developed Michigan type silicon electrodes, rough-surfaced AuPt alloy nanoparticles with nanoporosity were deposited on gold microelectrode sites through electro-co-deposition of Au-Pt-Cu alloy nanoparticles, followed by chemical dealloying Cu. The AuPt alloy nanoparticles modified gold microelectrode sites were characterized by scanning electron microscopy (SEM), electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV) and in vivo neural recording experiment. The SEM images showed that the prepared AuPt alloy nanoparticles exhibited cauliflower-like shapes and possessed very rough surfaces with many different sizes of pores. Average impedance of rough-surfaced AuPt alloy nanoparticles modified sites was 0.23 MΩ at 1 kHz, which was only 4.7% of that of bare gold microelectrode sites (4.9 MΩ), and corresponding in vitro background noise in the range of 1 Hz to 7500 Hz decreased to 7.5 μVrms from 34.1 μVrms at bare gold microelectrode sites. Spontaneous spike signal recording was used to evaluate in vivo neural recording performance of modified microelectrode sites, and results showed that rough-surfaced AuPt alloy nanoparticles modified microelectrode sites exhibited higher average spike signal-to-noise ratio (SNR) of 4.8 in lateral globus pallidus (GPe) due to lower background noise compared to control microelectrodes. Electro-co-deposition of Au-Pt-Cu alloy nanoparticles combined with chemical dealloying Cu was a convenient way for increasing the effective surface area of microelectrode sites, which could reduce electrode impedance and improve the quality of in vivo spike signal recording. PMID:27827893

  8. Biocompatibility of subretinal parylene-based Ti/Pt microelectrode array in rabbit for further artificial vision studies.

    PubMed

    Yu, Weihong; Wang, Xuqian; Zhao, Chan; Yang, Zhikun; Dai, Rongping; Dong, Fangtian

    2009-03-27

    To evaluate the biocompatibility of subretinal implanted parylene-based Ti/Pt microelectrode arrays (MEA). Eyes were enucleated 3 months after MEAs were implanted into the subretinal space of rabbits. Morphological changes of the retinas were investigated by H&E staining. Immunohistochemical staining for glial fibrillary acidic protein and opsin were performed to evaluate changes in Muller cells and photoreceptors in the retinas. Retina tissue around the array remained intact. Photoreceptor degeneration and glial cell activation were observed in the retina overlaying the MEA implant. However, the cells in the inner retinal layers were preserved. Photoreceptor degeneration and glial cell activation at the MEA-retina interface are expected to be a normal reaction to implantation. Material used in this experiment has good biocompatibility within the subretinal environment and is expected to be promising in the further retinal prosthesis studies.

  9. Integrated Arrays on Silicon at Terahertz Frequencies

    NASA Technical Reports Server (NTRS)

    Chattopadhayay, Goutam; Lee, Choonsup; Jung, Cecil; Lin, Robert; Peralta, Alessandro; Mehdi, Imran; Llombert, Nuria; Thomas, Bertrand

    2011-01-01

    In this paper we explore various receiver font-end and antenna architecture for use in integrated arrays at terahertz frequencies. Development of wafer-level integrated terahertz receiver front-end by using advanced semiconductor fabrication technologies and use of novel integrated antennas with silicon micromachining are reported. We report novel stacking of micromachined silicon wafers which allows for the 3-dimensional integration of various terahertz receiver components in extremely small packages which easily leads to the development of 2- dimensioanl multi-pixel receiver front-ends in the terahertz frequency range. We also report an integrated micro-lens antenna that goes with the silicon micro-machined front-end. The micro-lens antenna is fed by a waveguide that excites a silicon lens antenna through a leaky-wave or electromagnetic band gap (EBG) resonant cavity. We utilized advanced semiconductor nanofabrication techniques to design, fabricate, and demonstrate a super-compact, low-mass submillimeter-wave heterodyne frontend. When the micro-lens antenna is integrated with the receiver front-end we will be able to assemble integrated heterodyne array receivers for various applications such as multi-pixel high resolution spectrometer and imaging radar at terahertz frequencies.

  10. Characterization of ToxCast Phase II compounds disruption of spontaneous network activity in cortical networks grown on multi-well microelectrode array (mwMEA) plates.

    EPA Science Inventory

    The development of multi-well microelectrode array (mwMEA) systems has increased in vitro screening throughput making them an effective method to screen and prioritize large sets of compounds for potential neurotoxicity. In the present experiments, a multiplexed approach was used...

  11. Surface properties of pulsed laser deposited Ir, Rh, and Ir 0.9Rh 0.1 thin films for use as microelectrode arrays in electroanalytical heavy metal trace sensors

    NASA Astrophysics Data System (ADS)

    Le Drogoff, B.; El Khakani, M. A.; Silva, P. R. M.; Chaker, M.; Ross, G. G.

    1999-11-01

    Pulsed laser deposition (PLD) of iridium, rhodium, and Ir 0.9Rh 0.1 thin films onto a-SiC:H-coated silicon substrates for use in heavy metal sensors has been achieved by ablating iridium and/or rhodium targets with a KrF excimer laser. The deposited films are polycrystalline and exhibited very smooth surfaces with an average roughness value ( Ra) of ˜1 nm. The wettability by mercury of their surface was investigated by means of the contact angle measurement technique, and compared to that of Ag and Pt films. The PLD films (whether Ir, Rh, or Ir 0.9Rh 0.1) were found to present an almost identical Hg-wetting behavior, which is characterized by a high static contact angle of 132±2°. Moreover, in contrast to the cases of Pt or Ag films, where amalgamation with Hg rapidly occurs during the contact angle measurements, no evident interaction of Hg with the surface of the PLD films was observed. Microelectrode arrays of each of the three films (Ir, Rh and Ir 0.9Rh 0.1) were fabricated and used as a conducting base onto which Hg microdrops are electroplated. Reproducible and uniform Hg deposits on the microelectrode arrays were obtained. The electroanalytical performance of these Hg-electroplated microelectrode arrays based sensors was then evaluated by means of Square Wave Anodic Stripping Voltammetry (SWASV), in synthetic solutions containing Zn, Cd and Pb ion traces. Over a concentration range as wide as 0.2-20 ppb, the detected signals are found to exhibit a strong linear correlation with ion concentration. For a preconcentration time of only 5 min, detection limits as low as 0.2 ppb for both Cd and Pb, and 0.5 ppb for Zn were achieved.

  12. Precaution for volume conduction in rodent cortical electroencephalography using high-density polyimide-based microelectrode arrays on the skull.

    PubMed

    Stienen, P J; Venzi, M; Poppendieck, W; Hoffmann, K P; Åberg, E

    2016-04-01

    In humans, significant progress has been made to link spatial changes in electroencephalographic (EEG) spectral density, connectivity strength, and phase-amplitude modulation to neurological, physiological, and psychological correlates. In contrast, standard rodent EEG techniques employ only few electrodes, which results in poor spatial resolution. Recently, a technique was developed to overcome this limitation in mice. This technique was based on a polyimide-based microelectrode (PBM) array applied on the mouse skull, maintaining a significant number of electrodes with consistent contact, electrode impedance, and mechanical stability. The present study built on this technique by extending it to rats. Therefore, a similar PBM array, but adapted to rats, was designed and fabricated. In addition, this array was connected to a wireless EEG headstage, allowing recording in untethered, freely moving rats. The advantage of a high-density array relies on the assumption that the signal recorded from the different electrodes is generated from distinct sources, i.e., not volume-conducted. Therefore, the utility and validity of the array were evaluated by determining the level of synchrony between channels due to true synchrony or volume conduction during basal vigilance states and following a subanesthetic dose of ketamine. Although the PBM array allowed recording with high signal quality, under both drug and drug-free conditions, high synchronization existed due to volume conduction between the electrodes even in the higher spectral frequency range. Discrimination existed only between frontally and centrally/distally grouped electrode pairs. Therefore, caution should be used in interpreting spatial data obtained from high-density PBM arrays in rodents.

  13. Micro-flow Immunosensor Based on Thin-film Interdigitated Gold Array Microelectrodes for Cancer Biomarker Detection.

    PubMed

    Ravalli, Andrea; Lozzi, Luca; Marrazza, Giovanna

    2016-01-01

    In this paper, we reported the development of a micro-flow label-free impedimetric biosensor based on the use of thin-film interdigitated gold array microelectrodes (IDA) for the detection of carbohydrate antigen 125 (CA125). The immunosensor is developed through the electropolymerization of anthranilic acid (AA) on the surface of IDA electrodes followed by the covalent attachment of anti-CA125 monoclonal antibody. CA125 protein affinity reaction was then evaluated by means of electrochemical impedance spectroscopy (EIS). The sensor was characterized by electrochemical techniques and scanning electron microscopy (SEM). Using the optimized experimental conditions, the developed immunosensor showed a good analytical performance for CA125 detection from 0 to 100 U/mL with estimated limit of detection (LOD = 3Sblank/Slope) of 7 U/mL.

  14. A flexible and implantable microelectrode arrays using high-temperature grown vertical carbon nanotubes and a biocompatible polymer substrate

    NASA Astrophysics Data System (ADS)

    Yi, Wenwen; Chen, Chaoyang; Feng, Zhaoying; Xu, Yong; Zhou, Chengpeng; Masurkar, Nirul; Cavanaugh, John; Ming-Cheng Cheng, Mark

    2015-03-01

    This paper presents a novel microelectrode arrays using high-temperature grown vertically aligned carbon nanotubes (CNTs) integrated on a flexible and biocompatible parylene substrate. A simple microfabrication process is proposed to unite the high quality vertical CNTs grown at high temperature with the heat sensitive parylene substrate in a highly controllable manner. Briefly, the CNTs electrode is encapsulated by two layers of parylene and the device is released using xenon difluoride (XeF2). The process is compatible with wafer-scale post complementary metal oxide semiconductor integration. Lower impedance and larger interfacial capacitance have been demonstrated using CNTs compared to a Pt electrode. The flexible CNT electrodes have been utilized for extracellular neuronal recording and stimulation in rats. The signal-to-noise ratio of the device is about 12.5. The threshold voltage for initiating action potential is about 0.5 V.

  15. Multiple Single-Unit Long-Term Tracking on Organotypic Hippocampal Slices Using High-Density Microelectrode Arrays

    PubMed Central

    Gong, Wei; Senčar, Jure; Bakkum, Douglas J.; Jäckel, David; Obien, Marie Engelene J.; Radivojevic, Milos; Hierlemann, Andreas R.

    2016-01-01

    A novel system to cultivate and record from organotypic brain slices directly on high-density microelectrode arrays (HD-MEA) was developed. This system allows for continuous recording of electrical activity of specific individual neurons at high spatial resolution while monitoring at the same time, neuronal network activity. For the first time, the electrical activity patterns of single neurons and the corresponding neuronal network in an organotypic hippocampal slice culture were studied during several consecutive weeks at daily intervals. An unsupervised iterative spike-sorting algorithm, based on PCA and k-means clustering, was developed to assign the activities to the single units. Spike-triggered average extracellular waveforms of an action potential recorded across neighboring electrodes, termed “footprints” of single-units were generated and tracked over weeks. The developed system offers the potential to study chronic impacts of drugs or genetic modifications on individual neurons in slice preparations over extended times. PMID:27920665

  16. A flexible and implantable microelectrode arrays using high-temperature grown vertical carbon nanotubes and a biocompatible polymer substrate.

    PubMed

    Yi, Wenwen; Chen, Chaoyang; Feng, Zhaoying; Xu, Yong; Zhou, Chengpeng; Masurkar, Nirul; Cavanaugh, John; Cheng, Mark Ming-Cheng

    2015-03-27

    This paper presents a novel microelectrode arrays using high-temperature grown vertically aligned carbon nanotubes (CNTs) integrated on a flexible and biocompatible parylene substrate. A simple microfabrication process is proposed to unite the high quality vertical CNTs grown at high temperature with the heat sensitive parylene substrate in a highly controllable manner. Briefly, the CNTs electrode is encapsulated by two layers of parylene and the device is released using xenon difluoride (XeF2). The process is compatible with wafer-scale post complementary metal oxide semiconductor integration. Lower impedance and larger interfacial capacitance have been demonstrated using CNTs compared to a Pt electrode. The flexible CNT electrodes have been utilized for extracellular neuronal recording and stimulation in rats. The signal-to-noise ratio of the device is about 12.5. The threshold voltage for initiating action potential is about 0.5 V.

  17. Spatial analysis of slowly oscillating electric activity in the gut of mice using low impedance arrayed microelectrodes.

    PubMed

    Taniguchi, Mizuki; Kajioka, Shunichi; Shozib, Habibul B; Sawamura, Kenta; Nakayama, Shinsuke

    2013-01-01

    Smooth and elaborate gut motility is based on cellular cooperation, including smooth muscle, enteric neurons and special interstitial cells acting as pacemaker cells. Therefore, spatial characterization of electric activity in tissues containing these electric excitable cells is required for a precise understanding of gut motility. Furthermore, tools to evaluate spatial electric activity in a small area would be useful for the investigation of model animals. We thus employed a microelectrode array (MEA) system to simultaneously measure a set of 8×8 field potentials in a square area of ∼1 mm(2). The size of each recording electrode was 50×50 µm(2), however the surface area was increased by fixing platinum black particles. The impedance of microelectrode was sufficiently low to apply a high-pass filter of 0.1 Hz. Mapping of spectral power, and auto-correlation and cross-correlation parameters characterized the spatial properties of spontaneous electric activity in the ileum of wild-type (WT) and W/W(v) mice, the latter serving as a model of impaired network of pacemaking interstitial cells. Namely, electric activities measured varied in both size and cooperativity in W/W(v) mice, despite the small area. In the ileum of WT mice, procedures suppressing the excitability of smooth muscle and neurons altered the propagation of spontaneous electric activity, but had little change in the period of oscillations. In conclusion, MEA with low impedance electrodes enables to measure slowly oscillating electric activity, and is useful to evaluate both histological and functional changes in the spatio-temporal property of gut electric activity.

  18. Individually addressable microelectrode arrays fabricated with gold-coated pencil graphite particles for multiplexed and high sensitive impedance immunoassays.

    PubMed

    Zhang, Yun; Wang, Hua; Nie, Jinfang; Zhang, Yuwei; Shen, Guoli; Yu, Ruqin

    2009-09-15

    A renewable, site-selective immobilization platform of microelectrode array (MEA) for multiplexed immunoassays has been initially developed using pencil graphite particles coated with gold layers as microelectrodes. The graphite particles available on the common pencil were utilized for directing the electro-deposition of gold layers with uniform microstructures which displayed a well-defined sigmoidal voltammetric response. In the concept-of-proof experiments, the resulting MEA platform was modified with functionalized monolayer, on which anti-human IgG antibodies could be stably immobilized in a site-selective way through binding chemistry to selectively capture human IgG antigens from the sample media. The subsequent introduction of anti-human IgG antibodies conjugated with 15 nm electro-active gold nanoparticles to recognize the captured IgG proteins resulted in a significant decrease in the interfacial electron-transfer resistance. High sensitive electrochemical quantification by gold nanoparticle-amplified impedance responses could thus be achieved. Experimental results show that the developed MEA sensor can allow for the detection of human IgG with wide linear range (0.05-100 ng ml(-1)) and sensitivity over 10(3) larger than that of the conventional, bulk gold electrode. The rapid regeneration of the used MEA platform can additionally be realized by a simple electrochemical treatment. The high selectivity of four individually addressable MEA platforms for multiple antigens in a single sample has been further demonstrated in the multiplexed immunoassay experiments. Such a site-selective immobilization strategy of MEA platform may open a new door towards the development of various simple, sensitive, cost-effective, and reusable biological sensors and biochips.

  19. LSSA (Low-cost Silicon Solar Array) project

    NASA Technical Reports Server (NTRS)

    1976-01-01

    The Photovoltaic Conversion Program was established to find methods of economically generating enough electrical power to meet future requirements. Activities and progress in the following areas are discussed: silicon-refinement processes; silicon-sheet-growth techniques; encapsulants; manufacturing of off-the-shelf solar arrays; and procurement of semistandardized solar arrays.

  20. In Situ Characterization of Stimulating Microelectrode Arrays: Study of an Idealized Structure Based on Argus II Retinal implants

    NASA Astrophysics Data System (ADS)

    Kandagor, Vincent; Cela, Carlos J.; Sanders, Charlene A.; Greenbaum, Elias; Lazzi, Gianluca; Zhou, David D.; Castro, Richard; Gaikwad, Sanjay; Little, Jim

    The development of a retinal prosthesis for artificial sight includes a study of the factors affecting the structural and functional stability of chronically implanted microelectrode arrays. Although neuron depolarization and propagation of electrical signals have been studied for nearly a century, the use of multielectrode stimulation as a proposed therapy to treat blindness is a frontier area of modern ophthalmology research. Mapping and characterizing the topographic information contained in the electric field potentials and understanding how this information is transmitted and interpreted in the visual cortex is still very much a work in progress. In order to characterize the electrical field patterns generated by the device, an in vitro prototype that mimics several of the physical and chemical parameters of the in vivo visual implant device was fabricated. We carried out multiple electrical measurements in a model "eye," beginning with a single electrode, followed by a 9-electrode array structure, both idealized components based on the Argus II retinal implants. Correlating the information contained in the topographic features of the electric fields with psychophysical testing in patients may help reduce the time required for patients to convert the electrical patterns into graphic signals.

  1. LSSA (Low-cost Silicon Solar Array) project

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Methods are explored for economically generating electrical power to meet future requirements. The Low-Cost Silicon Solar Array Project (LSSA) was established to reduce the price of solar arrays by improving manufacturing technology, adapting mass production techniques, and promoting user acceptance. The new manufacturing technology includes the consideration of new silicon refinement processes, silicon sheet growth techniques, encapsulants, and automated assembly production being developed under contract by industries and universities.

  2. Design of two dimensional silicon nanowire arrays for antireflection and light trapping in silicon solar cells

    NASA Astrophysics Data System (ADS)

    Ding, Wuchang; Jia, Rui; Li, Haofeng; Chen, Chen; Sun, Yun; Jin, Zhi; Liu, Xinyu

    2014-01-01

    Silicon nitride coated nanowire arrays have been investigated as an efficient antireflection structure for silicon solar cells. The minimum average reflectance could reach 1.62% under AM1.5 spectrum. Scattering effects of silicon nanowire arrays also result in enhanced absorption in the substrate, and analytical results show that the scattered light can be well trapped in silicon substrate when the back surface is passivated by silicon dioxide. This ultra-low surface reflection property combined with light trapping effect may have potential applications in silicon solar cells with thin substrate.

  3. Thermal conductivity in porous silicon nanowire arrays.

    PubMed

    Weisse, Jeffrey M; Marconnet, Amy M; Kim, Dong Rip; Rao, Pratap M; Panzer, Matthew A; Goodson, Kenneth E; Zheng, Xiaolin

    2012-10-06

    The nanoscale features in silicon nanowires (SiNWs) can suppress phonon propagation and strongly reduce their thermal conductivities compared to the bulk value. This work measures the thermal conductivity along the axial direction of SiNW arrays with varying nanowire diameters, doping concentrations, surface roughness, and internal porosities using nanosecond transient thermoreflectance. For SiNWs with diameters larger than the phonon mean free path, porosity substantially reduces the thermal conductivity, yielding thermal conductivities as low as 1 W/m/K in highly porous SiNWs. However, when the SiNW diameter is below the phonon mean free path, both the internal porosity and the diameter significantly contribute to phonon scattering and lead to reduced thermal conductivity of the SiNWs.

  4. Thermal conductivity in porous silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Weisse, Jeffrey M.; Marconnet, Amy M.; Kim, Dong Rip; Rao, Pratap M.; Panzer, Matthew A.; Goodson, Kenneth E.; Zheng, Xiaolin

    2012-10-01

    The nanoscale features in silicon nanowires (SiNWs) can suppress phonon propagation and strongly reduce their thermal conductivities compared to the bulk value. This work measures the thermal conductivity along the axial direction of SiNW arrays with varying nanowire diameters, doping concentrations, surface roughness, and internal porosities using nanosecond transient thermoreflectance. For SiNWs with diameters larger than the phonon mean free path, porosity substantially reduces the thermal conductivity, yielding thermal conductivities as low as 1 W/m/K in highly porous SiNWs. However, when the SiNW diameter is below the phonon mean free path, both the internal porosity and the diameter significantly contribute to phonon scattering and lead to reduced thermal conductivity of the SiNWs.

  5. Nano-Ampere Stimulation Window for Cultured Neurons on Micro-Electrode Arrays

    DTIC Science & Technology

    2001-10-25

    the electrical potential and σ the conductivity of the NANO -AMPÈRE STIMULATION WINDOW FOR CULTURED NEURONS ON MICRO -ELECTRODE ARRAYS J.R. Buitenweg1... Nano -Ampere Stimulatin Window for Cultured Neurons on Micro -Electrode Arrays Contract Number Grant Number Program Element Number Author(s) Project...membrane, using a nano -ampère current through the extracellular electrode. Also, a stimulation window is observed. These findings can be explained by a

  6. A 16 x 16 element extrinsic silicon detector array

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Two bismuth-doped silicon accumulation-mode charge-injection device (AMCID) infrared detector arrays are studied. The geometry and composition of the arrays, and a description of the cold and warm electronics components of the system are described. Instructions for setting up and operating the array system, plus results of a functional test, are included.

  7. Silicon-based wire electrode array for neural interfaces

    NASA Astrophysics Data System (ADS)

    Pei, Weihua; Zhao, Hui; Zhao, Shanshan; Fang, Xiaolei; Chen, Sanyuan; Gui, Qiang; Tang, Rongyu; Chen, Yuanfang; Hong, Bo; Gao, Xiaorong; Chen, Hongda

    2014-09-01

    Objectives. Metal-wire electrode arrays are widely used to record and stimulate neurons. Commonly, these devices are fabricated from a long insulated metal wire by cutting it into the proper length and using the cross-section as the electrode site. The assembly of a micro-wire electrode array with regular spacing is difficult. With the help of micro-machine technology, a silicon-based wire electrode array (SWEA) is proposed to simplify the assembling process and provide a wire-type electrode with tapered tips. Approach. Silicon wires with regular spacing coated with metal are generated from a silicon wafer through micro-fabrication and are ordered into a 3D array. A silicon wafer is cut into a comb-like structure with hexagonal teeth on both sides by anisotropic etching. To establish an array of silicon-based linear needles through isotropic wet etching, the diameters of these hexagonal teeth are reduced; their sharp edges are smoothed out and their tips are sharpened. The needle array is coated with a layer of parylene after metallization. The tips of the needles are then exposed to form an array of linear neural electrodes. With these linear electrode arrays, an array of area electrodes can be fabricated. Main results. A 6  ×  6 array of wire-type electrodes based on silicon is developed using this method. The time required to manually assemble the 3D array decreases significantly with the introduction of micro-fabricated 2D array. Meanwhile, the tip intervals in the 2D array are accurate and are controlled at no more than 1%. The SWEA is effective both in vitro and in vivo. Significance. Using this method, the SWEA can be batch-prepared in advance along with its parameters, such as spacing, length, and diameter. Thus, neural scientists can assemble proper electrode arrays in a short time.

  8. A Compact Microelectrode Array Chip with Multiple Measuring Sites for Electrochemical Applications

    PubMed Central

    Dimaki, Maria; Vergani, Marco; Heiskanen, Arto; Kwasny, Dorota; Sasso, Luigi; Carminati, Marco; Gerrard, Juliet A.; Emneus, Jenny; Svendsen, Winnie E.

    2014-01-01

    In this paper we demonstrate the fabrication and electrochemical characterization of a microchip with 12 identical but individually addressable electrochemical measuring sites, each consisting of a set of interdigitated electrodes acting as a working electrode as well as two circular electrodes functioning as a counter and reference electrode in close proximity. The electrodes are made of gold on a silicon oxide substrate and are passivated by a silicon nitride membrane. A method for avoiding the creation of high edges at the electrodes (known as lift-off ears) is presented. The microchip design is highly symmetric to accommodate easy electronic integration and provides space for microfluidic inlets and outlets for integrated custom-made microfluidic systems on top. PMID:24878592

  9. A new 3-D finite-element model based on thin-film approximation for microelectrode array recording of extracellular action potential.

    PubMed

    Moulin, Céline; Glière, Alain; Barbier, Daniel; Joucla, Sebastien; Yvert, Blaise; Mailley, Pascal; Guillemaud, Régis

    2008-02-01

    A transient finite-element model has been developed to simulate an extracellular action potential recording in a tissue slice by a planar microelectrode array. The thin-film approximation of the active neuron membrane allows the simulation within single finite-element software of the intracellular and extracellular potential fields. In comparison with a compartmental neuron model, it is shown that the thin-film approximation-based model is able to properly represent the neuron bioelectrical behavior in terms of transmembrane current and potential. Moreover, the model is able to simulate extracellular action potential recordings with properties similar to those observed in biological experiments. It is demonstrated that an ideal measurement system model can be used to represent the recording microelectrode, provided that the electronic recording system adapts to the electrode-tissue interface impedance. By comparing it with a point source approximated neuron, it is also shown that the neuron three-dimensional volume should be taken into account to simulate the extracellular action potential recording. Finally, the influence of the electrode size on the signal amplitude is evaluated. This parameter, together with the microelectrode noise, should be taken into account in order to optimize future microelectrode designs in terms of the signal-to-noise ratio.

  10. A new high-density (25 electrodes/mm2) penetrating microelectrode array for recording and stimulating sub-millimeter neuroanatomical structures

    NASA Astrophysics Data System (ADS)

    Wark, H. A. C.; Sharma, R.; Mathews, K. S.; Fernandez, E.; Yoo, J.; Christensen, B.; Tresco, P.; Rieth, L.; Solzbacher, F.; Normann, R. A.; Tathireddy, P.

    2013-08-01

    Objective. Among the currently available neural interface devices, there has been a need for a penetrating electrode array with a high electrode-count and high electrode-density (the number of electrodes/mm2) that can be used for electrophysiological studies of sub-millimeter neuroanatomical structures. We have developed such a penetrating microelectrode array with both a high electrode-density (25 electrodes/mm2) and high electrode-count (up to 96 electrodes) for small nervous system structures, based on the existing Utah Slanted Electrode Array (USEA). Such high electrode-density arrays are expected to provide greater access to nerve fibers than the conventionally spaced USEA especially in small diameter nerves. Approach. One concern for such high density microelectrode arrays is that they may cause a nerve crush-type injury upon implantation. We evaluated this possibility during acute (<10 h) in vivo experiments with electrode arrays implanted into small diameter peripheral nerves of anesthetized rats (sciatic nerve) and cats (pudendal nerve). Main results. Successful intrafascicular implantation and viable nerve function was demonstrated via microstimulation, single-unit recordings and histological analysis. Measurements of the electrode impedances and quantified electrode dimensions demonstrated fabrication quality. The results of these experiments show that such high density neural interfaces can be implanted acutely into neural tissue without causing a complete nerve crush injury, while mediating intrafascicular access to fibers in small diameter peripheral nerves. Significance. This new penetrating microelectrode array has characteristics un-matched by other neural interface devices currently available for peripheral nervous system neurophysiological research.

  11. Electric Cell-Substrate Impedance Sensing (ECIS) with Microelectrode Arrays for Investigation of Cancer Cell – Fibroblasts Interaction

    PubMed Central

    Tran, Trong Binh; Baek, Changyoon; Min, Junhong

    2016-01-01

    The tumor microenvironment, including stromal cells, surrounding blood vessels and extracellular matrix components, has been defined as a crucial factor that influences the proliferation, drug-resistance, invasion and metastasis of malignant epithelial cells. Among other factors, the communications and interaction between cancer cells and stromal cells have been reported to play pivotal roles in cancer promotion and progression. To investigate these relationships, an on-chip co-culture model was developed to study the cellular interaction between A549—human lung carcinoma cells and MRC-5—human lung epithelial cells in both normal proliferation and treatment conditions. In brief, a co-culture device consisting of 2 individual fluidic chambers in parallel, which were separated by a 100 μm fence was utilized for cell patterning. Microelectrodes arrays were installed within each chamber including electrodes at various distances away from the confrontation line for the electrochemical impedimetric sensing assessment of cell-to-cell influence. After the fence was removed and cell-to-cell contact occurred, by evaluating the impedance signal responses representing cell condition and behavior, both direct and indirect cell-to-cell interactions through conditioned media were investigated. The impact of specific distances that lead to different influences of fibroblast cells on cancer cells in the co-culture environment was also defined. PMID:27088611

  12. Electric Cell-Substrate Impedance Sensing (ECIS) with Microelectrode Arrays for Investigation of Cancer Cell-Fibroblasts Interaction.

    PubMed

    Tran, Trong Binh; Baek, Changyoon; Min, Junhong

    2016-01-01

    The tumor microenvironment, including stromal cells, surrounding blood vessels and extracellular matrix components, has been defined as a crucial factor that influences the proliferation, drug-resistance, invasion and metastasis of malignant epithelial cells. Among other factors, the communications and interaction between cancer cells and stromal cells have been reported to play pivotal roles in cancer promotion and progression. To investigate these relationships, an on-chip co-culture model was developed to study the cellular interaction between A549-human lung carcinoma cells and MRC-5-human lung epithelial cells in both normal proliferation and treatment conditions. In brief, a co-culture device consisting of 2 individual fluidic chambers in parallel, which were separated by a 100 μm fence was utilized for cell patterning. Microelectrodes arrays were installed within each chamber including electrodes at various distances away from the confrontation line for the electrochemical impedimetric sensing assessment of cell-to-cell influence. After the fence was removed and cell-to-cell contact occurred, by evaluating the impedance signal responses representing cell condition and behavior, both direct and indirect cell-to-cell interactions through conditioned media were investigated. The impact of specific distances that lead to different influences of fibroblast cells on cancer cells in the co-culture environment was also defined.

  13. Femtomolar Detection of Silver Nanoparticles by Flow-Enhanced Direct-Impact Voltammetry at a Microelectrode Array

    PubMed Central

    2016-01-01

    We report the femtomolar detection of silver (Ag) nanoparticles by direct-impact voltammetry. This is achieved through the use of a random array of microelectrodes (RAM) integrated into a purpose-built flow cell, allowing combined diffusion and convection to the electrode surface. A coupled RAM-flow cell system is implemented and is shown to give reproducible wall-jet type flow characteristics, using potassium ferrocyanide as a molecular redox species. The calibrated flow system is then used to detect and quantitatively size Ag nanoparticles at femtomolar concentrations. Under flow conditions, it is found the nanoparticle impact frequency increases linearly with the volumetric flow rate. The resulting limit of detection is more than 2 orders of magnitude smaller than the previous detection limit for direct-impact voltammetry (900 fM) [J. Ellison et al. Sens. Actuators, B2014, 200, 47], and is more than 30 times smaller than the previous detection limit for mediated-impact voltammetry (83 fM) [T. M. Alligrant et al. Langmuir2014, 30, 13462]. PMID:27494652

  14. Comparative Analysis of Human and Rodent Brain Primary Neuronal Culture Spontaneous Activity Using Micro-Electrode Array Technology.

    PubMed

    Napoli, Alessandro; Obeid, Iyad

    2016-03-01

    Electrical activity in embryonic brain tissue has typically been studied using Micro Electrode Array (MEA) technology to make dozens of simultaneous recordings from dissociated neuronal cultures, brain stem cell progenitors, or brain slices from fetal rodents. Although these rodent neuronal primary culture electrical properties are mostly investigated, it has not been yet established to what extent the electrical characteristics of rodent brain neuronal cultures can be generalized to those of humans. A direct comparison of spontaneous spiking activity between rodent and human primary neurons grown under the same in vitro conditions using MEA technology has never been carried out before and will be described in the present study. Human and rodent dissociated fetal brain neuronal cultures were established in-vitro by culturing on a glass grid of 60 planar microelectrodes neurons under identical conditions. Three different cultures of human neurons were produced from tissue sourced from a single aborted fetus (at 16-18 gestational weeks) and these were compared with seven different cultures of embryonic rat neurons (at 18 gestational days) originally isolated from a single rat. The results show that the human and rodent cultures behaved significantly differently. Whereas the rodent cultures demonstrated robust spontaneous activation and network activity after only 10 days, the human cultures required nearly 40 days to achieve a substantially weaker level of electrical function. These results suggest that rat neuron preparations may yield inferences that do not necessarily transfer to humans.

  15. Femtomolar Detection of Silver Nanoparticles by Flow-Enhanced Direct-Impact Voltammetry at a Microelectrode Array.

    PubMed

    Sokolov, Stanislav V; Bartlett, Thomas R; Fair, Peter; Fletcher, Stephen; Compton, Richard G

    2016-09-06

    We report the femtomolar detection of silver (Ag) nanoparticles by direct-impact voltammetry. This is achieved through the use of a random array of microelectrodes (RAM) integrated into a purpose-built flow cell, allowing combined diffusion and convection to the electrode surface. A coupled RAM-flow cell system is implemented and is shown to give reproducible wall-jet type flow characteristics, using potassium ferrocyanide as a molecular redox species. The calibrated flow system is then used to detect and quantitatively size Ag nanoparticles at femtomolar concentrations. Under flow conditions, it is found the nanoparticle impact frequency increases linearly with the volumetric flow rate. The resulting limit of detection is more than 2 orders of magnitude smaller than the previous detection limit for direct-impact voltammetry (900 fM) [J. Ellison et al. Sens. Actuators, B 2014, 200, 47], and is more than 30 times smaller than the previous detection limit for mediated-impact voltammetry (83 fM) [T. M. Alligrant et al. Langmuir 2014, 30, 13462].

  16. Extracellularly Recorded Somatic and Neuritic Signal Shapes and Classification Algorithms for High-Density Microelectrode Array Electrophysiology

    PubMed Central

    Deligkaris, Kosmas; Bullmann, Torsten; Frey, Urs

    2016-01-01

    High-density microelectrode arrays (HDMEA) have been recently introduced to study principles of neural function at high spatial resolution. However, the exact nature of the experimentally observed extracellular action potentials (EAPs) is still incompletely understood. The soma, axon and dendrites of a neuron can all exhibit regenerative action potentials that could be sensed with HDMEA electrodes. Here, we investigate the contribution of distinct neuronal sources of activity in HDMEA recordings from low-density neuronal cultures. We recorded EAPs with HDMEAs having 11,011 electrodes and then fixed and immunostained the cultures with β3-tubulin for high-resolution fluorescence imaging. Immunofluorescence images overlaid with the activity maps showed EAPs both at neuronal somata and distal neurites. Neuritic EAPs had mostly narrow triphasic shapes, consisting of a positive, a pronounced negative peak and a second positive peak. EAPs near somata had wide monophasic or biphasic shapes with a main negative peak, and following optional positive peak. We show that about 86% of EAP recordings consist of somatic spikes, while the remaining 14% represent neuritic spikes. Furthermore, the adaptation of the waveform shape during bursts of these neuritic spikes suggested that they originate from axons, rather than from dendrites. Our study improves the understanding of HDMEA signals and can aid in the identification of the source of EAPs. PMID:27683541

  17. On-line observation of cell growth in a three-dimensional matrix on surface-modified microelectrode arrays.

    PubMed

    Lin, Shu-Ping; Kyriakides, Themis R; Chen, Jia-Jin J

    2009-06-01

    Despite many successful applications of microelectrode arrays (MEAs), typical two-dimensional in-vitro cultures do not project the full scale of the cell growth environment in the three-dimensional (3D) in-vivo setting. This study aims to on-line monitor in-vitro cell growth in a 3D matrix on the surface-modified MEAs with a dynamic perfusion culture system. A 3D matrix consisting of poly(ethylene glycol) hydrogel supplemented with poly-D-lysine was subsequently synthesized in situ on the self-assembled monolayer modified MEAs. FTIR spectrum analysis revealed a peak at 2100 cm(-1) due to the degradation of the structure of the 3D matrix. After 2 wks, microscopic examination revealed that the non-degraded area was around 1500 microm(2) and provided enough space for cell growth. Fluorescence microscopy revealed that the degraded 3D matrix was non-cytotoxic allowing the growth of NIH3T3 fibroblasts and cortical neurons in vitro. Time-course changes of total impedance including resistance and reactance were recorded for 8 days to evaluate the cell growth in the 3D matrix on the MEA. A consistent trend reflecting changes of reactance and total impedance was observed. These in-vitro assays demonstrate that our 3D matrix can construct a biomimetic system for cell growth and analysis of cell surface interactions.

  18. High efficiency, site-specific transfection of adherent cells with siRNA using microelectrode arrays (MEA).

    PubMed

    Patel, Chetan; Muthuswamy, Jit

    2012-09-13

    The discovery of RNAi pathway in eukaryotes and the subsequent development of RNAi agents, such as siRNA and shRNA, have achieved a potent method for silencing specific genes for functional genomics and therapeutics. A major challenge involved in RNAi based studies is the delivery of RNAi agents to targeted cells. Traditional non-viral delivery techniques, such as bulk electroporation and chemical transfection methods often lack the necessary spatial control over delivery and afford poor transfection efficiencies. Recent advances in chemical transfection methods such as cationic lipids, cationic polymers and nanoparticles have resulted in highly enhanced transfection efficiencies. However, these techniques still fail to offer precise spatial control over delivery that can immensely benefit miniaturized high-throughput technologies, single cell studies and investigation of cell-cell interactions. Recent technological advances in gene delivery have enabled high-throughput transfection of adherent cells, a majority of which use microscale electroporation. Microscale electroporation offers precise spatio-temporal control over delivery (up to single cells) and has been shown to achieve high efficiencies. Additionally, electroporation based approaches do not require a prolonged period of incubation (typically 4 hours) with siRNA and DNA complexes as necessary in chemical based transfection methods and lead to direct entry of naked siRNA and DNA molecules into the cell cytoplasm. As a consequence gene expression can be achieved as early as six hours after transfection. Our lab has previously demonstrated the use of microelectrode arrays (MEA) for site-specific transfection in adherent mammalian cell cultures. In the MEA based approach, delivery of genetic payload is achieved via localized micro-scale electroporation of cells. An application of electric pulse to selected electrodes generates local electric field that leads to electroporation of cells present in the region

  19. Biocompatibility of silicon-based arrays of electrodes coupled to organotypic hippocampal brain slice cultures.

    PubMed

    Kristensen, B W; Noraberg, J; Thiébaud, P; Koudelka-Hep, M; Zimmer, J

    2001-03-30

    In this study we examined the passive biocompatibility of a three-dimensional microelectrode array (MEA), designed to be coupled to organotypic brain slice cultures for multisite recording of electrophysiological signals. Hippocampal (and corticostriatal) brain slices from 1-week-old (and newborn) rats were grown for 4-8 weeks on the perforated silicon chips with silicon nitride surfaces and 40 microm sized holes and compared with corresponding tissue slices grown on conventional semiporous membranes. In terms of preservation of the basic cellular and connective organization, as visualized by Nissl staining, Timm sulphide silver-staining, microtubule-associated protein 2 (MAP2) and glial fibrillary acidic protein (GFAP) immunostaining, the slice cultures grown on chips did not differ from conventionally grown slice cultures. Neither were there any signs of astrogliosis or neurodegeneration around the upper recording part of the 47-microm-high platinum-tip electrodes. Slice cultures grown on a separate set of chips with platinum instead of silicon nitride surfaces also displayed normal MAP2 and GFAP immunostaining. The width of the GFAP-rich zone (glia limitans) at the bottom surface of the slice cultures was the same ( approximately 20 microm) in cultures grown on chips with silicon nitride and platinum surfaces and on conventional insert membranes. The slice cultures grown on chips maintained a normal, subfield differentiated susceptibility to the glutamate receptor agonist N-methyl-D-aspartate (NMDA) and the neurotoxin trimethyltin (TMT), as demonstrated by the cellular uptake of propidium iodide (PI), which was used as a reproducible and quantifiable marker for neuronal degeneration. We conclude that organotypic brain slice cultures can grow on silicon-based three-dimensional microelectrode arrays and develop normally with display of normal subfield differentiated susceptibilities to known excito- and neurotoxins. From this it is anticipated that the set

  20. Development of 30 micrometers extrinsic silicon multiplexed infrared deterctor array

    NASA Technical Reports Server (NTRS)

    Orias, G.; Campbell, D.

    1986-01-01

    Two hybrid infrared (IR) detector arrays of antimony-doped silicon (Si:Sb) were produced and tested to evaluate their potential for use in low-background IR astronomy applications. The format of the arrays is 58 x 62 elements, with 76 micron-square pixels. A random-access, switched metal-oxide semiconductor field effect transistor (MOSFET) silicon multiplexer is used to read out the array elements. Reduced-background tests of signal, noise, and noise equivalent power were conducted over the temperature range 3.2 to 12 K. The arrays were found to have good sensitivity and good uniformity.

  1. Spraylon fluorocarbon encapsulation for silicon solar cell arrays

    NASA Technical Reports Server (NTRS)

    1977-01-01

    A development program was performed for evaluating, modifying, and optimizing the Lockheed formulated liquid transparent filmforming Spraylon fluorocarbon protective coating for silicon solar cells and modules. The program objectives were designed to meet the requirements of the low-cost automated solar cell array fabrication process. As part of the study, a computer program was used to establish the limits of the safe working stress in the coated silicon solar cell array system under severe thermal shock.

  2. Development of three-dimension microelectrode array for bioelectric measurement using the liquidmetal-micromolding technique

    SciTech Connect

    Liu, Ran Yang, Xueyao; Chen, Weixing; Jin, Cuiyun; Fu, Jingjing; Liu, Jing

    2013-11-04

    A method of manufacturing three-dimension microneedle electrode arrays is presented in this paper using the micromolding technology with liquid metal at room temperature, based on the physical property of the Bi-In-Sn liquid metal alloy, being its melting point especially low. Observed under scanning electron microscopy, the needle body of the electrode chip manufactured using this method has a good consistency. Skin penetration test in-vitro indicates that the microneedle electrode can pierce the stratum corneum and cross the high-impedance layer to acquire electrical signals. Electrical impedance and polarization voltage experimental results show that the electrode chips have great electric characteristics and meet the practical application demands.

  3. Development of three-dimension microelectrode array for bioelectric measurement using the liquidmetal-micromolding technique

    NASA Astrophysics Data System (ADS)

    Liu, Ran; Yang, Xueyao; Jin, Cuiyun; Fu, Jingjing; Chen, Weixing; Liu, Jing

    2013-11-01

    A method of manufacturing three-dimension microneedle electrode arrays is presented in this paper using the micromolding technology with liquid metal at room temperature, based on the physical property of the Bi-In-Sn liquid metal alloy, being its melting point especially low. Observed under scanning electron microscopy, the needle body of the electrode chip manufactured using this method has a good consistency. Skin penetration test in-vitro indicates that the microneedle electrode can pierce the stratum corneum and cross the high-impedance layer to acquire electrical signals. Electrical impedance and polarization voltage experimental results show that the electrode chips have great electric characteristics and meet the practical application demands.

  4. Editor's Highlight: Evaluation of a Microelectrode Array-Based Assay for Neural Network Ontogeny Using Training Set Chemicals.

    PubMed

    Brown, Jasmine P; Hall, Diana; Frank, Christopher L; Wallace, Kathleen; Mundy, William R; Shafer, Timothy J

    2016-11-01

    Thousands of compounds in the environment have not been characterized for developmental neurotoxicity (DNT) hazard. To address this issue, methods to screen compounds rapidly for DNT hazard evaluation are necessary and are being developed for key neurodevelopmental processes. In order to develop an assay for network formation, this study evaluated effects of a training set of chemicals on network ontogeny by measuring spontaneous electrical activity in neural networks grown on microelectrode arrays (MEAs). Rat (0-24 h old) primary cortical cells were plated in 48 well-MEA plates and exposed to 6 compounds: acetaminophen, bisindolylmaleimide-1 (Bis-1), domoic acid, mevastatin, sodium orthovanadate, and loperamide for a period of 12 days. Spontaneous network activity was recorded on days 2, 5, 7, 9, and 12 and viability was assessed using the Cell Titer Blue assay on day 12. Network activity (e.g. mean firing rate [MFR], burst rate [BR], etc), increased between days 5 and 12. Random Forest analysis indicated that across all compounds and times, temporal correlation of firing patterns (r), MFR, BR, number of active electrodes and % of spikes in a burst were the most influential parameters in separating control from treated wells. All compounds except acetaminophen (≤ 30 µM) caused concentration-related effects on one or more of these parameters. Domoic acid and sodium orthovanadate altered several of these parameters in the absence of cytotoxicity. Although cytotoxicity was observed with Bis1, mevastatin, and loperamide, some parameters were affected by these compounds at concentrations below those resulting in cytotoxicity. These results demonstrate that this assay may be suitable for screening of compounds for DNT hazard identification.

  5. Impedance biosensor for the rapid detection of Listeria spp. based on aptamer functionalized Pt-interdigitated microelectrodes array

    NASA Astrophysics Data System (ADS)

    Sidhu, R.; Rong, Y.; Vanegas, D. C.; Claussen, J.; McLamore, E. S.; Gomes, C.

    2016-05-01

    Listeria monocytogenes is one of the most common causes of food illness deaths worldwide, with multiple outbreaks in the United States alone. Current methods to detect foodborne pathogens are laborious and can take several hours to days to produce results. Thus, faster techniques are needed to detect bacteria within the same reliability level as traditional techniques. This study reports on a rapid, accurate, and sensitive aptamer biosensor device for Listeria spp. detection based on platinum interdigitated array microelectrodes (Pt-IDEs). Pt-IDEs with different geometric electrode gaps were fabricated by lithographic techniques and characterized by cyclic voltammetric (CV), electrochemical impedance spectroscopy (EIS), and potential amperometry (DCPA) measurements of reversible redox species. Based on these results, 50 μm Pt-IDE was chosen to further functionalize with a Listeria monocytogenes DNA aptamer selective to the cell surface protein internalin A, via metal-thiol self-assembly at the 5' end of the 47-mer's. EIS analysis was used to detect Listeria spp. without the need for label amplification and pre-concentration steps. The optimized aptamer concentration of 800 nM was selected to capture the bacteria through internalin A binding and the aptamer hairpin structure near the 3' end. The aptasensor was capable of detecting a wide range of bacteria concentration from 10 to 106 CFU/mL at lower detection limit of 5.39 +/- 0.21 CFU/mL with sensitivity of 268.1 +/- 25.40 (Ohms/log [CFU/mL]) in 17 min. The aptamer based biosensor offers a portable, rapid and sensitive alternative for food safety applications with one of the lowest detection limits reported to date.

  6. A microchannel device tailored to laser axotomy and long-term microelectrode array electrophysiology of functional regeneration.

    PubMed

    Habibey, Rouhollah; Golabchi, Asiyeh; Latifi, Shahrzad; Difato, Francesco; Blau, Axel

    2015-12-21

    We designed a miniaturized and thin polydimethylsiloxane (PDMS) microchannel device compatible with commercial microelectrode array (MEA) chips. It was optimized for selective axonal ablation by laser microdissection (LMD) to investigate the electrophysiological and morphological responses to a focal injury in distinct network compartments over 45 days in vitro (45 DIV). Low-density cortical or hippocampal networks (<3500 neurons per device) were cultured in quasi-closed somal chambers. Their axons were selectively filtered through neurite cavities and guided into the PDMS microchannels aligned over the recording electrodes. The device geometries amplified extracellularly recorded signals in the somal reservoir and the axonal microchannels to detectable levels. Locally extended areas along the microchannel, so-called working stations, forced axonal bundles to branch out and thereby allowed for their repeatable and controllable local, partial or complete dissections. Proximal and distal changes in the activity and morphology of the dissected axons were monitored and compared to those of their parent networks and of intact axons in the control microchannels. Microscopy images confirmed progressive anterograde degeneration of distal axonal segments over four weeks after surgery. Dissection on cortical and hippocampal axons revealed different cell type- and age-dependent network responses. At 17 DIV, network activity increased in both the somal and proximal microchannel compartments of the dissected hippocampal or cortical axons. At later days (24 DIV), the hippocampal networks were more susceptible to axonal injury. While their activity decreased, that in the cortical cultures actually increased. Subsequent partial dissections of the same axonal bundles led to a stepwise activity reduction in the distal hippocampal or cortical axonal fragments. We anticipate that the MEA-PDMS microchannel device for the combined morphological and electrophysiological study of axonal

  7. QSpike tools: a generic framework for parallel batch preprocessing of extracellular neuronal signals recorded by substrate microelectrode arrays

    PubMed Central

    Mahmud, Mufti; Pulizzi, Rocco; Vasilaki, Eleni; Giugliano, Michele

    2014-01-01

    Micro-Electrode Arrays (MEAs) have emerged as a mature technique to investigate brain (dys)functions in vivo and in in vitro animal models. Often referred to as “smart” Petri dishes, MEAs have demonstrated a great potential particularly for medium-throughput studies in vitro, both in academic and pharmaceutical industrial contexts. Enabling rapid comparison of ionic/pharmacological/genetic manipulations with control conditions, MEAs are employed to screen compounds by monitoring non-invasively the spontaneous and evoked neuronal electrical activity in longitudinal studies, with relatively inexpensive equipment. However, in order to acquire sufficient statistical significance, recordings last up to tens of minutes and generate large amount of raw data (e.g., 60 channels/MEA, 16 bits A/D conversion, 20 kHz sampling rate: approximately 8 GB/MEA,h uncompressed). Thus, when the experimental conditions to be tested are numerous, the availability of fast, standardized, and automated signal preprocessing becomes pivotal for any subsequent analysis and data archiving. To this aim, we developed an in-house cloud-computing system, named QSpike Tools, where CPU-intensive operations, required for preprocessing of each recorded channel (e.g., filtering, multi-unit activity detection, spike-sorting, etc.), are decomposed and batch-queued to a multi-core architecture or to a computers cluster. With the commercial availability of new and inexpensive high-density MEAs, we believe that disseminating QSpike Tools might facilitate its wide adoption and customization, and inspire the creation of community-supported cloud-computing facilities for MEAs users. PMID:24678297

  8. Rapid Neuronal Differentiation of Induced Pluripotent Stem Cells for Measuring Network Activity on Micro-electrode Arrays.

    PubMed

    Frega, Monica; van Gestel, Sebastianus H C; Linda, Katrin; van der Raadt, Jori; Keller, Jason; Van Rhijn, Jon-Ruben; Schubert, Dirk; Albers, Cornelis A; Nadif Kasri, Nael

    2017-01-08

    Neurons derived from human induced Pluripotent Stem Cells (hiPSCs) provide a promising new tool for studying neurological disorders. In the past decade, many protocols for differentiating hiPSCs into neurons have been developed. However, these protocols are often slow with high variability, low reproducibility, and low efficiency. In addition, the neurons obtained with these protocols are often immature and lack adequate functional activity both at the single-cell and network levels unless the neurons are cultured for several months. Partially due to these limitations, the functional properties of hiPSC-derived neuronal networks are still not well characterized. Here, we adapt a recently published protocol that describes production of human neurons from hiPSCs by forced expression of the transcription factor neurogenin-2(12). This protocol is rapid (yielding mature neurons within 3 weeks) and efficient, with nearly 100% conversion efficiency of transduced cells (>95% of DAPI-positive cells are MAP2 positive). Furthermore, the protocol yields a homogeneous population of excitatory neurons that would allow the investigation of cell-type specific contributions to neurological disorders. We modified the original protocol by generating stably transduced hiPSC cells, giving us explicit control over the total number of neurons. These cells are then used to generate hiPSC-derived neuronal networks on micro-electrode arrays. In this way, the spontaneous electrophysiological activity of hiPSC-derived neuronal networks can be measured and characterized, while retaining interexperimental consistency in terms of cell density. The presented protocol is broadly applicable, especially for mechanistic and pharmacological studies on human neuronal networks.

  9. A method for electrophysiological characterization of hamster retinal ganglion cells using a high-density CMOS microelectrode array

    PubMed Central

    Jones, Ian L.; Russell, Thomas L.; Farrow, Karl; Fiscella, Michele; Franke, Felix; Müller, Jan; Jäckel, David; Hierlemann, Andreas

    2015-01-01

    Knowledge of neuronal cell types in the mammalian retina is important for the understanding of human retinal disease and the advancement of sight-restoring technology, such as retinal prosthetic devices. A somewhat less utilized animal model for retinal research is the hamster, which has a visual system that is characterized by an area centralis and a wide visual field with a broad binocular component. The hamster retina is optimally suited for recording on the microelectrode array (MEA), because it intrinsically lies flat on the MEA surface and yields robust, large-amplitude signals. However, information in the literature about hamster retinal ganglion cell functional types is scarce. The goal of our work is to develop a method featuring a high-density (HD) complementary metal-oxide-semiconductor (CMOS) MEA technology along with a sequence of standardized visual stimuli in order to categorize ganglion cells in isolated Syrian Hamster (Mesocricetus auratus) retina. Since the HD-MEA is capable of recording at a higher spatial resolution than most MEA systems (17.5 μm electrode pitch), we were able to record from a large proportion of RGCs within a selected region. Secondly, we chose our stimuli so that they could be run during the experiment without intervention or computation steps. The visual stimulus set was designed to activate the receptive fields of most ganglion cells in parallel and to incorporate various visual features to which different cell types respond uniquely. Based on the ganglion cell responses, basic cell properties were determined: direction selectivity, speed tuning, width tuning, transience, and latency. These properties were clustered to identify ganglion cell types in the hamster retina. Ultimately, we recorded up to a cell density of 2780 cells/mm2 at 2 mm (42°) from the optic nerve head. Using five parameters extracted from the responses to visual stimuli, we obtained seven ganglion cell types. PMID:26528115

  10. A method for electrophysiological characterization of hamster retinal ganglion cells using a high-density CMOS microelectrode array.

    PubMed

    Jones, Ian L; Russell, Thomas L; Farrow, Karl; Fiscella, Michele; Franke, Felix; Müller, Jan; Jäckel, David; Hierlemann, Andreas

    2015-01-01

    Knowledge of neuronal cell types in the mammalian retina is important for the understanding of human retinal disease and the advancement of sight-restoring technology, such as retinal prosthetic devices. A somewhat less utilized animal model for retinal research is the hamster, which has a visual system that is characterized by an area centralis and a wide visual field with a broad binocular component. The hamster retina is optimally suited for recording on the microelectrode array (MEA), because it intrinsically lies flat on the MEA surface and yields robust, large-amplitude signals. However, information in the literature about hamster retinal ganglion cell functional types is scarce. The goal of our work is to develop a method featuring a high-density (HD) complementary metal-oxide-semiconductor (CMOS) MEA technology along with a sequence of standardized visual stimuli in order to categorize ganglion cells in isolated Syrian Hamster (Mesocricetus auratus) retina. Since the HD-MEA is capable of recording at a higher spatial resolution than most MEA systems (17.5 μm electrode pitch), we were able to record from a large proportion of RGCs within a selected region. Secondly, we chose our stimuli so that they could be run during the experiment without intervention or computation steps. The visual stimulus set was designed to activate the receptive fields of most ganglion cells in parallel and to incorporate various visual features to which different cell types respond uniquely. Based on the ganglion cell responses, basic cell properties were determined: direction selectivity, speed tuning, width tuning, transience, and latency. These properties were clustered to identify ganglion cell types in the hamster retina. Ultimately, we recorded up to a cell density of 2780 cells/mm(2) at 2 mm (42°) from the optic nerve head. Using five parameters extracted from the responses to visual stimuli, we obtained seven ganglion cell types.

  11. Restoring motor control and sensory feedback in people with upper extremity amputations using arrays of 96 microelectrodes implanted in the median and ulnar nerves

    NASA Astrophysics Data System (ADS)

    Davis, T. S.; Wark, H. A. C.; Hutchinson, D. T.; Warren, D. J.; O'Neill, K.; Scheinblum, T.; Clark, G. A.; Normann, R. A.; Greger, B.

    2016-06-01

    Objective. An important goal of neuroprosthetic research is to establish bidirectional communication between the user and new prosthetic limbs that are capable of controlling >20 different movements. One strategy for achieving this goal is to interface the prosthetic limb directly with efferent and afferent fibres in the peripheral nervous system using an array of intrafascicular microelectrodes. This approach would provide access to a large number of independent neural pathways for controlling high degree-of-freedom prosthetic limbs, as well as evoking multiple-complex sensory percepts. Approach. Utah Slanted Electrode Arrays (USEAs, 96 recording/stimulating electrodes) were implanted for 30 days into the median (Subject 1-M, 31 years post-amputation) or ulnar (Subject 2-U, 1.5 years post-amputation) nerves of two amputees. Neural activity was recorded during intended movements of the subject’s phantom fingers and a linear Kalman filter was used to decode the neural data. Microelectrode stimulation of varying amplitudes and frequencies was delivered via single or multiple electrodes to investigate the number, size and quality of sensory percepts that could be evoked. Device performance over time was assessed by measuring: electrode impedances, signal-to-noise ratios (SNRs), stimulation thresholds, number and stability of evoked percepts. Main results. The subjects were able to proportionally, control individual fingers of a virtual robotic hand, with 13 different movements decoded offline (r = 0.48) and two movements decoded online. Electrical stimulation across one USEA evoked >80 sensory percepts. Varying the stimulation parameters modulated percept quality. Devices remained intrafascicularly implanted for the duration of the study with no significant changes in the SNRs or percept thresholds. Significance. This study demonstrated that an array of 96 microelectrodes can be implanted into the human peripheral nervous system for up to 1 month durations. Such an

  12. Microfabricated Silicon Microneedle Array for Transdermal Drug Delivery

    NASA Astrophysics Data System (ADS)

    Ji, Jing; Tay, Francis Eh; Miao, Jianmin; Iliescu, Ciprian

    2006-04-01

    This paper presents developed processes for silicon microneedle arrays microfabrication. Three types of microneedles structures were achieved by isotropic etching in inductively coupled plasma (ICP) using SF6/O2 gases, combination of isotropic etching with deep etching, and wet etching, respectively. A microneedle array with biodegradable porous tips was further developed based on the fabricated microneedles.

  13. Low cost silicon solar array project silicon materials task

    NASA Technical Reports Server (NTRS)

    1977-01-01

    A program was established to develop a high temperature silicon production process using existing electric arc heater technology. Silicon tetrachloride and a reductant will be injected into an arc heated mixture of hydrogen and argon. Under these high temperature conditions, a very rapid reaction is expected to occur and proceed essentially to completion, yielding silicon and gaseous sodium chloride. Techniques for high temperature separation and collection of the molten silicon will be developed using standard engineering approaches, and the salt vapor will later be electrolytically separated into its elemental constituents for recycle. Preliminary technical evaluations and economic projections indicate not only that this process appears to be feasible, but that it also has the advantages of rapid, high capacity production of good quality molten silicon at a nominal cost.

  14. Develop Silicone Encapsulation Systems for Terrestrial Silicon Solar Arrays

    NASA Technical Reports Server (NTRS)

    1979-01-01

    A cost effective encapsulant system was identified and a silicone acrylic cover material containing a durable ultraviolet screening agent was prepared. The effectiveness of the cover material in protecting photo-oxidatively sensitive polymers was demonstrated.

  15. Coherent acoustic vibrations in silicon submicron spiral arrays

    NASA Astrophysics Data System (ADS)

    Yamaguchi, Masashi; Liu, Jianxun; Ye, Dexian; Lu, Toh-Ming

    2009-08-01

    Mechanical properties of complex silicon submicron structures have been studied both experimentally and theoretically using time resolved ultrafast spectroscopy and finite element analysis. Periodic and random arrays of single-turned silicon submircron spirals were grown using the oblique angle deposition technique. Resonant vibrational modes of the submicron spirals were coherently excited by femtosecond laser pulses. Excitation of multiple harmonics of the resonant vibrations has been observed, and the mode patterns of the excited vibrations in the submicron spirals have been calculated.

  16. Neural control of cursor trajectory and click by a human with tetraplegia 1000 days after implant of an intracortical microelectrode array

    NASA Astrophysics Data System (ADS)

    Simeral, J. D.; Kim, S.-P.; Black, M. J.; Donoghue, J. P.; Hochberg, L. R.

    2011-04-01

    The ongoing pilot clinical trial of the BrainGate neural interface system aims in part to assess the feasibility of using neural activity obtained from a small-scale, chronically implanted, intracortical microelectrode array to provide control signals for a neural prosthesis system. Critical questions include how long implanted microelectrodes will record useful neural signals, how reliably those signals can be acquired and decoded, and how effectively they can be used to control various assistive technologies such as computers and robotic assistive devices, or to enable functional electrical stimulation of paralyzed muscles. Here we examined these questions by assessing neural cursor control and BrainGate system characteristics on five consecutive days 1000 days after implant of a 4 × 4 mm array of 100 microelectrodes in the motor cortex of a human with longstanding tetraplegia subsequent to a brainstem stroke. On each of five prospectively-selected days we performed time-amplitude sorting of neuronal spiking activity, trained a population-based Kalman velocity decoding filter combined with a linear discriminant click state classifier, and then assessed closed-loop point-and-click cursor control. The participant performed both an eight-target center-out task and a random target Fitts metric task which was adapted from a human-computer interaction ISO standard used to quantify performance of computer input devices. The neural interface system was further characterized by daily measurement of electrode impedances, unit waveforms and local field potentials. Across the five days, spiking signals were obtained from 41 of 96 electrodes and were successfully decoded to provide neural cursor point-and-click control with a mean task performance of 91.3% ± 0.1% (mean ± s.d.) correct target acquisition. Results across five consecutive days demonstrate that a neural interface system based on an intracortical microelectrode array can provide repeatable, accurate point

  17. Multifunctional microelectrode array (mMEA) chip for neural-electrical and neural-chemical interfaces: characterization of comb interdigitated electrode towards dopamine detection.

    PubMed

    Chuang, Min-Chieh; Lai, Hsin-Yi; Annie Ho, Ja-An; Chen, You-Yin

    2013-03-15

    Microelectrode array platforms have attracted considerable interest owing to their ability to facilitate interactive communications between investigators and neuronal network. We herein present an integrated multifunctional microelectrode array (mMEA) chip harnessed with multiple measurement modalities of both neural-electrical and neural-chemical recordings to enable simultaneous monitoring of action potential and the level of the specific neurotransmitter. A dopamine sensor modality fabricated in interdigitated electrodes (IDE) fashion was realized and characterized, subsequently applied to trace dopamine exocytosis in PC12 cells cultured on such mMEA chip. Facile fabrication process leveraging electroplating technique to implement the regulation of gap width was investigated and resulted in preferred IDE configuration. Collection efficiency and amplification effect were systematically evaluated. The as-fabricated sensing device exhibited a favorable diffusion-determining behavior reflected by the steady state current output, and in virtue of this feature, to detect dopamine in connection with limit of detection at 0.62 μM. The current signal was observed linear against the level of dopamine over the investigated concentration range with a resulting sensitivity of 0.096 nA μM(-1).

  18. Nanoscale laminin coating modulates cortical scarring response around implanted silicon microelectrode arrays

    NASA Astrophysics Data System (ADS)

    He, Wei; McConnell, George C.; Bellamkonda, Ravi V.

    2006-12-01

    Neural electrodes could significantly enhance the quality of life for patients with sensory and/or motor deficits as well as improve our understanding of brain functions. However, long-term electrical connectivity between neural tissue and recording sites is compromised by the development of astroglial scar around the recording probes. In this study we investigate the effect of a nanoscale laminin (LN) coating on Si-based neural probes on chronic cortical tissue reaction in a rat model. Tissue reaction was evaluated after 1 day, 1 week, and 4 weeks post-implant for coated and uncoated probes using immunohistochemical techniques to evaluate activated microglia/macrophages (ED-1), astrocytes (GFAP) and neurons (NeuN). The coating did not have an observable effect on neuronal density or proximity to the electrode surface. However, the response of microglia/macrophages and astrocytes was altered by the coating. One day post-implant, we observed an ~60% increase in ED-1 expression near LN-coated probe sites compared with control uncoated probe sites. Four weeks post-implant, we observed an ~20% reduction in ED-1 expression along with an ~50% reduction in GFAP expression at coated relative to uncoated probe sites. These results suggest that LN has a stimulatory effect on early microglia activation, accelerating the phagocytic function of these cells. This hypothesis is further supported by the increased mRNA expression of several pro-inflammatory cytokines (TNF-α, IL-1 and IL-6) in cultured microglia on LN-bound Si substrates. LN immunostaining of coated probes immediately after insertion and retrieval demonstrates that the coating integrity is not compromised by the shear force during insertion. We speculate, based on these encouraging results, that LN coating of Si neural probes could potentially improve chronic neural recordings through dispersion of the astroglial scar.

  19. Performance of a MedArray silicone hollow fiber oxygenator.

    PubMed

    LaFayette, Nathan G; Schewe, Rebecca E; Montoya, J Patrick; Cook, Keith E

    2009-01-01

    A silicone hollow fiber oxygenator was evaluated to characterize gas transfer and biocompatibility. The device's fiber bundle was composed of MedArray's silicone hollow fibers with a 320 microm outside diameter, a 50 microm wall thickness, a surface area of 0.45 m, and a 0.49 void fraction. An in vitro gas exchange study was performed comparing the MedArray device (n = 9) with the Medtronic 0600 oxygenator (n = 6) using Association for the Advancement of Medical Instrumentation standards and blood flow rates of 0.5-1.75 L/min, and an oxygen to blood flow ratio of two. Biocompatibility and resistance studies were performed in vivo using a swine venovenous extracorporeal membrane oxygenation model (MedArray n = 5, Medtronic n = 5). Average O(2) transfer at 1 L/min was 86 ml/min/m in the MedArray device and 101.1 ml/min/m in the Medtronic device. At 0.5 L/min the MedArray and Medtronic device average resistance was 15.5 and 148.5 mm Hg/(L/min), respectively. Both devices had similar platelet consumption and hemolysis. Results indicate that the MedArray device has lower O(2) transfer efficiency, similar biocompatibility, and lower resistance than the Medtronic 0600 oxygenator. Optimization of the MedArray fiber bundle and housing design is necessary to improve O(2) transfer efficiency while maintaining lower device resistance than the Medtronic oxygenator.

  20. Wrinkled single-layer graphenes fabricated by silicon nanopillar arrays

    NASA Astrophysics Data System (ADS)

    Li, Zibo; Wu, Yutong; Nan, Jingjie; Tang, Xiaoduo; Zhang, Junhu; Yang, Bai

    2016-11-01

    The degree of crumpling affects the optoelectronic properties of graphene, which are very important for the performance of graphene-based devices and materials. In this article, we report an approach to tune the formation of wrinkles on single-layer graphene (SLG) by silicon nanopillar (SNP) arrays. By using gold nanoparticles as an etching mask, SNP arrays with different heights could be prepared by tuning the duration of etching. The formation of wrinkles on these SNP arrays was studied systematically. We found that thermal treatment could lead to a wrapping behavior of graphene around SNP arrays, which was accompanied by the emergence of many more wrinkles. Controllable wettability, conductivity and transmittance were demonstrated. This ability to tune wrinkles using SNP arrays can be employed to engineer the fabrication of graphene-related devices and other optoelectronic applications.

  1. Silicon Wafer-Scale Substrate for Microshutters and Detector Arrays

    NASA Technical Reports Server (NTRS)

    Jhabvala, Murzy; Franz, David E.; Ewin, Audrey J.; Jhabvala, Christine; Babu, Sachi; Snodgrass, Stephen; Costen, Nicholas; Zincke, Christian

    2009-01-01

    The silicon substrate carrier was created so that a large-area array (in this case 62,000+ elements of a microshutter array) and a variety of discrete passive and active devices could be mounted on a single board, similar to a printed circuit board. However, the density and number of interconnects far exceeds the capabilities of printed circuit board technology. To overcome this hurdle, a method was developed to fabricate this carrier out of silicon and implement silicon integrated circuit (IC) technology. This method achieves a large number of high-density metal interconnects; a 100-percent yield over a 6-in. (approximately equal to 15-cm) diameter wafer (one unit per wafer); a rigid, thermally compatible structure (all components and operating conditions) to cryogenic temperatures; re-workability and component replaceability, if required; and the ability to precisely cut large-area holes through the substrate. A method that would employ indium bump technology along with wafer-scale integration onto a silicon carrier was also developed. By establishing a silicon-based version of a printed circuit board, the objectives could be met with one solution. The silicon substrate would be 2 mm thick to survive the environmental loads of a launch. More than 2,300 metal traces and over 1,500 individual wire bonds are required. To mate the microshutter array to the silicon substrate, more than 10,000 indium bumps are required. A window was cut in the substrate to allow the light signal to pass through the substrate and reach the microshutter array. The substrate was also the receptacle for multiple unpackaged IC die wire-bonded directly to the substrate (thus conserving space over conventionally packaged die). Unique features of this technology include the implementation of a 2-mmthick silicon wafer to withstand extreme mechanical loads (from a rocket launch); integrated polysilicon resistor heaters directly on the substrate; the precise formation of an open aperture

  2. Flat-plate solar array project. Volume 2: Silicon material

    NASA Astrophysics Data System (ADS)

    Lutwack, R.

    1986-10-01

    The goal of the Silicon Material Task, a part of the Flat Plate Solar Array (FSA) Project, was to develop and demonstate the technology for the low cost production of silicon of suitable purity to be used as the basic material for the manufacture of terrestrial photovoltaic solar cells. Summarized are 11 different processes for the production of silicon that were investigated and developed to varying extent by industrial, university, and Government researchers. The silane production section of the Union Carbide Corp. (UCC) silane process was developed completely in this program. Coupled with Siemens-type chemical vapor deposition reactors, the process was carried through the pilot stage. The overall UCC process involves the conversion of metallurgical-grade silicon to silane followed by decomposition of the silane to purified silicon. The other process developments are described to varying extents. Studies are reported on the effects of impurities in silicon on both silicon-material properties and on solar cell performance. These studies on the effects of impurities yielded extensive information and models for relating specific elemental concentrations to levels of deleterious effects.

  3. Preparation of electrochemically active silicon nanotubes in highly ordered arrays.

    PubMed

    Grünzel, Tobias; Lee, Young Joo; Kuepper, Karsten; Bachmann, Julien

    2013-01-01

    Silicon as the negative electrode material of lithium ion batteries has a very large capacity, the exploitation of which is impeded by the volume changes taking place upon electrochemical cycling. A Si electrode displaying a controlled porosity could circumvent the difficulty. In this perspective, we present a preparative method that yields ordered arrays of electrochemically competent silicon nanotubes. The method is based on the atomic layer deposition of silicon dioxide onto the pore walls of an anodic alumina template, followed by a thermal reduction with lithium vapor. This thermal reduction is quantitative, homogeneous over macroscopic samples, and it yields amorphous silicon and lithium oxide, at the exclusion of any lithium silicides. The reaction is characterized by spectroscopic ellipsometry for thin silica films, and by nuclear magnetic resonance and X-ray photoelectron spectroscopy for nanoporous samples. After removal of the lithium oxide byproduct, the silicon nanotubes can be contacted electrically. In a lithium ion electrolyte, they then display the electrochemical waves also observed for other bulk or nanostructured silicon systems. The method established here paves the way for systematic investigations of how the electrochemical properties (capacity, charge/discharge rates, cyclability) of nanoporous silicon negative lithium ion battery electrode materials depend on the geometry.

  4. Flat-plate solar array project. Volume 2: Silicon material

    NASA Technical Reports Server (NTRS)

    Lutwack, R.

    1986-01-01

    The goal of the Silicon Material Task, a part of the Flat Plate Solar Array (FSA) Project, was to develop and demonstate the technology for the low cost production of silicon of suitable purity to be used as the basic material for the manufacture of terrestrial photovoltaic solar cells. Summarized are 11 different processes for the production of silicon that were investigated and developed to varying extent by industrial, university, and Government researchers. The silane production section of the Union Carbide Corp. (UCC) silane process was developed completely in this program. Coupled with Siemens-type chemical vapor deposition reactors, the process was carried through the pilot stage. The overall UCC process involves the conversion of metallurgical-grade silicon to silane followed by decomposition of the silane to purified silicon. The other process developments are described to varying extents. Studies are reported on the effects of impurities in silicon on both silicon-material properties and on solar cell performance. These studies on the effects of impurities yielded extensive information and models for relating specific elemental concentrations to levels of deleterious effects.

  5. Bandgap tuning of silicon nanowire arrays for application to all-silicon tandem solar cells

    NASA Astrophysics Data System (ADS)

    Kurokawa, Yasuyoshi; Yano, Mitsugu; Miyajima, Shinsuke; Yamada, Akira

    2017-04-01

    To reduce the diameter of silicon nanowire (SiNW) arrays for bandgap tuning, a diameter reduction (DR) process incorporating H3PO4 oxidation and HF etching was conducted for SiNW arrays with a diameter of 30 nm and a length of 15 µm. After the DR process, the diameter of SiNW arrays around the tip was successfully reduced to below 10 nm. From the cathode luminescence measurement, the bandgap around the tip of SiNW arrays was estimated to be 1.2 eV, suggesting that bandgap widening occurred owing to the quantum size effect.

  6. In Situ Real-Time Monitoring of Glutamate and Electrophysiology from Cortex to Hippocampus in Mice Based on a Microelectrode Array

    PubMed Central

    Fan, Xinyi; Song, Yilin; Ma, Yuanlin; Zhang, Song; Xiao, Guihua; Yang, Lili; Xu, Huiren; Zhang, Dai; Cai, Xinxia

    2016-01-01

    Changes in the structure and function of the hippocampus contribute to epilepsy, schizophrenia and other neurological or mental disorders of the brain. Since the function of the hippocampus depends heavily on the glutamate (Glu) signaling pathways, in situ real-time detection of Glu neurotransmitter release and electrophysiological signals in hippocampus is of great significance. To achieve the dual-mode detection in mouse hippocampus in vivo, a 16-channel implantable microelectrode array (MEA) was fabricated by micro-electromechanical system (MEMS) technology. Twelve microelectrode sites were modified with platinum black for electrophysiological recording and four sites were modified with glutamate oxidase (GluOx) and 1,3-phenylenediamine (mPD) for selective electrochemical detection of Glu. The MEA was implanted from cortex to hippocampus in mouse brain for in situ real-time monitoring of Glu and electrophysiological signals. It was found that the Glu concentration in hippocampus was roughly 50 μM higher than that in the cortex, and the firing rate of concurrently recorded spikes declined from 6.32 ± 4.35 spikes/s in cortex to 0.09 ± 0.06 spikes/s in hippocampus. The present results demonstrated that the dual-mode MEA probe was capable in neurological detections in vivo with high spatial resolution and dynamical response, which lays the foundation for further pathology studies in the hippocampus of mouse models with nervous or mental disorders. PMID:28042814

  7. Simultaneous recording of brain extracellular glucose, spike and local field potential in real time using an implantable microelectrode array with nano-materials

    NASA Astrophysics Data System (ADS)

    Wei, Wenjing; Song, Yilin; Fan, Xinyi; Zhang, Song; Wang, Li; Xu, Shengwei; Wang, Mixia; Cai, Xinxia

    2016-03-01

    Glucose is the main substrate for neurons in the central nervous system. In order to efficiently characterize the brain glucose mechanism, it is desirable to determine the extracellular glucose dynamics as well as the corresponding neuroelectrical activity in vivo. In the present study, we fabricated an implantable microelectrode array (MEA) probe composed of platinum electrochemical and electrophysiology microelectrodes by standard micro electromechanical system (MEMS) processes. The MEA probe was modified with nano-materials and implanted in a urethane-anesthetized rat for simultaneous recording of striatal extracellular glucose, local field potential (LFP) and spike on the same spatiotemporal scale when the rat was in normoglycemia, hypoglycemia and hyperglycemia. During these dual-mode recordings, we observed that increase of extracellular glucose enhanced the LFP power and spike firing rate, while decrease of glucose had an opposite effect. This dual mode MEA probe is capable of examining specific spatiotemporal relationships between electrical and chemical signaling in the brain, which will contribute significantly to improve our understanding of the neuron physiology.

  8. Arrays of ultrathin silicon solar microcells

    DOEpatents

    Rogers, John A; Rockett, Angus A; Nuzzo, Ralph; Yoon, Jongseung; Baca, Alfred

    2014-03-25

    Provided are solar cells, photovoltaics and related methods for making solar cells, wherein the solar cell is made of ultrathin solar grade or low quality silicon. In an aspect, the invention is a method of making a solar cell by providing a solar cell substrate having a receiving surface and assembling a printable semiconductor element on the receiving surface of the substrate via contact printing. The semiconductor element has a thickness that is less than or equal to 100 .mu.m and, for example, is made from low grade Si.

  9. Arrays of ultrathin silicon solar microcells

    SciTech Connect

    Rogers, John A.; Rockett, Angus A.; Nuzzo, Ralph; Yoon, Jongseung; Baca, Alfred

    2015-08-11

    Provided are solar cells, photovoltaics and related methods for making solar cells, wherein the solar cell is made of ultrathin solar grade or low quality silicon. In an aspect, the invention is a method of making a solar cell by providing a solar cell substrate having a receiving surface and assembling a printable semiconductor element on the receiving surface of the substrate via contact printing. The semiconductor element has a thickness that is less than or equal to 100 .mu.m and, for example, is made from low grade Si.

  10. Fabrication and size dependent properties of porous silicon nanotube arrays.

    PubMed

    Huang, Xuezhen; Gonzalez-Rodriguez, Roberto; Rich, Ryan; Gryczynski, Zygmunt; Coffer, Jeffery L

    2013-06-28

    A general method for the formation of a broad family of silicon nanotube arrays (Si NTAs) relevant to diverse fields--ranging from energy storage to therapeutic platforms--is described. Such nanotubes demonstrate a thickness-dependent dissolution behavior important to its potential use in drug delivery. Under selected conditions, novel porous silicon nanotubes can be prepared when the shell thickness is on the order of 12 nm or less, capable of being loaded with small molecules such as luminescent ruthenium dyes associated with dye-sensitized photovoltaic devices.

  11. Recent progress in patterned silicon nanowire arrays: fabrication, properties and applications.

    PubMed

    Zhang, Yan; Qiu, Teng; Zhang, Wenjun; Chu, Paul K

    2011-01-01

    Currently there is great interest in patterned silicon nanowire arrays and applications. The accurately controlled fabrication of patterned silicon nanowire arrays with the desirable axial crystallographic orientation using simpler and quicker ways is very desirable and of great importance to material synthesis and future nanoscale optoelectronic devices that employ silicon. The recent advances in manipulating patterned silicon nanowire arrays and patents are reviewed with a focus on the progress of nanowire fabrication and applications.

  12. Highly Flexible Silicone Coated Neural Array for Intracochlear Electrical Stimulation

    PubMed Central

    Bhatti, P.; Van Beek-King, J.; Sharpe, A.; Crawford, J.; Tridandapani, S.; McKinnon, B.; Blake, D.

    2015-01-01

    We present an effective method for tailoring the flexibility of a commercial thin-film polymer electrode array for intracochlear electrical stimulation. Using a pneumatically driven dispensing system, an average 232 ± 64 μm (mean ± SD) thickness layer of silicone adhesive coating was applied to stiffen the underside of polyimide multisite arrays. Additional silicone was applied to the tip to protect neural tissue during insertion and along the array to improve surgical handling. Each array supported 20 platinum sites (180 μm dia., 250 μm pitch), spanning nearly 28 mm in length and 400 μm in width. We report an average intracochlear stimulating current threshold of 170 ± 93 μA to evoke an auditory brainstem response in 7 acutely deafened felines. A total of 10 arrays were each inserted through a round window approach into the cochlea's basal turn of eight felines with one delamination occurring upon insertion (preliminary results of the in vivo data presented at the 48th Annual Meeting American Neurotology Society, Orlando, FL, April 2013, and reported in Van Beek-King 2014). Using microcomputed tomography imaging (50 μm resolution), distances ranging from 100 to 565 μm from the cochlea's central modiolus were measured. Our method combines the utility of readily available commercial devices with a straightforward postprocessing step on the order of 24 hours. PMID:26236714

  13. Large area, dense silicon nanowire array chemical sensors

    SciTech Connect

    Talin, A. Alec; Hunter, Luke L.; Leonard, Francois; Rokad, Bhavin

    2006-10-09

    The authors present a simple top-down approach based on nanoimprint lithography to create dense arrays of silicon nanowires over large areas. Metallic contacts to the nanowires and a bottom gate allow the operation of the array as a field-effect transistor with very large on/off ratios. When exposed to ammonia gas or cyclohexane solutions containing nitrobenzene or phenol, the threshold voltage of the field-effect transistor is shifted, a signature of charge transfer between the analytes and the nanowires. The threshold voltage shift is proportional to the Hammett parameter and the concentration of the nitrobenzene and phenol analytes.

  14. Detectors based on silicon photomultiplier arrays for medical imaging applications

    SciTech Connect

    Llosa, G.; Barrio, J.; Cabello, J.; Lacasta, C.; Oliver, J. F.; Stankova, V.; Solaz, C.

    2011-07-01

    Silicon photomultipliers (SiPMs) have experienced a fast development and are now employed in different research fields. The availability of 2D arrays that provide information of the interaction position in the detector has had a high interest for medical imaging. Continuous crystals combined with segmented photodetectors can provide higher efficiency than pixellated crystals and very high spatial resolution. The IRIS group at IFIC is working on the development of detector heads based on continuous crystals coupled to SiPM arrays for different applications, including a small animal PET scanner in collaboration with the Univ. of Pisa and INFN Pisa, and a Compton telescope for dose monitoring in hadron therapy. (authors)

  15. LASER DESORPTION IONIZATION MASS SPECTROMETRY ON SILICON NANOWELL ARRAYS

    PubMed Central

    Gulbakan, Basri; Park, Dooho; Kang, Myungchan; Kececi, Kaan; Martin, Charles R.; Powell, David H.; Tan, Weihong

    2010-01-01

    This paper describes a new technique for fabrication of nanostructured porous silicon (pSi) for laser desorption ionization mass spectrometry. Porous silicon nanowell arrays were prepared by argon plasma etching through an alumina mask. Porous silicon prepared in this way proved to be an excellent substrate for desorption/ionization on silicon (DIOS) mass spectrometry (MS) using adenosine, Pro-Leu-Gly tripeptide and [Des-Arg9]-bradykinin as the model compounds. It also allows the analyses of complex biological samples such as a tryptic digest of bovine serum albumin, and a carnitine standard mixture. Nanowell array surfaces were also used for direct quantification of the illicit drug fentanyl in red blood cell extracts. This method also allows full control of the surface features. MS results suggested that the pore depth has significant effect on the ion signals. Significant improvement in the ionization was observed by increasing the pore depth from 10 nm to 50 nm. These substrates are useful for laser desorption ionization in both the atmospheric pressure and vacuum regimes. PMID:20731384

  16. Laser desorption ionization mass spectrometry on silicon nanowell arrays.

    PubMed

    Gulbakan, Basri; Park, Dooho; Kang, Myungchan; Kececi, Kaan; Martin, Charles R; Powell, David H; Tan, Weihong

    2010-09-15

    This paper describes a new technique for fabrication of nanostructured porous silicon (pSi) for laser desorption ionization mass spectrometry. Porous silicon nanowell arrays were prepared by argon plasma etching through an alumina mask. Porous silicon prepared in this way proved to be an excellent substrate for desorption/ionization on silicon (DIOS) mass spectrometry (MS) using adenosine, Pro-Leu-Gly tripeptide, and [Des-Arg(9)]-bradykinin as the model compounds. It also allows the analyses of complex biological samples such as a tryptic digest of bovine serum albumin and a carnitine standard mixture. Nanowell array surfaces were also used for direct quantification of the illicit drug fentanyl in red blood cell extracts. This method also allows full control of the surface features. MS results suggested that the pore depth has a significant effect on the ion signals. Significant improvement in the ionization was observed by increasing the pore depth from 10 to 50 nm. These substrates are useful for laser desorption ionization in both the atmospheric pressure and vacuum regimes.

  17. Deployable aerospace PV array based on amorphous silicon alloys

    NASA Technical Reports Server (NTRS)

    Hanak, Joseph J.; Walter, Lee; Dobias, David; Flaisher, Harvey

    1989-01-01

    The development of the first commercial, ultralight, flexible, deployable, PV array for aerospace applications is discussed. It is based on thin-film, amorphous silicon alloy, multijunction, solar cells deposited on a thin metal or polymer by a proprietary, roll-to-roll process. The array generates over 200 W at AM0 and is made of 20 giant cells, each 54 cm x 29 cm (1566 sq cm in area). Each cell is protected with bypass diodes. Fully encapsulated array blanket and the deployment mechanism weigh about 800 and 500 g, respectively. These data yield power per area ratio of over 60 W/sq m specific power of over 250 W/kg (4 kg/kW) for the blanket and 154 W/kg (6.5 kg/kW) for the power system. When stowed, the array is rolled up to a diameter of 7 cm and a length of 1.11 m. It is deployed quickly to its full area of 2.92 m x 1.11 m, for instant power. Potential applications include power for lightweight space vehicles, high altitude balloons, remotely piloted and tethered vehicles. These developments signal the dawning of a new age of lightweight, deployable, low-cost space arrays in the range from tens to tens of thousands of watts for near-term applications and the feasibility of multi-100 kW to MW arrays for future needs.

  18. Deployable aerospace PV array based on amorphous silicon alloys

    NASA Astrophysics Data System (ADS)

    Hanak, Joseph J.; Walter, Lee; Dobias, David; Flaisher, Harvey

    1989-04-01

    The development of the first commercial, ultralight, flexible, deployable, PV array for aerospace applications is discussed. It is based on thin-film, amorphous silicon alloy, multijunction, solar cells deposited on a thin metal or polymer by a proprietary, roll-to-roll process. The array generates over 200 W at AM0 and is made of 20 giant cells, each 54 cm x 29 cm (1566 sq cm in area). Each cell is protected with bypass diodes. Fully encapsulated array blanket and the deployment mechanism weigh about 800 and 500 g, respectively. These data yield power per area ratio of over 60 W/sq m specific power of over 250 W/kg (4 kg/kW) for the blanket and 154 W/kg (6.5 kg/kW) for the power system. When stowed, the array is rolled up to a diameter of 7 cm and a length of 1.11 m. It is deployed quickly to its full area of 2.92 m x 1.11 m, for instant power. Potential applications include power for lightweight space vehicles, high altitude balloons, remotely piloted and tethered vehicles. These developments signal the dawning of a new age of lightweight, deployable, low-cost space arrays in the range from tens to tens of thousands of watts for near-term applications and the feasibility of multi-100 kW to MW arrays for future needs.

  19. Label-free enumeration of colorectal cancer cells from lymphocytes performed at a high cell-loading density by using interdigitated ring-array microelectrodes.

    PubMed

    Xing, Xiaoxing; Poon, Randy Y C; Wong, Cesar S C; Yobas, Levent

    2014-11-15

    We report the label-free enumeration of human colorectal-carcinoma cells from blood lymphocytes by using interdigitated ring-array microelectrodes; this enumeration was based on the dielectrophoretic selection of cells. Because of the novel design of the device, a continuous flow of cells is uniformly distributed into parallel streams through 300 rings (~40 μm in diameter each) that are integrated into the electrode digits. Using this array, 82% of cancer cells were recovered and 99% of blood lymphocytes were removed. Most of the cancer cells recovered were viable (94%) and could be cultivated for >8 days, during which period they retained their normal cell morphology and proliferation rates. The recovery rate correlated closely with cancer-cell loadings in spiked samples and this relationship was linear over a range of at least 2 orders of magnitude. Importantly, because of the 3D structure of the rings, these results were obtained at a high cell-loading concentration (10(7)cells/mL). The rings could be further optimized for use in accurate label-free identification and measurement of circulating tumor cells in cancer research and disease management.

  20. New approaches to eliminating common-noise artifacts in recordings from intracortical microelectrode arrays: inter-electrode correlation and virtual referencing

    PubMed Central

    Paralikar, Kunal J; Rao, Chinmay R; Clement, Ryan S

    2009-01-01

    Intracortical microelectrode arrays record multi-unit extracellular activity for neurophysiology studies and for brain-machine interface applications. The common first step is neural spike detection; a process complicated by common-noise signals from motion artifacts, electromyographic activity, and electric field pickup, especially in awake/behaving subjects. Often common-noise spikes are very similar to neural spikes in their magnitude, spectral, and temporal features. Provided sufficient spacing exists between electrodes of the array, a local neural spike is rarely recorded on multiple electrodes simultaneously. This is not true for distant common-noise sources. Two new techniques compatible with standard spike detection schemes are introduced and evaluated. The first method, virtual referencing (VR), takes the average recording from all functional electrodes in the array (represents the signal from a virtual electrode at the array's center) and subtracts it from the test electrode signal. The second method, inter-electrode correlation (IEC), computes a correlation coefficient between threshold exceeding candidate spike segments on the test electrode and concurrent segments from remaining electrodes. When sufficient correlation is detected, the candidate spike is rejected as originating from a distant common-noise source. The performance of these algorithms was compared with standard thresholding and differential referencing approaches using neural recordings from unanaesthetized rats. By evaluating characteristics of mean-spike waveforms generated by each method under different levels of common-noise, it was found that IEC consistently offered the most robust means of neural spike-detection. Furthermore, IEC's rejection of supra-threshold events not likely originating from local neurons significantly reduces data handling for downstream spike sorting and processing operations. PMID:19394363

  1. Covalent Attachment of Ferrocene to Silicon Microwire Arrays.

    PubMed

    Kang, Onkar S; Bruce, Jared P; Herbert, David E; Freund, Michael S

    2015-12-09

    A fully integrated, freestanding device for photoelectrochemical fuel generation will likely require covalent attachment of catalysts to the surface of the photoelectrodes. Ferrocene has been utilized in the past as a model system for molecular catalyst integration on planar silicon; however, the surface structure of high-aspect ratio silicon microwires envisioned for a potential device presents potential challenges with respect to stability, characterization, and mass transport. Attachment of vinylferrocene to Cl-terminated surfaces of silicon microwires was performed thermally. By varying the reaction time, solutions of vinylferrocene in di-n-butyl ether were employed to control the extent of functionalization. X-ray photoelectron spectroscopy (XPS) and electrochemistry were used to estimate the density and surface coverage of the silicon microwire arrays with ferrocenyl groups, which could be controllably varied from 1.23 × 10(-11) to 4.60 × 10(-10) mol cm(-2) or 1 to 30% of a monolayer. Subsequent backfill of the remaining Si-Cl sites with methyl groups produced ferrocenyl-terminated surfaces that showed unchanged cyclic volammograms following two months in air, under ambient conditions, and repeated electrochemical cycling.

  2. Review of machine learning and signal processing techniques for automated electrode selection in high-density microelectrode arrays.

    PubMed

    Van Dijck, Gert; Van Hulle, Marc M

    2014-08-01

    Recently developed CMOS-based microprobes contain hundreds of electrodes on a single shaft with interelectrode distances as small as 30 µm. So far, neuroscientists manually select a subset of those electrodes depending on their appraisal of the "usefulness" of the recorded signals, which makes the process subjective but more importantly too time consuming to be useable in practice. The ever-increasing number of recording electrodes on microelectrode probes calls for an automated selection of electrodes containing "good quality signals" or "signals of interest." This article reviews the different criteria for electrode selection as well as the basic signal processing steps to prepare the data to compute those criteria. We discuss three of them. The first two select the electrodes based on "signal quality." The first criterion computes the penalized signal-to-noise ratio (SNR); the second criterion models the neuroscientist's appraisal of signal quality. Last, our most recent work allows the selection of electrodes that capture particular anatomical cell types. The discussed algorithms perform what is called in the literature "electronic depth control" in contrast to the mechanical repositioning of the electrode shafts in search of "good quality signals" or "signals of interest."

  3. Amorphous silicon cell array powered solar tracking apparatus

    DOEpatents

    Hanak, Joseph J.

    1985-01-01

    An array of an even number of amorphous silicon solar cells are serially connected between first and second terminals of opposite polarity. The terminals are connected to one input terminal of a DC motor whose other input terminal is connected to the mid-cell of the serial array. Vane elements are adjacent the end cells to selectively shadow one or the other of the end cells when the array is oriented from a desired attitude relative to the sun. The shadowing of one cell of a group of cells on one side of the mid-cell reduces the power of that group substantially so that full power from the group of cells on the other side of the mid-cell drives the motor to reorient the array to the desired attitude. The cell groups each have a full power output at the power rating of the motor. When the array is at the desired attitude the power output of the two groups of cells balances due to their opposite polarity so that the motor remains unpowered.

  4. Properties of Retinal Precursor Cells Grown on Vertically Aligned Multiwalled Carbon Nanotubes Generated for the Modification of Retinal Implant-Embedded Microelectrode Arrays

    PubMed Central

    Johnen, Sandra; Meißner, Frank; Krug, Mario; Baltz, Thomas; Endler, Ingolf; Mokwa, Wilfried; Walter, Peter

    2016-01-01

    Background. To analyze the biocompatibility of vertically aligned multiwalled carbon nanotubes (MWCNT), used as nanomodification to optimize the properties of prostheses-embedded microelectrodes that induce electrical stimulation of surviving retinal cells. Methods. MWCNT were synthesized on silicon wafers. Their growth was achieved by iron particles (Fe) or mixtures of iron-platinum (Fe-Pt) and iron-titanium (Fe-Ti) acting as catalysts. Viability, growth, adhesion, and gene expression of L-929 and retinal precursor (R28) cells were analyzed after nondirect and direct contact. Results. Nondirect contact had almost no influence on cell growth, as measured in comparison to reference materials with defined levels of cytotoxicity. Both cell types exhibited good proliferation properties on each MWCNT-coated wafer. Viability ranged from 95.9 to 99.8%, in which better survival was observed for nonfunctionalized MWCNT generated with the Fe-Pt and Fe-Ti catalyst mixtures. R28 cells grown on the MWCNT-coated wafers showed a decreased gene expression associated with neural and glial properties. Expression of the cell cycle-related genes CCNC, MYC, and TP53 was slightly downregulated. Cultivation on plasma-treated MWCNT did not lead to additional changes. Conclusions. All tested MWCNT-covered slices showed good biocompatibility profiles, confirming that this nanotechnology is a promising tool to improve prostheses bearing electrodes which connect with retinal tissue. PMID:27200182

  5. Microelectrodes integrated cell-chip for drug effects study

    NASA Astrophysics Data System (ADS)

    Chen, Yu; Cui, Hui-Fang; Ye, Jian-Shan; Chong, Ser-Choong; Lim, Tit-Meng; Sheu, Fwu-Shan; Cheong, Hui-Wing

    2006-01-01

    Silicon-based microelectrode chips are useful tools for temporal recording of neurotransmitter releasing from neural cells. Both invasive and non-invasive methods are targeted by different group researchers to perform electrical stimulating on neural cells. A microfabricated microelectrodes integrated biochip will be presented in this paper, which describes the dopaminergic cells growing on the chip directly. The dopamine exocytosis can be detected non-invasively from drug incubated dopaminergic cells growing on the chip. The abovementioned silicon-based electrochemical sensor chip has been designed with an electrode array located on the bottom of reaction chamber and each electrode is individually electrical controlled. MN9D, a mouse mesencephalic dopaminergic cell line, has been grown on the surface of the biochip chamber directly. Dopamine exocytosis from the chip-grown MN9D cells was detected using amperometry technology. The amperometric detection limit of dopamine of the biochip microelectrodes was found from 0.06μM to 0.21μM (S/N=3) statistically for the electrode diameters from 10 μm to 90 μm, the level of dopamine exocytosis from MN9D cells was undetectable whithout drug incubation. In contrast, after MN9D cells were incubated with L-dopa, a dopamine precursor, K+ induced dopamine extocytosis was temporally detected. The microelectrodes integrated biochip provides a non-invasive, temporal detection of dopamine exocytosis from dopaminergic cells, and holds the potential for applications in studying the mechanisms of dopamine exocytosis, and drug screening. It also provides a tool for pharmaceutical research and drug screening on dopaminergic cells, extendably to be used for other cell culture and drug effects study.

  6. Array Automated Assembly Task Low Cost Silicon Solar Array Project, Phase 2

    NASA Technical Reports Server (NTRS)

    Rhee, S. S.; Jones, G. T.; Allison, K. L.

    1978-01-01

    Progress in the development of solar cells and module process steps for low-cost solar arrays is reported. Specific topics covered include: (1) a system to automatically measure solar cell electrical performance parameters; (2) automation of wafer surface preparation, printing, and plating; (3) laser inspection of mechanical defects of solar cells; and (4) a silicon antireflection coating system. Two solar cell process steps, laser trimming and holing automation and spray-on dopant junction formation, are described.

  7. Composite silicon nanostructure arrays fabricated on optical fibre by chemical etching of multicrystal silicon film

    NASA Astrophysics Data System (ADS)

    Zuo, Zewen; Zhu, Kai; Ning, Lixin; Cui, Guanglei; Qu, Jun; Huang, Wanxia; Shi, Yi; Liu, Hong

    2015-04-01

    Integrating nanostructures onto optical fibers presents a promising strategy for developing new-fashioned devices and extending the scope of nanodevices’ applications. Here we report the first fabrication of a composite silicon nanostructure on an optical fiber. Through direct chemical etching using an H2O2/HF solution, multicrystal silicon films with columnar microstructures are etched into a vertically aligned, inverted-cone-like nanorod array embedded in a nanocone array. A faster dissolution rate of the silicon at the void-rich boundary regions between the columns is found to be responsible for the separation of the columns, and thus the formation of the nanostructure array. The morphology of the nanorods primarily depends on the microstructure of the columns in the film. Through controlling the microstructure of the as-grown film and the etching parameters, the structural control of the nanostructure is promising. This fabrication method can be extended to a larger length scale, and it even allows roll-to-roll processing.

  8. Copper nanorod array assisted silicon waveguide polarization beam splitter.

    PubMed

    Kim, Sangsik; Qi, Minghao

    2014-04-21

    We present the design of a three-dimensional (3D) polarization beam splitter (PBS) with a copper nanorod array placed between two silicon waveguides. The localized surface plasmon resonance (LSPR) of a metal nanorod array selectively cross-couples transverse electric (TE) mode to the coupler waveguide, while transverse magnetic (TM) mode passes through the original input waveguide without coupling. An ultra-compact and broadband PBS compared to all-dielectric devices is achieved with the LSPR. The output ports of waveguides are designed to support either TM or TE mode only to enhance the extinction ratios. Compared to silver, copper is fully compatible with complementary metal-oxide-semiconductor (CMOS) technology.

  9. High performance silicon solar arrays employing advanced structures

    NASA Technical Reports Server (NTRS)

    Rockey, D. E.; Hedgepeth, J. M.; Adams, L.

    1981-01-01

    Specific design features to reduce cell mass, lower panel operating temperatures, and improve power to mass ratios for silicon solar cell arrays in space applications are presented. Because mass constraints limit payload capacity for launch into GEO, graphite/epoxy structures combined with high performance Si cells are needed to deliver a power/mass ratio of 265 W/kg, notably for Solar Electric Propulsion systems, compared with existing level of 65 W/kg. Shallow diffusion and back surface field cell technology have raised cell efficiencies to 15%, with a back emissivity of 1.64. Structural design requirements comprise Shuttle interface compatibility, full ground test capability, low mass, and high stiffness. Three array alternatives are discussed, and the STACBEAM configuration, which consists of a triangular truss and a piston deployer with folding accomplished on simple hinges, provides 0.2 Hz stiffness and achieves the design power/mass goals.

  10. Copper nanorod array assisted silicon waveguide polarization beam splitter

    PubMed Central

    Kim, Sangsik; Qi, Minghao

    2014-01-01

    We present the design of a three-dimensional (3D) polarization beam splitter (PBS) with a copper nanorod array placed between two silicon waveguides. The localized surface plasmon resonance (LSPR) of a metal nanorod array selectively cross-couples transverse electric (TE) mode to the coupler waveguide, while transverse magnetic (TM) mode passes through the original input waveguide without coupling. An ultra-compact and broadband PBS compared to all-dielectric devices is achieved with the LSPR. The output ports of waveguides are designed to support either TM or TE mode only to enhance the extinction ratios. Compared to silver, copper is fully compatible with complementary metal-oxide-semiconductor (CMOS) technology. PMID:24787839

  11. Synthesis and characterization of silicon nanowire arrays for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Eichfeld, Sarah M.

    The overall objective of this thesis was the development of processes for the fabrication of radial p-n silicon nanowires (SiNWs) using bottom-up nanowire growth techniques on silicon and glass substrates. Vapor-liquid-solid (VLS) growth was carried out on Si(111) substrates using SiCl4 as the silicon precursor. Growth conditions including temperature, PSiCl4, PH2, and position were investigated to determine the optimum growth conditions for epitaxially oriented silicon nanowire arrays. The experiments revealed that the growth rate of the silicon nanowires exhibits a maximum as a function of PSiCl4 and P H2. Gas phase equilibrium calculations were used in conjunction with a mass transport model to explain the experimental data. The modeling results demonstrate a similar maximum in the mass of solid silicon predicted to form as a function of PSiCl4 and PH2, which results from a change in the gas phase concentration of SiHxCly and SiClx species. This results in a shift in the process from growth to etching with increasing PSiCl4. In general, for the atmospheric pressure conditions employed in this study, growth at higher temperatures >1000°C and higher SiCl4 concentrations gave the best results. The growth of silicon nanowire arrays on anodized alumina (AAO)-coated glass substrates was also investigated. Glass will not hold up to the high temperatures required for Si nanowire growth with SiCl4 so SiH 4 was used as the Si precursor instead. Initial studies were carried out to measure the resistivity of p-type and n-type silicon nanowires grown in freestanding AAO membranes. A series of nanowire samples were grown in which the doping and the nanowire length inside the membrane were varied. Circular metal contacts were deposited on the top surface of the membranes and the resistance of the nanowire arrays was measured. The measured resistance versus nanowire length was plotted and the nanowire resistivity was extracted from the slope. The resistivity of the silicon

  12. High-throughput PCR in silicon based microchamber array.

    PubMed

    Nagai, H; Murakami, Y; Yokoyama, K; Tamiya, E

    2001-12-01

    Highly integrated hybridization assay and capillary electrophoresis have improved the throughput of DNA analysis. The shift to high throughput analysis requires a high speed DNA amplification system, and several rapid PCR systems have been developed. In these thermal cyclers, the temperature was controlled by effective methodology instead of a large heating/cooling block preventing rapid thermal cycling. In our research, high speed PCR was performed using a silicon-based microchamber array and three heat blocks. The highly integrated microchamber array was fabricated by semiconductor microfabrication techniques. The temperature of the PCR microchamber was controlled by alternating between three heat blocks of different temperature. In general, silicon has excellent thermal conductivity, and the heat capacity is small in the miniaturized sample volume. Hence, the heating/cooling rate was rapid, approximately 16 degrees C/s. The rapid PCR was therefore completed in 18 min for 40 cycles. The thermal cycle time was reduced to 1/10 of a commercial PCR instrument (Model 9600, PE Applied Biosystems-3 h).

  13. Synthesis and Photoluminescence Properties of Porous Silicon Nanowire Arrays.

    PubMed

    Lin, Linhan; Guo, Siping; Sun, Xianzhong; Feng, Jiayou; Wang, Yan

    2010-08-05

    Herein, we prepare vertical and single crystalline porous silicon nanowires (SiNWs) via a two-step metal-assisted electroless etching method. The porosity of the nanowires is restricted by etchant concentration, etching time and doping lever of the silicon wafer. The diffusion of silver ions could lead to the nucleation of silver nanoparticles on the nanowires and open new etching ways. Like porous silicon (PS), these porous nanowires also show excellent photoluminescence (PL) properties. The PL intensity increases with porosity, with an enhancement of about 100 times observed in our condition experiments. A "red-shift" of the PL peak is also found. Further studies prove that the PL spectrum should be decomposed into two elementary PL bands. The peak at 850 nm is the emission of the localized excitation in the nanoporous structure, while the 750-nm peak should be attributed to the surface-oxidized nanostructure. It could be confirmed from the Fourier transform infrared spectroscopy analyses. These porous SiNW arrays may be useful as the nanoscale optoelectronic devices.

  14. A Low-Noise, Modular, and Versatile Analog Front-End Intended for Processing In Vitro Neuronal Signals Detected by Microelectrode Arrays

    PubMed Central

    Regalia, Giulia; Biffi, Emilia; Ferrigno, Giancarlo; Pedrocchi, Alessandra

    2015-01-01

    The collection of good quality extracellular neuronal spikes from neuronal cultures coupled to Microelectrode Arrays (MEAs) is a binding requirement to gather reliable data. Due to physical constraints, low power requirement, or the need of customizability, commercial recording platforms are not fully adequate for the development of experimental setups integrating MEA technology with other equipment needed to perform experiments under climate controlled conditions, like environmental chambers or cell culture incubators. To address this issue, we developed a custom MEA interfacing system featuring low noise, low power, and the capability to be readily integrated inside an incubator-like environment. Two stages, a preamplifier and a filter amplifier, were designed, implemented on printed circuit boards, and tested. The system is characterized by a low input-referred noise (<1 μV RMS), a high channel separation (>70 dB), and signal-to-noise ratio values of neuronal recordings comparable to those obtained with the benchmark commercial MEA system. In addition, the system was successfully integrated with an environmental MEA chamber, without harming cell cultures during experiments and without being damaged by the high humidity level. The devised system is of practical value in the development of in vitro platforms to study temporally extended neuronal network dynamics by means of MEAs. PMID:25977683

  15. A Framework for the Comparative Assessment of Neuronal Spike Sorting Algorithms towards More Accurate Off-Line and On-Line Microelectrode Arrays Data Analysis.

    PubMed

    Regalia, Giulia; Coelli, Stefania; Biffi, Emilia; Ferrigno, Giancarlo; Pedrocchi, Alessandra

    2016-01-01

    Neuronal spike sorting algorithms are designed to retrieve neuronal network activity on a single-cell level from extracellular multiunit recordings with Microelectrode Arrays (MEAs). In typical analysis of MEA data, one spike sorting algorithm is applied indiscriminately to all electrode signals. However, this approach neglects the dependency of algorithms' performances on the neuronal signals properties at each channel, which require data-centric methods. Moreover, sorting is commonly performed off-line, which is time and memory consuming and prevents researchers from having an immediate glance at ongoing experiments. The aim of this work is to provide a versatile framework to support the evaluation and comparison of different spike classification algorithms suitable for both off-line and on-line analysis. We incorporated different spike sorting "building blocks" into a Matlab-based software, including 4 feature extraction methods, 3 feature clustering methods, and 1 template matching classifier. The framework was validated by applying different algorithms on simulated and real signals from neuronal cultures coupled to MEAs. Moreover, the system has been proven effective in running on-line analysis on a standard desktop computer, after the selection of the most suitable sorting methods. This work provides a useful and versatile instrument for a supported comparison of different options for spike sorting towards more accurate off-line and on-line MEA data analysis.

  16. The use of microelectrode array (MEA) to study the protective effects of potassium channel openers on metabolically compromised HL-1 cardiomyocytes.

    PubMed

    Law, J K Y; Yeung, C K; Hofmann, B; Ingebrandt, S; Rudd, J A; Offenhäusser, A; Chan, M

    2009-02-01

    The microelectrode array (MEA) was used to evaluate the cardioprotective effects of adenosine triphosphate sensitive potassium (K(ATP)) channel activation using potassium channel openers (KCOs) on HL-1 cardiomyocytes subjected to acute chemically induced metabolic inhibition. Beat frequency and extracellular action potential (exAP) amplitude were measured in the presence of metabolic inhibitors (sodium azide (NaN(3)) or 2-deoxyglucose (2-DG)) or KCOs (pinacidil (PIN, a cyanoguanidine derivative, activates sarcolemmal K(ATP) channels) or SDZ PCO400 (SDZ, a benzopyran derivative, activates mitochondrial K(ATP) channels)). The protective effects of these KCOs on metabolically inhibited HL-1 cells were subsequently investigated. Signal shapes indicated that NaN(3) and 2-DG reduced the rate of the sodium (Na(+)) influx signal as reflected by a reduction in beat frequency. PIN and SDZ appeared to reduce both rate of depolarization and extent of the Na(+) influx signals. Pre-treating cardiomyocytes with PIN (0.1 mM), but not SDZ, prevented the reduction of beat frequency associated with NaN(3)- or 2-DG-induced metabolic inhibition. The exAP amplitude was not affected by either KCO. The cardioprotective effect of PIN relative to SDZ may be due to the opening of different K(ATP) channels. This metabolic inhibition model on the MEA may provide a stable platform for the study of cardiac pathophysiology in the future.

  17. Vascular lumen simulation and highly-sensitive nitric oxide detection using three-dimensional gelatin chip coupled to TiC/C nanowire arrays microelectrode.

    PubMed

    Li, Lin-Mei; Wang, Xue-Ying; Hu, Liang-Sheng; Chen, Rong-Sheng; Huang, Ying; Chen, Shi-Jing; Huang, Wei-Hua; Huo, Kai-Fu; Chu, Paul K

    2012-11-07

    Reproducing the physiological environment of blood vessels for the in vitro investigation of endothelial cell functions is very challenging. Here, we describe a vascular-like structure based on a three-dimensional (3D) gelatin chip with good compatibility and permeability which is also cost-effective and easy to produce. The controllable lumen diameter and wall thickness enable close mimicking of blood vessels in vitro. The 3D gelatin matrix between adjacent lumens is capable of generating soluble-factor gradients inside, and diffusion of molecules with different molecular weights through the matrix is studied. The cultured human umbilical vein endothelial cells proliferate on the gelatin lumen linings to form a vascular lumen. The hemodynamic behavior including adhesion, alignment of endothelial cells (ECs) under shear stress and pulsatile stretch is studied. Furthermore, a microelectrode comprising TiC/C nanowire arrays is fabricated to detect nitric oxide with sub-nM detection limits and NO generation from the cultured ECs is monitored in real time. This vascular model reproduces the surrounding parenchyma of endothelial cells and mimics the hemodynamics inside blood vessels very well, thereby enabling potential direct investigation of hemodynamics, angiogenesis, and tumor metastasis in vitro.

  18. Incubator-independent cell-culture perfusion platform for continuous long-term microelectrode array electrophysiology and time-lapse imaging

    PubMed Central

    Saalfrank, Dirk; Konduri, Anil Krishna; Latifi, Shahrzad; Habibey, Rouhollah; Golabchi, Asiyeh; Martiniuc, Aurel Vasile; Knoll, Alois; Ingebrandt, Sven; Blau, Axel

    2015-01-01

    Most in vitro electrophysiology studies extract information and draw conclusions from representative, temporally limited snapshot experiments. This approach bears the risk of missing decisive moments that may make a difference in our understanding of physiological events. This feasibility study presents a simple benchtop cell-culture perfusion system adapted to commercial microelectrode arrays (MEAs), multichannel electrophysiology equipment and common inverted microscopy stages for simultaneous and uninterrupted extracellular electrophysiology and time-lapse imaging at ambient CO2 levels. The concept relies on a transparent, replica-casted polydimethylsiloxane perfusion cap, gravity- or syringe-pump-driven perfusion and preconditioning of pH-buffered serum-free cell-culture medium to ambient CO2 levels at physiological temperatures. The low-cost microfluidic in vitro enabling platform, which allows us to image cultures immediately after cell plating, is easy to reproduce and is adaptable to the geometries of different cell-culture containers. It permits the continuous and simultaneous multimodal long-term acquisition or manipulation of optical and electrophysiological parameter sets, thereby considerably widening the range of experimental possibilities. Two exemplary proof-of-concept long-term MEA studies on hippocampal networks illustrate system performance. Continuous extracellular recordings over a period of up to 70 days revealed details on both sudden and gradual neural activity changes in maturing cell ensembles with large intra-day fluctuations. Correlated time-lapse imaging unveiled rather static macroscopic network architectures with previously unreported local morphological oscillations on the timescale of minutes. PMID:26543581

  19. Simultaneous determination and speciation of zinc, cadmium, lead, and copper in natural water with minimum handling and artifacts, by voltammetry on a gel-integrated microelectrode array.

    PubMed

    Pei, J; Tercier-Waeber, M L; Buffle, J

    2000-01-01

    The paper reports a new approach based on a gel-integrated Hg-plated-Ir-based microelectrode array (GIME), for measuring Cu, Pb, Cd, and Zn speciation in natural waters. This paper focuses on the quantitative discrimination between mobile and colloidal metal species (size limit of a few nanometers), for which most classical separation techniques present severe drawbacks. Previous papers have shown qualitatively that GIME combined with square wave anodic stripping voltammetry (SWASV) has the basic characteristics required to discriminate between these two fractions directly on the unperturbed sample. In addition, because of the large sensitivity provided by GIME, complexation parameters (equilibrium constants and site concentrations) can be determined in little-perturbed samples, particularly without metal addition or with small addition compared with natural concentrations. The advantages of this procedure are exemplified and the possible artifacts occurring when titrating the sample with metals, in particular intermetallic compound formation and other problems, are discussed in detail. The present paper shows that the characteristics of GIME make it a unique tool to get quantitative information on metal speciation at nanomolar or even subnanomolar levels, with only minor sample handling.

  20. In-Vivo Characterization of Glassy Carbon Micro-Electrode Arrays for Neural Applications and Histological Analysis of the Brain Tissue

    NASA Astrophysics Data System (ADS)

    Vomero, Maria

    The aim of this work is to fabricate and characterize glassy carbon Microelectrode Arrays (MEAs) for sensing and stimulating neural activity, and conduct histological analysis of the brain tissue after the implant to determine long-term performance. Neural applications often require robust electrical and electrochemical response over a long period of time, and for those applications we propose to replace the commonly used noble metals like platinum, gold and iridium with glassy carbon. We submit that such material has the potential to improve the performances of traditional neural prostheses, thanks to better charge transfer capabilities and higher electrochemical stability. Great interest and attention is given in this work, in particular, to the investigation of tissue response after several weeks of implants in rodents' brain motor cortex and the associated materials degradation. As part of this work, a new set of devices for Electrocorticography (ECoG) has been designed and fabricated to improve durability and quality of the previous generation of devices, designed and manufactured by the same research group in 2014. In-vivo long-term impedance measurements and brain activity recordings were performed to test the functionality of the neural devices. In-vitro electrical characterization of the carbon electrodes, as well as the study of the adhesion mechanisms between glassy carbon and different substrates is also part of the research described in this book.

  1. A movable microelectrode array for chronic basal ganglia single-unit electrocorticogram co-recording in freely behaving rats.

    PubMed

    Zheng, Xiaobin; Zeng, Jia; Chen, Ting; Lin, Yuanxiang; Yu, Lianghong; Li, Ying; Lin, Zhangya; Wu, Xiyue; Chen, Fuyong; Kang, Dezhi; Zhang, Shizhong

    2014-09-01

    The basal ganglia-cortical circuits are important for information process to brain function. However, chronic recording of single-unit activities in the basal ganglia nucleus has not yet been well established. We present a movable bundled microwire array for chronic subthalamic nucleus (STN) single-unit electrocorticogram co-recording. The electrode assembly contains a screw-advanced microdrive and a microwire array. The array consists of a steel guide tube, five recording wires and one referenced wire which form the shape of a guiding hand, and one screw electrode for cortico-recording. The electrode can acquire stable cortex oscillation-driven STN firing units in rats under different behaving conditions for 8 weeks. We achieved satisfying signal-to-noise ratio, portions of cells retaining viability, and spike waveform similarities across the recording sections. Using this method, we investigated neural correlations of the basal ganglia-cortical circuits in different behaving conditions. This method will become a powerful tool for multi-region recording to study normal statements or movement disorders.

  2. Smart integration of silicon nanowire arrays in all-silicon thermoelectric micro-nanogenerators

    NASA Astrophysics Data System (ADS)

    Fonseca, Luis; Santos, Jose-Domingo; Roncaglia, Alberto; Narducci, Dario; Calaza, Carlos; Salleras, Marc; Donmez, Inci; Tarancon, Albert; Morata, Alex; Gadea, Gerard; Belsito, Luca; Zulian, Laura

    2016-08-01

    Micro and nanotechnologies are called to play a key role in the fabrication of small and low cost sensors with excellent performance enabling new continuous monitoring scenarios and distributed intelligence paradigms (Internet of Things, Trillion Sensors). Harvesting devices providing energy autonomy to those large numbers of microsensors will be essential. In those scenarios where waste heat sources are present, thermoelectricity will be the obvious choice. However, miniaturization of state of the art thermoelectric modules is not easy with the current technologies used for their fabrication. Micro and nanotechnologies offer an interesting alternative considering that silicon in nanowire form is a material with a promising thermoelectric figure of merit. This paper presents two approaches for the integration of large numbers of silicon nanowires in a cost-effective and practical way using only micromachining and thin-film processes compatible with silicon technologies. Both approaches lead to automated physical and electrical integration of medium-high density stacked arrays of crystalline or polycrystalline silicon nanowires with arbitrary length (tens to hundreds microns) and diameters below 100 nm.

  3. Design, theoretical analysis, and experimental verification of a CMOS current integrator with 1.2 × 2.05 µm2 microelectrode array for high-sensitivity bacterial counting

    NASA Astrophysics Data System (ADS)

    Gamo, Kohei; Nakazato, Kazuo; Niitsu, Kiichi

    2017-01-01

    In this paper, we present the design and experimental verification of an amperometric CMOS-based sensor with a current integrator and a 1.2 × 2.05 µm2 bacterial-sized microelectrode array for high-sensitivity bacterial counting. For high-sensitivity bacterial counting with a sufficient signal-to-noise ratio (SNR), noise must be reduced because bacterial-sized microelectrodes can handle only a low current of the order of 100 pA. Thus, we implement a current integrator that is highly effective for noise reduction. Furthermore, for the first time, we use the current integrator in conjunction with the bacterial-sized microelectrode array. On the basis of the results of the proposed current integration, we successfully reduce noise and achieve a high SNR of 30.4 dB. To verify the effectiveness of the proposed CMOS-based sensor, we perform two-dimensional counting of microbeads, which are almost of the same size as bacteria. The measurement results demonstrate successful high-sensitivity two-dimensional (2D) counting of microbeads with a high SNR of 27 dB.

  4. Enhanced sub-micron colloidal particle separation with interdigitated microelectrode arrays using mixed AC/DC dielectrophoretic scheme.

    PubMed

    Swaminathan, Vikhram V; Shannon, Mark A; Bashir, Rashid

    2015-04-01

    Dielectrophoretic separation of particles finds a variety of applications in the capture of species such as cells, viruses, proteins, DNA from biological systems, as well as other organic and inorganic contaminants from water. The ability to capture particles is constrained by poor volumetric scaling of separation force with respect to particle diameter, as well as the weak penetration of electric fields in the media. In order to improve the separation of sub-micron colloids, we present a scheme based on multiple interdigitated electrode arrays under mixed AC/DC bias. The use of high frequency longitudinal AC bias breaks the shielding effects through electroosmotic micromixing to enhance electric fields through the electrolyte, while a transverse DC bias between the electrode arrays enables penetration of the separation force to capture particles from the bulk of the microchannel. We determine the favorable biasing conditions for field enhancement with the help of analytical models, and experimentally demonstrate the improved capture from sub-micron colloidal suspensions with the mixed AC/DC electrostatic excitation scheme over conventional AC-DEP methods.

  5. Electroassisted transfer of vertical silicon wire arrays using a sacrificial porous silicon layer.

    PubMed

    Weisse, Jeffrey M; Lee, Chi Hwan; Kim, Dong Rip; Cai, Lili; Rao, Pratap M; Zheng, Xiaolin

    2013-09-11

    An electroassisted method is developed to transfer silicon (Si) wire arrays from the Si wafers on which they are grown to other substrates while maintaining their original properties and vertical alignment. First, electroassisted etching is used to form a sacrificial porous Si layer underneath the Si wires. Second, the porous Si layer is separated from the Si wafer by electropolishing, enabling the separation and transfer of the Si wires. The method is further expanded to develop a current-induced metal-assisted chemical etching technique for the facile and rapid synthesis of Si nanowires with axially modulated porosity.

  6. Silicon technologies for arrays of Single Photon Avalanche Diodes

    PubMed Central

    Ceccarelli, Francesco; Rech, Ivan; Ghioni, Massimo

    2016-01-01

    In order to fulfill the requirements of many applications, we recently developed a new technology aimed at combining the advantages of traditional thin and thick silicon Single Photon Avalanche Diodes (SPAD). In particular we demonstrated single-pixel detectors with a remarkable improvement in the Photon Detection Efficiency in the red/near-infrared spectrum (e.g. 40% at 800nm) while maintaining a timing jitter better than 100ps. In this paper we discuss the limitations of such Red-Enhanced (RE) technology from the point of view of the fabrication of small arrays of SPAD and we propose modifications to the structure aimed at overcoming these issues. We also report the first preliminary experimental results attained on devices fabricated adopting the improved structure. PMID:27761058

  7. Non-invasive long-term and real-time analysis of endocrine cells on micro-electrode arrays

    PubMed Central

    Raoux, Matthieu; Bornat, Yannick; Quotb, Adam; Catargi, Bogdan; Renaud, Sylvie; Lang, Jochen

    2012-01-01

    Non-invasive high-throughput and long-term monitoring of endocrine cells is important for drug research, phenotyping, tissue engineering and pre-transplantation quality control. Here we report a novel approach to obtain simultaneous long-term electrical recordings of different islet cell types using multi-electrode arrays. We implemented wavelet transforms to resolve the low signal/noise ratio inherent to these measurements and extracted on-line a signature specific of cell activity. The architecture employed allows multiplexing a large number of electrodes for high-throughput screening. This method should be of considerable advantage in endocrine research and may be extended to other excitable cells previously not accessible to the technique. PMID:22199167

  8. A Label-Free Microelectrode Array Based on One-Step Synthesis of Chitosan–Multi-Walled Carbon Nanotube–Thionine for Ultrasensitive Detection of Carcinoembryonic Antigen

    PubMed Central

    Xu, Huiren; Wang, Yang; Wang, Li; Song, Yilin; Luo, Jinping; Cai, Xinxia

    2016-01-01

    Carcinoembryonic antigen (CEA) has been an extensively used tumor marker responsible for clinical early diagnosis of cervical carcinomas, and pancreatic, colorectal, gastric and lung cancer. Combined with micro-electro mechanical system (MEMS) technology, it is important to develop a novel immune microelectrode array (MEA) not only for rapid analysis of serum samples, but also for cell detection in vitro and in vivo. In this work, we depict a simple approach to modify chitosan–multi-walled carbon nanotubes–thionine (CS–MWCNTs–THI) hybrid film through one-step electrochemical deposition and the CS-MWCNTs-THI hybrid films are successfully employed to immobilize anti-CEA for fabricating simple, label-free, and highly sensitive electro-chemical immune MEAs. The detection principle of immune MEA was based on the fact that the increasing formation of the antigen-antibody immunocomplex resulted in the decreased response currents and the relationship between the current reductions with the corresponding CEA concentrations was directly proportional. Experimental results indicated that the label-free MEA had good selectivity and the limit of detection for CEA is 0.5 pg/mL signal to noise ratio (SNR) = 3. A linear calibration plot for the detection of CEA was obtained in a wide concentration range from 1 pg/mL to 100 ng/mL (r = 0.996). This novel MEA has potential applications for detecting CEA for the research on cancer cells and cancer tissue slices as well as for effective early diagnosis. PMID:28335260

  9. Interdigitated array microelectrode based impedance biosensor coupled with magnetic nanoparticle-antibody conjugates for detection of Escherichia coli O157:H7 in food samples.

    PubMed

    Varshney, Madhukar; Li, Yanbin

    2007-05-15

    An impedance biosensor based on interdigitated array microelectrode (IDAM) coupled with magnetic nanoparticle-antibody conjugates (MNAC) was developed and evaluated for rapid and specific detection of E. coli O157:H7 in ground beef samples. MNAC were prepared by immobilizing biotin-labeled polyclonal goat anti-E. coli antibodies onto streptavidin-coated magnetic nanoparticles, which were used to separate and concentrate E. coli O157:H7 from ground beef samples. Magnitude of impedance and phase angle were measured in a frequency range of 10 Hz to 1 MHz in the presence of 0.1M mannitol solution. The lowest detection limits of this biosensor for detection of E. coli O157:H7 in pure culture and ground beef samples were 7.4 x 10(4) and 8.0 x 10(5)CFU ml(-1), respectively. The regression equation for the normalized impedance change (NIC) versus E. coli O157:H7 concentration (N) in ground beef samples was NIC=15.55 N-71.04 with R(2)=0.95. Sensitivity of the impedance biosensor was improved by 35% by concentrating bacterial cells attached to MNAC in the active layer of IDAM above the surface of electrodes with the help of a magnetic field. Based on equivalent circuit analysis, it was observed that bulk resistance and double layer capacitance were responsible for the impedance change caused by the presence of E. coli O157:H7 on the surface of IDAM. Surface immobilization techniques, redox probes, or sample incubation were not used in this impedance biosensor. The total detection time from sampling to measurement was 35 min.

  10. Selective Recognition of 5-Hydroxytryptamine and Dopamine on a Multi-Walled Carbon Nanotube-Chitosan Hybrid Film-Modified Microelectrode Array

    PubMed Central

    Xu, Huiren; Wang, Li; Luo, Jinping; Song, Yilin; Liu, Juntao; Zhang, Song; Cai, Xinxia

    2015-01-01

    It is difficult to determine dopamine (DA) and 5-hydroxytryptamine (5-HT) accurately because of the interference of ascorbic acid (AA) in vitro, which has a high concentration and can be oxidized at a potential close to DA and 5-HT at a conventional electrode, combined with the overlapping voltammetric signal of DA and 5-HT at a bare electrode. Herein, chitosan (CS) was used as a stabilizing matrix by electrochemical reaction, and multi-walled carbon nanotubes (MWCNTs) were modified onto the microelectrode array (MEA). The CS-MWCNT hybrid film-modified MEA was quite effective at simultaneously recognizing these species in a mixture and resolved the overlapping anodic peaks of AA, DA and 5-HT into three well-defined oxidation peaks in differential pulse voltammetry (DPV) at −80 mV, 105 mV and 300 mV (versus Ag|AgCl), respectively. The linear responses were obtained in the range of 5 × 10−6 M to 2 × 10−4 M for DA (r = 0.996) and in the range of 1 × 10−5 M to 3 × 10−4 M for 5-HT (r = 0.999) using the DPV under the presence of a single substance. While DA coexisted with 5-HT in the interference of 3 × 10−4 M AA, the linear responses were obtained in the range of 1 × 10−5 M to 3 × 10−4 M for selective molecular recognition of DA (r = 0.997) and 5-HT (r = 0.997) using the DPV. Therefore, this proposed MEA was successfully used for selective molecular recognition and determination of DA and 5-HT using the DPV, which has a potential application for real-time determination in vitro experiments. PMID:25580900

  11. Selective recognition of 5-hydroxytryptamine and dopamine on a multi-walled carbon nanotube-chitosan hybrid film-modified microelectrode array.

    PubMed

    Xu, Huiren; Wang, Li; Luo, Jinping; Song, Yilin; Liu, Juntao; Zhang, Song; Cai, Xinxia

    2015-01-08

    It is difficult to determine dopamine (DA) and 5-hydroxytryptamine (5-HT) accurately because of the interference of ascorbic acid (AA) in vitro, which has a high concentration and can be oxidized at a potential close to DA and 5-HT at a conventional electrode, combined with the overlapping voltammetric signal of DA and 5-HT at a bare electrode. Herein, chitosan (CS) was used as a stabilizing matrix by electrochemical reaction, and multi-walled carbon nanotubes (MWCNTs) were modified onto the microelectrode array (MEA). The CS-MWCNT hybrid film-modified MEA was quite effective at simultaneously recognizing these species in a mixture and resolved the overlapping anodic peaks of AA, DA and 5-HT into three well-defined oxidation peaks in differential pulse voltammetry (DPV) at -80 mV, 105 mV and 300 mV (versus Ag|AgCl), respectively. The linear responses were obtained in the range of 5 × 10(-6) M to 2 × 10(-4) M for DA (r = 0.996) and in the range of 1 × 10(-5) M to 3 × 10(-4) M for 5-HT (r = 0.999) using the DPV under the presence of a single substance. While DA coexisted with 5-HT in the interference of 3 × 10(-4) M AA, the linear responses were obtained in the range of 1 × 10(-5) M to 3 × 10(-4) M for selective molecular recognition of DA (r = 0.997) and 5-HT (r = 0.997) using the DPV. Therefore, this proposed MEA was successfully used for selective molecular recognition and determination of DA and 5-HT using the DPV, which has a potential application for real-time determination in vitro experiments.

  12. Inverted Silicon Nanopencil Array Solar Cells with Enhanced Contact Structures

    PubMed Central

    Liang, Xiaoguang; Shu, Lei; Lin, Hao; Fang, Ming; Zhang, Heng; Dong, Guofa; Yip, SenPo; Xiu, Fei; Ho, Johnny C.

    2016-01-01

    Although three-dimensional nanostructured solar cells have attracted extensive research attention due to their superior broadband and omnidirectional light-harvesting properties, majority of them are still suffered from complicated fabrication processes as well as disappointed photovoltaic performances. Here, we employed our newly-developed, low-cost and simple wet anisotropic etching to fabricate hierarchical silicon nanostructured arrays with different solar cell contact design, followed by systematic investigations of their photovoltaic characteristics. Specifically, nano-arrays with the tapered tips (e.g. inverted nanopencils) are found to enable the more conformal top electrode deposition directly onto the nanostructures for better series and shunt conductance, but its insufficient film coverage at the basal plane would still restrict the charge carrier collection. In contrast, the low-platform contact design facilitates a substantial photovoltaic device performance enhancement of ~24%, as compared to the one of conventional top electrode design, due to the shortened current path and improved lateral conductance for the minimized carrier recombination and series resistance. This enhanced contact structure can not only maintain excellent photon-trapping behaviors of nanostructures, but also help to eliminate adverse impacts of these tapered nano-morphological features on the contact resistance, providing further insight into design consideration in optimizing the contact geometry for high-performance nanostructured photovoltaic devices. PMID:27671709

  13. Inverted Silicon Nanopencil Array Solar Cells with Enhanced Contact Structures

    NASA Astrophysics Data System (ADS)

    Liang, Xiaoguang; Shu, Lei; Lin, Hao; Fang, Ming; Zhang, Heng; Dong, Guofa; Yip, Senpo; Xiu, Fei; Ho, Johnny C.

    2016-09-01

    Although three-dimensional nanostructured solar cells have attracted extensive research attention due to their superior broadband and omnidirectional light-harvesting properties, majority of them are still suffered from complicated fabrication processes as well as disappointed photovoltaic performances. Here, we employed our newly-developed, low-cost and simple wet anisotropic etching to fabricate hierarchical silicon nanostructured arrays with different solar cell contact design, followed by systematic investigations of their photovoltaic characteristics. Specifically, nano-arrays with the tapered tips (e.g. inverted nanopencils) are found to enable the more conformal top electrode deposition directly onto the nanostructures for better series and shunt conductance, but its insufficient film coverage at the basal plane would still restrict the charge carrier collection. In contrast, the low-platform contact design facilitates a substantial photovoltaic device performance enhancement of ~24%, as compared to the one of conventional top electrode design, due to the shortened current path and improved lateral conductance for the minimized carrier recombination and series resistance. This enhanced contact structure can not only maintain excellent photon-trapping behaviors of nanostructures, but also help to eliminate adverse impacts of these tapered nano-morphological features on the contact resistance, providing further insight into design consideration in optimizing the contact geometry for high-performance nanostructured photovoltaic devices.

  14. Inverted Silicon Nanopencil Array Solar Cells with Enhanced Contact Structures.

    PubMed

    Liang, Xiaoguang; Shu, Lei; Lin, Hao; Fang, Ming; Zhang, Heng; Dong, Guofa; Yip, SenPo; Xiu, Fei; Ho, Johnny C

    2016-09-27

    Although three-dimensional nanostructured solar cells have attracted extensive research attention due to their superior broadband and omnidirectional light-harvesting properties, majority of them are still suffered from complicated fabrication processes as well as disappointed photovoltaic performances. Here, we employed our newly-developed, low-cost and simple wet anisotropic etching to fabricate hierarchical silicon nanostructured arrays with different solar cell contact design, followed by systematic investigations of their photovoltaic characteristics. Specifically, nano-arrays with the tapered tips (e.g. inverted nanopencils) are found to enable the more conformal top electrode deposition directly onto the nanostructures for better series and shunt conductance, but its insufficient film coverage at the basal plane would still restrict the charge carrier collection. In contrast, the low-platform contact design facilitates a substantial photovoltaic device performance enhancement of ~24%, as compared to the one of conventional top electrode design, due to the shortened current path and improved lateral conductance for the minimized carrier recombination and series resistance. This enhanced contact structure can not only maintain excellent photon-trapping behaviors of nanostructures, but also help to eliminate adverse impacts of these tapered nano-morphological features on the contact resistance, providing further insight into design consideration in optimizing the contact geometry for high-performance nanostructured photovoltaic devices.

  15. Nanofabrication of arrays of silicon field emitters with vertical silicon nanowire current limiters and self-aligned gates

    NASA Astrophysics Data System (ADS)

    Guerrera, S. A.; Akinwande, A. I.

    2016-07-01

    We developed a fabrication process for embedding a dense array (108 cm-2) of high-aspect-ratio silicon nanowires (200 nm diameter and 10 μm tall) in a dielectric matrix and then structured/exposed the tips of the nanowires to form self-aligned gate field emitter arrays using chemical mechanical polishing (CMP). Using this structure, we demonstrated a high current density (100 A cm-2), uniform, and long lifetime (>100 h) silicon field emitter array architecture in which the current emitted by each tip is regulated by the silicon nanowire current limiter connected in series with the tip. Using the current voltage characteristics and with the aid of numerical device models, we estimated the tip radius of our field emission arrays to be ≈4.8 nm, as consistent with the tip radius measured using a scanning electron microscope (SEM).

  16. Micropatterning of poly(dimethylsiloxane) using a photoresist lift-off technique for selective electrical insulation of microelectrode arrays

    PubMed Central

    Park, Jaewon; Kim, Hyun Soo; Han, Arum

    2009-01-01

    A poly(dimethylsiloxane) (PDMS) patterning method based on a photoresist lift-off technique to make an electrical insulation layer with selective openings is presented. The method enables creating PDMS patterns with small features and various thicknesses without any limitation in the designs and without the need for complicated processes or expensive equipments. Patterned PDMS layers were created by spin-coating liquid phase PDMS on top of a substrate having sacrificial photoresist patterns, followed by a photoresist lift-off process. The thickness of the patterned PDMS layers could be accurately controlled (6.5–24 µm) by adjusting processing parameters such as PDMS spin-coating speeds, PDMS dilution ratios, and sacrificial photoresist thicknesses. PDMS features as small as 15 µm were successfully patterned and the effects of each processing parameter on the final patterns were investigated. Electrical resistance tests between adjacent electrodes with and without the insulation layer showed that the patterned PDMS layer functions properly as an electrical insulation layer. Biocompatibility of the patterned PDMS layer was confirmed by culturing primary neuron cells on top of the layer for up to two weeks. An extensive neuronal network was successfully formed, showing that this PDMS patterning method can be applied to various biosensing microdevices. The utility of this fabrication method was further demonstrated by successfully creating a patterned electrical insulation layer on flexible substrates containing multi-electrode arrays. PMID:19946385

  17. Low cost silicon solar array project large area silicon sheet task: Silicon web process development

    NASA Technical Reports Server (NTRS)

    Duncan, C. S.; Seidensticker, R. G.; Mchugh, J. P.; Blais, P. D.; Davis, J. R., Jr.

    1977-01-01

    Growth configurations were developed which produced crystals having low residual stress levels. The properties of a 106 mm diameter round crucible were evaluated and it was found that this design had greatly enhanced temperature fluctuations arising from convection in the melt. Thermal modeling efforts were directed to developing finite element models of the 106 mm round crucible and an elongated susceptor/crucible configuration. Also, the thermal model for the heat loss modes from the dendritic web was examined for guidance in reducing the thermal stress in the web. An economic analysis was prepared to evaluate the silicon web process in relation to price goals.

  18. Magnetic field perturbation of neural recording and stimulating microelectrodes

    NASA Astrophysics Data System (ADS)

    Martinez-Santiesteban, Francisco M.; Swanson, Scott D.; Noll, Douglas C.; Anderson, David J.

    2007-04-01

    To improve the overall temporal and spatial resolution of brain mapping techniques, in animal models, some attempts have been reported to join electrophysiological methods with functional magnetic resonance imaging (fMRI). However, little attention has been paid to the image artefacts produced by the microelectrodes that compromise the anatomical or functional information of those studies. This work presents a group of simulations and MR images that show the limitations of wire microelectrodes and the potential advantages of silicon technology, in terms of image quality, in MRI environments. Magnetic field perturbations are calculated using a Fourier-based method for platinum (Pt) and tungsten (W) microwires as well as two different silicon technologies. We conclude that image artefacts produced by microelectrodes are highly dependent not only on the magnetic susceptibility of the materials used but also on the size, shape and orientation of the electrodes with respect to the main magnetic field. In addition silicon microelectrodes present better MRI characteristics than metallic microelectrodes. However, metallization layers added to silicon materials can adversely affect the quality of MR images. Therefore only those silicon microelectrodes that minimize the amount of metallic material can be considered MR-compatible and therefore suitable for possible simultaneous fMRI and electrophysiological studies. High resolution gradient echo images acquired at 2 T (TR/TE = 100/15 ms, voxel size = 100 × 100 × 100 µm3) of platinum-iridium (Pt-Ir, 90%-10%) and tungsten microwires show a complete signal loss that covers a volume significantly larger than the actual volume occupied by the microelectrodes: roughly 400 times larger for Pt-Ir and 180 for W, at the tip of the microelectrodes. Similar MR images of a single-shank silicon microelectrode only produce a partial volume effect on the voxels occupied by the probe with less than 50% of signal loss.

  19. Highly organised and dense vertical silicon nanowire arrays grown in porous alumina template on <100> silicon wafers

    NASA Astrophysics Data System (ADS)

    Gorisse, Therese; Dupré, Ludovic; Gentile, Pascal; Martin, Mickael; Zelsmann, Marc; Buttard, Denis

    2013-06-01

    In this work, nanoimprint lithography combined with standard anodization etching is used to make perfectly organised triangular arrays of vertical cylindrical alumina nanopores onto standard <100>-oriented silicon wafers. Both the pore diameter and the period of alumina porous array are well controlled and can be tuned: the periods vary from 80 to 460 nm, and the diameters vary from 15 nm to any required diameter. These porous thin layers are then successfully used as templates for the guided epitaxial growth of organised mono-crystalline silicon nanowire arrays in a chemical vapour deposition chamber. We report the densities of silicon nanowires up to 9 × 109 cm-2 organised in highly regular arrays with excellent diameter distribution. All process steps are demonstrated on surfaces up to 2 × 2 cm2. Specific emphasis was made to select techniques compatible with microelectronic fabrication standards, adaptable to large surface samples and with a reasonable cost. Achievements made in the quality of the porous alumina array, therefore on the silicon nanowire array, widen the number of potential applications for this technology, such as optical detectors or biological sensors.

  20. Highly organised and dense vertical silicon nanowire arrays grown in porous alumina template on <100> silicon wafers.

    PubMed

    Gorisse, Therese; Dupré, Ludovic; Gentile, Pascal; Martin, Mickael; Zelsmann, Marc; Buttard, Denis

    2013-06-17

    In this work, nanoimprint lithography combined with standard anodization etching is used to make perfectly organised triangular arrays of vertical cylindrical alumina nanopores onto standard <100>-oriented silicon wafers. Both the pore diameter and the period of alumina porous array are well controlled and can be tuned: the periods vary from 80 to 460 nm, and the diameters vary from 15 nm to any required diameter. These porous thin layers are then successfully used as templates for the guided epitaxial growth of organised mono-crystalline silicon nanowire arrays in a chemical vapour deposition chamber. We report the densities of silicon nanowires up to 9 × 109 cm-2 organised in highly regular arrays with excellent diameter distribution. All process steps are demonstrated on surfaces up to 2 × 2 cm2. Specific emphasis was made to select techniques compatible with microelectronic fabrication standards, adaptable to large surface samples and with a reasonable cost. Achievements made in the quality of the porous alumina array, therefore on the silicon nanowire array, widen the number of potential applications for this technology, such as optical detectors or biological sensors.

  1. Highly organised and dense vertical silicon nanowire arrays grown in porous alumina template on <100> silicon wafers

    PubMed Central

    2013-01-01

    In this work, nanoimprint lithography combined with standard anodization etching is used to make perfectly organised triangular arrays of vertical cylindrical alumina nanopores onto standard <100>−oriented silicon wafers. Both the pore diameter and the period of alumina porous array are well controlled and can be tuned: the periods vary from 80 to 460 nm, and the diameters vary from 15 nm to any required diameter. These porous thin layers are then successfully used as templates for the guided epitaxial growth of organised mono-crystalline silicon nanowire arrays in a chemical vapour deposition chamber. We report the densities of silicon nanowires up to 9 × 109 cm−2 organised in highly regular arrays with excellent diameter distribution. All process steps are demonstrated on surfaces up to 2 × 2 cm2. Specific emphasis was made to select techniques compatible with microelectronic fabrication standards, adaptable to large surface samples and with a reasonable cost. Achievements made in the quality of the porous alumina array, therefore on the silicon nanowire array, widen the number of potential applications for this technology, such as optical detectors or biological sensors. PMID:23773702

  2. Dense arrays of uniform submicron pores in silicon and their applications.

    PubMed

    Brodoceanu, Daniel; Elnathan, Roey; Prieto-Simón, Beatriz; Delalat, Bahman; Guinan, Taryn; Kroner, Elmar; Voelcker, Nicolas H; Kraus, Tobias

    2015-01-21

    We report a versatile particle-based route to dense arrays of parallel submicron pores with high aspect ratio in silicon and explore the application of these arrays in sensors, optics, and polymer micropatterning. Polystyrene (PS) spheres are convectively assembled on gold-coated silicon wafers and sputter-etched, resulting in well-defined gold disc arrays with excellent long-range order. The gold discs act as catalysts in metal-assisted chemical etching, yielding uniform pores with straight walls, flat bottoms, and high aspect ratio. The resulting pore arrays can be used as robust antireflective surfaces, in biosensing applications, and as templates for polymer replica molding.

  3. Extrinsic charge-extraction device /XCED/ - An extrinsic-silicon focal-plane array architecture

    NASA Astrophysics Data System (ADS)

    Pocock, D. N.; Chiu, K. Y.; Missman, R. A.; Nuttall, D. E.

    1980-01-01

    The XCED (extrinsic charge-extraction device) is a unique focal-plane array structure designed for staring infrared-imaging applications. Extrinsic-silicon detectors, MOS integrating storage capacitors, and unique accumulation mode multiplexing devices are combined in a two-dimensional array within a single monolithic chip. Zinc-doped silicon has been studied and utilized to fabricate detectors sensitive in the 2 to 4 micron spectral band with BLIP operating temperatures above 110 K. The potentially severe problems for staring arrays of element-to-element nonuniformities and detector storage saturation have been solved. Preliminary results and thermal imagery are shown for a 16 x 16 element array.

  4. Microelectrodes for Studying Neurobiology

    PubMed Central

    Kita, Justin M.; Wightman, R. Mark

    2008-01-01

    Summary of recent advances Microelectrodes have emerged as an important tool used by scientists to study biological changes in the brain and in single cells. This review briefly summarizes the ways in which microelectrodes as chemical sensors have furthered the field of neurobiology by reporting on changes that occur on the sub-second time scale. Microelectrodes have been used in a variety of fields including their use by electrophysiologists to characterize neuronal action potentials and development of neural prosthetics. Here we restrict our review to microelectrodes that have been used as chemical sensors. They have played a major role in many important neurobiological findings. PMID:18675377

  5. Electrostatic Microactuators for Precise Positioning of Neural Microelectrodes

    PubMed Central

    Muthuswamy, Jit; Okandan, Murat; Jain, Tilak; Gilletti, Aaron

    2006-01-01

    Microelectrode arrays used for monitoring single and multineuronal action potentials often fail to record from the same population of neurons over a period of time likely due to micromotion of neurons away from the microelectrode, gliosis around the recording site and also brain movement due to behavior. We report here novel electrostatic microactuated microelectrodes that will enable precise repositioning of the microelectrodes within the brain tissue. Electrostatic comb-drive microactuators and associated microelectrodes are fabricated using the SUMMiT V™ (Sandia's Ultraplanar Multilevel MEMS Technology) process, a five-layer polysilicon micromachining technology of the Sandia National labs, NM. The microfabricated microactuators enable precise bidirectional positioning of the microelectrodes in the brain with accuracy in the order of 1 μm. The microactuators allow for a linear translation of the microelectrodes of up to 5 mm in either direction making it suitable for positioning microelectrodes in deep structures of a rodent brain. The overall translation was reduced to approximately 2 mm after insulation of the microelectrodes with epoxy for monitoring multiunit activity. The microactuators are capable of driving the microelectrodes in the brain tissue with forces in the order of several micro-Newtons. Single unit recordings were obtained from the somatosensory cortex of adult rats in acute experiments demonstrating the feasibility of this technology. Further optimization of the insulation, packaging and interconnect issues will be necessary before this technology can be validated in long-term experiments. PMID:16235660

  6. Electrostatic microactuators for precise positioning of neural microelectrodes.

    PubMed

    Muthuswamy, Jit; Okandan, Murat; Jain, Tilak; Gilletti, Aaron

    2005-10-01

    Microelectrode arrays used for monitoring single and multineuronal action potentials often fail to record from the same population of neurons over a period of time likely due to micromotion of neurons away from the microelectrode, gliosis around the recording site and also brain movement due to behavior. We report here novel electrostatic microactuated microelectrodes that will enable precise repositioning of the microelectrodes within the brain tissue. Electrostatic comb-drive microactuators and associated microelectrodes are fabricated using the SUMMiT V (Sandia's Ultraplanar Multilevel MEMS Technology) process, a five-layer polysilicon micromachining technology of the Sandia National labs, NM. The microfabricated microactuators enable precise bidirectional positioning of the microelectrodes in the brain with accuracy in the order of 1 microm. The microactuators allow for a linear translation of the microelectrodes of up to 5 mm in either direction making it suitable for positioning microelectrodes in deep structures of a rodent brain. The overall translation was reduced to approximately 2 mm after insulation of the microelectrodes with epoxy for monitoring multiunit activity. The microactuators are capable of driving the microelectrodes in the brain tissue with forces in the order of several micro-Newtons. Single unit recordings were obtained from the somatosensory cortex of adult rats in acute experiments demonstrating the feasibility of this technology. Further optimization of the insulation, packaging and interconnect issues will be necessary before this technology can be validated in long-term experiments.

  7. Thermoelectric properties of electrolessly etched silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Sadhu, Jyothi; Tian, Hongxiang; Ma, Jun; Valavala, Krishna; Singh, Piyush; Sinha, Sanjiv

    2013-03-01

    Patterning silicon as nanowires with roughened sidewalls enhances the thermoelectric figure-of-merit ZT by order of magnitude compared to the bulk at 300 K. The enhancement is mainly achieved by the remarkable reduction in the thermal conductivity below 5 W/mK at 300 K with only a negligible effect on the power factor of these nanowires. While the focus remained on understanding the implications of surface disorder on the thermal conductivity, the phonon transport effects on the Seebeck coefficient of these wires remains largely unexplored. We developed an electroless etching technique to generate nanowire arrays (NWAs) with controlled surface roughness, morphology, porosity and doping. We conduct the simultaneous device-level measurements of the Seebeck coefficient and thermal conductivity of the NWAs using frequency domain techniques. We observe that nano-structuring quenches the phonon drag in NWAs thereby reducing the Seebeck coefficient by ~25% compared to the bulk at degenerate doping levels. Further, we observe that the sidewall roughness greater than 3 nm roughness height lowers the thermal conductivity 75% below the Casimir limit with 10% - 15% increase in Seebeck coefficient. The porous NWAs show thermal conductivity close to the amorphous limit of Si with enhancement in the Seebeck coefficient primarily due to the carrier depletion.

  8. Theoretical analysis of intracortical microelectrode recordings

    PubMed Central

    Lempka, Scott F; Johnson, Matthew D; Moffitt, Michael A; Otto, Kevin J; Kipke, Daryl R; McIntyre, Cameron C

    2011-01-01

    Advanced fabrication techniques have now made it possible to produce microelectrode arrays for recording the electrical activity of a large number of neurons in the intact brain for both clinical and basic science applications. However, the long-term recording performance desired for these applications is hindered by a number of factors that lead to device failure or a poor signal-to-noise ratio (SNR). The goal of this study was to identify factors that can affect recording quality using theoretical analysis of intracortical microelectrode recordings of single-unit activity. Extracellular microelectrode recordings were simulated with a detailed multi-compartment cable model of a pyramidal neuron coupled to a finite element volume conductor head model containing an implanted recording microelectrode. Recording noise sources were also incorporated into the overall modeling infrastructure. The analyses of this study would be very difficult to perform experimentally; however, our model-based approach enabled a systematic investigation of the effects of a large number of variables on recording quality. Our results demonstrate that recording amplitude and noise are relatively independent of microelectrode size, but instead are primarily affected by the selected recording bandwidth, impedance of the electrode-tissue interface, and the density and firing rates of neurons surrounding the recording electrode. This study provides the theoretical groundwork that allows for the design of the microelectrode and recording electronics such that the SNR is maximized. Such advances could help enable the long-term functionality required for chronic neural recording applications. PMID:21775783

  9. Theoretical analysis of intracortical microelectrode recordings

    NASA Astrophysics Data System (ADS)

    Lempka, Scott F.; Johnson, Matthew D.; Moffitt, Michael A.; Otto, Kevin J.; Kipke, Daryl R.; McIntyre, Cameron C.

    2011-08-01

    Advanced fabrication techniques have now made it possible to produce microelectrode arrays for recording the electrical activity of a large number of neurons in the intact brain for both clinical and basic science applications. However, the long-term recording performance desired for these applications is hindered by a number of factors that lead to device failure or a poor signal-to-noise ratio (SNR). The goal of this study was to identify factors that can affect recording quality using theoretical analysis of intracortical microelectrode recordings of single-unit activity. Extracellular microelectrode recordings were simulated with a detailed multi-compartment cable model of a pyramidal neuron coupled to a finite-element volume conductor head model containing an implanted recording microelectrode. Recording noise sources were also incorporated into the overall modeling infrastructure. The analyses of this study would be very difficult to perform experimentally; however, our model-based approach enabled a systematic investigation of the effects of a large number of variables on recording quality. Our results demonstrate that recording amplitude and noise are relatively independent of microelectrode size, but instead are primarily affected by the selected recording bandwidth, impedance of the electrode-tissue interface and the density and firing rates of neurons surrounding the recording electrode. This study provides the theoretical groundwork that allows for the design of the microelectrode and recording electronics such that the SNR is maximized. Such advances could help enable the long-term functionality required for chronic neural recording applications.

  10. Feasibility Study of Extended-Gate-Type Silicon Nanowire Field-Effect Transistors for Neural Recording.

    PubMed

    Kang, Hongki; Kim, Jee-Yeon; Choi, Yang-Kyu; Nam, Yoonkey

    2017-03-28

    In this research, a high performance silicon nanowire field-effect transistor (transconductance as high as 34 µS and sensitivity as 84 nS/mV) is extensively studied and directly compared with planar passive microelectrode arrays for neural recording application. Electrical and electrochemical characteristics are carefully characterized in a very well-controlled manner. We especially focused on the signal amplification capability and intrinsic noise of the transistors. A neural recording system using both silicon nanowire field-effect transistor-based active-type microelectrode array and platinum black microelectrode-based passive-type microelectrode array are implemented and compared. An artificial neural spike signal is supplied as input to both arrays through a buffer solution and recorded simultaneously. Recorded signal intensity by the silicon nanowire transistor was precisely determined by an electrical characteristic of the transistor, transconductance. Signal-to-noise ratio was found to be strongly dependent upon the intrinsic 1/f noise of the silicon nanowire transistor. We found how signal strength is determined and how intrinsic noise of the transistor determines signal-to-noise ratio of the recorded neural signals. This study provides in-depth understanding of the overall neural recording mechanism using silicon nanowire transistors and solid design guideline for further improvement and development.

  11. Synthesize of barium ferrite nanowire array by self-fabricated porous silicon template

    NASA Astrophysics Data System (ADS)

    Zheng, Hui; Han, Mangui; Deng, Jiangxia; Zheng, Liang; Wu, Jun; Deng, Longjiang; Qin, Huibin

    2014-08-01

    In this work, we synthesize barium ferrite (BaFe12O19) nanowire array in porous silicon template. The porous silicon templates are prepared via gold-assisted chemical etching method. The gold (Au) nanoparticles with mean diameter of 30 nm and distance of 100 nm were ordered on the surface of Si substrate through the Polystyrene (510000)-block-poly (2-vinylpyridine) (31000) (PS510000-b-P2VP31000) diblock copolymer. Porous silicon templates with mean diameter of 500 nm and distance between the pores of 500 nm were fabricated by two etching steps. BaFe12O19 nanowires with mean diameter of 200 nm were synthesized into a porous silicon template by a sol-gel method. Magnetic hysteresis loops show an isotropic feature of the BaFe12O19 nanowires array. The coercivity (Hc) and squareness ratio (Mr/Ms) of nanowire arrays are 2560 Oe and 0.6, respectively.

  12. Optical absorption enhancement with low structural-parameter sensitivity in three-dimensional silicon nanocavity array for solar photovoltaics

    NASA Astrophysics Data System (ADS)

    Zhang, Fuqiang; Sun, Ruinan; Hu, Ya; Peng, Kui-Qing

    2016-01-01

    Effective light trapping is essential for improving the efficiency and reducing the cost of thin-film silicon solar cells. Here, we numerically study the optical characteristics of periodic three-dimensional (3D) silicon nanocavity arrays. We found that the 3D silicon nanocavity array shows low sensitivity to geometric structural parameters for photon capture and achieves an outstanding efficiency superior to those of previously reported silicon nanostructures such as a nanowire and a nanohole with the same thickness. This excellence is attributed to a better antireflection capability and more resonant modes. The 3D silicon nanocavity array provides a new light-trapping strategy for thin-film photovoltaic devices.

  13. An array of layers in silicon sulfides: Chainlike and monolayer

    NASA Astrophysics Data System (ADS)

    Alonso-Lanza, T.; Ayuela, A.; Aguilera-Granja, F.

    2016-12-01

    While much is known about isoelectronic materials related to carbon nanostructures, such as boron-nitride layers and nanotubes, rather less is known about equivalent silicon-based materials. Following the recent discovery of phosphorene, here we discuss isoelectronic silicon-monosulfide monolayers. We describe a set of anisotropic structures that clearly have a high stability with respect to previously reported silicon-monosulfide monolayers. The source of the layer anisotropy is related to the presence of Si-S double chains linked by some Si-Si covalent bonds together with a remarkable spd hybridization on Si. The increased stability is related to silicon forming four bonds, including an additional double-bond-like Si-Si bond. The involvement of d orbitals brings more variety to silicon-sulfide-based nanostructures that are isoelectronic to phosphorene, which could be relevant for future applications, adding extra degrees of freedom.

  14. Multifunctional porous silicon nanopillar arrays: antireflection, superhydrophobicity, photoluminescence, and surface-enhanced Raman scattering (SERS)

    PubMed Central

    Kiraly, Brian; Yang, Shikuan

    2014-01-01

    We have fabricated porous silicon nanopillar arrays over large areas with a rapid, simple, and low-cost technique. The porous silicon nanopillars show unique longitudinal features along their entire length and have porosity with dimensions on the single-nanometer scale. Both Raman spectroscopy and photoluminescence data were used to determine the nanocrystallite size to be < 3 nm. The porous silicon nanopillar arrays also maintained excellent ensemble properties, reducing reflection nearly fivefold from planar silicon in the visible range without any optimization and approaching superhydrophobic behavior with increasing aspect ratio, demonstrating contact angles up to 138°. Finally, the porous silicon nanopillar arrays were made into sensitive surface enhanced Raman scattering (SERS) substrates by depositing metal onto the pillars. The SERS performance of the substrates was demonstrated using a chemical dye Rhodamine 6G. With their multitude of properties (i.e., antireflection, superhydrophobicity, photoluminescence, and sensitive SERS), the porous silicon nanopillar arrays described here can be valuable in applications such as solar harvesting, electrochemical cells, self-cleaning devices, and dynamic biological monitoring. PMID:23703091

  15. A novel MEMS field emission accelerometer based on silicon nanotips array

    NASA Astrophysics Data System (ADS)

    Chen, Li; Wen, Zhi-yu; Wen, Zhong-quan; Liu, Hai-tao

    2011-08-01

    A novel MEMS field emission accelerometer based on silicon nanotips array with about 10000 silicon tips in total is proposed. It consists of a proof mass, four L-shaped springs, silicon nanotips array, anode and feedback electrodes. The sensor is fabricated on one N-type (1 0 0) single crystal silicon wafer and one #7740 glass wafer using bulk silicon micromachining technology. The silicon tip arrays are form by wet etching with HNA (HNO3, HF and CH3COOH) with I2 as additive. After oxidation sharpening, the curvature radius of the tips is smaller than 50nm, and the tip arrays are metalized by sputtering TiW/Au film. ICP process is utilized to release the sensor chip. In order to improve the linearity of the sensor, a feedback control circuit is used to rebalance the proof mass. The accelerometer is tested on a dividing head and test results show that the sensitivity is about 420mV/g and nonlinearity is about 0.7% over a range of -1g~1g.

  16. Micro-Textured Black Silicon Wick for Silicon Heat Pipe Array

    NASA Technical Reports Server (NTRS)

    Yee, Karl Y.; Sunada, Eric T.; Ganapathi, Gani B.; Manohara, Harish; Homyk, Andrew; Prina, Mauro

    2013-01-01

    Planar, semiconductor heat arrays have been previously proposed and developed; however, this design makes use of a novel, microscale black silicon wick structure that provides increased capillary pumping pressure of the internal working fluid, resulting in increased effective thermal conductivity of the device, and also enables operation of the device in any orientation with respect to the gravity vector. In a heat pipe, the efficiency of thermal transfer from the case to the working fluid is directly proportional to the surface area of the wick in contact with the fluid. Also, the primary failure mechanism for heat pipes operating within the temperature range of interest is inadequate capillary pressure for the return of fluid from the condenser to the wick. This is also what makes the operation of heat pipes orientation-sensitive. Thus, the two primary requirements for a good wick design are a large surface area and high capillary pressure. Surface area can be maximized through nanomachined surface roughening. Capillary pressure is largely driven by the working fluid and wick structure. The proposed nanostructure wick has characteristic dimensions on the order of tens of microns, which promotes menisci of very small radii. This results in the possibility of enormous pumping potential due to the inverse proportionality with radius. Wetting, which also enhances capillary pumping, can be maximized through growth of an oxide layer or material deposition (e.g. TiO2) to create a superhydrophilic surface.

  17. Lithography-free fabrication of silicon nanowire and nanohole arrays by metal-assisted chemical etching

    NASA Astrophysics Data System (ADS)

    Liu, Ruiyuan; Zhang, Fute; Con, Celal; Cui, Bo; Sun, Baoquan

    2013-04-01

    We demonstrated a novel, simple, and low-cost method to fabricate silicon nanowire (SiNW) arrays and silicon nanohole (SiNH) arrays based on thin silver (Ag) film dewetting process combined with metal-assisted chemical etching. Ag mesh with holes and semispherical Ag nanoparticles can be prepared by simple thermal annealing of Ag thin film on a silicon substrate. Both the diameter and the distribution of mesh holes as well as the nanoparticles can be manipulated by the film thickness and the annealing temperature. The silicon underneath Ag coverage was etched off with the catalysis of metal in an aqueous solution containing HF and an oxidant, which form silicon nanostructures (either SiNW or SiNH arrays). The morphologies of the corresponding etched SiNW and SiNH arrays matched well with that of Ag holes and nanoparticles. This novel method allows lithography-free fabrication of the SiNW and SiNH arrays with control of the size and distribution.

  18. Ultralow thermal conductivity of silicon nanowire arrays by molecular dynamics simulation

    NASA Astrophysics Data System (ADS)

    Zhang, Ting; Xiong, Xue; Liu, Meng; Cheng, Guoan; Zheng, Ruiting; Xu, Ju; Wei, Lei

    2017-02-01

    We investigate the thermal conductivities of silicon nanowires (SiNWs) and their arrays based on molecular dynamics simulations. It is found that diminishing diameter, roughing surface and doping impurity of SiNWs can reduce their thermal conductivities by two or three orders of magnitude compared with that of bulk silicon crystals due to the strong phonon boundary and phonon impurity scattering. The simulated thermal conductivities of SiNW arrays demonstrate that arraying nanowires can further lower the thermal conductivity owing to the laterally-coupled effect, and the thermal conductivity of arrays decreases notably with the increased nanowire volume fraction, resulting in an ultralow thermal conductivity for the doped SiNW arrays with rough surfaces, which provides theoretical guidance of thermal management for semiconductor nanowire based microelectronic and thermoelectric devices.

  19. Black silicon with controllable macropore array for enhanced photoelectrochemical performance

    NASA Astrophysics Data System (ADS)

    Ao, Xianyu; Tong, Xili; Sik Kim, Dong; Zhang, Lianbing; Knez, Mato; Müller, Frank; He, Sailing; Schmidt, Volker

    2012-09-01

    Macroporous silicon with multiscale texture for reflection suppression and light trapping was achieved through a controllable electrochemical etching process. It was coated with TiO2 by atomic layer deposition, and used as the photoanode in photocatalytic water splitting. A conformal pn-junction was also built-in in order to split water without external bias. A 45% enhancement in photocurrent density was observed after black silicon etching. In comparison with nano-structured silicon, the etching process here has neither metal contamination nor requirement of vacuum facilities.

  20. A sensitive impedance biosensor based on immunomagnetic separation and urease catalysis for rapid detection of Listeria monocytogenes using an immobilization-free interdigitated array microelectrode.

    PubMed

    Chen, Qi; Lin, Jianhan; Gan, Chengqi; Wang, Yuhe; Wang, Dan; Xiong, Yonghua; Lai, Weihua; Li, Yuntao; Wang, Maohua

    2015-12-15

    In this study, we described a novel impedance biosensor combining immunomagnetic separation with urease catalysis for sensitive detection of foodborne bacteria using Listeria monocytogenes as model and an immobilization-free microelectrode as detector. The monoclonal antibodies (MAbs) were immobilized on the surface of the magnetic nanoparticles (MNPs) with the diameter of 180 nm by biotin-streptavidin system for specifically and efficiently separating Listeria cells from sample background. The polyclonal antibodies (PAbs) and the urease were modified onto the surface of the gold nanoparticles (AuNPs) with the diameter of 20 nm and the modified AuNPs were used to react with Listera to form the MNP-MAb-Listeria-PAb-AuNP-urease sandwich complexes. The urease in the complexes could catalyze the hydrolysis of the urea into ammonium carbonate and this led to an increase in the ionic strength of the media, which could be detected by the microelectrode. The magnetic separation efficiencies for L. monocytogenes at the concentrations ranging from 3.0×10(1) to 3.0×10(4) CFU/mL were over 95% for the pure cultures and over 85% for the spiked lettuce samples. The lower detection limit of this biosensor for L. monocytogenes was found to be 300 CFU/mL in both the pure cultures and the spiked lettuce samples. The microelectrode was demonstrated to be reusable for over 50 times with thorough cleaning by deionized water. This biosensor showed its potential to provide a simple, low-cost and sensitive method for rapid screening of foodborne pathogens and could be extended for detection of other biological or chemical targets.

  1. Laser desorption ionization and peptide sequencing on laser induced silicon microcolumn arrays

    DOEpatents

    Vertes, Akos [Reston, VA; Chen, Yong [San Diego, CA

    2011-12-27

    The present invention provides a method of producing a laser-patterned silicon surface, especially silicon wafers for use in laser desorption ionization (LDI-MS) (including MALDI-MS and SELDI-MS), devices containing the same, and methods of testing samples employing the same. The surface is prepared by subjecting a silicon substrate to multiple laser shots from a high-power picosecond or femtosecond laser while in a processing environment, e.g., underwater, and generates a remarkable homogenous microcolumn array capable of providing an improved substrate for LDI-MS.

  2. Flat-plate solar array project. Volume 3: Silicon sheet: Wafers and ribbons

    NASA Technical Reports Server (NTRS)

    Briglio, A.; Dumas, K.; Leipold, M.; Morrison, A.

    1986-01-01

    The primary objective of the Silicon Sheet Task of the Flat-Plate Solar Array (FSA) Project was the development of one or more low cost technologies for producing silicon sheet suitable for processing into cost-competitive solar cells. Silicon sheet refers to high purity crystalline silicon of size and thickness for fabrication into solar cells. Areas covered in the project were ingot growth and casting, wafering, ribbon growth, and other sheet technologies. The task made and fostered significant improvements in silicon sheet including processing of both ingot and ribbon technologies. An additional important outcome was the vastly improved understanding of the characteristics associated with high quality sheet, and the control of the parameters required for higher efficiency solar cells. Although significant sheet cost reductions were made, the technology advancements required to meet the task cost goals were not achieved.

  3. Highly efficient ultrathin-film amorphous silicon solar cells on top of imprinted periodic nanodot arrays

    SciTech Connect

    Yan, Wensheng Gu, Min; Tao, Zhikuo; Ong, Thiam Min Brian

    2015-03-02

    The addressing of the light absorption and conversion efficiency is critical to the ultrathin-film hydrogenated amorphous silicon (a-Si:H) solar cells. We systematically investigate ultrathin a-Si:H solar cells with a 100 nm absorber on top of imprinted hexagonal nanodot arrays. Experimental evidences are demonstrated for not only notable silver nanodot arrays but also lower-cost ITO and Al:ZnO nanodot arrays. The measured external quantum efficiency is explained by the simulation results. The J{sub sc} values are 12.1, 13.0, and 14.3 mA/cm{sup 2} and efficiencies are 6.6%, 7.5%, and 8.3% for ITO, Al:ZnO, and silver nanodot arrays, respectively. Simulated optical absorption distribution shows high light trapping within amorphous silicon layer.

  4. Free space optical communication link using a silicon photonic optical phased array

    NASA Astrophysics Data System (ADS)

    Rabinovich, William S.; Goetz, Peter G.; Pruessner, Marcel; Mahon, Rita; Ferraro, Mike S.; Park, Doe; Fleet, Erin; DePrenger, Michael J.

    2015-03-01

    Many components for free space optical communication systems have shrunken in size over the last decade. However, the steering systems have remained large and power hungry. Non-mechanical beam steering offers a path to reducing the size of these systems. Optical phased arrays can allow integrated beam steering elements. One of the most important aspects of an optical phased array technology is its scalability to a large number of elements. Silicon photonics can potentially offer this scalability using CMOS foundry techniques. In this paper a small-scale silicon photonic optical phased array is demonstrated for both the transmitter and receiver functions in a free space optical link. The device using an array of thermo-optically controlled waveguide phase shifters and demonstrates one-dimensional steering with a single control electrode. Transmission of a digitized video data stream over the link is shown.

  5. Optical absorption of several nanostructures arrays for silicon solar cells

    NASA Astrophysics Data System (ADS)

    Xu, Zhaopeng; Qiao, Huiling; Huangfu, Huichao; Li, Xiaowei; Guo, Jingwei; Wang, Haiyan

    2015-12-01

    To improve the efficiency and reduce the cost of solar cells, it's important to enhance the light absorption. Within the visible solar spectrum based on optimization simulations by COMSOL Multiphysics, the optical absorption of silicon cylindrical nanowires, nanocones and inverted nanocones was calculated respectively. The results reveal that the average absorption for the nanocones between 400 and 800 nm is 70.2%, which is better than cylindrical nanowires (55.3%), inverted nanocones (42.3%) and bulk silicon (42.2%). In addition, more than 95% of light from 630 to 800 nm is reflected for inverted nanocones, which can be used to enhance infrared reflection in photovoltaic devices.

  6. Fabrication of silicon nanowire arrays by macroscopic galvanic cell-driven metal catalyzed electroless etching in aerated HF solution.

    PubMed

    Liu, Lin; Peng, Kui-Qing; Hu, Ya; Wu, Xiao-Ling; Lee, Shuit-Tong

    2014-03-05

    Macroscopic galvanic cell-driven metal catalyzed electroless etching (MCEE) of silicon in aqueous hydrofluoric acid (HF) solution is devised to fabricate silicon nanowire (SiNW) arrays with dissolved oxygen acting as the one and only oxidizing agent. The key aspect of this strategy is the use of a graphite or other noble metal electrode that is electrically coupled with silicon substrate.

  7. Nanophotonic production, modulation and switching of ions by silicon microcolumn arrays

    DOEpatents

    Vertes, Akos [Reston, VA; Walker, Bennett N [Washington, DC

    2012-02-07

    The production and use of silicon microcolumn arrays that harvest light from a laser pulse to produce ions are described. The systems of the present invention seem to behave like a quasi-periodic antenna array with ion yields that show profound dependence on the plane of laser light polarization and the angle of incidence. By providing photonic ion sources, this enables enhanced control of ion production on a micro/nano scale and direct integration with miniaturized analytical devices.

  8. Nanophotonic production, modulation and switching of ions by silicon microcolumn arrays

    DOEpatents

    Vertes, Akos; Walker, Bennett N

    2015-04-07

    The production and use of silicon microcolumn arrays that harvest light from a laser pulse to produce ions are described. The systems of the present invention seem to behave like a quasi-periodic antenna array with ion yields that show profound dependence on the plane of laser light polarization and the angle of incidence. By providing photonic ion sources, this enables enhanced control of ion production on a micro/nano scale and direct integration with miniaturized analytical devices.

  9. Nanophotonic production, modulation and switching of ions by silicon microcolumn arrays

    DOEpatents

    Vertes, Akos; Walker, Bennett N.

    2013-09-10

    The production and use of silicon microcolumn arrays that harvest light from a laser pulse to produce ions are described. The systems of the present invention seem to behave like a quasi-periodic antenna array with ion yields that show profound dependence on the plane of laser light polarization and the angle of incidence. By providing photonic ion sources, this enables enhanced control of ion production on a micro/nano scale and direct integration with miniaturized analytical devices.

  10. Improvement of carrier diffusion length in silicon nanowire arrays using atomic layer deposition.

    PubMed

    Kato, Shinya; Kurokawa, Yasuyoshi; Miyajima, Shinsuke; Watanabe, Yuya; Yamada, Akira; Ohta, Yoshimi; Niwa, Yusuke; Hirota, Masaki

    2013-08-23

    To achieve a high-efficiency silicon nanowire (SiNW) solar cell, surface passivation technique is very important because a SiNW array has a large surface area. We successfully prepared by atomic layer deposition (ALD) high-quality aluminum oxide (Al2O3) film for passivation on the whole surface of the SiNW arrays. The minority carrier lifetime of the Al2O3-depositedSiNW arrays with bulk silicon substrate was improved to 27 μs at the optimum annealing condition. To remove the effect of bulk silicon, the effective diffusion length of minority carriers in the SiNW array was estimated by simple equations and a device simulator. As a result, it was revealed that the effective diffusion length in the SiNW arrays increased from 3.25 to 13.5 μm by depositing Al2O3 and post-annealing at 400°C. This improvement of the diffusion length is very important for application to solar cells, and Al2O3 deposited by ALD is a promising passivation material for a structure with high aspect ratio such as SiNW arrays.

  11. Energy requirement for the production of silicon solar arrays

    NASA Technical Reports Server (NTRS)

    Lindmayer, J.; Wihl, M.; Scheinine, A.; Morrison, A.

    1977-01-01

    An assessment of potential changes and alternative technologies which could impact the photovoltaic manufacturing process is presented. Topics discussed include: a multiple wire saw, ribbon growth techniques, silicon casting, and a computer model for a large-scale solar power plant. Emphasis is placed on reducing the energy demands of the manufacturing process.

  12. Omnidirectional Printing of Flexible, Stretchable, and Spanning Silver Microelectrodes

    NASA Astrophysics Data System (ADS)

    Ahn, Bok Y.; Duoss, Eric B.; Motala, Michael J.; Guo, Xiaoying; Park, Sang-Il; Xiong, Yujie; Yoon, Jongseung; Nuzzo, Ralph G.; Rogers, John A.; Lewis, Jennifer A.

    2009-03-01

    Flexible, stretchable, and spanning microelectrodes that carry signals from one circuit element to another are needed for many emerging forms of electronic and optoelectronic devices. We have patterned silver microelectrodes by omnidirectional printing of concentrated nanoparticle inks in both uniform and high-aspect ratio motifs with minimum widths of approximately 2 micrometers onto semiconductor, plastic, and glass substrates. The patterned microelectrodes can withstand repeated bending and stretching to large levels of strain with minimal degradation of their electrical properties. With this approach, wire bonding to fragile three-dimensional devices and spanning interconnects for solar cell and light-emitting diode arrays are demonstrated.

  13. The automated array assembly task of the low-cost silicon solar array project, phase 2

    NASA Technical Reports Server (NTRS)

    Coleman, M. G.; Pryor, R. A.; Sparks, T. G.; Legge, R.; Saltzman, D. L.

    1980-01-01

    Several specific processing steps as part of a total process sequence for manufacturing silicon solar cells were studied. Ion implantation was identified as the preferred process step for impurity doping. Unanalyzed beam ion implantation was shown to have major cost advantages over analyzed beam implantation. Further, high quality cells were fabricated using a high current unanalyzed beam. Mechanically masked plasma patterning of silicon nitride was shown to be capable of forming fine lines on silicon surfaces with spacings between mask and substrate as great as 250 micrometers. Extensive work was performed on advances in plated metallization. The need for the thick electroless palladium layer was eliminated. Further, copper was successfully utilized as a conductor layer utilizing nickel as a barrier to copper diffusion into the silicon. Plasma etching of silicon for texturing and saw damage removal was shown technically feasible but not cost effective compared to wet chemical etching techniques.

  14. Converting films for X-ray detectors, applied to amorphous silicon arrays

    SciTech Connect

    Ross, S.; Zentai, G.

    1998-12-31

    This paper presents results from the on-going efforts to characterize semiconductor thin films for direct X-ray conversion. The authors deposit these thin films onto an amorphous silicon (a-Si:H) readout array with the overall goal of developing a large area X-ray detector for protein crystallography, and for other X-ray imaging fields.

  15. Converting films for x-ray detectors, applied to amorphous silicon arrays.

    SciTech Connect

    Ross, S.; Zentai, G.

    1997-12-05

    This paper presents results from our on-going efforts to characterize semiconductor thin films for direct x-ray conversion. We deposit these thin films onto an amorphous silicon (a-Si:H) readout array with the overall goal of developing a large area x-ray detector for protein crystallography, and for other x-ray imaging fields.

  16. Photon lifetime correlated increase of Raman scattering and third-harmonic generation in silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Zabotnov, S. V.; Kholodov, M. M.; Georgobiani, V. A.; Presnov, D. E.; Golovan, L. A.; Kashkarov, P. K.

    2016-03-01

    Light propagation in silicon nanowire layers is studied via Raman scattering, third-harmonic generation and cross-correlation function measurements. The studied silicon nanowire arrays are characterized by a wire diameter of 50-100 nm and a layer thickness ranging from 0.2-16 μm. These structures are mesoscopic for light in the visible and near infrared ranges. The Raman signal increases monotonically with layer thickness increases at a 1.064 μm pump wavelength. The Stokes component for silicon nanowire arrays with a thickness larger than 2 μm exceeds that for crystalline silicon by more than an order. At the mentioned thicknesses, an increase is also registered for the third-harmonic signal, one that is up to fourfold greater than that for crystalline silicon for a 1.25 μm pump wavelength. Measurements of cross-correlation functions for the scattered photons evidence the significant photon lifetime increase in the silicon nanowire layers at their thickness increase. This fact can be connected with multiple scattering inside the studied mesoscopic structures and the increase of the interaction length for the Raman and third-harmonic generation processes.

  17. Beam test performance of a pixelated silicon array for the charge identification of cosmic rays

    NASA Astrophysics Data System (ADS)

    Maestro, P.; Bagliesi, M. G.; Bigongiari, G.; Bonechi, S.; Kim, M. Y.; Marrocchesi, P. S.

    2012-07-01

    A large area silicon array for the next generation of space-based experiments has been designed to determine, via multiple dE/dx measurements, the electric charge of cosmic radiation. The instrument can achieve an excellent charge discrimination, thus allowing to assess the elemental composition of charged cosmic rays at relativistic energies. Pairs of silicon sensors segmented into pixels were tested with a beam of fully ionized nuclei from boron to nickel (Z=28) with a kinetic energy of ∼1 GeV/amu, at the Fragment Separator (FRS) of the GSI Helmholtzzentrum für Schwerionenforschung in Darmstadt. The response of the sensors to different nuclear species was accurately characterized. The results of the beam test clearly show that a double-layered silicon array can achieve single-element separation with a resolution close to 0.2 electron charge units, in the whole interval of atomic number Z under test.

  18. Phonon processes in vertically aligned silicon nanowire arrays produced by low-cost all-solution galvanic displacement method

    NASA Astrophysics Data System (ADS)

    Banerjee, Debika; Trudeau, Charles; Gerlein, Luis Felipe; Cloutier, Sylvain G.

    2016-03-01

    The nanoscale engineering of silicon can significantly change its bulk optoelectronic properties to make it more favorable for device integration. Phonon process engineering is one way to enhance inter-band transitions in silicon's indirect band structure alignment. This paper demonstrates phonon localization at the tip of silicon nanowires fabricated by galvanic displacement using wet electroless chemical etching of a bulk silicon wafer. High-resolution Raman micro-spectroscopy reveals that such arrayed structures of silicon nanowires display phonon localization behaviors, which could help their integration into the future generations of nano-engineered silicon nanowire-based devices such as photodetectors and solar cells.

  19. A micromachined silicon parallel acoustic delay line (PADL) array for real-time photoacoustic tomography (PAT)

    NASA Astrophysics Data System (ADS)

    Cho, Young Y.; Chang, Cheng-Chung; Wang, Lihong V.; Zou, Jun

    2015-03-01

    To achieve real-time photoacoustic tomography (PAT), massive transducer arrays and data acquisition (DAQ) electronics are needed to receive the PA signals simultaneously, which results in complex and high-cost ultrasound receiver systems. To address this issue, we have developed a new PA data acquisition approach using acoustic time delay. Optical fibers were used as parallel acoustic delay lines (PADLs) to create different time delays in multiple channels of PA signals. This makes the PA signals reach a single-element transducer at different times. As a result, they can be properly received by single-channel DAQ electronics. However, due to their small diameter and fragility, using optical fiber as acoustic delay lines poses a number of challenges in the design, construction and packaging of the PADLs, thereby limiting their performances and use in real imaging applications. In this paper, we report the development of new silicon PADLs, which are directly made from silicon wafers using advanced micromachining technologies. The silicon PADLs have very low acoustic attenuation and distortion. A linear array of 16 silicon PADLs were assembled into a handheld package with one common input port and one common output port. To demonstrate its real-time PAT capability, the silicon PADL array (with its output port interfaced with a single-element transducer) was used to receive 16 channels of PA signals simultaneously from a tissue-mimicking optical phantom sample. The reconstructed PA image matches well with the imaging target. Therefore, the silicon PADL array can provide a 16× reduction in the ultrasound DAQ channels for real-time PAT.

  20. Improved Thermal Behavior of Multiple Linked Arrays of Silicon Nanowires Integrated into Planar Thermoelectric Microgenerators

    NASA Astrophysics Data System (ADS)

    Dávila, Diana; Tarancón, Albert; Calaza, Carlos; Salleras, Marc; Fernández-Regúlez, Marta; Paulo, Alvaro San; Fonseca, Luis

    2013-07-01

    Low-dimensional structures have been shown to be promising candidates for enhancing the thermoelectric properties of semiconductors, paving the way for integration of thermoelectric generators into silicon microtechnology. With this aim, dense arrays of well-oriented and size-controlled silicon nanowires (Si NWs) obtained by the chemical vapor deposition (CVD)-vapor-liquid-solid (VLS) mechanism have been implemented into microfabricated structures to develop planar unileg thermoelectric microgenerators ( μTEGs). Different low-thermal-mass suspended structures have been designed and microfabricated on silicon-on-insulator (SOI) substrates to operate as microthermoelements using p-type Si NW arrays as the thermoelectric material. To obtain nanowire arrays with effective lengths larger than normally attained by the VLS technique, structures composed of multiple ordered arrays consecutively bridged by transversal microspacers have been fabricated. The successive linkage of multiple Si NW arrays enabled the development of larger temperature differences while preserving good electrical contact. This gives rise to small internal thermoelement resistances, enhancing the performance of the devices as energy harvesters.

  1. On-chip silicon optical phased array for two-dimensional beam steering.

    PubMed

    Kwong, David; Hosseini, Amir; Covey, John; Zhang, Yang; Xu, Xiaochuan; Subbaraman, Harish; Chen, Ray T

    2014-02-15

    A 16-element optical phased array integrated on chip is presented for achieving two-dimensional (2D) optical beam steering. The device is fabricated on the silicon-on-insulator platform with a 250 nm silicon device layer. Steering is achieved via a combination of wavelength tuning and thermo-optic phase shifting with a switching power of P(π)=20  mW per channel. Using a silicon waveguide grating with a polycrystalline silicon overlay enables narrow far field beam widths while mitigating the precise etching needed for conventional shallow etch gratings. Using this system, 2D steering across a 20°×15° field of view is achieved with a sidelobe level better than 10 dB and with beam widths of 1.2°×0.5°.

  2. Solid-phase crystallization of amorphous silicon nanowire array and optical properties

    NASA Astrophysics Data System (ADS)

    Ishikawa, Ryousuke; Kato, Shinya; Yamazaki, Tatsuya; Kurokawa, Yasuyoshi; Miyajima, Shinsuke; Konagai, Makoto

    2014-02-01

    An amorphous silicon nanowire (a-SiNW) array perpendicular to a glass substrate can be successfully obtained through the metal-assisted chemical etching of amorphous silicon (a-Si) thin films. The solid-phase crystallization of a-SiNWs was carried out by thermal annealing in a forming gas in the temperature range from 600 to 900 °C. The effects of hydrogen in the film and the film morphology on the crystallization of a-SiNWs were investigated by Raman spectroscopy and transmission electron microscopy. A higher hydrogen concentration of a-SiNWs reduced the crystallization temperature, as in a-Si thin films. It was also revealed that the large surface area of the a-SiNW array affected the crystallization process. We also studied the optical property of the fabricated SiNW array and demonstrated its high potential as an active layer in solar cells.

  3. Hyperbolic and plasmonic properties of silicon/Ag aligned nanowire arrays.

    PubMed

    Prokes, S M; Glembocki, Orest J; Livenere, J E; Tumkur, T U; Kitur, J K; Zhu, G; Wells, B; Podolskiy, V A; Noginov, M A

    2013-06-17

    The hyperbolic and plasmonic properties of silicon nanowire/Ag arrays have been investigated. The aligned nanowire arrays were formed and coated by atomic layer deposition of Ag, which itself is a metamaterial due to its unique mosaic film structure. The theoretical and numerical studies suggest that the fabricated arrays have hyperbolic dispersion in the visible and IR ranges of the spectrum. The theoretical predictions have been indirectly confirmed by polarized reflection spectra, showing reduction of the reflection in p polarization in comparison to that in s polarization. Studies of dye emission on top of Si/Ag nanowire arrays show strong emission quenching and shortening of dye emission kinetics. This behavior is also consistent with the predictions for hyperbolic media. The measured SERS signals were enhanced by almost an order of magnitude for closely packed and aligned nanowires, compared to random nanowire composites. These results agree with electric field simulations of these array structures.

  4. Crosstalk analysis of silicon-on-insulator nanowire-arrayed waveguide grating

    NASA Astrophysics Data System (ADS)

    Li, Kai-Li; An, Jun-Ming; Zhang, Jia-Shun; Wang, Yue; Wang, Liang-Liang; Li, Jian-Guang; Wu, Yuan-Da; Yin, Xiao-Jie; Hu, Xiong-Wei

    2016-12-01

    The factors influencing the crosstalk of silicon-on-insulator (SOI) nanowire arrayed waveguide grating (AWG) are analyzed using the transfer function method. The analysis shows that wider and thicker arrayed waveguides, outsider fracture of arrayed waveguide, and larger channel space, could mitigate the deterioration of crosstalk. The SOI nanowire AWGs with different arrayed waveguide widths are fabricated by using deep ultraviolet lithography (DUV) and inductively coupled plasma etching (ICP) technology. The measurement results show that the crosstalk performance is improved by about 7 dB through adopting 800 nm arrayed waveguide width. Project supported by the National High Technology Research and Development Program of China (Grant No. 2015AA016902), the National Natural Science Foundation of China (Grant Nos. 61274047, 61435013, 61307034, and 61405188), and the National Key Research and Development Program of China (Grant No. 2016YFB0402504).

  5. Silicon material task. Part 3: Low-cost silicon solar array project

    NASA Technical Reports Server (NTRS)

    Roques, R. A.; Coldwell, D. M.

    1977-01-01

    The feasibility of a process for carbon reduction of low impurity silica in a plasma heat source was investigated to produce low-cost solar-grade silicon. Theoretical aspects of the reaction chemistry were studied with the aid of a computer program using iterative free energy minimization. These calculations indicate a threshold temperature exists at 2400 K below which no silicon is formed. The computer simulation technique of molecular dynamics was used to study the quenching of product species.

  6. Enhanced photoelectrochemical hydrogen production from silicon nanowire array photocathode.

    PubMed

    Oh, Ilwhan; Kye, Joohong; Hwang, Seongpil

    2012-01-11

    Herein we report that silicon nanowires (SiNWs) fabricated via metal-catalyzed electroless etching yielded a photoelectrochemical hydrogen generation performance superior to that of a planar Si, which is attributed to a lower kinetic overpotential due to a higher surface roughness, favorable shift in the flat-band potential, and light-trapping effects of the SiNW surface. The SiNW photocathode yielded a photovoltage of 0.42 V, one of the highest values ever reported for hydrogen generation on p-type Si/electrolyte interfaces.

  7. Comparative study of absorption in tilted silicon nanowire arrays for photovoltaics

    PubMed Central

    2014-01-01

    Silicon nanowire arrays have been shown to demonstrate light trapping properties and promising potential for next-generation photovoltaics. In this paper, we show that the absorption enhancement in vertical nanowire arrays on a perfectly electric conductor can be further improved through tilting. Vertical nanowire arrays have a 66.2% improvement in ultimate efficiency over an ideal double-pass thin film of the equivalent amount of material. Tilted nanowire arrays, with the same amount of material, exhibit improved performance over vertical nanowire arrays across a broad range of tilt angles (from 38° to 72°). The optimum tilt of 53° has an improvement of 8.6% over that of vertical nanowire arrays and 80.4% over that of the ideal double-pass thin film. Tilted nanowire arrays exhibit improved absorption over the solar spectrum compared with vertical nanowires since the tilt allows for the excitation of additional modes besides the HE 1m modes that are excited at normal incidence. We also observed that tilted nanowire arrays have improved performance over vertical nanowire arrays for a large range of incidence angles (under about 60°). PMID:25435833

  8. Comparative study of absorption in tilted silicon nanowire arrays for photovoltaics.

    PubMed

    Kayes, Md Imrul; Leu, Paul W

    2014-01-01

    Silicon nanowire arrays have been shown to demonstrate light trapping properties and promising potential for next-generation photovoltaics. In this paper, we show that the absorption enhancement in vertical nanowire arrays on a perfectly electric conductor can be further improved through tilting. Vertical nanowire arrays have a 66.2% improvement in ultimate efficiency over an ideal double-pass thin film of the equivalent amount of material. Tilted nanowire arrays, with the same amount of material, exhibit improved performance over vertical nanowire arrays across a broad range of tilt angles (from 38° to 72°). The optimum tilt of 53° has an improvement of 8.6% over that of vertical nanowire arrays and 80.4% over that of the ideal double-pass thin film. Tilted nanowire arrays exhibit improved absorption over the solar spectrum compared with vertical nanowires since the tilt allows for the excitation of additional modes besides the HE 1m modes that are excited at normal incidence. We also observed that tilted nanowire arrays have improved performance over vertical nanowire arrays for a large range of incidence angles (under about 60°).

  9. Characterization of electronic structures from CdS/Si nanoheterostructure array based on silicon nanoporous pillar array

    SciTech Connect

    Li, Yong; Song, Xiao Yan; Song, Yue Li; Ji, Peng Fei; Zhou, Feng Qun; Tian, Ming Li; Huang, Hong Chun; Li, Xin Jian

    2016-02-15

    Highlights: • CdS/Si nanoheterostructure array has been fabricated through a CBD method. • The electronic properties have been investigated by the I–V and C–V techniques. • The onset voltages, characteristic frequency and built-in potential are investigated. • The electronic structures can be tuned through the annealing treatments. - Abstract: The electronic properties of heterostructures are very important to its applications in the field of optoelectronic devices. Understanding and control of electronic properties are very necessary. CdS/Si nanoheterostructure array have been fabricated through growing CdS nanocrystals on the silicon nanoporous pillar array using a chemical bath deposition method. The electronic properties of CdS nanoheterostructure array have been investigated by the current–voltage, complex impedance spectroscopy and capacitance–voltage techniques. The onset voltages, characteristic frequency and built-in potential are gradually increased with increasing the annealing temperature. It is indicated that the electronic structures of CdS/Si nanoheterostructure array can be tuned through the annealing treatments.

  10. Optical phased array using single crystalline silicon high-contrast-gratings for beamsteering

    NASA Astrophysics Data System (ADS)

    Yoo, Byung-Wook; Chan, Trevor; Megens, Mischa; Sun, Tianbo; Yang, Weijian; Rao, Yi; Horsley, David A.; Chang-Hasnain, Connie J.; Wu, Ming C.

    2013-03-01

    We present a single crystalline silicon optical phased array using high-contrast-gratings (HCG) for fast two dimensional beamforming and beamsteering at 0.5 MHz. Since there are various applications for beamforming and beamsteering such as 3D imaging, optical communications, and light detection and ranging (LIDAR), it is great interest to develop ultrafast optical phased arrays. However, the beamsteering speed of optical phased arrays using liquid crystal and electro-wetting are typically limited to tens of milliseconds. Optical phased arrays using micro-electro-mechanical systems (MEMS) technologies can operate in the submegahertz range, but generally require metal coatings. The metal coating unfortunately cause bending of mirrors due to thermally induced stress. The novel MEMS-based optical phased array presented here consists of electrostatically driven 8 × 8 HCG pixels fabricated on a silicon-on-insulator (SOI) wafer. The HCG mirror is designed to have 99.9% reflectivity at 1550 nm wavelength without any reflective coating. The size of the HCG mirror is 20 × 20 μm2 and the mass is only 140 pg, much lighter than traditional MEMS mirrors. Our 8 × 8 optical phased array has a total field of view of +/-10° × 10° and a beam width of 2°. The maximum phase shift regarding the actuation gap defined by a 2 μm buried oxide layer of a SOI wafer is 1.7π at 20 V.

  11. Determination of parameters for successful spray coating of silicon microneedle arrays.

    PubMed

    McGrath, Marie G; Vrdoljak, Anto; O'Mahony, Conor; Oliveira, Jorge C; Moore, Anne C; Crean, Abina M

    2011-08-30

    Coated microneedle patches have demonstrated potential for effective, minimally invasive, drug and vaccine delivery. To facilitate cost-effective, industrial-scale production of coated microneedle patches, a continuous coating method which utilises conventional pharmaceutical processes is an attractive prospect. Here, the potential of spray-coating silicon microneedle patches using a conventional film-coating process was evaluated and the key process parameters which impact on coating coalescence and weight were identified by employing a fractional factorial design to coat flat silicon patches. Processing parameters analysed included concentration of coating material, liquid input rate, duration of spraying, atomisation air pressure, gun-to-surface distance and air cap setting. Two film-coating materials were investigated; hydroxypropylmethylcellulose (HPMC) and carboxymethylcellulose (CMC). HPMC readily formed a film-coat on silicon when suitable spray coating parameter settings were determined. CMC films required the inclusion of a surfactant (1%, w/w Tween 80) to facilitate coalescence of the sprayed droplets on the silicon surface. Spray coating parameters identified by experimental design, successfully coated 280μm silicon microneedle arrays, producing an intact film-coat, which follows the contours of the microneedle array without occlusion of the microneedle shape. This study demonstrates a novel method of coating microneedle arrays with biocompatible polymers using a conventional film-coating process. It is the first study to indicate the thickness and roughness of coatings applied to microneedle arrays. The study also highlights the importance of identifying suitable processing parameters when film coating substrates of micron dimensions. The ability of a fractional factorial design to identify these critical parameters is also demonstrated. The polymer coatings applied in this study can potentially be drug loaded for intradermal drug and vaccine delivery.

  12. Dense nanoimprinted silicon nanowire arrays with passivated axial p-i-n junctions for photovoltaic applications

    SciTech Connect

    Zhang, Peng; Liu, Pei; Siontas, Stylianos; Zaslavsky, A.; Pacifici, D.; Ha, Jong-Yoon; Krylyuk, S.; Davydov, A. V.

    2015-03-28

    We report on the fabrication and photovoltaic characteristics of vertical arrays of silicon axial p-i-n junction nanowire (NW) solar cells grown by vapor-liquid-solid (VLS) epitaxy. NW surface passivation with silicon dioxide shell is shown to enhance carrier recombination time, open-circuit voltage (V{sub OC}), short-circuit current density (J{sub SC}), and fill factor (FF). The photovoltaic performance of passivated individual NW and NW arrays was compared under 532 nm laser illumination with power density of ∼10 W/cm{sup 2}. Higher values of V{sub OC} and FF in the NW arrays are explained by enhanced light trapping. In order to verify the effect of NW density on light absorption and hence on the photovoltaic performance of NW arrays, dense Si NW arrays were fabricated using nanoimprint lithography to periodically arrange the gold seed particles prior to epitaxial growth. Compared to sparse NW arrays fabricated using VLS growth from randomly distributed gold seeds, the nanoimprinted NW array solar cells show a greatly increased peak external quantum efficiency of ∼8% and internal quantum efficiency of ∼90% in the visible spectral range. Three-dimensional finite-difference time-domain simulations of Si NW periodic arrays with varying pitch (P) confirm the importance of high NW density. Specifically, due to diffractive scattering and light trapping, absorption efficiency close to 100% in the 400–650 nm spectral range is calculated for a Si NW array with P = 250 nm, significantly outperforming a blanket Si film of the same thickness.

  13. Compact wavelength router based on a Silicon-on-insulator arrayed waveguide grating pigtailed to a fiber array.

    PubMed

    Dumon, P; Bogaerts, W; Van Thourhout, D; Taillaert, D; Baets, R; Wouters, J; Beckx, S; Jaenen, P

    2006-01-23

    We demonstrate a compact, fiber-pigtailed, 4-by-4 wavelength router in Silicon-on-insulator photonic wires, fabricated using CMOS processing methods. The core is an AWG with a 250GHz channel spacing and 1THz free spectral range, on a 425x155 microm(2) footprint. The insertion loss of the AWG was reduced to 3.5dB by applying a two-step processing technique. The crosstalk is -12dB. The device was pigtailed using vertical fiber couplers and an eight-fiber array connector.

  14. Phase 2 of the array automated assembly task for the low cost silicon solar array project

    NASA Technical Reports Server (NTRS)

    Petersen, R. C.

    1980-01-01

    Studies were conducted on several fundamental aspects of electroless nickel/solder metallization for silicon solar cells. A process, which precedes the electroless nickel plating with several steps of palladium plating and heat treatment, was compared directly with single step electroless nickel plating. Work was directed toward answering specific questions concerning the effect of silicon surface oxide on nickel plating, effects of thermal stresses on the metallization, sintering of nickel plated on silicon, and effects of exposure to the plating solution on solar cell characteristics. The process was found to be extremely lengthy and cumbersome, and was also found to produce a product virtually identical to that produced by single step electroless nickel plating, as shown by adhesion tests and electrical characteristics of cells under illumination.

  15. Energy requirement for the production of silicon solar arrays

    NASA Technical Reports Server (NTRS)

    Lindmayer, J.; Wihl, M.; Scheinine, A.; Rosenfield, T.; Wrigley, C. Y.; Morrison, A.; Anderson, J.; Clifford, A.; Lafky, W.

    1977-01-01

    The results of a study to investigate the feasibility of manufacturing photovoltaic solar array modules by the use of energy obtained from similar or identical photovoltaic sources are presented. The primary objective of this investigation was the characterization of the energy requirements of current and developing technologies which comprise the photovoltaic field. For cross-checking the energies of prevailing technologies data were also used and the wide-range assessment of alternative technologies included different refinement methods, various ways of producing light sheets, semicrystalline cells, etc. Energy data are utilized to model the behavior of a future solar breeder plant under various operational conditions.

  16. Infrared Vidicons Employing Metal-Silicon Schottky Diode Arrays

    DTIC Science & Technology

    1975-10-01

    platinum on the side of the wafer opposite to the diode array. (The iorward voltage drop calculated for the Pt-Si contact at 1 ixA is 70 mev...desired to calculate the potential at which the SiO surface will float in the geometry used in these retinae. It can be shown that the oxide...sin AW + cos Ax cos AW vc cos AW . A = l’\\ ’"• AW = R. (28) If one combines equations (28) and (24) to calculate the current flowing across the

  17. Nickel/silicon core/shell nanosheet arrays as electrode materials for lithium ion batteries

    SciTech Connect

    Huang, X.H. Zhang, P.; Wu, J.B.; Lin, Y.; Guo, R.Q.

    2016-08-15

    Highlights: • Ni nanosheet arrays is the core and Si layer is the shell. • Ni nanosheet arrays act as a three-dimensional current collector to support Si. • Ni nanosheet arrays can improve the conductivity and stability of the electrode. • Ni/Si nanosheet arrays exhibit excellent cyclic and rate performance. - Abstract: Ni/Si core/shell nanosheet arrays are proposed to enhance the electrochemical lithium-storage properties of silicon. The arrays are characterized by means of X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The arrays are micro-sized in height, which are constructed by interconnected Ni nanosheet as the core and Si coating layer as the shell. The electrochemical properties as anode materials of lithium ion batteries are investigated by cyclic voltammetry (CV) and galvanostatic charge-discharge tests. The arrays can achieve high reversible capacity, good cycle stability and high rate capability. It is believed that the enhanced electrochemical performance is attributed to the electrode structure, because the interconnected Ni nanosheet can act as a three-dimensional current collector, and it has the ability of improving the electrode conductivity, enlarging the electrochemical reaction interface, and suppressing the electrode pulverization.

  18. Multiscale Study of Plasmonic Scattering and Light Trapping Effect in Silicon Nanowire Array Solar Cells.

    PubMed

    Meng, Lingyi; Zhang, Yu; Yam, ChiYung

    2017-02-02

    Nanometallic structures that support surface plasmons provide new ways to confine light at deep-subwavelength scales. The effect of light scattering in nanowire array solar cells is studied by a multiscale approach combining classical electromagnetic (EM) and quantum mechanical simulations. A photovoltaic device is constructed by integrating a silicon nanowire array with a plasmonic silver nanosphere. The light scatterings by plasmonic element and nanowire array are obtained via classical EM simulations, while current-voltage characteristics and optical properties of the nanowire cells are evaluated quantum mechanically. We found that the power conversion efficiency (PCE) of photovoltaic device is substantially improved due to the local field enhancement of the plasmonic effect and light trapping by the nanowire array. In addition, we showed that there exists an optimal nanowire number density in terms of optical confinement and solar cell PCE.

  19. Two-dimensional beam steering using a thermo-optic silicon photonic optical phased array

    NASA Astrophysics Data System (ADS)

    Rabinovich, William S.; Goetz, Peter G.; Pruessner, Marcel W.; Mahon, Rita; Ferraro, Mike S.; Park, Doe; Fleet, Erin; DePrenger, Michael J.

    2016-11-01

    Many components for free-space optical (FSO) communication systems have shrunken in size over the last decade. However, the steering systems have remained large and power hungry. Nonmechanical beam steering offers a path to reducing the size of these systems. Optical phased arrays can allow integrated beam steering elements. One of the most important aspects of an optical phased array technology is its scalability to a large number of elements. Silicon photonics can potentially offer this scalability using CMOS foundry techniques. A phased array that can steer in two dimensions using the thermo-optic effect is demonstrated. No wavelength tuning of the input laser is needed and the design allows a simple control system with only two inputs. A benchtop FSO link with the phased array in both transmit and receive mode is demonstrated.

  20. Thermal conductivity of silicon nanowire arrays with controlled roughness

    SciTech Connect

    Feser, JP; Sadhu, JS; Azeredo, BP; Hsu, KH; Ma, J; Kim, J; Seong, M; Fang, NX; Li, XL; Ferreira, PM; Sinha, S; Cahill, DG

    2012-12-01

    A two-step metal assisted chemical etching technique is used to systematically vary the sidewall roughness of Si nanowires in vertically aligned arrays. The thermal conductivities of nanowire arrays are studied using time domain thermoreflectance and compared to their high-resolution transmission electron microscopy determined roughness. The thermal conductivity of nanowires with small roughness is close to a theoretical prediction based on an upper limit of the mean-free-paths of phonons given by the nanowire diameter. The thermal conductivity of nanowires with large roughness is found to be significantly below this prediction. Raman spectroscopy reveals that nanowires with large roughness also display significant broadening of the one-phonon peak; the broadening correlates well with the reduction in thermal conductivity. The origin of this broadening is not yet understood, as it is inconsistent with phonon confinement models, but could derive from microstructural changes that affect both the optical phonons observed in Raman scattering and the acoustic phonons that are important for heat conduction. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4767456

  1. High density micro-pyramids with silicon nanowire array for photovoltaic applications.

    PubMed

    Rahman, Tasmiat; Navarro-Cía, Miguel; Fobelets, Kristel

    2014-12-05

    We use a metal assisted chemical etch process to fabricate silicon nanowire arrays (SiNWAs) onto a dense periodic array of pyramids that are formed using an alkaline etch masked with an oxide layer. The hybrid micro-nano structure acts as an anti-reflective coating with experimental reflectivity below 1% over the visible and near-infrared spectral regions. This represents an improvement of up to 11 and 14 times compared to the pyramid array and SiNWAs on bulk, respectively. In addition to the experimental work, we optically simulate the hybrid structure using a commercial finite difference time domain package. The results of the optical simulations support our experimental work, illustrating a reduced reflectivity in the hybrid structure. The nanowire array increases the absorbed carrier density within the pyramid by providing a guided transition of the refractive index along the light path from air into the silicon. Furthermore, electrical simulations which take into account surface and Auger recombination show an efficiency increase for the hybrid structure of 56% over bulk, 11% over pyramid array and 8.5% over SiNWAs.

  2. Nanostructured biomimetic moth-eye arrays in silicon by nanoimprint lithography

    NASA Astrophysics Data System (ADS)

    Boden, Stuart A.; Bagnall, Darren M.

    2009-08-01

    The eyes and wings of some species of moth are covered in arrays of subwavelength pillars that have been tuned over millions of years of evolution to reflect as little sunlight as possible. We are investigating ways of exploiting this to reduce reflection from the surfaces of silicon solar cells. Here, we report on the experimental realization of biomimetic antireflective moth-eye arrays in silicon using a technique based on nanoimprint lithography and dry etching. Areas of 1cm x 1cm have been patterned and analysis of reflectance measurements predicts a loss in the performance of a solar cell of only 6.5% compared to an ideal antireflective coating. This compares well with an optimized single layer Si3N4 antireflective coating, for which an 8% loss is predicted.

  3. Application of neural networks to digital pulse shape analysis for an array of silicon strip detectors

    NASA Astrophysics Data System (ADS)

    Flores, J. L.; Martel, I.; Jiménez, R.; Galán, J.; Salmerón, P.

    2016-09-01

    The new generation of nuclear physics detectors that used to study nuclear reactions is considering the use of digital pulse shape analysis techniques (DPSA) to obtain the (A,Z) values of the reaction products impinging in solid state detectors. This technique can be an important tool for selecting the relevant reaction channels at the HYDE (HYbrid DEtector ball array) silicon array foreseen for the Low Energy Branch of the FAIR facility (Darmstadt, Germany). In this work we study the feasibility of using artificial neural networks (ANNs) for particle identification with silicon detectors. Multilayer Perceptron networks were trained and tested with recent experimental data, showing excellent identification capabilities with signals of several isotopes ranging from 12C up to 84Kr, yielding higher discrimination rates than any other previously reported.

  4. Ordered silicon microwire arrays grown from substrates patterned using imprint lithography and electrodeposition.

    PubMed

    Audesirk, Heather A; Warren, Emily L; Ku, Jessie; Lewis, Nathan S

    2015-01-28

    Silicon microwires grown by the vapor-liquid-solid process have attracted a great deal of interest as potential light absorbers for solar energy conversion. However, the research-scale techniques that have been demonstrated to produce ordered arrays of micro and nanowires may not be optimal for use as high-throughput processes needed for large-scale manufacturing. Herein we demonstrate the use of microimprint lithography to fabricate patterned templates for the confinement of an electrodeposited Cu catalyst for the vapor-liquid-solid (VLS) growth of Si microwires. A reusable polydimethylsiloxane stamp was used to pattern holes in silica sol-gels on silicon substrates, and the Cu catalyst was electrodeposited into the holes. Ordered arrays of crystalline p-type Si microwires were grown across the sol-gel-patterned substrates with materials quality and performance comparable to microwires fabricated with high-purity metal catalysts and cleanroom processing.

  5. Electrical properties of high density arrays of silicon nanowire field effect transistors

    NASA Astrophysics Data System (ADS)

    Kim, Hye-Young; Lee, Kangho; Lee, Jae Woo; Kim, Sangwook; Kim, Gyu-Tae; Duesberg, Georg S.

    2013-10-01

    Proximity effect corrected e-beam lithography of hydrogen silsesquioxane on silicon on insulator was used to fabricate multi-channel silicon nanowire field-effect transistors (SiNW FETs). Arrays of 15-channels with a line width of 18 nm and pitch as small as 50 nm, the smallest reported for electrically functional devices, were fabricated. These high density arrays were back-gated by the substrate and allowed for investigation of the effects of scaling on the electrical performance of this multi-channel SiNW FET. It was revealed that the drain current and the transconductance (gm) are both reduced with decreasing pitch size. The drain induced barrier lowering and the threshold voltage (Vth) are also decreased, whereas the subthreshold swing (S) is increased. The results are in agreement with our simulations of the electric potential profile of the devices. The study contains valuable information on SiNW FET integration and scaling for future devices.

  6. A wearable multiplexed silicon nonvolatile memory array using nanocrystal charge confinement.

    PubMed

    Kim, Jaemin; Son, Donghee; Lee, Mincheol; Song, Changyeong; Song, Jun-Kyul; Koo, Ja Hoon; Lee, Dong Jun; Shim, Hyung Joon; Kim, Ji Hoon; Lee, Minbaek; Hyeon, Taeghwan; Kim, Dae-Hyeong

    2016-01-01

    Strategies for efficient charge confinement in nanocrystal floating gates to realize high-performance memory devices have been investigated intensively. However, few studies have reported nanoscale experimental validations of charge confinement in closely packed uniform nanocrystals and related device performance characterization. Furthermore, the system-level integration of the resulting devices with wearable silicon electronics has not yet been realized. We introduce a wearable, fully multiplexed silicon nonvolatile memory array with nanocrystal floating gates. The nanocrystal monolayer is assembled over a large area using the Langmuir-Blodgett method. Efficient particle-level charge confinement is verified with the modified atomic force microscopy technique. Uniform nanocrystal charge traps evidently improve the memory window margin and retention performance. Furthermore, the multiplexing of memory devices in conjunction with the amplification of sensor signals based on ultrathin silicon nanomembrane circuits in stretchable layouts enables wearable healthcare applications such as long-term data storage of monitored heart rates.

  7. Multi-wire slurry wafering demonstrations. [slicing silicon ingots for solar arrays

    NASA Technical Reports Server (NTRS)

    Chen, C. P.

    1978-01-01

    Ten slicing demonstrations on a multi-wire slurry saw, made to evaluate the silicon ingot wafering capabilities, reveal that the present sawing capabilities can provide usable wafer area from an ingot 1.05m/kg (e.g. kerf width 0.135 mm and wafer thickness 0.265 mm). Satisfactory surface qualities and excellent yield of silicon wafers were found. One drawback is that the add-on cost of producing water from this saw, as presently used, is considerably higher than other systems being developed for the low-cost silicon solar array project (LSSA), primarily because the saw uses a large quantity of wire. The add-on cost can be significantly reduced by extending the wire life and/or by rescue of properly plated wire to restore the diameter.

  8. A wearable multiplexed silicon nonvolatile memory array using nanocrystal charge confinement

    PubMed Central

    Kim, Jaemin; Son, Donghee; Lee, Mincheol; Song, Changyeong; Song, Jun-Kyul; Koo, Ja Hoon; Lee, Dong Jun; Shim, Hyung Joon; Kim, Ji Hoon; Lee, Minbaek; Hyeon, Taeghwan; Kim, Dae-Hyeong

    2016-01-01

    Strategies for efficient charge confinement in nanocrystal floating gates to realize high-performance memory devices have been investigated intensively. However, few studies have reported nanoscale experimental validations of charge confinement in closely packed uniform nanocrystals and related device performance characterization. Furthermore, the system-level integration of the resulting devices with wearable silicon electronics has not yet been realized. We introduce a wearable, fully multiplexed silicon nonvolatile memory array with nanocrystal floating gates. The nanocrystal monolayer is assembled over a large area using the Langmuir-Blodgett method. Efficient particle-level charge confinement is verified with the modified atomic force microscopy technique. Uniform nanocrystal charge traps evidently improve the memory window margin and retention performance. Furthermore, the multiplexing of memory devices in conjunction with the amplification of sensor signals based on ultrathin silicon nanomembrane circuits in stretchable layouts enables wearable healthcare applications such as long-term data storage of monitored heart rates. PMID:26763827

  9. Aluminum-jointed silicon dioxide octagon nanohelix array with desired complex refractive index.

    PubMed

    Jen, Yi-Jun; Chen, Chien-Chi; Jheng, Ci-Yao

    2014-06-15

    In this Letter, glancing angle deposition is used to form an aluminum-jointed silicon dioxide octagon nanohelix array as a 3D nanostructured thin film. As a sculptured metal-dielectric composite, the film exhibits a complex refractive index of near unity with a small imaginary part. This structured film is demonstrated as an efficient light absorber to absorb light in a broad band and over a wide range of angles for both polarization states.

  10. Silicon microhole arrays architecture for stable and efficient photoelectrochemical cells using ionic liquids electrolytes

    NASA Astrophysics Data System (ADS)

    Shen, Xiaojuan; Chen, Ling; Li, Junnan; Zhao, Jie

    2016-06-01

    Silicon microhole arrays (SiMHs) structure is constructed and fabricated by a low-cost maskless anodic etching process, which is applied as the photoanode for the silicon photoelectrochemical (PEC) cells. The depths of silicon microhole arrays can be independently controlled by the etching time. The light-scattering properties are also investigated. Additionally, surface morphology analysis show that large hole diameters of SiMHs is very favourable for the full-filling of ionic liquids electrolyte. Therefore, better electrochemical contact as well as high ionic conductivity of the ionic liquids electrolyte renders the PEC SiMHs solar cells to exhibit more excellent performance. After optimization, the maximum PCE could be achieved at 4.04% for the SiMHs cell. The performance of the SiMHs cell is highly comparable to that of silicon nanowires cell. More importantly, the liquid-state electrolyte is confined in the unique microhole structure, which can obviously prevent the leakage of the ionic liquids electrolyte, resulting in much better long-term stability than the reference devices. These preliminary results validate the concept of interpenetrating networks with semiconductor structure/ILs junction to develop stable and efficient PEC cells.

  11. Development of silicon-germanium visible-near infrared arrays

    NASA Astrophysics Data System (ADS)

    Zeller, John W.; Rouse, Caitlin; Efstathiadis, Harry; Haldar, Pradeep; Lewis, Jay S.; Dhar, Nibir K.; Wijewarnasuriya, Priyalal; Puri, Yash R.; Sood, Ashok K.

    2016-05-01

    Photodetectors based on germanium which do not require cooling and can provide good near-infrared (NIR) detection performance offer a low-cost alternative to conventional infrared sensors based on material systems such as InGaAs, InSb, and HgCdTe. As a result of the significant difference in thermal expansion coefficients between germanium and silicon, tensile strain incorporated into Ge epitaxial layers deposited on Si utilizing specialized growth processes can extend the operational range of detection to 1600 nm and longer wavelengths. We have fabricated Ge based PIN photodetectors on 300 mm diameter Si wafers to take advantage of high throughput, large-area complementary metal-oxide semiconductor (CMOS) technology. This device fabrication process involves low temperature epitaxial deposition of Ge to form a thin p+ (boron) Ge seed/buffer layer, and subsequent higher temperature deposition of a thicker Ge intrinsic layer. This is followed by selective ion implantation of phosphorus of various concentrations to form n+ Ge regions, deposition of a passivating oxide cap, and then top copper contacts to complete the PIN detector devices. Various techniques including transmission electron microscopy (TEM) and secondary ion mass spectrometry (SIMS) have been employed to characterize the material and structural properties of the epitaxially grown layers and fabricated detector devices, and these results are presented. The I-V response of the photodetector devices with and without illumination was also measured, for which the Ge based photodetectors consistently exhibited low dark currents of around ~1 nA at -1 V bias.

  12. Diffuse Brain Injury Elevates Tonic Glutamate Levels and Potassium-Evoked Glutamate Release in Discrete Brain Regions at Two Days Post-Injury: An Enzyme-Based Microelectrode Array Study

    PubMed Central

    Hinzman, Jason M.; Currier Thomas, Theresa; Burmeister, Jason J.; Quintero, Jorge E.; Huettl, Peter; Pomerleau, Francois; Gerhardt, Greg A.

    2010-01-01

    Abstract Traumatic brain injury (TBI) survivors often suffer from a wide range of post-traumatic deficits, including impairments in behavioral, cognitive, and motor function. Regulation of glutamate signaling is vital for proper neuronal excitation in the central nervous system. Without proper regulation, increases in extracellular glutamate can contribute to the pathophysiology and neurological dysfunction seen in TBI. In the present studies, enzyme-based microelectrode arrays (MEAs) that selectively measure extracellular glutamate at 2 Hz enabled the examination of tonic glutamate levels and potassium chloride (KCl)-evoked glutamate release in the prefrontal cortex, dentate gyrus, and striatum of adult male rats 2 days after mild or moderate midline fluid percussion brain injury. Moderate brain injury significantly increased tonic extracellular glutamate levels by 256% in the dentate gyrus and 178% in the dorsal striatum. In the dorsal striatum, mild brain injury significantly increased tonic glutamate levels by 200%. Tonic glutamate levels were significantly correlated with injury severity in the dentate gyrus and striatum. The amplitudes of KCl-evoked glutamate release were increased significantly only in the striatum after moderate injury, with a 249% increase seen in the dorsal striatum. Thus, with the MEAs, we measured discrete regional changes in both tonic and KCl-evoked glutamate signaling, which were dependent on injury severity. Future studies may reveal the specific mechanisms responsible for glutamate dysregulation in the post-traumatic period, and may provide novel therapeutic means to improve outcomes after TBI. PMID:20233041

  13. Low Earth orbit durability evaluation of protected silicone for advanced refractive photovoltaic concentrator arrays

    NASA Technical Reports Server (NTRS)

    Degroh, Kim K.; Mccollum, Timothy A.

    1994-01-01

    The need for efficient, cost effective sources of electrical power in space has led to the development of photovoltaic power systems which make use of novel refractive solar concentrators. These concentrators have been conceived in both point-focus and linear-focus designs. Current concentrator lenses are fabricated from flexible silicones with Fresnel facets along their inside surface. To insure the efficient operation of these power systems, the concentrator lenses must be durable and the silicone material must remain specularly transmitting over a reasonable lifetime in low Earth orbit (LEO) and other space environments. Because of the vulnerability of silicones to atomic oxygen and ultraviolet radiation in LEO these lenses have been coated with a multi-layer metal oxide protective coating. The objective of this research was to evaluate the LEO durability of the multilayer coated silicone for advanced refractive photovoltaic concentrator arrays with respect to optical properties and microstructure. Flat metal oxide coated silicone samples were exposed to ground-laboratory and in-space atomic oxyqen for durability evaluation.

  14. Technology for fabrication of sub-20 nm silicon planar nanowires array

    NASA Astrophysics Data System (ADS)

    Miakonkikh, Andrey V.; Tatarintsev, Andrey A.; Rogozhin, Alexander E.; Rudenko, Konstantin V.

    2016-12-01

    The results presented on Silicon one-dimensional structures fabrication which are promising for application in nanoelectronics, sensors, THz-applications. We employ two-stage technology of precise anizotropic plasma etching of silicon over e-beam resist and isotropic removal of thermally oxidised defected surface layer of silicon by wet etch. As first the process for nano-fins fabrication on SOI substrate was developed. HSQ resist was used as a negative-tone electron beam resist with good etch-resistance, high resolution and high mechanical stability. The etching was performed by RIE in mix of SF6 + C4F8. plasma. By changing the ratio SF6:C4F8, the sidewall profile angle can be controlled thoroughly. Next step to minimize lateral size of structures and reduce impact of surface defects on electron mobility in core of nanowires was the application of surface thermal oxidation to defected layer. It was used for selective removal of damaged silicon layer and polymer residues. Oxidation was performed with controlled flow of dry oxygen and water vapour. Oxidation rate was precisely controlled by ex-situ spectral ellipsometry on unpatterned chips As a result the arrays of planar sub-20 nm Silicon nanowires with length in the range 200 nm - 500 um were made.

  15. Two dimensional thermo-optic beam steering using a silicon photonic optical phased array

    NASA Astrophysics Data System (ADS)

    Mahon, Rita; Preussner, Marcel W.; Rabinovich, William S.; Goetz, Peter G.; Kozak, Dmitry A.; Ferraro, Mike S.; Murphy, James L.

    2016-03-01

    Components for free space optical communication terminals such as lasers, amplifiers, and receivers have all seen substantial reduction in both size and power consumption over the past several decades. However, pointing systems, such as fast steering mirrors and gimbals, have remained large, slow and power-hungry. Optical phased arrays provide a possible solution for non-mechanical beam steering devices that can be compact and lower in power. Silicon photonics is a promising technology for phased arrays because it has the potential to scale to many elements and may be compatible with CMOS technology thereby enabling batch fabrication. For most free space optical communication applications, two-dimensional beam steering is needed. To date, silicon photonic phased arrays have achieved two-dimensional steering by combining thermo-optic steering, in-plane, with wavelength tuning by means of an output grating to give angular tuning, out-of-plane. While this architecture might work for certain static communication links, it would be difficult to implement for moving platforms. Other approaches have required N2 controls for an NxN element phased array, which leads to complexity. Hence, in this work we demonstrate steering using the thermo-optic effect for both dimensions with a simplified steering mechanism requiring only two control signals, one for each steering dimension.

  16. Fabrication of a carbon nanotube protruding electrode array for a retinal prosthesis

    NASA Astrophysics Data System (ADS)

    Wang, Ke; Dai, Hongjie; Fishman, Harvey A.; Harris, James S.

    2005-01-01

    Implantable retinal prosthetic devices consisting of microelectrode arrays are being built in attempts to restore vision. Current retinal prostheses use metal planar electrodes. We are developing a novel electro-neural interface using carbon nanotube (CNT) bundles as flexible, protruding microelectrodes. We have synthesized vertically self-assembled, multi-walled CNT bundles by thermal chemical vapor deposition. Using conventional silicon-based micro-fabrication processes, these CNT bundles were integrated onto pre-patterned circuits. CNT protruding electrodes have significant potentials in providing safer stimulation for retinal prostheses. They could also act as recording units to sense electrical and chemical activities in neural systems for fundamental neuroscience research.

  17. Heterogeneously integrated III-V/silicon dual-mode distributed feedback laser array for terahertz generation.

    PubMed

    Shao, Haifeng; Keyvaninia, Shahram; Vanwolleghem, Mathias; Ducournau, Guillaume; Jiang, Xiaoqing; Morthier, Geert; Lampin, Jean-Francois; Roelkens, Gunther

    2014-11-15

    We demonstrate an integrated distributed feedback (DFB) laser array as a dual-wavelength source for narrowband terahertz (THz) generation. The laser array is composed of four heterogeneously integrated III-V-on-silicon DFB lasers with different lengths enabling dual-mode lasing tolerant to process variations, bias fluctuations, and ambient temperature variations. By optical heterodyning the two modes emitted by the dual-wavelength DFB laser in the laser array using a THz photomixer composed of an uni-traveling carrier photodiode (UTC-PD), a narrow and stable carrier signal with a frequency of 0.357 THz is generated. The central operating frequency and the emitted terahertz wave linewidth are analyzed, along with their dependency on the bias current applied to the laser diode and ambient temperature.

  18. Stress Analysis and Design of Silicon Solar Cell Arrays and Related Material Properties

    NASA Technical Reports Server (NTRS)

    Salama, A. M.; Rowe, W. M.; Yasui, R. K.

    1972-01-01

    A systematic approach is presented for the design of solar cell arrays to eliminate mechanical failures that might arise in components of the arrays in a thermal environment. A prerequisite to the approach is the characterization of material properties at different temperatures. Significant data is obtained for the thermal behavior of the silicon solar cell material and adhesives. Upon determining the mechanical and thermal material properties of the components of the solar cell array, utilizing a finite element idealization for predicting the stress fields in the components, and employing the von Mises failure criterion, potential failure areas in various design configurations in a given thermal environment are identified. Guide lines and means to optimize a given design are illustrated by two examples.

  19. Broadband light absorption of silicon nanowires embedded in Ag nano-hole arrays

    NASA Astrophysics Data System (ADS)

    Rao, Lei; Ji, Chun-Lei; Li, Ming

    2016-09-01

    Silicon nanowires (SiNWs) embedded in Ag nano-hole arrays with broadband light absorption is proposed in this paper. Finite Difference Time Domain (FDTD) simulations were utilized to obtain absorptivity and band diagrams for both SiNWs and SiNWs embedded in Ag nano-hole arrays. A direct relationship between waveguide modes and extraordinary absorptivity is established qualitatively, which helps to optimal design the structure parameters to achieve broadband absorptivity. After introducing Ag nano-hole arrays at the rear side of SiNWs, the band modes are extended into leaky regions and light energy can be fully absorbed, resulting in high absorptivity at long wavelength. Severe reflection is also suppressed by light trapping capability of SiNWs at short wavelength. Over 70% average absorptivity from 400 nm to 1100 nm is realized finally. This kinds of design give promising route for high efficiency solar cells and optical absorbers.

  20. Application of a silicon photodiode array for solar edge tracking in the Halogen Occultation Experiment

    NASA Technical Reports Server (NTRS)

    Mauldin, L. E., III; Moore, A. S.; Stump, C. S.; Mayo, L. S.

    1985-01-01

    The optical and electronic design of the Halogen Occultation Experiment (HALOE) elevation sunsensor is described. This system uses a Galilean telescope to form a solar image on a linear silicon photodiode array. The array is a self-scanned, monolithic charge coupled device. The addresses of both solar edges imaged on the array are used by the control/pointing system to scan the HALOE science instantaneous-field-of-view (IFOV) across the vertical solar diameter during instrument calibration, and then maintain the science IFOV four arcmin below the top edge during the science data occultation event. Vertical resolution of 16 arcsec and a radiometric dynamic range of 100 are achieved at the 0.7 micrometer operating wavelength. The design provides for loss of individual photodiode elements without loss of angular tracking capability. The HALOE instrument is a gas correlation radiometer that is now being developed by NASA Langley Research Center for the Upper Atmospheric Research Satellite.

  1. The Automated Array Assembly Task of the Low-cost Silicon Solar Array Project, Phase 2

    NASA Technical Reports Server (NTRS)

    Coleman, M. G.; Grenon, L.; Pastirik, E. M.; Pryor, R. A.; Sparks, T. G.

    1978-01-01

    An advanced process sequence for manufacturing high efficiency solar cells and modules in a cost-effective manner is discussed. Emphasis is on process simplicity and minimizing consumed materials. The process sequence incorporates texture etching, plasma processes for damage removal and patterning, ion implantation, low pressure silicon nitride deposition, and plated metal. A reliable module design is presented. Specific process step developments are given. A detailed cost analysis was performed to indicate future areas of fruitful cost reduction effort. Recommendations for advanced investigations are included.

  2. Fabrication of disposable topographic silicon oxide from sawtoothed patterns: control of arrays of gold nanoparticles.

    PubMed

    Cho, Heesook; Yoo, Hana; Park, Soojin

    2010-05-18

    Disposable topographic silicon oxide patterns were fabricated from polymeric replicas of sawtoothed glass surfaces, spin-coating of poly(dimethylsiloxane) (PDMS) thin films, and thermal annealing at certain temperature and followed by oxygen plasma treatment of the thin PDMS layer. A simple imprinting process was used to fabricate the replicated PDMS and PS patterns from sawtoothed glass surfaces. Next, thin layers of PDMS films having different thicknesses were spin-coated onto the sawtoothed PS surfaces and annealed at 60 degrees C to be drawn the PDMS into the valley of the sawtoothed PS surfaces, followed by oxygen plasma treatment to fabricate topographic silicon oxide patterns. By control of the thickness of PDMS layers, silicon oxide patterns having various line widths were fabricated. The silicon oxide topographic patterns were used to direct the self-assembly of polystyrene-block-poly(2-vinylpyridine) (PS-b-P2VP) block copolymer thin films via solvent annealing process. A highly ordered PS-b-P2VP micellar structure was used to let gold precursor complex with P2VP chains, and followed by oxygen plasma treatment. When the PS-b-P2VP thin films containing gold salts were exposed to oxygen plasma environments, gold salts were reduced to pure gold nanoparticles without changing high degree of lateral order, while polymers were completely degraded. As the width of trough and crest in topographic patterns increases, the number of gold arrays and size of gold nanoparticles are tuned. In the final step, the silicon oxide topographic patterns were selectively removed by wet etching process without changing the arrays of gold nanoparticles.

  3. Laser desorption/ionization from nanostructured surfaces: nanowires, nanoparticle films and silicon microcolumn arrays

    NASA Astrophysics Data System (ADS)

    Chen, Yong; Luo, Guanghong; Diao, Jiajie; Chornoguz, Olesya; Reeves, Mark; Vertes, Akos

    2007-04-01

    Due to their optical properties and morphology, thin films formed of nanoparticles are potentially new platforms for soft laser desorption/ionization (SLDI) mass spectrometry. Thin films of gold nanoparticles (with 12±1 nm particle size) were prepared by evaporation-driven vertical colloidal deposition and used to analyze a series of directly deposited polypeptide samples. In this new SLDI method, the required laser fluence for ion detection was equal or less than what was needed for matrix-assisted laser desorption/ionization (MALDI) but the resulting spectra were free of matrix interferences. A silicon microcolumn array-based substrate (a.k.a. black silicon) was developed as a new matrix-free laser desorption ionization surface. When low-resistivity silicon wafers were processed with a 22 ps pulse length 3×ω Nd:YAG laser in air, SF6 or water environment, regularly arranged conical spikes emerged. The radii of the spike tips varied with the processing environment, ranging from approximately 500 nm in water, to ~2 µm in SF6 gas and to ~5 µm in air. Peptide mass spectra directly induced by a nitrogen laser showed the formation of protonated ions of angiotensin I and II, substance P, bradykinin fragment 1-7, synthetic peptide, pro14-arg, and insulin from the processed silicon surfaces but not from the unprocessed areas. Threshold fluences for desorption/ionization were similar to those used in MALDI. Although compared to silicon nanowires the threshold laser pulse energy for ionization is significantly (~10×) higher, the ease of production and robustness of microcolumn arrays offer complementary benefits.

  4. Ordered arrays of nanoporous silicon nanopillars and silicon nanopillars with nanoporous shells

    NASA Astrophysics Data System (ADS)

    Wang, Dong; Ji, Ran; Du, Song; Albrecht, Arne; Schaaf, Peter

    2013-01-01

    The fabrication of ordered arrays of nanoporous Si nanopillars with and without nanoporous base and ordered arrays of Si nanopillars with nanoporous shells are presented. The fabrication route is using a combination of substrate conformal imprint lithography and metal-assisted chemical etching. The metal-assisted chemical etching is performed in solutions with different [HF]/[H2O2 + HF] ratios. Both pore formation and polishing (marked by the vertical etching of the nanopillars) are observed in highly doped and lightly doped Si during metal-assisted chemical etching. Pore formation is more active in the highly doped Si, while the transition from polishing to pore formation is more obvious in the lightly doped Si. The etching rate is clearly higher in the highly doped Si. Oxidation occurs on the sidewalls of the pillars by etching in solutions with small [HF]/[H2O2 + HF] ratios, leading to thinning, bending, and bonding of pillars.

  5. Ordered arrays of nanoporous silicon nanopillars and silicon nanopillars with nanoporous shells

    PubMed Central

    2013-01-01

    The fabrication of ordered arrays of nanoporous Si nanopillars with and without nanoporous base and ordered arrays of Si nanopillars with nanoporous shells are presented. The fabrication route is using a combination of substrate conformal imprint lithography and metal-assisted chemical etching. The metal-assisted chemical etching is performed in solutions with different [HF]/[H2O2 + HF] ratios. Both pore formation and polishing (marked by the vertical etching of the nanopillars) are observed in highly doped and lightly doped Si during metal-assisted chemical etching. Pore formation is more active in the highly doped Si, while the transition from polishing to pore formation is more obvious in the lightly doped Si. The etching rate is clearly higher in the highly doped Si. Oxidation occurs on the sidewalls of the pillars by etching in solutions with small [HF]/[H2O2 + HF] ratios, leading to thinning, bending, and bonding of pillars. PMID:23336430

  6. 15% Power Conversion Efficiency from a Gated Nanotube/Silicon Nanowire Array Solar Cell

    NASA Astrophysics Data System (ADS)

    Petterson, Maureen K.; Lemaitre, Maxime G.; Shen, Yu; Wadhwa, Pooja; Hou, Jie; Vasilyeva, Svetlana V.; Kravchenko, Ivan I.; Rinzler, Andrew G.

    2015-03-01

    Despite their enhanced light trapping ability the performance of silicon nanowire array solar cells have, been stagnant with power conversion efficiencies barely breaking 10%. The problem is understood to be the consequence of a high photo-carrier recombination at the large surface area of the Si nanowire sidewalls. Here, by exploiting 1) electronic gating via an ionic liquid electrolyte to induce inversion in the n-type Si nanowires and 2) using a layer of single wall carbon nanotubes engineered to contact each nanowire tip and extract the minority carriers, we demonstrate silicon nanowire array solar cells with power conversion efficiencies of 15%. Our results allow for discrimination between the two principle means of avoiding front surface recombination: surface passivation and the use of local fields. A deleterious electrochemical reaction of the silicon due to the electrolyte gating is shown to be caused by oxygen/water entrained in the ionic liquid electrolyte. While encapsulation can avoid the issue a non-encapsulation based solution is also described. We gratefully acknowledge support from the National Science Foundation under ECCS-1232018.

  7. Handheld mechanical cell lysis chip with ultra-sharp silicon nano-blade arrays for rapid intracellular protein extraction.

    PubMed

    Yun, Sung-Sik; Yoon, Sang Youl; Song, Min-Kyung; Im, Sin-Hyeog; Kim, Sohee; Lee, Jong-Hyun; Yang, Sung

    2010-06-07

    This paper presents a handheld mechanical cell lysis chip with ultra-sharp nano-blade arrays fabricated by simple and cost effective crystalline wet etching of (110) silicon. The ultra-sharp nano-blade array is simply formed by the undercutting of (110) silicon during the crystalline wet etching process. Cells can be easily disrupted by the silicon nano-blade array without the help of additional reagents or electrical sources. Based on the bench-top test of the proposed device, a handheld mechanical cell lysis chip with the nano-blade arrays is designed and fabricated for direct connection to a commercial syringe. The direct connection to a syringe provides rapid cell lysis, easy handling, and minimization of the lysate dead volume. The protein concentration in the cell lysate obtained by the proposed lysis chip is quantitatively comparable to the one prepared by a conventional chemical lysis method.

  8. A monolithic electrically-injected nanowire array edge-emitting laser on (001) silicon

    NASA Astrophysics Data System (ADS)

    Stark, E.; Frost, T.; Jahangir, S.; Hazari, A.; Deshpande, S.; Bhattacharya, P.

    2015-03-01

    A silicon-based laser remains an important goal in science and technology. Unfortunately silicon is ill-suited as a light-emitter, prompting the need for alternative high quality light sources integrated with silicon. One such alternative, presented here, is a monolithic III-N edge-emitting laser comprised of a planarized nanowire array. Nanowire heterostructures with InGaN/GaN disk-in-nanowire active regions were grown on (001)silicon and planarized with parylene, forming a composite slab heterostructure supporting a guided mode propagating transverse to the growth direction. From this composite slab, ridge-geometry lasers were fabricated. Lasers with emission at 533 nm (green) and 610 nm (red) are presented here. The lasers are characterized by Jth = 1.76 kA/cm2 (green) and 2.94kA/cm2 (red) under continuous wave current injection. The green lasers have device lifetime of ~7000 hrs. Small-signal modulation measurements have also been performed. The -3dB modulation bandwidth of the green laser is 5.7 GHz.

  9. Conjugated polymer-silicon nanowire array hybrid Schottky diode for solar cell application.

    PubMed

    Zhang, Fute; Song, Tao; Sun, Baoquan

    2012-05-17

    The hybrid Schottky diode based on silicon nanowire arrays (SiNWs) and poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) has been fabricated for high performance solar cells. The length of SiNWs on a silicon substrate, which is prepared by metal-assisted chemical etching, can be tuned by adjusting the length of the etching time. In addition, the average distances between the adjacent silicon nanowires can be controlled by changing the immersing time in a saturated PCl(5) solution. The hybrid devices are made from the SiNWs with different wire lengths and various distances between adjacent wires by spin-casting PEDOT:PSS on the silicon substrates. It is found that the length and density play leading roles in the electric output characteristics. The device made from SiNWs with optimum morphology can achieve a power conversion efficiency of 7.3%, which is much improved in comparison with that of the planar one. The measurement of the transient photovoltage decay and the analysis of the current versus voltage curve indicate that the charge recombination process is a dominant factor on the device performance.

  10. Conjugated polymer-silicon nanowire array hybrid Schottky diode for solar cell application

    NASA Astrophysics Data System (ADS)

    Zhang, Fute; Song, Tao; Sun, Baoquan

    2012-05-01

    The hybrid Schottky diode based on silicon nanowire arrays (SiNWs) and poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT:PSS) has been fabricated for high performance solar cells. The length of SiNWs on a silicon substrate, which is prepared by metal-assisted chemical etching, can be tuned by adjusting the length of the etching time. In addition, the average distances between the adjacent silicon nanowires can be controlled by changing the immersing time in a saturated PCl5 solution. The hybrid devices are made from the SiNWs with different wire lengths and various distances between adjacent wires by spin-casting PEDOT:PSS on the silicon substrates. It is found that the length and density play leading roles in the electric output characteristics. The device made from SiNWs with optimum morphology can achieve a power conversion efficiency of 7.3%, which is much improved in comparison with that of the planar one. The measurement of the transient photovoltage decay and the analysis of the current versus voltage curve indicate that the charge recombination process is a dominant factor on the device performance.

  11. Disordered wall arrays by photo-assisted electrochemical etching in n-type silicon

    NASA Astrophysics Data System (ADS)

    Yaohu, Lei; Zhigang, Zhao; Jinchuan, Guo; Ji, Li; Hanben, Niu

    2016-10-01

    The fabrication of ordered, high aspect-ratio microstructures in silicon by use of photo-assisted electrochemical etching is an important technology, where voltage and current density are significant factors. In this paper, disordered walls appear in 5-inch n-type silicon wafers when a large current density is used. Based on the theory of space charge region, these disordered walls are caused by the contradiction between the protection from dissolution by a high applied voltage and the dissolution by a high current density. To verify this point, wall arrays were fabricated at different applied voltages and current densities. Moreover, the critical voltage was kept constant and different current densities were applied to obtain conditions for avoiding disordered walls and achieving uniform wall arrays. Finally, a wall array with a period of 5.6 μm and a depth of 55 μm was achieved at an applied voltage of 3 V and a monotonically increasing current density ranging from 22.9 to 24.5 mA/cm2. Project supported by the National Special Foundation of China for Major Science Instrument (No. 61227802), the National Natural Science Foundation of China (No. 61405120), the National Program on Key Basic Research Project (No. 2012CB825802), and the China Postdoctoral Science Foundation (No. 2014M552224).

  12. Contact-pressure reduction of pyramidal optical probe array on corrugated aluminium/silicon nitride membranes

    NASA Astrophysics Data System (ADS)

    Jang, Jinhee; Oh, Seonghyeon; Hahn, Jae W.

    2017-04-01

    In this study, we develop an optical contact probe array for scanning near-field lithography. We fabricate the optical probes with a pyramidal tip array on an aluminium/silicon nitride composite membrane. Here, we reduce the contact pressure using the corrugations on the silicon nitride membrane and the flattened surface on top of the tip. After fabricating the 5  ×  5 probes in the array, we evaluate the contact pressure using the force–distance curve obtained by an atomic force microscope. The spring constants of the corrugated membranes are 10  ±  0.6 N m‑1. The contact pressure on a flattened 295 nm in-radius is calculated to be approximately 33 MPa for a 300 nm deflection. This value is 22 times smaller than that of a sharp pyramidal tip of 20 nm in-radius on a flat membrane.

  13. Silicon on ceramic process. Silicon sheet growth development for the large-area silicon sheet task of the low-cost silicon solar array project

    NASA Technical Reports Server (NTRS)

    Zook, J. D.; Heaps, J. D.; Maciolek, R. B.; Koepke, B. G.; Butter, C. D.; Schuldt, S. B.

    1977-01-01

    The technical and economic feasibility of producing solar-cell-quality sheet silicon was investigated. The sheets were made by coating one surface of carbonized ceramic substrates with a thin layer of large-grain polycrystalline silicon from the melt. Significant progress was made in all areas of the program.

  14. Progress and prospects of silicon-based design for optical phased array

    NASA Astrophysics Data System (ADS)

    Hu, Weiwei; Peng, Chao; Chang-Hasnain, Connie

    2016-03-01

    The high-speed, high-efficient, compact phase modulator array is indispensable in the Optical-phased array (OPA) which has been considered as a promising technology for realizing flexible and efficient beam steering. In our research, two methods are presented to utilize high-contrast grating (HCG) as high-efficient phase modulator. One is that HCG possesses high-Q resonances that origins from the cancellation of leaky waves. As a result, sharp resonance peaks appear on the reflection spectrum thus HCGs can be utilized as efficient phase shifters. Another is that low-Q mode HCG is utilized as ultra-lightweight mirror. With MEMS technology, small HCG displacement (~50 nm) leads to large phase change (~1.7π). Effective beam steering is achieved in Connie Chang-Hasnian's group. On the other hand, we theoretically and experimentally investigate the system design for silicon-based optical phased array, including the star coupler, phased array, emission elements and far-field patterns. Further, the non-uniform optical phased array is presented.

  15. Spectroscopic investigations of arrays containing vertically and horizontally aligned silicon nanowires

    NASA Astrophysics Data System (ADS)

    Volpati, Diogo; Mårtensson, Niklas; Anttu, Nicklas; Viklund, Per; Sundvall, Christian; Åberg, Ingvar; Bäckström, Joakim; Olin, Håkan; Björk, Mikael T.; Castillo-Leon, Jaime

    2016-12-01

    The properties of nanowire arrays have been investigated mainly in comparison with isolated nanowires or thin films, owing to the difficulty in controlling the nanowire alignment. In this study, we report on arrays containing vertically or horizontally aligned silicon nanowires, whose alignment and structure were determined using x-ray diffraction and scanning electron microscopy. The Raman spectra of the nanowire arrays differ from those of isolated nanowires because of distinct heat dissipation rates of the absorbed energy from the laser, in agreement with recent theoretical calculations. The tailored alignment of the nanowires on solid substrates up to 1 inch of diameter also enabled the observation of resonance modes associated with light trapped into the nanowires. This was proven by comparing the light absorbed and scattered by the arrays, and may be exploited to enhance light harvesting in tandem solar cells. Significantly, the control of the assembly of nanowire arrays may have a direct impact on bottom-up technologies of high anisotropy nanomaterials.

  16. Multiband Hot Photoluminescence from Nanocavity-Embedded Silicon Nanowire Arrays with Tunable Wavelength.

    PubMed

    Mu, Zhiqiang; Yu, Haochi; Zhang, Miao; Wu, Aimin; Qi, Gongmin; Chu, Paul K; An, Zhenghua; Di, Zengfeng; Wang, Xi

    2017-03-08

    Besides the well-known quantum confinement effect, hot luminescence from indirect bandgap Si provides a new and promising approach to realize monolithically integrated silicon optoelectronics due to phonon-assisted light emission. In this work, multiband hot photoluminescence is generated from Si nanowire arrays by introducing trapezoid-shaped nanocavities that support hybrid photonic-plasmonic modes. By continuously adjusting the geometric parameters of the Si nanowires with trapezoidal nanocavities, the multiband hot photoluminescence can be tuned in the range from visible to near-infrared independent of the excitation laser wavelength. The highly tunable wavelength bands and concomitant compatibility with Si-integrated electronics enable tailoring of silicon-based light sources suitable for next-generation optoelectronics devices.

  17. Comparison of ordered and disordered silicon nanowire arrays: experimental evidence of photonic crystal modes.

    PubMed

    Dhindsa, Navneet; Saini, Simarjeet S

    2016-05-01

    We experimentally compared the reflectance between ordered and disordered silicon nanowires to observe the evidence of photonic crystal modes. For similar diameters, the resonance peaks for the ordered nanowires at a spacing of 400 nm was at a shorter wavelength than the disordered nanowires, consistent to the excitation of photonic crystal modes. Furthermore, the resonant wavelength didn't shift while changing the density of the disordered nanowires, whereas there was a significant shift observed in the ordered ones. At an ordered spacing of 800 nm, the resonance wavelength approached that of the disordered structures, indicating that the ordered structures were starting to behave like individual waveguides. To our knowledge, this is the first direct experimental observation of photonic crystal modes in vertical periodic silicon nanowire arrays.

  18. Silicon material task - Low cost solar array project /JPL/DOE/

    NASA Technical Reports Server (NTRS)

    Lutwack, R.

    1979-01-01

    The paper describes the silicon material task of the low-cost solar array project, which has the objective of establishing a silicon production capability equivalent to 500 mW per year at a price less than 10 dollars/kg (1975 dollars) in 1986. The task program is divided into four phases: technical feasibility, scale-up studies (the present phase), experimental process system development units, and implementation of large-scale production plants, and it involves the development of processes for two groups of materials, that is, semiconductor grade and solar cell grade. In addition, the effects of impurities on solar cell performance are being investigated. Attention is given to problem areas of the task program, such as environmental protection, material compatibility between the reacting chemicals and materials of construction of the equipment, and waste disposal.

  19. Hexagonal arrays of round-head silicon nanopillars for surface anti-reflection applications

    NASA Astrophysics Data System (ADS)

    Yan, Wensheng; Dottermusch, Stephan; Reitz, Christian; Richards, Bryce S.

    2016-10-01

    We designed and fabricated an anti-reflection surface of hexagonal arrays of round-head silicon nanopillars. The measurements show a significant reduction in reflectivity across a broad spectral range. However, we then grew a conformal titanium dioxide coating via atomic layer deposition to achieve an extremely low weighted average reflection of 2.1% over the 460-1040 nm wavelength range. To understand the underlying reasons for the reduced reflectance, the simulations were conducted and showed that it is due to strong forward scattering of incident light into the silicon substrate. The calculated normalized scattering cross section demonstrates a broadband distribution feature, and the peak has a red-shift to longer wavelengths. Finally, we report two-dimensional weighted average reflectance as a function of both wavelength and angle of incidence and present the resulting analysis contour map.

  20. N-Type delta Doping of High-Purity Silicon Imaging Arrays

    NASA Technical Reports Server (NTRS)

    Blacksberg, Jordana; Hoenk, Michael; Nikzad, Shouleh

    2005-01-01

    A process for n-type (electron-donor) delta doping has shown promise as a means of modifying back-illuminated image detectors made from n-doped high-purity silicon to enable them to detect high-energy photons (ultraviolet and x-rays) and low-energy charged particles (electrons and ions). This process is applicable to imaging detectors of several types, including charge-coupled devices, hybrid devices, and complementary metal oxide/semiconductor detector arrays. Delta doping is so named because its density-vs.-depth characteristic is reminiscent of the Dirac delta function (impulse function): the dopant is highly concentrated in a very thin layer. Preferably, the dopant is concentrated in one or at most two atomic layers in a crystal plane and, therefore, delta doping is also known as atomic-plane doping. The use of doping to enable detection of high-energy photons and low-energy particles was reported in several prior NASA Tech Briefs articles. As described in more detail in those articles, the main benefit afforded by delta doping of a back-illuminated silicon detector is to eliminate a "dead" layer at the back surface of the silicon wherein high-energy photons and low-energy particles are absorbed without detection. An additional benefit is that the delta-doped layer can serve as a back-side electrical contact. Delta doping of p-type silicon detectors is well established. The development of the present process addresses concerns specific to the delta doping of high-purity silicon detectors, which are typically n-type. The present process involves relatively low temperatures, is fully compatible with other processes used to fabricate the detectors, and does not entail interruption of those processes. Indeed, this process can be the last stage in the fabrication of an imaging detector that has, in all other respects, already been fully processed, including metallized. This process includes molecular-beam epitaxy (MBE) for deposition of three layers, including

  1. KOH post-etching-induced rough silicon nanowire array for H2 gas sensing application

    NASA Astrophysics Data System (ADS)

    Qin, Yuxiang; Wang, Yongyao; Liu, Yi; Zhang, Xiaojuan

    2016-11-01

    The limited surface area and compacted configuration of silicon nanowires (SiNWs), which are made by one-step metal-assisted chemical etching (MACE) go against target gas diffusion and adsorbtion for gas sensing application. To harvest suitable gas sensitivity and fast response-recovery characteristics, an aligned, rough SiNW array with loose configuration and high surface area was fabricated by a two-step etching process. The MACE technique was first employed to fabricate a smooth SiNW array, and then a KOH post-etching method was developed to roughen the NW surface further. The influence of the KOH post-etching time on the array density and surface roughness of the SiNWs was investigated, and the H2-sensing properties of the sensor based on the as-fabricated rough SiNW array were evaluated systematically at room temperature. It was revealed that the post-etching of KOH roughens the NW surface effectively, and also decreases the wire diameter and array density considerably. The resulting configuration of the SiNW array with high active surface and loose geometry is favorable for gas sensing. Consequently, the rough SiNW array-based sensor exhibited a linear response to H2 with a wide range of concentrations (50-10 000 ppm) at room temperature. Good stability and selectivity, satisfying response-recovery characteristics were also achieved. However, over-etching of SiNWs by KOH solution results in a considerable decrease in surface roughness and then in the H2-sensing response of the NWs.

  2. Vapor detection performance of vertically aligned, ordered arrays of silicon nanowires with a porous electrode.

    PubMed

    Field, Christopher R; In, Hyun Jin; Begue, Nathan J; Pehrsson, Pehr E

    2011-06-15

    Vertically aligned, ordered arrays of silicon nanowires capped with a porous top electrode are used to detect gas phase ammonia and nitrogen dioxide in humidified air. The sensors had very fast response times and large signal-to-noise ratios. Calibration curves were created using both an initial slope method and a fixed-time point method. The initial-slope method had a power law dependence that correlates well with concentration, demonstrating a viable alternative for eventual quantitative vapor detection and enabling shorter sampling and regeneration times.

  3. A palladium-nanoparticle and silicon-nanowire-array hybrid: a platform for catalytic heterogeneous reactions.

    PubMed

    Yamada, Yoichi M A; Yuyama, Yoshinari; Sato, Takuma; Fujikawa, Shigenori; Uozumi, Yasuhiro

    2014-01-03

    We report the development of a silicon nanowire array-stabilized palladium nanoparticle catalyst, SiNA-Pd. Its use in the palladium-catalyzed Mizoroki-Heck reaction, the hydrogenation of an alkene, the hydrogenolysis of nitrobenzene, the hydrosilylation of an α,β-unsaturated ketone, and the C-H bond functionalization reactions of thiophenes and indoles achieved a quantitative production with high reusability. The catalytic activity reached several hundred-mol ppb of palladium, reaching a TON of 2 000 000.

  4. Design and simulation of temperature-insensitive arrayed waveguide gratings based on silicon nanowires

    NASA Astrophysics Data System (ADS)

    Chen, Yan; Lang, Tingting; Zou, Jun; He, J.-J.

    2011-12-01

    The design and simulation results of temperature-insensitive arrayed waveguide gratings based on silicon nanowires are presented. The temperature dependent wavelength shift is minimized by using negative thermo-optic coefficient material SU-8 as the upper-cladding. Simulation results show that by using an appropriate thickness and width of the waveguide, quasi-athermal operation can be achieved. For temperature varying from 0°C to 80°C, the TD-CWS can be controlled down to 0.036nm with little polarization dependence for 272nm×253nm waveguide.

  5. Micro-contacting of single and periodically arrayed columnar silicon structures by focused ion beam techniques

    SciTech Connect

    Friedrich, F. Herfurth, N.; Teodoreanu, A.-M.; Boit, C.

    2014-06-16

    Micron-sized, periodic crystalline Silicon columns on glass substrate were electrically contacted with a transparent conductive oxide front contact and a focused ion beam processed local back contact. Individual column contacts as well as arrays of >100 contacted columns were processed. Current-voltage characteristics of the devices were determined. By comparison with characteristics obtained from adapted device simulation, the absorber defect density was reconstructed. The contacting scheme allows the fabrication of testing devices in order to evaluate the electronic potential of promising semiconductor microstructures.

  6. Compact 4×4 1250GHz silicon arrayed waveguide grating router for optical interconnects

    NASA Astrophysics Data System (ADS)

    Chen, Guanting; Zou, Jun; Lang, Tingting; He, Jianjun

    2015-02-01

    A compact silicon arrayed waveguide grating router (AWGR) for optical interconnects is experimentally demonstrated. The design, fabrication and characterization of this 4×4 AWGR with a 1250 GHz channel spacing and a 5 THz free spectral range are discussed. The loss of the AWGR varies from 2.5 dB to 5.5 dB and the crosstalk is better than -18 dB. The functionality of the AWG as a router and its good rotation property are also presented. This device has a compact footprint of 0.46×0.26mm2.

  7. Fabrication of silicon nanowire arrays by near-field laser ablation and metal-assisted chemical etching

    NASA Astrophysics Data System (ADS)

    Brodoceanu, D.; Alhmoud, H. Z.; Elnathan, R.; Delalat, B.; Voelcker, N. H.; Kraus, T.

    2016-02-01

    We present an elegant route for the fabrication of ordered arrays of vertically-aligned silicon nanowires with tunable geometry at controlled locations on a silicon wafer. A monolayer of transparent microspheres convectively assembled onto a gold-coated silicon wafer acts as a microlens array. Irradiation with a single nanosecond laser pulse removes the gold beneath each focusing microsphere, leaving behind a hexagonal pattern of holes in the gold layer. Owing to the near-field effects, the diameter of the holes can be at least five times smaller than the laser wavelength. The patterned gold layer is used as catalyst in a metal-assisted chemical etching to produce an array of vertically-aligned silicon nanowires. This approach combines the advantages of direct laser writing with the benefits of parallel laser processing, yielding nanowire arrays with controlled geometry at predefined locations on the silicon surface. The fabricated VA-SiNW arrays can effectively transfect human cells with a plasmid encoding for green fluorescent protein.

  8. Multi-strip silicon sensors for beam array monitoring in micro-beam radiation therapy.

    PubMed

    Alagoz, E; Brauer-Krisch, E; Bravin, A; Cornelius, I; Fournier, P; Hansen, T E; Kok, A; Lerch, M; Monakhov, E; Morse, J; Pacifico, N; Petasecca, M; Povoli, M; Requard, H; Rozenfeld, A D; Salome, M; Sandaker, H; Stugu, B

    2016-12-01

    We present here the latest results from tests performed at the ESRF ID17 and ID21 beamlines for the characterization of novel beam monitors for Microbeam Radiation Therapy (MRT), which is currently being implemented at ID17. MRT aims at treating solid tumors by exploiting an array of evenly spaced microbeams, having an energy spectrum distributed between 27 and 600keV and peaking at 100keV. Given the high instantaneous dose delivered (up to 20kGy/s), the position and the intensity of the microbeams has to be precisely and instantly monitored. For this purpose, we developed dedicated silicon microstrip beam monitors. We have successfully characterized them, both with a microbeam array at ID17, and a submicron scanning beam at ID21. We present here the latest results obtained in recent tests along with an outlook on future developments.

  9. SERS detection of low-concentration adenosine by silver nanoparticles on silicon nanoporous pyramid arrays structure

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Man, B. Y.; Jiang, S. Z.; Yang, C.; Liu, M.; Chen, C. S.; Xu, S. C.; Qiu, H. W.; Li, Z.

    2015-08-01

    A novel surface-enhanced Raman spectroscopy (SERS) substrate based on uniform silver nanoparticles/silicon nanoporous pyramid arrays (Ag/PS) is prepared and SERS behaviors to adenosine are discussed and compared. With a low concentration of 10-7 M, the characteristic Raman bands of adenosine demonstrate the significantly high SERS sensitivity of the prepared Ag/PS substrate. A reasonable linear correlation is obtained between the intensity of SERS signal and the adenosine concentration from 10-2 to 10-7M in log scale. These results imply that the Ag/PS with regular pyramids array might be an effective substrate for performing label-free sensitive SERS detections of biomolecule.

  10. Plasmon enhanced broadband optical absorption in ultrathin silicon nanobowl array for photoactive devices applications

    SciTech Connect

    Sun, Rui-Nan; Peng, Kui-Qing Hu, Bo; Hu, Ya; Zhang, Fu-Qiang; Lee, Shuit-Tong

    2015-07-06

    Both photonic and plasmonic nanostructures are key optical components of photoactive devices for light harvesting, enabling solar cells with significant thickness reduction, and light detectors capable of detecting photons with sub-band gap energies. In this work, we study the plasmon enhanced broadband light absorption and electrical properties of silicon nanobowl (SiNB) arrays. The SiNB-metal photonic-plasmonic nanostructure-based devices exhibited superior light-harvesting ability across a wide range of wavelengths up to the infrared regime well below the band edge of Si due to effective optical coupling between the SiNB array and incident sunlight, as well as electric field intensity enhancement around metal nanoparticles due to localized surface plasmon resonance. The photonic-plasmonic nanostructure is expected to result in infrared-light detectors and high-efficiency solar cells by extending light-harvesting to infrared frequencies.

  11. Development of ORRUBA: A Silicon Array for the Measurement of Transfer Reactions in Inverse Kinematics

    SciTech Connect

    Pain, S. D.; Bardayan, Daniel W; Blackmon, Jeff C; Chae, K. Y.; Chipps, K.; Cizewski, J. A.; Hatarik, Robert; Johnson, Micah; Jones, K. L.; Kapler, R.; Kozub, R. L.; Livesay, Jake; Matei, Catalin; Moazen, Brian; Nesaraja, Caroline D; O'Malley, Patrick; Smith, Michael Scott; Swan, T. P.; Thomas, J. S.; Wilson, Gemma L

    2009-01-01

    The development of high quality radioactive beams has made possible the measurement of transfer reactions in inverse kinematics on unstable nuclei. Measurement of (d,p) reactions on neutron-rich nuclei yield data on the evolution of nuclear structure away from stability, and are of astrophysical interest. Experimentally, (d,p) reactions on heavy (Z=50) fission fragments are complicated by the strongly inverse kinematics, and relatively low beam intensities. Consequently, ejectile detection with high resolution in position and energy, a high dynamic range and a high solid angular coverage is required. The Oak Ridge Rutgers University Barrel Array (ORRUBA) is a new silicon detector array optimized for the measurement of (d,p) reactions in inverse kinematics.

  12. Plasmon enhanced broadband optical absorption in ultrathin silicon nanobowl array for photoactive devices applications

    NASA Astrophysics Data System (ADS)

    Sun, Rui-Nan; Peng, Kui-Qing; Hu, Bo; Hu, Ya; Zhang, Fu-Qiang; Lee, Shuit-Tong

    2015-07-01

    Both photonic and plasmonic nanostructures are key optical components of photoactive devices for light harvesting, enabling solar cells with significant thickness reduction, and light detectors capable of detecting photons with sub-band gap energies. In this work, we study the plasmon enhanced broadband light absorption and electrical properties of silicon nanobowl (SiNB) arrays. The SiNB-metal photonic-plasmonic nanostructure-based devices exhibited superior light-harvesting ability across a wide range of wavelengths up to the infrared regime well below the band edge of Si due to effective optical coupling between the SiNB array and incident sunlight, as well as electric field intensity enhancement around metal nanoparticles due to localized surface plasmon resonance. The photonic-plasmonic nanostructure is expected to result in infrared-light detectors and high-efficiency solar cells by extending light-harvesting to infrared frequencies.

  13. THz Direct Detector and Heterodyne Receiver Arrays in Silicon Nanoscale Technologies

    NASA Astrophysics Data System (ADS)

    Grzyb, Janusz; Pfeiffer, Ullrich

    2015-10-01

    The main scope of this paper is to address various implementation aspects of THz detector arrays in the nanoscale silicon technologies operating at room temperatures. This includes the operation of single detectors, detectors operated in parallel (arrays), and arrays of detectors operated in a video-camera mode with an internal reset to support continuous-wave illumination without the need to synchronize the source with the camera (no lock-in receiver required). A systematic overview of the main advantages and limitations in using silicon technologies for THz applications is given. The on-chip antenna design challenges and co-design aspects with the active circuitry are thoroughly analyzed for broadband detector/receiver operation. A summary of the state-of-the-art arrays of broadband THz direct detectors based on two different operation principles is presented. The first is based on the non-quasistatic resistive mixing process in a MOSFET channel, whereas the other relies on the THz signal rectification by nonlinearity of the base-emitter junction in a high-speed SiGe heterojunction bipolar transistor (HBT). For the MOSFET detector arrays implemented in a 65 nm bulk CMOS technology, a state-of-the-art optical noise equivalent power (NEP) of 14 pW/ at 720 GHz was measured, whereas for the HBT detector arrays in a 0.25 μm SiGe process technology, an optical NEP of 47 pW/ at 700 GHz was found. Based on the implemented 1k-pixel CMOS camera with an average power consumption of 2.5 μW/pixel, various design aspects specific to video-mode operation are outlined and co-integration issues with the readout circuitry are analyzed. Furthermore, a single-chip 2 × 2 array of heterodyne receivers for multi-color active imaging in a 160-1000 GHz band is presented with a well-balanced NEP across the operation bandwidth ranging from 0.1 to 0.24 fW/Hz (44.1-47.8 dB single-sideband NF) and an instantaneous IF bandwidth of 10 GHz. In its present implementation, the receiver RF

  14. Electrochemical biosensor array for liver diagnosis using silanization technique on nanoporous silicon electrode.

    PubMed

    Song, Min-Jung; Yun, Dong-Hwa; Min, Nam-Ki; Hong, Suk-In

    2007-01-01

    An electrochemical biosensor array system was fabricated for the diagnosis and monitoring of liver diseases. Analysis on this array system with multiple samples was performed for point-of-care testing or home-use applications. Cholesterol, bilirubin and aminotransferases present in the serum are well-known biomarkers for liver diseases. For this study, we describe our biosensor array system consisting of cholesterol, bilirubin and glutamate sensors. To immobilize sensing enzymes on the array system, we employed a silanization technique. We observed that porous silicon layers formed on each working electrode notably increase the effective surface area. Sensing electrodes were placed in sampling wells to minimize the cross-interference effect so that multiple sampling would be possible with a low noise current. Compared with traditional analyte measurement procedures, our novel analytical device demonstrated acceptable sensitivities for the analyses of multiple samples and analytes without a marked cross-interference effect. The device sensitivities observed were 0.2656 microA/mM for cholesterol, 0.15354 mA/mM for bilirubin, 0.13698 microA/(U/l) for alanine aminotransferase (ALT) and 0.45439 microA/(U/l) for aspartate aminotransferase (AST).

  15. Preparing magnetic yttrium iron garnet nanodot arrays by ultrathin anodic alumina template on silicon substrate

    SciTech Connect

    Zheng, Hui; Han, Mangui Deng, Longjiang; Zheng, Liang; Zheng, Peng; Qin, Huibin; Wu, Qiong

    2015-08-10

    Ultrahigh density periodically ordered magnetic yttrium iron garnet (Y{sub 3}Fe{sub 5}O{sub 12}, YIG) nanodot arrays have been prepared by pulsed laser deposition through an ultrathin alumina mask (UTAM). UTAM having periodically ordered circularly shaped holes with 350 nm in diameter, 450 nm in inter-pore distance, and 700 nm in height has been prepared on silicon substrate. Furthermore, the microstructure and magnetic properties of YIG nanodot arrays have been characterized. Nanodot arrays with a sharp distribution in diameter centered at 340 nm with standard deviation of 10 nm have been fabricated. Moreover, typical hysteresis loops and ferromagnetic resonance spectra in in-plane and out-of-plane revealed that this unique structure greatly influences the magnetics properties of YIG. First, coercivity of YIG nanodot arrays in in-plane was increased about from 15 Oe of YIG films to 500 Oe. Then, the degree of uniformity about nanodot height decided that two or more resonance peaks in out-of-plane were detected in the spectra. The peak-to-peak linewidth values were about 94 Oe and 40 Oe in the parallel and perpendicular directions, respectively, which indicated that the values were larger by the two-magnon scattering. Consequently, this pattering method creates opportunities for studying physics in oxide nanomagnets and may be applied in spin-wave devices.

  16. A low-profile three-dimensional neural probe array using a silicon lead transfer structure

    NASA Astrophysics Data System (ADS)

    Cheng, Ming-Yuan; Je, Minkyu; Tan, Kwan Ling; Lim Tan, Ee; Lim, Ruiqi; Yao, Lei; Li, Peng; Park, Woo-Tae; Phua, Eric Jian Rong; Lip Gan, Chee; Yu, Aibin

    2013-09-01

    This paper presents a microassembly method for low-profile three-dimensional probe arrays for neural prosthesis and neuroscience applications. A silicon (Si) lead transfer structure, Si interposer, is employed to form electrical connections between two orthogonal planes—the two dimensional probes and the dummy application-specific integrated circuit (ASIC) chip. In order to hold the probe array and facilitate the alignment of probes during assembly, a Si platform is designed to have through-substrate slots for the insertion of probes and cavities for holding the Si interposers. The electrical interconnections between the probes and the dummy ASIC chip are formed by solder reflow, resulting in greatly improved throughput in the proposed assembly method. Moreover, since the backbone of the probe can be embedded inside the cavity of the Si platform, the profile of the probe array above the cortical surface can be controlled within 750 µm. This low-profile allows the probe array not to touch the skull after it is implanted on the brain. The impedance of the assembled probe is also measured and discussed.

  17. On-line coupling of a microelectrode array equipped poly(dimethylsiloxane) microchip with an integrated graphite electrospray emitter for electrospray ionisation mass spectrometry.

    PubMed

    Liljegren, Gustav; Dahlin, Andreas; Zettersten, Camilla; Bergquist, Jonas; Nyholm, Leif

    2005-10-01

    A novel method for the manufacturing of microchips for on-chip combinations of electrochemistry (EC) and sheathless electrospray ionisation mass spectrometry (ESI-MS) is described. The technique, which does not require access to clean-room facilities, is based on the incorporation of an array of gold microcoil electrodes into a poly(dimethylsiloxane)(PDMS) microflow channel equipped with an integrated graphite based sheathless ESI emitter. Electrochemical measurements, which were employed to determine the electroactive area of the electrodes and to test the microchips, show that the manufacturing process was reproducible and that the important interelectrode distance in the electrochemical cell could to be adequately controlled. The EC-ESI-MS device was evaluated based on the ESI-MS detection of the oxidation products of dopamine. The results demonstrate that the present on-chip approach enables full potentiostatic control of the electrochemical cell and the attainment of very short transfer times between the electrochemical cell and the electrospray emitter. The transfer times were 0.6 and 1.2 s for flow rates of 1.0 and 0.5 microL min(-1), respectively, while the electrochemical conversion efficiency of the electrochemical cell was found to be 30% at a flow rate of 0.5 microL min(-1). To decouple the electrochemical cell from the ESI-MS high voltage and to increase the user-friendliness, the on-line electrochemistry-ESI-MS experiments were performed using a wireless Bluetooth battery-powered instrument with the chip floating at the potential induced by the ESI high voltage. The described on-chip EC-ESI-MS device can be used for fundamental electrochemical investigations as well as for applications based on the use of electrochemically controlled sample pretreatment, preconcentration and ionisation steps prior to ESI-MS.

  18. Silicon nanowire arrays-induced graphene oxide reduction under UV irradiation.

    PubMed

    Fellahi, Ouarda; Das, Manash R; Coffinier, Yannick; Szunerits, Sabine; Hadjersi, Toufik; Maamache, Mustapha; Boukherroub, Rabah

    2011-11-01

    This paper reports on efficient UV irradiation-induced reduction of exfoliated graphene oxide. Direct illumination of an aqueous solution of graphene oxide at λ = 312 nm for 6 h resulted in the formation of graphene nanosheets dispersible in water. X-Ray photoelectron spectroscopy (XPS), UV-vis spectroscopy, atomic force microscopy (AFM) and electrochemical measurements (cyclic voltammetry and electrochemical impedance spectroscopy) suggest a restoration of the sp(2) carbon network. The results were compared with graphene nanosheets prepared by photochemical irradiation of a GO aqueous solution in the presence of hydrogenated silicon nanowire (SiNW) arrays or silicon nanowire arrays decorated with silver (SiNW/Ag NPs) or copper nanoparticles (SiNW/Cu NPs). Graphene nanosheets obtained by illumination of the GO aqueous solution at 312 nm for 6 h in the presence of SiNW/Cu NPs exhibited superior electrochemical charge transfer characteristics. This is mainly due to the higher amount of sp(2)-hybridized carbon in these graphene sheets found by XPS analysis. The high level of extended conjugated carbon network was also evident by the water insoluble nature of the resulting graphene nanosheets, which precipitated upon photochemical reduction.

  19. Morphology dependent field emission characteristics of ZnS/silicon nanoporous pillar array

    NASA Astrophysics Data System (ADS)

    Wang, Ling Li; Zhao, Cheng Zhou; Kang, Li Ping; Liu, De Wei; Zhao, Hui Chun; Hao, Shan Peng; Zhang, Yuan Kai; Chen, Zhen Ping; Li, Xin Jian

    2016-10-01

    Through depositing zinc sulphide (ZnS) nanoparticals on silicon nanoporous pillar array (Si-NPA) and crater-shaped silicon nanoporous pillar array (c-Si-NPA) by chemical bath deposition (CBD) method, ZnS/Si-NPA and c-ZnS/Si-NPA were prepared and the field emission (FE) properties of them were investigated. The turn-on electric fields of were 3.8 V/mm for ZnS/Si-NPA and 5.0 V/mm for c-ZnS/Si-NPA, respectively. The lower turn-on electric fields of ZnS/Si-NPA than that of c-ZnS/Si-NPA were attributed to the different electric distribution of the field emitters causing by the different surface morphology of the two samples, which was further demonstrated via the simulated results by finite element modeling. The FN curves for the ZnS/Si-NPA showed two-slope behavior. All the results indicate that the morphology play an important role in the FE properties and designing an appropriate top morphology for the emitter is a very efficient way to improve the FE performance.

  20. Periodic Organic–Inorganic Halide Perovskite Microplatelet Arrays on Silicon Substrates for Room‐Temperature Lasing

    PubMed Central

    Niu, Lin; Wu, Chunyang; Cong, Chunxiao; Wang, Hong; Zeng, Qingsheng; He, Haiyong; Fu, Qundong; Fu, Wei; Yu, Ting; Jin, Chuanhong

    2016-01-01

    Organic–inorganic metal halide perovskites have recently demonstrated outstanding efficiencies in photovoltaics as well as highly promising performances for a wide range of optoelectronic applications such as lasing, light emission, optical detectors, and even for radiation detection. Key to the realization of functional perovskite micro/nanosystems on the ubiquitous silicon optoelectronics platform is through sophisticated lithography. Despite the rapid progress made in halide perovskite lasing, direct lithographic patterning of perovskite films to form optical cavities on conventional substrates remains extremely challenging. This study realizes room‐temperature high‐quality factor whispering‐gallery‐mode lasing (Q ≈ 1210) from patterned lead halide perovskite microplatelets fabricated in periodic arrays on silicon substrate with micropatterned BN film as the buffer layer. By varying the size of the platelets, modal selectivity for single mode lasing can be achieved with different cavity sizes or by simply breaking the structural symmetry of the cavity through designing the pattern. Importantly, this work demonstrates a straightforward, versatile bottom‐up scalable strategy to realize high‐quality periodic perovskite arrays with variable cavity sizes for large‐area light‐emitting and optical gain applications. PMID:27980989

  1. Ultra-sensitive detection of adipocytokines with CMOS-compatible silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Pui, Tze-Sian; Agarwal, Ajay; Ye, Feng; Tou, Zhi-Qiang; Huang, Yinxi; Chen, Peng

    2009-09-01

    Perfectly aligned arrays of single-crystalline silicon nanowires were fabricated using top-down CMOS-compatible techniques. We demonstrate that these nanowire devices are able to detect adipocytokines secreted by adipose cells with femtomolar sensitivity, high specificity, wide detection range, and ability for parallel monitoring. The nanowire sensors also provide a novel tool to reveal the poorly understood signaling mechanisms of these newly recognized signaling molecules, as well as their relevance in common diseases such as obesity and diabetes.Perfectly aligned arrays of single-crystalline silicon nanowires were fabricated using top-down CMOS-compatible techniques. We demonstrate that these nanowire devices are able to detect adipocytokines secreted by adipose cells with femtomolar sensitivity, high specificity, wide detection range, and ability for parallel monitoring. The nanowire sensors also provide a novel tool to reveal the poorly understood signaling mechanisms of these newly recognized signaling molecules, as well as their relevance in common diseases such as obesity and diabetes. Electronic supplementary information (ESI) available: Process diagram of nanowire fabrication; specificity of nanowire detection; induced differentiation of 3T3-L1 cells. See DOI: 10.1039/b9nr00092e

  2. Single domain antibodies for the detection of ricin using silicon photonic microring resonator arrays.

    PubMed

    Shia, Winnie W; Bailey, Ryan C

    2013-01-15

    Ricin is a lethal protein toxin derived from the castor bean plant. Given its notorious history as a biowarfare agent and homicidal weapon, ricin has been classified as a category B bioterrorism agent. Current ricin detection methods based on immunoassays lack the required sensitivity and specificity for many homeland security surveillance applications. Importantly, many conventional antibody-based methodologies are unable to distinguish ricin from RCA 120, a nontoxic protein also found in the castor bean plant. Single domain antibodies (sdAbs), which are recombinantly derived from immunized llamas, are known to have high affinities for ricin A or B chains and low cross-reactivity with RCA 120. Herein, we demonstrate the use of silicon photonic microring resonators for antibody affinity profiling and one-step ricin detection at concentrations down to 300 pM using a 15 min, label-free assay format. These sdAbs were also simultaneously compared with a commercial anti-RCA IgG antibody in a multicapture agent, single target immunoassay using arrays of microrings, which allowed direct comparison of sensitivity and specificity. A selected sdAb was also found to exhibit outstanding specificity against another biotoxin, saporin, which has mechanism of action similar to ricin. Given the rapidity, scalability, and multiplexing capability of this silicon-based technology, this work represents a step toward using microring resonator arrays for the sensitive and specific detection of biowarfare agents.

  3. Evaluation of Matrix9 silicon photomultiplier array for small-animal PET

    PubMed Central

    Du, Junwei; Schmall, Jeffrey P.; Yang, Yongfeng; Di, Kun; Roncali, Emilie; Mitchell, Gregory S.; Buckley, Steve; Jackson, Carl; Cherry, Simon R.

    2015-01-01

    Purpose: The MatrixSL-9-30035-OEM (Matrix9) from SensL is a large-area silicon photomultiplier (SiPM) photodetector module consisting of a 3 × 3 array of 4 × 4 element SiPM arrays (total of 144 SiPM pixels) and incorporates SensL’s front-end electronics board and coincidence board. Each SiPM pixel measures 3.16 × 3.16 mm2 and the total size of the detector head is 47.8 × 46.3 mm2. Using 8 × 8 polished LSO/LYSO arrays (pitch 1.5 mm) the performance of this detector system (SiPM array and readout electronics) was evaluated with a view for its eventual use in small-animal positron emission tomography (PET). Methods: Measurements of noise, signal, signal-to-noise ratio, energy resolution, flood histogram quality, timing resolution, and array trigger error were obtained at different bias voltages (28.0–32.5 V in 0.5 V intervals) and at different temperatures (5 °C–25 °C in 5 °C degree steps) to find the optimal operating conditions. Results: The best measured signal-to-noise ratio and flood histogram quality for 511 keV gamma photons were obtained at a bias voltage of 30.0 V and a temperature of 5 °C. The energy resolution and timing resolution under these conditions were 14.2% ± 0.1% and 4.2 ± 0.1 ns, respectively. The flood histograms show that all the crystals in the 1.5 mm pitch LSO array can be clearly identified and that smaller crystal pitches can also be resolved. Flood histogram quality was also calculated using different center of gravity based positioning algorithms. Improved and more robust results were achieved using the local 9 pixels for positioning along with an energy offset calibration. To evaluate the front-end detector readout, and multiplexing efficiency, an array trigger error metric is introduced and measured at different lower energy thresholds. Using a lower energy threshold greater than 150 keV effectively eliminates any mispositioning between SiPM arrays. Conclusions: In summary, the Matrix9 detector system can resolve

  4. Evaluations of candidate encapsulation designs and materials for low-cost silicon photovoltaic arrays

    NASA Technical Reports Server (NTRS)

    Gaines, G. B.; Carmichael, D. C.; Sliemers, F. A.; Brockway, M. C.; Bunk, A. R.; Nance, G. P.

    1978-01-01

    Three encapsulation designs for silicon photovoltaic arrays based on cells with silk-screened Ag metallization have been evaluated: transparent polymeric coatings over cells laminated between two films or sheets of polymeric materials; cells adhesively bonded to a glass cover with a polymer pottant and a glass or other substrate component. Silicone and acrylic coatings were assessed, together with acrylic sheet, 0.635 mm fiberglass-reinforced polyester sheet, 0.102 mm polycarbonate/acrylic dual-layer film, 0.127 mm fluorocarbon film, soda-lime glass, borosilicate glass, low-iron glass, and several adhesives. The encapsulation materials were characterized by light transmittance measurements, determination of moisture barrier properties and bond strengths, and by the performance of cells before and after encapsulation. Silicon and acrylic coatings provided inadequate protection. Acrylic and fluorocarbon films displayed good weatherability and acceptable optical transmittance. Borosilicate, low-iron and soda-lime-float glasses were found to be acceptable candidate encapsulants for most environments.

  5. Subwavelength silicon through-hole arrays as an all-dielectric broadband terahertz gradient index metamaterial

    SciTech Connect

    Park, Sang-Gil; Jeong, Ki-Hun; Lee, Kanghee; Han, Daehoon; Ahn, Jaewook

    2014-09-01

    Structuring at subwavelength scales brings out artificial media with anomalous optical features called metamaterials. All-dielectric metamaterials have high potential for practical applications over the whole electromagnetic spectrum owing to low loss and optical isotropy. Here, we report subwavelength silicon through-hole arrays as an all-dielectric gradient index metamaterial with broadband THz operation. The unit cell consists of a single subwavelength through-hole on highly resistive monocrystalline silicon. Depending on the fill-factor and period, the effective index was linearly modulated at 0.3–1.6 THz. The experimental results also demonstrate silicon gradient refractive index (Si-GRIN) lenses with parabolic index profiles through the spatial modification of a single unit cell along the radial direction. Si-GRIN lenses either focus 0.4–1.6 THz beam to the diffraction-limit or serve as a flat and thin solid immersion lens on the backside of THz photoconductive antenna for highly efficient pulse extraction. This all-dielectric gradient index metamaterial opens up opportunities for integrated THz GRIN optics.

  6. Specific immobilization of human immunoglobulin G on gold-coated silicon microcantilever array

    NASA Astrophysics Data System (ADS)

    Vashist, Sandeep Kumar; Tewari, Rupinder; Bajpai, Ram Prakash; Bharadwaj, Lalit Mohan; Raiteri, Roberto

    2007-01-01

    We demonstrate a procedure for immobilizing human immunoglobulin G (IgG) on an array of gold-coated silicon microcantilevers. The procedure employed protein A for the specific immobilization of human IgG on the gold surface. Protein A bound specifically to the gold-coated upper surface of the silicon microcantilever and had no interaction with the silicon surface. It binds to the constant F c regions of human IgG keeping the antigen binding sites on the variable F ab region free to bind to antigens. Fluorescent microscopy was done to analyze qualitatively the biomolecular binding of human IgG using FITC labeled goat anti-human IgG. The immobilization densities of protein A and human IgG were 112+/-19 ng/cm2 and 629+/-23ng/cm2, as determined employing horse radish peroxidase (HRP) labeled biomolecules by 3, 3', 4, 4'-tetramethyl benzidine (TMB) substrate assay. The uniformness of the biomolecular coatings was further determined by atomic force microscopy (AFM). Surface plasmon resonance (SPR) was used to cross-validate the immobilization density of functional human IgG molecules immobilized on the gold surface w.r.t. that obtained by TMB substrate assay.

  7. Modeling and Simulation of Microelectrode-Retina Interactions

    SciTech Connect

    Beckerman, M

    2002-11-30

    The goal of the retinal prosthesis project is the development of an implantable microelectrode array that can be used to supply visually-driven electrical input to cells in the retina, bypassing nonfunctional rod and cone cells, thereby restoring vision to blind individuals. This goal will be achieved through the study of the fundamentals of electrical engineering, vision research, and biomedical engineering with the aim of acquiring the knowledge needed to engineer a high-density microelectrode-tissue hybrid sensor that will restore vision to millions of blind persons. The modeling and simulation task within this project is intended to address the question how best to stimulate, and communicate with, cells in the retina using implanted microelectrodes.

  8. Fabrication and demonstration of 1 × 8 silicon-silica multi-chip switch based on optical phased array

    NASA Astrophysics Data System (ADS)

    Katayose, Satomi; Hashizume, Yasuaki; Itoh, Mikitaka

    2016-08-01

    We experimentally demonstrated a 1 × 8 silicon-silica hybrid thermo-optic switch based on an optical phased array using a multi-chip integration technique. The switch consists of a silicon chip with optical phase shifters and two silica-based planar lightwave circuit (PLC) chips composed of optical couplers and fiber connections. We adopted a rib waveguide as the silicon waveguide to reduce the coupling loss and increase the alignment tolerance for coupling between silicon and silica waveguides. As a result, we achieved a fast switching response of 81 µs, a high extinction ratio of over 18 dB and a low insertion loss of 4.9-8.1 dB including a silicon-silica coupling loss of 0.5 ± 0.3 dB at a wavelength of 1.55 µm.

  9. Plasmonic enhancement of amorphous silicon solar photovoltaic cells with hexagonal silver arrays made with nanosphere lithography

    NASA Astrophysics Data System (ADS)

    Zhang, C.; Guney, D. O.; Pearce, J. M.

    2016-10-01

    Nanosphere lithography (NSL) provides an opportunity for a low-cost and scalable method to optically engineer solar photovoltaic (PV) cells. For PV applications, NSL is widely used in rear contact scenarios to excite surface plasmon polariton and/or high order diffractions, however, the top contact scenarios using NSL are rare. In this paper a systematic simulation study is conducted to determine the capability of achieving efficiency enhancement in hydrogenated amorphous silicon (a-Si:H) solar cells using NSL as a top contact plasmonic optical enhancer. The study focuses on triangular prism and sphere arrays as they are the most commonly and easily acquired through direct deposition or low-temperature annealing, respectively. For optical enhancement, a characteristic absorption profile is generated and analyzed to determine the effects of size, shape and spacing of plasmonic structures compared to an un-enhanced reference cell. The factors affecting NSL-enhanced PV performance include absorption, shielding effects, diffraction, and scattering. In the triangular prism array, parasitic absorption of the silver particles proves to be problematic, and although it can be alleviated by increasing the particle spacing, no useful enhancement was observed in the triangular prism arrays that were simulated. Sphere arrays, on the other hand, have broad scattering cross-sections that create useful scattering fields at several sizes and spacing intervals. For the simulated sphere arrays the highest enhancement found was 7.4%, which was fabricated with a 250 nm radius nanosphere and a 50 nm silver thickness, followed by annealing in inert gas. These results are promising and provide a path towards the commercialization of plasmonic a-Si:H solar cells using NSL fabrication techniques.

  10. The status of lightweight photovoltaic space array technology based on amorphous silicon solar cells

    NASA Technical Reports Server (NTRS)

    Hanak, Joseph J.; Kaschmitter, Jim

    1991-01-01

    Ultralight, flexible photovoltaic (PV) array of amorphous silicon (a-Si) was identified as a potential low cost power source for small satellites. A survey was conducted of the status of the a-Si PV array technology with respect to present and future performance, availability, cost, and risks. For existing, experimental array blankets made of commercial cell material, utilizing metal foil substrates, the Beginning of Life (BOL) performance at Air Mass Zero (AM0) and 35 C includes total power up to 200 W, power per area of 64 W/sq m and power per weight of 258 W/kg. Doubling of power per weight occurs when polyimide substrates are used. Estimated End of Life (EOL) power output after 10 years in a nominal low earth orbit would be 80 pct. of BOL, the degradation being due to largely light induced effects (-10 to -15 pct.) and in part (-5 pct.) to space radiation. Predictions for the year 1995 for flexible PV arrays, made on the basis of published results for rigid a-Si modules, indicate EOL power output per area and per weight of 105 W/sq m and 400 W/kg, respectively, while predictions for the late 1990s based on existing U.S. national PV program goals indicate EOL values of 157 W/sq m and 600 W/kg. Cost estimates by vendors for 200 W ultralight arrays in volume of over 1000 units range from $100/watt to $125/watt. Identified risks include the lack of flexible, space compatible encapsulant, the lack of space qualification effort, recent partial or full acquisitions of US manufacturers of a-Si cells by foreign firms, and the absence of a national commitment for a long range development program toward developing of this important power source for space.

  11. Delayed fracture of silicon: Silicon sheet growth development for the large area silicon sheet task of the low cost silicon solar array project

    NASA Technical Reports Server (NTRS)

    Chen, T. J.; Knapp, W. J.

    1978-01-01

    Bar specimens were cut from ingots of single crystal silicon, and acid etched prior to testing. Artificial surface flaws were introduced in specimens by indentation with a Knoop hardness tester. The specimens were loaded in four-point bending to 95 percent of the nominal fracture stress, while keeping the surface area, containing the flaw, wet with test liquids. No evidence of delayed fracture, and, therefore stress corrosion, of single crystal silicon was observed for liquid environments including water, acetone, and aqueous solutions of NaCl, NH4OH, and HNO3, when tested with a flaw parallel to a (110) surface. The fracture toughness was calculated.

  12. A novel method for fabrication of high-frequency (>100 MHz) ZnO ultrasonic array transducers on silicon substrates

    NASA Astrophysics Data System (ADS)

    Xu, W. J.; Ji, X. M.; Gao, J. M.; Carlier, J.; Zhang, J. Y.; Nongaillard, B.; Huang, Y. P.; Piwakowski, B.

    2012-05-01

    High-frequency ultrasonic transducer arrays are essential for efficient imaging in clinical analysis and nondestructive evaluation (NDE). However, the fabrication of piezoelectric transducers is really a great challenge due to the small features in an array. A novel technique is presented to fabricate thick-film ZnO ultrasonic array transducers. Piezoelectric elements are formed by sputtering thick-film ZnO onto etched features of a silicon substrate so that the difficult etching process for ZnO films is avoided by etching silicon. This process is simple and efficient. A 13-μm-pitch ZnO sandwich array is achieved with a thickness of 8 μm for 300 MHz. Finite element method is employed to simulate the wave propagation in water based on this new transducer configuration. The acoustic field results indicate this configuration has an acceptable performance. A potential application is proposed based on integration with microfluidics.

  13. A review and analysis on growth and optical absorption properties of silicon nanowire array for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Sharma, Ritu; Dusad, Lalit Kumar

    2015-11-01

    In this paper, optical absorptions in silicon nanowires (SiNWs) arrays obtained from theoretical studies and experimental approaches have been reviewed. A brief description on the different growth techniques for SiNW arrays reported so far is presented. Comparative analysis based on major research findings has been done and the advantages of SiNW-based solar cells over thin film solar cells are presented. Furthermore, future aspects of the use of SiNWs for photovoltaic applications are discussed.

  14. A vertical tip-tip contact silicon nanowire array for gas sensing.

    PubMed

    Lin, Leimiao; Liu, Dong; Chen, Qiaofen; Zhou, Hongzhi; Wu, Jianmin

    2016-10-20

    Novel chemiresistive gas sensors based on a vertical tip-tip contact silicon nanowire (TTC-SiNW) array were constructed. The welding of TTC-SiNWs after joule heating treatment was confirmed by a current-voltage curve (I-V curve). The TTC-SiNW structure not only resolved the problem of electrode contact encountered in conventional nanowire sensors, but also elongated the nanowire length to increase the void space for fast gas diffusion. The TTC-SiNW sensor comprising the same two types of SiNW arrays responded to NO2 very sensitively. The LOD for the p-p and n-n contact SiNW arrays is around 150 ppb and 3 ppb (S/N = 3), respectively. Furthermore, the highly oriented nano-junction formed on the TTC structure provided solid evidence to clarify the contribution of the nanojunction to gas sensing behavior. The TTC-SiNW sensor with a p-n junction displays a significant rectification effect. The sensitive response towards NO2 (LOD is about 18 ppb) was observed at a reverse bias voltage, whereas the response at a forward bias voltage was insignificant. Finally, the mechanism of gas sensing behavior on different types of TTC structures was proposed.

  15. Simulation Analysis on Photoelectric Conversion Characteristics of Silicon Nanowire Array Photoelectrodes.

    PubMed

    Zhao, Yong; Yu, Jin; Fang, Li-Guang; Zheng, Jun; Wang, Hui-Qin; Yuan, Ji-Ren; Wu, Shaolong; Cheng, Guo-An

    2015-12-01

    Semiconductor nanowire photoelectrochemical cells have attracted extensive attention in the light-conversion field owing to the low-cost preparation, excellent optical absorption, and short distance of carrier collection. Although there are numbers of experimental investigations to improve the device performance, the understanding of the detailed process of photoelectric conversion needs to be further improved. In this work, a thorough optoelectronic simulation is employed to figure out how the nanowire diameter, doping concentration, and illumination wavelength affect the photoelectric conversion characteristics of the silicon nanowire array photoelectrodes. We find that two balances should be carefully weighted between optical absorption and photogenerated-carrier collection, along with between short-circuit photocurrent density and open-circuit voltage. For the small-diameter nanowire array photoelectrodes, the overall absorption is higher than that of the larger-diameter ones with the most contribution from the nanowires. However, the substrate shows increasing absorption with increasing illumination wavelength. Higher doping density leads to a larger open-circuit voltage; while lower doping density can guarantee a relatively higher short-circuit photocurrent. To obtain high-light-conversion-efficiency photoelectrodes, the doping density should be carefully chosen with considerations of illumination wavelength and surface recombination. Suppressing the surface recombination velocity can effectively enhance the short-circuit photocurrent (open-circuit voltage) for the lightly (heavily) doped nanowire array photoelectrodes. Our systematical results provide a theoretical guidance for the photoelectrochemical devices based on semiconductor nanostructures.

  16. Fabrication of 721-pixel silicon lens array of an MKID camera

    NASA Astrophysics Data System (ADS)

    Mitsui, Kenji; Nitta, Tom; Okada, Norio; Sekímoto, Yutaro; Karatsu, Kenichi; Sekiguchi, Shigeyuki; Sekine, Masakazu; Noguchi, Takashi

    2014-07-01

    We have been developing a lens-integrated superconducting camera for millimeter and submillimeter astronomy. High-purity silicon (Si) is suitable for the lens array of the Microwave Kinetic Inductance Detector (MKID) camera due to the high refractive index and the low dielectric loss at low temperature. The camera is antenna-coupled Al coplanar waveguides on a Si substrate. Thus the lens and the device are made of the same material. We report a fabrication method of 721 pixel Si lens array with anti-reflection coating. The Si lens array was fabricated with an ultra-precision cutting machine. It uses TiAlN coated carbide end mills attached with a high-speed spindle. The shape accuracy was less than 50 μm peak-to-valley and the surface roughness was Ra 1.8 μm. The mixed epoxy was used as anti-reflection coating to adjust the refractive index. It was shaved to make the thickness of 185 μm for 220 GHz. Narrow grooves were made between the lenses to prevent cracking due to different thermal expansion coefficients of Si and the epoxy. The surface roughness of the anti-reflection coating was Ra 2.4 ~ 4.2 μm.

  17. Fabrication of 721-pixel silicon lens array of a microwave kinetic inductance detector camera

    NASA Astrophysics Data System (ADS)

    Mitsui, Kenji; Nitta, Tom; Okada, Norio; Sekimoto, Yutaro; Karatsu, Kenichi; Sekiguchi, Shigeyuki; Sekine, Masakazu; Noguchi, Takashi

    2015-04-01

    We have been developed a lens-integrated superconducting camera for millimeter and submillimeter astronomy. High-purity silicon (Si) is suitable for the lens array of the microwave kinetic inductance detector camera due to its high refractive index and low dielectric loss at low temperatures. The camera is an antenna-coupled Al coplanar waveguide on a Si substrate. Thus the lens and the device are made of the same material. We report a fabrication method of a 721-pixel Si lens array with an antireflection (AR) coating. The Si lens array was fabricated with an ultraprecision cutting machine. It uses TiAlN-coated carbide end mills attached with a high-speed spindle. The shape accuracy was less than 50 μm peak-to-valley and the surface roughness was arithmetic average roughness (Ra) of 1.8 μm. The mixed epoxy was used as an AR coating to adjust the refractive index. It was shaved to yield a thickness of 185 μm for 220 GHz. Narrow grooves were made between the lenses to prevent cracking due to the different thermal expansion coefficients of Si and the epoxy. The surface roughness of the AR coating was Ra of 2.4 to 4.2 μm.

  18. Controllable shrinking of inverted-pyramid silicon nanopore arrays by dry-oxygen oxidation.

    PubMed

    Deng, Tao; Chen, Jian; Li, Mengwei; Wang, Yifan; Zhao, Chenxu; Zhang, Zhonghui; Liu, Zewen

    2013-12-20

    A novel and simple technique for the controllable shrinkage of inverted-pyramid silicon (Si) nanopore arrays is reported. The Si nanopore arrays with sizes from 60 to 150 nm, made using a combination of dry and wet etching, were shrunk to sub 10 nm, or even closed, using direct dry-oxygen oxidation at 900 ° C. The shrinkage process of the pyramidal nanopore induced by oxidation was carefully modeled and simulated. The simulation was found to be in good agreement with the experimental data within most of the oxidation time range. Using this method, square nanopore arrays with an average size of 30 nm, and rectangular nanopores and nanoslits with feature sizes as small as 8 nm, have been obtained. Furthermore, focused ion beam cutting experiments revealed that the inner structure of the nanopore after the shrinkage kept its typical inverted-pyramid shape, which is of importance in many fields such as biomolecular sensors and ionic analogs of electronic devices, as well as nanostencils for surface nano-patterning.

  19. Effect of acid vapor etching on morphological and opto-electric properties of flat silicon and silicon nanowire arrays: A comparative study

    NASA Astrophysics Data System (ADS)

    Amri, Chohdi; Ouertani, Rachid; Hamdi, Abderrahmen; Ezzaouia, Hatem

    2016-03-01

    In this paper, we report a comparative study between porous silicon (pSi) and porous silicon nanowires (pSiNWs). Acid Vapor Etching (AVE) treatment has been used to perform porous structure on flat Si and SiNWs array substrates respectively. SiNW structure is prepared by the widely used Silver catalyzed etching method. SEM and TEM images show that AVE treatment induces porous structure in the whole Si wafer and the SiNW sidewall. Comparatively to pSi, pSiNWs exhibit a low reflectivity in the whole spectral range which decreases with etching duration. However, the reflectivity of pSi changes with porous layer thickness. Both pSi and pSiNWs exhibit a significant PL peak situated at 2 eV. PL peaks are attributed to the quantum confinement effect in the silicon nanocrystallites (SiNCs). We discussed the significant enhancement in the peak intensities and a shift toward lower energy displayed in Raman spectra for both pSi and pSiNWs. We reported a correlative study of the AVE treatment effect on the minority carrier life time of flat silicon and SiNW arrays with the passivation effect of chemical induced silicon oxides highlighted by FTIR spectra.

  20. Broadband High Efficiency Fractal-Like and Diverse Geometry Silicon Nanowire Arrays for Photovoltaic Applications

    NASA Astrophysics Data System (ADS)

    AL-Zoubi, Omar H.

    Solar energy has many advantages over conventional sources of energy. It is abundant, clean and sustainable. One way to convert solar energy directly into electrical energy is by using the photovoltaic solar cells (PVSC). Despite PVSC are becoming economically competitive, they still have high cost and low light to electricity conversion efficiency. Therefore, increasing the efficiency and reducing the cost are key elements for producing economically more competitive PVSC that would have significant impact on energy market and saving environment. A significant percentage of the PVSC cost is due to the materials cost. For that, thin films PVSC have been proposed which offer the benefits of the low amount of material and fabrication costs. Regrettably, thin film PVSC show poor light to electricity conversion efficiency because of many factors especially the high optical losses. To enhance conversion efficiency, numerous techniques have been proposed to reduce the optical losses and to enhance the absorption of light in thin film PVSC. One promising technique is the nanowire (NW) arrays in general and the silicon nanowire (SiNW) arrays in particular. The purpose of this research is to introduce vertically aligned SiNW arrays with enhanced and broadband absorption covering the entire solar spectrum while simultaneously reducing the amount of material used. To this end, we apply new concept for designing SiNW arrays based on employing diversity of physical dimensions, especially radial diversity within certain lattice configurations. In order to study the interaction of light with SiNW arrays and compute their optical properties, electromagnetic numerical modeling is used. A commercial numerical electromagnetic solver software package, high frequency structure simulation (HFSS), is utilized to model the SiNW arrays and to study their optical properties. We studied different geometries factors that affect the optical properties of SiNW arrays. Based on this study, we

  1. Silicon-on-ceramic process: Silicon sheet growth and device development for the large-area silicon sheet task of the low-cost solar array project

    NASA Technical Reports Server (NTRS)

    Whitehead, A. B.; Zook, J. D.; Grung, B. L.; Heaps, J. D.; Schmit, F.; Schuldt, S. B.; Chapman, P. W.

    1981-01-01

    The technical feasibility of producing solar cell quality sheet silicon to meet the DOE 1986 cost goal of 70 cents/watt was investigated. The silicon on ceramic approach is to coat a low cost ceramic substrate with large grain polycrystalline silicon by unidirectional solidification of molten silicon. Results and accomplishments are summarized.

  2. A Silicon-Based Nanothin Film Solid Oxide Fuel Cell Array with Edge Reinforced Support for Enhanced Thermal Mechanical Stability.

    PubMed

    Baek, Jong Dae; Yu, Chen-Chiang; Su, Pei-Chen

    2016-04-13

    A silicon-based micro-solid oxide fuel cell (μ-SOFC) with electrolyte membrane array embedded in a thin silicon supporting membrane, featuring a unique edge reinforcement structure, was demonstrated by utilizing simple silicon micromachining processes. The square silicon supporting membrane, fabricated by combining deep reactive ion etching and through-wafer wet etching processes, has thicker edges and corners than the center portion of the membrane, which effectively improved the mechanical stability of the entire fuel cell array during cell fabrication and cell operation. The 20 μm thick single crystalline silicon membrane supports a large number of 80 nm thick free-standing yttria-stabilized zirconia (YSZ) electrolytes. The fuel cell array was stably maintained at the open circuit voltage (OCV) of 1.04 V for more than 30 h of operation at 350 °C. A high peak power density of 317 mW/cm(2) was obtained at 400 °C. During a rigorous in situ thermal cycling between 150 and 400 °C at a fast cooling and heating rate of 25 °C/min, the OCV of the μ-SOFC recovered to its high value of 1.07 V without any drop caused by membrane failure, which justifies the superior thermal stability of this novel cell architecture.

  3. Large-area monocrystalline silicon thin films by annealing of macroporous arrays: Understanding and tackling defects in the material

    NASA Astrophysics Data System (ADS)

    Depauw, Valérie; Gordon, Ivan; Beaucarne, Guy; Poortmans, Jef; Mertens, Robert; Celis, Jean-Pierre

    2009-08-01

    A concept that could provide a thin monocrystalline-silicon absorber layer without resorting to the expensive step of epitaxy would be very appealing for reducing the cost of solar cells. The empty-space-in-silicon technique by which thin films of silicon can be formed by reorganization of regular arrays of cylindrical voids at high temperature may be such a concept if the high quality of the thin film could be ensured on centimeter-large areas. While previous works mainly investigated the influence of the porous array on the final structure, this work focuses on the practical aspects of the high-temperature step and its application to large areas. An insight into the defects that may form is given and the origin of these defects is discussed, providing recommendations on how to avoid them. Surface roughening, pitting, formation of holes, and silicon pillars could be attributed to the nonuniform reactions between Si, SiO2, and SiO. Hydrogen atmospheres are therefore preferred for reorganization of macroporous arrays. Argon atmospheres, however, may provide high-quality silicon thin films as well, possibly even more easily transferable, as long as annealing is performed in controlled, clean, and oxygen-free conditions. Our experiments on large areas also highlight the importance of kinetics, which had not been considered up to now and which will require further understanding to ensure a complete reorganization over any wafer area.

  4. Development of silicon monolithic arrays for dosimetry in external beam radiotherapy

    NASA Astrophysics Data System (ADS)

    Bisello, Francesca; Menichelli, David; Scaringella, Monica; Talamonti, Cinzia; Zani, Margherita; Bucciolini, Marta; Bruzzi, Mara

    2015-10-01

    New tools for dosimetry in external beam radiotherapy have been developed during last years in the framework of the collaboration among the University of Florence, INFN Florence and IBA Dosimetry. The first step (in 2007) was the introduction in dosimetry of detector solutions adopted from high energy physics, namely epitaxial silicon as the base detector material and a guard ring in diode design. This allowed obtaining state of the art radiation hardness, in terms of sensitivity dependence on accumulated dose, with sensor geometry particularly suitable for the production of monolithic arrays with modular design. Following this study, a 2D monolithic array has been developed, based on 6.3×6.3 cm2 modules with 3 mm pixel pitch. This prototype has been widely investigated and turned out to be a promising tool to measure dose distributions of small and IMRT fields. A further linear array prototype has been recently design with improve spatial resolution (1 mm pitch) and radiation hardness. This 24 cm long device is constituted by 4×64 mm long modules. It features low sensitivity changes with dose (0.2%/kGy) and dose per pulse (±1% in the range 0.1-2.3 mGy/pulse, covering applications with flattened and unflattened photon fields). The detector has been tested with very satisfactory results as a tool for quality assurance of linear accelerators, with special regards to small fields, and proton pencil beams. In this contribution, the characterization of the linear array with unflattened MV X-rays, 60Co radiation and 226 MeV protons is reported.

  5. Slicing of silicon into sheet material. Silicon sheet growth development for the large area silicon sheet task of the low cost silicon solar array project

    NASA Technical Reports Server (NTRS)

    Holden, S. C.; Fleming, J. R.

    1978-01-01

    Fabrication of a prototype large capacity multiple blade slurry saw is considered. Design of the bladehead which will tension up to 1000 blades, and cut a 45 cm long silicon ingot as large as 12 cm in diameter is given. The large blade tensioning force of 270,000 kg is applied through two bolts acting on a pair of scissor toggles, significantly reducing operator set-up time. Tests with an upside-down cutting technique resulted in 100% wafering yields and the highest wafer accuracy yet experienced with MS slicing. Variations in oil and abrasives resulted only in degraded slicing results. A technique of continuous abrasive slurry separation to remove silicon debris is described.

  6. Two-dimensional optical phased array antenna on silicon-on-insulator.

    PubMed

    Van Acoleyen, Karel; Rogier, Hendrik; Baets, Roel

    2010-06-21

    Optical wireless links can offer a very large bandwidth and can act as a complementary technology to radiofrequency links. Optical components nowadays are however rather bulky. Therefore, we have investigated the potential of silicon photonics to fabricated integrated components for wireless optical communication. This paper presents a two-dimensional phased array antenna consisting of grating couplers that couple light off-chip. Wavelength steering of $0.24 degrees /nm is presented reducing the need of active phase modulators. The needed steering range is $1.5 degrees . The 3dB angular coverage range of these antennas is about $0.007pi sr with a directivity of more than 38dBi and antenna losses smaller than 3dB.

  7. Extraordinary transmission through gain-assisted silicon-based nanohole arrays in telecommunication regimes.

    PubMed

    Bavil, Mehdi Afshari; Deng, Qingzhong; Zhou, Zhiping

    2014-08-01

    Extraordinary gain-assisted transmission in telecommunication regimes through circular nanohole arrays drilled on a metallic film is investigated theoretically. Silicon-compatible Er-Yb silicate, which has a photoluminescence peak in the telecommunication regime, was selected for optical amplification purposes. Geometrical parameters were optimized analytically in order to present transmission resonances at telecommunication regions. The required gain value for lossless propagation was determined by considering the surface-plasmon dispersion relation. Simulation results show that the predicted gain for lossless propagation cannot completely compensate the loss. By increasing gain value, absorption becomes zero and transmission approaches unit through a laser with a pumping power of 372 mW at 1480 nm.

  8. Self-organized 2D periodic arrays of nanostructures in silicon by nanosecond laser irradiation.

    PubMed

    Nayak, Barada K; Sun, Keye; Rothenbach, Christian; Gupta, Mool C

    2011-06-01

    We report a phenomenon of spontaneous formation of self-organized 2D periodic arrays of nanostructures (protrusions) by directly exposing a silicon surface to multiple nanosecond laser pulses. These self-organized 2D periodic nanostructures are produced toward the edge as an annular region around the circular laser spot. The heights of these nanostructures are around 500 nm with tip diameter ~100 nm. The period of the nanostructures is about 1064 nm, the wavelength of the incident radiation. In the central region of the laser spot, nanostructures are destroyed because of the higher laser intensity (due to the Gaussian shape of the laser beam) and accumulation of large number of laser pulses. Optical diffraction from these nanostructures indicates a threefold symmetry, which is in accordance with the observed morphological symmetries of these nanostructures.

  9. Spin-on-doping for output power improvement of silicon nanowire array based thermoelectric power generators

    SciTech Connect

    Xu, B. Fobelets, K.

    2014-06-07

    The output power of a silicon nanowire array (NWA)-bulk thermoelectric power generator (TEG) with Cu contacts is improved by spin-on-doping (SOD). The Si NWAs used in this work are fabricated via metal assisted chemical etching (MACE) of 0.01–0.02 Ω cm resistivity n- and p-type bulk, converting ~4% of the bulk thickness into NWs. The MACE process is adapted to ensure crystalline NWs. Current-voltage and Seebeck voltage-temperature measurements show that while SOD mainly influences the contact resistance in bulk, it influences both contact resistance and power factor in NWA-bulk based TEGs. According to our experiments, using Si NWAs in combination with SOD increases the output power by an order of 3 under the same heating power due to an increased power factor, decreased thermal conductivity of the NWA and reduced Si-Cu contact resistance.

  10. An Improved Manufacturing Approach for Discrete Silicon Microneedle Arrays with Tunable Height-Pitch Ratio

    PubMed Central

    Wang, Renxin; Wang, Wei; Li, Zhihong

    2016-01-01

    Silicon microneedle arrays (MNAs) have been widely studied due to their potential in various transdermal applications. However, discrete MNAs, as a preferred choice to fabricate flexible penetrating devices that could adapt curved and elastic tissue, are rarely reported. Furthermore, the reported discrete MNAs have disadvantages lying in uniformity and height-pitch ratio. Therefore, an improved technique is developed to manufacture discrete MNA with tunable height-pitch ratio, which involves KOH-dicing-KOH process. The detailed process is sketched and simulated to illustrate the formation of microneedles. Furthermore, the undercutting of convex mask in two KOH etching steps are mathematically analyzed, in order to reveal the relationship between etching depth and mask dimension. Subsequently, fabrication results demonstrate KOH-dicing-KOH process. {321} facet is figured out as the surface of octagonal pyramid microneedle. MNAs with diverse height and pitch are also presented to identify the versatility of this approach. At last, the metallization is realized via successive electroplating. PMID:27735837

  11. An Improved Manufacturing Approach for Discrete Silicon Microneedle Arrays with Tunable Height-Pitch Ratio.

    PubMed

    Wang, Renxin; Wang, Wei; Li, Zhihong

    2016-10-09

    Silicon microneedle arrays (MNAs) have been widely studied due to their potential in various transdermal applications. However, discrete MNAs, as a preferred choice to fabricate flexible penetrating devices that could adapt curved and elastic tissue, are rarely reported. Furthermore, the reported discrete MNAs have disadvantages lying in uniformity and height-pitch ratio. Therefore, an improved technique is developed to manufacture discrete MNA with tunable height-pitch ratio, which involves KOH-dicing-KOH process. The detailed process is sketched and simulated to illustrate the formation of microneedles. Furthermore, the undercutting of convex mask in two KOH etching steps are mathematically analyzed, in order to reveal the relationship between etching depth and mask dimension. Subsequently, fabrication results demonstrate KOH-dicing-KOH process. {321} facet is figured out as the surface of octagonal pyramid microneedle. MNAs with diverse height and pitch are also presented to identify the versatility of this approach. At last, the metallization is realized via successive electroplating.

  12. Electron emission properties of gated silicon field emitter arrays driven by laser pulses

    NASA Astrophysics Data System (ADS)

    Shimawaki, Hidetaka; Nagao, Masayoshi; Neo, Yoichiro; Mimura, Hidenori; Wakaya, Fujio; Takai, Mikio

    2016-10-01

    We report optically modulated electron emission from gated p-type silicon field emitter arrays (Si-FEAs). The device's "volcano" structure is designed to control the photoexcitation of electrons by transmitting light through the small gate aperture, thereby minimizing the photogeneration of slow diffusion carriers outside the depletion region in the tip. Compared to that in the dark, the emission current was enhanced by more than three orders of magnitude in the high field region when irradiated with blue laser pulses. Results from the time-resolved measurements of photoassisted electron emission showed that these possess the same response as the laser pulse with no discernible delay. These results indicate that the volcano device structure is effective at eliminating the generation of diffusion carriers and that a fully optimized FEA is promising as a photocathode for producing high-speed modulated electron beams.

  13. Catalase-like and peroxidase-like catalytic activities of silicon nanowire arrays.

    PubMed

    Wang, Hongwei; Jiang, Wenwen; Wang, Yanwei; Liu, Xiaoli; Yao, Jianlin; Yuan, Lin; Wu, Zhaoqiang; Li, Dan; Song, Bo; Chen, Hong

    2013-01-08

    Silicon nanowire arrays (SiNWAs) were found to have catalytic activities similar to those of biological enzymes catalase and peroxidase. Thus not only can these materials catalyze the decomposition reaction of H(2)O(2) into water and oxygen, but they can also catalyze the oxidation of o-phenylenediamine (OPD), a common substrate for peroxidases, by H(2)O(2). The presence of Si-H bonds and the morphology of the SiNWAs are found to be crucial to the occurrence of such catalytic activity. When the SiNWAs are reacted with H(2)O(2), the data from Raman spectroscopy suggests the formation of (Si-H)(2)···(O species) ((Si-H)(2)···Os), which is presumably responsible for the catalytic activity. These findings suggest the potential use of SiNWAs as enzyme mimics in medicine, biotechnology, and environmental chemistry.

  14. Sensitive and Selective Detection of HIV-1 RRE RNA Using Vertical Silicon Nanowire Electrode Array

    NASA Astrophysics Data System (ADS)

    Lee, Jaehyung; Hong, Min-Ho; Han, Sanghun; Na, Jukwan; Kim, Ilsoo; Kwon, Yong-Joon; Lim, Yong-beom; Choi, Heon-Jin

    2016-07-01

    In this study, HIV-1 Rev response element (RRE) RNA was detected via an Au-coated vertical silicon nanowire electrode array (VSNEA). The VSNEA was fabricated by combining bottom-up and top-down approaches and then immobilized by artificial peptides for the recognition of HIV-1 RRE. Differential pulse voltammetry (DPV) analysis was used to measure the electrochemical response of the peptide-immobilized VSNEA to the concentration and types of HIV-1 RRE RNA. DPV peaks showed linearity to the concentration of RNA with a detection limit down to 1.513 fM. It also showed the clear different peaks to the mutated HIV-1 RRE RNA. The high sensitivity and selectivity of VSNEA for the detection of HIV-1 RRE RNA may be attributed to the high surface-to-volume ratio and total overlap diffusion mode of ions of the one-dimensional nanowire electrodes.

  15. Self-referenced silicon nitride array microring biosensor for toxin detection using glycans at visible wavelength

    NASA Astrophysics Data System (ADS)

    Ghasemi, Farshid; Eftekhar, Ali A.; Gottfried, David S.; Song, Xuezheng; Cummings, Richard D.; Adibi, Ali

    2013-02-01

    We report on application of on-chip referencing to improve the limit-of-detection (LOD) in compact silicon nitride (SiN) microring arrays. Microring resonators, fabricated by e-beam lithography and fluorine-based etching, are designed for visible wavelengths (656nm) and have a footprint of 20 x 20 μm. GM1 ganglioside is used as the specific ligand for recognition of Cholera Toxin Subunit B (CTB), with Ricinus Communis Agglutinin I (RCA I) as a negative control. Using micro-cantilever based printing less than 10 pL of glycan solution is consumed per microring. Real-time data on analyte binding is extracted from the shifts in resonance wavelengths of the microrings.

  16. Silicon Photomultipliers and front-end electronics performance for Cherenkov Telescope Array camera development

    NASA Astrophysics Data System (ADS)

    Ambrosi, G.; Bissaldi, E.; Giglietto, N.; Giordano, F.; Ionica, M.; Paoletti, R.; Rando, R.; Simone, D.; Vagelli, V.

    2017-02-01

    In the last few years a number of efforts have been undertaken to develop new technology related to Silicon Photomultipliers (SiPMs). These photosensors consist of an array of identical Avalanche Photodiodes operating in Geiger mode and connected in parallel to a single output. The Italian Institute of Nuclear Physics (INFN) is involved in the R&D program Progetto Premiale Telescopi CHErenkov made in Italy (TECHE.it) to develop photosensors for a SiPM based camera that will be part of the Cherenkov Telescope Array (CTA) observatory. In this framework tests are ongoing on innovative devices suitable to detect Cherenkov light in the blue and near-UV wavelength region, the so-called Near Ultra-Violet Silicon Photomultipliers (NUV SiPMs). The tests on photosensors produced by Fondazione Bruno Kessler (FBK) are revealing promising performance: low operating voltage, capability to detect very low intensity light down to a single photon and high Photo Detection Efficiency (PDE) in the range 390-410 nm. In particular the developed device is a High Density NUV-SiPM (NUV-HD SiPM) based on a micro-cell of 30 μm×30 μm and 6 mm×6 mm area. Tests on this detector in single-cell configuration and in a matrix arrangement have been done. At the same time front-end electronics based on the waveform sampling technique optimized for the new NUV-HD SIPMs is under study and development.

  17. Using Microelectrode Arrays for Neurotoxicity Screening

    EPA Science Inventory

    Chemicals can disrupt nervous system electrical activity, rapidly causing toxicity prior to, or in the absence of, biochemical or morphological changes. However, high-throughput, functional approaches to detect chemical induced changes in electrical excitability are lacking. Micr...

  18. An investigation into the fabrication and combustion performance of porous silicon nanoenergetic array chips.

    PubMed

    Wang, Shouxu; Shen, Ruiqi; Ye, Yinghua; Hu, Yan

    2012-11-02

    An investigation into the ignitions and combustions of porous silicon (PS) nanoenergetic material array chips (nECs) at different ignition voltages was performed. The PS nECs were fabricated by integrating PS nanoenergetic material (nEMs) matrices and Cr-microbridges (microigniters) on the surface of silicon substrates. The combustion of PS nECs was in ambient air. Its ignition and combustion were investigated by a testing system and an optical high-speed camera. Experimental results revealed that the combustion delay time of PS nEMs increased from 8.0 × 10(-5) s to 1.1 × 10(-4) s with the decrement of ignition voltages from 140 to 80 V. The scope of ignition energy ranged from 0.153 to 0.287 mJ by calculations. The reaction type was deflagration, from the analysis of the high-speed video of PS nECs. The comprehensive experimental results indicated that the combustion of PS nECs was ignited by the synergic effect of the heat and the plasma. The ignition experiments suggested that Cr-microbridges were reliable igniters to trigger the self-sustained combustion of PS nECs. The strong plume of flame emitted from the surface of PS nECs indicated that the PS nECs may be applied as micro/nano igniter chips and microthruster chips.

  19. Synthesis, characterization and application of electroless metal assisted silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Sahoo, Sumanta Kumar; Marikani, Arumugam

    2015-12-01

    Vertically aligned silicon nanowire arrays (SiNWs) have been synthesized by electroless metal deposition process. The fabricated SiNWs have an average diameter of 75 nm and 3.5-4.0 μm length, as confirmed from scanning electron microscopy. A characteristic asymmetric peak broadening at 520 cm-1 from Raman spectroscopy was obtained for the SiNWs as compared to the bulk silicon crystal due to phonon confinement. The as-prepared SiNWs exhibit good electron field-emission properties with turn-on field of about 8.26 V μm-1 at a current density of 4.9 μA cm-2. The SiNWs was functionalized by coating with a thin gold metallic film for 60 s, and then used as bio-probe for the detection of bovine serum albumin (BSA) protein molecules. From the linear sweep voltammetry analysis, the Au coated SiNWs, exhibit linear response to the BSA analyte with increase in concentration. The minimum detection limit of the protein molecule was calculated of about 1.16 μM by the as-synthesized SiNWs probe.

  20. Fluoroscopic x-ray imaging with amorphous silicon thin-film arrays

    NASA Astrophysics Data System (ADS)

    Schiebel, Ulrich W.; Conrads, Norbert; Jung, Norbert; Weibrecht, Martin; Wieczorek, Herfried K.; Zaengel, Thomas T.; Powell, M. J.; French, I. D.; Glasse, C.

    1994-05-01

    The dream of an all-solid state large area x-ray image sensor with digital readout and full dynamic performance will most probably find a first realization in 2D thin-film amorphous silicon arrays. In this paper we address in particular the evaluation of the limits of the signal/noise ratio in this concept. Using small prototype detectors measurements of MTF and noise power spectra have been made as a function of x-ray dose. The results are given in terms of the detective quantum efficiency as a function of dose and spatial frequency. We further present an analysis of the different noise sources and their dependence on the detector parameters, and we provide estimates on the maximum signals that may be achieved per unit dose. The intrinsic lag of the amorphous silicon photodiodes causes a second problem area with this type of x-ray detectors. Especially in radiography/fluoroscopy mixed applications, memory effects may not be negligible.

  1. In vivo optical modulation of neural signals using monolithically integrated two-dimensional neural probe arrays

    NASA Astrophysics Data System (ADS)

    Son, Yoojin; Jenny Lee, Hyunjoo; Kim, Jeongyeon; Shin, Hyogeun; Choi, Nakwon; Justin Lee, C.; Yoon, Eui-Sung; Yoon, Euisik; Wise, Kensall D.; Geun Kim, Tae; Cho, Il-Joo

    2015-10-01

    Integration of stimulation modalities (e.g. electrical, optical, and chemical) on a large array of neural probes can enable an investigation of important underlying mechanisms of brain disorders that is not possible through neural recordings alone. Furthermore, it is important to achieve this integration of multiple functionalities in a compact structure to utilize a large number of the mouse models. Here we present a successful optical modulation of in vivo neural signals of a transgenic mouse through our compact 2D MEMS neural array (optrodes). Using a novel fabrication method that embeds a lower cladding layer in a silicon substrate, we achieved a thin silicon 2D optrode array that is capable of delivering light to multiple sites using SU-8 as a waveguide core. Without additional modification to the microelectrodes, the measured impedance of the multiple microelectrodes was below 1 MΩ at 1 kHz. In addition, with a low background noise level (±25 μV), neural spikes from different individual neurons were recorded on each microelectrode. Lastly, we successfully used our optrodes to modulate the neural activity of a transgenic mouse through optical stimulation. These results demonstrate the functionality of the 2D optrode array and its potential as a next-generation tool for optogenetic applications.

  2. In vivo optical modulation of neural signals using monolithically integrated two-dimensional neural probe arrays

    PubMed Central

    Son, Yoojin; Jenny Lee, Hyunjoo; Kim, Jeongyeon; Shin, Hyogeun; Choi, Nakwon; Justin Lee, C.; Yoon, Eui-Sung; Yoon, Euisik; Wise, Kensall D.; Geun Kim, Tae; Cho, Il-Joo

    2015-01-01

    Integration of stimulation modalities (e.g. electrical, optical, and chemical) on a large array of neural probes can enable an investigation of important underlying mechanisms of brain disorders that is not possible through neural recordings alone. Furthermore, it is important to achieve this integration of multiple functionalities in a compact structure to utilize a large number of the mouse models. Here we present a successful optical modulation of in vivo neural signals of a transgenic mouse through our compact 2D MEMS neural array (optrodes). Using a novel fabrication method that embeds a lower cladding layer in a silicon substrate, we achieved a thin silicon 2D optrode array that is capable of delivering light to multiple sites using SU-8 as a waveguide core. Without additional modification to the microelectrodes, the measured impedance of the multiple microelectrodes was below 1 MΩ at 1 kHz. In addition, with a low background noise level (±25 μV), neural spikes from different individual neurons were recorded on each microelectrode. Lastly, we successfully used our optrodes to modulate the neural activity of a transgenic mouse through optical stimulation. These results demonstrate the functionality of the 2D optrode array and its potential as a next-generation tool for optogenetic applications. PMID:26494437

  3. Label-free silicon photonic biosensor system with integrated detector array.

    PubMed

    Yan, Rongjin; Mestas, Santano P; Yuan, Guangwei; Safaisini, Rashid; Dandy, David S; Lear, Kevin L

    2009-08-07

    An integrated, inexpensive, label-free photonic waveguide biosensor system with multi-analyte capability has been implemented on a silicon photonics integrated circuit from a commercial CMOS line and tested with nanofilms. The local evanescent array coupled (LEAC) biosensor is based on a new physical phenomenon that is fundamentally different from the mechanisms of other evanescent field sensors. Increased local refractive index at the waveguide's upper surface due to the formation of a biological nanofilm causes local modulation of the evanescent field coupled into an array of photodetectors buried under the waveguide. The planar optical waveguide biosensor system exhibits sensitivity of 20%/nm photocurrent modulation in response to adsorbed bovine serum albumin (BSA) layers less than 3 nm thick. In addition to response to BSA, an experiment with patterned photoresist as well as beam propagation method simulations support the evanescent field shift principle. The sensing mechanism enables the integration of all optical and electronic components for a multi-analyte biosensor system on a chip.

  4. Defect level characterization of silicon nanowire arrays: Towards novel experimental paradigms

    SciTech Connect

    Carapezzi, Stefania; Castaldini, Antonio; Cavallini, Anna

    2014-02-21

    The huge amount of knowledge, and infrastructures, brought by silicon (Si) technology, make Si Nanowires (NWs) an ideal choice for nano-electronic Si-based devices. This, in turn, challenges the scientific research to adapt the technical and theoretical paradigms, at the base of established experimental techniques, in order to probe the properties of these systems. Metal-assisted wet-Chemical Etching (MaCE) [1, 2] is a promising fast, easy and cheap method to grow high aspect-ratio aligned Si NWs. Further, contrary to other fabrication methods, this method avoids the possible detrimental effects related to Au diffusion into NWs. We investigated the bandgap level diagram of MaCE Si NW arrays, phosphorous-doped, by means of Deep Level Transient Spectroscopy. The presence of both shallow and deep levels has been detected. The results have been examined in the light of the specificity of the MaCE growth. The study of the electronic levels in Si NWs is, of course, of capital importance in view of the integration of Si NW arrays as active layers in actual devices.

  5. Development of arrays of Silicon Drift Detectors and readout ASIC for the SIDDHARTA experiment

    NASA Astrophysics Data System (ADS)

    Quaglia, R.; Schembari, F.; Bellotti, G.; Butt, A. D.; Fiorini, C.; Bombelli, L.; Giacomini, G.; Ficorella, F.; Piemonte, C.; Zorzi, N.

    2016-07-01

    This work deals with the development of new Silicon Drift Detectors (SDDs) and readout electronics for the upgrade of the SIDDHARTA experiment. The detector is based on a SDDs array organized in a 4×2 format with each SDD square shaped with 64 mm2 (8×8) active area. The total active area of the array is therefore 32×16 mm2 while the total area of the detector (including 1 mm border dead area) is 34 × 18mm2. The SIDDHARTA apparatus requires 48 of these modules that are designed and manufactured by Fondazione Bruno Kessler (FBK). The readout electronics is composed by CMOS preamplifiers (CUBEs) and by the new SFERA (SDDs Front-End Readout ASIC) circuit. SFERA is a 16-channels readout ASIC designed in a 0.35 μm CMOS technology, which features in each single readout channel a high order shaping amplifier (9th order Semi-Gaussian complex-conjugate poles) and a high efficiency pile-up rejection logic. The outputs of the channels are connected to an analog multiplexer for the external analog to digital conversion. An on-chip 12-bit SAR ADC is also included. Preliminary measurements of the detectors in the single SDD format are reported. Also measurements of low X-ray energies are reported in order to prove the possible extension to the soft X-ray range.

  6. Bacteria detection based on its blockage effect on silicon nanopore array.

    PubMed

    Tang, Yanyan; Li, Zhen; Luo, Qiaohui; Liu, Jingqing; Wu, Jianmin

    2016-05-15

    Bacteria detection plays an important role in the guarantee of food and water safety. This work proposed a new sensing strategy for the rapid detection of bacteria based on its blockage effect on nanopore array, which was prepared from electrochemically etched silicon. With the assistance of microfluidic technology, the nanopore array attached with Escherichia coli antibody can selectively and rapidly capture E. coli bacteria, resulting in the decrease of pore accessibility. The signal of pore blockage can be measured by in-direct Fourier Transformed Reflectometric Interference Spectroscopy (FT-RIS). The pore blockage signal has a linear relationship with the logarithm of bacterial density in aqueous sample within the range from 10(3) to 10(7)cfuml(-1). Due to the specific interaction between the antibody and target bacteria, only the E. coli sample displayed significant pore blockage effect, whereas the non-target bacteria, Nox and P17, almost did not show any pore blockage effect. The strategy established in this work might be pervasively applied in the rapid detection of target bacteria and cell in a label-free manner.

  7. The Indiana silicon sphere 4 π charged-particle detector array

    NASA Astrophysics Data System (ADS)

    Kwiatkowski, K.; Bracken, D. S.; Morley, K. B.; Brzychczyk, J.; Foxford, E. Renshaw; Komisarcik, K.; Viola, V. E.; Yoder, N. R.; Dorsett, J.; Poehlman, J.; Madden, N.; Ottarson, J.

    1995-02-01

    A low threshold charged particle detector array for the study of fragmentation processes in light-ion-induced reactions has been constructed and successfully implemented at the IUCF and Saturne II accelerators. The array consists of 162-triple-element detector telescopes mounted in a spherical geometry and covering 74% of 4π in solid angle. Telescope elements are composed of (1) an axial-field gas ionization chamber operated with C3F8 gas; (2) a 0.5 mm thick passivated silicon detector, and (3) a 2.8 cm thick CsI(TI) scintillation crystal with photodiode readout. Discrete element identification is obtained for ejectiles up to Z ~ 16 over the dynamic range 0.7 <= E/A <= 95 MeV/nucleon. Isotopes are also distinguished for H, He, Li and Be ejectiles with 8 <~ E/A <~ 95 MeV. Custom-designed electronics are employed for bias supplies and linear signal processing. Data are acquired via a CAMAC/VME/Ethernet system.

  8. Implementing Silicon Nanoribbon Field-Effect Transistors as Arrays for Multiple Ion Detection.

    PubMed

    Stoop, Ralph L; Wipf, Mathias; Müller, Steffen; Bedner, Kristine; Wright, Iain A; Martin, Colin J; Constable, Edwin C; Fanget, Axel; Schönenberger, Christian; Calame, Michel

    2016-05-06

    Ionic gradients play a crucial role in the physiology of the human body, ranging from metabolism in cells to muscle contractions or brain activities. To monitor these ions, inexpensive, label-free chemical sensing devices are needed. Field-effect transistors (FETs) based on silicon (Si) nanowires or nanoribbons (NRs) have a great potential as future biochemical sensors as they allow for the integration in microscopic devices at low production costs. Integrating NRs in dense arrays on a single chip expands the field of applications to implantable electrodes or multifunctional chemical sensing platforms. Ideally, such a platform is capable of detecting numerous species in a complex analyte. Here, we demonstrate the basis for simultaneous sodium and fluoride ion detection with a single sensor chip consisting of arrays of gold-coated SiNR FETs. A microfluidic system with individual channels allows modifying the NR surfaces with self-assembled monolayers of two types of ion receptors sensitive to sodium and fluoride ions. The functionalization procedure results in a differential setup having active fluoride- and sodium-sensitive NRs together with bare gold control NRs on the same chip. Comparing functionalized NRs with control NRs allows the compensation of non-specific contributions from changes in the background electrolyte concentration and reveals the response to the targeted species.

  9. Evaluation of Matrix9 silicon photomultiplier array for small-animal PET

    SciTech Connect

    Du, Junwei Schmall, Jeffrey P.; Yang, Yongfeng; Di, Kun; Roncali, Emilie; Mitchell, Gregory S.; Buckley, Steve; Jackson, Carl; Cherry, Simon R.

    2015-02-15

    Purpose: The MatrixSL-9-30035-OEM (Matrix9) from SensL is a large-area silicon photomultiplier (SiPM) photodetector module consisting of a 3 × 3 array of 4 × 4 element SiPM arrays (total of 144 SiPM pixels) and incorporates SensL’s front-end electronics board and coincidence board. Each SiPM pixel measures 3.16 × 3.16 mm{sup 2} and the total size of the detector head is 47.8 × 46.3 mm{sup 2}. Using 8 × 8 polished LSO/LYSO arrays (pitch 1.5 mm) the performance of this detector system (SiPM array and readout electronics) was evaluated with a view for its eventual use in small-animal positron emission tomography (PET). Methods: Measurements of noise, signal, signal-to-noise ratio, energy resolution, flood histogram quality, timing resolution, and array trigger error were obtained at different bias voltages (28.0–32.5 V in 0.5 V intervals) and at different temperatures (5 °C–25 °C in 5 °C degree steps) to find the optimal operating conditions. Results: The best measured signal-to-noise ratio and flood histogram quality for 511 keV gamma photons were obtained at a bias voltage of 30.0 V and a temperature of 5 °C. The energy resolution and timing resolution under these conditions were 14.2% ± 0.1% and 4.2 ± 0.1 ns, respectively. The flood histograms show that all the crystals in the 1.5 mm pitch LSO array can be clearly identified and that smaller crystal pitches can also be resolved. Flood histogram quality was also calculated using different center of gravity based positioning algorithms. Improved and more robust results were achieved using the local 9 pixels for positioning along with an energy offset calibration. To evaluate the front-end detector readout, and multiplexing efficiency, an array trigger error metric is introduced and measured at different lower energy thresholds. Using a lower energy threshold greater than 150 keV effectively eliminates any mispositioning between SiPM arrays. Conclusions: In summary, the Matrix9 detector system

  10. Optimal and Local Connectivity Between Neuron and Synapse Array in the Quantum Dot/Silicon Brain

    NASA Technical Reports Server (NTRS)

    Duong, Tuan A.; Assad, Christopher; Thakoor, Anikumar P.

    2010-01-01

    This innovation is used to connect between synapse and neuron arrays using nanowire in quantum dot and metal in CMOS (complementary metal oxide semiconductor) technology to enable the density of a brain-like connection in hardware. The hardware implementation combines three technologies: 1. Quantum dot and nanowire-based compact synaptic cell (50x50 sq nm) with inherently low parasitic capacitance (hence, low dynamic power approx.l0(exp -11) watts/synapse), 2. Neuron and learning circuits implemented in 50-nm CMOS technology, to be integrated with quantum dot and nanowire synapse, and 3. 3D stacking approach to achieve the overall numbers of high density O(10(exp 12)) synapses and O(10(exp 8)) neurons in the overall system. In a 1-sq cm of quantum dot layer sitting on a 50-nm CMOS layer, innovators were able to pack a 10(exp 6)-neuron and 10(exp 10)-synapse array; however, the constraint for the connection scheme is that each neuron will receive a non-identical 10(exp 4)-synapse set, including itself, via its efficacy of the connection. This is not a fully connected system where the 100x100 synapse array only has a 100-input data bus and 100-output data bus. Due to the data bus sharing, it poses a great challenge to have a complete connected system, and its constraint within the quantum dot and silicon wafer layer. For an effective connection scheme, there are three conditions to be met: 1. Local connection. 2. The nanowire should be connected locally, not globally from which it helps to maximize the data flow by sharing the same wire space location. 3. Each synapse can have an alternate summation line if needed (this option is doable based on the simple mask creation). The 10(exp 3)x10(exp 3)-neuron array was partitioned into a 10-block, 10(exp 2)x10(exp 3)-neuron array. This building block can be completely mapped within itself (10,000 synapses to a neuron).

  11. Slicing of Silicon into Sheet Material: Silicon Sheet Growth Development for the Large Area Silicon Sheet Task of the Low Cost Silicon Solar Array Project

    NASA Technical Reports Server (NTRS)

    Fleming, J. R.

    1979-01-01

    Testing of low cost low suspension power slurry vehicles is presented. Cutting oils are unlikely to work, but a mineral oil with additives should be workable. Two different abrasives were tested. A cheaper silicon carbide from Norton gave excellent results except for excessive kerf loss: the particles were too big. An abrasive treated for lubricity showed no lubricity improvement in mineral oil vehicle. The bounce fixture was tested for the first time under constant cut rate conditions (rather than constant force). Although the cut was not completed before the blades broke, the blade lifetime of thin (100 micrometer) blades was 120 times the lifetime without the fixture. The large prototype saw completed a successful run, producing 90% cutting yield (849 wafers) at 20 wafers/cm. Although inexperience with large numbers of wafers caused cleaning breakage to reduce this yield to 74%, the yield was high enough that the concept of the large saw is proven workable.

  12. High-efficiency ordered silicon nano-conical-frustum array solar cells by self-powered parallel electron lithography.

    PubMed

    Lu, Yuerui; Lal, Amit

    2010-11-10

    Nanostructured silicon thin film solar cells are promising, due to the strongly enhanced light trapping, high carrier collection efficiency, and potential low cost. Ordered nanostructure arrays, with large-area controllable spacing, orientation, and size, are critical for reliable light-trapping and high-efficiency solar cells. Available top-down lithography approaches to fabricate large-area ordered nanostructure arrays are challenging due to the requirement of both high lithography resolution and high throughput. Here, a novel ordered silicon nano-conical-frustum array structure, exhibiting an impressive absorbance of 99% (upper bound) over wavelengths 400-1100 nm by a thickness of only 5 μm, is realized by our recently reported technique self-powered parallel electron lithography that has high-throughput and sub-35-nm high resolution. Moreover, high-efficiency (up to 10.8%) solar cells are demonstrated, using these ordered ultrathin silicon nano-conical-frustum arrays. These related fabrication techniques can also be transferred to low-cost substrate solar energy harvesting device applications.

  13. Delta-Doping at Wafer Level for High Throughput, High Yield Fabrication of Silicon Imaging Arrays

    NASA Technical Reports Server (NTRS)

    Hoenk, Michael E. (Inventor); Nikzad, Shoulch (Inventor); Jones, Todd J. (Inventor); Greer, Frank (Inventor); Carver, Alexander G. (Inventor)

    2014-01-01

    Systems and methods for producing high quantum efficiency silicon devices. A silicon MBE has a preparation chamber that provides for cleaning silicon surfaces using an oxygen plasma to remove impurities and a gaseous (dry) NH3 + NF3 room temperature oxide removal process that leaves the silicon surface hydrogen terminated. Silicon wafers up to 8 inches in diameter have devices that can be fabricated using the cleaning procedures and MBE processing, including delta doping.

  14. Inorganic/organic hybrid solar cells: optimal carrier transport in vertically aligned silicon nanowire arrays

    NASA Astrophysics Data System (ADS)

    Sato, Keisuke; Dutta, Mrinal; Fukata, Naoki

    2014-05-01

    Inorganic/organic hybrid radial heterojunction solar cells that combine vertically-aligned n-type silicon nanowires (SiNWs) with poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) have great potential for replacing commercial Si solar cells. The chief advantage of such solar cells is that they exhibit higher absorbance for a given thickness than commercial Si solar cells, due to incident light-trapping within the NW arrays, thus enabling lower-cost solar cell production. We report herein on the effects of NW length, annealing and surface electrode on the device performance of SiNW/PEDOT:PSS hybrid radial heterojunction solar cells. The power conversion efficiency (PCE) of the obtained SiNW/PEDOT:PSS hybrid solar cells can be optimized by tuning the thickness of the surface electrode, and the etching conditions during NW formation and post-annealing. The PCE of 9.3% is obtained by forming efficient transport pathways for photogenerated charge carriers to electrodes. Our approach is a significant contribution to design of high-performance and low-cost inorganic/organic hybrid heterojunction solar cells.Inorganic/organic hybrid radial heterojunction solar cells that combine vertically-aligned n-type silicon nanowires (SiNWs) with poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) have great potential for replacing commercial Si solar cells. The chief advantage of such solar cells is that they exhibit higher absorbance for a given thickness than commercial Si solar cells, due to incident light-trapping within the NW arrays, thus enabling lower-cost solar cell production. We report herein on the effects of NW length, annealing and surface electrode on the device performance of SiNW/PEDOT:PSS hybrid radial heterojunction solar cells. The power conversion efficiency (PCE) of the obtained SiNW/PEDOT:PSS hybrid solar cells can be optimized by tuning the thickness of the surface electrode, and the etching conditions during NW formation and

  15. Phase 2 of the array automated assembly task for the low cost silicon solar array project. Final report

    SciTech Connect

    Petersen, R.C.

    1980-11-01

    Studies were conducted on several fundamental aspects of electroless nickel/solder metallization for silicon solar cells. A process proposed by Motorola, which precedes the electroless nickel plating with several steps of palladium plating and heat treatment, was compared directly with single step electroless nickel plating. Work has directed toward answering specific questions concerning the effect of silicon surface oxide on nickel plating, effects of thermal stresses on the metallization, sintering of nickel plated on silicon, and effects of exposure to the plating solution on solar cell characteristics. The Motorola process was compared with simple electroless nickel plating in a series of parallel experiments. Results are presented. (WHK)

  16. Silicon materials task of the Low Cost Solar Array Project: Effect of impurities and processing on silicon solar cells

    NASA Technical Reports Server (NTRS)

    Hopkins, R. H.; Davis, J. R.; Rohatgi, A.; Hanes, M. H.; Rai-Choudhury, P.; Mollenkopf, H. C.

    1982-01-01

    The effects of impurities and processing on the characteristics of silicon and terrestrial silicon solar cells were defined in order to develop cost benefit relationships for the use of cheaper, less pure solar grades of silicon. The amount of concentrations of commonly encountered impurities that can be tolerated in typical p or n base solar cells was established, then a preliminary analytical model from which the cell performance could be projected depending on the kinds and amounts of contaminants in the silicon base material was developed. The impurity data base was expanded to include construction materials, and the impurity performace model was refined to account for additional effects such as base resistivity, grain boundary interactions, thermal processing, synergic behavior, and nonuniform impurity distributions. A preliminary assessment of long term (aging) behavior of impurities was also undertaken.

  17. Hot forming of silicon sheet, silicon sheet growth development for the large area silicon sheet task of the low cost silicon solar array project

    NASA Technical Reports Server (NTRS)

    Graham, C. D., Jr.; Pope, D. P.; Kulkarni, S.; Wolf, M.

    1978-01-01

    The hot workability of polycrystalline silicon was studied. Uniaxail stress-strain curves are given for strain rates in the range of .0001 to .1/sec and temperatures from 1100 to 1380 C. At the highest strain rates at 1380 C axial strains in excess of 20% were easily obtainable without cracking. After deformations of 36%, recrystallization was completed within 0.1 hr at 1380 C. When the recrystallization was complete, there was still a small volume fraction of unrecyrstallized material which appeared very stable and may degrade the electronic properties of the bulk materials. Texture measurements showed that the as-produced vapor deposited polycrystalline rods have a 110 fiber texture with the 110 direction parallel to the growth direction and no preferred orientation about this axis. Upon axial compression perpendicular to the growth direction, the former 110 fiber axis changed to 111 and the compression axis became 110 . Recrystallization changed the texture to 110 along the former fiber axis and to 100 along the compression axis.

  18. Numerically controlled atmospheric-pressure plasma sacrificial oxidation using electrode arrays for improving silicon-on-insulator layer uniformity

    NASA Astrophysics Data System (ADS)

    Takei, Hiroyasu; Yoshinaga, Keinosuke; Matsuyama, Satoshi; Yamauchi, Kazuto; Sano, Yasuhisa

    2015-01-01

    Silicon-on-insulator (SOI) wafers are important semiconductor substrates in high-performance devices. In accordance with device miniaturization requirements, ultrathin and highly uniform top silicon layers (SOI layers) are required. A novel method involving numerically controlled (NC) atmospheric-pressure plasma sacrificial oxidation using an electrode array system was developed for the effective fabrication of an ultrathin SOI layer with extremely high uniformity. Spatial resolution and oxidation properties are the key factors controlling ultraprecision machining. The controllability of plasma oxidation and the oxidation properties of the resulting experimental electrode array system were examined. The results demonstrated that the method improved the thickness uniformity of the SOI layer over one-sixth of the area of an 8-in. wafer area.

  19. The influence of passivation and photovoltaic properties of α-Si:H coverage on silicon nanowire array solar cells

    PubMed Central

    2013-01-01

    Silicon nanowire (SiNW) arrays for radial p-n junction solar cells offer potential advantages of light trapping effects and quick charge collection. Nevertheless, lower open circuit voltages (Voc) lead to lower energy conversion efficiencies. In such cases, the performance of the solar cells depends critically on the quality of the SiNW interfaces. In this study, SiNW core-shell solar cells have been fabricated by growing crystalline silicon (c-Si) nanowires via the metal-assisted chemical etching method and by depositing hydrogenated amorphous silicon (α-Si:H) via the plasma-enhanced chemical vapor deposition (PECVD) method. The influence of deposition parameters on the coverage and, consequently, the passivation and photovoltaic properties of α-Si:H layers on SiNW solar cells have been analyzed. PMID:24059343

  20. The influence of passivation and photovoltaic properties of α-Si:H coverage on silicon nanowire array solar cells.

    PubMed

    Li, Kuntang; Wang, Xiuqin; Lu, Pengfei; Ding, Jianning; Yuan, Ningyi

    2013-09-23

    Silicon nanowire (SiNW) arrays for radial p-n junction solar cells offer potential advantages of light trapping effects and quick charge collection. Nevertheless, lower open circuit voltages (Voc) lead to lower energy conversion efficiencies. In such cases, the performance of the solar cells depends critically on the quality of the SiNW interfaces. In this study, SiNW core-shell solar cells have been fabricated by growing crystalline silicon (c-Si) nanowires via the metal-assisted chemical etching method and by depositing hydrogenated amorphous silicon (α-Si:H) via the plasma-enhanced chemical vapor deposition (PECVD) method. The influence of deposition parameters on the coverage and, consequently, the passivation and photovoltaic properties of α-Si:H layers on SiNW solar cells have been analyzed.

  1. A high performance three-phase enzyme electrode based on superhydrophobic mesoporous silicon nanowire arrays for glucose detection.

    PubMed

    Xu, Chenlong; Song, Zhiqian; Xiang, Qun; Jin, Jian; Feng, Xinjian

    2016-04-14

    We describe here a high performance oxygen-rich three-phase enzyme electrode based on superhydrophobic mesoporous silicon nanowire arrays for glucose detection. We demonstrate that its linear detection upper limit is 30 mM, more than 15 times higher than that can be obtained on the normal enzyme-electrode. Notably, the three-phase enzyme electrode output is insensitive to the significant oxygen level fluctuation in analyte solution.

  2. Measurement and Simulation of the Variation in Proton-Induced Energy Deposition in Large Silicon Diode Arrays

    NASA Technical Reports Server (NTRS)

    Howe, Christina L.; Weller, Robert A.; Reed, Robert A.; Sierawski, Brian D.; Marshall, Paul W.; Marshall, Cheryl J.; Mendenhall, Marcus H.; Schrimpf, Ronald D.

    2007-01-01

    The proton induced charge deposition in a well characterized silicon P-i-N focal plane array is analyzed with Monte Carlo based simulations. These simulations include all physical processes, together with pile up, to accurately describe the experimental data. Simulation results reveal important high energy events not easily detected through experiment due to low statistics. The effects of each physical mechanism on the device response is shown for a single proton energy as well as a full proton space flux.

  3. Direct detection of transcription factors in cotyledons during seedling development using sensitive silicon-substrate photonic crystal protein arrays.

    PubMed

    Jones, Sarah I; Tan, Yafang; Shamimuzzaman, Md; George, Sherine; Cunningham, Brian T; Vodkin, Lila

    2015-03-01

    Transcription factors control important gene networks, altering the expression of a wide variety of genes, including those of agronomic importance, despite often being expressed at low levels. Detecting transcription factor proteins is difficult, because current high-throughput methods may not be sensitive enough. One-dimensional, silicon-substrate photonic crystal (PC) arrays provide an alternative substrate for printing multiplexed protein microarrays that have greater sensitivity through an increased signal-to-noise ratio of the fluorescent signal compared with performing the same assay upon a traditional aminosilanized glass surface. As a model system to test proof of concept of the silicon-substrate PC arrays to directly detect rare proteins in crude plant extracts, we selected representatives of four different transcription factor families (zinc finger GATA, basic helix-loop-helix, BTF3/NAC [for basic transcription factor of the NAC family], and YABBY) that have increasing transcript levels during the stages of seedling cotyledon development. Antibodies to synthetic peptides representing the transcription factors were printed on both glass slides and silicon-substrate PC slides along with antibodies to abundant cotyledon proteins, seed lectin, and Kunitz trypsin inhibitor. The silicon-substrate PC arrays proved more sensitive than those performed on glass slides, detecting rare proteins that were below background on the glass slides. The zinc finger transcription factor was detected on the PC arrays in crude extracts of all stages of the seedling cotyledons, whereas YABBY seemed to be at the lower limit of their sensitivity. Interestingly, the basic helix-loop-helix and NAC proteins showed developmental profiles consistent with their transcript patterns, indicating proof of concept for detecting these low-abundance proteins in crude extracts.

  4. Gain compensation technique by bias correction in arrays of Silicon Photomultipliers using fully differential fast shaper

    NASA Astrophysics Data System (ADS)

    Baszczyk, M.; Dorosz, P.; Glab, S.; Kucewicz, W.; Mik, L.; Sapor, M.

    2016-07-01

    Proposed algorithm compensates the gain by changing the bias voltage of Silicon Photomultipliers (SiPM). The signal from SiPM is amplified in fully differential preamplifier then is formed in time by the fully differential fast shaper. The compensation method was tested with four channels common cathode multi-pixel photon counter from Hamamatsu. The measurement system requires only one high voltage power supply. The polarization voltage is adjusted individually in each channel indirectly by tuning the output common mode voltage (VOCM) of fully differential amplifier. The changes of VOCM affect the input voltage through the feedback network. Actual gain of the SiPM is calculated by measuring the mean amplitude of the signal resulting from detection of single photoelectron. The VOCM is adjusted by DAC so as to reach the desired value of gain by each channel individually. The advantage of the algorithm is the possibility to set the bias of each SiPM in the array independently so they all could operate in very similar conditions (have similar gain and dark count rate). The algorithm can compensate the variations of gain of SiPM by using thermally generated pulses. There is no need to use additional current to voltage conversion which could introduce extra noises.

  5. Ultrathin Epitaxial Silicon Solar Cells with Inverted Nanopyramid Arrays for Efficient Light Trapping.

    PubMed

    Gaucher, Alexandre; Cattoni, Andrea; Dupuis, Christophe; Chen, Wanghua; Cariou, Romain; Foldyna, Martin; Lalouat, Loı̈c; Drouard, Emmanuel; Seassal, Christian; Roca I Cabarrocas, Pere; Collin, Stéphane

    2016-09-14

    Ultrathin c-Si solar cells have the potential to drastically reduce costs by saving raw material while maintaining good efficiencies thanks to the excellent quality of monocrystalline silicon. However, efficient light trapping strategies must be implemented to achieve high short-circuit currents. We report on the fabrication of both planar and patterned ultrathin c-Si solar cells on glass using low temperature (T < 275 °C), low-cost, and scalable techniques. Epitaxial c-Si layers are grown by PECVD at 160 °C and transferred on a glass substrate by anodic bonding and mechanical cleavage. A silver back mirror is combined with a front texturation based on an inverted nanopyramid array fabricated by nanoimprint lithography and wet etching. We demonstrate a short-circuit current density of 25.3 mA/cm(2) for an equivalent thickness of only 2.75 μm. External quantum efficiency (EQE) measurements are in very good agreement with FDTD simulations. We infer an optical path enhancement of 10 in the long wavelength range. A simple propagation model reveals that the low photon escape probability of 25% is the key factor in the light trapping mechanism. The main limitations of our current technology and the potential efficiencies achievable with contact optimization are discussed.

  6. Inorganic/organic hybrid solar cells: optimal carrier transport in vertically aligned silicon nanowire arrays.

    PubMed

    Sato, Keisuke; Dutta, Mrinal; Fukata, Naoki

    2014-06-07

    Inorganic/organic hybrid radial heterojunction solar cells that combine vertically-aligned n-type silicon nanowires (SiNWs) with poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) have great potential for replacing commercial Si solar cells. The chief advantage of such solar cells is that they exhibit higher absorbance for a given thickness than commercial Si solar cells, due to incident light-trapping within the NW arrays, thus enabling lower-cost solar cell production. We report herein on the effects of NW length, annealing and surface electrode on the device performance of SiNW/PEDOT:PSS hybrid radial heterojunction solar cells. The power conversion efficiency (PCE) of the obtained SiNW/PEDOT:PSS hybrid solar cells can be optimized by tuning the thickness of the surface electrode, and the etching conditions during NW formation and post-annealing. The PCE of 9.3% is obtained by forming efficient transport pathways for photogenerated charge carriers to electrodes. Our approach is a significant contribution to design of high-performance and low-cost inorganic/organic hybrid heterojunction solar cells.

  7. Angular domain spectroscopic imaging of turbid media using silicon micromachined microchannel arrays

    NASA Astrophysics Data System (ADS)

    Vasefi, Fartash; Ng, Eldon; Najiminaini, Mohamadreza; Albert, Genevieve; Kaminska, Bozena; Chapman, Glenn H.; Carson, Jeffrey J. L.

    2010-02-01

    We experimentally characterized a novel Angular Domain Spectroscopic Imaging (ADSI) technique for the detection and characterization of optical contrast abnormalities in turbid media. The new imaging system employs silicon micromachined angular filtering methodology, which has high angular selectivity for photons exiting the turbid medium. The angular filter method offers efficient scattered light suppression at moderate levels of scattering (i.e. up to 6 reduced mean free paths). An ADSI system was constructed from a broadband light source, an Angular Filter Array (AFA), and an imaging spectrometer. The free-space collimated broadband light source was used to trans-illuminate a turbid sample over a wide range of wavelengths in the near infrared region of the spectrum. The imaging spectrometer decomposed the output of the AFA into hyperspectral images representative of spatial location and wavelength. It collected and angularly filtered a line image from the object onto the CCD camera with the spatial information displayed along one axis and wavelength information along the other. The ADSI system performance was evaluated on tissue-mimicking phantoms as well as fresh chicken breast tissue. Collected images with the ADSI displayed differences in image contrast between different tissue types.

  8. Disordered array of Au covered Silicon nanowires for SERS biosensing combined with electrochemical detection

    NASA Astrophysics Data System (ADS)

    Convertino, Annalisa; Mussi, Valentina; Maiolo, Luca

    2016-04-01

    We report on highly disordered array of Au coated silicon nanowires (Au/SiNWs) as surface enhanced Raman scattering (SERS) probe combined with electrochemical detection for biosensing applications. SiNWs, few microns long, were grown by plasma enhanced chemical vapor deposition on common microscope slides and covered by Au evaporated film, 150 nm thick. The capability of the resulting composite structure to act as SERS biosensor was studied via the biotin-avidin interaction: the Raman signal obtained from this structure allowed to follow each surface modification step as well as to detect efficiently avidin molecules over a broad range of concentrations from micromolar down to the nanomolar values. The metallic coverage wrapping SiNWs was exploited also to obtain a dual detection of the same bioanalyte by electrochemical impedance spectroscopy (EIS). Indeed, the SERS signal and impedance modifications induced by the biomolecule perturbations on the metalized surface of the NWs were monitored on the very same three-electrode device with the Au/SiNWs acting as both working electrode and SERS probe.

  9. Magnetic field alignment of randomly oriented, high aspect ratio silicon microwires into vertically oriented arrays.

    PubMed

    Beardslee, Joseph A; Sadtler, Bryce; Lewis, Nathan S

    2012-11-27

    External magnetic fields have been used to vertically align ensembles of silicon microwires coated with ferromagnetic nickel films. X-ray diffraction and image analysis techniques were used to quantify the degree of vertical orientation of the microwires. The degree of vertical alignment and the minimum field strength required for alignment were evaluated as a function of the wire length, coating thickness, magnetic history, and substrate surface properties. Nearly 100% of 100 μm long, 2 μm diameter, Si microwires that had been coated with 300 nm of Ni could be vertically aligned by a 300 G magnetic field. For wires ranging from 40 to 60 μm in length, as the length of the wire increased, a higher degree of alignment was observed at lower field strengths, consistent with an increase in the available magnetic torque. Microwires that had been exposed to a magnetic sweep up to 300 G remained magnetized and, therefore, aligned more readily during subsequent magnetic field alignment sweeps. Alignment of the Ni-coated Si microwires occurred at lower field strengths on hydrophilic Si substrates than on hydrophobic Si substrates. The magnetic field alignment approach provides a pathway for the directed assembly of solution-grown semiconductor wires into vertical arrays, with potential applications in solar cells as well as in other electronic devices that utilize nano- and microscale components as active elements.

  10. Thermally responsive silicon nanowire arrays for native/denatured-protein separation.

    PubMed

    Wang, Hongwei; Wang, Yanwei; Yuan, Lin; Wang, Lei; Yang, Weikang; Wu, Zhaoqiang; Li, Dan; Chen, Hong

    2013-03-15

    We present our findings of the selective adsorption of native and denatured proteins onto thermally responsive, native-protein resistant poly(N-isopropylacrylamide) (PNIPAAm) decorated silicon nanowire arrays (SiNWAs). The PNIPAAm-SiNWAs surface, which shows very low levels of native-protein adsorption, favors the adsorption of denatured proteins. The amount of denatured-protein adsorption is higher at temperatures above the lower critical solution temperature (LCST) of PNIPAAm. Temperature cycling surrounding the LCST, which ensures against thermal denaturation of native proteins, further increases the amount of denatured-protein adsorption. Moreover, the PNIPAAm-SiNWAs surface is able to selectively adsorb denatured protein even from mixtures of different protein species; meanwhile, the amount of native proteins in solution is kept nearly at its original level. It is believed that these results will not only enrich current understanding of protein interactions with PNIPAAm-modified SiNWAs surfaces, but may also stimulate applications of PNIPAAm-SiNWAs surfaces for native/denatured protein separation.

  11. Disordered array of Au covered Silicon nanowires for SERS biosensing combined with electrochemical detection

    PubMed Central

    Convertino, Annalisa; Mussi, Valentina; Maiolo, Luca

    2016-01-01

    We report on highly disordered array of Au coated silicon nanowires (Au/SiNWs) as surface enhanced Raman scattering (SERS) probe combined with electrochemical detection for biosensing applications. SiNWs, few microns long, were grown by plasma enhanced chemical vapor deposition on common microscope slides and covered by Au evaporated film, 150 nm thick. The capability of the resulting composite structure to act as SERS biosensor was studied via the biotin-avidin interaction: the Raman signal obtained from this structure allowed to follow each surface modification step as well as to detect efficiently avidin molecules over a broad range of concentrations from micromolar down to the nanomolar values. The metallic coverage wrapping SiNWs was exploited also to obtain a dual detection of the same bioanalyte by electrochemical impedance spectroscopy (EIS). Indeed, the SERS signal and impedance modifications induced by the biomolecule perturbations on the metalized surface of the NWs were monitored on the very same three-electrode device with the Au/SiNWs acting as both working electrode and SERS probe. PMID:27112197

  12. Fabrication of microlens array on silicon surface using electrochemical wet stamping technique

    NASA Astrophysics Data System (ADS)

    Lai, Lei-Jie; Zhou, Hang; Zhu, Li-Min

    2016-02-01

    This paper focuses on the fabrication of microlens array (MLA) on silicon surface by taking advantage of a novel micromachining approach, the electrochemical we stamping (E-WETS). The E-WETS allows the direct imprinting of MLA on an agarose stamp into the substrate through a selective anodic dissolution process. The pre-patterned agarose stamp can direct and supply the solution preferentially on the contact area between the agarose stamp and the substrate, to which the electrochemical reaction is confined. The anodic potential vs. saturated calomel electrode is optimized and 1.5 V is chosen as the optimum value for the electrochemical polishing of p-Si. A refractive MLA on a PMMA mold is successfully transferred onto the p-Si surface. The machining deviations of the fabricated MLA from those on the mold are 0.44% in diameter and 2.1% in height respectively, and the machining rate in HF is around 1.1 μm/h. The surface roughness of the fabricated MLA is less than 12 nm owing to the electrochemical polishing process. The results demonstrate that E-WETS is a promising approach to fabricate MLA on p-Si surface with high accuracy and efficiency.

  13. X-ray imaging performance of scintillator-filled silicon pore arrays

    SciTech Connect

    Simon, Matthias; Engel, Klaus Juergen; Menser, Bernd; Badel, Xavier; Linnros, Jan

    2008-03-15

    The need for fine detail visibility in various applications such as dental imaging, mammography, but also neurology and cardiology, is the driver for intensive efforts in the development of new x-ray detectors. The spatial resolution of current scintillator layers is limited by optical diffusion. This limitation can be overcome by a pixelation, which prevents optical photons from crossing the interface between two neighboring pixels. In this work, an array of pores was etched in a silicon wafer with a pixel pitch of 50 {mu}m. A very high aspect ratio was achieved with wall thicknesses of 4-7 {mu}m and pore depths of about 400 {mu}m. Subsequently, the pores were filled with Tl-doped cesium iodide (CsI:Tl) as a scintillator in a special process, which includes powder melting and solidification of the CsI. From the sample geometry and x-ray absorption measurement the pore fill grade was determined to be 75%. The scintillator-filled samples have a circular active area of 16 mm diameter. They are coupled with an optical sensor binned to the same pixel pitch in order to measure the x-ray imaging performance. The x-ray sensitivity, i.e., the light output per absorbed x-ray dose, is found to be only 2.5%-4.5% of a commercial CsI-layer of similar thickness, thus very low. The efficiency of the pores to transport the generated light to the photodiode is estimated to be in the best case 6.5%. The modulation transfer function is 40% at 4 lp/mm and 10%-20% at 8 lp/mm. It is limited most likely by the optical gap between scintillator and sensor and by K-escape quanta. The detective quantum efficiency (DQE) is determined at different beam qualities and dose settings. The maximum DQE(0) is 0.28, while the x-ray absorption with the given thickness and fill factor is 0.57. High Swank noise is suspected to be the reason, mainly caused by optical scatter inside the CsI-filled pores. The results are compared to Monte Carlo simulations of the photon transport inside the pore array

  14. Optical properties of silicon nanowire arrays formed by metal-assisted chemical etching: evidences for light localization effect

    NASA Astrophysics Data System (ADS)

    Osminkina, Liubov A.; Gonchar, Kirill A.; Marshov, Vladimir S.; Bunkov, Konstantin V.; Petrov, Dmitry V.; Golovan, Leonid A.; Talkenberg, Florian; Sivakov, Vladimir A.; Timoshenko, Victor Yu

    2012-09-01

    We study the structure and optical properties of arrays of silicon nanowires (SiNWs) with a mean diameter of approximately 100 nm and length of about 1-25 μm formed on crystalline silicon (c-Si) substrates by using metal-assisted chemical etching in hydrofluoric acid solutions. In the middle infrared spectral region, the reflectance and transmittance of the formed SiNW arrays can be described in the framework of an effective medium with the effective refractive index of about 1.3 (porosity, approximately 75%), while a strong light scattering for wavelength of 0.3 ÷ 1 μm results in a decrease of the total reflectance of 1%-5%, which cannot be described in the effective medium approximation. The Raman scattering intensity under excitation at approximately 1 μm increases strongly in the sample with SiNWs in comparison with that in c-Si substrate. This effect is related to an increase of the light-matter interaction time due to the strong scattering of the excitation light in SiNW array. The prepared SiNWs are discussed as a kind of `black silicon', which can be formed in a large scale and can be used for photonic applications as well as in molecular sensing.

  15. Initial steps toward the realization of large area arrays of single photon counting pixels based on polycrystalline silicon TFTs

    NASA Astrophysics Data System (ADS)

    Liang, Albert K.; Koniczek, Martin; Antonuk, Larry E.; El-Mohri, Youcef; Zhao, Qihua; Jiang, Hao; Street, Robert A.; Lu, Jeng Ping

    2014-03-01

    The thin-film semiconductor processing methods that enabled creation of inexpensive liquid crystal displays based on amorphous silicon transistors for cell phones and televisions, as well as desktop, laptop and mobile computers, also facilitated the development of devices that have become ubiquitous in medical x-ray imaging environments. These devices, called active matrix flat-panel imagers (AMFPIs), measure the integrated signal generated by incident X rays and offer detection areas as large as ~43×43 cm2. In recent years, there has been growing interest in medical x-ray imagers that record information from X ray photons on an individual basis. However, such photon counting devices have generally been based on crystalline silicon, a material not inherently suited to the cost-effective manufacture of monolithic devices of a size comparable to that of AMFPIs. Motivated by these considerations, we have developed an initial set of small area prototype arrays using thin-film processing methods and polycrystalline silicon transistors. These prototypes were developed in the spirit of exploring the possibility of creating large area arrays offering single photon counting capabilities and, to our knowledge, are the first photon counting arrays fabricated using thin film techniques. In this paper, the architecture of the prototype pixels is presented and considerations that influenced the design of the pixel circuits, including amplifier noise, TFT performance variations, and minimum feature size, are discussed.

  16. Optical properties of silicon nanowire arrays formed by metal-assisted chemical etching: evidences for light localization effect.

    PubMed

    Osminkina, Liubov A; Gonchar, Kirill A; Marshov, Vladimir S; Bunkov, Konstantin V; Petrov, Dmitry V; Golovan, Leonid A; Talkenberg, Florian; Sivakov, Vladimir A; Timoshenko, Victor Yu

    2012-09-25

    We study the structure and optical properties of arrays of silicon nanowires (SiNWs) with a mean diameter of approximately 100 nm and length of about 1-25 μm formed on crystalline silicon (c-Si) substrates by using metal-assisted chemical etching in hydrofluoric acid solutions. In the middle infrared spectral region, the reflectance and transmittance of the formed SiNW arrays can be described in the framework of an effective medium with the effective refractive index of about 1.3 (porosity, approximately 75%), while a strong light scattering for wavelength of 0.3 ÷ 1 μm results in a decrease of the total reflectance of 1%-5%, which cannot be described in the effective medium approximation. The Raman scattering intensity under excitation at approximately 1 μm increases strongly in the sample with SiNWs in comparison with that in c-Si substrate. This effect is related to an increase of the light-matter interaction time due to the strong scattering of the excitation light in SiNW array. The prepared SiNWs are discussed as a kind of 'black silicon', which can be formed in a large scale and can be used for photonic applications as well as in molecular sensing.

  17. Proceedings of the Flat-Plate Solar Array Workshop on the Science of Silicon Material Preparation

    NASA Technical Reports Server (NTRS)

    1983-01-01

    Several areas of silicon material preparation were addressed including silicon production and purity, thermodynamics, kinetics, mechanisms, particle formation and growth, deposition in fluidized bed reactors, and chemical vapor deposition. Twenty-two papers were presented.

  18. Low cost solar array project silicon materials task. Development of a process for high capacity arc heater production of silicon for solar arrays

    NASA Technical Reports Server (NTRS)

    Reed, W. H.

    1978-01-01

    Silicon tetrachloride and a reductant (sodium) will be injected into an arc heated mixture of hydrogen and argon, yielding silicon and gaseous sodium chloride. Detailed characterization of the Sonicore sodium injection nozzle, using water as the test fluid was completed. Results indicated that flow rates of 45 gph sodium and 50 scfm argon should produce sufficiently small droplet sizes. The design effort was also completed for the test system preparation which was divided into two categories: (1) system components and (2) test system-laboratory integration.

  19. Development of a Thick-film Silicon Ribbon Growth Technique for Application to Large-area Solar Cells and Arrays

    NASA Technical Reports Server (NTRS)

    Berman, P. A.

    1973-01-01

    A new technique is described for growth of large-area silicon ribbons. This technique is an edge-defined, film-fed growth process by which single crystals can be grown having a shape controlled by the outside dimensions of a shaping die, growth taking place from an extremely thin film of liquid fed by capillary action from a crucible below. The material from which the die is fabricated is very critical to the process. The die must be wet by the silicon, but adverse impurities must not be introduced into the silicon, and the die must not become degraded by the molten silicon. A breakthrough in die fabrication that has allowed the growth of silicon ribbons having dimensions of 1 cm by 30 cm with a thickness of 0.7 mm is described. The implications of this significant advancement with respect to development of photovoltaic solar arrays for wide-scale terrestrial solar-to-electric energy conversion systems are discussed.

  20. Evaluation of selected chemical processes for production of low-cost silicon phase 2. silicon material task, low-cost silicon solar array project

    NASA Technical Reports Server (NTRS)

    Blocher, J. M., Jr.; Browning, M. F.; Rose, E. E.; Thompson, W. B.; Schmitt, W. A.; Fippin, J. S.; Kidd, R. W.; Liu, C. Y.; Kerbler, P. S.; Ackley, W. R.

    1978-01-01

    Progress from October 1, 1977, through December 31, 1977, is reported in the design of the 50 MT/year experimental facility for the preparation of high purity silicon by the zinc vapor reduction of silicon tetrachloride in a fluidized bed of seed particles to form a free flowing granular product.

  1. Quantitative Analysis of Defects in Silicon. Silicon Sheet Growth Development for the Large Area Silicon Sheet Task of the Low-cost Solar Array Project

    NASA Technical Reports Server (NTRS)

    Natesh, R.; Smith, J. M.; Qidwai, H. A.

    1979-01-01

    The various steps involved in the chemical polishing and etching of silicon samples are described. Data on twins, dislocation pits, and grain boundaries from thirty-one (31) silicon sample are also discussed. A brief review of the changes made to upgrade the image analysis system is included.

  2. Development and evaluation of die and container materials. Low cost silicon solar array project

    NASA Technical Reports Server (NTRS)

    Wills, R. R.; Niesx, D. E.

    1979-01-01

    Specific compositions of high purity silicon aluminum oxynitride (Sialon) and silicon beryllium oxynitride (Sibeon) solid solutions were shown to be promising refractory materials for handling and manipulating solar grade silicon into silicon ribbon. Evaulation of the interaction of these materials in contact with molten silicon indicated that solid solutions based upon beta-Si3N4 were more stable than those based on Si2N2O. Sibeon was more resistant to molten silicon attack than Sialon. Both materials should preferably be used in an inert atmosphere rather than under vacuum conditions because removal of oxygen from the silicon melt occurs as SiO enhances the dissolution of aluminum and beryllium. The wetting angles of these materials were low enough for these materials to be considered as both die and container materials.

  3. Characterization of electrothermal actuators and arrays fabricated in a four-level, planarized surface-micromachined polycrystalline silicon process

    SciTech Connect

    Comtois, J.H.; Michalicek, M.A.; Barron, C.C.

    1997-06-01

    This paper presents the results of tests performed on a variety of electrothermal microactuators and arrays of these actuators recently fabricated in the four-level planarized polycrystalline silicon (polysilicon) SUMMiT process at the U.S. Department of Energy`s Sandia National Laboratories. These results are intended to aid designers of thermally actuated mechanisms, and will apply to similar actuators made in other polysilicon MEMS processes. The measurements include force and deflection versus input power, maximum operating frequency, effects of long term operation, and ideal actuator and array geometries for different design criteria. A typical application in a stepper motor is shown to illustrate the utility of these actuators and arrays.

  4. Hollow silicon microneedle array based trans-epidermal antiemetic patch for efficient management of chemotherapy induced nausea and vomiting

    NASA Astrophysics Data System (ADS)

    Kharbikar, Bhushan N.; Kumar S., Harish; Kr., Sindhu; Srivastava, Rohit

    2015-12-01

    Chemotherapy Induced Nausea and Vomiting (CINV) is a serious health concern in the treatment of cancer patients. Conventional routes for administering anti-emetics (i.e. oral and parenteral) have several drawbacks such as painful injections, poor patient compliance, dependence on skilled personnel, non-affordability to majority of population (parenteral), lack of programmability and suboptimal bioavailability (oral). Hence, we have developed a trans-epidermal antiemetic drug delivery patch using out-of-plane hollow silicon microneedle array. Microneedles are pointed micron-scale structures that pierce the epidermal layer of skin to reach dermal blood vessels and can directly release the drug in their vicinity. They are painless by virtue of avoiding significant contact with dermal sensory nerve endings. This alternate approach gives same pharmacodynamic effects as par- enteral route at a sparse drug-dose requirement, hence negligible side-effects and improved patient compliance. Microneedle design attributes were derived by systematic study of human skin anatomy, natural micron-size structures like wasp-sting and cactus-spine and multi-physics simulations. We used deep reactive ion etching with Bosch process and optimized recipe of gases to fabricate high-aspect-ratio hollow silicon microneedle array. Finally, microneedle array and polydimethylsiloxane drug reservoir were assembled to make finished anti-emetic patch. We assessed microneedles mechanical stability, physico-chemical properties and performed in-vitro, ex- vivo and in-vivo studies. These studies established functional efficacy of the device in trans-epidermal delivery of anti-emetics, its programmability, ease of use and biosafety. Thus, out-of-plane hollow silicon microneedle array trans-epidermal antiemetic patch is a promising strategy for painless and effective management of CINV at low cost in mainstream healthcare.

  5. Performance of in-pixel circuits for photon counting arrays (PCAs) based on polycrystalline silicon TFTs.

    PubMed

    Liang, Albert K; Koniczek, Martin; Antonuk, Larry E; El-Mohri, Youcef; Zhao, Qihua; Street, Robert A; Lu, Jeng Ping

    2016-03-07

    Photon counting arrays (PCAs), defined as pixelated imagers which measure the absorbed energy of x-ray photons individually and record this information digitally, are of increasing clinical interest. A number of PCA prototypes with a 1 mm pixel-to-pixel pitch have recently been fabricated with polycrystalline silicon (poly-Si)-a thin-film technology capable of creating monolithic imagers of a size commensurate with human anatomy. In this study, analog and digital simulation frameworks were developed to provide insight into the influence of individual poly-Si transistors on pixel circuit performance-information that is not readily available through empirical means. The simulation frameworks were used to characterize the circuit designs employed in the prototypes. The analog framework, which determines the noise produced by individual transistors, was used to estimate energy resolution, as well as to identify which transistors contribute the most noise. The digital framework, which analyzes how well circuits function in the presence of significant variations in transistor properties, was used to estimate how fast a circuit can produce an output (referred to as output count rate). In addition, an algorithm was developed and used to estimate the minimum pixel pitch that could be achieved for the pixel circuits of the current prototypes. The simulation frameworks predict that the analog component of the PCA prototypes could have energy resolution as low as 8.9% full width at half maximum (FWHM) at 70 keV; and the digital components should work well even in the presence of significant thin-film transistor (TFT) variations, with the fastest component having output count rates as high as 3 MHz. Finally, based on conceivable improvements in the underlying fabrication process, the algorithm predicts that the 1 mm pitch of the current PCA prototypes could be reduced significantly, potentially to between ~240 and 290 μm.

  6. Performance of in-pixel circuits for photon counting arrays (PCAs) based on polycrystalline silicon TFTs

    NASA Astrophysics Data System (ADS)

    Liang, Albert K.; Koniczek, Martin; Antonuk, Larry E.; El-Mohri, Youcef; Zhao, Qihua; Street, Robert A.; Lu, Jeng Ping

    2016-03-01

    Photon counting arrays (PCAs), defined as pixelated imagers which measure the absorbed energy of x-ray photons individually and record this information digitally, are of increasing clinical interest. A number of PCA prototypes with a 1 mm pixel-to-pixel pitch have recently been fabricated with polycrystalline silicon (poly-Si)—a thin-film technology capable of creating monolithic imagers of a size commensurate with human anatomy. In this study, analog and digital simulation frameworks were developed to provide insight into the influence of individual poly-Si transistors on pixel circuit performance—information that is not readily available through empirical means. The simulation frameworks were used to characterize the circuit designs employed in the prototypes. The analog framework, which determines the noise produced by individual transistors, was used to estimate energy resolution, as well as to identify which transistors contribute the most noise. The digital framework, which analyzes how well circuits function in the presence of significant variations in transistor properties, was used to estimate how fast a circuit can produce an output (referred to as output count rate). In addition, an algorithm was developed and used to estimate the minimum pixel pitch that could be achieved for the pixel circuits of the current prototypes. The simulation frameworks predict that the analog component of the PCA prototypes could have energy resolution as low as 8.9% full width at half maximum (FWHM) at 70 keV; and the digital components should work well even in the presence of significant thin-film transistor (TFT) variations, with the fastest component having output count rates as high as 3 MHz. Finally, based on conceivable improvements in the underlying fabrication process, the algorithm predicts that the 1 mm pitch of the current PCA prototypes could be reduced significantly, potentially to between ~240 and 290 μm.

  7. Quantitative analysis of defects in silicon: Silicon sheet growth development for the large area silicon sheet task of the low cost solar array project

    NASA Technical Reports Server (NTRS)

    Natesh, R.; Smith, J. M.; Qidwai, H. A.

    1978-01-01

    The various steps involved in the chemical polishing and etching of silicon samples are described and the data on twins, grain boundaries and dislocation pits from fifty-three (53) samples are discussed.

  8. Silicon sheet growth development for the large area silicon sheet task of the low cost solar array project. Quantitative analysis of defects in silicon

    NASA Technical Reports Server (NTRS)

    Natesh, R.

    1978-01-01

    The various steps involved in obtaining quantitative information of structural defects in crystalline silicon samples are described. Procedures discussed include: (1) chemical polishing; (2) chemical etching; and (3) automated image analysis of samples on the QTM 720 System.

  9. Dip-coating process: Silicon sheet growth development for the large-area silicon sheet task of the low-cost silicon solar array project

    NASA Technical Reports Server (NTRS)

    Zook, J. D.; Heaps, J. D.; Maciolek, R. B.; Koepke, B. G.; Gutter, C. D.; Schuldt, S. B.

    1977-01-01

    The objective of this research program is to investigate the technical and economic feasibility of producing solar-cell-quality sheet silicon by coating one surface of carbonized ceramic substrates with a thin layer of large-grain polycrystalline silicon from the melt. The past quarter demonstrated significant progress in several areas. Seeded growth of silicon-on-ceramic (SOC) with an EFG ribbon seed was demonstrated. Different types of mullite were successfully coated with silicon. A new method of deriving minority carrier diffusion length, L sub n from spectral response measurements was evaluated. ECOMOD cost projections were found to be in good agreement with the interim SAMIS method proposed by JPL. On the less positive side, there was a decrease in cell performance which we believe to be due to an unidentified source of impurities.

  10. Fabrication of CoFe2O4 ferrite nanowire arrays in porous silicon template and their local magnetic properties

    NASA Astrophysics Data System (ADS)

    Hui, Zheng; Man-Gui, Han; Long-Jiang, Deng

    2016-02-01

    CoFe2O4 ferrite nanowire arrays are fabricated in porous silicon templates. The porous silicon templates are prepared via metal-assisted chemical etching with gold (Au) nanoparticles as the catalyst. Subsequently, CoFe2O4 ferrite nanowires are successfully synthesized into porous silicon templates by the sol-gel method. The magnetic hysteresis loop of nanowire array shows an isotropic feature of magnetic properties. The coercivity and squareness ratio (Mr/Ms) of ensemble nanowires are found to be 630 Oe (1 Oe, = 79.5775 A·m-1 and 0.4 respectively. However, the first-order reversal curve (FORC) is adopted to reveal the probability density function of local magnetostatic properties (i.e., interwire interaction field and coercivity). The FORC diagram shows an obvious distribution feature for interaction field and coercivity. The local coercivity with a value of about 1000 Oe is found to have the highest probability. Project supported by the National Natural Science Foundation of China (Grant No. 61271039), the Scientific Projects of Sichuan Province, China (Grant No. 2015HH0016), and the Natural Science Foundations of Zhejiang Province, China (Grant Nos. LQ12E02001 and Y107255).

  11. Thermal and Cold Neutron Computed Tomography at the Los Alamos Neutron Scattering Center Using an Amorphous Silicon Detector Array

    SciTech Connect

    Claytor, T.N.; Schwab, M.J.; Farnum, E.H.; McDonald, T.E.; Summa, D.A.; Sheats, M.J.; Stupin, D.M.; Sievers, W.L.

    1998-07-19

    The use of the EG and G-Heimann RTM 128 or dpiX FS20 amorphous silicon (a-Si) detector array for thermal neutron radiography/computed tomography has proven to be a quick and efficient means of producing high quality digital radiographic images. The resolution, although not as good as film, is about 750 pm with the RTM and 127 pm with the dpiX array with a dynamic range in excess of 2,800. In many respects using an amorphous silicon detector is an improvement over other techniques such as imaging with a CCD camera, using a storage phosphor plate or film radiography. Unlike a CCD camera, which is highly susceptible to radiation damage, a-Si detectors can be placed in the beam directly behind the object under examination and do not require any special optics or turning mirrors. The amorphous silicon detector also allows enough data to be acquired to construct a digital image in just a few seconds (minimum gate time 40 ms) whereas film or storage plate exposures can take many minutes and then need to be digitized with a scanner. The flat panel can therefore acquire a complete 3D computed tomography data set in just a few tens of minutes. While a-Si detectors have been proposed for use in imaging neutron beams, this is the first reported implementation of such a detector for neutron imaging.

  12. Reduction of Cr(VI) to Cr(III) using silicon nanowire arrays under visible light irradiation.

    PubMed

    Fellahi, Ouarda; Barras, Alexandre; Pan, Guo-Hui; Coffinier, Yannick; Hadjersi, Toufik; Maamache, Mustapha; Szunerits, Sabine; Boukherroub, Rabah

    2016-03-05

    We report an efficient visible light-induced reduction of hexavalent chromium Cr(VI) to trivalent Cr(III) by direct illumination of an aqueous solution of potassium dichromate (K2Cr2O7) in the presence of hydrogenated silicon nanowires (H-SiNWs) or silicon nanowires decorated with copper nanoparticles (Cu NPs-SiNWs) as photocatalyst. The SiNW arrays investigated in this study were prepared by chemical etching of crystalline silicon in HF/AgNO3 aqueous solution. The Cu NPs were deposited on SiNW arrays via electroless deposition technique. Visible light irradiation of an aqueous solution of K2Cr2O7 (10(-4)M) in presence of H-SiNWs showed that these substrates were not efficient for Cr(VI) reduction. The reduction efficiency achieved was less than 10% after 120 min irradiation at λ>420 nm. Addition of organic acids such as citric or adipic acid in the solution accelerated Cr(VI) reduction in a concentration-dependent manner. Interestingly, Cu NPs-SiNWs was found to be a very efficient interface for the reduction of Cr(VI) to Cr(III) in absence of organic acids. Almost a full reduction of Cr(VI) was achieved by direct visible light irradiation for 140 min using this photocatalyst.

  13. Silicon-based antenna-coupled polarization-sensitive millimeter-wave bolometer arrays for cosmic microwave background instruments

    NASA Astrophysics Data System (ADS)

    Rostem, Karwan; Ali, Aamir; Appel, John W.; Bennett, Charles L.; Brown, Ari; Chang, Meng-Ping; Chuss, David T.; Colazo, Felipe A.; Costen, Nick; Denis, Kevin L.; Essinger-Hileman, Tom; Hu, Ron; Marriage, Tobias A.; Moseley, Samuel H.; Stevenson, Thomas R.; U-Yen, Kongpop; Wollack, Edward J.; Xu, Zhilei

    2016-07-01

    We describe feedhorn-coupled polarization-sensitive detector arrays that utilize monocrystalline silicon as the dielectric substrate material. Monocrystalline silicon has a low-loss tangent and repeatable dielectric constant, characteristics that are critical for realizing efficient and uniform superconducting microwave circuits. An additional advantage of this material is its low specific heat. In a detector pixel, two Transition-Edge Sensor (TES) bolometers are antenna-coupled to in-band radiation via a symmetric planar orthomode transducer (OMT). Each orthogonal linear polarization is coupled to a separate superconducting microstrip transmission line circuit. On-chip filtering is employed to both reject out-of-band radiation from the upper band edge to the gap frequency of the niobium superconductor, and to flexibly define the bandwidth for each TES to meet the requirements of the application. The microwave circuit is compatible with multi-chroic operation. Metalized silicon platelets are used to define the backshort for the waveguide probes. This micro-machined structure is also used to mitigate the coupling of out-of-band radiation to the microwave circuit. At 40 GHz, the detectors have a measured efficiency of ˜90%. In this paper, we describe the development of the 90 GHz detector arrays that will be demonstrated using the Cosmology Large Angular Scale Surveyor (CLASS) ground-based telescope.

  14. Silicon-on ceramic process: Silicon sheet growth and device development for the large-area silicon sheet task of the low-cost solar array project

    NASA Technical Reports Server (NTRS)

    Grung, B. L.; Heaps, J. D.; Schmit, F. M.; Schuldt, S. B.; Zook, J. D.

    1981-01-01

    The technical feasibility of producing solar-cell-quality sheet silicon to meet the Department of Energy (DOE) 1986 overall price goal of $0.70/watt was investigated. With the silicon-on-ceramic (SOC) approach, a low-cost ceramic substrate is coated with large-grain polycrystalline silicon by unidirectional solidification of molten silicon. This effort was divided into several areas of investigation in order to most efficiently meet the goals of the program. These areas include: (1) dip-coating; (2) continuous coating designated SCIM-coating, and acronym for Silicon Coating by an Inverted Meniscus (SCIM); (3) material characterization; (4) cell fabrication and evaluation; and (5) theoretical analysis. Both coating approaches were successful in producing thin layers of large grain, solar-cell-quality silicon. The dip-coating approach was initially investigated and considerable effort was given to this technique. The SCIM technique was adopted because of its scale-up potential and its capability to produce more conventiently large areas of SOC.

  15. Hybrid solar cells with conducting polymers and vertically aligned silicon nanowire arrays: The effect of silicon conductivity

    NASA Astrophysics Data System (ADS)

    Woo, Sungho; Hoon Jeong, Jae; Kun Lyu, Hong; Jeong, Seonju; Hyoung Sim, Jun; Hyun Kim, Wook; Soo Han, Yoon; Kim, Youngkyoo

    2012-08-01

    Organic/inorganic hybrid solar cells, based on vertically aligned n-type silicon nanowires (n-Si NWs) and p-type conducting polymers (PEDOT:PSS), were investigated as a function of Si conductivity. The n-Si NWs were easily prepared from the n-Si wafer by employing a silver nanodot-mediated micro-electrochemical redox reaction. This investigation shows that the photocurrent-to-voltage characteristics of the n-Si NW/PEDOT:PSS cells clearly exhibit a stable rectifying diode behavior. The increase in current density and fill factor using high conductive silicon is attributed to an improved charge transport towards the electrodes achieved by lowering the device's series resistance. Our results also show that the surface area of the nanowire that can form heterojunction domains significantly influences the device performance.

  16. SU-E-J-91: Novel Epitaxial Silicon Array for Quality Assurance in Photon and Proton Therapy

    SciTech Connect

    Talamonti, C; Zani, M; Scaringella, M; Bruzzi, M; Bucciolini, M; Menichelli, D; Friedl, F

    2014-06-01

    Purpose: to demonstrate suitability of a novel silicon array for measuring the dose properties of highly conformal photon and proton beams. Methods: prototype under test is a 24cm long linear array prototype, although the underlying technology is suitable to construct 2D arrays as well. It is based on a 64pixels monolithic sensor with 1mm pixel pitch, made of epitaxial ptype silicon. Thanks to design modularity, more sensors can be placed side by side without breaking pixel pitch. Flattened and unflattened photon beams, as well as proton radiation from a cyclotron in pencil beam scanning mode, were considered. Measurements of beam characteristics as percentage depth doses, dose profiles, output factors and energy response, which are necessary to deliver radiation with high precision and reliability, were performed. Results: Dose rate independence with photons was verified in the dose per pulse range 0.03 to 2mGy. Results clearly indicate nondependence of the detector sensitivity both for flattened and unflattened beams, with a variation of at most 0.5percentage. OFs were obtained for field with a lateral size ranging from 0.8cm to 16cm and the results are in good agreement with ion chamber A1SL, max difference less than 1.5percentage. Field sizes and beam penumbra were measured and compared to EBT film results. Concerning proton beams, sensitivity independence on dose rate was verified by changing the beam current in the interval 2-130Gy/s. Field sizes and beam penumbra measurements are in agreement with data taken with a scintillating 2D array with 0.5mm resolution IBA Lynx, and a better penumbra definition than an array of ionization chambers IBA MatriXX is reached. Conclusion: The device is a novel and valuable tool for QA both for photon and proton dose delivery. All measurements demonstrated its capability to measure with high spatial resolution many crucial properties of the RT beam.

  17. Core-shell heterojunction of silicon nanowire arrays and carbon quantum dots for photovoltaic devices and self-driven photodetectors.

    PubMed

    Xie, Chao; Nie, Biao; Zeng, Longhui; Liang, Feng-Xia; Wang, Ming-Zheng; Luo, Linbao; Feng, Mei; Yu, Yongqiang; Wu, Chun-Yan; Wu, Yucheng; Yu, Shu-Hong

    2014-04-22

    Silicon nanostructure-based solar cells have lately intrigued intensive interest because of their promising potential in next-generation solar energy conversion devices. Herein, we report a silicon nanowire (SiNW) array/carbon quantum dot (CQD) core-shell heterojunction photovoltaic device by directly coating Ag-assisted chemical-etched SiNW arrays with CQDs. The heterojunction with a barrier height of 0.75 eV exhibited excellent rectifying behavior with a rectification ratio of 10(3) at ±0.8 V in the dark and power conversion efficiency (PCE) as high as 9.10% under AM 1.5G irradiation. It is believed that such a high PCE comes from the improved optical absorption as well as the optimized carrier transfer and collection capability. Furthermore, the heterojunction could function as a high-performance self-driven visible light photodetector operating in a wide switching wavelength with good stability, high sensitivity, and fast response speed. It is expected that the present SiNW array/CQD core-shell heterojunction device could find potential applications in future high-performance optoelectronic devices.

  18. Static and dynamic characterization of robust superhydrophobic surfaces built from nano-flowers on silicon micro-post arrays

    NASA Astrophysics Data System (ADS)

    Chen, Longquan; Xiao, Zhiyong; Chan, Philip C. H.; Lee, Yi-Kuen

    2010-10-01

    Superhydrophobic nano-flower surfaces were fabricated using MEMS technology and microwave plasma-enhanced chemical vapor deposition (MPCVD) of carbon nanotubes on silicon micro-post array surfaces. The nano-flower structures can be readily formed within 1-2 min on the micro-post arrays with the spacing ranging from 25 to 30 µm. The petals of the nano-flowers consisted of clusters of multi-wall carbon nanotubes. Patterned nano-flower structures were characterized using various microscopy techniques. After MPCVD, the apparent contact angle (160 ± 0.2°), abbreviated as ACA (defined as the measured angle between the apparent solid surface and the tangent to the liquid-fluid interface), of the nano-flower surfaces increased by 139% compared with that of the silicon micro-post arrays. The measured ACA of the nano-flower surface is consistent with the predicted ACA from a modified Cassie-Baxter equation. A high-speed CCD camera was used to study droplet impact dynamics on various micro/nanostructured surfaces. Both static testing (ACA and sliding angle) and droplet impact dynamics demonstrated that, among seven different micro/nanostructured surfaces, the nano-flower surfaces are the most robust superhydrophobic surfaces.

  19. Silicon nanowire array/Cu2O crystalline core-shell nanosystem for solar-driven photocatalytic water splitting

    NASA Astrophysics Data System (ADS)

    Xiong, Zuzhou; Zheng, Maojun; Liu, Sida; Ma, Li; Shen, Wenzhong

    2013-07-01

    P-type Cu2O nanocrystals were deposited on n-type silicon nanowire arrays (Si NWs) to form core-shell heterojunction arrays structure via a simple electroless deposition technique. Scanning electron microscopy, transmission electron microscope and x-ray diffraction were utilized to characterize the morphology and structure of the core-shell nanosystem. The reflectivity of the obtained core-shell structure measured by UV/vis spectrometry showed a comparatively low reflectivity in the visible-light region, which implied good optical absorption performance. The water splitting performance of the obtained Si NWs, planar Si/Cu2O structure and Si NW/Cu2O core-shell nanosystem were studied. Owing to the large specific surface area, heterojunctions formed between Cu2O nanocrystallites and Si NWs and the light trapping effect of the NW array structure, the photocatalytic performance of the Si NW/Cu2O core-shell nanosystem increased markedly compared with that of pure silicon NWs and a planar Si/Cu2O structure, which means excellent hydrogen production capacity under irradiation with simulated sunlight. In addition, the photocatalytic performance of the core-shell nanosystem was improved obviously after platinum nanoparticles were electrodeposited on it.

  20. Proceedings of the Flat-Plate Solar Array Project Workshop on Crystal Gowth for High-Efficiency Silicon Solar Cells

    NASA Technical Reports Server (NTRS)

    Dumas, K. A. (Editor)

    1985-01-01

    A Workshop on Crystal Growth for High-Efficiency Silicon Solar Cells was held December 3 and 4, 1984, in San Diego, California. The Workshop offered a day and a half of technical presentations and discussions and an afternoon session that involved a panel discussion and general discussion of areas of research that are necessary to the development of materials for high-efficiency solar cells. Topics included the theoretical and experimental aspects of growing high-quality silicon crystals, the effects of growth-process-related defects on photovoltaic devices, and the suitability of various growth technologies as cost-effective processes. Fifteen invited papers were presented, with a discussion period following each presentation. The meeting was organized by the Flat-Plate Solar Array Project of the Jet Propulsion Laboratory. These Proceedings are a record of the presentations and discussions, edited for clarity and continuity.

  1. Nanopillar array band-edge laser cavities on silicon-on-insulator for monolithic integrated light sources

    NASA Astrophysics Data System (ADS)

    Lee, Wook-Jae; Kim, Hyunseok; Farrell, Alan C.; Senanayake, Pradeep; Huffaker, Diana L.

    2016-02-01

    A simple and unique laser scheme comprised of a finite-size nanopillar array on a silicon-on-insulator grating layer is introduced for realizing an on-chip monolithically integrated light source. A photonic band-edge mode, confined by the grating substrate in the vertical direction, shows a quality factor as high as 4000. We show that the proposed laser cavity allows direct coupling into a waveguide, which is essential for monolithic integration. In addition, III-V semiconductor nanopillars are grown on a silicon-on-insulator grating substrate in order to demonstrate the feasibility of epitaxy on 3D surfaces. These results provide a practical solution for on-chip integration of a monolithic light source.

  2. Performance improvement in silicon arrayed waveguide grating by suppression of scattering near the boundary of a star coupler.

    PubMed

    Park, Jaegyu; Kim, Gyungock; Park, Hyundai; Joo, Jiho; Kim, Sanggi; Kwack, Myung-Joon

    2015-06-10

    We investigate the reduction of transition loss across the star coupler boundary in a silicon arrayed waveguide grating (AWG) by suppressing multimode generation and scattering near the boundary of a star coupler. Eight-channel silicon AWGs were designed with optimal conditions based on enhanced field matching in combination with ultrashallow etched structures. The fabricated AWG demonstrates an insertion loss down to 0.63 dB with a cross talk of -23 to -25.3 dB, exhibiting ~0.8 dB improvement of insertion loss and ~4 dB improvement of cross talk compared to the Si AWG fabricated with a conventional double-etch technique.

  3. Gold-Free Ternary III–V Antimonide Nanowire Arrays on Silicon: Twin-Free down to the First Bilayer

    PubMed Central

    2013-01-01

    With the continued maturation of III–V nanowire research, expectations of material quality should be concomitantly raised. Ideally, III–V nanowires integrated on silicon should be entirely free of extended planar defects such as twins, stacking faults, or polytypism, position-controlled for convenient device processing, and gold-free for compatibility with standard complementary metal–oxide–semiconductor (CMOS) processing tools. Here we demonstrate large area vertical GaAsxSb1–x nanowire arrays grown on silicon (111) by molecular beam epitaxy. The nanowires’ complex faceting, pure zinc blende crystal structure, and composition are mapped using characterization techniques both at the nanoscale and in large-area ensembles. We prove unambiguously that these gold-free nanowires are entirely twin-free down to the first bilayer and reveal their three-dimensional composition evolution, paving the way for novel infrared devices integrated directly on the cost-effective Si platform. PMID:24329502

  4. WE-AB-BRB-04: A Novel Monolithic Silicon 2D Detector Array for Use in Stereotactic Applications

    SciTech Connect

    Gargett, M; Petasecca, M; Alnaghy, S; Rosenfeld, A; Oborn, B; Metcalfe, P

    2015-06-15

    Purpose: To assess the capability of a novel 2D monolithic silicon detector array in measuring stereotactic photon fields. Methods: The silicon array detector used in this work, named Magic Plate-512 (MP512), is a thin monolithic silicon wafer (52 × 52 × 0.47 mm{sup 3}) with 512 ion-implanted diodes (0.5 × 0.5 mm{sup 2}). Adjacent pixels are spaced evenly with 2 mm pitch, covering a maximum detection area 46 mm wide. Its fast, FPGA based read-out system is synchronised with the linac to allow readout of all pixels pulse-by-pulse. A clinical SABR lung plan (consisting of 9 single segment beams, 6MV) was measured with the array at 1.5 cm depth in a solid water phantom (100 cm SSD). The typical field size was in the range of 3 × 3 cm{sup 2} to 4 × 4 cm{sup 2}. Each beam was delivered at perpendicular incidence to the detector plane so as to avoid the need for angular dependence corrections. The fields were measured under the same conditions using Gafchromic EBT3 film for comparison. The film was scanned at 72 dpi resolution, with the red channel data used for analysis. Results: Average gamma passing rates of (92.3 ± 1.8) % for 2%/2mm criteria, and (86.6 ± 2.3) % for 1%/2mm criteria were achieved for MP512, using EBT3 film as the reference distribution. The detector array was able to accurately measure the full-width-at-half-maximum (FWHM), to within (0.77 ± 0.01) mm accuracy when compared to film. The penumbral widths (80%-20%) were measured to within (0.30 ± 0.01) mm accuracy to film. Conclusion: The MP512 is a feasible option for measurement of stereotactic photon fields, with its high density of detection points making it useful for small field applications. The prototype array has demonstrated merit; in the future the development of a larger array detection area would be beneficial for clinical applications.

  5. Silicon/SU8 multi-electrode micro-needle for in vivo neurochemical monitoring.

    PubMed

    Vasylieva, Natalia; Marinesco, Stéphane; Barbier, Daniel; Sabac, Andrei

    2015-10-15

    Simultaneous monitoring of glucose and lactate is an important challenge for understanding brain energetics in physiological or pathological states. We demonstrate here a versatile method based on a minimally invasive single implantation in the rat brain. A silicon/SU8-polymer multi-sensing needle-shaped biosensor, was fabricated and tested. The multi-electrode array design comprises three platinum planar microelectrodes with a surface area of 40 × 200 µm(2) and a spacing of 200 µm, which were micromachined on a single 3mm long micro-needle having a 100 × 50 µm(2) cross-section for reduced tissue damage during implantation. Platinum micro-electrodes were aligned at the bottom of micro-wells obtained by photolithography on a SU8 photoresist layer. After clean room processing, each micro-electrode was functionalized inside the micro-wells by means of a micro-dispensing device, either with glucose oxidase or with lactate oxidase, which were cross-linked on the platinum electrodes. The third electrode covered with Bovine Serum Albumin (BSA) was used for the control of non-specific currents. The thick SU8 photoresist layer has revealed excellent electrical insulation of the micro-electrodes and between interconnection lines, and ensured a precise localization and packaging of the sensing enzymes on platinum micro-electrodes. During in vitro calibration with concentrations of analytes in the mM range, the micro-wells patterned in the SU8 photoresist proved to be highly effective in eliminating cross-talk signals, caused by H2O2 diffusion from closely spaced micro-electrodes. Moreover, our biosensor was successfully assayed in the rat cortex for simultaneous monitoring of both glucose and lactate during insulin and glucose administration.

  6. Development of a process for high capacity arc heater production of silicon for solar arrays

    NASA Technical Reports Server (NTRS)

    Meyer, T. N.

    1980-01-01

    A high temperature silicon production process using existing electric arc heater technology is discussed. Silicon tetrachloride and a reductant, liquid sodium, were injected into an arc heated mixture of hydrogen and argon. Under these high temperature conditions, a very rapid reaction occurred, yielding silicon and gaseous sodium chloride. Techniques for high temperature separation and collection of the molten silicon were developed. The desired degree of separation was not achieved. The electrical, control and instrumentation, cooling water, gas, SiCl4, and sodium systems are discussed. The plasma reactor, silicon collection, effluent disposal, the gas burnoff stack, and decontamination and safety are also discussed. Procedure manuals, shakedown testing, data acquisition and analysis, product characterization, disassembly and decontamination, and component evaluation are reviewed.

  7. Highly featured amorphous silicon nanorod arrays for high-performance lithium-ion batteries

    SciTech Connect

    Soleimani-Amiri, Samaneh; Safiabadi Tali, Seied Ali; Azimi, Soheil; Sanaee, Zeinab; Mohajerzadeh, Shamsoddin

    2014-11-10

    High aspect-ratio vertical structures of amorphous silicon have been realized using hydrogen-assisted low-density plasma reactive ion etching. Amorphous silicon layers with the thicknesses ranging from 0.5 to 10 μm were deposited using radio frequency plasma enhanced chemical vapor deposition technique. Standard photolithography and nanosphere colloidal lithography were employed to realize ultra-small features of the amorphous silicon. The performance of the patterned amorphous silicon structures as a lithium-ion battery electrode was investigated using galvanostatic charge-discharge tests. The patterned structures showed a superior Li-ion battery performance compared to planar amorphous silicon. Such structures are suitable for high current Li-ion battery applications such as electric vehicles.

  8. Low-cost solar array project task 1: Silicon material. Gaseous melt replenishment system

    NASA Technical Reports Server (NTRS)

    Jewett, D. N.; Bates, H. E.; Hill, D. M.

    1980-01-01

    The operation of a silicon production technique was demonstrated. The essentials of the method comprise chemical vapor deposition of silicon, by hydrogen reduction of chlorosilanes, on the inside of a quartz reaction vessel having large internal surface area. The system was designed to allow successive deposition-melting cycles, with silicon removal being accomplished by discharging the molten silicon. The liquid product would be suitable for transfer to a crystal growth process, casting into solid form, or production of shots. A scaled-down prototype reactor demonstrated single pass conversion efficiency of 20 percent and deposition rates and energy consumption better than conventional Siemens reactors, via deposition rates of 365 microns/hr. and electrical consumption of 35 Kwhr/kg of silicon produced.

  9. Low-cost silicon solar array project environmental hail model for assessing risk to solar collectors

    NASA Technical Reports Server (NTRS)

    Gonzalez, C.

    1977-01-01

    The probability of solar arrays being struck by hailstones of various sizes as a function of geographic location and service life was assessed. The study complements parallel studies of solar array sensitivity to hail damage, the final objective being an estimate of the most cost effective level for solar array hail protection.

  10. Supermode dispersion and waveguide-to-slot mode transition in arrays of silicon-on-insulator waveguides.

    PubMed

    de Nobriga, Charles E; Hobbs, Gareth D; Wadsworth, William J; Knight, Jonathan C; Skryabin, Dmitry V; Samarelli, Antonio; Sorel, Marc; De La Rue, Richard M

    2010-12-01

    In this Letter, we report group index measurements of the supermodes of an array of two strongly coupled silicon-on-insulator waveguides. We observe coupling-induced dispersion that is greater than the material and waveguide dispersion of the individual waveguides. We demonstrate that the system transforms from supporting the two supermodes associated with two coupled waveguides to the single mode of a slot waveguide within the investigated spectral range. During the cutoff of the antisymmetric supermode, an anti-crossing between the symmetric TM and antisymmetric TE supermodes has been observed.

  11. Slicing of Silicon into Sheet Material. Silicon Sheet Growth Development for the Large Area Silicon Sheet Task of the Low Cost Solar Array Project

    NASA Technical Reports Server (NTRS)

    Fleming, J. R.; Holden, S. C.; Wolfson, R. G.

    1979-01-01

    The use of multiblade slurry sawing to produce silicon wafers from ingots was investigated. The commercially available state of the art process was improved by 20% in terms of area of silicon wafers produced from an ingot. The process was improved 34% on an experimental basis. Economic analyses presented show that further improvements are necessary to approach the desired wafer costs, mostly reduction in expendable materials costs. Tests which indicate that such reduction is possible are included, although demonstration of such reduction was not completed. A new, large capacity saw was designed and tested. Performance comparable with current equipment (in terms of number of wafers/cm) was demonstrated.

  12. Low earth orbit durability of protected silicone for refractive photovoltaic concentrator arrays

    NASA Technical Reports Server (NTRS)

    McCollum, Timothy A.; deGroh, Kim K.

    1995-01-01

    Photovoltaic power systems with novel refractive silicone solar concentrators are being developed for use in low Earth orbit (LEO). Because of the vulnerability of silicones to atomic oxygen and ultraviolet radiation, these lenses are coated with a multilayer metal oxide protective coating. The objective of this work was to evaluate the effects of atomic oxygen and thermal exposures on multilayer coated silicone. Samples were exposed to high-fluence ground-laboratory and low-fluence in-space atomic oxygen. Ground testing resulted in decreases in both total and specular transmittance, while in-space exposure resulted in only small decreases in specular transmittance. A contamination film, attributed to exposed silicone at coating crack sites, was found to cause transmittance decreases during ground testing. Propagation of coating cracks was found to be the result of sample heating during exposure. The potential for silicone exposure, with the resulting degradation of optical properties from silicone contamination, indicates that this multilayer coated silicone is not durable for LEO space applications where thermal exposures will cause coating crack development and propagation.

  13. Flexible Near-Infrared Photovoltaic Devices Based on Plasmonic Hot-Electron Injection into Silicon Nanowire Arrays.

    PubMed

    Liu, Dong; Yang, Dong; Gao, Yang; Ma, Jun; Long, Ran; Wang, Chengming; Xiong, Yujie

    2016-03-24

    The development of flexible near-infrared (NIR) photovoltaic (PV) devices containing silicon meets the strong demands for solar utilization, portability, and sustainable manufacture; however, improvements in the NIR light absorption and conversion efficiencies in ultrathin crystalline Si are required. We have developed an approach to improve the quantum efficiency of flexible PV devices in the NIR spectral region by integrating Si nanowire arrays with plasmonic Ag nanoplates. The Ag nanoplates can directly harvest and convert NIR light into plasmonic hot electrons for injection into Si, while the Si nanowire arrays offer light trapping. Taking the wavelength of 800 nm as an example, the external quantum efficiency has been improved by 59 % by the integration Ag nanoplates. This work provides an alternative strategy for the design and fabrication of flexible NIR PVs.

  14. SERS detection of R6G based on a novel graphene oxide/silver nanoparticles/silicon pyramid arrays structure.

    PubMed

    Zhang, C; Jiang, S Z; Huo, Y Y; Liu, A H; Xu, S C; Liu, X Y; Sun, Z C; Xu, Y Y; Li, Z; Man, B Y

    2015-09-21

    We present a novel surface-enhanced Raman scattering (SERS) substrate based on graphene oxide/silver nanoparticles/silicon pyramid arrays structure (GO/Ag/PSi). The SERS behaviors are discussed and compared by the detection of R6G. Based on the contrast experiments with PSi, GO/PSi, Ag/PSi and GO/AgA/PSi as SERS substrate, the perfect bio-compatibility, good homogeneity and chemical stability were confirmed. We also calculated the electric field distributions using Finite-difference time-domain (FDTD) analysis to further understand the GO/Ag/PSi structure as a perfect SERS platform. These experimental and theoretical results imply that the GO/Ag/PSi with regular pyramids array is expected to be an effective substrate for label-free sensitive SERS detections in areas of medicine, food safety and biotechnology.

  15. Development of a Process for a High Capacity Arc Heater Production of Silicon for Solar Arrays

    NASA Technical Reports Server (NTRS)

    Reed, W. H.

    1979-01-01

    A program was established to develop a high temperature silicon production process using existing electric arc heater technology. Silicon tetrachloride and a reductant (sodium) are injected into an arc heated mixture of hydrogen and argon. Under these high temperature conditions, a very rapid reaction is expected to occur and proceed essentially to completion, yielding silicon and gaseous sodium chloride. Techniques for high temperature separation and collection were developed. Included in this report are: test system preparation; testing; injection techniques; kinetics; reaction demonstration; conclusions; and the project status.

  16. Chemiluminescence lateral flow immunoassay cartridge with integrated amorphous silicon photosensors array for human serum albumin detection in urine samples.

    PubMed

    Zangheri, Martina; Di Nardo, Fabio; Mirasoli, Mara; Anfossi, Laura; Nascetti, Augusto; Caputo, Domenico; De Cesare, Giampiero; Guardigli, Massimo; Baggiani, Claudio; Roda, Aldo

    2016-12-01

    A novel and disposable cartridge for chemiluminescent (CL)-lateral flow immunoassay (LFIA) with integrated amorphous silicon (a-Si:H) photosensors array was developed and applied to quantitatively detect human serum albumin (HSA) in urine samples. The presented analytical method is based on an indirect competitive immunoassay using horseradish peroxidase (HRP) as a tracer, which is detected by adding the luminol/enhancer/hydrogen peroxide CL cocktail. The system comprises an array of a-Si:H photosensors deposited on a glass substrate, on which a PDMS cartridge that houses the LFIA strip and the reagents necessary for the CL immunoassay was optically coupled to obtain an integrated analytical device controlled by a portable read-out electronics. The method is simple and fast with a detection limit of 2.5 mg L(-1) for HSA in urine and a dynamic range up to 850 mg L(-1), which is suitable for measuring physiological levels of HSA in urine samples and their variation in different diseases (micro- and macroalbuminuria). The use of CL detection allowed accurate and objective analyte quantification in a dynamic range that extends from femtomoles to picomoles. The analytical performances of this integrated device were found to be comparable with those obtained using a charge-coupled device (CCD) as a reference off-chip detector. These results demonstrate that integrating the a-Si:H photosensors array with CL-LFIA technique provides compact, sensitive and low-cost systems for CL-based bioassays with a wide range of applications for in-field and point-of-care bioanalyses. Graphical Abstract A novel integrated portable device was developed for direct quantitative detection of human serum albumin (HSA) in urine samples, exploiting a chemiluminescence lateral flow immunoassay (LFIA). The device comprises a cartridge that holds the LFIA strip and all the reagents necessary for the analysis, an array of amorphous silicon photosensors, and a custom read-out electronics.

  17. Quantitative analysis of defects in silicon. Silicon sheet growth development for the Large Area Silicon Sheet Task of the Low-Cost Solar Array Project. Final report

    SciTech Connect

    Natesh, R.; Smith, J.M.; Bruce, T.; Qidwai, H.A.

    1980-04-01

    The complete procedures for the defect analysis of silicon samples using a QTM-720 Image Analyzing System are described, chemical polishing, etching, and QTM operation are discussed. The data from one hundred and seventy four (174) samples, and a discussion of the data are included. The data include twin boundary density, dislocation pit density, and grain boundary length. (WHK)

  18. Development of impedance/external field potential dual measurement system for evaluation of electrophysiological properties of cells on microelectrodes

    NASA Astrophysics Data System (ADS)

    Nomura, Fumimasa; Matsuura, Kenji; Hattori, Akihiro; Odaka, Masao; Sugio, Yoshihiro; Kurotobi, Hiromi; Terazono, Hideyuki; Yasuda, Kenji

    2015-06-01

    A combination of extracellular field potential (FP) and impedance measurement technologies for multielectrode array (MEA) chip architecture is developed for the simultaneous evaluation of information on the i