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1

Thermal diffusivity of light-emitting diode packaging material determined by photoacoustic piezoelectric technique  

NASA Astrophysics Data System (ADS)

Thermal property is one of the most important properties of light-emitting diode (LED). Thermal property of LED packaging material determines the heat dissipations of the phosphor and the chip surface, accordingly having an influence on the light-emitting efficiency and the life-span of the device. In this paper, photoacoustic piezoelectric (PAPE) technique has been employed to investigate the thermal properties of polyvinyl alcohol (PVA) and silicon dioxide, which are the new and the traditional packaging materials in white LED, respectively. Firstly, the theory of PAPE technique has been developed for two-layer model in order to investigate soft materials; secondly, the experimental system has been set up and adjusted by measuring the reference sample; thirdly, the thermal diffusivities of PVA and silicon dioxide are measured and analysed. The experimental results show that PVA has a higher thermal diffusivity than silicon dioxide and is a better packaging material in the sense of thermal diffusivity for white LED.

Sun, Qi-Ming; Gao, Chun-Ming; Zhao, Bin-Xing; Rao, Hai-Bo

2010-11-01

2

Thermal Diffusivity of Reduced Activation Ferritic/Martensitic Steel Determined by the Time Domain Photoacoustic Piezoelectric Technique  

NASA Astrophysics Data System (ADS)

The thermal diffusivity of reduced activation ferritic/martensitic steel (CLF-1), which is recognized as the primary candidate structural material for the test blanket module of the international thermal-nuclear experimental reactor, has been studied by the time-domain (TD) photoacoustic piezoelectric (PAPE) technique. The TD PAPE model based on a simplified thermoelastic theory under square-wave modulated laser excitation is presented, relating the TD PAPE signal to the modulation frequency, thermal diffusivity, and other material parameters. Thermal diffusivities of reference samples such as copper and nickel were measured and analyzed, by which the validity of the technique is verified. The thermal diffusivity of the CLF-1 sample was measured to be 8.2 {mm}2{\\cdot }{s}^{-1} , which is at a medium level among the ordinary steel materials (3 {mm}2{\\cdot }{s}^{-1} to 14 {mm}2{\\cdot }{s}^{-1}) and has decent heat-dissipation ability. The results show that the TD PAPE technique can provide a fast and economic way for the investigation of the thermophysical properties of fusion reactor structural materials.

Zhao, Binxing; Wang, Yafei; Gao, Chunming; Sun, Qiming; Wang, Pinghuai

2014-07-01

3

Piezoelectric photoacoustic detection: Theory and experiment  

SciTech Connect

The theory of piezoelectric photoacoustic spectroscopy is developed for condensed-matter samples. Treating the sample as an elastic layer and neglecting the transducer's effect on the sample, the three-dimensional uncoupled quasistatic thermoelastic equations are solved using a Green's function for the stress. An expression for the dependence of the signal on absorption, modulation frequency, thermal properties, and mechanical properties of the sample is derived. The theoretical predictions are experimentally verified, the sources of noise are analyzed, and the noise equivalent power is estimated. Finally, considerations for detector optimization are discussed.

Jackson, W.; Amer, N.M.

1980-06-01

4

[Study of thermal diffusivity by piezoelectric photoacoustic phase].  

PubMed

Piezoelectric photoacoustic phase information can be applied to determine the thermal diffusivity of sample. In actual experiments, the results of phase versus modulation frequency deviate from the theory heavily because of the disturbance of instrumental contribution from the whole detecting system. Considering that the instrumental contribution of phase from PA cell can be ignored reasonably, there will be no additional phase contribution after the piezoelectric PA cell has been replaced by microphone PA cell while the other experimental conditions have been kept invariable. Based on this hypothesis, the conventional photoacoustic cell with microphone is employed to determine the instrumental contribution of whole detecting system by studying the PA phase of solid rare earth complexes. The instrumental contribution of phase was considered to be constant for that the same detecting system was used in both the microphone PA method and piezoelectric PA method. This method has been proved by detecting the thermal diffusivity of aluminium sample. The corrected results of experiments match the theory well, showing that the method of subtracting the instrumental contribution from the original experimental phase can be applied reasonably in relevant chopping frequency region. While in lower chopping frequency region, there will be a little deviation from the theoretical results. The method has been also employed to the photoacoustic detection of leaf, and the thermal diffusivity of leaf can be acquired by studying the piezoelectric photoacoustic phase. PMID:18051501

Hu, Bin; Chen, Da; Su, Qing-De

2007-09-01

5

Pulse shapes of nanosecond photoacoustic signals in liquids detected by piezoelectric foil  

SciTech Connect

A nonringing detection system based on 28-..mu..m-thick piezoelectric, poly(vinylidene difluoride) foil has been constructed for studying photoacoustic signals in liquids. Excellent agreement between theoretical and experimental photoacoustic pulse shapes has been observed. This system is well suited for monitoring radiationless relaxation processes in solutions on a nanosecond time scale.

Komorowski, S.J.; Eyring, E.M.

1987-10-01

6

Photoacoustic Signal Formation in Heterogeneous Multilayer Systems with Piezoelectric Detection  

NASA Astrophysics Data System (ADS)

A new efficient model describing photoacoustic (PA) signal formation with piezoelectric detection is reported. Multilayer sandwich-like systems: heterogeneous studied structure—buffer layer—piezoelectric transducers are considered. In these systems, the buffer layer is used for spatial redistribution of thermoelastic force moments generated in the investigated structure. Thus, mechanical properties of this layer play a crucial role to ensure perfect control of the detected voltage formed on a piezoelectric transducer by contribution of different regions of the studied structure. In particular, formation of the voltage signal strongly depends on the point at which the thermoelastic source is applied. Therefore, use of relatively simple linear Green's functions introduced in frames of the Kirchhoff-Love theory is chosen as an efficient approach for the PA signal description. Moreover, excellent agreement between the theoretical model and measured results obtained on a heterogeneous "porous silicon-bulk Si substrate" structure is stated. Furthermore, resolving of the inverse problem with fitting of the experimental curves by the developed model allows reliable evaluation of the thermal conductivity of the nanostructured porous silicon layer.

Isaiev, Mykola; Andrusenko, Dmytro; Tytarenko, Alona; Kuzmich, Andrey; Lysenko, Vladimir; Burbelo, Roman

2014-12-01

7

AlN-based piezoelectric micromachined ultrasonic transducer for photoacoustic imaging  

NASA Astrophysics Data System (ADS)

We report on the fabrication of a piezoelectric micromachined ultrasonic transducer (pMUT) and its application to photoacoustic imaging. With c-axis orientation, AlN was grown on a 300 nm-thick SiO2 film and a 200 nm-thick bottom electrode at room temperature. The device consists of SiO2, bottom electrode, AlN films, upper electrode, and polyimide protective layer. An area ratio of 0.45 was used between the upper electrode and the vibration area of the pMUT to provide an optimal sensitivity of transducer. Its resonant frequency was measured to be 2.885 MHz, and the coupling coefficient in the range of 2.38%-3.71%. The fabricated pMUT was integrated with a photoacoustic imaging system and photoacoustic image of a phantom was obtained. The resolution of the system was measured to be about 240 ?m.

Chen, Bingzhang; Chu, Futong; Liu, Xingzhao; Li, Yanrong; Rong, Jian; Jiang, Huabei

2013-07-01

8

Analog Front-End Circuitry in Piezoelectric and Microphone Detection of Photoacoustic Signals  

NASA Astrophysics Data System (ADS)

This paper is a review of analog front-end circuitry used in photoacoustic equipment with microphone or piezoelectric detection. A block structure of the front end as well as detailed circuit diagrams of preamplifiers dedicated for piezoelectric sensors and measurement condenser and electret microphones are described. The presented circuits are optimized toward low-noise operation. Practical remarks regarding the design of the remaining analog blocks are also given. The analysis shows that it is possible to design an analog front end for which specifications will be comparable with the best commercial solutions.

Starecki, Tomasz

2014-11-01

9

Photoacoustic technique applied to the study of skin and leather  

NASA Astrophysics Data System (ADS)

In this paper the photoacoustic technique is used in bull skin for the determination of thermal and optical properties as a function of the tanning process steps. Our results show that the photoacoustic technique is sensitive to the study of physical changes in this kind of material due to the tanning process.

Vargas, M.; Varela, J.; Hernández, L.; González, A.

1998-08-01

10

Photoacoustic measurement technique using acoustic phase perturbation  

SciTech Connect

A novel photoacoustic measurement technique is introduced, which is based on the phase perturbation of an external acoustic wave that propagates through a region of material irradiated by an optical beam. The mechanism of the perturbation is the local change in acoustic velocity due to heating of the irradiated sample. Because the acoustic phase perturbation may be calibrated directly, it is found that the absolute optical absorption coefficient of the irradiated sample may be determined using the technique. Both the experimental phase detection system and a theoretical analysis of the acoustic perturbation are discussed. Finally, an experiment is described in detail, where the measurement technique is used to determine the absolute optical absorption coefficient of a liquid.

Stearns, R.G.

1988-02-01

11

Skin absorption studied by photoacoustic techniques  

NASA Astrophysics Data System (ADS)

In this work we propose for the particular problem of penetration of substance into skin, a setup which is based on the conventional photoacoustic cell. In order to avoid some problems, intrinsic to the material under study and the sensibility of the technique, we use the thermal effusivity of the skin-substance system to monitor this phenomenon, in vivo and in situ. We measure the changes of thermal effusivity due to the absorption of some topical medicaments. These values are compared with those from an adjacent sample of clean skin (without medicament, natural fats or transpiration). This experiment was performed on a volunteer in different parts of the human skin. We use stainless steel (250 mm thickness) as the thermally thin light absorbance surface. The values for this parameter are in agreement with some reported in the literature. Besides the measurements described above.

Vargas-Luna, M.; Córdova-Fraga, T.; Varela-Nájera, J. B.; Gutiérrez-Juárez, G.

2000-10-01

12

Normalized photoacoustic techniques for thermal diffusivity measurements of buried layers in multilayered systems  

E-print Network

the theoretical photoacoustic signal from the three layers with the corresponding signal from the uppermost twoNormalized photoacoustic techniques for thermal diffusivity measurements of buried layers for the implementation of normalized depth-profilometric photoacoustic methodologies involving the open photoacoustic

Mandelis, Andreas

13

A preliminary measurement of fibres and fines in pulp suspensions by the scattering photoacoustic technique  

NASA Astrophysics Data System (ADS)

The consistency of fibres and concentration of fines need to be controlled during the production process in the paper industry. In paper pulp, fibre lengths range from less than a millimetre to several millimetres whereas fines particles have sizes of a few tens of micrometres. Therefore, the two fractions have different properties of optical scattering and acoustic attenuation, i.e., fibres produce more forward optical scattering and acoustic attenuation, while fines produce larger and more homogeneous scattering but less acoustic attenuation. Based on these facts, we specifically develop a new method, a scattering photoacoustic technique, to measure the consistency of fibres and concentration of fines simultaneously. It employs near-infrared light (1064 nm wavelength) to produce three acoustic waves with MHz frequencies. One piezoelectric transducer detects these waves, which are used to measure optical scattering and acoustic attenuation of pulp samples. The results indicate that our current apparatus successfully discerned the pure fibre and fines samples. It also proved capable of extracting the consistencies of fines and fibres in the studied samples that consisted of mixtures of fibre and fines. Finally, the scattering photoacoustic technique has a potential ability in online measurement of fibre and fines consistencies in pulp suspensions.

Zhao, Z.; Törmänen, M.; Myllylä, R.

2006-01-01

14

Percutaneous permeation measurement of topical phthalocyanine by photoacoustic technique  

NASA Astrophysics Data System (ADS)

This investigation have studied photoacoustic (PA) technique to percutaneous permeation of topical hydroxy-(29H,31H-phthalocyaninate) aluminum (PcAlOH) on pig ear skin. The PcAlOH was incorporated in an emulsion (O/W) (1 mg/dl) with assessed stability parameters of: pH, short and long term stability tests (in the several conditions). The skin was prepared through a heat separation technique, and with a scalpel, the outer skin of the cartilage was removed. The skins were then cut into 4 cm2 pieces and treated with sodium bromide 2 mol/L for 6 h at 37 °C. The epidermis layer was washed with purified water, dried, and stored under reduced pressure until use. The skin permeation kinetics was determined by photoacoustic technique in an open photoacoustic cell. Short (after preparation) and long-term stability tests showed no phase separation. The emulsion developed pH 7.6 and after incorporating the pH was unchanged. The typical times for percutaneous permeation of the emulsion base and emulsion + PcAlOH were 182 (±6) and 438 (±3) s, respectively. This study indicated that the formulations containing PcAlOH have stabile characteristics and show promising results in absorption into the skin. The presence of the photosensitive agent in the formulation contributed significantly to the greater absorption time than observed in the base formulation. The used photoacoustic technical to examine the penetration kinetics of PcAlOH in pig ear skin was adequate and may be employed in the determination of the percutaneous permeation of phthalocyanines.

Silva, Emanoel P. O.; Barja, Paulo R.; Cardoso, Luiz E.; Beltrame, Milton

2012-11-01

15

Photoacoustic correlation technique for low-speed flow measurement.  

PubMed

A photoacoustic correlation spectroscopy (PACS) technique was proposed for the first time. This technique is inspired by its optical counterpart-the fluorescence correlation spectroscopy (FCS), which is widely used in the characterization of the dynamics of fluorescent species. The fluorescence intensity is measured in FCS while the acoustic signals are detected in PACS. To proof of concept, we demonstrated the flow measurement of light-absorbing beads probed by a pulsed laser. A PACS system with temporal resolution of 0.8 sec was built. Polymer microring resonators were used to detect the photoacoustic signals, which were then signal processed and used to obtain the autocorrelation curves. Flow speeds ranging from 249 to 15.1 ?m/s with corresponding flow time from 4.42 to 72.5 sec were measured. The capability of low-speed flow measurement can potentially be used for detecting blood flow in relatively deep capillaries in biological tissues. Moreover, similar to FCS, PACS may have many potential applications in studying the dynamics of photoacoustic beads. PMID:20689645

Chen, Sung-Liang; Ling, Tao; Huang, Sheng-Wen; Baac, Hyoung Won; Chang, Yu-Chung; Guo, L Jay

2010-02-11

16

Study of photoacoustic techniques for detection of mercaptans  

SciTech Connect

Studies were performed utilizing photoacoustic techniques for the quantitative detection of mercaptans in natural gas. An experimental spectrophone was designed and constructed. Its performance was analyzed using samples of methane gas containing differing concentrations of normal propyl mercaptan, one of the odorants commonly injected into natural gas. The spectrophone performed the necessary analyses and reported the concentration of mercaptans present in the gas samples. The test obtained from the spectrophone closely followed the theoretical response curve. The decrease in signal voltage was determined to be directly proportional to the decrease in mercaptan concentration. The lowest concentration of mercaptan analyzed by the spectrophone was approximately 25% of the typical concentration level of mercaptan occurring in odorized natural gas. Thus, the studies indicated the analytical range of the spectrophone was sufficient to allow the instrument to be utilized ion performing quantitative analyses of mercaptans in natural gas.

Overbey, R.L.

1986-01-01

17

Photoacoustic frequency transmission technique: Electronic deformation mechanism in semiconductors  

Microsoft Academic Search

A quantitative analysis of the electronic deformation (electronic strain) contribution to the photoacoustic signal in semiconductor samples was done. The photoacoustic (PA) effect was investigated as a function of the modulation frequency in a transmission detection configuration. The theoretical model for this configuration was given for the thermal and elastic processes besides the carrier transport characteristic and the relation for

D. M. Todorovic; P. M. Nikolic; A. I. Bojicic

1999-01-01

18

Recovery of the Elastic Constants from Wavespeed Measurements in Viscoelastic Composites by Photoacoustic Technique  

NASA Astrophysics Data System (ADS)

Mixtures of black rubber (natural rubber) vulcanizates containing various concentrations of sand particles, as hard fillers, were prepared to determine their elastic constants at low and high frequency using the photoacoustic technique. These parameters are related with the degree of sand filler dispersion which determines the changes in stiffness, as well as its potential as reinforcement material for treads in tires. The constants are recovered through measurements of the longitudinal wave and complemented with the predictions from the Kerner model to obtain the Poisson’s ratio. Some results are corroborated with tension and compression tests. The acoustic waves are acquired by two piezoelectric transducers, one centered at 3 kHz and the other at 240 kHz. The results show a slight increase in Young’s modulus at low frequencies; meanwhile at high frequencies, it increases by two orders of magnitude. In addition, we found that on adding small amounts of prepared sand, the stiffness increases and this is particularly convenient to reduce the energy losses by the rolling resistance in automotive vehicles.

Navarrete, M.; Mejía-Uriarte, E. V.; Villagrán-Muniz, M.

2013-09-01

19

Nonlinear photoacoustic microscopy via a loss modulation technique: from detection to imaging.  

PubMed

In order to achieve high-resolution deep-tissue imaging, multi-photon fluorescence microscopy and photoacoustic tomography had been proposed in the past two decades. However, combining the advantages of these two imaging systems to achieve optical-spatial resolution with an ultrasonic-penetration depth is still a field with challenges. In this paper, we investigate the detection of the two-photon photoacoustic ultrasound, and first demonstrate background-free two-photon photoacoustic imaging in a phantom sample. To generate the background-free two-photon photoacoustic signals, we used a high-repetition rate femtosecond laser to induce narrowband excitation. Combining a loss modulation technique, we successfully created a beating on the light intensity, which not only provides pure sinusoidal modulation, but also ensures the spectrum sensitivity and frequency selectivity. By using the lock-in detection, the power dependency experiment validates our methodology to frequency-select the source of the nonlinearity. This ensures our capability of measuring the background-free two-photon photoacoustic waves by detecting the 2nd order beating signal directly. Furthermore, by mixing the nanoparticles and fluorescence dyes as contrast agents, the two-photon photoacoustic signal was found to be enhanced and detected. In the end, we demonstrate subsurface two-photon photoacoustic bio-imaging based on the optical scanning mechanism inside phantom samples. PMID:24515013

Lai, Yu-Hung; Lee, Szu-Yu; Chang, Chieh-Feng; Cheng, Yu-Hsiang; Sun, Chi-Kuang

2014-01-13

20

Piezoelectric cantilevers energy harvesting in MEMS technique  

NASA Astrophysics Data System (ADS)

Piezoelectric cantilevers energy harvesting made by micro-electromechanical system (MEMS) technology can scavenge power from low-level ambient vibration sources. The developed cantilevers energy harvesting are featured with resonate frequency and power output in microwatt level, which is sufficient to the self-supportive sensors for in-service integrity monitoring of large social and environmental infrastructures at remote locations. In this paper, piezoelectric energy harvesting based on thick-film piezoelectric cantilevers is investigated to resonate at specific frequencies of an external vibration energy source, which creating electrical energy via the piezoelectric effect. Our cantilever device has a multiple structure with a proof mass added to the end. The thick film lead zirconate titanate Pb(Zr,Ti)O3 (PZT) coated on the top of Au/Cr/SiO2/Si substrates by sol-gel-spin method. The thickness of the PZT membrane was up to 2?m and the cantilevers substrates thickness 50?m, wideness 1.5mm, length 4mm. The Au/Ti top electrode is patterned on top of the sol-gel-spin coated PZT thick film in order to employ the d31 mode. The prototype energy generator has a measured performance of 0.74?W effective electrical power, and 4.93 DC output voltages to resistance load. The effect of proof mass, beam shape and damping on the power generating performance are modeled to provide a design guideline for maximum power harvesting from environmentally available low frequency vibrations. A multiple structure cantilever is designed to achieve compactness, low resonant frequency and minimum damping coefficient, simultaneously. This device is promising to support networks of ultra-low-power sensor.

Shang, Yingqi; Qiu, Chengjun; Liu, Hongmei; Chen, Xiaojie; Qu, Wei; Dou, Yanwei

2011-11-01

21

Piezoelectric cantilevers energy harvesting in MEMS technique  

NASA Astrophysics Data System (ADS)

Piezoelectric cantilevers energy harvesting made by micro-electromechanical system (MEMS) technology can scavenge power from low-level ambient vibration sources. The developed cantilevers energy harvesting are featured with resonate frequency and power output in microwatt level, which is sufficient to the self-supportive sensors for in-service integrity monitoring of large social and environmental infrastructures at remote locations. In this paper, piezoelectric energy harvesting based on thick-film piezoelectric cantilevers is investigated to resonate at specific frequencies of an external vibration energy source, which creating electrical energy via the piezoelectric effect. Our cantilever device has a multiple structure with a proof mass added to the end. The thick film lead zirconate titanate Pb(Zr,Ti)O3 (PZT) coated on the top of Au/Cr/SiO2/Si substrates by sol-gel-spin method. The thickness of the PZT membrane was up to 2?m and the cantilevers substrates thickness 50?m, wideness 1.5mm, length 4mm. The Au/Ti top electrode is patterned on top of the sol-gel-spin coated PZT thick film in order to employ the d31 mode. The prototype energy generator has a measured performance of 0.74?W effective electrical power, and 4.93 DC output voltages to resistance load. The effect of proof mass, beam shape and damping on the power generating performance are modeled to provide a design guideline for maximum power harvesting from environmentally available low frequency vibrations. A multiple structure cantilever is designed to achieve compactness, low resonant frequency and minimum damping coefficient, simultaneously. This device is promising to support networks of ultra-low-power sensor.

Shang, Yingqi; Qiu, Chengjun; Liu, Hongmei; Chen, Xiaojie; Qu, Wei; Dou, Yanwei

2012-04-01

22

Applications of photoacoustic techniques to the study of jet fuel residue  

NASA Technical Reports Server (NTRS)

It has been known for many years that fuels for jet aircraft engines demonstrate thermal instability. One manifestation of this thermal instability is the formation of deleterious fuel-derived thermally-induced deposits on surfaces of the aircraft's fuel-handling system. The results of an investigation of the feasibility of applying photoacoustic techniques to the study of the physical properties of these thermal deposits are presented. Both phase imaging and magnitude imaging and spectroscopy were investigated. It is concluded that the use of photoacoustic techniques in the study of films of the type encountered in this investigation is not practical.

Claspy, P. C.

1983-01-01

23

Piezoelectric energy harvesting using a series synchronized switch technique  

NASA Astrophysics Data System (ADS)

An alternative switching technique for piezoelectric energy harvesting is presented. The energy harvester based on piezoelectric elements is a promising method to scavenge ambient energy. Several non-linear techniques such as SSHI have been implemented to improve the global harvested energy. However, these techniques are sensitive to load and should be tuned to obtain optimal power output. This technique, called Series Synchronized Switch Harvesting (S3H), has both the advantage of easy implementation and independence of the harvested power with the load impedance. The harvesting circuit simply consists of a switch in series with the piezoelement and the load. The switch is nearly always open and is triggered-on each time the piezoelectric voltage reaches an extremum. It is opened back after an arbitrary on-time t0. The energy scavenging process happens when switch is closed. Based on linear motion assumption, the harvester structure is modeled as a "Mass-Spring-Damper" system. The analysis of S3H technique is considered with harmonic excitation. An analytical model of S3H is presented and discussed. The main advantage of this approach compared with the usual standard technique is that the extracted power is independent of the load within a wide range of load impedance, and that the useful impedance range is simply related to the defined switch on-time. For constant displacement excitation condition, the optimal power output is more than twice the power extracted by the standard technique as long as the on-time interval is small comparatively with the vibration period. For constant force excitation, an optimal on-time can be defined resulting in an optimally wide load bandwidth. Keywords: piezoelectric; energy harvesting; non-linear harvesting techniques; switching techniques.

Li, Yang; Lallart, Mickaël.; Richard, Claude

2014-04-01

24

Resonance frequencies and Young's modulus determination of magnetorheological elastomers using the photoacoustic technique  

NASA Astrophysics Data System (ADS)

A simple and reliable methodology for determining the Young's modulus of magnetorheological elastomers is proposed based on the resonance frequencies of the amplitude of the photoacoustic signal. An explicit expression for the pressure changes within a photoacoustic cell, due to the thermal expansion of the air and the elastic bending of a clamped circular elastic membrane, is derived and analyzed. It is found that the resonance behavior of the amplitude of the photoacoustic signal is due to the contribution of the axial bending of its thickness. It is also shown that the Young's modulus of the membrane is proportional to its density, the square of its resonance frequencies and the fourth power of its radius, and inversely proportional to the square of its thickness. The application of the proposed approach to membranes made up of spherical microparticles of carbonyl iron powder embedded in a matrix of silicone rubber with weight concentrations of 0%, 5.2%, and 13.7% yields accurate and reproducible results, which are in good agreement with reported data in the literature. The highest accuracy on the measurement of the resonance frequencies and therefore on the Young's modulus is found for the first resonance peak. When a magnetic field is applied to the samples to modify their stiffness, it is observed that the Young's modulus increases with the magnetic field. This novel application of the photoacoustic technique opens the possibility of performing mechanical characterization of a broad diversity of magnetorheological membranes.

Daniel Macias, J.; Ordonez-Miranda, J.; Alvarado-Gil, J. J.

2012-12-01

25

Photoacoustic effect in stressed elastic solids  

Microsoft Academic Search

A multimode approach based on the simultaneous application of several photothermal and photoacoustic methods is proposed for the study of thermal and thermoelastic effects in solids with residual stress. It includes photoacoustic gas microphone, photodeflection, photoreflectance and photoacoustic piezoelectric microscopy methods. This approach provides complementary information about thermal, elastic and thermoelastic properties of samples with residual stress. Some experimental results

K. L. Muratikov; A. L. Glazov; D. N. Rose; J. E. Dumar

2000-01-01

26

Real-Time Photoacoustic Microscopy  

Microsoft Academic Search

In this thesis we developed a new real-time photoacoustic microscopy theory for detecting subsurface defects in opaque solid samples. The theory is verified by experiment and applied to a gas-microphone photoacoustic microscope. A line scan image can be achieved in tens of hundreds milliseconds in contrast to several minutes in conventional photoacoustic microscopy. This new technique differs from conventional photoacoustic

Zhi-Ming Liu

1987-01-01

27

Parametric studies on the harvested energy of piezoelectric switching techniques  

NASA Astrophysics Data System (ADS)

Piezoelectric energy harvesting techniques have experienced increasing research effort during the last few years. Possible applications including wireless, fully autonomous electronic devices, such as sensors, have attracted great interest. The key aspect of harvesting techniques is the amount of converted and stored energy, because the energy source and the conversion rate is limited. In particular, switching techniques offer many parameters that can be optimized. It is therefore crucial to examine the influence of these parameters in a precise manner. This paper addresses an accurate analytical modeling approach, facilitating the calculation of standard-DC and parallel SSHI-DC energy harvesting circuits. In particular the influence of the frequency ratio between the excitation and the electrical resonance of the switching LR-branch, and the voltage gaps across the rectifier diodes are studied in detail. Additionally a comparison with the SSDI damping network is performed. The relationship between energy harvesting and damping is indicated in this paper.

Neubauer, M.; Krack, M.; Wallaschek, J.

2010-02-01

28

Improved piezoelectric switch shunt damping technique using negative capacitance  

NASA Astrophysics Data System (ADS)

This paper proposes an adaptive shunt damping circuit for improved damping performance. It consists of a switched inductance-resistance network (SSDI), which is connected in parallel to a negative capacitance. This circuit is in the following called 'synchronized switching damping on negative capacitor and inductor' (SSDNCI). It combines the adaptive nature of the SSDI technique and the improved performance of a negative capacitance. By the action of the switch device, the piezoelectric element is periodically held under both states of the nonlinear shunt and therefore adapts to the frequency of excitation. The analysis in this publication is performed based on the typical assumptions of a single degree-of-freedom oscillator. The stationary charge signal and energy dissipation are derived as functions of the ratio between the negative capacitance and piezoelectric capacitance. Calculation results show that the dissipated energy grows with the negative capacitance up to the stability boundary of the system. Measurements are conducted on a clamped beam test rig to validate the theoretical results. In the operative range of the negative capacitance which is used in this research, an increase in nearly 220% in energy dissipation compared to the standard SSDI technique is achieved.

Han, Xu; Neubauer, Marcus; Wallaschek, Jörg

2013-01-01

29

Identification of Plant Growth-Promoting Bacteria Using Titanium Dioxide Photocatalysis-Assisted Photoacoustic Technique  

NASA Astrophysics Data System (ADS)

The effect of titanium dioxide photocatalysis against bacteria that are dangerous for human health has been investigated in the past, suggesting the possibility of using a specific behavior for each microorganism during this process for its discrimination. In this study, the behavior of some plants’ growth promoting bacteria ( Burkholderia unamae (Strain MTI 641), Acetobacter diazotrophicus (Strain PAl 5T), A. diazotrophicus (Strain CFN-Cf 52), and B. unamae (Strain TATl-371)) interacting with light and bactericidal titanium dioxide films have been analyzed using the photoacoustic technique. The monitoring of these interactions shows particular characteristics that could serve for identifying these species.

Gordillo-Delgado, F.; Marín, E.; Calderón, A.

2013-09-01

30

Study on Photoacoustic Measurement Technique of Thermophysical Properties of Thick Solid Material and Human Skin  

NASA Astrophysics Data System (ADS)

The thermal effusivity and thermal diffusivity of thick solid materials were measured to validate a developed technique using a photoacoustic method. First, the thermal effusivity was determined by making close contact between an optically opaque sheet and the material. A titanium plate was used as the sheet with known thermophysical properties. Second, using the thermal effusivity as a known value, the thermal diffusivity was also determined by making close contact between an optically semitransparent sheet and the material. A rigid polyvinyl chloride plate was used as the thin sheet with known thermophysical and radiative properties, and a natural rubber block and an epoxy resin block were adopted as samples. The results indicated that the present technique was sufficiently accurate. The thermal effusivity and then the thermal diffusivity of human skin in vivo were measured noninvasively in the same way instead of the solid materials. The results also indicated that the present technique was sufficiently accurate for human skin.

Yoshida, Atsumasa; Imuta, Azusa; Yamada, Tetsuya; Kagata, Kakeru

2014-12-01

31

Benefits of the Mycorrhizal Fungi in Tomato Leaves Measured by Open Photoacoustic Cell Technique: Interpretation of the Diffusion Parameters  

NASA Astrophysics Data System (ADS)

The open photoacoustic cell technique was used to measure tomato leaves from plants with and without mycorrhizal fungi ( Glomus fasciculatum). Based on measurement of the photobaric contribution of the photoacoustic signal, the exponential parameter of the diffusion behavior for this contribution was calculated. From this value, the oxygen diffusion coefficient was derived. The changes in the oxygen- diffusion-coefficient-dependent exponential parameter are statistically significant ( p < 0.05) and are consistent with the expected benefits of mycorrhizal symbiosis. Potentially similar results obtained from the photothermal contribution are discussed.

Sánchez-Rocha, S.; Vargas-Luna, M.; Gutiérrez-Juárez, G.; Huerta-Franco, R.; Olalde-Portugal, V.

2008-12-01

32

Measurement of the Auger lifetime in GaInAsSb/GaSb heterostructures using the photoacoustic technique  

SciTech Connect

We have studied Ga{sub x}In{sub 1-x}As{sub y}Sb{sub 1-y}/GaSb heterostructures for x=0.84 and y=0.14 using the photoacoustic technique with the heat transmission configuration. A theoretical model, which includes all the possible nonradiative recombination mechanisms that contribute to heat generation, was developed to calculate the photoacoustic signal for this type of heterostructure. The Auger recombination lifetime {tau}{sub Auger} was determined by fitting our experimental results to the calculated frequency dependence of the theoretical photoacoustic signal. The obtained value for {tau}{sub Auger} is compatible with those reported in the literature for semiconductors with band-gap energies below and above 0.5 eV, the energy region where there is a lack of experimental {tau}{sub Auger} values. {copyright} 2001 American Institute of Physics.

Riech, I.; Gomez-Herrera, M. L.; Diaz, P.; Mendoza-Alvarez, J. G.; Herrera-Perez, J. L.; Marin, E.

2001-08-13

33

Analysis of Maize Seed Germs by Photoacoustic Microscopy and Photopyroelectric Technique  

NASA Astrophysics Data System (ADS)

A knowledge about thermal parameters of structural components of maize seed is of great relevance in the seed technology practice. The objective of the present study was to determine the thermal effusivity of germs of maize ( Zea mays L.) of different genotypes by means of the photopyroelectric technique (PPE) in the inverse configuration and obtaining the thermal imaging of these samples by photoacoustic microscopy (PAM). Germs from crystalline maize (white pigment), semi-crystalline maize (yellow pigment), and floury maize (blue pigment) were used in this investigation. The results show differences between germs of maize seeds mainly in the values of their thermal effusivities. The thermal images showed minimum inhomogeneity of these seed germs. Characterizations of thermal parameters in seeds are important in agriculture and food production and could be particularly useful to define their quality and determine their utility. PPE and PAM can be considered as potential diagnostic tools for the characterization of agriculture seeds.

Pacheco, A. Domínguez; Aguilar, C. Hernández; Cruz-Orea, A.

2013-05-01

34

Analysis of Piezoelectric Structural Sensors with Emergent Computing Techniques  

NASA Technical Reports Server (NTRS)

The purpose of this project was to try to interpret the results of some tests that were performed earlier this year and to demonstrate a possible use of emergence in computing to solve IVHM problems. The test data used was collected with piezoelectric sensors to detect mechanical changes in structures. This project team was included of Dr. Doug Ramers and Dr. Abdul Jallob of the Summer Faculty Fellowship Program, Arnaldo Colon-Lopez - a student intern from the University of Puerto Rico of Turabo, and John Lassister and Bob Engberg of the Structural and Dynamics Test Group. The tests were performed by Bob Engberg to compare the performance two types of piezoelectric (piezo) sensors, Pb(Zr(sub 1-1)Ti(sub x))O3, which we will label PZT, and Pb(Zn(sub 1/3)Nb(sub 2/3))O3-PbTiO, which we will label SCP. The tests were conducted under varying temperature and pressure conditions. One set of tests was done by varying water pressure inside an aluminum liner covered with carbon-fiber composite layers (a cylindrical "bottle" with domed ends) and the other by varying temperatures down to cryogenic levels on some specially prepared composite panels. This report discusses the data from the pressure study. The study of the temperature results was not completed in time for this report. The particular sensing done with these piezo sensors is accomplished by the sensor generating an controlled vibration that is transmitted into the structure to which the sensor is attached, and the same sensor then responding to the induced vibration of the structure. There is a relationship between the mechanical impedance of the structure and the resulting electrical impedance produced in the in the piezo sensor. The impedance is also a function of the excitation frequency. Changes in the real part of impendance signature relative to an original reference signature indicate a change in the coupled structure that could be the results of damage or strain. The water pressure tests were conducted by pressurizing the bottle on a test stand, and running sweeps of excitations frequencies for each of the piezo sensors and recording the resulting impedance. The sweeps were limited to 401 points by the available analyzer, and it was decided to perform individual sweeps at five different excitation frequency ranges. The frequency ranges used for the PZTs were different in two of the five ranges from the ranges used for the SCP. The bottles were pressurized to empty (no water), 0psig, 77 psig, 155 psig, 227 psig in nearly uniform increments of about 77psi. One of each of the two types of piezo sensors was fastened on to the bottle surface at two locations: about midway between the ends on cylindrical portion of the bottle and at the very edge of one of the end domes. The data was collected in files by sensor type (2 cases), by location (2 cases), by frequency range (5 cases), and pressure (5cases) to produce 100 data sets of 401 impedances. After familiarization with the piezo sensing technology and obtaining the data, the team developed a set of questions to try to answer regarding the data and made assignments of responsibilities. The next section lists the questions, and the remainder of the report describes the data analysis work performed by Dr. Ramers. This includes a discussion of the data, the approach to answering the question using statistical techniques, the use of an emergent system to investigate the data where statistical techniques were not usable, conclusions regarding the data, and recommendations.

Ramers, Douglas L.

2005-01-01

35

Photoacoustics of the stressed state in solids  

Microsoft Academic Search

The modern experimental and theoretical states of the problem of residual stress detection by the photoacoustic method are analyzed. Some experimental results obtained by the photoacoustic method for Vickers indentation zones in silicon nitride and Al2O3-SiC-TiC ceramics are presented. The effect of annealing on the photoacoustic piezoelectric signal for the Al2O3-SiC-TiC ceramic and the influence of the given external loading

K. L. Muratikov; A. L. Glazov; D. N. Rose; J. E. Dumar

2003-01-01

36

Photoacoustics of the stressed state in solids  

Microsoft Academic Search

The modern experimental and theoretical states of the problem of residual stress detection by the photoacoustic method are analyzed. Some experimental results obtained by the photoacoustic method for Vickers indentation zones in silicon nitride and Al2O3–SiC–TiC ceramics are presented. The effect of annealing on the photoacoustic piezoelectric signal for the Al2O3–SiC–TiC ceramic and the influence of the given external loading

K. L. Muratikov; A. L. Glazov; D. N. Rose; J. E. Dumar

2003-01-01

37

Laser photoacoustic microscopy of solids with residual stresses  

Microsoft Academic Search

The results of scanning photodeflection and photoacoustic piezoelectric imaging of the Vickers indentation on Al2O3-SiC-TiC ceramic composite are presented. It is demonstrated that external loading influences on the photoacoustic signal behavior near the radial crack tips. The theoretical model of the photoacoustic signal behavior near radial cracks under external loading is proposed. It is shown that the photoacoustic signal modifications

Kyrill L. Muratikov; Alexej L. Glazov

2003-01-01

38

Dynamics of Acetaldehyde Production during Anoxia and Post-Anoxia in Red Bell Pepper Studied by Photoacoustic Techniques  

Microsoft Academic Search

Acetaldehyde (AA), ethanol, and CO, production in red bell pepper (Capsicum annum 1.) fruit has been measured in a contin- uou~ flow system as the fruit was switched between 20% O, and anaerobic conditions. Minimum gas phase concentrations of 0.5 nL L-l, 10 nL 1-', and 1 mL L-', respectively, can be detected em- ploying a laser-based photoacoustic technique. This

Hanna Zuckermann; Frans J. M. Harren; Joerg Reuss; David H. Parker

39

A new fabrication method for microactuators with piezoelectric thin film using precision cutting technique  

Microsoft Academic Search

A new fabrication method for microactuators and microstructures is presented. It is based on a precision cutting technique and hydrothermal method to make piezoelectric thin film. It is generally considered that the cutting technique is not suitable for microparts fabrication because the cutting force is too large compared to the size of the structure. The authors have used a four

Y. Yamagata; S. Mihara; N. Nishioki; T. Higuchi

1996-01-01

40

In vivo measurement of human skin absorption of topically applied substances by a photoacoustic technique.  

PubMed

A photoacoustic technique is used for studying topically applied substance absorption in human skin. The proposed method utilizes a double-chamber PA cell. The absorption determination was obtained through the measurement of the thermal effusivity of the binary system substance-skin. The theoretical model assumes that the effective thermal effusivity of the binary system corresponds to that of a two-phase system. Experimental applications of the method employed different substances of topical application in different parts of the body of a volunteer. The method is demonstrated to be an easily used non-invasive technique for dermatology research. The relative concentrations as a function of time of substances such as ketoconazol and sunscreen were determined by fitting a sigmoidal function to the data, while an exponential function corresponds to the best fit for the set of data for nitrofurazona, vaseline and vaporub. The time constants associated with the rates of absorption, were found to vary in the range between 10 and 58 min, depending on the substance and the part of the body. PMID:12214760

Gutiérrez-Juárez, G; Vargas-Luna, M; Córdova, T; Varela, J B; Bernal-Alvarado, J J; Sosa, M

2002-08-01

41

Normalized photoacoustic techniques for thermal diffusivity measurements of buried layers in multilayered systems  

Microsoft Academic Search

The one-dimensional heat diffusion problem for a three-layer system is solved assuming the surface absorption model. The analytical solution is shown to be suitable for the implementation of normalized depth-profilometric photoacoustic methodologies involving the open photoacoustic-cell configuration for thermal diffusivity measurements in buried underlayers within a three-layer stack. Our normalization procedures eliminate the frequency-dependent instrumental electronic contribution (transfer function) and

J. A. Balderas-Lopez; A. Mandelis; J. A. Garcia

2002-01-01

42

Multi-contrast Photoacoustic Microscopy  

NASA Astrophysics Data System (ADS)

Photoacoustic microscopy is a hybrid imaging modality with high spatial resolution, moderate imaging depth, excellent imaging contrast and functional imaging capability. Taking full advantage of this powerful weapon, we have investigated different anatomical, functional, flow dynamic and metabolic parameter measurements using photoacoustic microscopy. Specifically, Evans-blue dye was used to enhance photoacoustic microscopy of capillaries; label-free transverse and axial blood flow was measured based on bandwidth broadening and time shift of the photoacoustic signals; metabolic rate of oxygen was quantified in vivo from all the five parameters measured by photoacoustic microcopy; whole cross-sectional imaging of small intestine was achieved on a double-illumination photoacoustic microscopy with extended depth of focus and imaging depth; hemodynamic imaging was performed on a MEMS-mirror enhanced photoacoustic microscopy with a cross-sectional imaging rate of 400 Hz. As a maturing imaging technique, PAM is expected to find new applications in both fundamental life science and clinical practice.

Yao, Junjie

43

Analytical and experimental investigation of the frequency ratio and switching law for piezoelectric switching techniques  

NASA Astrophysics Data System (ADS)

Piezoelectric shunt damping with mechanical structures has been an active research topic for several years. Standard passive techniques suffer from a very limited and frequency-dependent damping performance. Recently, semi-active switching techniques—namely SSDI (synchronized switch damping on inductor) and SSDV (synchronized switch damping on voltage source) techniques—have been proposed, which are capable of adapting to variations of the excitation frequency without reduction in performance. Crucial for the damping performance is the tuning of the shunt parameters and the precise switching sequence. In this paper, an analytical analysis of the switching technique is presented, which includes the influence of all shunt parameters and the switching times. New results concerning the optimal tuning of the inductance and the switching sequence are obtained, and it is shown that the enhanced SSDV technique can be equated with the SSDI technique, albeit with an increased effective piezoelectric force factor. Measurements are conducted to validate the theoretical results.

Neubauer, M.; Wallaschek, J.

2008-06-01

44

Analytical and experimental investigation of the frequency ratio and switching law for piezoelectric switching techniques  

Microsoft Academic Search

Piezoelectric shunt damping with mechanical structures has been an active research topic for several years. Standard passive techniques suffer from a very limited and frequency-dependent damping performance. Recently, semi-active switching techniques---namely SSDI (synchronized switch damping on inductor) and SSDV (synchronized switch damping on voltage source) techniques---have been proposed, which are capable of adapting to variations of the excitation frequency without

M. Neubauer; J. Wallaschek

2008-01-01

45

Photoacoustic Measurements in Brain Tissue  

SciTech Connect

In this work, we develop and evaluate the photoacoustic technique for recording spectra of white and gray mammalian brain tissues. In addition to the experimental work, we also discuss the geometric aspects of photoacoustic signal generation using collimated light. Spectra constructed from the peak-to-peak amplitude of the photoacoustic waveforms indicate differences in the two tissue types at wavelengths between 620 and 695 nm. The potential of the technique for non-invasive diagnosis is discussed.

Kasili, P.M.; Mobley, J.; Vo-Dinh, T.

1999-09-19

46

Effect of boundary (support) conditions on piezoelectric damping in the case of SSDI vibration control technique  

NASA Astrophysics Data System (ADS)

Piezoelectric transducers in conjunction with appropriate electric networks can be used as a mechanical energy dissipation device. If a piezoelectric element is attached to a structure, it is strained as the structure deforms and converts a portion of the vibration energy into electrical energy that can be dissipated through a shunt network in the form of heating. These vibration control devices experienced a great development in recent years, due to their performances and advantages compared with active techniques. One of them is the synchronized switch damping (SSD) and derived techniques, which were developed in the field of piezoelectric damping, and which lead to a very good trade-off between the simplicity, the required power supply and their performances. This technique consists in a non-linear processing of the piezoelectric voltage, which induces an increase in electromechanical energy conversion. The control law consists in triggering the inverting switch on each extremum of voltage (or displacement). In this study, the proposed method for the switching sequence is based on the statistical evaluation of structural deflection. The purpose of this paper is to present an experimental study of the synchronized switch damping on inductance (SSDI) control technique sensitivity to the system boundary conditions. It is observed that the fundamental natural frequency greatly depends on these conditions. The effect of these constraints is distributed all over the system and significantly affects the results.

Guyomar, D.; Mohammadi, S.; Richard, C.

2009-02-01

47

A photoacoustic technique applied to detection of ethylene emissions in edible coated passion fruit  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy was applied to study the physiological behavior of passion fruit when coated with edible films. The results have shown a reduction of the ethylene emission rate. Weight loss monitoring has not shown any significant differences between the coated and uncoated passion fruit. On the other hand, slower color changes of coated samples suggest a slowdown of the ripening process in coated passion fruit.

Alves, G. V. L.; dos Santos, W. C.; Waldman, W. R.; Oliveira, J. G.; Vargas, H.; da Silva, M. G.

2010-03-01

48

An optical detection system for biomedical photoacoustic imaging  

Microsoft Academic Search

An all-optical system for the detection of photoacoustic transients is under development for photoacoustic imaging applications. The sensing mechanism is based upon the detection of acoustically-induced variations in the optical thickness of a Fabry Perot polymer film interferometer and provides an alternative to piezoelectric based detection methods. A key advantage is that the sensing geometry is defined by the area

Pc Beard; Tn Mills

2000-01-01

49

Photoacoustic measurement of epidermal melanin  

NASA Astrophysics Data System (ADS)

Most dermatologic laser procedures must consider epidermal melanin, as it is a broadband optical absorber which affects subsurface fluence, effectively limiting the amount of light reaching the dermis and targeted chromophores. An accurate method for quantifying epidermal melanin content would aid clinicians in determining proper light dosage for therapeutic laser procedures. While epidermal melanin content has been quantified non-invasively using optical methods, there is currently no way to determine the melanin distribution in the epidermis. We have developed a photoacoustic probe that uses a Q-switched, frequency doubled Nd:YAG laser operating at 532nm to generate acoustic pulses in skin in vivo. The probe contained a piezoelectric element that detected photoacoustic waves which were then analyzed for epidermal melanin content, using a photoacoustic melanin index (PAMI). We tested 15 human subjects with skin types I--VI using the photoacoustic probe. We also present photoacoustic data for a human subject with vitiligo. Photoacoustic measurement showed melanin in the vitiligo subject was almost completely absent.

Viator, John A.; Svaasand, Lars O.; Aguilar, Guillermo; Choi, Bernard; Nelson, J. Stuart

2003-06-01

50

Spontaneous high piezoelectricity in poly(vinylidene fluoride) nanoribbons produced by iterative thermal size reduction technique.  

PubMed

We produced kilometer-long, endlessly parallel, spontaneously piezoelectric and thermally stable poly(vinylidene fluoride) (PVDF) micro- and nanoribbons using iterative size reduction technique based on thermal fiber drawing. Because of high stress and temperature used in thermal drawing process, we obtained spontaneously polar ? phase PVDF micro- and nanoribbons without electrical poling process. On the basis of X-ray diffraction (XRD) analysis, we observed that PVDF micro- and nanoribbons are thermally stable and conserve the polar ? phase even after being exposed to heat treatment above the melting point of PVDF. Phase transition mechanism is investigated and explained using ab initio calculations. We measured an average effective piezoelectric constant as -58.5 pm/V from a single PVDF nanoribbon using a piezo evaluation system along with an atomic force microscope. PVDF nanoribbons are promising structures for constructing devices such as highly efficient energy generators, large area pressure sensors, artificial muscle and skin, due to the unique geometry and extended lengths, high polar phase content, high thermal stability and high piezoelectric coefficient. We demonstrated two proof of principle devices for energy harvesting and sensing applications with a 60 V open circuit peak voltage and 10 ?A peak short-circuit current output. PMID:25133594

Kanik, Mehmet; Aktas, Ozan; Sen, Huseyin Sener; Durgun, Engin; Bayindir, Mehmet

2014-09-23

51

Micromachining Techniques in Developing High-Frequency Piezoelectric Composite Ultrasonic Array Transducers  

PubMed Central

Several micromachining techniques for the fabrication of high-frequency piezoelectric composite ultrasonic array transducers are described in this paper. A variety of different techniques are used in patterning the active piezoelectric material, attaching backing material to the transducer, and assembling an electronic interconnection board for transmission and reception from the array. To establish the feasibility of the process flow, a hybrid test ultrasound array transducer consisting of a 2-D array having an 8 × 8 element pattern and a 5-element annular array was designed, fabricated, and assessed. The arrays are designed for a center frequency of ~60 MHz. The 2-D array elements are 105 × 105 ?m in size with 5-?m kerfs between elements. The annular array surrounds the square 2-D array and provides the option of transmitting from the annular array and receiving with the 2-D array. Each annular array element has an area of 0.71 mm2 with a 16-?m kerf between elements. The active piezoelectric material is (1 ? x) Pb(Mg1/3Nb2/3)O3?xPbTiO3 (PMN-PT)/epoxy 1–3 composite with a PMN-PT pillar lateral dimension of 8 ?m and an average gap width of ~4 ?m, which was produced by deep reactive ion etching (DRIE) dry etching techniques. A novel electric interconnection strategy for high-density, small-size array elements was proposed. After assembly, the array transducer was tested and characterized. The capacitance, pulse–echo responses, and crosstalk were measured for each array element. The desired center frequency of ~60 MHz was achieved and the ?6-dB bandwidth of the received signal was ~50%. At the center frequency, the crosstalk between adjacent 2-D array elements was about ?33 dB. The techniques described herein can be used to build larger arrays containing smaller elements. PMID:24297027

Liu, Changgeng; Djuth, Frank T.; Zhou, Qifa; Shung, K. Kirk

2014-01-01

52

Micromachining techniques in developing high-frequency piezoelectric composite ultrasonic array transducers.  

PubMed

Several micromachining techniques for the fabrication of high-frequency piezoelectric composite ultrasonic array transducers are described in this paper. A variety of different techniques are used in patterning the active piezoelectric material, attaching backing material to the transducer, and assembling an electronic interconnection board for transmission and reception from the array. To establish the feasibility of the process flow, a hybrid test ultrasound array transducer consisting of a 2-D array having an 8 × 8 element pattern and a 5-element annular array was designed, fabricated, and assessed. The arrays are designed for a center frequency of ~60 MHz. The 2-D array elements are 105 × 105 ?m in size with 5-?m kerfs between elements. The annular array surrounds the square 2-D array and provides the option of transmitting from the annular array and receiving with the 2-D array. Each annular array element has an area of 0.71 mm(2) with a 16-?m kerf between elements. The active piezoelectric material is (1 - x) Pb(Mg1/3Nb2/3)O3-xPbTiO3 (PMN-PT)/epoxy 1-3 composite with a PMN-PT pillar lateral dimension of 8 ?m and an average gap width of ~4 ?m, which was produced by deep reactive ion etching (DRIE) dry etching techniques. A novel electric interconnection strategy for high-density, small-size array elements was proposed. After assembly, the array transducer was tested and characterized. The capacitance, pulse-echo responses, and crosstalk were measured for each array element. The desired center frequency of ~60 MHz was achieved and the -6-dB bandwidth of the received signal was ~50%. At the center frequency, the crosstalk between adjacent 2-D array elements was about -33 dB. The techniques described herein can be used to build larger arrays containing smaller elements. PMID:24297027

Liu, Changgeng; Djuth, Frank T; Zhou, Qifa; Shung, K Kirk

2013-12-01

53

Picosecond measurements using photoacoustic detection  

NASA Technical Reports Server (NTRS)

A report is presented of experimental results on picosecond time-resolved photoacoustic measurements of excited-state lifetimes, cross sections, and polarization properties for organic dye molecules in solution, using a new technique in which the total photoacoustic impulse produced by two ultrashort optical pulses with variable time delay between them is detected. The picosecond photoacoustic detection technique reported here appears to be a promising new way to observe weak excited-state cross sections and to perform picosecond lifetime measurements in a large variety of weakly absorbing and/or nonfluorescing atomic and molecular systems.

Heritier, J.-M.; Siegman, A. E.

1983-01-01

54

Photoacoustic technique applied to ethylene emission in passion fruit seedlings: An experimental approach  

NASA Astrophysics Data System (ADS)

It is well known that plants respond to mechanical perturbation, such as swaying in the wind, touching or brushing, by a reduction in stem length and an increase in stem diameter. Brushing provides a tactile or thigmic stimulation of the plant growing points and undergo physiological and developmental changes that increase stress tolerance. One of the main hormones released by brushing plants is thought to be ethylene, a plant hormone difficult to trace and monitor because it is a gas. The emission rate of ethylene was monitored using a photoacoustic spectrometer based on the infrared absorption of the line 10P12 and 10P14 of CO2 LASER. In response to the brushing treatment, seedlings of passion fruit (Passiflora edulis L.) showed a increase in the ethylene emission. The aim of this work was to investigate the effect of brushing on the ethylene emission rate of passion fruit seedlings.

Pereira, T.; Baptista-Filho, M.; Corrêa, S. F.; de Oliveira, J. G.; da Silva, M. G.; Vargas, H.

2005-06-01

55

Grueneisen relaxation photoacoustic microscopy  

PubMed Central

The temperature-dependent property of the Grueneisen parameter has been employed in photoacoustic imaging mainly to measure tissue temperature. Here we explore this property using a different approach and develop Grueneisen-relaxation photoacoustic microscopy (GR-PAM), a technique that images non-radiative absorption with confocal optical resolution. GR-PAM sequentially delivers two identical laser pulses with a micro-second-scale time delay. The first laser pulse generates a photoacoustic signal and thermally tags the in-focus absorbers. Owing to the temperature dependence of the Grueneisen parameter, when the second laser pulse excites the tagged absorbers within the thermal relaxation time, a photoacoustic signal stronger than the first one is produced. GR-PAM detects the amplitude difference between the two co-located photoacoustic signals, confocally imaging the non-radiative absorption. We greatly improved axial resolution from 45 µm to 2.3 µm and at the same time slightly improved lateral resolution from 0.63 µm to 0.41 µm. In addition, the optical sectioning capability facilitates the measurement of the absolute absorption coefficient without fluence calibration. PMID:25379919

Wang, Lidai; Zhang, Chi; Wang, Lihong V.

2014-01-01

56

Piezoelectric active sensing techniques for damage detection on wind turbine blades  

NASA Astrophysics Data System (ADS)

This paper presents the performance of a variety of structural health monitoring (SHM) techniques, based on the use of piezoelectric active sensors, to determine the structural integrity of a 9m CX-100 wind turbine blade (developed by Sandia National Laboratory). First, the dynamic characterization of a CX-100 blade is performed using piezoelectric transducers, where the results are compared to those by conventional accelerometers. Several SHM techniques, including Lamb wave propagations, frequency response functions, and time series based methods are then utilized to analyze the condition of the wind turbine blade. The main focus of this research is to assess and construct a performance matrix to compare the performance of each method in identifying incipient damage, with a special consideration given the issues related to field deployment. Experiments are conducted on a stationary, full length CX-100 wind turbine blade. This examination is a precursor for planned full-scale fatigue testing of the blade and subsequent tests to be performed on an operational CX-100 Rotor Blade to be flown in the field.

Park, Gyuhae; Farinholt, Kevin M.; Taylor, Stuart G.; Farrar, Charles R.

2011-04-01

57

Use of time history speckle pattern and pulsed photoacoustic techniques to detect the self-accommodating transformation in a Cu-Al-Ni shape memory alloy  

SciTech Connect

Continuous and pulsed electromagnetic radiation was used to detect the self-accommodation mechanism on a polycrystalline Cu-13.83 wt.%Al-2.34 wt.%Ni shape memory alloy. Rectangular samples of this alloy were mechanically polished to observe the austenite and martensite phases. The samples were cooled in liquid nitrogen prior to the experiments to obtain the martensite phase. Using a dynamic speckle technique with a continuous wave laser we obtained the time history of the speckle pattern image and monitored the surface changes caused by the self-accommodation mechanism during the inverse (martensitic to austenitic) transformation. Using a photoacoustic technique based on a pulsed laser source it was also possible to detect the self-accommodation phenomena in a bulk sample. For comparison purposes, we used differential scanning calorimetry (DSC) to detect the critical temperatures of transformation and use these as reference to evaluate the performance of the optical and photoacoustical techniques. In all cases, the same range of temperature was obtained during the inverse transformation. From these results, we conclude that time history speckle pattern (THSP) and pulsed photoacoustic are complementary techniques; they are non-destructive and useful to detect surface and bulk martensitic transformation induced by a temperature change.

Sanchez-Arevalo, F.M., E-mail: fsanchez@iim.unam.mx [CCADET - Universidad Nacional Autonoma de Mexico, A.P. 70-186, Mexico D.F., C.P. 04510 (Mexico); Aldama-Reyna, W. [Departamento Academico de Fisica, Universidad Nacional de Trujillo, Trujillo (Peru); Lara-Rodriguez, A.G. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico (Mexico); Garcia-Fernandez, T. [Universidad Autonoma de la Ciudad de Mexico (UACM), Prolongacion San Isidro 151, Col. San Lorenzo Tezonco, Mexico DF, C.P. 09790 (Mexico); Pulos, G. [Instituto de Investigaciones en Materiales, Universidad Nacional Autonoma de Mexico (Mexico); Trivi, M. [Centro de Investigaciones Opticas, Universidad de la Plata (Argentina); Villagran-Muniz, M. [CCADET - Universidad Nacional Autonoma de Mexico, A.P. 70-186, Mexico D.F., C.P. 04510 (Mexico)

2010-05-15

58

Detection of aqueous glucose based on a cavity size- and optical-wavelength-independent continuous-wave photoacoustic technique.  

PubMed

Toward the achievement of noninvasive and continuous monitoring of blood glucose level, we developed a new measurement method based on the continuous-wave photoacoustic (CW-PA) technique and performed the first validation in vitro with calibrated aqueous glucose solutions. The PA technique has been studied in the past but exclusively based on the pulse setup since the CW one exhibits dependence on the cavity dimensions, which is not compatible with the final application requirements. This paper describes a new strategy relying on the monitoring of the resonant-frequency relative shift induced by the change of glucose concentrations rather than amplitude signal levels at a fixed frequency. From in vitro results, we demonstrate a stable and reproducible response to glucose at various cavity dimensions and optical wavelengths, with a slope of 0.19 ±0.01%/g/dL. From theoretical considerations, this method is consistent with a relative acoustic velocity measurement, which also explains the aforementioned stability. The proposed method then resolves most of the issues usually associated with the CW-PA technique and makes it a potential alternative for the noninvasive and continuous monitoring of glycemia levels. However, experimental determination of sensor responses to albumin and temperature as two potential interferents shows similar levels, which points to the selectivity to glucose as a major issue we should deal with in future development. PMID:22548281

Camou, S; Haga, T; Tajima, T; Tamechika, E

2012-06-01

59

The efficiency of electron transfer from QA? to the donor side of Photosystem II decreases during induction of photosynthesis: Evidences from chlorophyll fluorescence and photoacoustic techniques  

Microsoft Academic Search

The amplitudes ratio of the fast and slow phases (Afast\\/Aslow) in the kinetics of the dark relaxation of variable chlorophyll fluorescence (FV) was studied after various periods of illumination of dark-adapted primary barley leaves. Simultaneously, photosynthetic activity was monitored using the photoacoustic technique and the photochemical and non-photochemical fluorescence quenching parameters. The ratio Afast\\/Aslow changed with the preceding illumination time

Nikolai G. Bukhov; Robert Carpentier

1996-01-01

60

Photoacoustic microscopy  

Microsoft Academic Search

Considerable improvements have been achieved in the design of the photoacoustic microscope, including new sample cells, and better microcomputer hardware, firmware, and software for the scan control and data acquisition. The ND:YAG laser system has been made operational and has been used to obtain preliminary data in the development of a time-domain photoacoustic microscope (pulse-echo termal wave imaging). Scan control

R. L. Thomas; L. D. Favro; P. K. Kuo

1982-01-01

61

Exploration of noninvasive determination of blood glucose concentration by using photoacoustic technique  

NASA Astrophysics Data System (ADS)

Photoacoustic (PA) noninvasive detection has become a research hotspot of measuring blood glucose concentration (BGC) in recent years. This novel method overcomes greatly the scattering light interference problem must be faced in near infrared (NIR) spectroscopy. A PA based BGC measurement set-up was established, in which a Q switched Nd: YAG pumped optical parametric oscillator (OPO) pulsed laser is used as the excitation source and lateral detection model was used to detetct the PA signals of glucose. To validate the profile model of real time PA signal, determine the characteristic wavelengths of glucose, a series of vitro experiments of glucose aqueous solutions were perfromed. Several wavelengths were preliminarily determined as the characteristic wavelengths via the peak-to-peak values difference. The prediction concentration model was established via least square fitting algorithm between PA peak-to-peak values with their different concentrations. The experimental results demonstrated that the PA profile of glucose is consistent with PA meachnism and the root-mean-squre error (RMSE) of prediction concentration can reach 0.77mmol/L. Therefore, this PA based set-up and scheme has the potential value in the BGC monitoring research.

Ren, Zhong; Liu, Guodong; Liu, Ying; Huang, Zhen

2013-09-01

62

Environment-dependent generation of photoacoustic waves from plasmonic nanoparticles.  

PubMed

Nanoparticle-augmented photoacoustics is an emerging technique for molecular imaging. This study investigates the fundamental process of the photoacoustic signal generation by plasmonic nanoparticles suspended in a weakly absorbing fluid. The photoacoustic signal of gold nanospheres with varying silica shell thicknesses is shown to be dominated by the heat transfer between the nanoparticles and the surrounding environment. PMID:22114029

Chen, Yun-Sheng; Frey, Wolfgang; Aglyamov, Salavat; Emelianov, Stanislav

2012-01-01

63

Photoacoustic molecular imaging  

NASA Astrophysics Data System (ADS)

It is well documented that photoacoustic imaging has the capability to differentiate tissue based on the spectral characteristics of tissue in the optical regime. The imaging depth in tissue exceeds standard optical imaging techniques, and systems can be designed to achieve excellent spatial resolution. A natural extension of imaging the intrinsic optical contrast of tissue is to demonstrate the ability of photoacoustic imaging to detect contrast agents based on optically absorbing dyes that exhibit well defined absorption peaks in the infrared. The ultimate goal of this project is to implement molecular imaging, in which Herceptin TM, a monoclonal antibody that is used as a therapeutic agent in breast cancer patients that over express the HER2 gene, is labeled with an IR absorbing dye, and the resulting in vivo bio-distribution is mapped using multi-spectral, infrared stimulation and subsequent photoacoustic detection. To lay the groundwork for this goal and establish system sensitivity, images were collected in tissue mimicking phantoms to determine maximum detection depth and minimum detectable concentration of Indocyanine Green (ICG), a common IR absorbing dye, for a single angle photoacoustic acquisition. A breast mimicking phantom was constructed and spectra were also collected for hemoglobin and methanol. An imaging schema was developed that made it possible to separate the ICG from the other tissue mimicking components in a multiple component phantom. We present the results of these experiments and define the path forward for the detection of dye labeled Herceptin TM in cell cultures and mice models.

Kiser, William L., Jr.; Reinecke, Daniel; DeGrado, Timothy; Bhattacharyya, Sibaprasad; Kruger, Robert A.

2007-02-01

64

Innovative technique for tailoring intrinsic stress in reactively sputtered piezoelectric aluminum nitride films  

SciTech Connect

Novel technical and technological solutions enabling effective stress control in highly textured polycrystalline aluminum nitride (AlN) thin films deposited with ac (40 kHz) reactive sputtering processes are discussed. Residual stress in the AlN films deposited by a dual cathode S-Gun magnetron is well controlled by varying Ar gas pressure, however, since deposition rate and film thickness uniformity depend on gas pressure too, an independent stress control technique has been developed. The technique is based on regulation of the flux of the charged particles from ac plasma discharge to the substrate. In the ac powered S-Gun, a special stress adjustment unit (SAU) is employed for reducing compressive stress in the film by means of redistribution of discharge current between electrodes of the S-Gun leading to controllable suppression of bombardment of the growing film. This technique is complementary to AlN deposition with rf substrate bias which increases ion bombardment and shifts stress in the compressive direction, if required. Using SAU and rf bias functions ensures tailoring intrinsic stress in piezoelectric AlN films for a particular application from high compressive -700 MPa to high tensile +300 MPa and allows the gas pressure to be adjusted independently to fine control the film uniformity. The AlN films deposited on Si substrates and Mo electrodes have strong (002) texture with full width at half maximum ranging from 2 degree sign for 200 nm to 1 degree sign for 2000 nm thick films.

Felmetsger, V. V.; Laptev, P. N.; Tanner, S. M. [Tegal Corporation, 51 Daggett Drive, San Jose, California 95134 (United States)

2009-05-15

65

Influence of the size, geometry and temporal response of the finite piezoelectric sensor on the photoacoustic signal: the case of the point-like source  

NASA Astrophysics Data System (ADS)

Most photoacoustic (PA) work assumes a point-like detection of generated pressure waves; this assumption results in important differences between predicted and experimental signals, as shown in this paper. We used the geometry of a real sensor in the theoretical signal generation through the discretization of the sensing surface, considering each element as a point-like sensor. We modeled the interaction between the wavefront and the real sensor, starting from a well-known PA pressure relation for a point-like source and punctual detection. We obtained the electrical response of the real sensor experimentally and modeled it as a summation of Gaussian functions. The impulse response was convolved with the total PA pressure to obtain the theoretical PA signal. We analyzed the dependence of the source-sensor distance on the discretization size. Then the predicted signal and experimental data were compared for two different frequency response transducers. We found differences in shape and temporal width of simulated PA signals for point-like-source/punctual-detection model and for point-like-source/finite-sensor model.

Bravo-Miranda, C. A.; González-Vega, A.; Gutiérrez-Juárez, G.

2014-06-01

66

Effect of boundary (support) conditions on piezoelectric damping in the case of SSDI vibration control technique  

Microsoft Academic Search

Piezoelectric transducers in conjunction with appropriate electric networks can be used as a mechanical energy dissipation device. If a piezoelectric element is attached to a structure, it is strained as the structure deforms and converts a portion of the vibration energy into electrical energy that can be dissipated through a shunt network in the form of heating. These vibration control

D. Guyomar; S. Mohammadi; C. Richard

2009-01-01

67

Acoustically penetrable optical reflector for photoacoustic tomography.  

PubMed

Photoacoustic tomography (PAT) detects ultrasound signals generated by the objects after absorbing illuminating photons. However, the widely used piezoelectric ultrasound transducers are generally not optically transparent, which would cause conflicts between the light illumination and the ultrasonic detection in PAT. We report a different acoustically penetrable optical reflector (APOR) concept to provide a solution to this conflict. We measured the properties of an APOR and experimentally tested its performance in a PAT system. The results demonstrated that the APOR successfully allowed the transducer to detector photoacoustic signals without affecting the light illumination. Moreover, the APOR concept can be readily implemented in various PAT systems. PMID:23839486

Deng, Zijian; Zhao, Honghong; Ren, Qiushi; Li, Changhui

2013-07-01

68

Photoacoustic imaging in biomedicine Minghua Xua  

E-print Network

The photoacoustic PA effect is the physical basis for PA imaging; it refers to the generation of acoustic waves techniques, including depth profiling in layered media, scanning tomography with focused ultrasonic-infrared light or radio-frequency­wave-induced photoacoustic imaging, which has important potential for early

Wang, Lihong

69

Photoacoustic computed microscopy  

PubMed Central

Photoacoustic microscopy (PAM) is emerging as a powerful technique for imaging microvasculature at depths beyond the ~1?mm depth limit associated with confocal microscopy, two-photon microscopy and optical coherence tomography. PAM, however, is currently qualitative in nature and cannot quantitatively measure important functional parameters including oxyhemoglobin (HbO2), deoxyhemoglobin (HbR), oxygen saturation (sO2), blood flow (BF) and rate of oxygen metabolism (MRO2). Here we describe a new photoacoustic microscopic method, termed photoacoustic computed microscopy (PACM) that combines current PAM technique with a model-based inverse reconstruction algorithm. We evaluate the PACM approach using tissue-mimicking phantoms and demonstrate its in vivo imaging ability of quantifying HbO2, HbR, sO2, cerebral BF and cerebral MRO2 at the small vessel level in a rodent model. This new technique provides a unique tool for neuroscience research and for visualizing microvasculature dynamics involved in tumor angiogenesis and in inflammatory joint diseases. PMID:24828539

Yao, Lei; Xi, Lei; Jiang, Huabei

2014-01-01

70

Photoacoustic computed microscopy  

NASA Astrophysics Data System (ADS)

Photoacoustic microscopy (PAM) is emerging as a powerful technique for imaging microvasculature at depths beyond the ~1 mm depth limit associated with confocal microscopy, two-photon microscopy and optical coherence tomography. PAM, however, is currently qualitative in nature and cannot quantitatively measure important functional parameters including oxyhemoglobin (HbO2), deoxyhemoglobin (HbR), oxygen saturation (sO2), blood flow (BF) and rate of oxygen metabolism (MRO2). Here we describe a new photoacoustic microscopic method, termed photoacoustic computed microscopy (PACM) that combines current PAM technique with a model-based inverse reconstruction algorithm. We evaluate the PACM approach using tissue-mimicking phantoms and demonstrate its in vivo imaging ability of quantifying HbO2, HbR, sO2, cerebral BF and cerebral MRO2 at the small vessel level in a rodent model. This new technique provides a unique tool for neuroscience research and for visualizing microvasculature dynamics involved in tumor angiogenesis and in inflammatory joint diseases.

Yao, Lei; Xi, Lei; Jiang, Huabei

2014-05-01

71

Photoacoustic computed microscopy.  

PubMed

Photoacoustic microscopy (PAM) is emerging as a powerful technique for imaging microvasculature at depths beyond the ~1?mm depth limit associated with confocal microscopy, two-photon microscopy and optical coherence tomography. PAM, however, is currently qualitative in nature and cannot quantitatively measure important functional parameters including oxyhemoglobin (HbO2), deoxyhemoglobin (HbR), oxygen saturation (sO2), blood flow (BF) and rate of oxygen metabolism (MRO2). Here we describe a new photoacoustic microscopic method, termed photoacoustic computed microscopy (PACM) that combines current PAM technique with a model-based inverse reconstruction algorithm. We evaluate the PACM approach using tissue-mimicking phantoms and demonstrate its in vivo imaging ability of quantifying HbO2, HbR, sO2, cerebral BF and cerebral MRO2 at the small vessel level in a rodent model. This new technique provides a unique tool for neuroscience research and for visualizing microvasculature dynamics involved in tumor angiogenesis and in inflammatory joint diseases. PMID:24828539

Yao, Lei; Xi, Lei; Jiang, Huabei

2014-01-01

72

Quantitative photoacoustic tomography with multiple optical sources.  

PubMed

Quantitative imaging of optical properties of biological tissues with high resolution has been a long-sought-after goal of many research groups. Photoacoustic imaging is a hybrid bio-optical imaging technique offering optical absorption contrast with ultrasonic spatial resolution. While photoacoustic methods offer significant promise for high-resolution optical imaging, quantification has thus far proved challenging. In this paper, a noniterative reconstruction technique for producing quantitative photoacoustic images of absorption perturbations is introduced for the case when the optical properties of the turbid background are known and when multiple optical illumination locations are used. Through theoretical developments and computational examples it is demonstrated that multiple-optical-source photoacoustic imaging can produce quantitative optical absorption reconstructions. The combination of optical and photoacoustic measurements is shown to yield improved reconstruction stability. PMID:20563210

Zemp, Roger J

2010-06-20

73

Photoacoustics meets ultrasound: micro-Doppler photoacoustic effect and detection by ultrasound  

E-print Network

In recent years, photoacoustics has attracted intensive research for both anatomical and functional biomedical imaging. However, the physical interaction between photoacoustic generated endogenous waves and an exogenous ultrasound wave is a largely unexplored area. Here, we report the initial results about the interaction of photoacoustic and external ultrasound waves leading to a micro-Doppler photoacoustic (mDPA) effect, which is experimentally observed and consistently modelled. It is based on a simultaneous excitation on the target with a pulsed laser and continuous wave (CW) ultrasound. The thermoelastically induced expansion will modulate the CW ultrasound and leads to transient Doppler frequency shift. The reported mDPA effect can be described as frequency modulation of the intense CW ultrasound carrier through photoacoustic vibrations. This technique may open the possibility to sensitively detect the photoacoustic vibration in deep optically and acoustically scattering medium, avoiding acoustic distor...

Gao, Fei; Zheng, Yuanjin; Ohl, Claus-Dieter

2014-01-01

74

Adaptive Flutter Test Vane: Low Net Passive Stiffness (LNPS) Techniques for Deflection Amplification of Piezoelectric Actuators  

E-print Network

This document outlines the design, development and testing of an adaptive flutter test surface utilizing low net passive stiffness (LNPS) actuator configurations for deflection amplification. The device uses a tapered piezoelectric bender actuator...

Barnhart, Ryan

2012-12-31

75

Measurement of thin film piezoelectric constants using x-ray diffraction technique  

NASA Astrophysics Data System (ADS)

A new method to measure the piezoelectric constants of d33f and d31f of thin films using x-ray diffraction (XRD) is proposed. Piezoelectric constant d33f is calculated from the measurement of change in out-of-plane lattice spacing of the piezoelectric films while piezoelectric constant d31f is obtained from the change in the slope of dphi ? versus sin2 ? curves before and after applying an electric field over the film. This method improves the accuracy by directly measuring the strains in the films induced by the externally applied electric field instead of the surface displacement that could easily be interfered with by environment/vibration and surface morphology of the thin films.

Yu, Y. H.; Lai, M. O.; Lu, L.

2007-12-01

76

Laser damage threshold of SiO{sub 2} films by the photoacoustic mirage technique  

SciTech Connect

SiO{sub 2} thin films of 240 nm thickness have been deposited by a dual-ion-beam sputtering technique using argon or xenon ions mixed with oxygen ions in the assisting ion beam and the role of the assisting ion beam and of the substrate temperature on the laser damage threshold at 308 nm (XeCl excimer laser) has been investigated by the photo acoustic mirage technique. It has been found that the laser damage threshold was quite dependent on the film deposition conditions. The sample grown at a substrate temperature of 300 deg. C and with the argon ion assisting beam was characterized by the highest damage threshold ( congruent with 10 J/cm{sup 2})

Alvisi, M.; Vasanelli, L. [Dipartimento di Scienza dei Materiali, Universita di Lecce, 73100 Lecce (Italy); De Nunzio, G.; Diso, D.; Perrone, M. R.; Protopapa, L. [Dipartimento di Fisica, Universita di Lecce, 73100 Lecce (Italy); Rizzo, A. [PASTIS-CNRSM, ss 7 Appia, km 713, 72100 Brindisi (Italy); Scaglione, S. [Laboratorio Film Sottili, Enea Casaccia, 00060 S. Maria di Galeria, Roma (Italy)

1999-03-15

77

Application of photoacoustic and photothermal techniques for heat conduction measurements in a free-standing chemical vapor-deposited diamond film  

SciTech Connect

Heat conduction in a free-standing chemical vapor-deposited polycrystalline diamond film has been investigated by means of combined front and rear photoacoustic signal detection techniques and also by means of a mirage' photothermal beam deflection technique. The results obtained with the different techniques are consistent with a value of [alpha] = (5.5 [+-] 0.4) [times] 10[sup [minus]4]m[sup 2][center dot]s[sup [minus]1] for thermal diffusivity, resulting in a value of k -(9.8 [+-] 0.7) [times] 10[sup 2]W m[sup [minus]1]. K[sup [minus]1] for thermal conductivity when literature values for the density and heat capacity for natural diamond are used. 25 refs., 7 figs.

Glorieux, C.; De Groote, J.; Lauriks, W.; Thoen, J. (Katholieke Universiteit Leuven (Belgium.)); Fivez, J. (Katholieke Universiteit Leuven (Belgium.) EHSAL, Brussel (Belgium.) Universitaire Faculteiten St. Ignatius, Antwerpen (Belgium.))

1993-11-01

78

Signal processing techniques for damage detection with piezoelectric wafer active sensors and embedded ultrasonic structural radar  

NASA Astrophysics Data System (ADS)

Embedded ultrasonic structural radar (EUSR) algorithm is developed for using piezoelectric wafer active sensor (PWAS) array to detect defects within a large area of a thin-plate specimen. Signal processing techniques are used to extract the time of flight of the wave packages, and thereby to determine the location of the defects with the EUSR algorithm. In our research, the transient tone-burst wave propagation signals are generated and collected by the embedded PWAS. Then, with signal processing, the frequency contents of the signals and the time of flight of individual frequencies are determined. This paper starts with an introduction of embedded ultrasonic structural radar algorithm. Then we will describe the signal processing methods used to extract the time of flight of the wave packages. The signal processing methods being used include the wavelet denoising, the cross correlation, and Hilbert transform. Though hardware device can provide averaging function to eliminate the noise coming from the signal collection process, wavelet denoising is included to ensure better signal quality for the application in real severe environment. For better recognition of time of flight, cross correlation method is used. Hilbert transform is applied to the signals after cross correlation in order to extract the envelope of the signals. Signal processing and EUSR are both implemented by developing a graphical user-friendly interface program in LabView. We conclude with a description of our vision for applying EUSR signal analysis to structural health monitoring and embedded nondestructive evaluation. To this end, we envisage an automatic damage detection application utilizing embedded PWAS, EUSR, and advanced signal processing.

Yu, Lingyu; Bao, Jingjing; Giurgiutiu, Victor

2004-07-01

79

Photoacoustic Tomography of the Brain  

NASA Astrophysics Data System (ADS)

Photoacoustic tomography (PAT) is an emerging hybrid imaging technique with great potential for a wide range of brain imaging applications. A unique feature of PAT is the capability of sensing optical contrasts ultrasonically. Because of the low ultrasonic scattering in tissue, PAT generates high resolution images in both the ballistic and diffusive regimes. With a rich choice of endogenous and exogenous optical contrasts, PAT can provide neurovascular, structural, functional, and molecular brain images at multiple spatial scales. In this chapter, we review the principles and imaging capability of various photoacoustic brain tomography systems and highlight studies published in the past few years.

Xia, Jun; Wang, Lihong V.

80

Photoacoustic spectroscopy for chemical detection  

NASA Astrophysics Data System (ADS)

The Global War on Terror has made rapid detection and identification of chemical and biological agents a priority for Military and Homeland Defense applications. Reliable real-time detection of these threats is complicated by our enemy's use of a diverse range of materials. Therefore, an adaptable platform is necessary. Photoacoustic spectroscopy (PAS) is a useful monitoring technique that is well suited for trace detection of gaseous media. This method routinely exhibits detection limits at the parts-per-billion (ppb) or sub-ppb range. The versatility of PAS also allows for the investigation of solid and liquid analytes. Current research utilizes quantum cascade lasers (QCLs) in combination with an air-coupled solid-phase photoacoustic cell design for the detection of condensed phase material films deposited on a surface. Furthermore, variation of the QCL pulse repetition rate allows for identification and molecular discrimination of analytes based solely on photoacoustic spectra collected at different film depths.

Holthoff, Ellen L.; Pellegrino, Paul M.

2012-06-01

81

Condensed phase photoacoustic spectroscopic detection of porphyrins and dyes  

SciTech Connect

A simple piezoelectric detection system suitable for performing highly sensitive liquid-phase photoacoustic spectroscopy is presented. Performance of the system with respect to linearity, solvent effects, and excitation pulse characteristics is experimentally evaluated and compared with theoretical figures of merit. Limits of detection for various porphyrins, laser dyes, and drugs are presented.

Voigtman, E.; Jurgensen, A.; Winefordner, J.

1981-08-01

82

Photoacoustic microcantilevers  

DOEpatents

A system generates a photoacoustic spectrum in an open or closed environment with reduced noise. A source focuses a beam on a target substance disposed on a base. The base supports a cantilever that measures acoustic waves generated as light is absorbed by the target substance. By focusing a chopped/pulsed light beam on the target substance, a range of optical absorbance may be measured as the wavelength of light changes. An identifying spectrum of the target may detected by monitoring the vibration intensity variation of the cantilever as a function of illuminating wavelength or color.

Thundat, Thomas G. (Knoxville, TN); Van Neste, Charles W. (Kingston, TN); Brown, Gilbert M. (Knoxville, TN); Senesac, Lawrence R. (Knoxville, TN)

2012-06-05

83

Finite element homogenization technique for the characterization of d15 shear piezoelectric macro-fibre composites  

NASA Astrophysics Data System (ADS)

A finite element homogenization method for a shear actuated d15 macro-fibre composite (MFC) made of seven layers (Kapton, acrylic, electrode, piezoceramic fibre and epoxy composite, electrode, acrylic, Kapton) is proposed and used for the characterization of its effective material properties. The methodology is first validated for the MFC active layer only, made of piezoceramic fibre and epoxy, through comparison with previously published analytical results. Then, the methodology is applied to the seven-layer MFC. It is shown that the packaging reduces significantly the shear stiffness of the piezoceramic material and, thus, leads to significantly smaller effective electromechanical coupling coefficient k15 and piezoelectric stress constant e15 when compared to the piezoceramic fibre properties. However, it is found that the piezoelectric charge constant d15 is less affected by the softer layers required by the MFC packaging.

Trindade, M. A.; Benjeddou, A.

2011-07-01

84

Temperature mapping using photoacoustic and thermoacoustic tomography  

NASA Astrophysics Data System (ADS)

Photoacoustic (PA) and thermoacoustic (TA) effects are based on the generation of acoustic waves after tissues absorb electromagnetic energy. The amplitude of the acoustic signal is related to the temperature of the absorbing target tissue. A combined photoacoustic and thermoacoustic imaging system built around a modified commercial ultrasound scanner was used to obtain an image of the target's temperature, using reconstructed photoacoustic or thermoacoustic images. To demonstrate these techniques, we used photoacoustic imaging to monitor the temperature changes of methylene blue solution buried at a depth of 1.5 cm in chicken breast tissue from 12 to 42 °C. We also used thermoacoustic imaging to monitor the temperature changes of porcine muscle embedded in 2 cm porcine fat from 14 to 28 °C. The results demonstrate that these techniques can provide noninvasive real-time temperature monitoring of embedded objects and tissue.

Ke, Haixin; Erpelding, Todd N.; Jankovic, Ladislav; Wang, Lihong V.

2012-02-01

85

Photoacoustic thermography of tissue.  

PubMed

Photoacoustic (PA) techniques can measure temperature in biological tissues because PA signal amplitude is sensitive to tissue temperature. So far, temperature-measuring PA techniques have focused on sensing of temperature changes at a single position. In this work, we photoacoustically measured spatial distribution of temperature in deep tissue. By monitoring the temperature at a single position using a thermocouple, the relationship between the PA signal amplitude and the actual temperature was determined. The relationship was then used to translate a PA image into a temperature map. This study showed that it is possible to calibrate the system for the temperature range of hyperthermia using single-point measurements over a smaller temperature range. Our experimental results showed a precision of -0.8±0.4°C (mean±standard error) in temperature measurement, and a spatial resolution as fine as 1.0 mm. PA techniques can be potentially applied to monitor temperature distribution deep in tissue during hyperthermia treatment of cancer. PMID:24522803

Ke, Haixin; Tai, Stephen; Wang, Lihong V

2014-02-01

86

Improved Photoacoustic Generator  

NASA Astrophysics Data System (ADS)

In conventional photoacoustic setups, the photoacoustic signal results from stimulation of a sample placed in the photoacoustic cell by the light modulated at a selected frequency. The signal can be amplified in a resonance photoacoustic cell. For this purpose, different types of acoustic resonators are used. Acoustic resonators are passive, frequency selective elements. An acoustic resonator used in a photoacoustic cell offers the opportunity to design a system working on a basis similar to that of a self-oscillating generator. The geometrical dimensions of an acoustic resonator, and the temperature, composition, and concentration of substances in the gas filling its interior determine the resonance frequency. In conventional photoacoustic setups, in which the resonance method is used, the variability of parameters requires continuous adjusting of or searching for the actual resonance frequency. Use of a fixed and arbitrary selected modulation frequency of the light beam can cause considerable errors in detection of substances in the sample or in determination of their concentration. Unlike conventional photoacoustic methods, the frequency of a photoacoustic signal in an improved photoacoustic generator is self-tuned to the actual resonant frequency of the photoacoustic cell. The improved photoacoustic generator operates without an external circuit that controls the optical modulator. The improved photoacoustic generator has been tested in different measurements of the concentration of methane in air. The automatic gain control signal can be used for determination of the absorption by the sample.

Borowski, T.; Burd, A.; Suchenek, M.; Starecki, T.

2014-12-01

87

Speckle in photoacoustic tomography  

Microsoft Academic Search

Photoacoustic tomography is emerging as a promising imaging modality for various biomedical applications. Unlike traditional ultrasound imaging that is plagued by strong speckle artifacts, no obvious speckle has so far been observed in photoacoustic images. We systematically studied the reason for this lack of speckle in photoacoustic tomography based on speckle contrast. Theoretical explanations were validated by simulation. The results

Li Li; Lihong V. Wang

2006-01-01

88

Quantitative imaging of chromophore concentrations using a photoacoustic forward model  

Microsoft Academic Search

Photoacoustic spectroscopy has been shown to be capable of making non-invasive, spatially resolved measurements of haemodynamic parameters, such as the concentrations of oxy- and deoxyhaemoglobin and blood oxygen saturation. The development of photoacoustic techniques for molecular imaging that go beyond the measurement of haemodynamic parameters has recently become an area of interest. These techniques are aimed at the detection and

J. Laufer; E. Zhang; B. Cox; P. Beard

2008-01-01

89

FT-IR-cPAS—New Photoacoustic Measurement Technique for Analysis of Hot Gases: A Case Study on VOCs  

PubMed Central

This article describes a new photoacoustic FT-IR system capable of operating at elevated temperatures. The key hardware component is an optical-readout cantilever microphone that can work up to 200 °C. All parts in contact with the sample gas were put into a heated oven, incl. the photoacoustic cell. The sensitivity of the built photoacoustic system was tested by measuring 18 different VOCs. At 100 ppm gas concentration, the univariate signal to noise ratios (1?, measurement time 25.5 min, at highest peak, optical resolution 8 cm?1) of the spectra varied from minimally 19 for o-xylene up to 329 for butyl acetate. The sensitivity can be improved by multivariate analyses over broad wavelength ranges, which effectively co-adds the univariate sensitivities achievable at individual wavelengths. The multivariate limit of detection (3?, 8.5 min, full useful wavelength range), i.e., the best possible inverse analytical sensitivity achievable at optimum calibration, was calculated using the SBC method and varied from 2.60 ppm for dichloromethane to 0.33 ppm for butyl acetate. Depending on the shape of the spectra, which often only contain a few sharp peaks, the multivariate analysis improved the analytical sensitivity by 2.2 to 9.2 times compared to the univariate case. Selectivity and multi component ability were tested by a SBC calibration including 5 VOCs and water. The average cross selectivities turned out to be less than 2% and the resulting inverse analytical sensitivities of the 5 interfering VOCs was increased by maximum factor of 2.2 compared to the single component sensitivities. Water subtraction using SBC gave the true analyte concentration with a variation coefficient of 3%, although the sample spectra (methyl ethyl ketone, 200 ppm) contained water from 1,400 to 100k ppm and for subtraction only one water spectra (10k ppm) was used. The developed device shows significant improvement to the current state-of-the-art measurement methods used in industrial VOC measurements. PMID:22163900

Hirschmann, Christian Bernd; Koivikko, Niina Susanna; Raittila, Jussi; Tenhunen, Jussi; Ojala, Satu; Rahkamaa-Tolonen, Katariina; Marbach, Ralf; Hirschmann, Sarah; Keiski, Riitta Liisa

2011-01-01

90

Photoacoustic wave propagation simulations using the FDTD method with Berenger's perfectly matched layers  

Microsoft Academic Search

Several photoacoustic (PA) techniques, such as photoacoustic imaging, spectroscopy, and parameter sensing, measure quantities that are closely related to optical absorption, position detection, and laser irradiation parameters. The photoacoustic waves in biomedical applications are usually generated by elastic thermal expansion, which has advantages of nondestructiveness and relatively high conversion efficiency from optical to acoustic energy. Most investigations describe this process

Yae-Lin Sheu; Chen-Wei Wei; Chao-Kang Liao; Pai-Chi Li

2008-01-01

91

4-D Photoacoustic Tomography  

NASA Astrophysics Data System (ADS)

Photoacoustic tomography (PAT) offers three-dimensional (3D) structural and functional imaging of living biological tissue with label-free, optical absorption contrast. These attributes lend PAT imaging to a wide variety of applications in clinical medicine and preclinical research. Despite advances in live animal imaging with PAT, there is still a need for 3D imaging at centimeter depths in real-time. We report the development of four dimensional (4D) PAT, which integrates time resolutions with 3D spatial resolution, obtained using spherical arrays of ultrasonic detectors. The 4D PAT technique generates motion pictures of imaged tissue, enabling real time tracking of dynamic physiological and pathological processes at hundred micrometer-millisecond resolutions. The 4D PAT technique is used here to image needle-based drug delivery and pharmacokinetics. We also use this technique to monitor 1) fast hemodynamic changes during inter-ictal epileptic seizures and 2) temperature variations during tumor thermal therapy.

Xiang, Liangzhong; Wang, Bo; Ji, Lijun; Jiang, Huabei

2013-01-01

92

4-D Photoacoustic Tomography  

PubMed Central

Photoacoustic tomography (PAT) offers three-dimensional (3D) structural and functional imaging of living biological tissue with label-free, optical absorption contrast. These attributes lend PAT imaging to a wide variety of applications in clinical medicine and preclinical research. Despite advances in live animal imaging with PAT, there is still a need for 3D imaging at centimeter depths in real-time. We report the development of four dimensional (4D) PAT, which integrates time resolutions with 3D spatial resolution, obtained using spherical arrays of ultrasonic detectors. The 4D PAT technique generates motion pictures of imaged tissue, enabling real time tracking of dynamic physiological and pathological processes at hundred micrometer-millisecond resolutions. The 4D PAT technique is used here to image needle-based drug delivery and pharmacokinetics. We also use this technique to monitor 1) fast hemodynamic changes during inter-ictal epileptic seizures and 2) temperature variations during tumor thermal therapy. PMID:23346370

Xiang, Liangzhong; Wang, Bo; Ji, Lijun; Jiang, Huabei

2013-01-01

93

Backward-mode photoacoustic transducer for sensing optical scattering and ultrasonic attenuation: determining fraction consistencies in pulp suspensions  

NASA Astrophysics Data System (ADS)

An innovative backward-mode photoacoustic transducer was developed, consisting of an optical fibre, a composite absorber, piezoelectric film and high impedance preamplifier. By receiving scattering light from a turbid suspension, the transducer produces a photoacoustic source in it. This source emits two photoacoustic waves travelling in opposite directions. The waves' amplitudes relate to the optical scattering properties of the suspension, and the echo of a wave returning from the suspension carries information of acoustic attenuation. By assessing the optical scattering and acoustic attenuation, fraction consistencies in a two-fractional suspension can be determined if one fraction dominantly scatters light and the other mainly attenuates ultrasound. This technique is used in this paper to investigate paper pulp suspensions. Pulp consists of wood celluloses and wood fines (or extra-added fillers in some cases), where cellulose lengths range from a few sub-millimetres to millimetres and fines/filler sizes are a few tens of micrometres or smaller. Due to their different size and shape, celluloses and fines (or fillers) have different optical scattering and acoustic attenuation properties. Experimental results showed that the transducer can measure pulp consistency with good linearity at least in the range from 0.5% to 3%, and that it can distinguish pulp cellulose from fines or fillers (TiO2 particles). Needless to say, this technique is also suitable for determining other suspensions in the food, pharmaceutical and mineral industries.

Zhao, Zuomin; Törmänen, Matti; Myllylä, Risto

2010-02-01

94

Photoacoustic radiation force on a microbubble  

NASA Astrophysics Data System (ADS)

We investigate the radiation force on a microbubble due to the photoacoustic wave which is generated by using a pulsed laser. In particular, we focus on the dependence of pulsed laser parameters on the radiation force. In order to do so, we first obtain a new and comprehensive analytical solution to the photoacoustic wave equation based on the Fourier transform for various absorption profiles. Then, we write an expression of the radiation force containing explicit laser parameters, pulse duration, and beamwidth of the laser. Furthermore, we calculate the primary radiation force acting on a microbubble. We show that laser parameters and the position of the microbubble relative to a photoacoustic source have a considerable effect on the primary radiation force. By means of recent developments in laser technologies that render tunability of pulse duration and repetition frequency possible, an adjustable radiation force can be applied to microbubbles. High spatial control of applied force is ensured on account of smaller focal spots achievable by focused optics. In this context, conventional piezoelectric acoustic source applications could be surpassed. In addition, it is possible to increase the radiation force by making source wavelength with the absorption peak of absorber concurrent. The application of photoacoustic radiation force can open a cache of opportunities such as manipulation of microbubbles used as contrast agents and as carrier vehicles for drugs and genes with a desired force along with in vivo applications.

Erkol, Hakan; Aytac-Kipergil, Esra; Unlu, Mehmet Burcin

2014-08-01

95

Photoacoustic thermal diffusion flowmetry.  

PubMed

Thermal Diffusion Flowmetry (TDF) (also called Heat Clearance Method or Thermal Clearance Method) is a longstanding technique for measuring blood flow or blood perfusion in living tissues. Typically, temperature transients and/or gradients are induced in a volume of interest and the temporal and/or spatial temperature variations which follow are measured and used for calculation of the flow. In this work a new method for implementing TDF is studied theoretically and experimentally. The heat deposition which is required for TDF is implemented photothermally (PT) and the measurement of the induced temperature variations is done by photoacoustic (PA) thermometry. Both excitation light beams (the PT and the PA) are produced by directly modulated 830 nm laser diodes and are conveniently delivered to the volume under test by the same optical fiber. The method was tested experimentally using a blood-filled phantom vessel and the results were compared with a theoretical prediction based on the heat and the photoacoustic equations. The fitting of a simplified lumped thermal model to the experimental data yielded estimated values of the blood velocity at different flow rates. By combining additional optical sources at different wavelengths it will be possible to utilize the method for non-invasive simultaneous measurement of blood flow and oxygen saturation using a single fiber probe. PMID:22574267

Sheinfeld, Adi; Eyal, Avishay

2012-04-01

96

Photoacoustic Study of Fungal Disease of Acai ( Euterpe oleracea) Seeds  

Microsoft Academic Search

Photoacoustic spectroscopy is introduced as a promising experimental technique to investigate fungus infected Acai ( Euterpe oleracea) seeds. Photoacoustic spectra of healthy and infected Acai seeds with the fungus Colletotrichum gloeosporioides were recorded firstly in the modulation frequency range of 5Hz to 700 Hz, while keeping the wavelength of excitation radiation of a Xe arc-lamp constant, to ascertain the depth

Denise V. Rezende; O. A. C. Nunes; A. C. Oliveira

2009-01-01

97

Photoacoustic tomography: principles and advances  

PubMed Central

Photoacoustic tomography (PAT) is an emerging imaging modality that shows great potential for preclinical research and clinical practice. As a hybrid technique, PAT is based on the acoustic detection of optical absorption from either endogenous chromophores, such as oxy-hemoglobin and deoxy-hemoglobin, or exogenous contrast agents, such as organic dyes and nanoparticles. Because ultrasound scatters much less than light in tissue, PAT generates high-resolution images in both the optical ballistic and diffusive regimes. Over the past decade, the photoacoustic technique has been evolving rapidly, leading to a variety of exciting discoveries and applications. This review covers the basic principles of PAT and its different implementations. Strengths of PAT are highlighted, along with the most recent imaging results. PMID:25642127

Xia, Jun; Yao, Junjie; Wang, Lihong V.

2014-01-01

98

Determination of formation constants at elevated temperatures by laser-induced photoacoustic spectroscopy  

SciTech Connect

A photoacoustic spectrometer has been developed for high-sensitivity optical absorption measurements of aqueous solutions at temperatures from ambient to 90 C. The light source is a Nd:YAG-pumped dye laser, and the photoacoustic signal is detected with a piezoelectric transducer coupled to a thermostatted quartz cell. The temperature dependence of the observed photoacoustic signal is compared to a theoretical model, and the application of the instrument to the determination of formation constants of metal-ligand complexes at elevated temperatures is discussed. Measurements of the temperature dependence of the formation constant for AmCO{sub 3}{sup +} are reported.

Wruck, D.A.; Kadkhodayan, B.; Russo, R.E. [Lawrence Livermore National Laboratory, CA (United States)] [and others

1994-12-31

99

Quantitative Photoacoustic Imaging of Nanoparticles in Cells and Tissues  

PubMed Central

Quantitative visualization of nanoparticles in cells and tissues, while preserving the spatial information, is very challenging. A photoacoustic imaging technique to depict the presence and quantity of nanoparticles is presented. This technique is based on the dependence of the photoacoustic signal with both the nanoparticle quantity and the laser fluence. Quantitative photoacoustic imaging is a robust technique that doesn’t require knowledge of the local fluence, but a relative change in the fluence. This eliminates the need for sophisticated methods or models to determine the energy distribution of light in turbid media. Quantitative photoacoustic imaging was first applied to nanoparticle-loaded cells and quantitation was validated by inductively coupled plasma mass spectrometry. Quantitative photoacoustic imaging was then extended to xenograft tumor tissue sections, and excellent agreement with traditional histopathological analysis was demonstrated. Our results suggest that quantitative photoacoustic imaging may be used in many applications including the determination of the efficiency and effectiveness of molecular targeting strategies for cell studies and animal models, the quantitative assessment of photoacoustic contrast agent biodistribution, and the validation of in vivo photoacoustic imaging. PMID:23312348

Cook, Jason R.; Frey, Wolfgang; Emelianov, Stanislav

2013-01-01

100

Piezoelectric Polymers  

NASA Technical Reports Server (NTRS)

The purpose of this review is to detail the current theoretical understanding of the origin of piezoelectric and ferroelectric phenomena in polymers; to present the state-of-the-art in piezoelectric polymers and emerging material systems that exhibit promising properties; and to discuss key characterization methods, fundamental modeling approaches, and applications of piezoelectric polymers. Piezoelectric polymers have been known to exist for more than forty years, but in recent years they have gained notoriety as a valuable class of smart materials.

Harrison, J. S.; Ounaies, Z.; Bushnell, Dennis M. (Technical Monitor)

2001-01-01

101

Piezoelectric valve  

DOEpatents

A motorized valve has a housing having an inlet and an outlet to be connected to a pipeline, a saddle connected with the housing, a turn plug having a rod, the turn plug cooperating with the saddle, and a drive for turning the valve body and formed as a piezoelectric drive, the piezoelectric drive including a piezoelectric generator of radially directed standing acoustic waves, which is connected with the housing and is connectable with a pulse current source, and a rotor operatively connected with the piezoelectric generator and kinematically connected with the rod of the turn plug so as to turn the turn plug when the rotor is actuated by the piezoelectric generator.

Petrenko, Serhiy Fedorovich

2013-01-15

102

Design considerations for ultrasound detectors in photoacoustic breast imaging  

NASA Astrophysics Data System (ADS)

The ultrasound detector is the heart of a photoacoustic imaging system. In photoacoustic imaging of the breast there is a requirement to detect tumors located a few centimeters deep in tissue, where the light is heavily attenuated. Thus a sensitive ultrasound transducer is of crucial importance. As the frequency content of photoacoustic waves are inversely proportional to the dimensions of the absorbing structures, and in tissue can range from hundreds of kHz to tens of MHz, a broadband ultrasound transducer is required centered on an optimum frequency. A single element piezoelectric transducer structurally consists of the active piezoelectric material, front- and back-matching layers and a backing layer. To have both high sensitivity and broad bandwidth, the materials, their acoustic characteristics and their dimensions should be carefully chosen. In this paper, we present design considerations of an ultrasound transducer for imaging the breast such as the detector sensitivity and frequency response, which guides the selection of active material, matching layers and their geometries. We iterate between simulation of detector performance and experimental characterization of functional models to arrive at an optimized implementation. For computer simulation, we use 1D KLM and 3D finite-element based models. The optimized detector has a large-aperture possessing a center frequency of 1 MHz with fractional bandwidth of more than 80%. The measured minimum detectable pressure is 0.5 Pa, which is two orders of magnitude lower than the detector used in the Twente photoacoustic mammoscope.

Xia, Wenfeng; Piras, Daniele; Singh, Mithun K. A.; van Hespen, Johan C. G.; van Veldhoven, Spiridon; Prins, Christian; van Leeuwen, Ton G.; Steenbergen, Wiendelft; Manohar, Srirang

2013-03-01

103

Photoacoustic Wave Propagation Simulations Using the Finite-Difference Time-Domain Method with Berenger's Perfectly Matched Layers  

Microsoft Academic Search

Several photoacoustic (PA) techniques, such as photoacoustic imaging, spectroscopy, and parameter sensing, measure quantities that are closely related to optical absorption, position detection, and laser irradiation parameters. The photoacoustic waves in biomedical applications are usually generated by elastic thermal expansion, which has advantages of nondestructiveness and relatively high conversion efficiency from optical to acoustic energy. Most investigations describe this process

Yae-Lin Sheu; Pai-Chi Lia

104

Improvement of depth resolution on photoacoustic imaging using multiphoton absorption  

NASA Astrophysics Data System (ADS)

Commercial imaging systems, such as computed tomography and magnetic resonance imaging, are frequently used powerful tools for observing structures deep within the human body. However, they cannot precisely visualized several-tens micrometer-sized structures for lack of spatial resolution. In this presentation, we propose photoacoustic imaging using multiphoton absorption technique to generate ultrasonic waves as a means of improving depth resolution. Since the multiphoton absorption occurs at only the focus point and the employed infrared pulses deeply penetrate living tissues, it enables us to extract characteristic features of structures embedded in the living tissue. When nanosecond pulses from a 1064-nm Nd:YAG laser were focused on Rhodamine B/chloroform solution (absorption peak: 540 nm), the peak intensity of the generated photoacoustic signal was proportional to the square of the input pulse energy. This result shows that the photoacoustic signals can be induced by the two-photon absorption of infrared nanosecond pulse laser and also can be detected by a commercial low-frequency MHz transducer. Furthermore, in order to evaluate the depth resolution of multiphoton-photoacoustic imaging, we investigated the dependence of photoacoustic signal on depth position using a 1-mm-thick phantom in a water bath. We found that the depth resolution of two-photon photoacoustic imaging (1064 nm) is greater than that of one-photon photoacoustic imaging (532 nm). We conclude that evolving multiphoton-photoacoustic imaging technology renders feasible the investigation of biomedical phenomena at the deep layer in living tissue.

Yamaoka, Yoshihisa; Fujiwara, Katsuji; Takamatsu, Tetsuro

2007-07-01

105

Effect of an external mechanical load on elastic stresses near radial cracks in Al 2 O 3 -SiC-TiC ceramics: Photoacoustic study  

Microsoft Academic Search

The variation of the photoacoustic signal near the mouths of radial cracks in Vickers-indented externally loaded Al2O3-SiC-TiC ceramics is studied. A theoretical model of a photoacoustic signal that is recorded near the mouths of vertical cracks\\u000a is suggested. Indentation zones in Al2O3-SiC-TiC ceramics are visualized by laser scanning photoacoustic microscopy. The sensitivity of the photoacoustic method with\\u000a piezoelectric detection of

K. L. Muratikov; A. L. Glazov

2003-01-01

106

Piezoelectrically Enhanced Photocathodes  

NASA Technical Reports Server (NTRS)

Doping of photocathodes with materials that have large piezoelectric coefficients has been proposed as an alternative means of increasing the desired photoemission of electrons. Treating cathode materials to increase emission of electrons is called "activation" in the art. It has been common practice to activate photocathodes by depositing thin layers of suitable metals (usually, cesium). Because cesium is unstable in air, fabrication of cesiated photocathodes and devices that contain them must be performed in sealed tubes under vacuum. It is difficult and costly to perform fabrication processes in enclosed, evacuated spaces. The proposed piezoelectrically enhanced photocathodes would have electron-emission properties similar to those of cesiated photocathodes but would be stable in air, and therefore could be fabricated more easily and at lower cost. Candidate photocathodes include nitrides of elements in column III of the periodic table . especially compounds of the general formula Al(x)Ga(1.x)N (where 0< or = x < or =.1). These compounds have high piezoelectric coefficients and are suitable for obtaining response to ultraviolet light. Fabrication of a photocathode according to the proposal would include inducement of strain in cathode layers during growth of the layers on a substrate. The strain would be induced by exploiting structural mismatches among the various constituent materials of the cathode. Because of the piezoelectric effect in this material, the strain would give rise to strong electric fields that, in turn, would give rise to a high concentration of charge near the surface. Examples of devices in which piezoelectrically enhanced photocathodes could be used include microchannel plates, electron- bombarded charge-coupled devices, image tubes, and night-vision goggles. Piezoelectrically enhanced photocathode materials could also be used in making highly efficient monolithic photodetectors. Highly efficient and stable piezoelectrically enhanced, ultraviolet-sensitive photocathodes and photodetectors could be fabricated by use of novel techniques for growing piezoelectrically enhanced layers, in conjunction with thinning and dopant-selective etching techniques.

Beach, Robert A.; Nikzad, Shouleh; Bell, Lloyd Douglas; Strittmatter, Robert

2011-01-01

107

Photoacoustic cell for ultrasound contrast agent characterization.  

PubMed

Photoacoustics has emerged as a tool for the study of liquid gel suspension behavior and has been recently employed in a number of new biomedical applications. In this paper, a photoacoustic sensor is presented which was designed and realized for analyzing photothermal signals from solutions filled with microbubbles, commonly used as ultrasound contrast agents in echographic imaging techniques. It is a closed cell device, where photothermal volume variation of an aqueous solution produces the periodic deflection of a thin membrane closing the cell at the end of a short pipe. The cell then acts as a Helmholtz resonator, where the displacement of the membrane is measured through a laser probe interferometer, whereas photoacoustic signal is generated by a laser chopped light beam impinging onto the solution through a glass window. Particularly, the microbubble shell has been modeled through an effective surface tension parameter, which has been then evaluated from experimental data through the shift of the resonance frequencies of the photoacoustic sensor. This shift of the resonance frequencies of the photoacoustic sensor caused by microbubble solutions is high enough for making such a cell a reliable tool for testing ultrasound contrast agent, particularly for bubble shell characterization. PMID:21034110

Alippi, A; Bettucci, A; Biagioni, A; D'Orazio, A; Germano, M; Passeri, D

2010-10-01

108

Piezoelectric Scanners  

NASA Astrophysics Data System (ADS)

Bimorph piezoelectric elements show relative large axial displacements at moderate voltages. Their response to voltage variations is very fast. The re-produceability of the displacement is practically limited only by the mechanical and electrical supplementary equipment. In combination with a deflection mirror linear scans or two-dimensional scan pattern can be generated. Fast scanning with good linearity and repeatability is possible, either in a resonant mode or in a random acces mode. However, the hysteresis of the piezoelectric material and the large capacitance of the elements impose some constraints on the applicability of the piezoelectric scanners. In the first part of the paper the properties of piezoelectric elements are discussed in view of scanner application; in the second part an experimental single mirror two-axis piezoelectric scanner is described. Some suggestions for future applications of piezoelectric scanners are made.

Hohner, M.; Manhart, S.

1987-09-01

109

Multi-view optical resolution photoacoustic microscopy  

PubMed Central

Optical resolution photoacoustic microscopy (OR-PAM), while providing high lateral resolution, has been limited by its relatively poor acoustically determined axial resolution. Although this limitation has been tackled in recent works by using either broadband acoustic detection or nonlinear photoacoustic effects, a flexible solution with three dimensional optical resolution in reflection mode remains desired. Herein we present a multi-view OR-PAM technique. By imaging the sample from multiple view angles and reconstructing the data using a multi-view deconvolution method, we have experimentally demonstrated an isotropic optical resolution in three dimensions.

Zhu, Liren; Li, Lei; Gao, Liang; Wang, Lihong V.

2014-01-01

110

Enhanced photoacoustic detection using photonic crystal substrate  

SciTech Connect

This paper demonstrates the enhanced photoacoustic sensing of surface-bound light absorbing molecules and metal nanoparticles using a one-dimensional photonic crystal (PC) substrate. The PC structure functions as an optical resonator at the wavelength where the analyte absorption is strong. The optical resonance of the PC sensor provides an intensified evanescent field with respect to the excitation light source and results in enhanced optical absorption by surface-immobilized samples. For the analysis of a light absorbing dye deposited on the PC surface, the intensity of photoacoustic signal was enhanced by more than 10-fold in comparison to an un-patterned acrylic substrate. The technique was also applied to detect gold nanorods and exhibited more than 40 times stronger photoacoustic signals. The demonstrated approach represents a potential path towards single molecule absorption spectroscopy with greater performance and inexpensive instrumentation.

Zhao, Yunfei; Liu, Kaiyang [Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa 50011 (United States); McClelland, John [Ames Laboratory-USDOE, Ames, Iowa 50011 (United States); Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011 (United States); Department of Biochemistry, Biophysics, and Molecular Biology, Iowa State University, Ames, Iowa 50011 (United States); Lu, Meng, E-mail: menglu@iastate.edu [Department of Electrical and Computer Engineering, Iowa State University, Ames, Iowa 50011 (United States); Department of Mechanical Engineering, Iowa State University, Ames, Iowa 50011 (United States)

2014-04-21

111

Combining H and interval techniques to design robust low order controllers: application to piezoelectric actuators  

E-print Network

. The paper is particularly focused on the design of a robust PID controller to control systems with order nCombining H and interval techniques to design robust low order controllers: application Abstract-- This paper addresses the design of ro- bust controllers for interval systems. For that, the H

Paris-Sud XI, Université de

112

Photoacoustic spectra of MoS/sub 2/  

SciTech Connect

The photoacoustic spectra of powdered MoS/sub 2/ prepared by particle-size reduction and dilution have been determined and compared with the optical transmittance spectra of single crystals and thin-film deposits. MoS/sub 2/ was chosen as a typical representative of the layer-structured transition metal dichalcogenides, for which optical properties are important in explaining their unusual structural and transport properties. Reasonably well-resolved photoacoustic spectra were obtained by a layering technique using KCl as a diluent. Analysis of the experiments indicated that the spectral resolution was obtained not by reduction in photoacoustic signal saturation but by the enhancement of diffuse reflectance.

Carlson, K.D.; Hodul, D.

1983-09-15

113

Piezoelectric osteotomy in hand surgery: first experiences with a new technique  

PubMed Central

Background In hand and spinal surgery nerve lesions are feared complications with the use of standard oscillating saws. Oral surgeons have started using a newly developed ultrasound bone scalpel when performing precise osteotomies. By using a frequency of 25–29 kHz only mineralized tissue is cut, sparing the soft tissue. This reduces the risk of nerve lesions. As there is a lack of experience with this technique in the field of orthopaedic bone surgery, we performed the first ultrasound osteotomy in hand surgery. Method While performing a correctional osteotomy of the 5th metacarpal bone we used the Piezosurgery® Device from Mectron [Italy] instead of the usual oscillating saw. We will report on our experience with one case, with a follow up time of one year. Results The cut was highly precise and there were no vibrations of the bone. The time needed for the operation was slightly longer than the time needed while using the usual saw. Bone healing was good and at no point were there any neurovascular disturbances. Conclusion The Piezosurgery® Device is useful for small long bone osteotomies. Using the fine tip enables curved cutting and provides an opportunity for new osteotomy techniques. As the device selectively cuts bone we feel that this device has great potential in the field of hand- and spinal surgery. PMID:16611362

Hoigne, Dominik J; Stübinger, Stefan; Kaenel, Oliver Von; Shamdasani, Sonia; Hasenboehler, Paula

2006-01-01

114

Photoacoustic spectroscopy of ?-hematin  

NASA Astrophysics Data System (ADS)

Malaria affects over 200 million individuals annually, resulting in 800?000 fatalities. Current tests use blood smears and can only detect the disease when 0.1-1% of blood cells are infected. We are investigating the use of photoacoustic flowmetry to sense as few as one infected cell among 10 million or more normal blood cells, thus diagnosing infection before patients become symptomatic. Photoacoustic flowmetry is similar to conventional flow cytometry, except that rare cells are targeted by nanosecond laser pulses to induce ultrasonic responses. This system has been used to detect single melanoma cells in 10 ml of blood. Our objective is to apply photoacoustic flowmetry to detection of the malaria pigment hemozoin, which is a byproduct of parasite-digested hemoglobin in the blood. However, hemozoin is difficult to purify in quantities greater than a milligram, so a synthetic analog, known as ?-hematin was derived from porcine hemin. The specific purpose of this study is to establish the efficacy of using ?-hematin, rather than hemozoin, for photoacoustic measurements. We characterized ?-hematin using UV-vis spectroscopy, TEM, and FTIR, then tested the effects of laser irradiation on the synthetic product. We finally determined its absorption spectrum using photoacoustic excitation. UV-vis spectroscopy verified that ?-hematin was distinctly different from its precursor. TEM analysis confirmed its previously established nanorod shape, and comparison of the FTIR results with published spectroscopy data showed that our product had the distinctive absorbance peaks at 1661 and 1206 cm-1. Also, our research indicated that prolonged irradiation dramatically alters the physical and optical properties of the ?-hematin, resulting in increased absorption at shorter wavelengths. Nevertheless, the photoacoustic absorption spectrum mimicked that generated by UV-vis spectroscopy, which confirms the accuracy of the photoacoustic method and strongly suggests that photoacoustic flowmetry may be used as a tool for diagnosis of malaria infection.

Samson, Edward B.; Goldschmidt, Benjamin S.; Whiteside, Paul J. D.; Sudduth, Amanda S. M.; Custer, John R.; Beerntsen, Brenda; Viator, John A.

2012-06-01

115

Piezoelectric single crystals for ultrasonic transducers in biomedical applications.  

PubMed

Piezoelectric single crystals, which have excellent piezoelectric properties, have extensively been employed for various sensors and actuators applications. In this paper, the state-of-art in piezoelectric single crystals for ultrasonic transducer applications is reviewed. Firstly, the basic principles and design considerations of piezoelectric ultrasonic transducers will be addressed. Then, the popular piezoelectric single crystals used for ultrasonic transducer applications, including LiNbO3 (LN), PMN-PT and PIN-PMN-PT, will be introduced. After describing the preparation and performance of the single crystals, the recent development of both the single-element and array transducers fabricated using the single crystals will be presented. Finally, various biomedical applications including eye imaging, intravascular imaging, blood flow measurement, photoacoustic imaging, and microbeam applications of the single crystal transducers will be discussed. PMID:25386032

Zhou, Qifa; Lam, Kwok Ho; Zheng, Hairong; Qiu, Weibao; Shung, K Kirk

2014-10-01

116

High-Temperature Piezoelectric Sensing  

PubMed Central

Piezoelectric sensing is of increasing interest for high-temperature applications in aerospace, automotive, power plants and material processing due to its low cost, compact sensor size and simple signal conditioning, in comparison with other high-temperature sensing techniques. This paper presented an overview of high-temperature piezoelectric sensing techniques. Firstly, different types of high-temperature piezoelectric single crystals, electrode materials, and their pros and cons are discussed. Secondly, recent work on high-temperature piezoelectric sensors including accelerometer, surface acoustic wave sensor, ultrasound transducer, acoustic emission sensor, gas sensor, and pressure sensor for temperatures up to 1,250 °C were reviewed. Finally, discussions of existing challenges and future work for high-temperature piezoelectric sensing are presented. PMID:24361928

Jiang, Xiaoning; Kim, Kyungrim; Zhang, Shujun; Johnson, Joseph; Salazar, Giovanni

2014-01-01

117

Frequency modulated (FM) time delay photoacoustic and photothermal wave spectroscopies. Technique, instrumentation, and detection. Part I: Theoretical  

Microsoft Academic Search

A conceptual basis for the technique of time delay photothermal wave spectroscopy is presented. The signal generation and appropriate system functions in the time delay and frequency domains are introduced and discussed from the point of view of correlation and spectral analysis and processing.

Andreas Mandelis

1986-01-01

118

Photoacoustic Study of Fungal Disease of Acai ( Euterpe oleracea ) Seeds  

Microsoft Academic Search

Photoacoustic spectroscopy is introduced as a promising experimental technique to investigate fungus infected Acai (Euterpe oleracea) seeds. Photoacoustic spectra of healthy and infected Acai seeds with the fungus Colletotrichum gloeosporioides were recorded firstly in the modulation frequency range of 5Hz to 700 Hz, while keeping the wavelength of excitation radiation\\u000a of a Xe arc-lamp constant, to ascertain the depth of penetration

Denise V. Rezende; O. A. C. Nunes; A. C. Oliveira

2009-01-01

119

Photoacoustic determination of small optical absorption coefficients: extended theory.  

PubMed

Photoacoustic measurement of small absorption coefficients provides an important alternative to standard techniques. The theoretical basis for such measurements is extended to include the effects of thermally generated mechanical motion of the sample, by incorporating the thermoelastic equations for an isotropicm solid in a cylindrical configuration. Sample calculations show that this thermoacoustic effect may dominate the photoacoustic signal for certain modulation frequencies and beam configurations. PMID:20212851

Alan McDonald, F

1979-05-01

120

Prototyping of radially oriented piezoelectric ceramic-polymer tube composites using fused deposition and lost mold processing techniques  

NASA Astrophysics Data System (ADS)

Piezoelectric tube composite hydrophones of 3-1, 3-2, and 2-2 connectivity were developed using Fused Deposition (FD) and lost mold processing (LMP). In this work, a new series of thermoplastic binder formulations, named the ECG series, were developed for the FD process. The ECG-9 formulation exhibits mechanical, thermal, and rheological properties suitable for the Fused Deposition of functional lead zirconate titanate ceramic devices. This binder consists of 100 parts (by weight) Vestoplast 408, 20 parts Escorez 2520, 15 parts Vestowax A-227, and 5 parts Indopol H-1500. Oleic acid, oleyl alcohol, stearic acid, and stearyl alcohol (in toluene) were tested for use as a dispersant in the PZT/ECG-9 system. It was found that stearic acid adsorbs the most onto PZT powder, adsorbing 8.1 mg/m2. Using stearic acid, solutions of increasing concentration (5.0--50.0 g/l) were measured for adsorption. It was found that 30.0 g/l is the minimum concentration necessary for optimum surface coverage. The surfactant-coated powder was compounded with ECG-9 binder to create a 54 vol.% mix. The mix was extruded using a single screw extrusion apparatus into continuous lengths (>30 m) of 1.78 mm diameter filament. Fused Deposition was used to create composite designs of 3-1, 3-2, and 2-2 connectivity. After sintering, samples exhibit a sintered density greater than 97%. Sanders Prototyping (SPI) was used to manufacture molds for use with LMP techniques. Molds of 3-1, 3-2, and 2-2 connectivity were developed. The molds were infiltrated with a 55 vol.% aqueous based PZT slurry. The parts were subjected to a binder decomposition cycle, followed by sintering. Resultant samples were highly variable due to random macro-pores present in the samples after sintering. The resultant preforms were embedded in epoxy, and polished to dimensions of 8.0 mm inside diameter (ID), 14.0 mm outside diameter (OD), and 10.0 mm length (l) the OD and l dimensions are accurate to +/--2%, while the ID is accurate to +/--5%. Samples were corona poled, and the electromechanical properties were evaluated. Dielectric constant (K), hydrostatic charge coefficients (dh), and radial displacements (ur) were measured. Of the seven composite types studied, the FD-based composites with 3-2 connectivity exhibited the highest average dh of 42.4 pCN. The same 3-2 composites exhibited the highest dhgh (FOM) of 140 fm2/N.

McNulty, Thomas Francis

121

Computationally intelligent pulsed photoacoustics  

NASA Astrophysics Data System (ADS)

In this paper, the application of computational intelligence in pulsed photoacoustics is discussed. Feedforward multilayer perception networks are applied for real-time simultaneous determination of the laser beam spatial profile and vibrational-to-translational relaxation time of the polyatomic molecules in gases. Networks are trained and tested with theoretical data adjusted for a given experimental set-up. Genetic optimization has been used for calculation of the same parameters, fitting the photoacoustic signals with a different number of generations. Observed benefits from the application of computational intelligence in pulsed photoacoustics and advantages over previously developed methods are discussed, such as real-time operation, high precision and the possibility of finding solutions in a wide range of parameters, similar to in experimental conditions. In addition, the applicability for practical uses, such as the real-time in situ measurements of atmospheric pollutants, along with possible further developments of obtained results, is argued.

Luki?, Mladena; ?ojbaši?, Žarko; Rabasovi?, Mihailo D.; Markushev, Dragan D.

2014-12-01

122

Stimulated Raman photoacoustic imaging.  

PubMed

Achieving label-free, molecular-specific imaging with high spatial resolution in deep tissue is often considered the grand challenge of optical imaging. To accomplish this goal, significant optical scattering in tissues has to be overcome while achieving molecular specificity without resorting to extrinsic labeling. We demonstrate the feasibility of developing such an optical imaging modality by combining the molecularly specific stimulated Raman excitation with the photoacoustic detection. By employing two ultrashort excitation laser pulses, separated in frequency by the vibrational frequency of a targeted molecule, only the specific vibrational level of the target molecules in the illuminated tissue volume is excited. This targeted optical absorption generates ultrasonic waves (referred to as stimulated Raman photoacoustic waves) which are detected using a traditional ultrasonic transducer to form an image following the design of the established photoacoustic microscopy. PMID:21059930

Yakovlev, Vladislav V; Zhang, Hao F; Noojin, Gary D; Denton, Michael L; Thomas, Robert J; Scully, Marlan O

2010-11-23

123

Photoacoustic flow cytometry.  

PubMed

Conventional flow cytometry using scattering and fluorescent detection methods has been a fundamental tool of biological discoveries for many years. Invasive extraction of cells from a living organism, however, may lead to changes in cell properties and prevents the long-term study of cells in their native environment. Here, we summarize recent advances of new generation flow cytometry for in vivo noninvasive label-free or targeted detection of cells in blood, lymph, bone, cerebral and plant vasculatures using photoacoustic (PA) detection techniques, multispectral high-pulse-repetition-rate lasers, tunable ultrasharp (up to 0.8 nm) rainbow plasmonic nanoprobes, positive and negative PA contrasts, in vivo magnetic enrichment, time-of-flight cell velocity measurement, PA spectral analysis, and integration of PA, photothermal (PT), fluorescent, and Raman methods. Unique applications of this tool are reviewed with a focus on ultrasensitive detection of normal blood cells at different functional states (e.g., apoptotic and necrotic) and rare abnormal cells including circulating tumor cells (CTCs), cancer stem cells, pathogens, clots, sickle cells as well as pharmokinetics of nanoparticles, dyes, microbubbles and drug nanocarriers. Using this tool we discovered that palpation, biopsy, or surgery can enhance CTC release from primary tumors, increasing the risk of metastasis. The novel fluctuation flow cytometry provided the opportunity for the dynamic study of blood rheology including red blood cell aggregation and clot formation in different medical conditions (e.g., blood disorders, cancer, or surgery). Theranostics, as a combination of PA diagnosis and PT nanobubble-amplified multiplex therapy, was used for eradication of CTCs, purging of infected blood, and thrombolysis of clots using PA guidance to control therapy efficiency. In vivo flow cytometry using a portable fiber-based devices can provide a breakthrough platform for early diagnosis of cancer, infection and cardiovascular disorders with a potential to inhibit, if not prevent, metastasis, sepsis, and strokes or heart attack by well-timed personalized therapy. PMID:22749928

Galanzha, Ekaterina I; Zharov, Vladimir P

2012-07-01

124

A non-contact and online ink thickness sensor for printing machines using the photoacoustic effect  

Microsoft Academic Search

We have developed an ink thickness sensor by employing a photoacoustic technique in order to enable the online measurement of ink thickness for printing machines such as a sheet-fed press. This sensor enables the online measurement of black ink thickness, which was impossible using the conventional methods. In order to detect the photoacoustic signals from the ink on a rotating

Koichi Kurita

2008-01-01

125

Photoacoustic frequency-domain depth profiling of contintiouslly inhomogeneous condensed phases: Theory and simulations  

E-print Network

Photoacoustic frequency-domain depth profiling of contintiouslly inhomogeneous condensed phases: Theory and simulations for the inverse problem Andreas Mandelisa) and Samuel B. Peralta Photoacoustic) capabilities of this technique. Even though much experimental workI and some theoretical models215have been

Mandelis, Andreas

126

Piezoelectric transducer  

NASA Technical Reports Server (NTRS)

Transducer consists of a hybrid thin film and a piezoelectric transistor that acts as a stress-sensitive device with built-in gain. It provides a stress/strain transducer that incorporates a signal amplification stage and sensor in a single package.

Conragan, J.; Muller, R. S.

1970-01-01

127

Catheter-based photoacoustic endoscope  

NASA Astrophysics Data System (ADS)

We report a flexible shaft-based mechanical scanning photoacoustic endoscopy (PAE) system that can be potentially used for imaging the human gastrointestinal tract via the instrument channel of a clinical video endoscope. The development of such a catheter endoscope has been an important challenge to realize the technique's benefits in clinical settings. We successfully implemented a prototype PAE system that has a 3.2-mm diameter and 2.5-m long catheter section. As the instrument's flexible shaft and scanning tip are fully encapsulated in a plastic catheter, it easily fits within the 3.7-mm diameter instrument channel of a clinical video endoscope. Here, we demonstrate the intra-instrument channel workability and in vivo animal imaging capability of the PAE system.

Yang, Joon-Mo; Li, Chiye; Chen, Ruimin; Zhou, Qifa; Shung, K. Kirk; Wang, Lihong V.

2014-06-01

128

Photoacoustic effect as a liquid absorbance detector  

Microsoft Academic Search

A theoretical treatment of the photoacoustic effect for a liquid enclosed in a cylindrical cell is given. Simple analytical expressions for the photoacoustic signal are derived for CW and pulse modulation schemes. Modulation frequency or pulse width dependence of the photoacoustic signal is discussed. For the CW modulation scheme it is found that more photoacoustic power is generated in a

Abdullah Atalar

1980-01-01

129

Quartz-Enhanced Photoacoustic Spectroscopy: A Review  

PubMed Central

A detailed review on the development of quartz-enhanced photoacoustic sensors (QEPAS) for the sensitive and selective quantification of molecular trace gas species with resolved spectroscopic features is reported. The basis of the QEPAS technique, the technology available to support this field in terms of key components, such as light sources and quartz-tuning forks and the recent developments in detection methods and performance limitations will be discussed. Furthermore, different experimental QEPAS methods such as: on-beam and off-beam QEPAS, quartz-enhanced evanescent wave photoacoustic detection, modulation-cancellation approach and mid-IR single mode fiber-coupled sensor systems will be reviewed and analysed. A QEPAS sensor operating in the THz range, employing a custom-made quartz-tuning fork and a THz quantum cascade laser will be also described. Finally, we evaluated data reported during the past decade and draw relevant and useful conclusions from this analysis. PMID:24686729

Patimisco, Pietro; Scamarcio, Gaetano; Tittel, Frank K.; Spagnolo, Vincenzo

2014-01-01

130

Quartz-enhanced photoacoustic spectroscopy: a review.  

PubMed

A detailed review on the development of quartz-enhanced photoacoustic sensors (QEPAS) for the sensitive and selective quantification of molecular trace gas species with resolved spectroscopic features is reported. The basis of the QEPAS technique, the technology available to support this field in terms of key components, such as light sources and quartz-tuning forks and the recent developments in detection methods and performance limitations will be discussed. Furthermore, different experimental QEPAS methods such as: on-beam and off-beam QEPAS, quartz-enhanced evanescent wave photoacoustic detection, modulation-cancellation approach and mid-IR single mode fiber-coupled sensor systems will be reviewed and analysed. A QEPAS sensor operating in the THz range, employing a custom-made quartz-tuning fork and a THz quantum cascade laser will be also described. Finally, we evaluated data reported during the past decade and draw relevant and useful conclusions from this analysis. PMID:24686729

Patimisco, Pietro; Scamarcio, Gaetano; Tittel, Frank K; Spagnolo, Vincenzo

2014-01-01

131

Virus-based piezoelectric energy generation  

NASA Astrophysics Data System (ADS)

Piezoelectric materials can convert mechanical energy into electrical energy, and piezoelectric devices made of a variety of inorganic materials and organic polymers have been demonstrated. However, synthesizing such materials often requires toxic starting compounds, harsh conditions and/or complex procedures. Previously, it was shown that hierarchically organized natural materials such as bones, collagen fibrils and peptide nanotubes can display piezoelectric properties. Here, we demonstrate that the piezoelectric and liquid-crystalline properties of M13 bacteriophage (phage) can be used to generate electrical energy. Using piezoresponse force microscopy, we characterize the structure-dependent piezoelectric properties of the phage at the molecular level. We then show that self-assembled thin films of phage can exhibit piezoelectric strengths of up to 7.8 pm V-1. We also demonstrate that it is possible to modulate the dipole strength of the phage, hence tuning the piezoelectric response, by genetically engineering the major coat proteins of the phage. Finally, we develop a phage-based piezoelectric generator that produces up to 6 nA of current and 400 mV of potential and use it to operate a liquid-crystal display. Because biotechnology techniques enable large-scale production of genetically modified phages, phage-based piezoelectric materials potentially offer a simple and environmentally friendly approach to piezoelectric energy generation.

Lee, Byung Yang; Zhang, Jinxing; Zueger, Chris; Chung, Woo-Jae; Yoo, So Young; Wang, Eddie; Meyer, Joel; Ramesh, Ramamoorthy; Lee, Seung-Wuk

2012-06-01

132

Lifetime-based photoacoustic oxygen sensing in vivo  

PubMed Central

Abstract. The determination of oxygen levels in blood and other tissues in vivo is critical for ensuring proper body functioning, for monitoring the status of many diseases, such as cancer, and for predicting the efficacy of therapy. Here we demonstrate, for the first time, a lifetime-based photoacoustic technique for the measurement of oxygen in vivo, using an oxygen sensitive dye, enabling real time quantification of blood oxygenation. The results from the main artery in the rat tail indicated that the lifetime of the dye, quantified by the photoacoustic technique, showed a linear relationship with the blood oxygenation levels in the targeted artery. PMID:22612143

Ray, Aniruddha; Rajian, Justin Rajesh; Lee, Yong-Eun Koo; Wang, Xueding; Kopelman, Raoul

2012-01-01

133

Laser-induced photoacoustic spectroscopy investigation of colon phantom tissue  

Microsoft Academic Search

This paper discusses laser-induced photoacoustic investigations; it concerns a non-destructive technique for the determination\\u000a of the thermal diffusivity of colon phantom tissue employing open photoacoustic cell configuration.\\u000a \\u000a \\u000a The theoretical value of thermal diffusivity is determined to be 5.65×10?4 m2?s?1 and found to be comparable with other conventional thermal-diffusivity measurement techniques such as laser flash method.\\u000a The results obtained provide the evidence

James Joseph; Krishnan Sathiyamoorthy; T. Visalatchi; V. M. Murukeshan; Lye Sun Woh

2010-01-01

134

Sensitivity of photoacoustic microscopy  

PubMed Central

Building on its high spatial resolution, deep penetration depth and excellent image contrast, 3D photoacoustic microscopy (PAM) has grown tremendously since its first publication in 2005. Integrating optical excitation and acoustic detection, PAM has broken through both the optical diffusion and optical diffraction limits. PAM has 100% relative sensitivity to optical absorption (i.e., a given percentage change in the optical absorption coefficient yields the same percentage change in the photoacoustic amplitude), and its ultimate detection sensitivity is limited only by thermal noise. Focusing on the engineering aspects of PAM, this Review discusses the detection sensitivity of PAM, compares the detection efficiency of different PAM designs, and summarizes the imaging performance of various endogenous and exogenous contrast agents. It then describes representative PAM applications with high detection sensitivity, and outlines paths to further improvement. PMID:25302158

Yao, Junjie; Wang, Lihong V.

2014-01-01

135

Photoacoustic spectroscopy for analytical measurements  

NASA Astrophysics Data System (ADS)

Many different techniques, such as UV/vis absorption, IR spectroscopy, fluorescence and Raman spectroscopy are routinely applied in chemical (micro-)analysis and chemical imaging, and a large variety of instruments is commercially available. Up to now, opto- or photoacoustic (PA) and other optothermal (OT) methods are less common and only a limited number of instruments reached a level of application beyond prototypes in research laboratories. The underlying principle of all these techniques is the detection of local heating due to the conversion of light into heat by optical absorption. Considering the versatility, robustness and instrumental simplicity of many PA techniques, it is surprising that the number of commercial instruments based on such approaches is so sparse. The impetus of this review is to summarize basic principles and possible applications described in the literature, in order to foster routine application of these techniques in industry, process analysis and environmental screening. While the terms OT and PA methods cover a very wide range of methods and physical phenomena, this review will concentrate on techniques with applications for analytical measurements.

Haisch, Christoph

2012-01-01

136

Nondestructive evaluation of structural ceramics by photoacoustic microscopy  

NASA Technical Reports Server (NTRS)

A photoacoustic microscopy (PAM) digital imaging system was developed and utilized to characterize silicon nitride material at the various stages of the ceramic fabrication process. Correlation studies revealed that photoacoustic microscopy detected failure initiating defects in substantially more specimens than microradiography and ultrasonic techniques. Photoacoustic microscopy detected 10 to 100 micron size surface and subsurface pores and inclusions, respectively, up to 80 microns below the interrogating surface in machined sintered silicon nitride. Microradiography detected 50 micron diameter fracture controlling pores and inclusions. Subsurface holes were detected up to a depth of 570 microns and 1.00 mm in sintered silicon nitride and silicon carbide, respectively. Seeded voids of 20 to 30 micron diameters at the surface and 50 microns below the interrogating surface were detected by photoacoustic microscopy and microradiography with 1 percent X-ray thickness sensitivity. Tight surface cracks of 96 micron length x 48 micron depth were detected by photoacoustic microscopy. PAM volatilized and removed material in the green state which resulted in linear shallow microcracks after sintering. This significantly limits the use of PAM as an in-process NDE technique.

Khandelwal, Pramod K.

1987-01-01

137

Theoretical aspects of photoacoustic spectroscopy  

Microsoft Academic Search

The exact form of the Rosencwaig-Gersho theory for the photoacoustic effect in solids is used to depict how the magnitude and phase of the photoacoustic signal vary with chopping frequency and normalized length. Applications of the theory to studies of film-substrate systems are discussed.

Allan Rosencwaig

1978-01-01

138

Thermally Induced Photoacoustic Transients Produced by Laser-Irradiated Fluid Spheres  

NASA Astrophysics Data System (ADS)

Pulsed laser irradiation of a weakly absorbing fluid sphere in a transparent medium results in the production of a large thermal gradient at the surface of the sphere. The rapid transfer of heat from the sphere to the surrounding fluid as a result of the thermal gradient generates high frequency photoacoustic transients which affect the leading edge of a photoacoustic wave. Here, the character of the photoacoustic wave is determined by solving a modified wave equation for the photoacoustic effect. A solution to the heat diffusion equation is determined, which, together with the heating function for the optical source, provides the source term for the wave equation for pressure. The wave equation is then solved with appropriate boundary conditions using Laplace transform techniques to give the photoacoustic waveform. The relative magnitude of the transient to the N-shaped wave is shown to be determined, in part, by the laser pulse length.

Frez, Clifford; Diebold, Gerald J.

2014-12-01

139

Ultrasound-heated photoacoustic flowmetry  

PubMed Central

Abstract. We report the development of photoacoustic flowmetry assisted by high-intensity focused ultrasound (HIFU). This novel method employs HIFU to generate a heating impulse in the flow medium, followed by photoacoustic monitoring of the thermal decay process. Photoacoustic flowmetry in a continuous medium remains a challenge in the optical diffusive regime. Here, both the HIFU heating and photoacoustic detection can focus at depths beyond the optical diffusion limit (?1??mm in soft tissue). This method can be applied to a continuous medium, i.e., a medium without discrete scatterers or absorbers resolvable by photoacoustic imaging. Flow speeds up to 41??mm·s?1 have been experimentally measured in a blood phantom covered by 1.5-mm-thick tissue. PMID:24194064

Wang, Lidai; Yao, Junjie; Maslov, Konstantin I.; Xing, Wenxin; Wang, Lihong V.

2013-01-01

140

Photoacoustic detection of breast cancer cells in human blood  

NASA Astrophysics Data System (ADS)

Detection of breast cancer cells in human blood may provide early determination of metastasis, enabling aggressive treatment prior to detection by conventional radiographic methods. We developed a photoacoustic flowmetry system in which we irradiated breast cancer cells in suspension to simulate metastatic breast cancer cells derived from human blood. In order to provide optical discrimination between the breast cancer cells and lymphocytes, we attached antibody labeled latex microspheres and gold nanoparticles to breast cancer cells. The breast cancer cells were derived from an estrogen receptor (ER) positive cell line, MCF-7. The particles were conjugated to ER antibodies. We irradiated the cell suspension using the photoacoustic flowmeter consisting of a glass flow chamber with a piezoelectric sensor. We irradiated the suspension at 422 and 530nm and solved a linear system of equations in two variables to separate the contribution of the photoacoustic wave from the breast cancer cells and possible erythrocytes that may be present in a patient blood draw. We found a detection threshold of 10 breast cancer cells using this flowmeter. Future optimization of the system may decrease the detection threshold to single breast cancer cells.

Thomas, T. S.; Dale, P. S.; Weight, R. M.; Atasoy, Ulus; Magee, J.; Viator, J. A.

2008-02-01

141

Comparison of electrostatic fins with piezoelectric impact hammer techniques to extend impulse calibration range of a torsional thrust stand.  

PubMed

With the progression of high-power electric propulsion and high thrust-to-power propulsions system, thrust stand diagnostics require high-fidelity calibration systems that are accurate over a large-range of thrust levels. Multi-mode and variable I(sp) propulsion devices also require that a single stand be capable of measuring thrust from 10's of uNs to 100's of mNs. While the torsional thrust stand mechanic and diagnostics are capable of operating over such a large range, current pulsed calibration schemes are typically limited to a few orders of magnitude of dynamic range. In order to develop a stand with enough dynamic range, two separate calibration methods have been examined and compared to create a combined system. Electrostatic fin (ESF) and piezoelectric impact hammer (PIH) calibration systems were simultaneously tested on a large scale torsional thrust stand system. The use of the these two methods allowed the stand to be calibrated over four orders of magnitude, from 0.01 mNs to 750 mNs. The ESF system produced linear results within 0.52% from 0.01 mNs to 20 mNs, while the PIH system extended this calibration range from 10 mNs to 750 mNs with an error of 0.99%. The two calibration methods agreed within 4.51% over their overlapping range of 10-20 mNs. PMID:22462962

Pancotti, Anthony P; Gilpin, Matthew; Hilario, Martin S

2012-03-01

142

Comparison of electrostatic fins with piezoelectric impact hammer techniques to extend impulse calibration range of a torsional thrust stand  

NASA Astrophysics Data System (ADS)

With the progression of high-power electric propulsion and high thrust-to-power propulsions system, thrust stand diagnostics require high-fidelity calibration systems that are accurate over a large-range of thrust levels. Multi-mode and variable Isp propulsion devices also require that a single stand be capable of measuring thrust from 10's of uNs to 100's of mNs. While the torsional thrust stand mechanic and diagnostics are capable of operating over such a large range, current pulsed calibration schemes are typically limited to a few orders of magnitude of dynamic range. In order to develop a stand with enough dynamic range, two separate calibration methods have been examined and compared to create a combined system. Electrostatic fin (ESF) and piezoelectric impact hammer (PIH) calibration systems were simultaneously tested on a large scale torsional thrust stand system. The use of the these two methods allowed the stand to be calibrated over four orders of magnitude, from 0.01 mNs to 750 mNs. The ESF system produced linear results within 0.52% from 0.01 mNs to 20 mNs, while the PIH system extended this calibration range from 10 mNs to 750 mNs with an error of 0.99%. The two calibration methods agreed within 4.51% over their overlapping range of 10-20 mNs.

Pancotti, Anthony P.; Gilpin, Matthew; Hilario, Martin S.

2012-03-01

143

Photoacoustic spectroscopic differences between normal and malignant thyroid tissues  

NASA Astrophysics Data System (ADS)

The thyroid is one of the main endocrine glands of human body, which plays a crucial role in the body's metabolism. Thyroid cancer mortality ranks only second to ovarian cancer in endocrine cancer. Routine diagnostic methods of thyroid diseases in present clinic exist misdiagnosis and missed diagnosis to varying degrees. Those lead to miss the best period of cancer treatment--early. Photoacoustic spectroscopy technology is a new tool, which provides an effective and noninvasive way for biomedical materials research, being highly sensitive and without sample pretreatment. In this paper, we use photoacoustic spectroscopy technology (PAST) to detect the absorption spectrum between normal and malignant thyroid tissues. The result shows that the photoacoustic spectroscopy technology (PAST) could differentiate malignant thyroid tissue from normal thyroid tissue very well. This technique combined with routine diagnostic methods has the potential to increase the diagnostic accuracy in clinical thyroid cancer diagnosis.

Li, Li; Xie, Wengming; Li, Hui

2012-12-01

144

Development of a breadboard CO2 laser photoacoustic toxic vapor monitor. Project summary  

SciTech Connect

The report describes the development of a breadboard version of CO2 laser photoacoustic detector. The CO2 laser photoacoustic technique has been demonstrated to be capable of detecting, with high specificity, a variety of toxic compounds a low parts-per-billion (ppb) levels in multicomponent air samples. The technique can be used for monitoring trace levels of various hazardous compounds in ambient air samples.

Loper, G.L.; Corbin, R.C.; Takayama, M.L.; Clifton, R.A.; Gelbwachs, J.A.

1988-11-01

145

Piezoelectric Effect  

NSDL National Science Digital Library

In this activity, by the Concord Consortium's Molecular Literacy project, students explore the piezoelectric effect, which is the conversion between electricity and mechanical motion. The model used in this activity shows this conversion and users can manipulate the model to change the voltage and observe changes to a crystal. The activity itself is a java-based interactive resource built upon the free, open source Molecular Workbench software. In these activities, students are allowed to explore at their own pace in a digital environment full of demonstrations, illustrations, and models they can manipulate. In addition to the activity, visitors will find an overview of the activity and central and key concepts.

2008-10-23

146

Neurovascular Photoacoustic Tomography  

PubMed Central

Neurovascular coupling refers to the relationship between neuronal activities and downstream hemodynamic responses. Photoacoustic tomography (PAT), enabling comprehensive label-free imaging of hemodynamic activities with highly scalable penetration and spatial resolution, has great potential in the study of neurovascular coupling. In this review, we first introduce the technical basis of hemodynamic PAT – including label-free quantification of total hemoglobin concentration, blood oxygenation, and blood flow – as well as its applications in hemodynamic monitoring. Then, we demonstrate the potential application of PAT in neurovascular imaging by highlighting representative studies on cerebral vascular responses to whisker stimulation and Alzheimer's disease. Finally, potential research directions and associated technical challenges are discussed. PMID:20616885

Hu, Song; Wang, Lihong V.

2010-01-01

147

A proposal to localize an intraocular melanoma by photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

A method of laser-induced photoacoustic spectroscopic imaging (LIPASI) and its possible applications in biological research are described. Possible applications of this method include diagnosis of an intraocular malignant melanoma and cardial infarcts. A comparison is made between LIPASI and the normal ultrasonic imaging technique and the advantages of LIPASI are emphasized.

Wolbarsht, M. L.

1981-12-01

148

Photoacoustic procedure for measuring thermal parameters of transparent solids  

Microsoft Academic Search

An application of photoacoustic technique is developed for determining the thermal diffusivity coefficient and the thermal conductivity of transparent materials. The backing material which supports the sample is made optically opaque, i.e., it entirely absorbs the incident light, and the converted heat diffuses through the sample heating the gas in contact with its opposite surface. The method is illustrated by

W. L. Barros Melo; R. M. Faria

1995-01-01

149

Label-free photoacoustic nanoscopy  

NASA Astrophysics Data System (ADS)

Super-resolution microscopy techniques-capable of overcoming the diffraction limit of light-have opened new opportunities to explore subcellular structures and dynamics not resolvable in conventional far-field microscopy. However, relying on staining with exogenous fluorescent markers, these techniques can sometimes introduce undesired artifacts to the image, mainly due to large tagging agent sizes and insufficient or variable labeling densities. By contrast, the use of endogenous pigments allows imaging of the intrinsic structures of biological samples with unaltered molecular constituents. Here, we report label-free photoacoustic (PA) nanoscopy, which is exquisitely sensitive to optical absorption, with an 88 nm resolution. At each scanning position, multiple PA signals are successively excited with increasing laser pulse energy. Because of optical saturation or nonlinear thermal expansion, the PA amplitude depends on the nonlinear incident optical fluence. The high-order dependence, quantified by polynomial fitting, provides super-resolution imaging with optical sectioning. PA nanoscopy is capable of super-resolution imaging of either fluorescent or nonfluorescent molecules.

Danielli, Amos; Maslov, Konstantin; Garcia-Uribe, Alejandro; Winkler, Amy M.; Li, Chiye; Wang, Lidai; Chen, Yun; Dorn, Gerald W.; Wang, Lihong V.

2014-08-01

150

Characterization of integrating ultrasound detectors for photoacoustic tomography  

NASA Astrophysics Data System (ADS)

Photoacoustic tomography is based on generation of sound waves in a semitransparent medium by illumination with short light pulses. In standard methods, measurements of the acoustic waves around the sample with point like ultrasound detectors are used for reconstruction of the distribution of absorbed energy, which contains information on light-absorbing structures such as blood vessels in tissue. Integrating ultrasound detectors are planes or lines larger than the imaged object and measure temporal signals that are given by spatial integrals over the sound field. It can be shown that such integrated signals give exact reconstructions with constant, high resolution throughout the imaging zone. The goal of the present study was to investigate with the help of simulations and experiments how far real implementations of integrating detectors based on piezoelectric films or optical interferometry have characteristics approximating those of ideal planes or lines. It is shown that the directive sensitivity of piezoelectric films tends to distort signals, mainly in the case of large area detectors. This distortion can, on the other hand, be used to directly measure a part of the directivity that is caused by distribution of stress components in the detector. Optical beams as part of an interferometer have omnidirectional response, but need focusing in order to achieve high temporal and spatial resolution. For example, with a beam focused to a diameter of 38 ?m a spatial image resolution of 52 ?m could be observed. Because of the beam waist, this resolution can only be achieved for acoustic sources lying within a range corresponding to the focal depth of the beam. It is concluded that line detectors made of piezoelectric thin films yield almost ideal performance for acoustic waves at normal incidence. Even better suited for photoacoustic tomography are focused optical beams as line detectors due to their omnidirectional response and higher signal to noise ratio, but only for objects with a size smaller than the focal depth.

Paltauf, G.; Nuster, R.; Burgholzer, P.

2009-05-01

151

Measurement of cardiac output by use of noninvasively measured transient hemodilution curves with photoacoustic technology  

PubMed Central

We present the theoretical basis and experimental verification for cardiac output measurements using noninvasively measured hemodilution curves afforded with an indicator dilution technique and the emerging photoacoustic technology. A photoacoustic system noninvasively tracks a transient hemodilution effect induced by a bolus of isotonic saline as an indicator. As a result, a photoacoustic indicator dilution curve is obtained, which allows to estimate cardiac output from the developed algorithm. The experiments with a porcine blood circulatory phantom system demonstrated the feasibility of this technology towards the development of a noninvasive cardiac output measurement system for patient monitoring. PMID:24877007

Kang, Dongyel; Huang, Qiaojian; Li, Youzhi

2014-01-01

152

Measurement of cardiac output by use of noninvasively measured transient hemodilution curves with photoacoustic technology.  

PubMed

We present the theoretical basis and experimental verification for cardiac output measurements using noninvasively measured hemodilution curves afforded with an indicator dilution technique and the emerging photoacoustic technology. A photoacoustic system noninvasively tracks a transient hemodilution effect induced by a bolus of isotonic saline as an indicator. As a result, a photoacoustic indicator dilution curve is obtained, which allows to estimate cardiac output from the developed algorithm. The experiments with a porcine blood circulatory phantom system demonstrated the feasibility of this technology towards the development of a noninvasive cardiac output measurement system for patient monitoring. PMID:24877007

Kang, Dongyel; Huang, Qiaojian; Li, Youzhi

2014-05-01

153

Using Diffusion Bonding in Making Piezoelectric Actuators  

NASA Technical Reports Server (NTRS)

A technique for the fabrication of piezoelectric actuators that generate acceptably large forces and deflections at relatively low applied voltages involves the stacking and diffusion bonding of multiple thin piezoelectric layers coated with film electrodes. The present technique stands in contrast to an older technique in which the layers are bonded chemically, by use of urethane or epoxy agents. The older chemical-bonding technique entails several disadvantages, including the following: It is difficult to apply the bonding agents to the piezoelectric layers. It is difficult to position the layers accurately and without making mistakes. There is a problem of disposal of hazardous urethane and epoxy wastes. The urethane and epoxy agents are nonpiezoelectric materials. As such, they contribute to the thickness of a piezoelectric laminate without contributing to its performance; conversely, for a given total thickness, the performance of the laminate is below that of a unitary piezoelectric plate of the same thickness. The figure depicts some aspects of the fabrication of a laminated piezoelectric actuator by the present diffusion- bonding technique. First, stock sheets of the piezoelectric material are inspected and tested. Next, the hole pattern shown in the figure is punched into the sheets. Alternatively, if the piezoelectric material is not a polymer, then the holes are punched in thermoplastic films. Then both faces of each punched piezoelectric sheet or thermoplastic film are coated with a silver-ink electrode material by use of a silkscreen printer. The electrode and hole patterns are designed for minimal complexity and minimal waste of material. After a final electrical test, all the coated piezoelectric layers (or piezoelectric layers and coated thermoplastic films) are stacked in an alignment jig, which, in turn, is placed in a curved press for the diffusion-bonding process. In this process, the stack is pressed and heated at a specified curing temperature and pressure for a specified curing time. The pressure, temperature, and time depend on the piezoelectric material selected. At the end of the diffusion-bonding process, the resulting laminated piezoelectric actuator is tested to verify the adequacy of the mechanical output as a function of an applied DC voltage.

Sager, Frank E.

2003-01-01

154

Functional photoacoustic tomography of animal brains  

E-print Network

This research is primarily focused on laser-based non-invasive photoacoustic tomography of small animal brains. Photoacoustic tomography, a novel imaging modality, was applied to visualize the distribution of optical absorptions in small...

Wang, Xueding

2005-11-01

155

An experimental and theoretical approach to the study of the photoacoustic signal produced by cancer cells  

NASA Astrophysics Data System (ADS)

The distinctive spectral absorption characteristics of cancer cells make photoacoustic techniques useful for detection in vitro and in vivo. Here we report on our evaluation of the photoacoustic signal produced by a series of monolayers of different cell lines in vitro. Only the melanoma cell line HS936 produced a detectable photoacoustic signal in which amplitude was dependent on the number of cells. This finding appears to be related to the amount of melanin available in these cells. Other cell lines (i.e. HL60, SK-Mel-1, T47D, Hela, HT29 and PC12) exhibited values similar to a precursor of melanin (tyrosinase), but failed to produce sufficient melanin to generate a photoacoustic signal that could be distinguished from background noise. To better understand this phenomenon, we determined a formula for the time-domain photoacoustic wave equation for a monolayer of cells in a non-viscous fluid on the thermoelastic regime. The theoretical results showed that the amplitude and profile of the photoacoustic signal generated by a cell monolayer depended upon the number and distribution of the cells and the location of the point of detection. These findings help to provide a better understanding of the factors involved in the generation of a photoacoustic signal produced by different cells in vitro and in vivo.

Solano, Rafael Pérez; Ramirez-Perez, Francisco I.; Castorena-Gonzalez, Jorge A.; Anell, Edgar Alvarado; Gutiérrez-Juárez, Gerardo; Polo-Parada, Luis

2012-03-01

156

Open-ended photoacoustic cells:? application to two-layer samples using pulse laser-induced photoacoustics.  

PubMed

To measure the difference between samples in situ, two types of open-ended photoacoustic cells were constructed. One type was a differential open-ended photoacoustic cell with a differential microphone, which connected two equivalent open-ended cell chambers through two waveguides. The other design used single open-ended photoacoustic cell chambers, each with an electric condenser microphone. A pair of these was used to suppress background signal by subtraction of the signals. The performance of these cells was compared to that of a conventional photoacoustic apparatus with a chopper. Detection limits of Sudan red for those cells were about 1.29 and 2.35 ng for a differential open-ended cell and a single open-ended cell, respectively. The photoacoustic cells were then applied to the pulse mode operation, using a nitrogen laser as a pulse light source. The laser beams were led to the photoacoustic cells through quartz optical fibers. Using this instrument setup, depth profiling analysis was carried out for two-layer samples made of poly(methyl methacrylate) (PMMA) or polystyrene (PS) films. A linear relationship was obtained between the signal delay time and the film thickness. The delay time of the signal (?) was expressed in terms of the thermal diffusivity (?/cm(2) s(-)(1)) of the film as ? (ms) ? (2.25 × 10(-3)) x (?m) ?(-1/2). The method was successful in measuring the thickness of transparent surface layers. We applied this technique to observe the generation of a certain chromophore, thought to be melanin, under the surface of human skin tanned by exposure to long-wavelength UV light. PMID:21644762

Uchiyama, K; Yoshida, K; Wu, X Z; Hobo, T

1998-02-01

157

Inverse Diffusion Theory of Photoacoustics Guillaume Bal  

E-print Network

of Photoacoustics 2 in many practical settings. For references on the practical and theoretical aspects of PAT, weInverse Diffusion Theory of Photoacoustics Guillaume Bal Department of Applied Physics & Applied knowledge of internal data. In the application of photoacoustics, the internal data are the amount

Bal, Guillaume

158

Photoacoustic Thermal Wave Microscopy of Opaque Solids  

Microsoft Academic Search

The photoacoustic effect, the process whereby light energy is converted into acoustic energy was used in the present study to develop photoacoustic thermal wave microscopy instrumentation and methods for performing in -situ photoacoustic response measurements on opaque solids. A conventional Universal Reflectance microscope was modified to allow photoexcitation of the material to be studied with the aid of a focused

Abhijit Biswas

1986-01-01

159

Photoacoustic sensor for medical diagnostics  

NASA Astrophysics Data System (ADS)

The development of new optical sensor technologies has a major impact on the progress of diagnostic methods. Of the permanently increasing number of non-invasive breath tests, the 13C-Urea Breath Test (UBT) for the detection of Helicobacter pylori is the most prominent. However, many recent developments, like the detection of cancer by breath test, go beyond gastroenterological applications. We present a new detection scheme for breath analysis that employs an especially compact and simple set-up. Photoacoustic Spectroscopy (PAS) represents an offset-free technique that allows for short absorption paths and small sample cells. Using a single-frequency diode laser and taking advantage of acoustical resonances of the sample cell, we performed extremely sensitive and selective measurements. The smart data processing method contributes to the extraordinary sensitivity and selectivity as well. Also, the reasonable acquisition cost and low operational cost make this detection scheme attractive for many biomedical applications. The experimental set-up and data processing method, together with exemplary isotope-selective measurements on carbon dioxide, are presented.

Wolff, Marcus; Groninga, Hinrich G.; Harde, Hermann

2004-03-01

160

In-Situ Measurements of Aerosol Optical Properties using New Cavity Ring-Down and Photoacoustics Instruments and Comparison with more Traditional Techniques  

NASA Technical Reports Server (NTRS)

Carbonaceous species (BC and OC) are responsible for most of the absorption associated with aerosol particles. The amount of radiant energy an aerosol absorbs has profound effects on climate and air quality. It is ironic that aerosol absorption coefficient is one of the most difficult aerosol properties to measure. A new cavity ring-down (CRD) instrument, called Cadenza (NASA-ARC), measures the aerosol extinction coefficient for 675 nm and 1550 nm light, and simultaneously measures the scattering coefficient at 675 nm. Absorption coefficient is obtained from the difference of measured extinction and scattering within the instrument. Aerosol absorption coefficient is also measured by a photoacoustic (PA) instrument (DRI) that was operated on an aircraft for the first time during the DOE Aerosol Intensive Operating Period (IOP). This paper will report on measurements made with this new instrument and other in-situ instruments during two field recent field studies. The first field study was an airborne cam;oaign, the DOE Aerosol Intensive Operating Period flown in May, 2003 over northern Oklahoma. One of the main purposes of the IOP was to assess our ability to measure extinction and absorption coefficient in situ. This paper compares measurements of these aerosol optical properties made by the CRD, PA, nephelometer, and Particle Soot Absorption Photometer (PSAP) aboard the CIRPAS Twin-Otter. During the IOP, several significant aerosol layers were sampled aloft. These layers are identified in the remote (AATS-14) as well as in situ measurements. Extinction profiles measured by Cadenza are compared to those derived from the Ames Airborne Tracking Sunphotometer (AATS-14, NASA-ARC). The regional radiative impact of these layers is assessed by using the measured aerosol optical properties in a radiative transfer model. The second study was conducted in the Caldecott Tunnel, a heavily-used tunnel located north of San Francisco, Ca. The aerosol sampled in this study was characterized by fresh automobile and diesel exhaust. Measurements from Cadenza and from an aethalometer are presented. The aethalometer is a filter-based photometer and the infrared channel is calibrated to produce a measure of BC mass loading.

Strawa, A. W.; Arnott, P.; Covert, D.; Elleman, R.; Ferrare, R.; Hallar, A. G.; Jonsson, H.; Kirchstetter, T. W.; Luu, A. P.; Ogren, J.

2004-01-01

161

Photoacoustic lifetime imaging of dissolved oxygen using methylene blue.  

PubMed

Measuring distribution of dissolved oxygen in biological tissue is of prime interest for cancer diagnosis, prognosis, and therapy optimization. Tumor hypoxia indicates poor prognosis and resistance to radiotherapy. Despite its major clinical significance, no current imaging modality provides direct imaging of tissue oxygen. We present preliminary results demonstrating the potential of photoacoustic lifetime imaging (PALI) for noninvasive, 3-D imaging of tissue oxygen. The technique is based on photoacoustic probing of the excited state lifetime of methylene blue (MB) dye. MB is an FDA-approved water soluble dye with a peak absorption at 660 nm. A double pulse laser system (pump probe) is used to excite the dye and probe its transient absorption by detecting photoacoustic emission. The relaxation rate of MB depends linearly on oxygen concentration. Our measurements show high photoacoustic signal contrast at a probe wavelength of 810 nm, where the excited state absorption is more than four times higher than the ground state absorption. Imaging of a simple phantom is demonstrated. We conclude by discussing possible implementations of the technique in clinical settings and combining it with photodynamic therapy (PDT) for real-time therapy monitoring. PMID:20799768

Ashkenazi, Shai

2010-01-01

162

Reverse photoacoustic standoff spectroscopy  

DOEpatents

A system and method are disclosed for generating a reversed photoacoustic spectrum at a greater distance. A source may emit a beam to a target and a detector measures signals generated as a result of the beam being emitted on the target. By emitting a chopped/pulsed light beam to the target, it may be possible to determine the target's optical absorbance by monitoring the intensity of light collected at the detector at different wavelengths. As the wavelength of light is changed, the target may absorb or reject each optical frequency. Rejection may increase the intensity at the sensing element and absorption may decrease the intensity. Accordingly, an identifying spectrum of the target may be made with the intensity variation of the detector as a function of illuminating wavelength.

Van Neste, Charles W. (Kingston, TN); Senesac, Lawrence R. (Knoxville, TN); Thundat, Thomas G. (Knoxville, TN)

2011-04-12

163

Intravascular Photoacoustic Imaging  

PubMed Central

Intravascular photoacoustic (IVPA) imaging is a catheter-based, minimally invasive, imaging modality capable of providing high-resolution optical absorption map of the arterial wall. Integrated with intravascular ultrasound (IVUS) imaging, combined IVPA and IVUS imaging can be used to detect and characterize atherosclerotic plaques building up in the inner lining of an artery. In this paper, we present and discuss various representative applications of combined IVPA/IVUS imaging of atherosclerosis, including assessment of the composition of atherosclerotic plaques, imaging of macrophages within the plaques, and molecular imaging of biomarkers associated with formation and development of plaques. In addition, imaging of coronary artery stents using IVPA and IVUS imaging is demonstrated. Furthermore, the design of an integrated IVUS/IVPA imaging catheter needed for in vivo clinical applications is discussed. PMID:21359138

Wang, Bo; Su, Jimmy L.; Karpiouk, Andrei B.; Sokolov, Konstantin V.; Smalling, Richard W.; Emelianov, Stanislav Y.

2011-01-01

164

Piezoelectric Ultrasonic Micromotors  

E-print Network

This report describes development of micro-fabricated piezoelectric ultrasonic motors and bulk-ceramic piezoelectric ultrasonic motors. Ultrasonic motors offer the advantage of low speed, high torque operation without ...

Flynn, Anita M.

1995-06-01

165

Photoacoustic tomography and sensing in biomedicine  

PubMed Central

Photoacoustics has been broadly studied in biomedicine, for both human and small animal tissues. Photoacoustics uniquely combines the absorption contrast of light or radio frequency waves with ultrasound resolution. Moreover, it is non-ionizing and non-invasive, and is the fastest growing new biomedical method, with clinical applications on the way. This article provides a brief review of recent developments in photoacoustics in biomedicine, from basic principles to applications. The emphasized areas include the new imaging modalities, hybrid detection methods, photoacoustic contrast agents, and the photoacoustic Doppler effect, as well as translational research topics. PMID:19724102

Li, Changhui; Wang, Lihong V.

2010-01-01

166

Piezoelectric drive circuit  

DOEpatents

A piezoelectric motor drive circuit is provided which utilizes the piezoelectric elements as oscillators and a Meacham half-bridge approach to develop feedback from the motor ground circuit to produce a signal to drive amplifiers to power the motor. The circuit automatically compensates for shifts in harmonic frequency of the piezoelectric elements due to pressure and temperature changes.

Treu, Jr., Charles A. (Raymore, MO)

1999-08-31

167

Piezoelectrically Assisted Ultrafiltration  

Microsoft Academic Search

We have demonstrated the feasibility of using piezoelectrically assisted ultrafiltration to reduce membrane fouling and enhance the flux through ultrafiltration membranes. A preliminary economic evaluation, accounting for the power consumption of the piezoelectric driver and the extent of permeate flow rate enhancement, has also shown that piezoelectrically assisted ultrafiltration is cost effective and economically competitive in comparison with traditional separation

N. Ahner; D. Gottschlich; S. Narang; D. Roberts; S. Sharma; S. Ventura

1993-01-01

168

"Mighty Worm" Piezoelectric Actuator  

NASA Technical Reports Server (NTRS)

"Mighty Worm" piezoelectric actuator used as adjustable-length structural member, active vibrator or vibration suppressor, and acts as simple (fixed-length) structural member when inactive. Load force not applied to piezoelectric element in simple-structural-member mode. Piezoelectric element removed from load path when not in use.

Bamford, Robert M.; Wada, Ben K.; Moore, Donald M.

1994-01-01

169

Region-of-interest breast images with the Twente Photoacoustic Mammoscope (PAM)  

NASA Astrophysics Data System (ADS)

The Twente Photoacoustic Mammoscope (PAM) is based on generating laser-induced ultrasound from absorbing structures in the breast. The heart of the instrument is a flat PVDF based detector matrix comprising 590 active elements. The exciting source is an Nd:YAG laser operating at 1064 nm with 5 ns pulses. The instrument is built around a hospital bed. A study protocol was designed to explore the feasibility of using the photoacoustic technique as embodied in PAM to detect cancer in the breasts of patients with suspect/symptomatic breasts. The protocol was approved by a Medical Ethics testing committee and the instrument approved for laser and electrical safety. The protocol was executed at the Medisch Spectrum Twente by using the mammoscope to obtain photoacoustic region-of-interest (ROI) images of the suspect/symptomatic breasts. We report on one case and compare the photoacoustic images obtained with x-ray mammograms and ultrasound images.

Manohar, Srirang; Vaartjes, Sanne E.; van Hespen, Johan G. C.; Klaase, Joost M.; van den Engh, Frank M.; The, Andy K. H.; Steenbergen, Wiendelt; van Leeuwen, Ton G.

2007-02-01

170

Photoacoustic correlation spectroscopy and its application to low-speed flow measurement.  

PubMed

A photoacoustic correlation technique, inspired by its optical counterpart-the fluorescence correlation spectroscopy (FCS)-was tested for the first time, to our knowledge, to demonstrate the feasibility of low-speed flow measurement based on photoacoustic signal detection. A pulsed laser was used to probe the flow of light-absorbing beads. A photoacoustic correlation system of 0.8 s temporal resolution was built and flow speeds ranging from 249 to 14.9 microm/s with corresponding flow times from 4.42 to 74.1 s were measured. The experiment serves as a proof of concept for photoacoustic correlation spectroscopy, which may have many potential applications similar to the FCS. PMID:20410966

Chen, Sung-Liang; Ling, Tao; Huang, Sheng-Wen; Won Baac, Hyoung; Guo, L Jay

2010-04-15

171

Photoacoustic guided ultrasound wavefront shaping for targeted acousto-optic imaging.  

PubMed

To overcome speed of sound aberrations that negatively impact the acoustic focus in acousto-optic imaging, received photoacoustic signals are used to guide the formation of ultrasound wavefronts to compensate for acoustic inhomogeneities. Photoacoustic point sources composed of gold and superparamagnetic iron oxide nanoparticles are used to generate acoustic waves that acoustically probe the medium as they propagate to the detector. By utilizing cross-correlation techniques with the received photoacoustic signal, transmitted ultrasound wavefronts compensate for the aberration, allowing for optimized and configurable ultrasound transmission to targeted locations. It is demonstrated that utilizing a portable commercially available ultrasound system using customized software, photoacoustic guided ultrasound wavefront shaping for targeted acousto-optic imaging is robust in the presence of large, highly attenuating acoustic aberration. PMID:24514632

Staley, Jacob; Hondebrink, Erwin; Peterson, Wilma; Steenbergen, Wiendelt

2013-12-16

172

Contrast Agents for Photoacoustic and Thermoacoustic Imaging: A Review  

PubMed Central

Photoacoustic imaging (PAI) and thermoacoustic imaging (TAI) are two emerging biomedical imaging techniques that both utilize ultrasonic signals as an information carrier. Unique advantages of PAI and TAI are their abilities to provide high resolution functional information such as hemoglobin and blood oxygenation and tissue dielectric properties relevant to physiology and pathology. These two methods, however, may have a limited detection depth and lack of endogenous contrast. An exogenous contrast agent is often needed to effectively resolve these problems. Such agents are able to greatly enhance the imaging contrast and potentially break through the imaging depth limit. Furthermore, a receptor-targeted contrast agent could trace the molecular and cellular biological processes in tissues. Thus, photoacoustic and thermoacoustic molecular imaging can be outstanding tools for early diagnosis, precise lesion localization, and molecular typing of various diseases. The agents also could be used for therapy in conjugation with drugs or in photothermal therapy, where it functions as an enhancer for the integration of diagnosis and therapy. In this article, we present a detailed review about various exogenous contrast agents for photoacoustic and thermoacoustic molecular imaging. In addition, challenges and future directions of photoacoustic and thermoacoustic molecular imaging in the field of translational medicine are also discussed. PMID:25530615

Wu, Dan; Huang, Lin; Jiang, Max S.; Jiang, Huabei

2014-01-01

173

Photoacoustic imaging and temperature measurement for photothermal cancer therapy  

PubMed Central

Photothermal therapy is a noninvasive, targeted, laser-based technique for cancer treatment. During photothermal therapy, light energy is converted to heat by tumor-specific photoabsorbers. The corresponding temperature rise causes localized cancer destruction. For effective treatment, however, the presence of photoabsorbers in the tumor must be ascertained before therapy and thermal imaging must be performed during therapy. This study investigates the feasibility of guiding photothermal therapy by using photoacoustic imaging to detect photoabsorbers and to monitor temperature elevation. Photothermal therapy is carried out by utilizing a continuous wave laser and metal nanocomposites broadly absorbing in the near-infrared optical range. A linear array-based ultrasound imaging system is interfaced with a nanosecond pulsed laser to image tissue-mimicking phantoms and ex-vivo animal tissue before and during photothermal therapy. Before commencing therapy, photoacoustic imaging identifies the presence and spatial location of nanoparticles. Thermal maps are computed by monitoring temperature-induced changes in the photoacoustic signal during the therapeutic procedure and are compared with temperature estimates obtained from ultrasound imaging. The results of our study suggest that photoacoustic imaging, augmented by ultrasound imaging, is a viable candidate to guide photoabsorber-enhanced photothermal therapy. PMID:18601569

Shah, Jignesh; Park, Suhyun; Aglyamov, Salavat; Larson, Timothy; Ma, Li; Sokolov, Konstantin; Johnston, Keith; Milner, Thomas; Emelianov, Stanislav Y.

2009-01-01

174

Improved Open Photoacoustic Helmholtz Cell  

NASA Astrophysics Data System (ADS)

This paper presents the design of an open photoacoustic Helmholtz cell in which high acoustic volumes with quarter-wave ducts act as high-impedance separators between the main Helmholtz cell structure and the exterior. As a result, penetration of the external acoustic noise into the cell was substantially reduced in comparison to earlier open Helmholtz cell designs. Although the presented cell is not windowless, the photoacoustic background signal resulting from the absorption of the light by the windows is significantly lower in comparison to standard Helmholtz cells. Such an effect was obtained by locating the windows not at the relatively small sample cavity, but at the acoustic buffers, for which the volumes are two orders of magnitude higher. The proposed cell is dedicated for gas or liquid measurements, and its design allows for constant flow of the fluid. Hence, it can be used in continuous, real-time photoacoustic measurements.

Starecki, Tomasz; Geras, Antonina

2014-11-01

175

Application of time-resolved glucose concentration photoacoustic signals based on an improved wavelet denoising  

NASA Astrophysics Data System (ADS)

Real-time monitoring of blood glucose concentration (BGC) is a great important procedure in controlling diabetes mellitus and preventing the complication for diabetic patients. Noninvasive measurement of BGC has already become a research hotspot because it can overcome the physical and psychological harm. Photoacoustic spectroscopy is a well-established, hybrid and alternative technique used to determine the BGC. According to the theory of photoacoustic technique, the blood is irradiated by plused laser with nano-second repeation time and micro-joule power, the photoacoustic singals contained the information of BGC are generated due to the thermal-elastic mechanism, then the BGC level can be interpreted from photoacoustic signal via the data analysis. But in practice, the time-resolved photoacoustic signals of BGC are polluted by the varities of noises, e.g., the interference of background sounds and multi-component of blood. The quality of photoacoustic signal of BGC directly impacts the precision of BGC measurement. So, an improved wavelet denoising method was proposed to eliminate the noises contained in BGC photoacoustic signals. To overcome the shortcoming of traditional wavelet threshold denoising, an improved dual-threshold wavelet function was proposed in this paper. Simulation experimental results illustrated that the denoising result of this improved wavelet method was better than that of traditional soft and hard threshold function. To varify the feasibility of this improved function, the actual photoacoustic BGC signals were test, the test reslut demonstrated that the signal-to-noises ratio(SNR) of the improved function increases about 40-80%, and its root-mean-square error (RMSE) decreases about 38.7-52.8%.

Ren, Zhong; Liu, Guodong; Huang, Zhen

2014-10-01

176

Single-cell photoacoustic thermometry  

PubMed Central

Abstract. A novel photoacoustic thermometric method is presented for simultaneously imaging cells and sensing their temperature. With three-seconds-per-frame imaging speed, a temperature resolution of 0.2°C was achieved in a photo-thermal cell heating experiment. Compared to other approaches, the photoacoustic thermometric method has the advantage of not requiring custom-developed temperature-sensitive biosensors. This feature should facilitate the conversion of single-cell thermometry into a routine lab tool and make it accessible to a much broader biological research community. PMID:23377004

Gao, Liang; Wang, Lidai; Li, Chiye; Liu, Yan; Ke, Haixin; Zhang, Chi; Wang, Lihong V.

2013-01-01

177

A transparent broadband ultrasonic detector based on an optical micro-ring resonator for photoacoustic microscopy  

PubMed Central

Photoacoustic microscopy (PAM) does not rely on contrast agent to image the optical absorption contrast in biological tissue. It is uniquely suited for measuring several tissue physiological parameters, such as hemoglobin oxygen saturation, that would otherwise remain challenging. Researchers are designing new clinical diagnostic tools and multimodal microscopic systems around PAM to fully unleash its potential. However, the sizeable and opaque piezoelectric ultrasonic detectors commonly used in PAM impose a serious constraint. Our solution is a coverslip-style optically transparent ultrasound detector based on a polymeric optical micro-ring resonator (MRR) with a total thickness of 250??m. It enables highly-sensitive ultrasound detection over a wide receiving angle with a bandwidth of 140?MHz, which corresponds to a photoacoustic saturation limit of 287?cm?1, at an estimated noise-equivalent pressure (NEP) of 6.8?Pa. We also established a theoretical framework for designing and optimizing the MRR for PAM. PMID:24675547

Li, Hao; Dong, Biqin; Zhang, Zhen; Zhang, Hao F.; Sun, Cheng

2014-01-01

178

A transparent broadband ultrasonic detector based on an optical micro-ring resonator for photoacoustic microscopy.  

PubMed

Photoacoustic microscopy (PAM) does not rely on contrast agent to image the optical absorption contrast in biological tissue. It is uniquely suited for measuring several tissue physiological parameters, such as hemoglobin oxygen saturation, that would otherwise remain challenging. Researchers are designing new clinical diagnostic tools and multimodal microscopic systems around PAM to fully unleash its potential. However, the sizeable and opaque piezoelectric ultrasonic detectors commonly used in PAM impose a serious constraint. Our solution is a coverslip-style optically transparent ultrasound detector based on a polymeric optical micro-ring resonator (MRR) with a total thickness of 250??m. It enables highly-sensitive ultrasound detection over a wide receiving angle with a bandwidth of 140?MHz, which corresponds to a photoacoustic saturation limit of 287?cm(-1), at an estimated noise-equivalent pressure (NEP) of 6.8?Pa. We also established a theoretical framework for designing and optimizing the MRR for PAM. PMID:24675547

Li, Hao; Dong, Biqin; Zhang, Zhen; Zhang, Hao F; Sun, Cheng

2014-01-01

179

A self diagnostic system for piezoelectric sensors  

NASA Technical Reports Server (NTRS)

A technique for determining the mounting conditions of a piezoelectric accelerometer is presented. This technique electrically stimulates the piezoelectric element in the 'diagnostic' frequency band measuring the electrical frequency response characteristics across a capacitive load impedance. The diagnostic frequency band is tipically much higher than the operating bandwidth of the accelerometer. The resonant frequencies of the accelerometer are included in the diagnostic band. By monitoring the shift in these resonant frequencies, via electrical stimulation techniques, certain diagnostic conditions including mounting conditions can be determined. Experimental data from a compression mode accelerometer is used to demonstrate this technique.

Atherton, William J.; Flanagan, Patrick M.

1989-01-01

180

Theory of photoacoustic signal generation for optimized photoacoustic cells  

Microsoft Academic Search

Recent advances in the theory of the photoacoustic effect are applied to the problem of cell optimization. Three-dimensional heat flow, including conduction to the cell window and walls, is considered. A relatively simple theoretical expression for the signal is obtained, provided certain experimental conditions are satisfied.

F. Alan McDonald

1981-01-01

181

[Theoretical study on radial resonance coupling of cylindrical photoacoustic cells].  

PubMed

Photoacoustic detection of trace concentrations of gases is one of the most sensitive techniques of infrared absorption spectroscopy. High-sensitivity photoacoustic detectors apply an acoustic resonator for the amplification of the weak photoacoustic signal. If the modulation frequency coincides with one of the resonance frequencies of the chamber, a standing acoustic wave is excited and the system works as an acoustic amplifier. The amplification of the resonator relies on the acting mode, quality factor, nature of microphone, and the coupling between electromagnetic radiation and the stand wave resonance mode. With different incidence orientation of the modulated IR laser relative to acoustic chamber, the sound pressure magnitude of resonance mode varies. The influence of different laser incidence orientation on the coupling coefficients of radial resonance mode of cylindrical photoacoustic cells was investigated by both theoretical deduction and numerical computation method. It is concluded that the coupling coefficients have two zeros and two maximums when the laser incidence angle varies from 0 to pi/2. When the incidence angle is 0 or tan(-1) (0.859 2 X 2R/L), the coupling coefficients are zeros and the radial resonance is invalid. When the incidence angle is tan(-1) (0.556 8 X 2R/L) or tan(-1) (2R/L), the coupling coefficients are the maximums and the radial resonance is the strongest. Here R is the radius and L the length of the cell. The results therein before give some theoretical guidelines for photoacoustic cell designing, optimizing, installing and adjusting, and for improvement of detection sensitivity in trace gas detectors through maximal excitement of radial modes in cylindrical acoustic cells. PMID:20545122

Yuan, Chang-Ying; Liu, Xian-Yong; Meng, Gui; Zhao, Liang

2010-04-01

182

Patterned thin metal film for the lateral resolution measurement of photoacoustic tomography  

PubMed Central

Background Image quality assessment method of photoacoustic tomography has not been completely standardized yet. Due to the combined nature of photonic signal generation and ultrasonic signal transmission in biological tissue, neither optical nor ultrasonic traditional methods can be used without modification. An optical resolution measurement technique was investigated for its feasibility for resolution measurement of photoacoustic tomography. Methods A patterned thin metal film deposited on silica glass provides high contrast in optical imaging due to high reflectivity from the metal film and high transmission from the glass. It provides high contrast when it is used for photoacoustic tomography because thin metal film can absorb pulsed laser energy. An US Air Force 1951 resolution target was used to generate patterned photoacoustic signal to measure the lateral resolution. Transducer with 2.25?MHz bandwidth and a sample submerged in water and gelatinous block were tested for lateral resolution measurement. Results Photoacoustic signal generated from a thin metal film deposited on a glass can propagate along the surface or through the surrounding medium. First, a series of experiments with tilted sample confirmed that the measured photoacoustic signal is what is propagating through the medium. Lateral resolution of the photoacoustic tomography system was successfully measured for water and gelatinous block as media: 0.33?mm and 0.35?mm in water and gelatinous material, respectively, when 2.25?MHz transducer was used. Chicken embryo was tested for biomedical applications. Conclusions A patterned thin metal film sample was tested for its feasibility of measuring lateral resolution of a photoacoustic tomography system. Lateral resolutions in water and gelatinous material were successfully measured using the proposed method. Measured resolutions agreed well with theoretical values. PMID:22794510

2012-01-01

183

Harvesting Raindrop Energy with Piezoelectrics: a Review  

NASA Astrophysics Data System (ADS)

Harvesting vibration energy from piezoelectric material impacted by raindrops has proved to be a promising approach for future applications. A piezoelectric harvester has interesting advantages such as simple structure, easy fabrication, reduced number of components, and direct conversion of vibrations to electrical charge. Extensive research has been carried out and is still underway to explore this technique for practical applications. This review provides a comprehensive picture of global research and development of raindrop energy harvesting using piezoelectric material to enable researchers to determine the direction of further investigation. The work published so far in this area is reviewed and summarized with relevant suggestions for future work. In addition, a brief experiment was carried out to investigate the suitable piezoelectric structure for raindrop energy harvesting. Results showed that the bridge structure generated a higher voltage compared with the cantilever structure.

Wong, Chin-Hong; Dahari, Zuraini; Abd Manaf, Asrulnizam; Miskam, Muhammad Azman

2015-01-01

184

S-sequence patterned illumination iterative photoacoustic tomography.  

PubMed

Quantitatively reconstructing optical absorption using photoacoustic imaging is nontrivial. Theoretical hurdles, such as nonuniqueness and numerical instability, can be mitigated by using multiple illuminations. However, even with multiple illuminations, using ANSI-safety-limited fluence for practical imaging may result in poor performance owing to limited signal-to-noise ratio (SNR). We demonstrate the use of S-sequence coded patterned illumination to boost SNR while preserving the enhanced stability of multiple-illumination iterative techniques. PMID:25202899

Harrison, Tyler; Shao, Peng; Zemp, Roger J

2014-09-01

185

Developing a self-diagnostic system for piezoelectric sensors  

NASA Technical Reports Server (NTRS)

Measurement techniques for developing a self-diagnostic system for piezoelectric sensors are presented. The self-diagnostic system uses two types of measurement techniques based on passive and active evaluation of the piezoelectric element. Both hard and soft failures can be detected by this system. Hard failures such as loss of sensor signal and change in sensor output resistance are determined by monitoring the sensor's output resistance, voltage or current. These are passive measurements of the sensor's output condition. Soft failures include changes in sensor calibration and mounting conditions. Soft failures are detected by measuring structural/electrical impedance of the piezoelectric sensor. Active measurement techniques are used to calculate changes in piezoelectric element properties related to soft failures. This paper describes the general operating principles of a self-diagnostic system and discusses the design of an active/passive measurement technique required for this system to function. Experimental results using two types of piezoelectric accelerometers are presented.

Flanagan, Patrick M.; Atherton, William J.

1990-01-01

186

Noninvasive monitoring of traumatic brain injury and post-traumatic rehabilitation with laser-induced photoacoustic imaging  

NASA Astrophysics Data System (ADS)

A photoacoustic imaging system was used for noninvasive monitoring of traumatic mouse brain in vivo with high-quality reconstructed images. Traumatic lesions accompanying with hemorrhage in the mouse cortical surface were accurately mapped, and foreign bodies of two small copper wires inserted in the mouse brain were also detected. Furthermore, the time course of morphological changes of cerebral blood during rehabilitation process of a mouse brain with traumatic brain injury was obtained using a series of photoacoustic images. Experimental results demonstrate that photoacoustic technique holds the potential for clinical applications in brain trauma and cerebrovascular disease detection.

Yang, Sihua; Xing, Da; Lao, Yeqi; Yang, Diwu; Zeng, Lvming; Xiang, Liangzhong; Chen, Wei R.

2007-06-01

187

Measurements of thermal effusivity of liquids using a conventional photoacoustic cell  

NASA Astrophysics Data System (ADS)

In this article, we present a new photoacoustic technique, based on the conventional photoacoustic configuration, to characterize the thermal effusivity of liquid samples. This new technique is applicable for all kind of liquid samples, including the nontransparent ones. In order to show the usefulness of this new technique, we measured the thermal effusivity of a variety of liquid samples including: distilled water, ethanol, methanol, chloroform, glycerol, and car oil. The comparison with literature values shows a remarkable agreement. Also, we show measurements of the thermal effusivity of acetone in distilled water mixtures, showing the graphical dependence of this thermal property with the concentration of one of the components.

Balderas-López, J. A.; Gutiérrez-Juárez, G.; Jaime-Fonseca, M. R.; Sánchez-Sinencio, Feliciano

1999-04-01

188

A piezoelectric transformer  

NASA Technical Reports Server (NTRS)

This work describes a modeling and design method whereby a piezoelectric system is formulated by two sets of second-order equations, one for the mechanical system, and the other for the electrical system, coupled through the piezoelectric effect. The solution to this electromechanical coupled system gives a physical interpretation of the piezoelectric effect as a piezoelectric transformer that is a part of the piezoelectric system, which transfers the applied mechanical force into a force-controlled current source, and short circuit mechanical compliance into capacitance. It also transfers the voltage source into a voltage-controlled relative velocity input, and free motional capacitance into mechanical compliance. The formulation and interpretation simplify the modeling of smart structures and lead to physical insight that aids the designer. Due to its physical realization, the smart structural system can be unconditional stable and effectively control responses. This new concept has been demonstrated in three numerical examples for a simple piezoelectric system.

Won, C. C.

1993-01-01

189

Photoacoustic signal amplification through plasmonic nanoparticle aggregation  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging, using targeted plasmonic metallic nanoparticles, is a promising noninvasive molecular imaging method. Analysis of the photoacoustic signal generated by plasmonic metallic nanoparticles is complex because of the dependence upon physical properties of both the nanoparticle and the surrounding environment. We studied the effect of the aggregation of gold nanoparticles on the photoacoustic signal amplitude. We found that the photoacoustic signal from aggregated silica-coated gold nanoparticles is greatly enhanced in comparison to disperse silica-coated gold nanoparticles. Because cellular uptake and endocytosis of nanoparticles results in their aggregation, these results have important implications for the application of plasmonic metallic nanoparticles towards quantitative molecular imaging.

Bayer, Carolyn L.; Nam, Seung Yun; Chen, Yun-Sheng; Emelianov, Stanislav Y.

2013-01-01

190

Photoacoustic signal amplification through plasmonic nanoparticle aggregation  

PubMed Central

Abstract. Photoacoustic imaging, using targeted plasmonic metallic nanoparticles, is a promising noninvasive molecular imaging method. Analysis of the photoacoustic signal generated by plasmonic metallic nanoparticles is complex because of the dependence upon physical properties of both the nanoparticle and the surrounding environment. We studied the effect of the aggregation of gold nanoparticles on the photoacoustic signal amplitude. We found that the photoacoustic signal from aggregated silica-coated gold nanoparticles is greatly enhanced in comparison to disperse silica-coated gold nanoparticles. Because cellular uptake and endocytosis of nanoparticles results in their aggregation, these results have important implications for the application of plasmonic metallic nanoparticles towards quantitative molecular imaging. PMID:23288414

Bayer, Carolyn L.; Nam, Seung Yun; Chen, Yun-Sheng; Emelianov, Stanislav Y.

2013-01-01

191

Electrospinning of continuous piezoelectric yarns for composite application  

NASA Astrophysics Data System (ADS)

The focus of this research is to electrospin continuous yarns of piezoelectric nanofibers. Incorporating piezoelectric polymer fibers in traditional composites can add sensing and actuation capabilities, which creates a wide array of potential applications. To process nanofibers with piezoelectric properties, we are pursuing the electrospinning of poly (vinylidene fluoride) (PVDF) in DMAc. A method of electrospinning on water is used to form the continuous fibers, which are then tested using DSC, XRD, and microscopy. Through this technique, we see evidence that the non-polar ?-phase of PVDF is converted to the polar ?-phase, which is responsible for its piezoelectric behavior.

Lagoudas, Natasha C.; Ounaies, Zoubeida

2008-03-01

192

Usefulness of the photoacoustic measurement method for monitoring the regenerative process of full-thickness defects in articular cartilage using tissue-engineering technology  

NASA Astrophysics Data System (ADS)

We demonstrated the capability of photoacoustic measurement for viscoelastic characterization. Since tissue viscoelasticity affects the propagation and attenuation of photoacoustic waves generated in the tissue, the relaxation times of the photoacoustic waves give the viscosity-elasticity ratio of the tissue. The relaxation times of photoacoustic waves of articular cartilage tissues engineered under various culture conditions were closely correlated with intrinsic viscosity-elasticity ratios measured by using a conventional viscoelastic analyzer (R > 0.98). In order to apply the photoacoustic measurement method to evaluation of the regeneration of articular cartilage as a method to validate the surgery, the method should enable not only evaluation of engineered tissue during cultivation in vitro but also evaluation after transplantation of engineered tissue in vivo. The aim of this study was to verify the usefulness of the photoacoustic method for repeated measurement of viscoelastic properties in order to evaluate the process of regeneration of a full-thickness defect in rabbit articular cartilage using allografted tissue-engineered cartilage. Photoacoustic waves were induced by 266- and 355-nm, 5-7 ns, light pulses delivered through an optical silica fiber from an Q-switched Nd:YAG laser and were detected by a piezoelectric transducer, which we had designed. About a 40% difference between the viscosity-elasticity ratio of allografted cartilage that of tissue surrounding the defect was shown just after surgery. The difference was significantly reduced at 4 and 12 postoperative weeks. Therefore, since the photoacoustic measurement method enables assessment of the progress of restoration of the viscoelasticity of articular cartilage, its main function, this method would be useful as an evaluation method in regenerative medicine.

Ishihara, Miya; Sato, Masato; Sato, Shunichi; Kikuchi, Toshiyuki; Mitani, Genya; Kaneshiro, Nagatoshi; Ishihara, Masayuki; Mochida, Joji; Kikuchi, Makoto

2005-04-01

193

Photoacoustic Evaluation of the Mechanical Properties of Aluminum / Silicon Nitride Double-Layer Thin Films  

NASA Astrophysics Data System (ADS)

In this paper, we compare two photoacoustic techniques to characterize the mechanical parameters of edge-supported aluminum and silicon nitride double-layer thin films. In a first set of experiments, a femtosecond transient pump-probe technique is used to investigate the Young's moduli of the aluminum and silicon nitride layers by launching ultra-high frequency bulk acoustic waves in the films. In a second set of experiments, dispersion curves of the A0 mode of the Lamb waves that propagate along the unsupported films are measured using a broadband photoacoustic guided-wave method. The residual stresses and flexural rigidities for the same set of double-layer membranes are determined from these dispersion curves. Comparisons of the results obtained by the two photoacoustic techniques are made.

Zhang, Feifei; Krishnaswamy, Sridhar; Lilley, Carmen M.

2006-03-01

194

Intracavity quartz-enhanced photoacoustic sensor  

SciTech Connect

We report on a spectroscopic technique named intracavity quartz-enhanced photoacoustic spectroscopy (I-QEPAS) employed for sensitive trace-gas detection in the mid-infrared spectral region. It is based on a combination of QEPAS with a buildup optical cavity. The sensor includes a distributed feedback quantum cascade laser emitting at 4.33??m. We achieved a laser optical power buildup factor of ?500, which corresponds to an intracavity laser power of ?0.75?W. CO{sub 2} has been selected as the target molecule for the I-QEPAS demonstration. We achieved a detection sensitivity of 300 parts per trillion for 4?s integration time, corresponding to a noise equivalent absorption coefficient of 1.4?×?10{sup ?8}?cm{sup ?1} and a normalized noise-equivalent absorption of 3.2?×?10{sup ?10} W cm{sup ?1}?Hz{sup ?1/2}.

Borri, S., E-mail: simone.borri@ino.it; Galli, I.; Mazzotti, D.; Giusfredi, G.; De Natale, P. [CNR-INO UOS Sesto Fiorentino and LENS, via Carrara 1, 50019 Sesto Fiorentino FI (Italy); Patimisco, P.; Scamarcio, G.; Spagnolo, V. [CNR-IFN UOS Bari and Dipartimento Interateneo di Fisica, Università degli Studi di Bari e Politecnico di Bari, via Amendola 173, 70126 Bari BA (Italy); Akikusa, N. [Development Bureau Laser Device R and D Group, Hamamatsu Photonics KK, Shizuoka 434-8601 (Japan); Yamanishi, M. [Central Research Laboratories, Hamamatsu Photonics KK, Shizuoka 434-8601 (Japan)

2014-03-03

195

Improved Current and Charge Amplifiers for Driving Piezoelectric Loads, and Issues in Signal  

E-print Network

Improved Current and Charge Amplifiers for Driving Piezoelectric Loads, and Issues in Signal of hysteresis (Jaffe et al., 1971; Adriaens, 2000). When used in an actuating role, piezoelectric transducers of the sentiment towards this technique: ``While hysteresis in a piezoelectric actuator is reduced if the charge

Fleming, Andrew J.

196

Parametric dependencies for photoacoustic leak localization  

NASA Astrophysics Data System (ADS)

Unintended gas or liquid leaks from manufactured components or manufacturing systems may be detrimental to consumers, manufacturers, and the environment. Thus, leak testing is important for quality, safety, and environmental reasons. This paper describes parametric dependencies for photoacoustic leak localization. The technique is based on the interaction of 10.6-micrometer radiation from a carbon dioxide (CO2) laser and a photoactive tracer gas, sulfur hexafluoride (SF6). For the current investigations, acoustic signals are generated by scanning a laser beam at high speed through gas plumes formed above calibrated leaks. These signals are remotely measured with a four-microphone linear array and analyzed using Bartlett and minimum-variance-distortionless (MVD) matched-field processing (MFP) techniques to determine leak location. This paper extends prior work in photoacoustic leak testing through (i) use of more signal frequencies; (ii) parametric study of four different laser scan rates; and (iii) examination of mismatch between the actual acoustic environment and the propagation model used in the MFP; and (iv) presentation of leak localization results on a curved surface. For a 12-watt CO2 laser exciting the small SF6 gas plume produced by a one-cm3-per-day leak with microphones placed 0.41 m from the leak location, root-mean-square localization uncertainties as small as plus-or-minus0.5 mm on a line scan of 0.46 m can be achieved when the largest possible number of signal frequencies fall in a measurement bandwidth of approximately 70 kHz. copyright 2002 Acoustical Society of America.

Yonak, Serdar H.; Dowling, David R.

2002-07-01

197

Parametric dependencies for photoacoustic leak localization.  

PubMed

Unintended gas or liquid leaks from manufactured components or manufacturing systems may be detrimental to consumers, manufacturers, and the environment. Thus, leak testing is important for quality, safety, and environmental reasons. This paper describes parametric dependencies for photoacoustic leak localization. The technique is based on the interaction of 10.6-micrometer radiation from a carbon dioxide (CO2) laser and a photoactive tracer gas, sulfur hexafluoride (SF6). For the current investigations, acoustic signals are generated by scanning a laser beam at high speed through gas plumes formed above calibrated leaks. These signals are remotely measured with a four-microphone linear array and analyzed using Bartlett and minimum-variance-distortionless (MVD) matched-field processing (MFP) techniques to determine leak location. This paper extends prior work in photoacoustic leak testing through (i) use of more signal frequencies; (ii) parametric study of four different laser scan rates; and (iii) examination of mismatch between the actual acoustic environment and the propagation model used in the MFP; and (iv) presentation of leak localization results on a curved surface. For a 12-watt CO2 laser exciting the small SF6 gas plume produced by a one-cm3-per-day leak with microphones placed 0.41 m from the leak location, root-mean-square localization uncertainties as small as +/-0.5 mm on a line scan of 0.46 m can be achieved when the largest possible number of signal frequencies fall in a measurement bandwidth of approximately 70 kHz. PMID:12141339

Yönak, Serdar H; Dowling, David R

2002-07-01

198

High strain behavior of composite thin film piezoelectric membranes  

Microsoft Academic Search

The behavior of thin-film piezoelectric membranes at high deflections and strains for use as generators is examined. Experiments are conducted with a bulge tester to obtain pressure–deflection relationships, residual stresses, and electrical output characteristics of the piezoelectric membranes. A model is developed using an energy minimization technique. The experimental results are compared to the modeled results. Experimental results have shown

I. Demir; A. L. Olson; J. L. Skinner; C. D. Richards; R. F. Richards; D. F. Bahr

2004-01-01

199

Photoacoustic elastic bending method in microelectronics invited paper  

Microsoft Academic Search

The basic concept, development and application of the photoacoustic elastic bending method are given. The photoacoustic effect as a function of modulation frequency including the elastic bending contribution to the photoacoustic signal is investigated. The theoretical model for a typical detection configuration was given and the relations for elastic bending and photoacoustic signal were derived by the dynamic theory of

D. M. Todorovic

2006-01-01

200

Amplitude-masked photoacoustic wavefront shaping and application in flowmetry  

PubMed Central

Optical-resolution photoacoustic flowmetry allows non-invasive single-cell flow measurements. However, its operational depth is limited by optical diffusion, which prevents focusing beyond shallow depths in scattering media, as well as reducing the measurement signal-to-noise ratio (SNR). To overcome this limitation, we used binary-amplitude wavefront shaping to enhance light focusing in the presence of scattering. Here, the transmission modes that contributed constructively to the intensity at the optical focus were identified and selectively illuminated, resulting in a 14-fold intensity increase and a corresponding increase in SNR. This technique can potentially extend the operational depth of optical-resolution photoacoustic flowmetry beyond 1 mm in tissue. PMID:25360912

Tay, Jian Wei; Liang, Jinyang; Wang, Lihong V.

2014-01-01

201

Photoacoustic evaluation of the penetration of piroxicam gel applied with phonophoresis into human skin  

Microsoft Academic Search

The photoacoustic (PA) technique has been increasingly employed in biomedical studies, allowing in vivo skin measurements not easily performed with other techniques. It is possible to use PA measurements to evaluate transdermal delivery of products topically applied through manual massage or phonophoresis, that is the utilization of ultrasound waves to enhance drug absorption. The aim of this study was to

F. L. F. D. Silveira; P. R. Barja; D. Acosta-Avalos

2010-01-01

202

Piezoelectric dispenser based on a piezoelectric-metal-cavity actuator  

Microsoft Academic Search

A piezoelectric dispenser has been fabricated based on the idea of a piezoelectric-metal-cavity (PMC) actuator. The PMC actuator consists of a metal ring sandwiched between two identical piezoelectric unimorphs. The radial contraction of the piezoelectric ceramic is converted into a flextensional motion of the unimorph, causing a large flexural displacement in the center part of the actuator. With the PMC

K. H. Lam; C. L. Sun; K. W. Kwok; H. L. W. Chan

2009-01-01

203

Pattern Recognition in Photoacoustic Dataset  

NASA Astrophysics Data System (ADS)

In photoacoustic imaging, optical absorption properties of matter are imaged by detecting the ultrasound that is produced when the material is illuminated by a laser. For medical imaging, photoacoustics is a useful tool since matter in the human body has different optical absorption properties. In this study, pattern recognition systems are used to study a set of medical images for tumor identification and extraction—to detect the specific area in which the tumor is present. The objective is to incorporate this information into real-time image acquisition systems to improve medical diagnosis. Preliminary results obtained by studying the image dataset demonstrated the interchangeability of the proposed system. A system of automatic classification was constructed, using a set of images with and without cancerous tumors to evaluate the proposed method. The training set used was manually labeled, and the test set was never seen by the training set. The results helped us determine the feasibility of the proposed system.

Guzmán-Cabrera, R.; Guzmán-Sepúlveda, J. R.; Torres-Cisneros, M.; May-Arrioja, D. A.; Ruiz-Pinales, J.; Ibarra-Manzano, O. G.; Aviña-Cervantes, G.

2013-09-01

204

Depth and resolution characterization of two-photon photoacoustic spectroscopy for noninvasive subsurface chemical diagnostics  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy is a powerful optical biopsy technique that enables rapid tumor diagnosis in situ. It has also been reported that photoacoustic spectroscopy can be used to diagnose pre-malignant tissue based on the chemical differences between healthy and pre-malignant tissues. Since the acoustic signals obtained from tissues in these analyses suffer from minimum damping, photoacoustic spectroscopy can be highly sensitive. This paper focuses on the characterization of a novel multiphoton excited photoacoustic methodology for margining of malignant and pre-malignant tissues. The two-photon excitation process in tissues using nanosecond laser pulses produces ultrasonic signals that transmit through tissue with minimal attenuation. Additionally, the two-photon excitation process is highly localized since only ballistic photons contribute to the excitation process; thereby eliminating potential absorption events in tissue not of interest (i.e., along the beam path) and increasing the spatial resolution of the diagnostic technique to that achievable via optics. This work characterizes the two-photon excitation process for photoacoustic signal measurements on a model dye. Using gelatin phantoms to mimic real tissues, tissue penetration studies were performed, revealing chemical species as deep as 1.3 cm in the tissue can easily be detected using this methodology. Furthermore, the resolution of this multiphoton excitation process was determined to be as great as 50 ?m (near cellular level resolution).

Dahal, Sudhir; Kiser, John B.; Cullum, Brian M.

2011-05-01

205

Development and Application of Stable Phantoms for the Evaluation of Photoacoustic Imaging Instruments  

PubMed Central

Photoacoustic imaging combines the high contrast of optical imaging with the spatial resolution and penetration depth of ultrasound. This technique holds tremendous potential for imaging in small animals and importantly, is clinically translatable. At present, there is no accepted standard physical phantom that can be used to provide routine quality control and performance evaluation of photoacoustic imaging instruments. With the growing popularity of the technique and the advent of several commercial small animal imaging systems, it is important to develop a strategy for assessment of such instruments. Here, we developed a protocol for fabrication of physical phantoms for photoacoustic imaging from polyvinyl chloride plastisol (PVCP). Using this material, we designed and constructed a range of phantoms by tuning the optical properties of the background matrix and embedding spherical absorbing targets of the same material at different depths. We created specific designs to enable: routine quality control; the testing of robustness of photoacoustic signals as a function of background; and the evaluation of the maximum imaging depth available. Furthermore, we demonstrated that we could, for the first time, evaluate two small animal photoacoustic imaging systems with distinctly different light delivery, ultrasound imaging geometries and center frequencies, using stable physical phantoms and directly compare the results from both systems. PMID:24086557

Bohndiek, Sarah E.; Bodapati, Sandhya; Van De Sompel, Dominique; Kothapalli, Sri-Rajasekhar; Gambhir, Sanjiv S.

2013-01-01

206

Synchrotron infrared photoacoustic spectroscopy Kirk H. Michaeliana)  

E-print Network

of SR in the mid-infrared. Other beamlines are optimized for far-infrared spectroscopy, in recognition- and far-infrared photoacoustic PA spectroscopy, where the IR beam is usually slightly focused to about 5Synchrotron infrared photoacoustic spectroscopy Kirk H. Michaeliana) Natural Resources Canada

Homes, Christopher C.

207

Ultrasensitive CO2 laser photoacoustic system  

Microsoft Academic Search

The present paper describes an extremely sensitive apparatus based upon laser photoacoustic spectroscopy (LPAS) methods which can be used for the detection and measurement of trace gases at very low concentrations (parts per trillion by volume - pptV). Two experimental set-ups were designed and characterized with the photoacoustic (PA) cell in an external configuration: the first one with a low

D. C. Dumitras; S. Banita; A. M. Bratu; R. Cernat; D. C. A. Dutu; C. Matei; M. Patachia; M. Petrus; C. Popa

2010-01-01

208

Mathematics of thermoacoustic and photoacoustic tomography  

E-print Network

with good contrast (like optical or electrical impedance tomography) suffer from low resolution, while someMathematics of thermoacoustic and photoacoustic tomography Peter Kuchment and Leonid Kunyansky in the Thermoacoustic and Photoacoustic To- mography. 1 Introduction Medical tomography has had a huge impact on medical

209

Quantitative photoacoustic imaging in radiative transport regime  

E-print Network

Quantitative photoacoustic imaging in radiative transport regime Alexander V. Mamonov Kui Ren July 6, 2012 Abstract The objective of quantitative photoacoustic tomography (QPAT) is to reconstruct inside the media. There have been extensive theoretical and com- putational studies on the inverse

Ren, Kui

210

Phase reference materials for photoacoustic spectroscopy  

Microsoft Academic Search

Interest in the phase of photoacoustic signals has increased greatly since the advent of phase modulation in FTIR spectroscopy. The photoacoustic phase provides information on the depth of the light-absorbing species within a solid sample. A spectroscopist needs data from a phase-reference material for standardizing phase measurements and for correcting the instrumental effects on the observed phase. Unfortunately, there is

R. Jones; S. Bajic; J. McClelland

1999-01-01

211

Photoacoustic measurement of refractive index of dye solutions and myoglobin for biosensing applications  

PubMed Central

Current methods of determining the refractive index of chemicals and materials, such as ellipsometry and reflectometry, are limited by their inability to analyze highly absorbing or highly transparent materials, as well as the required prior knowledge of the sample thickness and estimated refractive index. Here, we present a method of determining the refractive index of solutions using the photoacoustic effect. We show that a photoacoustic refractometer can analyze highly absorbing dye samples to within 0.006 refractive index units of a handheld optical refractometer. Further, we use myoglobin, an early non-invasive biomarker for malignant hyperthermia, as a proof of concept that this technique is applicable for use as a medical diagnostic. Comparison of the speed, cost, simplicity, and accuracy of the techniques shows that this photoacoustic method is well-suited for optically complex systems. PMID:24298407

Goldschmidt, Benjamin S.; Mehta, Smit; Mosley, Jeff; Walter, Chris; Whiteside, Paul J. D.; Hunt, Heather K.; Viator, John A.

2013-01-01

212

Characteristics of a photoacoustic air pollution detector at CO(2) laser frequencies.  

PubMed

The characteristics of a photoacoustic detection system for measurement of ambient trace atmospheric pollutants at CO(2) laser frequencies are analyzed and described. Several photoacoustic variables are optimized in this study. An alternate-traverse acoustic cell to eliminate cell window signals is described. An ac biased 16-cm(2) microphone is used. The observed modulation frequency dependence of the acoustic signal and a theoretical analysis are also presented. Trace gas interferents limit the practical sensitivity of the system, however, even with interferents present, a minimum measurable pressure change of 2.43 x 10(-9) atm, and apparent absorptivity of 8.42 x 10(-9)/cm was obtained. Techniques to minimize effects of interferents are reported along with the methodology of the photoacoustic technique in trace gas measurements. PMID:20212783

Adamowicz, R F; Koo, K P

1979-09-01

213

Differential Open Photoacoustic Helmholtz Cell  

NASA Astrophysics Data System (ADS)

There are very few designs of the open photoacoustic Helmholtz cells, and most of them exhibit very strong penetration of the external acoustic noise inside the cell. So far the best values of external acoustic noise suppression obtained in such cells were reported at the level of about 40 dB to 50 dB. This paper presents an open photoacoustic Helmholtz cell design with a differential signal detection. Both Helmholtz resonator cavities are equipped with microphones and connected with the exterior via duct-buffer-duct structures. The length and diameter of the ducts as well as volume of the acoustic buffers are selected in such a way that the acoustic impedance of the duct-buffer-duct structure at the frequency of light modulation is relatively high. As a result, the resonance of the cell is not damped, while penetration of the external acoustic noise inside the cell is strongly reduced. Preliminary analysis predicts attenuation of the external acoustic noise at the resonance frequency of the cell with a single microphone to be at the level of at least 60 dB. Additional rejection of the external acoustic noise can be obtained with differential detection, which simultaneously doubles the photoacoustic signal component; as in the Helmholtz resonator, pressure changes in the cavities are in counterphase.

Starecki, Tomasz; Geras, Antonina

2014-12-01

214

Energy harvesting from low frequency applications using piezoelectric materials  

NASA Astrophysics Data System (ADS)

In an effort to eliminate the replacement of the batteries of electronic devices that are difficult or impractical to service once deployed, harvesting energy from mechanical vibrations or impacts using piezoelectric materials has been researched over the last several decades. However, a majority of these applications have very low input frequencies. This presents a challenge for the researchers to optimize the energy output of piezoelectric energy harvesters, due to the relatively high elastic moduli of piezoelectric materials used to date. This paper reviews the current state of research on piezoelectric energy harvesting devices for low frequency (0-100 Hz) applications and the methods that have been developed to improve the power outputs of the piezoelectric energy harvesters. Various key aspects that contribute to the overall performance of a piezoelectric energy harvester are discussed, including geometries of the piezoelectric element, types of piezoelectric material used, techniques employed to match the resonance frequency of the piezoelectric element to input frequency of the host structure, and electronic circuits specifically designed for energy harvesters.

Li, Huidong; Tian, Chuan; Deng, Z. Daniel

2014-12-01

215

Coherent photoacoustic-ultrasound correlation and imaging.  

PubMed

Both photoacoustics and ultrasound have been researched extensively but separately. In this letter, we report an initial study on the coherent correlation between pulsed photoacoustic wave and pulse-echo ultrasound wave. By illuminating an object with a pulsed laser and external ultrasound sequentially, both the endogenous photoacoustic wave and pulse-echo ultrasound wave are received and coherently correlated, demonstrating enhanced signal-to-noise ratio. Image contrast of the proposed coherent photoacoustic-ultrasound imaging is also demonstrated to be improved significantly on vessel-mimicking phantom, due to fusion of the optical absorption and ultrasound reflection contrasts by coherent correlation of either conventional laser-induced photoacoustic imaging or pulse-echo ultrasound imaging separately. PMID:24801584

Gao, Fei; Feng, Xiaohua; Zheng, Yuanjin

2014-09-01

216

Light scattering effects in photoacoustic spectroscopy  

SciTech Connect

The influence of light scattering on photoacoustic signals is treated. Theoretical and experimental results are compared. The theoretical results are based on a model in which the photons diffuse through the sample. An equation governing the diffusion process is solved with appropriate boundary conditions. This gives the distribution of photons in the sample. The photoacoustic signal is then calculated and the result is compared with the result for nonscattering samples, giving the influence of the light scattering. The experimental results are obtained by measuring the photoacoustic signal for both scattering and nonscattering samples. The experimental and theoretical results are in good agreement. The differences are mainly due to the incompleteness of the original diffusion theory. An improved theory incorporating internal reflection at the sample surface is also analyzed. The paper illustrates the effects of light scattering on photoacoustic signals. It also shows how to estimate theoretically the photoacoustic signal from a light-scattering sample.

Helander, P.; Lundstroem, I.; McQueen, D.

1980-07-01

217

Magnetocaloric piezoelectric composites for energy harvesting  

NASA Astrophysics Data System (ADS)

Magnetocaloric alloy, Gd5Si2Ge2, was developed into a composite with the poly(vinylidene fluoride) (PVDF) piezoelectric polymer. This multifunctional material possesses unique properties that are suitable for energy conversion and harvesting. Experimental approaches include using an arc melting technique to synthesize the Gd5Si2Ge2 (GSG) alloy and the spinning casting method to fabricate the composite. The materials were characterized using various techniques at different length scales. These include atomic force microscopy (AFM), optical microscopy, scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS). The results indicated that the phase transformation of the magnetocaloric material close to its Curie temperature induced a significant increase in power generation in the piezoelectric polymer. The power output of a laminated structure was 1.1 mW, more than 200 thousand times higher than the piezoelectric materials alone (5.1 nW).

Cleveland, Michael; Liang, Hong

2012-04-01

218

Kinetic ceramics piezoelectric hydraulic pumps  

NASA Astrophysics Data System (ADS)

This paper discusses the development and testing of two Piezoelectrically driven Hydraulic Pumps (PHP2 & PHP3) utilizing low cost discrete multilayer piezoelectric actuators and low cost structural components. New valve technologies were developed utilizing reed and MEMS valves. Structural optimization was performed to decrease weight and volume. The PHP3 design extracts power from a PZT material with high efficiency despite impedance mismatch between the piezoelectric actuator and fluid by utilizing a hydraulic pendulum energy recovery technique. Hydraulic power of 168 watts can be developed with a pump mass of under 1lb. Flow rate of 2300 cc/min free flow has been demonstrated as well as output pressure greater than 200 bar in the stalled condition. The result of the effort is practical solid state conversion of electrical energy into a useable hydraulic source for actuation systems without having normal rotational wear components. The PHP2 pump was used to power the hydraulic primary flight controls in a RPV technology demonstrator flight tested in November 2006.

O'Neill, Conal; Burchfield, John

2007-04-01

219

In vivo combined photoacoustic and Doppler ultrasound imaging  

NASA Astrophysics Data System (ADS)

The long-term goal of our research is to develop photoacoustic and Doppler ultrasound imaging methods for noninvasive estimation of the oxygen consumption rate (MRO2) in vivo. Previously, we have demonstrated a combined photoacoustic and high-frequency Doppler ultrasound system and shown the feasibility of flow velocity and oxygen saturation (sO2) estimation using double-ink flow phantoms. In this work, the results of in vitro sheep blood experiments are presented. Blood oxygen flux has been estimated at different sO2 levels and mean flow speeds, and the uncertainty of the measurement has been quantified. In vivo experiments have been performed on Swiss Webster mice to provide coregistered photoacoustic and Doppler flow images with imaging depths of ~2mm. Doppler bandwidth broadening technique has been used to obtain transverse flow velocity. The diameter of the blood vessel is ~500?m and the mean flow speed is 15cm/s. We are working towards sO2 estimation in vivo and 3D oxygen consumption imaging of tumors at depths beyond OR-PAM.

Jiang, Yan; Harrison, Tyler; Forbrich, Alexander; Zemp, Roger J.

2012-02-01

220

Novel applications of photoacoustic spectroscopy in life sciences  

NASA Astrophysics Data System (ADS)

The Photoacoustic Spectroscopy, based on the generation of acoustic waves following the absorption of the modulated light by an enclosed material, was discovered in 1880 by Alexander Graham Bell. There are a lot of remarkable achievements in this topic since those days. It has been intended to present a relatively new tool to the researchers in biological areas and, simultaneously, to propose new fields of investigation to those who have been attracted by physics. The application of Photoacoustic trace gas detection to the determination of ethylene content in mice exhalation is described as a biomarker of free radicals production. It has been demonstrated the feasibility of studying the lipid peroxidation in vivo by this technique. Specifically, the results of ?-aminolevulinic acid administration in mice are presented. This drug has been used to induce Protoporphyrin IX production and ultimately to apply the Photodynamic Therapy, a recent method in cancer treatment. A kinetic study of Protoporphyrin IX production in mice skin and blood after ?-aminolevulinic acid administration in different doses is also shown. This study was performed using Photoacoustic Spectroscopy in solids.

Stolik, S.

2004-10-01

221

Potential for photoacoustic imaging of the neonatal brain  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging (PAI) has been proposed as a non-invasive technique for imaging neonatal brain injury. Since PAI combines many of the merits of both optical and ultrasound imaging, images with high contrast, high resolution, and a greater penetration depth can be obtained when compared to more traditional optical methods. However, due to the strong attenuation and reflection of photoacoustic pressure waves at the skull bone, PAI of the brain is much more challenging than traditional methods (e.g. near infrared spectroscopy) for optical interrogation of the neonatal brain. To evaluate the potential limits the skull places on 3D PAI of the neonatal brain, we constructed a neonatal skull phantom (1.4-mm thick) with a mixture of epoxy and titanium dioxide powder that provided acoustic insertion loss (1-5MHz) similar to human infant skull bone. The phantom was molded into a realistic infant skull shape by means of a CNCmachined mold that was based upon a 3D CAD model. To evaluate the effect of the skull bone on PAI, a photoacoustic point source was raster scanned within the phantom brain cavity to capture the imaging operator of the 3D PAI system (128 ultrasound transducers in a hemispherical arrangement) with and without the intervening skull phantom. The resultant imaging operators were compared to determine the effect of the skull layer on the PA signals in terms of amplitude loss and time delay.

Tavakolian, Pantea; Kosik, Ivan; Chamson-Reig, Astrid; St. Lawrence, Keith; Carson, Jeffrey J. L.

2013-03-01

222

Wood pulp characterization by a novel photoacoustic sensor  

NASA Astrophysics Data System (ADS)

In this paper we introduce a novel photoacoustic sensing technique that captures a photoacoustic signal excited by a laser light pulse after the light has propagated through a turbid medium. Simultaneously, the ultrasonic sound wave is captured after it has propagated through the same turbid medium. By combining the two signals, more information on the investigated medium can be obtained. Applications can be found in the pulp and paper industry where monitoring wood pulp compositions is of interest. Depending on its origin, pulp suspension contains different compositions of fibres and fibre fragments (fines). Poor control of the pulp composition leads to an unstable process that compromises the production, quality and energy efficiency in the pulp mill. The result shows the feasibility of the photoacoustic sensor in monitoring the mass fractions of fibres and fines in a pulp suspension. The first received echo, corresponding to the light interaction with the sample, showed a stronger correlation to the fines mass fraction compared to fibre mass fraction. The second echo, corresponding to the sound wave interaction with the sample, showed a much stronger correlation to fibre mass fraction than to fines mass fraction. Hence, it is proposed that by combining these two echoes, more information about the pulp suspension could be extracted than from any other sensor built on a single sensing principle.

Niemi, Jan; Löfqvist, Torbjörn

2012-08-01

223

Characterization of Lignin in Situ by Photoacoustic Spectroscopy  

PubMed Central

Photoacoustic spectroscopy is a recently developed nondestructive analytical technique that provides ultraviolet, visible, and infrared absorption spectra from intensely light scattering, solid, and/or optically opaque materials not suitable for conventional spectrophotometric analysis. In wood and other lignocellulosics, the principal ultraviolet absorption bands, in the absence of photosynthetic pigments, arise from the aromatic lignin component of the cell walls. Photoacoustic spectra of extracted lignin fragments (milled wood lignin) and synthetic lignin-like polymers contain a single major absorption band at 280 nanometers with an absorption tail extending beyond 400 nanometers. Photoacoustic spectra of pine, maple, and oak lignin in situ contain a broad primary absorption band at 300 nanometers and a longer wavelength shoulder around 370 nanometers. Wheat lignin in situ, on the other hand, exhibits two principle absorption peaks, at 280 nanometers and 320 nanometers. The presence of absorption bands at wavelengths greater than 300 nanometers in intact lignin could result from (a) interacting, nonconjugated chromophores, or (b) the presence of more highly conjugated structural components formed as the result of oxidation of the polymer. Evidence for the latter comes from the observation that, on the outer surface of senescent, field-dried wheat culms (stems), new absorption bands in the 350 to 400 nanometer region predominate. These new bands are less apparent on the outer surface of presenescent wheat culms and are virtually absent on the inner surface of either senescent or presenescent culms, suggesting that the appearance of longer wavelength absorption bands in senescent wheat is the result of accumulated photochemical modifications of the ligin polymer. These studies also demonstrate photoacoustic spectroscopy to be an important new tool for the investigation of insoluble plant components. PMID:16662709

Gould, J. Michael

1982-01-01

224

Adaptive piezoelectric sensoriactuator  

NASA Technical Reports Server (NTRS)

An adaptive algorithm implemented in digital or analog form is used in conjunction with a voltage controlled amplifier to compensate for the feedthrough capacitance of piezoelectric sensoriactuator. The mechanical response of the piezoelectric sensoriactuator is resolved from the electrical response by adaptively altering the gain imposed on the electrical circuit used for compensation. For wideband, stochastic input disturbances, the feedthrough capacitance of the sensoriactuator can be identified on-line, providing a means of implementing direct-rate-feedback control in analog hardware. The device is capable of on-line system health monitoring since a quasi-stable dynamic capacitance is indicative of sustained health of the piezoelectric element.

Clark, Jr., Robert L. (Inventor); Vipperman, Jeffrey S. (Inventor); Cole, Daniel G. (Inventor)

1996-01-01

225

Development of a MEMS-scale photoacoustic chemical sensor for trace vapor detection  

NASA Astrophysics Data System (ADS)

Photoacoustic spectroscopy (PAS) is a useful monitoring technique that is well suited for trace gas detection. This method routinely exhibits detection limits at the parts-per-million (ppm) or parts-per-billion (ppb) level for gaseous samples. PAS also possesses favorable detection characteristics when the system dimensions are scaled to a microsystem design. Micro-electromechanical systems (MEMS)-scale designs offer the possibility to develop photoacoustic sensors in which the signals would remain at sensitivities similar to or greater than those typically found in macro-scale devices. The objective of the present work is to develop a monolithic MEMS-scale photoacoustic trace gas sensor utilizing the Army Research Laboratory's chemical and biological sensing capability. In order to realize the advantage of photoacoustic sensor miniaturization, light sources of comparable size are required. Quantum cascade lasers (QCLs) have been tested in combination with MEMS-scale photoacoustic cells. This sensing platform has provided favorable detection limits for a standard nerve agent simulant. Current research employs this sensor scheme for the detection of 2,4-dinitrotoluene, a degradation product of TNT. Preliminary results describing the sensor capabilities and performance for the detection of this compound will be presented.

Holthoff, Ellen L.; Pellegrino, Paul M.

2009-05-01

226

Photoacoustic image reconstruction from few-detector and limited-angle data.  

PubMed

Photoacoustic tomography (PAT) is an emerging non-invasive imaging technique with great potential for a wide range of biomedical imaging applications. However, the conventional PAT reconstruction algorithms often provide distorted images with strong artifacts in cases when the signals are collected from few measurements or over an aperture that does not enclose the object. In this work, we present a total-variation-minimization (TVM) enhanced iterative reconstruction algorithm that can provide excellent photoacoustic image reconstruction from few-detector and limited-angle data. The enhancement is confirmed and evaluated using several phantom experiments. PMID:21991554

Yao, Lei; Jiang, Huabei

2011-09-01

227

Intravascular photoacoustic imaging of exogenously labeled atherosclerotic plaque through luminal blood  

PubMed Central

Abstract. Combined intravascular ultrasound and intravascular photoacoustic (IVUS/IVPA) imaging has been previously established as a viable means for assessing atherosclerotic plaque morphological and compositional characteristics using both endogenous and exogenous contrast. In this study, IVUS/IVPA imaging of atherosclerotic rabbit aortas following systemic injection of gold nanorods (AUNRs) with peak absorbance within the tissue optical window is performed. Ex vivo imaging results reveal a high photoacoustic signal from localized AUNRs in regions with atherosclerotic plaques. Corresponding histological staining further confirms the preferential extravasation of AUNRs in atherosclerotic regions with compromised luminal endothelium and acute inflammation. The ability to detect AUNRs using combined IVUS and photoacoustic imaging in the presence of luminal saline and luminal blood is evaluated using both spectroscopic and single wavelength IVPA imaging techniques. Results demonstrate that AUNR detection within the arterial wall can be achieved using both methods, even in the case of imaging through luminal blood. PMID:23224013

Yeager, Doug; Karpiouk, Andrei; Wang, Bo; Amirian, James; Sokolov, Konstantin; Smalling, Richard; Emelianov, Stanislav

2012-01-01

228

Gold nanoparticle targeted photoacoustic cavitation for potential deep tissue imaging and therapy  

PubMed Central

The laser generation of vapor bubbles around plasmonic nanoparticles can be enhanced through the application of an ultrasound field; a technique referred to as photoacoustic cavitation. The combination of light and ultrasound allows for bubble formation at lower laser fluence and peak negative ultrasound pressure than can be achieved using either modality alone. The growth and collapse of these bubbles leads to local mechanical disruption and acoustic emission, and can potentially be used to induce and monitor tissue therapy. Photoacoustic cavitation is investigated for a broad range of ultrasound pressures and nanoparticle concentrations for gold nanorods and nanospheres. The cavitation threshold fluences for both nanoparticle types are found to drastically reduce in the presence of an ultrasound field. The results indicate that photoacoustic cavitation can potentially be produced at depth in biological tissue without exceeding the safety limits for ultrasound or laser radiation at the tissue surface. PMID:23304648

Ju, Hengyi; Roy, Ronald A.; Murray, Todd W.

2012-01-01

229

Intravascular photoacoustic imaging of exogenously labeled atherosclerotic plaque through luminal blood  

NASA Astrophysics Data System (ADS)

Combined intravascular ultrasound and intravascular photoacoustic (IVUS/IVPA) imaging has been previously established as a viable means for assessing atherosclerotic plaque morphological and compositional characteristics using both endogenous and exogenous contrast. In this study, IVUS/IVPA imaging of atherosclerotic rabbit aortas following systemic injection of gold nanorods (AUNRs) with peak absorbance within the tissue optical window is performed. Ex vivo imaging results reveal a high photoacoustic signal from localized AUNRs in regions with atherosclerotic plaques. Corresponding histological staining further confirms the preferential extravasation of AUNRs in atherosclerotic regions with compromised luminal endothelium and acute inflammation. The ability to detect AUNRs using combined IVUS and photoacoustic imaging in the presence of luminal saline and luminal blood is evaluated using both spectroscopic and single wavelength IVPA imaging techniques. Results demonstrate that AUNR detection within the arterial wall can be achieved using both methods, even in the case of imaging through luminal blood.

Yeager, Doug; Karpiouk, Andrei; Wang, Bo; Amirian, James; Sokolov, Konstantin; Smalling, Richard; Emelianov, Stanislav

2012-10-01

230

Initial results of imaging melanoma metastasis in resected human lymph nodes using photoacoustic computed tomography  

NASA Astrophysics Data System (ADS)

The pathological status of the sentinel lymph node is important for accurate melanoma staging, ascertaining prognosis and planning treatment. The standard procedure involves biopsy of the node and histopathological assessment of its status. Drawbacks of this examination include a finite sampling of the node with the likelihood of missing metastases, and a significant time-lag before histopathological results are available to the surgeon. We studied the applicability of photoacoustic computed tomographic imaging as an intraoperative modality for examining the status of resected human sentinel lymph nodes. We first applied the technique to image ex vivo pig lymph nodes carrying metastases-simulating melanoma cells using multiple wavelengths. The experience gained was applied to image a suspect human lymph node. We validated the photoacoustic imaging results by comparing a reconstructed slice with a histopathological section through the node. Our results suggest that photoacoustics has the potential to develop into an intraoperative imaging method to detect melanoma metastases in sentinel lymph nodes.

Jose, Jithin; Grootendorst, Diederik J.; Vijn, Thomas W.; Wouters, Michel W.; van Boven, Hester; van Leeuwen, Ton G.; Steenbergen, Wiendelt; Ruers, Theo J. M.; Manohar, Srirang

2011-09-01

231

Correcting photoacoustic signals for fluence variations using acousto-optic modulation.  

PubMed

We present a theoretical concept which may lead to quantitative photoacoustic mapping of chromophore concentrations. The approach supposes a technique capable of tagging light in a well-defined tagging volume at a specific location deep in the medium. We derive a formula that expresses the local absorption coefficient inside a medium in terms of noninvasively measured quantities and experimental parameters and we validate the theory using Monte Carlo simulations. Furthermore, we performed an experiment to basically validate the concept as a strategy to correct for fluence variations in photoacoustics. In the experiment we exploit the possibility of acousto-optic modulation, using focused ultrasound, to tag photons. Results show that the variation in photoacoustic signals of absorbing insertions embedded at different depths in a phantom, caused by fluence variations of more than one order of magnitude, can be corrected for to an accuracy of 5%. PMID:22714476

Daoudi, K; Hussain, A; Hondebrink, E; Steenbergen, W

2012-06-18

232

Estimating optical absorption, scattering, and Grueneisen distributions with multiple-illumination photoacoustic tomography.  

PubMed

While photoacoustic methods offer significant promise for high-resolution optical contrast imaging, quantification has thus far proved challenging. In this paper, a noniterative reconstruction technique for producing quantitative photoacoustic images of both absorption and scattering perturbations is introduced for the case when the optical properties of the turbid background are known and multiple optical illumination locations are used. Through theoretical developments and computational examples, it is demonstrated that multiple-illumination photoacoustic tomography (MI-PAT) can alleviate ill-posedness due to absorption-scattering nonuniqueness and produce quantitative high-resolution reconstructions of optical absorption, scattering, and Gruneisen parameter distributions. While numerical challenges still exist, we show that the linearized MI-PAT framework that we propose has orders of magnitude improved condition number compared with CW diffuse optical tomography. PMID:21743514

Shao, Peng; Cox, Ben; Zemp, Roger J

2011-07-01

233

Broadband pulsed flow using piezoelectric microjets  

NASA Astrophysics Data System (ADS)

A piezohydraulic microjet design and experimental results are presented to demonstrate broadband active flow control for applications on various aircraft structures including impinging jets, rotor blades, cavity bays, etc. The microjet actuator includes a piezoelectric stack actuator and hydraulic circuit that is used to throttle a 400 ?m diameter microjet using hydraulic amplification of the piezoelectric stack actuator. This system is shown to provide broadband pulsed flow actuation up to 800 Hz. Unsteady pressure measurements of the microjet's exit flow are coupled with high-speed phase imagery using micro-Schlieren techniques to quantify the flow field. These results are compared with in situ stack actuator displacements using strain gauge measurements.

Hogue, Joshua; Solomon, John; Hays, Michael; Alvi, Farrukh; Oates, William

2010-04-01

234

Piezoelectric Polymer Shock Gauges  

NASA Astrophysics Data System (ADS)

The science and technology of piezoelectric materials has long been dominated by the availability of specific materials with particular properties. Piezoelectric PVDF (Poly(vinylidene fluoride) polymer and copolymers of PVDF with trifluoroethylene have shown to have the potential for new shock-wave sensors. Since 1981 through 1995, the piezoelectric response of PVDF was studied in a cooperative effort with François Bauer of ISL, France, R.A. Graham of Sandia National Laboratories and L.M. Lee of Ktech Corporation, Albuquerque. Among the known piezoelectric polymers, the PVDF plays an important role in measuring mechanical and physical state of matter under shock loading. The present paper presents the history of the development of the PVDF gauge. After 24 years of research in this area, main relevant results and data obtained are summarized as well as some original applications of the PVDF gauges.

Bauer, F.

2006-07-01

235

Effect of cement-polymer ratio on 1-3 piezoelectric composites  

NASA Astrophysics Data System (ADS)

A 1-3 type piezoelectric composite was fabricated by cut-filling technique. The effects of cement-polymer ratio on piezoelectric and dielectric properties of the composites were analyzed. The results show that piezoelectric strain factor d33 and piezoelectric voltage factor g33 exhibit the trend of decrease initially and then increase with increasing cement-polymer ratio. With the increase of cement-polymer ratio, the dielectric factor ?r and dielectric loss tan? of the composites increase initially and then decrease. Comparing with pure piezoelectric ceramic, the mechanical quality factor Qm decreases obviously. Acoustic impedance Z is about 9 M raly, which is matching with concrete.

Guo, Lili; Xu, Dongyu; Huang, Shifeng

2009-07-01

236

Photoacoustic resonance spectroscopy for biological tissue characterization  

NASA Astrophysics Data System (ADS)

By "listening to photons," photoacoustics allows the probing of chromosomes in depth beyond the optical diffusion limit. Here we report the photoacoustic resonance effect induced by multiburst modulated laser illumination, which is theoretically modeled as a damped mass-string oscillator and a resistor-inductor-capacitor (RLC) circuit. Through sweeping the frequency of multiburst modulated laser, the photoacoustic resonance effect is observed experimentally on phantoms and porcine tissues. Experimental results demonstrate different spectra for each phantom and tissue sample to show significant potential for spectroscopic analysis, fusing optical absorption and mechanical vibration properties. Unique RLC circuit parameters are extracted to quantitatively characterize phantom and biological tissues.

Gao, Fei; Feng, Xiaohua; Zheng, Yuanjin; Ohl, Claus-Dieter

2014-06-01

237

Photoacoustic effect in a periodically modulated structure  

NASA Astrophysics Data System (ADS)

We discuss the photoacoustic effect in one-dimensional phononic structures with sinusoidal modulation of its acoustic properties. The periodic structure is considered to have a modulation in its density or compressibility of the form 1-2?(2?xa), where ? is the modulation factor and a is the periodic length of the phononic structures. The properties of the photoacoustic waves are determined by an inhomogeneous Mathieu equation. We give several different methods including Green's function solutions, series expansions, and variation of parameters solutions for determining closed from solutions to the inhomogeneous Mathieu equation to obtain the properties of the photoacoustic effect.

Wu, Binbin; Diebold, Gerald

2011-04-01

238

Photoacoustic phasoscopy super-contrast imaging  

SciTech Connect

Phasoscopy is a recently proposed concept correlating electromagnetic (EM) absorption and scattering properties based on energy conservation. Phase information can be extracted from EM absorption induced acoustic wave and scattered EM wave for biological tissue characterization. In this paper, an imaging modality, termed photoacoustic phasoscopy imaging (PAPS), is proposed and verified experimentally based on phasoscopy concept with laser illumination. Both endogenous photoacoustic wave and scattered photons are collected simultaneously to extract the phase information. The PAPS images are then reconstructed on vessel-mimicking phantom and ex vivo porcine tissues to show significantly improved contrast than conventional photoacoustic imaging.

Gao, Fei; Feng, Xiaohua; Zheng, Yuanjin, E-mail: yjzheng@ntu.edu.sg [School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798 (Singapore)

2014-05-26

239

Photoacoustic shock generation in carbon suspensions  

SciTech Connect

This letter discusses photoacoustic shock wave generation and the origin of nonlinear sound wave generation in carbon suspensions. The Burgers equation for an inviscid fluid is solved for an exponential acoustic wave. The solution shows an increasingly steep wave form that gradually coalesces into a shock front. Large dynamic range measurements of photoacoustic waves generated by a pulsed-laser beam in carbon suspensions show the pressure in the wave to depart significantly from the predictions of linear response theory. Acoustic sound speed and amplitude measurements indicate that weak shocks are produced from the photoacoustic sound generation process rather than from nonlinear propagational effects. (c) 1999 American Institute of Physics.

Beveridge, Andrew C. [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States)] [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States); McGrath, Thomas E. [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States)] [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States); Diebold, Gerald J. [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States)] [Department of Chemistry, Brown University, Providence, Rhode Island 02912 (United States); Karabutov, Alexander A. [International Laser Center, Moscow State University, Moscow, Russia (Russian Federation)] [International Laser Center, Moscow State University, Moscow, Russia (Russian Federation)

1999-12-27

240

In vivo optically encoded photoacoustic flowgraphy  

PubMed Central

We present an optically encoded photoacoustic flow imaging method based on optical-resolution photoacoustic microscopy. An intensity-modulated continuous-wave laser photothermally encodes the flowing medium, and a pulsed laser generates photoacoustic waves to image the encoded heat pattern. Flow speeds can be calculated by cross-correlation. The method was validated in phantoms, at flow speeds ranging from 0.23 mm/s to 11 mm/s. Venous blood flow speed in a mouse ear was also measured. PMID:24978744

Zhang, Ruiying; Wang, Lidai; Yao, Junjie; Yeh, Cheng-Hung; Wang, Lihong V.

2014-01-01

241

Laminated piezoelectric transformer  

NASA Technical Reports Server (NTRS)

A laminated piezoelectric transformer is provided using the longitudinal vibration modes for step-up voltage conversion applications. The input portions are polarized to deform in a longitudinal plane and are bonded to an output portion. The deformation of the input portions is mechanically coupled to the output portion, which deforms in the same longitudinal direction relative to the input portion. The output portion is polarized in the thickness direction relative its electrodes, and piezoelectrically generates a stepped-up output voltage.

Vazquez Carazo, Alfredo (Inventor)

2006-01-01

242

Piezoelectric Energy Harvesting Solutions  

PubMed Central

This paper reviews the state of the art in piezoelectric energy harvesting. It presents the basics of piezoelectricity and discusses materials choice. The work places emphasis on material operating modes and device configurations, from resonant to non-resonant devices and also to rotational solutions. The reviewed literature is compared based on power density and bandwidth. Lastly, the question of power conversion is addressed by reviewing various circuit solutions. PMID:24618725

Caliò, Renato; Rongala, Udaya Bhaskar; Camboni, Domenico; Milazzo, Mario; Stefanini, Cesare; de Petris, Gianluca; Oddo, Calogero Maria

2014-01-01

243

Quartz enhanced photoacoustic spectroscopy (QEPAS) with antimonide compounds in very compact systems  

NASA Astrophysics Data System (ADS)

We present in this paper measurements made by quartz enhanced photoacoustic spectroscopy (QEPAS) technique with antimonide laser diodes emitting at 2.3 ?m and 3.3 ?m. These measurements dedicated to environmental purposes allow us sensitive detection of ethylene and methane. Two experimental setups are reported: a laboratory and brand new compact benches. The detection limits are mentioned.

Nguyen Ba, T.; Triki, M.; Gaimard, Quentin; Rouillard, Y.; Vicet, A.

2014-05-01

244

DEVELOPMENT OF A BREADBOARD CO2 LASER PHOTOACOUSTIC TOXIC VAPOR MONITOR  

EPA Science Inventory

The report describes the development of a breadboard version of a CO2 laser photoacoustic (LPA) detector. The CO2 LPA technique has been demonstrated to be capable of detecting, with high specificity, a variety of toxic compounds at low parts-per-billion (ppb) levels in multicomp...

245

Photoacoustic, Photothermal, and Diffusion-Wave Sciences in the Twenty-First Century: Triumphs of the Past Set the Trends for the Future  

NASA Astrophysics Data System (ADS)

A handful of early breakthroughs in photoacoustic science and engineering since its modern-day (scientific) renaissance in the 1970s has defined directions in the development of the photoacoustic, photothermal, and diffusion-wave fields in the past 40 years that have shaped modern day developments and have led to an impressive range of vibrant and unique technologies in the third millennium (technological renaissance). A power-point presentation on the ICPPP-16 opening plenary talk focuses on the historical roots of what I perceive to be some of today's most successful and unique technologies, while readily acknowledging the impossibility to be all inclusive. It can be found under the url: http://cadift.mie.utoronto.ca/History_of_Photoacoustics-Photothermics.ppt. The thematic areas in question include historical reviews selected among the following topics: Piezoelectric photoacoustic microscopy (PAM) which, along with early gas-phase PA spectroscopic studies of biomaterials such as blood haemoglobin and progress in the physics of photon diffusion waves, has led to the modern-day explosion in biomedical photoacoustic imaging technologies with future trends for photoacoustic and ultrasound co-registered imagers; Thermoreflectance, piezoelectric, and gas-phase PA imaging of semiconductors which, along with developments in photocarrier diffusion wave physics, led to photocarrier radiometry, nanolayer diagnostics, carrierographic imaging of optoelectronic materials, and devices with industrial trends in solar cell inspection and control; Photoacoustic gas-phase and infrared radiometric probing and scanning imaging NDE which led to lock-in thermography and have spawned industrial and biomedical technologies; Thermal-wave interferometry and the quest for thermal coherence which led to thermal-wave cavities, the thermal-wave radar, and derivative depth profiling technologies, and, very recently, thermal coherence tomography. This review is meant to be a growing public record of work in progress, with new materials in the given thematic areas and other thematic areas being added as more information on the rich history of the field becomes available. Direct inputs to the author by the broader photoacoustic, photothermal, and diffusion-wave community are solicited and strongly encouraged to ensure that all landmark and seminal work that shaped the state of the science and art in the field receives fair and deserving exposure and the historical review becomes truly representative and comprehensive.

Mandelis, Andreas

2012-11-01

246

Piezoelectric dilatometric analysis using homodyne and heterodyne laser interferometry  

NASA Astrophysics Data System (ADS)

The electromechanical coupling of piezoelectric materials has been widely studied since such property is found to be a key element of enhanced sensitivity in piezoelectric sensors or actuators. However a unified view of this coupling as function of frequencies verified using multiple measurement techniques has not previously been available. This study examines and compares multiple optical based homodyne and heterodyne interferometry techniques for piezoelectric displacement measurement, over a wide range of frequencies from DC to 20 MHz. A custom configured homodyne optical interferometer and a commercial heterodyne Laser Doppler Vibrometer are used in the study. Because the frequency ranges used by these devices overlap, it is possible to compare the results. Ferroelectric lead titanate PbTiO3 (PT) ceramic sample with high ferroelectric strain is studied in this work. Frequency dependence of the electromechanical displacement is obtained using multiple techniques and the emphasis of the interrogations is given to frequencies near piezoelectric resonances.

Delahoussaye, Keith

247

Photoacoustic endoscopy Joon-Mo Yang,1  

E-print Network

penetrations limited by the transport mean- free path ( 1 mm in the skin) [5­7]; consequently, much interest- graph of the distal end of our photoacoustic endo- scopic probe. In the probe, a light-guiding optical

Wang, Lihong

248

Noise-equivalent sensitivity of photoacoustics  

PubMed Central

Abstract. The fundamental limitations of photoacoustic microscopy for detecting optically absorbing molecules are investigated both theoretically and experimentally. We experimentally demonstrate noise-equivalent detection sensitivities of 160,000 methylene blue molecules (270 zeptomol or 2.7×10?19??mol) and 86,000 oxygenated hemoglobin molecules (140 zeptomol) using narrowband continuous-wave photoacoustics. The ultimate sensitivity of photoacoustics is fundamentally limited by thermal noise, which can present in the acoustic detection system as well as in the medium itself. Under the optimized conditions described herein and using commercially available detectors, photoacoustic microscopy can detect as few as 100s of oxygenated hemoglobin molecules. Realizable improvements to the detector may enable single molecule detection of select molecules. PMID:24026425

Winkler, Amy M.; Maslov, Konstantin; Wang, Lihong V.

2013-01-01

249

Photoacoustic excitation profiles of gold nanoparticles?  

PubMed Central

The wavelength dependence of the laser-induced photoacoustic signal amplitude has been measured for water dispersions of 10, 61, and 93 nm diameter gold nanospheres. The whole region of the localized surface plasmon resonance has been covered. This “photoacoustic excitation profile” can be overlayed with the extinction spectrum between 450 nm and 600 nm in the case of the smallest nanoparticles. At variance, the larger-sized nanoparticles display a progressive deviation from the extinction spectrum at longer wavelength, where the photoacoustic signal becomes relatively smaller. Considering that photoacoustics is intrinsically insensitive to light scattering, at least for optically thin samples, the results are in agreement with previous theoretical work predicting (i) an increasing contribution of scattering to extinction when the nanoparticle size increases and (ii) a larger scattering component at longer wavelengths. Therefore, the method has a general validity and can be applied to selectively determine light absorption by plasmonic systems. PMID:25302155

Feis, Alessandro; Gellini, Cristina; Salvi, Pier Remigio; Becucci, Maurizio

2014-01-01

250

Photoacoustic Imaging for Cancer Detection and Staging  

PubMed Central

Cancer is one of the leading causes of death in the world. Diagnosing a cancer at its early stages of development can decrease the mortality rate significantly and reduce healthcare costs. Over the past two decades, photoacoustic imaging has seen steady growth and has demonstrated notable capabilities to detect cancerous cells and stage cancer. Furthermore, photoacoustic imaging combined with ultrasound imaging and augmented with molecular targeted contrast agents is capable of imaging cancer at the cellular and molecular level, thus opening diverse opportunities to improve diagnosis of tumors, detect circulating tumor cells and identify metastatic lymph nodes. In this paper we introduce the principles of photoacoustic imaging, and review recent developments in photoacoustic imagingas an emerging imaging modality for cancer diagnosis and staging. PMID:24032095

Mehrmohammadi, Mohammad; Yoon, Soon Joon; Yeager, Douglas; Emelianov, Stanislav Y.

2013-01-01

251

Photoacoustic photonic crystal fiber gas sensor  

E-print Network

Photoacoustic spectroscopy (PAS) is a form of laser spectroscopy that has demonstrated very high sensitivity for gas detection. Typically, PAS involves the absorption of a modulated laser beam by the gas species of interest, ...

Chen, Raymond, M. Eng. Massachusetts Institute of Technology

2007-01-01

252

Photoacoustic excitation profiles of gold nanoparticles.  

PubMed

The wavelength dependence of the laser-induced photoacoustic signal amplitude has been measured for water dispersions of 10, 61, and 93 nm diameter gold nanospheres. The whole region of the localized surface plasmon resonance has been covered. This "photoacoustic excitation profile" can be overlayed with the extinction spectrum between 450 nm and 600 nm in the case of the smallest nanoparticles. At variance, the larger-sized nanoparticles display a progressive deviation from the extinction spectrum at longer wavelength, where the photoacoustic signal becomes relatively smaller. Considering that photoacoustics is intrinsically insensitive to light scattering, at least for optically thin samples, the results are in agreement with previous theoretical work predicting (i) an increasing contribution of scattering to extinction when the nanoparticle size increases and (ii) a larger scattering component at longer wavelengths. Therefore, the method has a general validity and can be applied to selectively determine light absorption by plasmonic systems. PMID:25302155

Feis, Alessandro; Gellini, Cristina; Salvi, Pier Remigio; Becucci, Maurizio

2014-03-01

253

Toward in-vivo photoacoustic imaging of human ovarian tissue for cancer detection  

NASA Astrophysics Data System (ADS)

Currently, most of the cancers in the ovary are detected when they have already metastasized to other parts of the body. As a result, ovarian cancer has the highest mortality of all gynecological cancers with a 5-year survival rate of 30% or less [1]. The reason is the lack of reliable symptoms as well as the lack of efficacious screening techniques [2,3]. Thus, there is an urgent need to improve the current diagnostic techniques. We have investigated the potential role of co-registered photoacoustic and ultrasound imaging in ovarian cancer detection. In an effort to bring this technique closer to clinical application, we have developed a co-registered ultrasound and photoacoustic transvaginal probe. A fiber coupling assembly has been developed to deliver the light from around the transducer for reflection geometry imaging. Co-registered ultrasound and photoacoustic images of swine ovaries through vagina wall muscle and human ovaries using the aforementioned probe, demonstrate the potential of photoacoustic imaging to non-invasively detect ovarian cancer in vivo.

Aguirre, Andres; Kumavor, Patrick; Ardeshirpour, Yasaman; Sanders, Mary M.; Brewer, Molly; Zhu, Quing

2011-03-01

254

Reflection-mode multiple-illumination photoacoustic sensing to estimate optical properties?  

PubMed Central

Objectives We analyze a reflection-mode multiple-illumination photoacoustic method which allows us to estimate optical scattering properties of turbid media based on fitting light-transport models and explore its limits in optical property estimation and depth-dependent fluence compensation. Background Recent simulation results show significant promise for a technique called multiple-illumination photoacoustic tomography (MI-PAT) to quantitatively reconstruct both absorption and scattering heterogeneities in turbid medium. Prior to experiments, it is essential to develop and analyze a measurement technique and probe capabilities of quantitative measurements that focus on sensing rather than imaging. Methods This technique involved translation of a 532 nm pulsed-laser light spot while focusing an ultrasound receiver on a sub-surface optical absorber immersed in a scattering medium at 3, 4 and 5 mm below the surface. Measured photoacoustic amplitudes for media with different reduced scattering coefficients are fitted with a light propagation model to estimate optical properties. Results When the absorber was located at 5 mm below the membrane in media with a reduced scattering coefficient of 4.4 and 5.5 cm?1, the true values were predicted with an error of 5.7% and 12.7%, respectively. We observe accuracy and the ability of estimating optical scattering properties decreased with the increased reduced scattering coefficient. Nevertheless, the estimated parameters were sufficient for demonstrating depth-dependent fluence compensation for improved quantitation in photoacoustic imaging. PMID:25302153

Ranasinghesagara, Janaka C.; Jiang, Yan; Zemp, Roger J.

2013-01-01

255

Comparisons of a conventional photoacoustic cell with an acoustic window photoacoustic cell  

Microsoft Academic Search

A conventional photoacoustic measurement cell is compared with the newly developed acoustic window photoacoustic window cell both theoretically and experimentally using liquid and power samples. The results indicate that the signal strengths from the two cell types are about equal for liquid samples in practical cells. This is important since the acoustic window cell was developed with applications to on-line

D. H. McQueen

1982-01-01

256

Piezoelectric Ceramics and Their Applications  

ERIC Educational Resources Information Center

Describes the piezoelectric effect in ceramics and presents a quantitative representation of this effect. Explains the processes involved in the manufacture of piezoelectric ceramics, the materials used, and the situations in which they are applied. (GS)

Flinn, I.

1975-01-01

257

Phase reference materials for photoacoustic spectroscopy  

SciTech Connect

Interest in the phase of photoacoustic signals has increased greatly since the advent of phase modulation in FTIR spectroscopy. The photoacoustic phase provides information on the depth of the light-absorbing species within a solid sample. A spectroscopist needs data from a phase-reference material for standardizing phase measurements and for correcting the instrumental effects on the observed phase. Unfortunately, there is no universally accepted phase-reference material. The authors have studied the photoacoustic-signal phase and magnitude behavior for several potential phase-reference materials as a function of experimental parameters, such as beam modulation frequency, sample position in the photoacoustic cell, and cell purge gas. Theoretically, an ideal surface-absorbing material would have a photoacoustic phase that trails the phase of the excitation light by 90{degree}. They have found no material with this behavior, although some come close under a limited range of conditions. The three samples were separately sealed in the photoacoustic detector and illuminated by a red LED that was modulated at selected frequencies. The phases of the samples vary rapidly at very low frequencies because of the response of the cell microphone. Above that range, all three are within 10{degree} of the ideal 90{degree}, but each varies linearly with frequency with a different slope. The behaviors of these and other samples will be discussed in detail.

Jones, R.; Bajic, S. [Ames Lab., IA (United States); McClelland, J. [Ames Lab., IA (United States)]|[MTEC Photoacoustics, Ames, IA (United States)

1999-06-01

258

High temperature piezoelectric drill  

NASA Astrophysics Data System (ADS)

The current NASA Decadal mission planning effort has identified Venus as a significant scientific target for a surface in-situ sampling/analyzing mission. The Venus environment represents several extremes including high temperature (460°C), high pressure (~9 MPa), and potentially corrosive (condensed sulfuric acid droplets that adhere to surfaces during entry) environments. This technology challenge requires new rock sampling tools for these extreme conditions. Piezoelectric materials can potentially operate over a wide temperature range. Single crystals, like LiNbO3, have a Curie temperature that is higher than 1000°C and the piezoelectric ceramics Bismuth Titanate higher than 600°C. A study of the feasibility of producing piezoelectric drills that can operate in the temperature range up to 500°C was conducted. The study includes the high temperature properties investigations of engineering materials and piezoelectric ceramics with different formulas and doping. The drilling performances of a prototype Ultrasonic/Sonic Drill/Corer (USDC) using high temperate piezoelectric ceramics and single crystal were tested at temperature up to 500°C. The detailed results of our study and a discussion of the future work on performance improvements are presented in this paper.

Bao, Xiaoqi; Scott, James; Boudreau, Kate; Bar-Cohen, Yoseph; Sherrit, Stewart; Badescu, Mircea; Shrout, Tom; Zhang, Shujun

2009-03-01

259

Direct measurement of piezoelectric shear coefficient  

NASA Astrophysics Data System (ADS)

Piezoelectric materials exhibit electromechanical coupling which has led to their widespread application for sensors, actuators, and energy harvesters. These materials possess anisotropic behavior with the shear coefficient, and have the largest electromechanical coupling coefficient. However, the shear mode is difficult to measure with existing techniques and thus has not been fully capitalized upon in recent devices. Better understanding of the full shear response with respect to the driving electric field would significantly help the design of optimized piezoelectric shear devices. Here, a simple and low cost direct measurement method based on digital image correlation is developed to characterize the shear response of piezoelectric materials and its nonlinear behavior as a function of external field. The piezoelectric shear coefficient (d15) of a commercial shear plate actuator is investigated in both bipolar and unipolar electric fields. Two different nonlinearities and hysteresis behaviors of the actuators were observed, and the relation between the driving field amplitude and the corresponding d15 coefficient is determined. Moreover, the measured transverse displacement of the plate actuator in simple shear condition is validated through a laser interferometry technique.

Malakooti, Mohammad H.; Sodano, Henry A.

2013-06-01

260

Development of a neonatal skull phantom for photoacoustic imaging  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging (PAI) has been proposed as a non-invasive technique for the diagnosis and monitoring of disorders in the neonatal brain. However, PAI of the brain through the intact skull is challenging due to reflection and attenuation of photoacoustic pressure waves by the skull bone. The objective of this work was to develop a phantom for testing the potential limits the skull bone places on PAI of the neonatal brain. Our approach was to make acoustic measurements on materials designed to mimic the neonatal skull bone and construct a semi-realistic phantom. A water tank and two ultrasound transducers were utilized to measure the ultrasound insertion loss (100 kHz to 5MHz) of several materials. Cured mixtures of epoxy and titanium dioxide powder provided the closest acoustic match to neonatal skull bone. Specifically, a 1.4-mm thick sample composed of 50% (by mass) titanium dioxide powder and 50% epoxy was closest to neonatal skull bone in terms of acoustic insertion loss. A hemispherical skull phantom (1.4 mm skull thickness) was made by curing the epoxy/titanium dioxide powder mixture inside a mold. The mold was constructed using 3D prototyping techniques and was based on the hairless head of a realistic infant doll. The head was scanned to generate a 3D model, which in turn was used to build a 3D CAD version of the mold. The mold was CNC machined from two solid blocks of Teflon®. The neonatal skull phantom will enable the study of the propagation of photoacoustic pressure waves under a variety of experimental conditions.

Tavakolian, Pantea; Todd, Rhiannon; Kosik, Ivan; Chamson-Reig, Astrid; Vasefi, Fartash; St. Lawrence, Keith; Carson, Jeffrey J. L.

2013-03-01

261

Theoretical and experimental investigation of multispectral photoacoustic osteoporosis detection method  

NASA Astrophysics Data System (ADS)

Osteoporosis is a widespread disorder, which has a catastrophic impact on patients lives and overwhelming related to healthcare costs. Recently, we proposed a multispectral photoacoustic technique for early detection of osteoporosis. Such technique has great advantages over pure ultrasonic or optical methods as it allows the deduction of both bone functionality from the bone absorption spectrum and bone resistance to fracture from the characteristics of the ultrasound propagation. We demonstrated the propagation of multiple acoustic modes in animal bones in-vitro. To further investigate the effects of multiple wavelength excitations and of induced osteoporosis on the PA signal a multispectral photoacoustic system is presented. The experimental investigation is based on measuring the interference of multiple acoustic modes. The performance of the system is evaluated and a simple two mode theoretical model is fitted to the measured phase signals. The results show that such PA technique is accurate and repeatable. Then a multiple wavelength excitation is tested. It is shown that the PA response due to different excitation wavelengths revels that absorption by the different bone constitutes has a profound effect on the mode generation. The PA response is measured in single wavelength before and after induced osteoporosis. Results show that induced osteoporosis alters the measured amplitude and phase in a consistent manner which allows the detection of the onset of osteoporosis. These results suggest that a complete characterization of the bone over a region of both acoustic and optical frequencies might be used as a powerful tool for in-vivo bone evaluation.

Steinberg, Idan; Hershkovich, Hadas Sara; Gannot, Israel; Eyal, Avishay

2014-03-01

262

Theoretical analysis of pulse photoacoustic effect in gas filled cell  

Microsoft Academic Search

Pulse photoacoustic effect in solids is a fondation of nondestructive data acquisition method describing thermal properties of solid samples. Pulse research ray be carried out using facilities developed for photoacoustic, continuous wave investigation, but proper interpretation of results obtained in a particular experimental setup requires that a theoretical model be developed. In this paper a one-dimensional model of four-segmeent photoacoustic

R. J. Bukowski; A. Domanowska

2003-01-01

263

Laser photoacoustic microscopy of mechanical stresses in modern materials  

Microsoft Academic Search

This paper presents the main experimental and theoretical results so far obtained in the detection of internal stresses by the photoacoustic method in brittle and plastic materials. Examples are presented of typical photoacoustic images of sections of Vickers-indented ceramics and metals. The main assumptions of the nonlinear model of the photoacoustic effect in stressed materials are formulated, taking into account

K. L. Muratikov; A. L. Glazov

2006-01-01

264

Active Piezoelectric Diaphragms  

NASA Technical Reports Server (NTRS)

Several active piezoelectric diaphragms were fabricated by placing unelectroded piezoelectric disks between copper clad films patterned with Inter-Circulating Electrodes "ICE". When a voltage potential is applied to the electrodes, the result is radially distributed electric field that mechanically strains the piezo-ceramic along the Z-axis (perpendicular to the applied electric field), rather than the expected in-plane (XY-axis) direction. Unlike other out of plane piezoelectric actuators, which are benders, these Radial Field Diaphragms (RFDs) strain concentrically yet afford high displacements while maintaining a constant circumference. This paper covers the fabrication and characterization of these diaphragms as a function of poling field strength, ceramic diameter and line spacing, as well as the surface topography, the resulting strain field and displacement as a function of applied voltage ranging from DC to 10 Hz.

Bryant, Robert G.; Effinger, Robert T., IV; Aranda, Isaiah, Jr.; Copeland, Ben M.; Covington, Ed W., III

2002-01-01

265

Piezoelectric hydraulic pump performance  

NASA Astrophysics Data System (ADS)

A piezohydraulic pump making use of the step and repeat capability of piezoelectric actuators has been developed for actuation of aircraft control surfaces. The piezohydraulic pump utilizes a piezoelectric stack actuator to drive a piston in a cylinder. The cylinder is fitted with two check valves. On the compression stroke, oil is forced out of the cylinder. On the intake stroke, oil is drawn into the cylinder. The oil is used to drive a linear actuator. The actuator was driven at 7cm/sec with a 271N (61lb) blocking force. To achieve this, the piezoelectric stack actuator was driven at 60Hz with a switching power supply. The system utilizes an accumulator to eliminate cavitation. This work discusses piezohydraulic pumping theory, pump design, and pump performance. Consideration of pump performance includes the effects of varying accumulator pressure, hydraulic oil viscosity, and load imposed on the linear actuator.

Mauck, Lisa D.; Oates, William S.; Lynch, Christopher S.

2001-06-01

266

Active piezoelectric diaphragms  

NASA Astrophysics Data System (ADS)

Several active piezoelectric diaphragms were fabricated by placing unelectroded piezoelectric disks between copper clad films patterned with Inter-Circulating Electrodes (ICE). When a voltage potential is applied to the electrodes, the result is radially distributed electric field that mechanically strains the piezo-ceramic along the Z-axis, rather than the expected in-plane direction. Unlike other out of plane piezoelectric actuators, which are benders, these Radial Field Diaphragms strain concentrically yet afford high displacements while maintaining a constant circumference. This paper covers the fabrication and characterization of these diaphragms as a function of poling field strength, ceramic diameter and line spacing, as well as the surface topography, the resulting strain field and displacement as a function of applied voltage ranging from DC to 10 Hz.

Bryant, Robert G.; Effinger, Robert T., IV; Aranda, Isaiah, Jr.; Copeland, Ben M., Jr.; Covington, Ed W., III

2002-07-01

267

Detection of Delaminations in Composite Beams Using Piezoelectric Sensors  

NASA Technical Reports Server (NTRS)

This paper investigates the feasibility of a proposed technique for detecting delamination using piezoelectric layers or patches embedded or bonded to a composite structure. Variations in the voltage generated in the piezoelectric layers indicates the presence and location of delamination, when the structure is excited either externally or via actuators. The theoretical foundations of a method for predicting the dynamic response of delaminated composite beams with piezoelectric layers are described. The governing equations are presented for the case of external vibroacoustic excitation, as well as, for the case of locally induced vibrations by some of the embedded piezoelectric elements. An exact solution is developed within the limits of linear laminate theory. Applications illustrate the feasibility of delamination detection in cantilever beams. The results illustrate that the proposed technique may provide accurate detection of the presence, size, and location of a delamination.

Saravanos, Dimitris A.; Birman, Victor; Hopkins, Dale A.

1994-01-01

268

Gold nanoparticles for photoacoustic imaging.  

PubMed

Photoacoustic (PA) imaging is a biomedical imaging modality that provides functional information regarding the cellular and molecular signatures of tissue by using endogenous and exogenous contrast agents. There has been tremendous effort devoted to the development of PA imaging agents, and gold nanoparticles as exogenous contrast agents have great potential for PA imaging due to their inherent and geometrically induced optical properties. The gold-based nanoparticles that are most commonly employed for PA imaging include spheres, rods, shells, prisms, cages, stars and vesicles. This article provides an overview of the current state of research in utilizing these gold nanomaterials for PA imaging of cancer, atherosclerotic plaques, brain function and image-guided therapy. PMID:25600972

Li, Wanwan; Chen, Xiaoyuan

2015-01-01

269

On the spectral response of thick piezoelectric capacitive sensors for arrays in imagenology applications  

NASA Astrophysics Data System (ADS)

We investigate the spectral response of capacitive sensors with 28 ?m thick Polyvinylidene Fluoride (PVDF) films operating in the piezoelectric mode. We present spectra of signals obtained from laser-induced photoacoustic emissions in several materials. We examine the sensor response to direct laser pulses and to ultrasonic signals generated by laser pulses interacting with polyvinyl alcohol (PVA) phantoms, neoprene slabs and a composite of PVA phantom with a hidden slab of neoprene. We exhibit the sensor's sensitivity to the phantom thickness, affecting the amplitude and bandwidth of the ultrasonic output signal. The sensors fabricated and tested under water achieved an operational frequency bandwidth ranging from 1 to 50 MHz.

Reyes-Ramírez, B.; Garcia-Segundo, C.; García-Valenzuela, A.

2014-03-01

270

Theoretical studies of wave propagation in multilayered piezoelectric media  

SciTech Connect

The purpose of this paper is to extend the analysis of a single plate or substrate to the case of a multilayered medium. Due to the requiring of higher operating frequency, lower attenuation, and stronger piezoelectricity, layered structure becomes necessary. This technique is rapidly applied in the field of nondestructive evaluation and testing (NDE/T). Recently, a new feature of applying the piezoelectric effect for remote sensing, actuating, and vibration controlling came under study and development in aerospace and automative industries.

Chien, Hual-Te; Sheen, Shuh-Haw; Raptis, A.C.

1993-08-01

271

Photoacoustic imaging of brachytherapy seeds using a channel-domain ultrasound array system  

NASA Astrophysics Data System (ADS)

Brachytherapy is a technique commonly used in the treatment of prostate cancer that relies on the precise placement of small radioactive seeds near the tumor location. The advantage of this technique over traditional radiation therapies is that treatment can be continuous and uniform, resulting in fewer clinic visits and a shorter treatment duration. Two important phases of this treatment are needle guidance for implantation, and post-placement verification for dosimetry. Ultrasound is a common imaging modality used for these purposes, but it can be difficult to distinguish the seeds from surrounding tissues, often requiring other imaging techniques such as MRI or CT. Photoacoustic imaging may offer a viable alternative. Using a photoacoustic system based on an L7- 4 array transducer and a realtime ultrasound array system capable of parallel channel data acquisition streamed to a multi-core computer via PCI-express, we have demonstrated imaging of these seeds at an ultrasound depth of 16 mm and laser penetration depths ranging up to 50 mm in chicken tissue with multiple optical wavelengths. Ultrasound and photoacoustic images are coregistered via an interlaced pulse sequence. Two laser pulses are used to form a photoacoustic image, and at these depths, the brachytherapy seeds are detected with a signal-to-noise ratio of over 26dB. To obtain this result, 1064nm light was used with a fluence of 100mJ/cm2, the ANSI limit for human skin exposure at this wavelength. This study demonstrates the potential for photoacoustic imaging as a candidate technology for brachytherapy seed placement guidance and verification.

Harrison, Tyler; Zemp, Roger J.

2011-03-01

272

Using high-power light emitting diodes for photoacoustic imaging  

NASA Astrophysics Data System (ADS)

Photoacoustic imaging will become an important supplement to conventional ultrasound imaging. However, the equipment needed is still too delicate to bring this technique into the daily clinical work. The pulsed light source is the area of interest in the present report. Usually, large and costly laser systems are used to provide high-energy light pulses with a chosen wavelength. Pulsed semiconductor lasers have been demonstrated as a possible alternative light source for the photoacoustic imaging purpose. As an alternative to laser sources, the preliminary result of using a pulsed high-power light emitting diode, LED, for photoacoustic imaging is presented here. The pulsed light source is created from a Luxeon LXHL_PD09 red LED (250mW optical output power at 1 Amp current). The LED is supplied with current pulses 60ns wide and 40A peak. The LED delivers 60ns light pulses with approximately 6W peak power. The phantom used consists of a thin stripe (3mm high x 5mm wide) of green colored gelatin overlaid by a 3cm layer of un-colored gelatin. The light pulses from the LED are collected by a lens system and focused on the green gelatin from beneath the sample. The acoustic response from the green gelatin is detected with a single focused transducer on the upper surface of the 3cm thick colorless gelatin layer. The response is clearly observed when the measurement is taken as an average of 50,000 pulses. Is it concluded that despite the relatively low pulse power, for some purposes, a combination of of LED's could be a candidate for an inexpensive light source.

Skov Hansen, René

2011-03-01

273

Electrostatic and Piezoelectric Testing Methods for RF MEMS Resonators  

Microsoft Academic Search

Two techniques to characterize diamond micromechanical resonator structures are described: (1) electrostatic testing, and (2) piezoelectric actuation with optical detection. It is found that, while the resonant frequency values obtained from the two techniques differ only by 3%, method (2) yield up to eight times larger estimates for the quality factor Q. After describing the techniques and discussing experimental results,

N. Sepulveda; M. Toledo-Quinones

2006-01-01

274

PRODUCT DATA Piezoelectric Accelerometer  

E-print Network

element used is a PZ 23 lead zirconate titanate element. The housing material is titanium. Calibration around a triangular centre post. The ring prestresses the piezoelectric elements to give a high degree Characteristics Dimensions See outline drawing Weight gram (oz.) 17 (0.6) Case Material Titanium Connector 10

Phani, A. Srikantha

275

Piezoelectric actuators control unit  

Microsoft Academic Search

Superconductive cavities for future linear accelerators, such as ILC, have extremely large quality factors that require an effective stabilization with both slow and fast tuners. Piezoelectric actuators are the most common choice for fast tuners, but one drawback for large scale applications is the limited bandwidth and the large cost of commercially available drivers. In this paper we present a

Franco Bedeschi; Stefano Galeotti; Alberto Gennai; Carlo Magazzu; Diego Passuello; Elena Pedreschi; Franco Spinella; Federico Paoletti

2010-01-01

276

Thermophysical investigation of Gafchromic EBT2 films using photoacoustic spectroscopy.  

PubMed

The thermophysical properties of EBT2 films exposed to different doses of x-ray were investigated. The doses ranged from 2 to 818 cGy. The films were irradiated by a Varian linear accelerator using a 6 MV photon beam. The thermal conductivity (k) was obtained by measuring the thermal diffusivity (?) and thermal effusivity (e) using the photoacoustic (PA) technique. The ?, e, and k values clearly indicated their dependence on the dose from 0 to 818 cGy. The results demonstrate that the PA technique can detect variations in the thermal diffusivity at doses as low as approximately 3 cGy. The thermal conductivity for the film exposed to 818 cGy of radiation increased by a factor of approximately 3.70 compared to the non-exposed film. The PA spectroscopic technique displayed good reproducibility, with a relative standard deviation of less than 5%. PMID:24874301

Aydarous, A; Abdallah, S; Al Towairqi, M

2014-07-01

277

Photoacoustic Brain Imaging: from Microscopic to Macroscopic Scales  

PubMed Central

Human brain mapping has become one of the most exciting contemporary research areas, with major breakthroughs expected in the following decades. Modern brain imaging techniques have allowed neuroscientists to gather a wealth of anatomic and functional information about the brain. Among these techniques, by virtue of its rich optical absorption contrast, high spatial and temporal resolutions, and deep penetration, photoacoustic tomography (PAT) has attracted more and more attention, and is playing an increasingly important role in brain studies. In particular, PAT complements other brain imaging modalities by providing high-resolution functional and metabolic imaging. More importantly, PAT’s unique scalability enables scrutinizing the brain at both microscopic and macroscopic scales, using the same imaging contrast. In this Review, we present the state-of-the-art PAT techniques for brain imaging, summarize representative neuroscience applications, outline the technical challenges in translating PAT to human brain imaging, and envision potential technological deliverables. PMID:25401121

Yao, Junjie; Wang, Lihong V.

2014-01-01

278

Photo-acoustic imaging of blue nanoparticle targeted brain tumor for intra-operative glioma delineation  

NASA Astrophysics Data System (ADS)

Distinguishing the tumor from the background neo-plastic tissue is challenging for cancer surgery such as surgical resection of glioma. Attempts have been made to use visible or fluorescent markers to delineate the tumors during surgery. However, the systemic injection of the dyes requires high dose, resulting in negative side effects. A novel method to delineate rat brain tumors intra-operatively, as well as post-operatively, using a highly sensitive photoacoustic imaging technique enhanced by tumor targeting blue nanoparticle as contrast agent is demonstrated. The nanoparticles are made of polyacrylamide (PAA) matrix with covalently linked Coomassie-Blue dye. They contain 7.0% dye and the average size is 80nm. Their surface was conjugated with F3 peptide for active tumor targeting. These nanoparticles are nontoxic, chemically inert and have long plasma circulation lifetime, making them suitable as nanodevices for imaging using photoacoustics. Experiments on phantoms and rat brains tumors ex-vivo demonstrate the high sensitivity of photoacoustic imaging in delineating the tumor, containing contrast agent at concentrations too low to be visualized by eye. The control tumors without nanoparticles did not show any enhanced signal. This study shows that photoacoustic imaging facilitated with the nanoparticle contrast agent could contribute to future surgical procedures for glioma.

Ray, Aniruddha; Wang, Xueding; Koo Lee, Yong-Eun; Hah, HoeJin; Kim, Gwangseong; Chen, Thomas; Orrienger, Daniel; Sagher, Oren; Kopelman, Raoul

2011-07-01

279

Multicontrast photoacoustic in vivo imaging using near-infrared fluorescent proteins  

NASA Astrophysics Data System (ADS)

Non-invasive imaging of biological processes in vivo is invaluable in advancing biology. Photoacoustic tomography is a scalable imaging technique that provides higher resolution at greater depths in tissue than achievable by purely optical methods. Here we report the application of two spectrally distinct near-infrared fluorescent proteins, iRFP670 and iRFP720, engineered from bacterial phytochromes, as photoacoustic contrast agents. iRFPs provide tissue-specific contrast without the need for delivery of any additional substances. Compared to conventional GFP-like red-shifted fluorescent proteins, iRFP670 and iRFP720 demonstrate stronger photoacoustic signals at longer wavelengths, and can be spectrally resolved from each other and hemoglobin. We simultaneously visualized two differently labeled tumors, one with iRFP670 and the other with iRFP720, as well as blood vessels. We acquired images of a mouse as 2D sections of a whole animal, and as localized 3D volumetric images with high contrast and sub-millimeter resolution at depths up to 8 mm. Our results suggest iRFPs are genetically-encoded probes of choice for simultaneous photoacoustic imaging of several tissues or processes in vivo.

Krumholz, Arie; Shcherbakova, Daria M.; Xia, Jun; Wang, Lihong V.; Verkhusha, Vladislav V.

2014-02-01

280

Origin of piezoelectricity in monolayer halogenated graphane piezoelectrics  

NASA Astrophysics Data System (ADS)

Periodic patterning with adatoms or defect is one of the methods for opening the band gap of graphene. In particular, under certain configurations controlled by the order of hydrogen and halogen atoms attached on graphene, inversion symmetry of graphene can be broken to give piezoelectricity as well as pyroelectricity. Using first-principles calculations, we examine the structural stability and electronic properties of four polar conformations of halogenated graphane (C2HX)n to understand the origin of piezoelectricity in this two-dimensional system. The formation energies and piezoelectric coefficients manifest that the four conformations of (C2HF)n are energetically stable with considerable piezoelectricity. We find that the electronic contribution of the proper piezoelectricity in (C2HF)n is mainly related to the change of the electron distribution around F atoms. By substituting flourine with chlorine, we confirm that the piezoelectricity enhances at the expense of stability degradation.

Kim, Hye Jung; Noor-A-Alam, Mohammad; Son, Jong Yeog; Shin, Young-Han

2014-05-01

281

Piezoelectrically actuated time-averaged atomic microtraps  

NASA Astrophysics Data System (ADS)

We present a scheme for creating tight and adiabatic time-averaged atom-traps through the piezoelectric actuation of nanomagnetic structures. We show that potentials formed by the circular translation of magnetic structures have several advantages over conventional rotating-field techniques, particularly for high trap frequencies. As the magnitude of the actuation is changed, the trapping potential can be changed adiabatically between harmonic 3D confinement and a toroidal trap.

West, A. D.; Wade, C. G.; Weatherill, K. J.; Hughes, I. G.

2012-07-01

282

Parallel acoustic delay lines for photoacoustic tomography  

NASA Astrophysics Data System (ADS)

Achieving real-time photoacoustic (PA) tomography typically requires massive ultrasound transducer arrays and data acquisition (DAQ) electronics to receive PA waves simultaneously. In this paper, we report the first demonstration of a photoacoustic tomography (PAT) system using optical fiber-based parallel acoustic delay lines (PADLs). By employing PADLs to introduce specific time delays, the PA signals (on the order of a few micro seconds) can be forced to arrive at the ultrasonic transducers at different times. As a result, time-delayed PA signals in multiple channels can be ultimately received and processed in a serial manner with a single-element transducer, followed by single-channel DAQ electronics. Our results show that an optically absorbing target in an optically scattering medium can be photoacoustically imaged using the newly developed PADL-based PAT system. Potentially, this approach could be adopted to significantly reduce the complexity and cost of ultrasonic array receiver systems.

Yapici, Murat Kaya; Kim, Chulhong; Chang, Cheng-Chung; Jeon, Mansik; Guo, Zijian; Cai, Xin; Zou, Jun; Wang, Lihong V.

2013-03-01

283

Parallel acoustic delay lines for photoacoustic tomography  

NASA Astrophysics Data System (ADS)

Achieving real-time photoacoustic (PA) tomography typically requires multi-element ultrasound transducer arrays and their associated multiple data acquisition (DAQ) electronics to receive PA waves simultaneously. We report the first demonstration of a photoacoustic tomography (PAT) system using optical fiber-based parallel acoustic delay lines (PADLs). By employing PADLs to introduce specific time delays, the PA signals (on the order of a few micro seconds) can be forced to arrive at the ultrasonic transducers at different times. As a result, time-delayed PA signals in multiple channels can be ultimately received and processed in a serial manner with a single-element transducer, followed by single-channel DAQ electronics. Our results show that an optically absorbing target in an optically scattering medium can be photoacoustically imaged using the newly developed PADL-based PAT system. Potentially, this approach could be adopted to significantly reduce the complexity and cost of ultrasonic array receiver systems.

Yapici, Murat Kaya; Kim, Chulhong; Chang, Cheng-Chung; Jeon, Mansik; Guo, Zijian; Cai, Xin; Zou, Jun; Wang, Lihong V.

2012-11-01

284

Photoacoustic imaging of carotid artery atherosclerosis  

NASA Astrophysics Data System (ADS)

We introduce a method for photoacoustic imaging of the carotid artery, tailored toward detection of lipid-rich atherosclerotic lesions. A common human carotid artery was obtained at autopsy, embedded in a neck mimicking phantom and imaged with a multimodality imaging system using interstitial illumination. Light was delivered through a 1.25-mm-diameter optical probe that can be placed in the pharynx, allowing the carotid artery to be illuminated from within the body. Ultrasound imaging and photoacoustic signal detection is achieved by an external 8-MHz linear array coupled to an ultrasound imaging system. Spectroscopic analysis of photoacoustic images obtained in the wavelength range from 1130 to 1250 nm revealed plaque-specific lipid accumulation in the collagen structure of the artery wall. These spectroscopic findings were confirmed by histology.

Kruizinga, Pieter; van der Steen, Antonius F. W.; de Jong, Nico; Springeling, Geert; Robertus, Jan Lukas; van der Lugt, Aad; van Soest, Gijs

2014-11-01

285

A theoretical investigation of photoacoustic contrast agents.  

PubMed

Photoacoustic imaging offers significant potential as a biomedical imaging modality. For some applications, however, there is a need for contrast enhancement. In this paper, a theoretical comparison is presented of the efficacy of three different designs for photoacoustic contrast agents (PACAs), specifically, a droplet of dye, a bubble filled with gas coated by a dye loaded shell, and a droplet of volatile dye. For each case, the governing equations describing the dynamics of a single PACA in a homogenous incompressible fluid are derived. The coupled sets of equations describing the bubble oscillation and resulting radiated pressure, the photo-acoustic energy equation, and the equation of state are then solved numerically. The numerical results predict a stronger radiated acoustic signal for the same optical source energy density in the case of the volatile dye droplet by a factor of up to two orders of magnitude compared with the other two types of agent. PMID:23742340

Firouzi, K; Stride, E; Saffari, N

2013-06-01

286

Ultrasonically encoded photoacoustic flowgraphy in biological tissue.  

PubMed

Blood flow speed is an important functional parameter. Doppler ultrasound flowmetry lacks sufficient sensitivity to slow blood flow (several to tens of millimeters per second) in deep tissue. To address this challenge, we developed ultrasonically encoded photoacoustic flowgraphy combining ultrasonic thermal tagging with photoacoustic imaging. Focused ultrasound generates a confined heat source in acoustically absorptive fluid. Thermal waves propagate with the flow and are directly visualized in pseudo color using photoacoustic computed tomography. The Doppler shift is employed to calculate the flow speed. This method requires only acoustic and optical absorption, and thus is applicable to continuous fluid. A blood flow speed as low as 0.24??mm·s(-1)} was successfully measured. Deep blood flow imaging was experimentally demonstrated under 5-mm-thick chicken breast tissue. PMID:24289689

Wang, Lidai; Xia, Jun; Yao, Junjie; Maslov, Konstantin I; Wang, Lihong V

2013-11-15

287

Ultrasonically encoded photoacoustic flowgraphy in biological tissue  

PubMed Central

Blood flow speed is an important functional parameter. Doppler ultrasound flowmetry lacks sufficient sensitivity to slow blood flow (several to tens of millimeters per second) in deep tissue. To address this challenge, we developed ultrasonically encoded photoacoustic flowgraphy combining ultrasonic thermal tagging with photoacoustic imaging. Focused ultrasound generates a confined heat source in acoustically absorptive fluid. Thermal waves propagate with the flow and are directly visualized in pseudo color using photoacoustic computed tomography. The Doppler shift is employed to calculate the flow speed. This method requires only acoustic and optical absorption, and thus is applicable to continuous fluid. A blood flow speed as low as 0.24 mm·s?1 was successfully measured. Deep blood flow imaging was experimentally demonstrated under 5-mm-thick chicken breast tissue. PMID:24289689

Wang, Lidai; Xia, Jun; Yao, Junjie; Maslov, Konstantin I.; Wang, Lihong V.

2014-01-01

288

Systematic study of high-frequency ultrasonic transducer design for laser-scanning photoacoustic ophthalmoscopy  

PubMed Central

Abstract. Photoacoustic ophthalmoscopy (PAOM) is a high-resolution in vivo imaging modality that is capable of providing specific optical absorption information for the retina. A high-frequency ultrasonic transducer is one of the key components in PAOM, which is in contact with the eyelid through coupling gel during imaging. The ultrasonic transducer plays a crucial role in determining the image quality affected by parameters such as spatial resolution, signal-to-noise ratio, and field of view. In this paper, we present the results of a systematic study on a high-frequency ultrasonic transducer design for PAOM. The design includes piezoelectric material selection, frequency selection, and the fabrication process. Transducers of various designs were successfully applied for capturing images of biological samples in vivo. The performances of these designs are compared and evaluated. PMID:24441942

Ma, Teng; Zhang, Xiangyang; Chiu, Chi Tat; Chen, Ruimin; Kirk Shung, K.; Zhou, Qifa; Jiao, Shuliang

2014-01-01

289

Deblurring algorithms accounting for the finite detector size in photoacoustic tomography.  

PubMed

Most reconstruction algorithms for photoacoustic tomography, like back projection or time reversal, work ideally for point-like detectors. For real detectors, which integrate the pressure over their finite size, images reconstructed by these algorithms show some blurring. Iterative reconstruction algorithms using an imaging matrix can take the finite size of real detectors directly into account, but the numerical effort is significantly higher compared to the use of direct algorithms. For spherical or cylindrical detection surfaces, the blurring caused by a finite detector size is proportional to the distance from the rotation center (spin blur) and is equal to the detector size at the detection surface. In this work, we apply deconvolution algorithms to reduce this type of blurring on simulated and on experimental data. Two particular deconvolution methods are compared, which both utilize the fact that a representation of the blurred image in polar coordinates decouples pixels at different radii from the rotation center. Experimental data have been obtained with a flat, rectangular piezoelectric detector measuring signals around a plastisol cylinder containing various small photoacoustic sources with variable distance from the center. Both simulated and experimental results demonstrate a nearly complete elimination of spin blur. PMID:24853146

Roitner, Heinz; Haltmeier, Markus; Nuster, Robert; O'Leary, Dianne P; Berer, Thomas; Paltauf, Guenther; Grün, Hubert; Burgholzer, Peter

2014-05-01

290

Remote photoacoustic imaging for material inspection  

NASA Astrophysics Data System (ADS)

We report on (to our knowledge) the first remote contactless photoacoustic imaging with short excitation pulses on semitransparent solid polymer samples for material inspection. In this work solid semitransparent samples are excited with pulses from a short pulse laser. The local absorption of the electromagnetic radiation leads to generation of broadband ultrasonic waves. Ultrasonic waves arriving on the sample surface are detected with a confocal Fabry-Pérot interferometer. After data acquisition the absorbed energy density is reconstructed by utilizing an F-SAFT algorithm. The work shows the potential of photoacoustic imaging on material inspection of semitransparent solid materials.

Berer, T.; Hochreiner, A.; Reitinger, B.; Grün, H.; Burgholzer, P.

2011-01-01

291

Photoacoustic imaging of microvascular structure in tissue  

NASA Astrophysics Data System (ADS)

Our goal is the development of a photo-acoustic instrument for 3D imaging of the microvascular structure in tissue, in real time. A photo-acoustic multi-element detector has been designed, which measures in reflection mode. The light source is a pulsed laser with a wavelength of 532nm and the active piezo-material is PVdF. Using a disk detector we have achieved to reconstruction 3D images with a depth and lateral resolution of 10-20 micrometers and 200 micrometers respectively. With the new probe we expect to reduce the measuring time and to sped up the signal and image processing.

Pilatou, Magdalena C.; Kolkman, Roy G. M.; Hondebrink, Erwin; Berendsen, Ralph; de Mul, Frits F. M.

2000-05-01

292

Photoacoustic effect in a sinusoidally modulated structure  

NASA Astrophysics Data System (ADS)

We derive solutions to an inhomogeneous Mathieu equation that describes the photoacoustic effect in a one-dimensional phononic structure whose acoustic properties vary sinusoidally in space. Solutions show splitting of resonances, the space equivalent of subharmonic generation, and spatial confinement. Properties of the photoacoustic effect including the damping of waves inside the band gaps, the dispersion relation, the positions and widths of the gaps, the frequencies of resonances, and the space dependence of the acoustic waves can be found in closed form from known properties of Mathieu functions.

Wu, Binbin; Diebold, Gerald J.

2012-04-01

293

Photoacoustic imaging based on MEMS mirror scanning  

PubMed Central

A microelectromechanical systems (MEMS)-based photoacoustic imaging system is reported for the first time. In this system, the MEMS-based light scanning subsystem and a ring-shaped polyvinylidene fluoride (PVDF) transducer are integrated into a miniaturized probe that is capable of three-dimensional (3D) photoacoustic imaging. It is demonstrated that the imaging system is able to image small objects embedded in phantom materials and in chicken and to in vivo visualize blood vessels under the skin of a human hand. PMID:21258548

Xi, Lei; Sun, Jingjing; Zhu, Yiping; Wu, Lei; Xie, Huikai; Jiang, Huabei

2010-01-01

294

In vivo virtual intraoperative surgical photoacoustic microscopy  

SciTech Connect

We developed a virtual intraoperative surgical photoacoustic microscopy system by combining with a commercial surgical microscope and photoacoustic microscope (PAM). By sharing the common optical path in the microscope and PAM system, we could acquire the PAM and microscope images simultaneously. Moreover, by employing a beam projector to back-project 2D PAM images onto the microscope view plane as augmented reality, the conventional microscopic and 2D cross-sectional PAM images are concurrently mapped on the plane via an ocular lens of the microscope in real-time. Further, we guided needle insertion into phantom ex vivo and mice skins in vivo.

Han, Seunghoon, E-mail: hsh860504@gmail.com; Kim, Sehui, E-mail: sehui0916@nate.com; Kim, Jeehyun, E-mail: jeehk@knu.ac.kr, E-mail: chulhong@postech.edu [School of Electrical Engineering and Computer Science, Kyungpook National University, Daegu 702-701 (Korea, Republic of)] [School of Electrical Engineering and Computer Science, Kyungpook National University, Daegu 702-701 (Korea, Republic of); Lee, Changho, E-mail: ch31037@postech.edu; Jeon, Mansik, E-mail: msjeon@postech.edu [Department of Creative IT Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of)] [Department of Creative IT Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of); Kim, Chulhong, E-mail: jeehk@knu.ac.kr, E-mail: chulhong@postech.edu [Department of Creative IT Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of) [Department of Creative IT Engineering, Pohang University of Science and Technology (POSTECH), Pohang 790-784 (Korea, Republic of); Department of Biomedical Engineering, The State University of New York at Buffalo, Buffalo, New York 14221 (United States)

2013-11-11

295

In vivo virtual intraoperative surgical photoacoustic microscopy  

PubMed Central

We developed a virtual intraoperative surgical photoacoustic microscopy system by combining with a commercial surgical microscope and photoacoustic microscope (PAM). By sharing the common optical path in the microscope and PAM system, we could acquire the PAM and microscope images simultaneously. Moreover, by employing a beam projector to back-project 2D PAM images onto the microscope view plane as augmented reality, the conventional microscopic and 2D cross-sectional PAM images are concurrently mapped on the plane via an ocular lens of the microscope in real-time. Further, we guided needle insertion into phantom ex vivo and mice skins in vivo. PMID:24343135

Han, Seunghoon; Lee, Changho; Kim, Sehui; Jeon, Mansik; Kim, Jeehyun; Kim, Chulhong

2013-01-01

296

Source-receiver photoacoustic wave interferometry  

NASA Astrophysics Data System (ADS)

The representation theorems of the convolution type and the correlation type are used to obtain the superposition of the Green's function and its time reversal counterpart for the photoacoustic wave equation. Based on the representation theorems, an interferometry relation providing the Green's function between sources and receivers is obtained. The reciprocity theorems for a spherical geometrical system consisting of sources located on the boundary of the inner spherical region and transducers located on the outer boundary are utilized. Therefore, the measurement would be observed at one of the detectors if there were a photoacoustic point source at the other one.

Erkol, Hakan; Demirkiran, Aytac; Aytac-Kipergil, Esra; Uluc, Nasire; Unlu, Mehmet B.

2014-03-01

297

Mapping tissue oxygen in vivo by photoacoustic lifetime imaging  

NASA Astrophysics Data System (ADS)

Oxygen plays a key role in the energy metabolism of living organisms. Any imbalance in the oxygen levels will affect the metabolic homeostasis and lead to pathophysiological diseases. Hypoxia, a status of low tissue oxygen, is a key factor in tumor biology as it is highly prominent in tumor tissues. However, clinical tools for assessing tissue oxygenation are limited. The gold standard is polarographic needle electrode which is invasive and not capable of mapping (imaging) the oxygen content in tissue. We applied the method of photoacoustic lifetime imaging (PALI) of oxygen-sensitive dye to small animal tissue hypoxia research. PALI is new technology for direct, non-invasive imaging of oxygen. The technique is based on mapping the oxygen-dependent transient optical absorption of Methylene Blue (MB) by pump-probe photoacoustic imaging. Our studies show the feasibility of imaging of dissolved oxygen distribution in phantoms. In vivo experiments demonstrate that the hypoxia region is consistent with the site of subcutaneously xenografted prostate tumor in mice with adequate spatial resolution and penetration depth.

Shao, Qi; Morgounova, Ekaterina; Choi, Jeung-Hwan; Jiang, Chunlan; Bischof, John; Ashkenazi, Shai

2013-03-01

298

Combined optical resolution photoacoustic and fluorescence micro-endoscopy  

NASA Astrophysics Data System (ADS)

We present a new micro-endoscopy system combining real-time C-scan optical-resolution photoacoustic micro-endoscopy (OR-PAME), and a high-resolution fluorescence micro-endoscopy system for visualizing fluorescently labeled cellular components and optically absorbing microvasculature simultaneously. With a diode-pumped 532-nm fiber laser, the OR-PAM sub-system is capable of imaging with a resolution of ~ 7?m. The fluorescence sub-system consists of a diode laser with 445 nm-centered emissions as the light source, an objective lens and a CCD camera. Proflavine, a FDA approved drug for human use, is used as the fluorescent contrast agent by topical application. The fluorescence system does not require any mechanical scanning. The scanning laser and the diode laser light source share the same light path within an optical fiber bundle containing 30,000 individual single mode fibers. The absorption of Proflavine at 532 nm is low, which mitigates absorption bleaching of the contrast agent by the photoacoustic excitation source. We demonstrate imaging in live murine models. The system is able to provide cellular morphology with cellular resolution co-registered with the structural and functional information given by OR-PAM. Therefore, the system has the potential to serve as a virtual biopsy technique, helping researchers and clinicians visualize angiogenesis, effects of anti-cancer drugs on both cells and the microcirculation, as well as aid in the study of other diseases.

Shao, Peng; Shi, Wei; Hajireza, Parsin; Zemp, Roger J.

2012-02-01

299

Piezoelectric Resonator with Two Layers  

NASA Technical Reports Server (NTRS)

A piezoelectric resonator device includes: a top electrode layer with a patterned structure, a top piezoelectric layer adjacent to the top layer, a middle metal layer adjacent to the top piezoelectric layer opposite the top layer, a bottom piezoelectric layer adjacent to the middle layer opposite the top piezoelectric layer, and a bottom electrode layer with a patterned structure and adjacent to the bottom piezoelectric layer opposite the middle layer. The top layer includes a first plurality of electrodes inter-digitated with a second plurality of electrodes. A first one of the electrodes in the top layer and a first one of the electrodes in the bottom layer are coupled to a first contact, and a second one of the electrodes in the top layer and a second one of the electrodes in the bottom layer are coupled to a second contact.

Stephanou, Philip J. (Inventor); Black, Justin P. (Inventor)

2013-01-01

300

Piezoelectric step-motion actuator  

DOEpatents

A step-motion actuator using piezoelectric material to launch a flight mass which, in turn, actuates a drive pawl to progressively engage and drive a toothed wheel or rod to accomplish stepped motion. Thus, the piezoelectric material converts electrical energy into kinetic energy of the mass, and the drive pawl and toothed wheel or rod convert the kinetic energy of the mass into the desired rotary or linear stepped motion. A compression frame may be secured about the piezoelectric element and adapted to pre-compress the piezoelectric material so as to reduce tensile loads thereon. A return spring may be used to return the mass to its resting position against the compression frame or piezoelectric material following launch. Alternative embodiment are possible, including an alternative first embodiment wherein two masses are launched in substantially different directions, and an alternative second embodiment wherein the mass is eliminated in favor of the piezoelectric material launching itself.

Mentesana; Charles P. (Leawood, KS)

2006-10-10

301

Finite Element Simulation of Photoacoustic Pressure in a Resonant Photoacoustic Cell Using Lossy Boundary Conditions  

Microsoft Academic Search

The finite-element method (FEM) is used to simulate the photoacoustic signal in a cylindrical resonant photoacoustic cell.\\u000a Simulations include loss effects near the cell walls that appear in the boundary conditions for the inhomogeneous Helmholtz\\u000a equation governing the acoustic pressure. Reasonably good agreement is obtained between theoretical results and experimental\\u000a data. However, it was anticipated that loss mechanisms other than

L. Duggen; N. Lopes; M. Willatzen; H.-G. Rubahn

2011-01-01

302

Improved Piezoelectric Loudspeakers And Transducers  

NASA Technical Reports Server (NTRS)

Loudspeakers and related acoustic transducers of improved type feature both light weight and energy efficiency of piezoelectric transducers and mechanical coupling efficiency. Active component of transducer made from wafer of "rainbow" piezoelectric material, ceramic piezoelectric material chemically reduced on one face. Chemical treatment forms wafer into dishlike shallow section of sphere. Both faces then coated with electrically conductive surface layers serving as electrodes. Applications include high-fidelity loudspeakers, and underwater echo ranging devices.

Regan, Curtis Randall; Jalink, Antony; Hellbaum, Richard F.; Rohrbach, Wayne W.

1995-01-01

303

Photoacoustic microscopy of human teeth  

NASA Astrophysics Data System (ADS)

Photoacoustic microscopy (PAM) utilizes short laser pulses to deposit energy into light absorbers and sensitively detects the ultrasonic waves the absorbers generate in response. PAM directly renders a three-dimensional spatial distribution of sub-surface optical absorbers. Unlike other optical imaging technologies, PAM features label-free optical absorption contrast and excellent imaging depths. Standard dental imaging instruments are limited to X-ray and CCD cameras. Subsurface optical dental imaging is difficult due to the highly-scattering enamel and dentin tissue. Thus, very few imaging methods can detect dental decay or diagnose dental pulp, which is the innermost part of the tooth, containing the nerves, blood vessels, and other cells. Here, we conducted a feasibility study on imaging dental decay and dental pulp with PAM. Our results showed that PAM is sensitive to the color change associated with dental decay. Although the relative PA signal distribution may be affected by surface contours and subsurface reflections from deeper dental tissue, monitoring changes in the PA signals (at the same site) over time is necessary to identify the progress of dental decay. Our results also showed that deep-imaging, near-infrared (NIR) PAM can sensitively image blood in the dental pulp of an in vitro tooth. In conclusion, PAM is a promising tool for imaging both dental decay and dental pulp.

Rao, Bin; Cai, Xin; Favazza, Christopher; Yao, Junjie; Li, Li; Duong, Steven; Liaw, Lih-Huei; Holtzman, Jennifer; Wilder-Smith, Petra; Wang, Lihong V.

2011-03-01

304

[Evaluation of nutrient release profiles from polymer coated fertilizers using Fourier transform mid-infrared photoacoustic spectroscopy].  

PubMed

The acrylate-like materials were used to develop the polymer coated controlled release fertilizer, the nutrients release profiles were determined, meanwhile the Fourier transform mid-infrared photoacoustic spectra of the coatings were recorded and characterized; GRNN model was used to predict the nutrients release profiles using the principal components of the mid-infrared photoacoustic spectra as input. Results showed that the GRNN model could fast and effectively predict the nutrient release profiles, and the predicted calibration coefficients were more than 0.93; on the whole, the prediction errors (RMSE) were influenced by the profiling depth of the spectra, the average prediction error was 10.28%, and the spectra from the surface depth resulted in a lowest prediction error with 7.14%. Therefore, coupled with GRNN modeling, Fourier transform mid-infrared photoacoustic spectroscopy can be used as an alternative new technique in the fast and accurate prediction of nutrient release from polymer coated fertilizer. PMID:22512162

Shen, Ya-zhen; Du, Chang-wen; Zhou, Jian-min; Wang, Huo-yan; Chen, Xiao-qin

2012-02-01

305

Photoacoustic Doppler measurement of flow using tone burst excitation.  

PubMed

In this paper a novel technique for flow measurement which is based on the photoacoustic (PA) Doppler effect is described. A significant feature of the proposed approach is that it can be implemented using tone burst optical excitation thus enabling simultaneous measurement of both velocity and position. The technique, which is based on external modulation and heterodyne detection, was experimentally demonstrated by measurement of the flow of a suspension of carbon particles in a silicon tube and successfully determined the particles mean velocity up to values of 130 mm/sec, which is about 10 times higher than previously reported PA Doppler set-ups. In the theoretical part a rigorous derivation of the PA response of a flowing medium is described and some important simplifying approximations are highlighted. PMID:20389434

Sheinfeld, Adi; Gilead, Sharon; Eyal, Avishay

2010-03-01

306

High Temperature Piezoelectric Drill  

NASA Technical Reports Server (NTRS)

Venus is one of the planets in the solar systems that are considered for potential future exploration missions. It has extreme environment where the average temperature is 460 deg C and its ambient pressure is about 90 atm. Since the existing actuation technology cannot maintain functionality under the harsh conditions of Venus, it is a challenge to perform sampling and other tasks that require the use of moving parts. Specifically, the currently available electromagnetic actuators are limited in their ability to produce sufficiently high stroke, torque, or force. In contrast, advances in developing electro-mechanical materials (such as piezoelectric and electrostrictive) have enabled potential actuation capabilities that can be used to support such missions. Taking advantage of these materials, we developed a piezoelectric actuated drill that operates at the temperature range up to 500 deg C and the mechanism is based on the Ultrasonic/Sonic Drill/Corer (USDC) configuration. The detailed results of our study are presented in this paper

Bao, Xiaoqi; Bar-Cohen, Yoseph; Sherrit, Stewart; Badescu, Mircea; Shrout, Tom

2012-01-01

307

High temperature piezoelectric drill  

NASA Astrophysics Data System (ADS)

Venus is one of the planets in the solar systems that are considered for potential future exploration missions. It has extreme environment where the average temperature is 460°C and its ambient pressure is about 90 atm. Since the existing actuation technology cannot maintain functionality under the harsh conditions of Venus, it is a challenge to perform sampling and other tasks that require the use of moving parts. Specifically, the currently available electromagnetic actuators are limited in their ability to produce sufficiently high stroke, torque, or force. In contrast, advances in developing electro-mechanical materials (such as piezoelectric and electrostrictive) have enabled potential actuation capabilities that can be used to support such missions. Taking advantage of these materials, we developed a piezoelectric actuated drill that operates at the temperature range up to 500°C and the mechanism is based on the Ultrasonic/Sonic Drill/Corer (USDC) configuration. The detailed results of our study are presented in this paper.

Bao, Xiaoqi; Bar-Cohen, Yoseph; Sherrit, Stewart; Badescu, Mircea; Shrout, Tom

2012-04-01

308

Photo-acoustic excitation and detection of guided ultrasonic waves in bone samples covered by a soft coating layer  

NASA Astrophysics Data System (ADS)

Photo-acoustic (PA) excitation was combined with skeletal quantitative ultrasound (QUS) for multi-mode ultrasonic assessment of human long bones. This approach permits tailoring of the ultrasonic excitation and detection so as to efficiently detect the fundamental flexural guided wave (FFGW) through a coating of soft tissue. FFGW is a clinically relevant indicator of cortical thickness. An OPO laser with tunable optical wavelength, was used to excite a photo-acoustic source in the shaft of a porcine femur. Ultrasonic signals were detected by a piezoelectric transducer, scanning along the long axis of the bone, 20-50 mm away from the source. Five femurs were measured without and with a soft coating. The coating was made of an aqueous gelatin-intralipid suspension that optically and acoustically mimicked real soft tissue. An even coating thickness was ensured by using a specific mold. The optical wave length of the source (1250 nm) was tuned to maximize the amplitude of FFGW excitation at 50 kHz frequency. The experimentally determined FFGW phase velocity in the uncoated samples was consistent with that of the fundamental antisymmetric Lamb mode (A0). Using appropriate signal processing, FFGW was also identified in the coated bone samples, this time with a phase velocity consistent with that theoretically predicted for the first mode of a fluid-solid bilayer waveguide (BL1). Our results suggest that photo-acoustic quantitative ultrasound enables assessment of the thickness-sensitive FFGW in bone through a layer of soft tissue. Photo-acoustic characterization of the cortical bone thickness may thus become possible.

Zhao, Zuomin; Moilanen, Petro; Karppinen, Pasi; Määttä, Mikko; Karppinen, Timo; Hæggström, Edward; Timonen, Jussi; Myllylä, Risto

2012-12-01

309

Hybrid piezoelectric energy harvesting transducer system  

NASA Technical Reports Server (NTRS)

A hybrid piezoelectric energy harvesting transducer system includes: (a) first and second symmetric, pre-curved piezoelectric elements mounted separately on a frame so that their concave major surfaces are positioned opposite to each other; and (b) a linear piezoelectric element mounted separately on the frame and positioned between the pre-curved piezoelectric elements. The pre-curved piezoelectric elements and the linear piezoelectric element are spaced from one another and communicate with energy harvesting circuitry having contact points on the frame. The hybrid piezoelectric energy harvesting transducer system has a higher electromechanical energy conversion efficiency than any known piezoelectric transducer.

Xu, Tian-Bing (Inventor); Jiang, Xiaoning (Inventor); Su, Ji (Inventor); Rehrig, Paul W. (Inventor); Hackenberger, Wesley S. (Inventor)

2008-01-01

310

PIEZOELECTRIC POWER SCAVENGING OF MECHANICAL VIBRATION ENERGY  

E-print Network

PIEZOELECTRIC POWER SCAVENGING OF MECHANICAL VIBRATION ENERGY PIEZOELECTRIC POWER SCAVENGING OFPIEZOELECTRIC POWER SCAVENGING OF MECHANICAL VIBRATION ENERGYMECHANICAL VIBRATION ENERGY CE 511- Structural

Ervin, Elizabeth K.

311

Piezoelectrically enhanced photocathode  

NASA Technical Reports Server (NTRS)

A photocathode, for generating electrons in response to incident photons in a photodetector, includes a base layer having a first lattice structure and an active layer having a second lattice structure and epitaxially formed on the base layer, the first and second lattice structures being sufficiently different to create a strain in the active layer with a corresponding piezoelectrically induced polarization field in the active layer, the active layer having a band gap energy corresponding to a desired photon energy.

Beach, Robert A. (Inventor); Nikzad, Shouleh (Inventor); Strittmatter, Robert P. (Inventor); Bell, Lloyd Douglas (Inventor)

2009-01-01

312

Modeling piezoelectric actuators  

Microsoft Academic Search

The piezoelectric actuator (PEA) is a well-known device for managing extremely small displacements in the range from 10 pm to 100 ?m. When developing a control system for a piezo-actuated positioning mechanism, the actuator dynamics have to be taken into account. An electromechanical piezo model, based on physical principles, is presented in this paper. In this model, a first-order differential

H. J. M. T. S. Adriaens; W. L. De Koning; R. Banning

2000-01-01

313

Multimaterial piezoelectric fibres  

NASA Astrophysics Data System (ADS)

Fibre materials span a broad range of applications ranging from simple textile yarns to complex modern fibre-optic communication systems. Throughout their history, a key premise has remained essentially unchanged: fibres are static devices, incapable of controllably changing their properties over a wide range of frequencies. A number of approaches to realizing time-dependent variations in fibres have emerged, including refractive index modulation, nonlinear optical mechanisms in silica glass fibres and electroactively modulated polymer fibres. These approaches have been limited primarily because of the inert nature of traditional glassy fibre materials. Here we report the composition of a phase internal to a composite fibre structure that is simultaneously crystalline and non-centrosymmetric. A ferroelectric polymer layer of 30?m thickness is spatially confined and electrically contacted by internal viscous electrodes and encapsulated in an insulating polymer cladding hundreds of micrometres in diameter. The structure is thermally drawn in its entirety from a macroscopic preform, yielding tens of metres of piezoelectric fibre. The fibres show a piezoelectric response and acoustic transduction from kilohertz to megahertz frequencies. A single-fibre electrically driven device containing a high-quality-factor Fabry-Perot optical resonator and a piezoelectric transducer is fabricated and measured.

Egusa, S.; Wang, Z.; Chocat, N.; Ruff, Z. M.; Stolyarov, A. M.; Shemuly, D.; Sorin, F.; Rakich, P. T.; Joannopoulos, J. D.; Fink, Y.

2010-08-01

314

Photoacoustic FTIR spectroscopic study of undisturbed human cortical bone  

NASA Astrophysics Data System (ADS)

Chemical pretreatment has been the prevailing sample preparation procedure for infrared (IR) spectroscopic studies on bone. However, experiments have indicated that chemical pretreatment can potentially affect the interactions between the components. Typically the IR techniques have involved transmission experiments. Here we report experimental studies using photoacoustic Fourier transform infrared spectroscopy (PA-FTIR). As a nondestructive technique, PA-FTIR can detect absorbance spectrum from a sample at controllable sampling depth and with little or no sample preparation. Additionally, the coupling inert gas, helium, which is utilized in the PA-FTIR system, can inhibit bacteria growth of bone by displacing oxygen. Therefore, we used this technique to study the undisturbed human cortical bone. It is found that photoacoustic mode (linear-scan, LS-PA-FTIR) can obtain basically similar spectra of bone as compared to the traditional transmission mode, but it seems more sensitive to amide III and ?2 carbonate bands. The ?3 phosphate band is indicative of detailed mineral structure and symmetry of native bone. The PA-FTIR depth profiling experiments on human cortical bone also indicate the influence of water on OH band and the cutting effects on amide I and mineral bands. Our results indicate that phosphate ion geometry appears less symmetric in its undisturbed state as detected by the PA-FTIR as compared to higher symmetry observed using transmission techniques on disturbed samples. Moreover, the PA-FTIR spectra indicate a band at 1747 cm-1 possibly resulting from Cdbnd O stretching of lipids, cholesterol esters, and triglycerides from the arteries. Comparison of the spectra in transverse and longitudinal cross-sections demonstrates that, the surface area of the longitudinal section bone appears to have more organic matrix exposed and with higher mineral stoichiometry.

Gu, Chunju; Katti, Dinesh R.; Katti, Kalpana S.

2013-02-01

315

Thermal Images of Small Agricultural Seeds Obtained by Photoacoustic and Photopyroelectric Microscopies  

NASA Astrophysics Data System (ADS)

Photoacoustic (PA) and photopyroelectric microscopies were used to obtain photothermal images of small agricultural seeds. In the photoacoustic microscopy (PAM) technique, a tightly closed PA cell was used with an electret microphone as the sensor. In photopyroelectric microscopy (PPEM), the seeds were placed in contact with a pyroelectric (PE) sensor. From the experimental data, it was possible to obtain thermal images of the scanned samples from the amplitude and phase signals. In the present research, thermal images of small agricultural seeds were obtained by both techniques and compared. The experimental results show that the photothermal images obtained by PAM have better resolution than those obtained by PPEM. PAM images using the amplitude signal appear to be more sensitive to detect seed structures as was observed in the seed thermal images obtained in this study.

Domínguez Pacheco, A.; Hernández Aguilar, C.; Cruz-Orea, A.

2013-05-01

316

Photoacoustic tomography imaging based on a 4f acoustic lens imaging system.  

PubMed

The theory of photoacoustic tomography (PAT) imaging using a 4f acoustic lens imaging system has been investigated, and the theoretical results show that a 4f acoustic lens has the ability of imaging and guarantees axial and lateral unit magnification of image. A system, a 4f acoustic lens imaging system combining with time-resolved technique, is developed to acquire PAT images. The 4f acoustic lens is able to image initial photoacoustic (PA) pressure distribution, which exactly resembles the absorption distribution, onto an imaging plane. Combining with time-resolved technique, the linear transducer array is adopted to acquire the PA pressure distribution to reconstruct the PAT images. Experimental results demonstrate that the system is able to obtain PAT images and the images contrast sharply with their backgrounds. PMID:19532746

Chen, Zhanxu; Tang, Zhilie; Wan, Wei

2007-04-16

317

Development of microvalves for gas flow control in micronozzles using PVDF piezoelectric polymer  

Microsoft Academic Search

This work describes a fabrication and test sequence of microvalves installed on micronozzles. The technique used to fabricate the micronozzles was powder blasting. The microvalves are actuators made from PVDF (polivinylidene fluoride), that is a piezoelectric polymer. The micronozzles have convergent-divergent shape with external diameter of 1mm and throat around 230mum. The polymer have low piezoelectric coefficient, for this reason

R. S. Wiederkehr; M. C. Salvadori; F. T. Degasperi; M. Cattani

2008-01-01

318

Development of microvalves for gas flow control in micronozzles using PVDF piezoelectric polymer  

Microsoft Academic Search

This work describes a fabrication and test sequence of microvalves installed on micronozzles. The technique used to fabricate the micronozzles was powder blasting. The microvalves are actuators made from PVDF (polivinylidene fluoride), that is a piezoelectric polymer. The micronozzles have convergent-divergent shape with external diameter of 1mm and throat around 230?m. The polymer have low piezoelectric coefficient, for this reason

R S Wiederkehr; M C Salvadori; F T Degasperi; M Cattani

2008-01-01

319

Piezoelectric actuation of crack growth along polymer-metal interfaces in adhesive bonds  

Microsoft Academic Search

A new experimental technique for determining mechanical properties of polymer-metal interfaces was developed by replacing the conventional mechanical testing machine with a piezoelectric actuator. The actuator was made from a thin ferroelectric ceramic beam attached to a bilayer polymer-metal composite specimen. The trilayer specimen was loaded by applying ac electric fields on the piezoelectric actuator to drive crack growth along

Tianbao Du; Ming Liu; Steve Seghi; K. J. Hsia; J. Economy; J. K. Shang

2001-01-01

320

Energy Harvesting Using PVDF Piezoelectric Nanofabric  

NASA Astrophysics Data System (ADS)

Energy harvesting using piezoelectric nanomaterial provides an opportunity for advancement towards self-powered electronics. The fabrication complexities and limited power output of these nano/micro generators have hindered these advancements thus far. This thesis presents a fabrication technique with electrospinning using a grounded cylinder as the collector. This method addresses the difficulties with the production and scalability of the nanogenerators. The non-aligned nanofibers are woven into a textile form onto the cylindrical drum that can be easily removed. The electrical poling and mechanical stretching induced by the electric field and the drum rotation increase the concentration of the piezoelectric beta phase in the PVDF nanofabric. The nanofabric is placed between two layers of polyethylene terephthalate (PET) that have interdigitated electrodes painted on them with silver paint. Applying continuous load onto the flexible PVDF nanofabric at 35Hz produces a peak voltage of 320 mV and maximum power of 2200 pW/(cm2) .

Shafii, Chakameh Shafii

321

Remote photoacoustic imaging for material inspection  

Microsoft Academic Search

We report on (to our knowledge) the first remote contactless photoacoustic imaging with short excitation pulses on semitransparent solid polymer samples for material inspection. In this work solid semitransparent samples are excited with pulses from a short pulse laser. The local absorption of the electromagnetic radiation leads to generation of broadband ultrasonic waves. Ultrasonic waves arriving on the sample surface

T. Berer; A. Hochreiner; B. Reitinger; H. Grün; P. Burgholzer

2011-01-01

322

Inverse Transport Theory of Photoacoustics Guillaume Bal  

E-print Network

of acoustic (ultrasonic) waves. Electromagnetic radiation, sent through a domain of interest, generates some data. Photoacoustic tomography (PAT) radiates high frequency electromagnetic waves into the domain of the tissues generates acoustic waves, which then propagate through the medium and are recorded by an array

Bal, Guillaume

323

Diode Pumped Solid State Laser Photoacoustic Spectrometer  

E-print Network

Diode Pumped Solid State Laser Photoacoustic Spectrometer Jeffrey S. Pilgrim and David S. Bomse study is based on Tm3+ :YAG [3]. Other solid state lasers are available as shown in Fig. 1, which hampered by the absence of a simple tunable infrared source with moderate power. Diode pumped solid state

324

Diode Pumped Solid State Laser Photoacoustic Spectrometer  

E-print Network

Abstract: Photoacoustic spectroscopy (PAS) is well-known for trace gas detection but has been hampered by the lack of a simple tunable infrared source. DPSS lasers offer this capability and enable a PAS sensor with superior performance. ©2000 Optical Society of America

Jeffrey S. Pilgrim; David S. Bomse

325

Improving photoacoustic imaging contrast of brachytherapy seeds  

NASA Astrophysics Data System (ADS)

Prostate brachytherapy is a form of radiotherapy for treating prostate cancer where the radiation sources are seeds inserted into the prostate. Accurate localization of seeds during prostate brachytherapy is essential to the success of intraoperative treatment planning. The current standard modality used in intraoperative seeds localization is transrectal ultrasound. Transrectal ultrasound, however, suffers in image quality due to several factors such speckle, shadowing, and off-axis seed orientation. Photoacoustic imaging, based on the photoacoustic phenomenon, is an emerging imaging modality. The contrast generating mechanism in photoacoustic imaging is optical absorption that is fundamentally different from conventional B-mode ultrasound which depicts changes in acoustic impedance. A photoacoustic imaging system is developed using a commercial ultrasound system. To improve imaging contrast and depth penetration, absorption enhancing coating is applied to the seeds. In comparison to bare seeds, approximately 18.5 dB increase in signal-to-noise ratio as well as a doubling of imaging depth are achieved. Our results demonstrate that the coating of the seeds can further improve the discernibility of the seeds.

Pan, Leo; Baghani, Ali; Rohling, Robert; Abolmaesumi, Purang; Salcudean, Septimiu; Tang, Shuo

2013-03-01

326

Nonresonant photoacoustic monitoring of atmospheric methane  

NASA Astrophysics Data System (ADS)

The resonant and non-resonant photoacoustic (PA) detection of atmospheric trace gases is discussed with special respect to field measurements. Continuous in-situ methane measurements in a cow shed by a non-resonant PA detector applying an HeNe laser are reported, which allow the model based determination of the methane production rate of cows.

Fiedler, Michael; Goelz, C.; Platt, Ulrich

1993-02-01

327

Nonresonant photoacoustic monitoring of atmospheric methane  

Microsoft Academic Search

The resonant and non-resonant photoacoustic (PA) detection of atmospheric trace gases is discussed with special respect to field measurements. Continuous in-situ methane measurements in a cow shed by a non-resonant PA detector applying an HeNe laser are reported, which allow the model based determination of the methane production rate of cows.

Michael Fiedler; C. Goelz; Ulrich Platt

1993-01-01

328

Extensions of quartz-enhanced photoacoustic spectroscopy  

E-print Network

The goal of this thesis was to perform quartz-enhanced photoacoustic spectroscopy (QEPAS) on trace concentrations of NH3 in the 1.53 pm region with a DFB laser without the use of a resonating cavity. I analyzed the process ...

Masurkar, Amrita V

2009-01-01

329

In-vivo photoacoustic microscopy of nanoshell  

E-print Network

In-vivo photoacoustic microscopy of nanoshell extravasation from solid tumor vasculature Meng extravasation and accumulation of nanoshells within a solid tumor in vivo. PAM takes advan- tage of the strong near-infrared absorption of nanoshells and their extravasation tendency from leaky tumor vascu- latures

Wang, Lihong

330

Light scattering effects in photoacoustic spectroscopy  

Microsoft Academic Search

Consideration is given to the influence of light scattering on photoacoustic signals, and theoretical and experimental results are compared. It is shown that the theoretical results are based on a model in which the photons diffuse through the sample. An equation governing the diffusion process is solved with appropriate boundary conditions, which gives the distribution of photons in the sample.

Per Helander; Ingemar LundstrOm; Douglas McQueen

1980-01-01

331

On-line monitoring of biogenic isoprene emissions using photoacoustic spectroscopy  

Microsoft Academic Search

.   Isoprene (C5H8) is one of the most important biogenic volatile organic compounds (VOCs) in the atmosphere. To calculate the impact of isoprene\\u000a on atmospheric processes models have been developed that describe the isoprene release from plants. Measurements of this release\\u000a require techniques for a fast, sensitive, on-line isoprene detection.\\u000a \\u000a Photoacoustic (PA) spectroscopy is applied here for the first time

H. Dahnke; J. Kahl; G. Schüler; W. Boland; W. Urban; F. Kühnemann

2000-01-01

332

Piezoelectric dispenser based on a piezoelectric-metal-cavity actuator.  

PubMed

A piezoelectric dispenser has been fabricated based on the idea of a piezoelectric-metal-cavity (PMC) actuator. The PMC actuator consists of a metal ring sandwiched between two identical piezoelectric unimorphs. The radial contraction of the piezoelectric ceramic is converted into a flextensional motion of the unimorph, causing a large flexural displacement in the center part of the actuator. With the PMC actuator as a fluid chamber, the large flexural actuation can be used to produce the displacement needed to eject fluid. By applying an appropriate voltage to the piezoelectric unimorphs, a drop-on-demand ejection of ink or water can be achieved. The efficiency of fluid ejection can be enhanced after installing a valve in the fluid chamber. With the simple PMC structure, the dispenser can be operated with a low driving voltage of 12-15 V. PMID:19655984

Lam, K H; Sun, C L; Kwok, K W; Chan, H L W

2009-07-01

333

Piezoelectric dispenser based on a piezoelectric-metal-cavity actuator  

NASA Astrophysics Data System (ADS)

A piezoelectric dispenser has been fabricated based on the idea of a piezoelectric-metal-cavity (PMC) actuator. The PMC actuator consists of a metal ring sandwiched between two identical piezoelectric unimorphs. The radial contraction of the piezoelectric ceramic is converted into a flextensional motion of the unimorph, causing a large flexural displacement in the center part of the actuator. With the PMC actuator as a fluid chamber, the large flexural actuation can be used to produce the displacement needed to eject fluid. By applying an appropriate voltage to the piezoelectric unimorphs, a drop-on-demand ejection of ink or water can be achieved. The efficiency of fluid ejection can be enhanced after installing a valve in the fluid chamber. With the simple PMC structure, the dispenser can be operated with a low driving voltage of 12-15 V.

Lam, K. H.; Sun, C. L.; Kwok, K. W.; Chan, H. L. W.

2009-07-01

334

Piezoelectric actuators for dynamic applications  

Microsoft Academic Search

The main advantages of piezoelectrical actuators are their high resolution in motion and their excellent dynamic behavior. Especially the very short response times of solid state actuators presents new opportunities in developing high dynamical systems with unsurpassable characteristics. New concepts of piezoelectrically driven microoptical devices, e.g. optical fiber switches, intensity modulators and choppers, can be developed. Very compact systems with

Peter Buecker; Bernt Goetz; Thomas Martin

1998-01-01

335

Coaxing graphene to be piezoelectric  

NASA Astrophysics Data System (ADS)

Several exotic characteristics and properties have made graphene a well-studied material from both a basic science viewpoint as well as tantalizing applications ranging from nanoelectronics, gas separation membranes to ultracapacitors. Graphene, however, is non-piezoelectric. This is obvious when graphene is in its metallic or semi-metallic state. However, even when graphene is in dielectric form—which can be engineered through porosity or by using nanoribbons—graphene is non-piezoelectric due to its centrosymmetric crystal structure. Using quantum mechanical calculations, we show that merely by creating holes of the right symmetry, graphene can be coaxed to act as a piezoelectric. We find that certain specifically tailored porous graphene sheets can "acquire" piezoelectricity coefficient that is nearly 72% of the well-known piezoelectric (quartz) or 36% of boron nitride nanotubes.

Chandratre, Swapnil; Sharma, Pradeep

2012-01-01

336

High-Temperature Piezoelectrics with Large Piezoelectric Coefficients  

NASA Astrophysics Data System (ADS)

High-temperature piezoelectric materials are of interest for sensors and actuators in various industrial applications in which the devices are exposed to high temperature. A lot of research has been conducted in this area to bring forth a suitable piezoelectric material having a high Curie temperature for suitable usage at a high temperature with good piezoelectric properties. This report is an attempt to review the state of the art in high-temperature piezoelectric materials, covering their issues and concerns at elevated temperatures. Among the non-ferroelectric crystal classes, langasite and oxyborate crystals retain their piezoelectricity up to a very high temperature, but their piezoelectric coefficient is much smaller compared to a standard piezoelectric material such as lead zirconate titanate. A similar trend has also been observed in ferroelectric crystal class which shows poor piezoelectricity but retains it until a high temperature. Recent studies on solid solutions of bismuth-based oxides and lead titanate with the chemical formulae Bi(Me3+) O3-PbTiO3 and Bi(Me1Me2)O3-PbTiO3 (Me3+ represents a trivalent cation and Me1 and Me2 are cations having a combined valency of 3) show a much application potential of these materials due to improved piezoelectric property and high Curie temperature. BiScO3-PbTiO3, Bi(Mg0.5Ti0.5)O3-PbTiO3, (Bi(Ni0.5Ti0.5)O3-PbTiO3 and Bi(Zn0.5T0.5)O3-PbTiO3 are some interesting high-temperature piezoelectrics from the group of Bi(Me3+)O3-PbTiO3 and Bi(Me1Me2) O3-PbTiO3 which shows superior piezoelectric properties at high temperatures. Among the lead-free piezoelectrics, (K0.5Na0.5)NbO3 demands a special interest for further studies due to its plausible good piezoelectric property at elevated temperature.

Shinekumar, K.; Dutta, Soma

2014-12-01

337

High-Temperature Piezoelectrics with Large Piezoelectric Coefficients  

NASA Astrophysics Data System (ADS)

High-temperature piezoelectric materials are of interest for sensors and actuators in various industrial applications in which the devices are exposed to high temperature. A lot of research has been conducted in this area to bring forth a suitable piezoelectric material having a high Curie temperature for suitable usage at a high temperature with good piezoelectric properties. This report is an attempt to review the state of the art in high-temperature piezoelectric materials, covering their issues and concerns at elevated temperatures. Among the non-ferroelectric crystal classes, langasite and oxyborate crystals retain their piezoelectricity up to a very high temperature, but their piezoelectric coefficient is much smaller compared to a standard piezoelectric material such as lead zirconate titanate. A similar trend has also been observed in ferroelectric crystal class which shows poor piezoelectricity but retains it until a high temperature. Recent studies on solid solutions of bismuth-based oxides and lead titanate with the chemical formulae Bi(Me3+) O3-PbTiO3 and Bi(Me1Me2)O3-PbTiO3 (Me3+ represents a trivalent cation and Me1 and Me2 are cations having a combined valency of 3) show a much application potential of these materials due to improved piezoelectric property and high Curie temperature. BiScO3-PbTiO3, Bi(Mg0.5Ti0.5)O3-PbTiO3, (Bi(Ni0.5Ti0.5)O3-PbTiO3 and Bi(Zn0.5T0.5)O3-PbTiO3 are some interesting high-temperature piezoelectrics from the group of Bi(Me3+)O3-PbTiO3 and Bi(Me1Me2) O3-PbTiO3 which shows superior piezoelectric properties at high temperatures. Among the lead-free piezoelectrics, (K0.5Na0.5)NbO3 demands a special interest for further studies due to its plausible good piezoelectric property at elevated temperature.

Shinekumar, K.; Dutta, Soma

2015-02-01

338

Performance analysis of piezoelectric cantilever bending actuators  

Microsoft Academic Search

Bimorph and unimorph are two typical bending mode actuators, either consisting two piezoelectric layers or one piezoelectric layer and one elastic layer. In the case of bimorph actuator, when an electric field is applied to the piezoelectric layers, one layer expands while the other contract along length direction, producing a pure bending deformation. In unimorph actuator, when piezoelectric layer is

Qing-Ming Wang; L. Eric Cross

1998-01-01

339

Label-free oxygen-metabolic photoacoustic microscopy in vivo  

NASA Astrophysics Data System (ADS)

Almost all diseases, especially cancer and diabetes, manifest abnormal oxygen metabolism. Accurately measuring the metabolic rate of oxygen (MRO2) can be helpful for fundamental pathophysiological studies, and even early diagnosis and treatment of disease. Current techniques either lack high resolution or rely on exogenous contrast. Here, we propose label-free metabolic photoacoustic microscopy (mPAM) with small vessel resolution to noninvasively quantify MRO2 in vivo in absolute units. mPAM is the unique modality for simultaneously imaging all five anatomical, chemical, and fluid-dynamic parameters required for such quantification: tissue volume, vessel cross-section, concentration of hemoglobin, oxygen saturation of hemoglobin, and blood flow speed. Hyperthermia, cryotherapy, melanoma, and glioblastoma were longitudinally imaged in vivo. Counterintuitively, increased MRO2 does not necessarily cause hypoxia or increase oxygen extraction. In fact, early-stage cancer was found to be hyperoxic despite hypermetabolism.

Yao, Junjie; Maslov, Konstantin I.; Zhang, Yu; Xia, Younan; Wang, Lihong V.

2011-07-01

340

Quantum cascade laser based standoff photoacoustic chemical detection.  

PubMed

Standoff chemical detection with a distance of more than 41 feet using photoacoustic effect and quantum cascade laser (QCL) operated at relatively low power, less than 40 mW, is demonstrated for the first time. The option of using QCL provides the advantages of easy tuning and modulation besides the benefit of compact size, light weight and low power consumption. The standoff detection signal can be calibrated as a function of different parameters such as laser pulse energy, gas vapor concentration and detection distance. The results yield good agreements with theoretical model. Techniques to obtain even longer detection distance and achieve outdoor operations are in the process of implementation and their projection is discussed. PMID:21997036

Chen, Xing; Cheng, Liwei; Guo, Dingkai; Kostov, Yordan; Choa, Fow-Sen

2011-10-10

341

Plucked piezoelectric bimorphs for energy harvesting applications  

NASA Astrophysics Data System (ADS)

The modern drive towards mobility and wireless devices is motivating intense research in energy harvesting (EH) technologies. In an effort to reduce the battery burden of people, we are investigating a novel piezoelectric wearable energy harvester. As piezoelectric EH is significantly more effective at high frequencies, in opposition to the characteristically low-frequency human activities, we propose the use of an up-conversion strategy analogous to the pizzicato musical technique. In order to guide the design of such harvester, we have modelled with Finite Elements (FE) the response and power generation of a piezoelectric bimorph while it is "plucked", i.e. deflected, then released and permitted to vibrate freely. An experimental rig has been devised and set up to reproduce the action of the bimorph in the harvester. Measurements of the voltage output and the energy dissipated across a series resistor are reported and compared with the FE predictions. As the novel harvester will feature a number of bimorphs, each plucked tens of times per step, we predict a total power output of several mW, with imperceptible effect on the wearer's gait.

Pozzi, Michele; Zhu, Meiling

2011-06-01

342

Design of optimized piezoelectric HDD-sliders  

NASA Astrophysics Data System (ADS)

As storage data density in hard-disk drives (HDDs) increases for constant or miniaturizing sizes, precision positioning of HDD heads becomes a more relevant issue to ensure enormous amounts of data to be properly written and read. Since the traditional single-stage voice coil motor (VCM) cannot satisfy the positioning requirement of high-density tracks per inch (TPI) HDDs, dual-stage servo systems have been proposed to overcome this matter, by using VCMs to coarsely move the HDD head while piezoelectric actuators provides fine and fast positioning. Thus, the aim of this work is to apply topology optimization method (TOM) to design novel piezoelectric HDD heads, by finding optimal placement of base-plate and piezoelectric material to high precision positioning HDD heads. Topology optimization method is a structural optimization technique that combines the finite element method (FEM) with optimization algorithms. The laminated finite element employs the MITC (mixed interpolation of tensorial components) formulation to provide accurate and reliable results. The topology optimization uses a rational approximation of material properties to vary the material properties between 'void' and 'filled' portions. The design problem consists in generating optimal structures that provide maximal displacements, appropriate structural stiffness and resonance phenomena avoidance. The requirements are achieved by applying formulations to maximize displacements, minimize structural compliance and maximize resonance frequencies. This paper presents the implementation of the algorithms and show results to confirm the feasibility of this approach.

Nakasone, Paulo H.; Yoo, Jeonghoon; Silva, Emilio C. N.

2010-04-01

343

Narcotics detection using piezoelectric ringing  

NASA Astrophysics Data System (ADS)

Piezo-electric ringing (PER) has been demonstrated to be an effective means of scanning cargo for the presence of hidden narcotics. The PER signal is characteristic of certain types of crystallized material, such as cocaine hydrochloride. However, the PER signal cannot be used to conclusively identify all types of narcotic material, as the signal is not unique. For the purposes of cargo scanning, the PER technique is therefore most effective when used in combination with quadrupole resonance analysis (QRA). PER shares the same methodology as QRA technology, and can therefore be very easily and inexpensively integrated into existing QRA detectors. PER can be used as a pre-scanning technique before the QRA scan is applied and, because the PER scan is of a very short duration, can effectively offset some of the throughput limitations of standard QRA narcotics detectors. Following is a discussion of a PER detector developed by Quantum Manetics under contract to United States Customs. Design philosophy and performance are discussed, supported by results from recent tests conducted by the U.S. Drug Enforcement Agency and U.S. Customs.

Rayner, Timothy J.; Magnuson, Erik E.; West, Rebecca; Lyndquist, R.

1997-02-01

344

Investigation of standoff explosives detection via photothermal/photoacoustic interferometry  

NASA Astrophysics Data System (ADS)

Progress in standoff detection of surface-bound explosives residue using photothermal and photoacoustic (PT/PA) imaging and spectroscopy has been reported recently. Photothermal/photoacoustic interferometry (PTI), a variation of the aforementioned techniques, is a candidate for standoff detection as a result of its non-contact and non-destructive approach. In PTI, the transient PT/PA hydrodynamic response produced by impulsive infra-red laser excitation(s) are detected by an overlapping focused probe laser beam. The return back-scattered/reflected probe laser beam is collected and coupled into a single-mode optical fiber. The PT/PA-induced perturbation on the return probe laser, in the form of phase or amplitude modulation or both, is extracted interferometrically. The resulting quadrature signals are digitized and processed to recover the minute PT/PA dynamics above background noise. Characteristic spectra for materials can be obtained by quantifying the PT response as a function of excitation(s) wavelength. The CW probe laser, operating in the 1550 nm range, and the constituents of the coherent detection system are commercial off-the-shelf components. A commercially available and continuously tunable quantum cascade laser (QCL) with output pulse energies up to 50 nJ was employed to generate the PT/PA spectra in the 8.8-10.2 ?m range. PTI detected absorption spectra were collected for HMX, RDX, and PETN, with the probe laser system positioned 5 meters away from the explosives targets. In addition, PTI measurements of the stimulated Raman (SR) spectra of ammonium nitrate and 2,4,6-trinitrotoluene obtained using a near-IR OPO laser are described. We believe this is the first-ever application of photothermal techniques to the measurement of the SR effect on solid explosive materials at meaningful standoff distances.

Cho, Pak S.; Jones, Robert M.; Shuman, Timothy; Scoglietti, Daniel; Harston, Geof

2011-05-01

345

Influence of external and technological stresses on photoacoustic images of Vickers indented ceramics and metals  

Microsoft Academic Search

The theoretical model of the photoacoustic effect in stressed solids with application to analysis to the photoacoustic signal behavior near vertical crack tips is developed. Photoacoustic images for Vickers indentation zones in ceramics and metals are presented. It is demonstrated the influence of the given external mechanical stresses on the photoacoustic images of Vickers indentations both for ceramics and metals.

Kyrill L. Muratikov; Alexej L. Glazov

2007-01-01

346

Contrast distortion correction for photoacoustic image based on compensation for pressure distribution of sound field  

Microsoft Academic Search

The nonuniform energy density distribution of laser pulses leads to nonuniform pressure distribution of sound field on photoacoustic effect, and photoacoustic image would be distorted at the edge of the absorbed optical energy deposit area. In this paper, a new method for compensating the sound field pressure and correcting the photoacoustic image is reported and testified. Distribution of the photoacoustic

Y. Yuan; S. Yang; L. Xiang

2010-01-01

347

Tunable fiber laser and fiber amplifier based photoacoustic spectrometer for trace gas detection.  

PubMed

A new wavelength modulated photoacoustic spectrometer based on a near-infrared tunable erbium doped fiber laser (TEDFL) and an erbium doped fiber amplifier (EDFA) is first developed for trace gas detection. This sensor has been applied to the detection of ammonia using a first longitudinal resonant photoacoustic cell with double absorption optical path (L=20cm) and lock-in harmonic detection technique. The minimum detectable limit of 3 parts-per-billion volume (signal-to-noise ratio=1) and response time of approximately 1min is achieved at room temperature and atmospheric pressure with 100ms time constant and 500mW optical power at the 1531.7nm transition line. PMID:19781982

Peng, Yong; Zhang, Wang; Li, Liang; Yu, Qingxu

2009-11-01

348

Born-ratio type data normalization improves quantitation in photoacoustic tomography  

NASA Astrophysics Data System (ADS)

In this report, we present a Born-ratio type of data normalization for reconstruction of initial acoustic pressure distribution in photoacoustic tomography (PAT). The normalized Born-ratio type of data is obtained as a ratio of photoacoustic pressure obtained with tissue sample in a coupling medium to the one obtained using purely coupling medium. It is shown that this type of data normalization improves the quantitation (intrinsic contrast) of the reconstructed images in comparison to the traditional techniques (unnormalized) that are currently available in PAT. Studies are carried out using various tissue samples. The robustness of the proposed method is studied at various noise levels added to the collected data. The improvement in quantitation can enable accurate estimation of pathophysiological parameter (optical absorption coefficient, ?a) of tissue sample under investigation leading to better sensitivity in PAT.

Singh, M. Suheshkumar; Yalavarthy, Phaneendra K.

2014-03-01

349

Interlaced photoacoustic and ultrasound imaging system with real-time coregistration for ovarian tissue characterization  

NASA Astrophysics Data System (ADS)

Coregistered ultrasound (US) and photoacoustic imaging are emerging techniques for mapping the echogenic anatomical structure of tissue and its corresponding optical absorption. We report a 128-channel imaging system with real-time coregistration of the two modalities, which provides up to 15 coregistered frames per second limited by the laser pulse repetition rate. In addition, the system integrates a compact transvaginal imaging probe with a custom-designed fiber optic assembly for in vivo detection and characterization of human ovarian tissue. We present the coregistered US and photoacoustic imaging system structure, the optimal design of the PC interfacing software, and the reconfigurable field programmable gate array operation and optimization. Phantom experiments of system lateral resolution and axial sensitivity evaluation, examples of the real-time scanning of a tumor-bearing mouse, and ex vivo human ovaries studies are demonstrated.

Alqasemi, Umar; Li, Hai; Yuan, Guangqian; Kumavor, Patrick; Zanganeh, Saeid; Zhu, Quing

2014-07-01

350

Interlaced photoacoustic and ultrasound imaging system with real-time coregistration for ovarian tissue characterization.  

PubMed

Coregistered ultrasound (US) and photoacoustic imaging are emerging techniques for mapping the echogenic anatomical structure of tissue and its corresponding optical absorption. We report a 128-channel imaging system with real-time coregistration of the two modalities, which provides up to 15 coregistered frames per second limited by the laser pulse repetition rate. In addition, the system integrates a compact transvaginal imaging probe with a custom-designed fiber optic assembly for in vivo detection and characterization of human ovarian tissue. We present the coregistered US and photoacoustic imaging system structure, the optimal design of the PC interfacing software, and the reconfigurable field programmable gate array operation and optimization. Phantom experiments of system lateral resolution and axial sensitivity evaluation, examples of the real-time scanning of a tumor-bearing mouse, and ex vivo human ovaries studies are demonstrated. PMID:25069009

Alqasemi, Umar; Li, Hai; Yuan, Guangqian; Kumavor, Patrick; Zanganeh, Saeid; Zhu, Quing

2014-07-01

351

High-resolution photoacoustic tomography of resting-state functional connectivity in the mouse brain  

PubMed Central

The increasing use of mouse models for human brain disease studies presents an emerging need for a new functional imaging modality. Using optical excitation and acoustic detection, we developed a functional connectivity photoacoustic tomography system, which allows noninvasive imaging of resting-state functional connectivity in the mouse brain, with a large field of view and a high spatial resolution. Bilateral correlations were observed in eight functional regions, including the olfactory bulb, limbic, parietal, somatosensory, retrosplenial, visual, motor, and temporal regions, as well as in several subregions. The borders and locations of these regions agreed well with the Paxinos mouse brain atlas. By subjecting the mouse to alternating hyperoxic and hypoxic conditions, strong and weak functional connectivities were observed, respectively. In addition to connectivity images, vascular images were simultaneously acquired. These studies show that functional connectivity photoacoustic tomography is a promising, noninvasive technique for functional imaging of the mouse brain. PMID:24367107

Nasiriavanaki, Mohammadreza; Xia, Jun; Wan, Hanlin; Bauer, Adam Quentin; Culver, Joseph P.; Wang, Lihong V.

2014-01-01

352

Functional photoacoustic imaging to observe regional brain activation induced by cocaine hydrochloride  

NASA Astrophysics Data System (ADS)

Photoacoustic microscopy (PAM) was used to detect small animal brain activation in response to drug abuse. Cocaine hydrochloride in saline solution was injected into the blood stream of Sprague Dawley rats through tail veins. The rat brain functional change in response to the injection of drug was then monitored by the PAM technique. Images in the coronal view of the rat brain at the locations of 1.2 and 3.4 mm posterior to bregma were obtained. The resulted photoacoustic (PA) images showed the regional changes in the blood volume. Additionally, the regional changes in blood oxygenation were also presented. The results demonstrated that PA imaging is capable of monitoring regional hemodynamic changes induced by drug abuse.

Jo, Janggun; Yang, Xinmai

2011-09-01

353

High frequency photoacoustic imaging for in vivo visualizing blood flow of zebrafish heart  

PubMed Central

A technique on high frame rate(28fps), high frequency co-registered ultrasound and photoacoustic imaging for visualizing zebrafish heart blood flow was demonstrated. This approach was achieved with a 40MHz light weight(0.38g) ring-type transducer, serving as the ultrasound transmitter and receiver, to allow an optic fiber, coupled with a 532nm laser, to be inserted into the hole. From the wire target study, axial resolutions of 38µm and 42µm were obtained for ultrasound and photoacoustic imaging, respectively. Carbon nanotubes were utilized as contrast agents to increase the flow signal level by 20dB in phantom studies, and zebrafish heart blood flow was successfully observed. PMID:23787651

Park, Jinhyoung; Cummins, Thomas M.; Harrison, Michael; Lee, Jungwoo; Zhou, Qifa; Lien, Ching-Ling; Shung, K. Kirk

2013-01-01

354

Photoacoustic imaging of functional domains in primary motor cortex in rhesus macaques  

NASA Astrophysics Data System (ADS)

Functional detection in primate brains has particular advantages because of the similarity between non-human primate brain and human brain and the potential for relevance to a wide range of conditions such as stroke and Parkinson's disease. In this research, we used photoacoustic imaging (PAI) technique to detect functional changes in primary motor cortex of awake rhesus monkeys. We observed strong increases in photoacoustic signal amplitude during both passive and active forelimb movement, which indicates an increase in total hemoglobin concentration resulting from activation of primary motor cortex. Further, with PAI approach, we were able to obtain depthresolved functional information from primary motor cortex. The results show that PAI can reliably detect primary motor cortex activation associated with forelimb movement in rhesus macaques with a minimal-invasive approach.

Jo, Janggun; Zhang, Hongyu; Cheney, Paul; Yang, Xinmai

2012-02-01

355

Can molecular imaging enable personalized diagnostics? An example using magnetomotive photoacoustic imaging  

PubMed Central

The advantages of photoacoustic imaging, including low cost, non-ionizing operation, and sub-mm spatial resolution at centimeters depth, make it a promising modality to probe nanoparticle-targeted abnormalities in real time at cellular and molecular levels. However, detecting rare cell types in a heterogeneous background with strong optical scattering and absorption remains a big challenge. For example, differentiating circulating tumor cells in vivo (typically fewer than 10 cells/ml for an active tumor) among billions of erythrocytes in the blood is nearly impossible. In this paper, a newly developed technique, magnetomotive photoacoustic (mmPA) imaging, which can greatly increase the sensitivity and specificity of sensing targeted cells or molecular interactions, is reviewed. Its primary advantage is suppression of background signals through magnetic enrichment/manipulation with simultaneous photoacoustic detection of magnetic contrast agent targeted objects. Results from phantom and in vitro studies demonstrate the capability of mmPA imaging to differentiate regions targeted with magnetic nanoparticles from the background, and to trap and sensitively detect targeted cells at a concentration of a single cell per milliliter in a flow system mimicking a human peripheral artery. This technique provides an example of the ways in which molecular imaging can potentially enable robust molecular diagnosis and treatment, and accelerate the translation of molecular medicine into the clinic. PMID:23982280

O'Donnell, Matthew; Wei, Chen-wei; Xia, Jinjun; Pelivanov, Ivan; Jia, Congxian; Huang, Sheng-Wen; Hu, Xiaoge; Gao, Xiaohu

2013-01-01

356

Design Requirements for Amorphous Piezoelectric Polymers  

NASA Technical Reports Server (NTRS)

An overview of the piezoelectric activity in amorphous piezoelectric polymers is presented. The criteria required to render a polymer piezoelectric are discussed. Although piezoelectricity is a coupling between mechanical and electrical properties, most research has concentrated on the electrical properties of potentially piezoelectric polymers. In this work, we present comparative mechanical data as a function of temperature and offer a summary of polarization and electromechanical properties for each of the polymers considered.

Ounaies, Z.; Young, J. A.; Harrison, J. S.

1999-01-01

357

Radial Field Piezoelectric Diaphragms  

NASA Technical Reports Server (NTRS)

A series of active piezoelectric diaphragms were fabricated and patterned with several geometrically defined Inter-Circulating Electrodes "ICE" and Interdigitated Ring Electrodes "ICE". When a voltage potential is applied to the electrodes, the result is a radially distributed electric field that mechanically strains the piezoceramic along the Z-axis (perpendicular to the applied electric field). Unlike other piezoelectric bender actuators, these Radial Field Diaphragms (RFDs) strain concentrically yet afford high displacements (several times that of the equivalent Unimorph) while maintaining a constant circumference. One of the more intriguing aspects is that the radial strain field reverses itself along the radius of the RFD while the tangential strain remains relatively constant. The result is a Z-deflection that has a conical profile. This paper covers the fabrication and characterization of the 5 cm. (2 in.) diaphragms as a function of poling field strength, ceramic thickness, electrode type and line spacing, as well as the surface topography, the resulting strain field and displacement as a function of applied voltage at low frequencies. The unique features of these RFDs include the ability to be clamped about their perimeter with little or no change in displacement, the environmentally insulated packaging, and a highly repeatable fabrication process that uses commodity materials.

Bryant, R. G.; Effinger, R. T., IV; Copeland, B. M., Jr.

2002-01-01

358

Ferroelastic Characterization of Piezoelectrics  

NASA Astrophysics Data System (ADS)

The elastic deformation behavior of an isotropic material is governed by Young's modulus Y and Poisson's ratio ?. Knowledge of the Young's modulus, for instance, is necessary to split the total deformation S i measured under load stress T i into elastic S {/i el} and "plastic" S {/i pl} strain contributions S_i = S_i^el + S_i^pl = {T_i over Y} + S_i^pl , where Y is not necessarily a constant, but may depend on the amount of nonelastic strains, as will be shown later. The methods for the determination of the Young's moduli, well-known from conventional ceramics and also applicable to unpoled piezoelectric materials, are much more complicated for nonisotropic materials due to the tensorial character of the modulus and the special electric boundary conditions [1]. The conditions of a constant electrical field, E z ? E 3 = const, or a constant dielectric displacement, D z ? E 3 = const, influence the elastic properties. This effect may be illustrated for a uniaxial stress state with T x ? T 1 ? 0 exclusively. In the case of a piezoelectric material, we are interested in the components D_3 = d_{31}T_1 + \\varepsilon_{33}^T E_3 .

Fett, T.

359

Optical coherence photoacoustic microscopy: accomplishing optical coherence tomography and photoacoustic microscopy with a single light source  

PubMed Central

Abstract. We developed optical coherence photoacoustic microscopy (OC-PAM) to demonstrate that the functions of optical coherence tomography (OCT) and photoacoustic microscopy (PAM) can be achieved simultaneously by using a single illuminating light source. We used a pulsed broadband laser centered at 580 nm and detected the absorbed photons through photoacoustic detection and the back-scattered photons with an interferometer. In OC-PAM, each laser pulse generates both one OCT A-line and one PAM A-line simultaneously; as a result, the two imaging modalities are intrinsically co-registered in the lateral directions. In vivo images of the mouse ear were acquired to demonstrate the capabilities of OC-PAM. PMID:22502553

Zhang, Xiangyang; Zhang, Hao F.; Jiao, Shuliang

2012-01-01

360

Indocyanine Green-Loaded Photoacoustic Nanodroplets – Dual Contrast Nanoconstructs for Enhanced Photoacoustic and Ultrasound Imaging  

PubMed Central

Recently, perfluorocarbon (PFC) nanodroplets were introduced as contrast agents for imaging and image-guided therapy. For example, in sonography, high-intensity ultrasound pulses were used to phase-transition liquid perfluorocarbon to produce gas microbubbles. More recently, perfluorocarbon nanodroplets with encapsulated gold nanorods were used as dual ultrasound/photoacoustic contrast agents. To expedite clinical translation, we synthesized and characterized ICG-loaded perfluorocarbon nanodroplets, i.e. constructs comprising biocompatible, non-toxic and biologically safe materials. We then demonstrated enhanced photoacoustic contrast through optically triggered phase transition of PFC nanodroplets and ultrasound contrast from the resulting PFC bubbles. We assessed the quality enhancement of photoacoustic and ultrasound images through analysis of contrast and contrast-to-noise ratio. We further investigated the changes in image contrast due to increased ambient temperature. Our studies suggest that ICG-loaded perfluorocarbon nanodroplets may become a valuable tool for various imaging modalities, and have promising therapeutic applications. PMID:24303934

Hannah, Alexander; Luke, Geoffrey; Wilson, Katheryne; Homan, Kimberly Ann; Emelianov, Stanislav

2014-01-01

361

Photoacoustic and Photothermal Effects in Particulate Suspensions  

SciTech Connect

A summary of the research areas investigated by the author during the grant period is given. Experiments and theory have been carried out on the photoacoustic effect arising from a number of physical and chemical processes. A number of studies of the photoacoustic effect as it occurs in transient grating experiments have been completed. The research done with the Ludwig-Soret effect on the generation of shock waves is reported. Other research, such as that carried out on interferometric and beam deflection microphones, the use of microphones in vacuum as momentum flux detectors, and chemical generation of sonoluminescence is listed. A list of published research including selected publications, a complete list of journal articles, books, review articles, and reviews are given.

Diebold, Gerald, J.

2009-04-30

362

Photoacoustic microscopy for ovarian tissue characterization  

NASA Astrophysics Data System (ADS)

In this paper, we present the construction of an optical-resolution photoacoustic microscopy (OR-PAM) system and studies done on the characterization of human ovarian tissue with malignant and benign features ex vivo. PAM images of the ovaries showed more detailed blood vessel distributions with much higher resolution compared with conventional photoacoustic images obtained with array transducers. In all, 29 PAM images (20 from normal ovaries and 9 from malignant ovaries) were studied. Eight different features were extracted quantitatively from the PAM images, and a generalized linear model (GLM) was used to classify the ovaries as normal or malignant. By using the GLM, a specificity of 100% and a sensitivity of 100% were obtained for the training set. These preliminary results demonstrate the feasibility of our PAM system in mapping microvasculature networks, as well as characterizing the ovarian tissue, and could be extremely valuable in assisting surgeons for in vivo evaluation of ovarian tissue.

Wang, Tianheng; Yang, Yi; Alqasemi, Umar; Kumavor, Patrick D.; Brewer, Molly; Zhu, Quing

2013-03-01

363

A photoacoustic spectrometer for trace gas detection  

NASA Astrophysics Data System (ADS)

A high-resolution external laser photoacoustic spectrometer has been developed for trace gas detection with absorption transitions in coincidence with CO2 laser emission lines (9,2-10,9 ?m: 920-1086 cm-1). The CO2 laser operates in 90 CW lines with power of up to 15 W. A PC-controlled step motor can tune the laser lines. The resonance frequency of first longitudinal mode of the photoacoustic cell is at 1600 Hz. The cell Q-factor and cell constant are measured close to 50 and 28 mVcmW-1, respectively. The spectrometer has been tested in preliminary studies to analyze the absorption transitions of ozone (O_3). The ethylene (C_2H_4) from papaya fruit is also investigated using N2 as carrier gas at a constant flow rate.

Telles, E. M.; Bezerra, E.; Scalabrin, A.

2005-06-01

364

Ultrahigh resolution photoacoustic microscopy via transient absorption.  

PubMed

We have developed a novel, hybrid imaging modality, Transient Absorption Ultrasonic Microscopy (TAUM), which takes advantage of the optical nonlinearities afforded by transient absorption to achieve ultrahigh-resolution photoacoustic microscopy. The theoretical point spread function for TAUM is functionally equivalent to confocal and two-photon fluorescence microscopy, potentially enabling cellular/subcellular photoacoustic imaging. A prototype TAUM system was designed, built, and used to image a cross-section through several capillaries in the excised cheek pouch of a Syrian Hamster. The well-resolved capillaries in the TAUM image provided experimental evidence of the spatial resolution. These results suggest that TAUM has excellent potential for producing volumetric images with cellular/subcellular resolution in three dimensions deep inside living tissue. PMID:21258499

Shelton, Ryan L; Applegate, Brian E

2010-01-01

365

In vivo optically encoded photoacoustic flowgraphy.  

PubMed

We present an optically encoded photoacoustic (PA) flow imaging method based on optical-resolution PA microscopy. An intensity-modulated continuous-wave laser photothermally encodes the flowing medium, and a pulsed laser generates PA waves to image the encoded heat pattern. Flow speeds can be calculated by cross correlation. The method was validated in phantoms at flow speeds ranging from 0.23 to 11??mm/s. Venous blood flow speed in a mouse ear was also measured. PMID:24978744

Zhang, Ruiying; Wang, Lidai; Yao, Junjie; Yeh, Cheng-Hung; Wang, Lihong V

2014-07-01

366

Multiscale photoacoustic microscopy and computed tomography  

Microsoft Academic Search

Photoacoustic tomography (PAT) is probably the fastest-growing area of biomedical imaging technology, owing to its capacity for high-resolution sensing of rich optical contrast in vivo at depths beyond the optical transport mean free path (~1 mm in human skin). Existing high-resolution optical imaging technologies, such as confocal microscopy and two-photon microscopy, have had a fundamental impact on biomedicine but cannot

Lihong V. Wang

2009-01-01

367

Thermal nonlinearity in a photoacoustic cell  

Microsoft Academic Search

The effect of the thermal nonlinearity caused by the temperature dependence of the specific heat and thermal conductivity\\u000a of a sample, substrate, and air on the temperature field in a photoacoustic cell is stud-ied theoretically. Exact solutions\\u000a are obtained for a steady temperature field with allowance for thermal nonlin-earity and for a nonsteady field without allowance\\u000a for this nonlinearity. The

U. Madvaliev; T. Kh. Salikhov; D. M. Sharifov

2004-01-01

368

Photoacoustic cavitation in spherical and cylindrical absorbers  

Microsoft Academic Search

.   Photomechanical damage in absorbing regions or particles surrounded by a non-absorbing medium is investigated experimentally\\u000a and theoretically. The damage mechanism is based on the generation of thermoelastic pressure by absorption of pulsed laser\\u000a radiation under conditions of stress confinement. Principles of photoacoustic sound generation predict that the acoustic wave\\u000a generated in a finite-size absorbing region must contain both compressive

G. Paltauf; H. Schmidt-Kloiber

1999-01-01

369

Quantitative Photo-Acoustic Imaging of Small Absorbers Habib Ammari  

E-print Network

Quantitative Photo-Acoustic Imaging of Small Absorbers Habib Ammari Emmanuel Bossy Vincent Jugnon Hyeonbae Kang§ December 1, 2009 Abstract In photo-acoustic imaging, energy absorption causes thermo absorber from the absorbed density. AMS subject classifications. 31B20, 35B37,35L05 Key words. photo

Kang, Hyeonbae

370

Photoacoustic Doppler Effect from Flowing Small Light-Absorbing Particles  

Microsoft Academic Search

From the flow of a suspension of micrometer-scale carbon particles, the photoacoustic Doppler shift is observed. As predicted theoretically, the observed Doppler shift equals half of that in Doppler ultrasound and does not depend on the direction of laser illumination. This new physical phenomenon provides a basis for developing photoacoustic Doppler flowmetry, which can potentially be used for detecting fluid

Hui Fang; Konstantin Maslov; Lihong V. Wang

2007-01-01

371

Pulsed photoacoustic gas cell design for low pressure studies  

Microsoft Academic Search

The designing of the photoacoustic cell is critical to obtain rather good signal to noise ratio. All theoretical and experimental studies predict that for a constant light absorption, the amplitude of the photoacoustic signal reaching the microphone depends on the size of the cell and in general increases as cell dimensions are reduced. For constant laser energy and beam –

M. D. Rabasovi?; J. D. Nikoli?; D. D. Markushev; J. Jovanovi?-Kurepa

2008-01-01

372

Simulation study of photoacoustic coded excitation using Golay Codes  

Microsoft Academic Search

Photoacoustics (PA) is a new imaging modality based on the generation of ultrasound due to laser irradiation. Instead of commonly used Q-switched Nd:YAG lasers the application of pulsed laser diodes as light sources for photoacoustic imaging is proposed. The high pulse repetition frequency of laser diodes enables the usage of coded excitation schemes for SNR improvement. Therefore, the performance of

Martin P. Mienkina; Annika Eder; Georg Schmitz; Claus-Stefan Friedrich; Nils C. Gerhardt; Martin R. Hofmann

2008-01-01

373

Acoustic and photoacoustic characterization of micron-sized perfluorocarbon emulsions.  

PubMed

Perfluorocarbon droplets containing nanoparticles (NPs) have recently been investigated as theranostic and dual-mode contrast agents. These droplets can be vaporized via laser irradiation or used as photoacoustic contrast agents below the vaporization threshold. This study investigates the photoacoustic mechanism of NP-loaded droplets using photoacoustic frequencies between 100 and 1000 MHz, where distinct spectral features are observed that are related to the droplet composition. The measured photoacoustic spectrum from NP-loaded perfluorocarbon droplets was compared to a theoretical model that assumes a homogenous liquid. Good agreement in the location of the spectral features was observed, which suggests the NPs act primarily as optical absorbers to induce thermal expansion of the droplet as a single homogenous object. The NP size and composition do not affect the photoacoustic spectrum; therefore, the photoacoustic signal can be maximized by optimizing the NP optical absorbing properties. To confirm the theoretical parameters in the model, photoacoustic, ultrasonic, and optical methods were used to estimate the droplet diameter. Photoacoustic and ultrasonic methods agreed to within 1.4%, while the optical measurement was 8.5% higher; this difference decreased with increasing droplet size. The small discrepancy may be attributed to the difficulty in observing the small droplets through the partially translucent phantom. PMID:23085917

Strohm, Eric M; Gorelikov, Ivan; Matsuura, Naomi; Kolios, Michael C

2012-09-01

374

Photoacoustic imaging and characterization of the microvasculature  

PubMed Central

Photoacoustic (optoacoustic) tomography, combining optical absorption contrast and highly scalable spatial resolution (from micrometer optical resolution to millimeter acoustic resolution), has broken through the fundamental penetration limit of optical ballistic imaging modalities—including confocal microscopy, two-photon microscopy, and optical coherence tomography—and has achieved high spatial resolution at depths down to the diffusive regime. Optical absorption contrast is highly desirable for microvascular imaging and characterization because of the presence of endogenous strongly light-absorbing hemoglobin. We focus on the current state of microvascular imaging and characterization based on photoacoustics. We first review the three major embodiments of photoacoustic tomography: microscopy, computed tomography, and endoscopy. We then discuss the methods used to characterize important functional parameters, such as total hemoglobin concentration, hemoglobin oxygen saturation, and blood flow. Next, we highlight a few representative applications in microvascular-related physiological and pathophysiological research, including hemodynamic monitoring, chronic imaging, tumor-vascular interaction, and neurovascular coupling. Finally, several potential technical advances toward clinical applications are suggested, and a few technical challenges in contrast enhancement and fluence compensation are summarized. PMID:20210427

Hu, Song; Wang, Lihong V.

2010-01-01

375

Acoustic and Photoacoustic Molecular Imaging of Cancer  

PubMed Central

Ultrasound and combined optical and ultrasonic (photoacoustic) molecular imaging have shown great promise in the visualization and monitoring of cancer through imaging of vascular and extravascular molecular targets. Contrast-enhanced ultrasound with molecularly targeted microbubbles can detect early-stage cancer through the visualization of targets expressed on the angiogenic vasculature of tumors. Ultrasonic molecular imaging can be extended to the imaging of extravascular targets through use of nanoscale, phase-change droplets and photoacoustic imaging, which provides further molecular information on cancer given by the chemical composition of tissues and by targeted nanoparticles that can interact with extravascular tissues at the receptor level. A new generation of targeted contrast agents goes beyond merely increasing imaging signal at the site of target expression but shows activatable and differential contrast depending on their interactions with the tumor microenvironment. These innovations may further improve our ability to detect and characterize tumors. In this review, recent developments in acoustic and photoacoustic molecular imaging of cancer are discussed. PMID:24187042

Wilson, Katheryne E.; Wang, Tzu Yin; Willmann, Jürgen K.

2014-01-01

376

Imaging hypoxia using 3D photoacoustic spectroscopy  

NASA Astrophysics Data System (ADS)

Purpose: The objective is to develop a multivariate in vivo hemodynamic model of tissue oxygenation (MiHMO2) based on 3D photoacoustic spectroscopy. Introduction: Low oxygen levels, or hypoxia, deprives cancer cells of oxygen and confers resistance to irradiation, some chemotherapeutic drugs, and oxygen-dependent therapies (phototherapy) leading to treatment failure and poor disease-free and overall survival. For example, clinical studies of patients with breast carcinomas, cervical cancer, and head and neck carcinomas (HNC) are more likely to suffer local reoccurrence and metastasis if their tumors are hypoxic. A novel method to non invasively measure tumor hypoxia, identify its type, and monitor its heterogeneity is devised by measuring tumor hemodynamics, MiHMO2. Material and Methods: Simulations are performed to compare tumor pO2 levels and hypoxia based on physiology - perfusion, fractional plasma volume, fractional cellular volume - and its hemoglobin status - oxygen saturation and hemoglobin concentration - based on in vivo measurements of breast, prostate, and ovarian tumors. Simulations of MiHMO2 are performed to assess the influence of scanner resolutions and different mathematic models of oxygen delivery. Results: Sensitivity of pO2 and hypoxic fraction to photoacoustic scanner resolution and dependencies on model complexity will be presented using hemodynamic parameters for different tumors. Conclusions: Photoacoustic CT spectroscopy provides a unique ability to monitor hemodynamic and cellular physiology in tissue, which can be used to longitudinally monitor tumor oxygenation and its response to anti-angiogenic therapies.

Stantz, Keith M.

2010-02-01

377

Precision piezoelectric stepping motor using piezoelectric torsional actuator  

NASA Astrophysics Data System (ADS)

This paper deals with a newly developed piezoelectric motor that generates precise stepping motion using a piezoelectric torsional actuator and a pair of one-way clutch bearings. The torsional actuator consists of a piezoelectric cylinder that produces rotation motion invoking shear mode of piezoelectric materials and a torsion bar that magnifies the rotation angle produced from the piezoelectric cylinder. Inner one-way clutch bearing is fit on the torsion bar and outer bearing is mounted outside of the inner bearing such that when the torsion bar rotates in one direction, the inner bearing moves together while the outer one slips. When the torsion bar rotates in opposite direction, the inner bearing slips against the torsion bar while the outer bearing locks the inner bearing so as to accumulate the rotation angle. Because the elaborate piezoelectric torsional actuator functions as the driving source at high frequency, a precise step motion with high speed can be produced. The optimum condition for driving the motor is investigated in terms of excitation frequency, electrical impedance and the location of the bearing set. The rotation speed and torque of the motor is investigated, and 350 rpm and 0.19mNm torque are observed in maximum.

Kang, Byung-Woo; Kim, Jaehwan; Cheong, ChaeCheon; Yang, Bo-Won

2001-03-01

378

Structure and piezoelectric properties of lead-free bismuth-based perovskite solid solutions.  

E-print Network

??A new group of lead free piezoelectric perovskite solid solutions, (1-x)Bi(B'B")O?-xABO?, were obtained via solid-state processing techniques. The solubility of unstable perovskite Bi(B'B")O? compounds into… (more)

Huang, Chien-Chih

2008-01-01

379

Theory and analysis of frequency-domain photoacoustic tomography.  

PubMed

A new frequency-domain approach to photoacoustic tomography has recently been proposed, promising to overcome some of the shortcomings associated with the pulsed photoacoustic approach. This approach offers many of the benefits of pulsed photoacoustics but requires a different set of equations for modeling of the forward and inverse problems due to the longer time scales involved in the optical input signal. The theory of photoacoustic tomography with an optical input that is not necessarily a short pulse is considered in this paper. The full optical, thermal, and acoustic governing equations are derived. A transfer function approach is taken for the solution and analysis of this problem. The results and implications are compared with those of pulsed photoacoustics and traditional ultrasonic diffraction tomography. A Fourier diffraction theorem is also presented, which could be used as a basis for the development of tomographic imaging algorithms. PMID:18529177

Baddour, Natalie

2008-05-01

380

A Resonant Damping Study Using Piezoelectric Materials  

NASA Technical Reports Server (NTRS)

Excessive vibration of turbomachinery blades causes high cycle fatigue (HCF) problems requiring damping treatments to mitigate vibration levels. Based on the technical challenges and requirements learned from previous turbomachinery blade research, a feasibility study of resonant damping control using shunted piezoelectric patches with passive and active control techniques has been conducted on cantilever beam specimens. Test results for the passive damping circuit show that the optimum resistive shunt circuit reduces the third bending resonant vibration by almost 50%, and the optimum inductive circuit reduces the vibration by 90%. In a separate test, active control reduced vibration by approximately 98%.

Min, J. B.; Duffy, K. P.; Choi, B. B.; Morrison, C. R.; Jansen, R. H.; Provenza, A. J.

2008-01-01

381

Piezoelectric microcantilever serum protein detector  

NASA Astrophysics Data System (ADS)

The development of a serum protein detector will provide opportunities for better screening of at-risk cancer patients, tighter surveillance of disease recurrence and better monitoring of treatment. An integrated system that can process clinical samples for a number of different types of biomarkers would be a useful tool in the early detection of cancer. Also, screening biomarkers such as antibodies in serum would provide clinicians with information regarding the patient's response to treatment. Therefore, the goal of this study is to develop a sensor which can be used for rapid, all-electrical, real-time, label-fee, in-situ, specific quantification of cancer markers, e.g., human epidermal receptor 2 (Her2) or antibodies, in serum. To achieve this end, piezoelectric microcantilever sensors (PEMS) were constructed using an 8 mum thick lead magnesium niobate-lead titanate (PMN-PT) freestanding film as the piezoelectric layer. The desired limit of detection is on the order of pg/mL. In order to achieve this goal the higher frequency lateral extension modes were used. Also, as the driving and sensing of the PEMS is electrical, the PEMS must be insulated in a manner that allows it to function in aqueous solutions. The insulation layer must also be compatible with standardized bioconjugation techniques. Finally, detection of both cancer antigens and antibodies in serum was carried out, and the results were compared to a standard commercialized protocol. PEMS have demonstrated the capability of detecting Her2 at a concentration of 5 pg/mL in diluted human serum (1:40) in less than 1 hour. The approach can be easily translated into the clinical setting because the sensitivity is more than sufficient for monitoring prognosis of breast cancer patients. In addition to Her2 detection, antibodies in serum were assayed in order to demonstrate the feasibility of monitoring the immune response for antibody-dependent cellular cytotoxicity (ADCC) in patients on antibody therapies such as Herceptin and Cetuximab. The PEMS displayed a limit of detection of 100 fg/mL, which was 100 times lower than the current methods of protein detection in serum, such as ELISA. Furthermore, the sensitivity of the PEMS device allows it to be capable of determining the dissociation constant, K d, of selective receptors such as antibodies. Using the dose response trials of Her2, Kd has been deduced for H3 scFv, and Herceptin, a commercial antibody specific for Her2.

Capobianco, Joseph A.

382

Piezoelectric One-Way Remote  

NSDL National Science Digital Library

In this activity, learners construct a device out of a piezoelectric igniter, like those used as barbecue lighters. Learners use the device to remotely start current flowing in a simple series circuit containing a small electric fan.

Rathjen, Don

2004-01-01

383

Piezoelectric MEMS for energy harvesting  

E-print Network

Piezoelectric microelectromechanical systems (MEMS) have been proven to be an attractive technology for harvesting small magnitudes of energy from ambient vibrations. This technology promises to eliminate the need for ...

Kim, Sang-Gook

384

A piezoelectrically actuated ball valve  

NASA Technical Reports Server (NTRS)

Bimorph strip composed of two layers of poled piezoelectric ceramic material closes and opens valve. Strip performs like capacitator, allowing initial inrush of current when valve is energized and then only small leakage current flows as valve remains energized.

Erwin, L. R.; Schwartz, H. W.; Teitelbaum, B. R.

1972-01-01

385

Piezoelectric Rotary Tube Motor  

NASA Technical Reports Server (NTRS)

A custom rotary SQUIGGLE(Registered TradeMark) motor has been developed that sets new benchmarks for small motor size, high position resolution, and high torque without gear reduction. Its capabilities cannot be achieved with conventional electromagnetic motors. It consists of piezoelectric plates mounted on a square flexible tube. The plates are actuated via voltage waveforms 90 out of phase at the resonant frequency of the device to create rotary motion. The motors were incorporated into a two-axis postioner that was designed for fiber-fed spectroscopy for ground-based and space-based projects. The positioner enables large-scale celestial object surveys to take place in a practical amount of time.

Fisher, Charles D.; Badescu, Mircea; Braun, David F.; Culhane, Robert

2011-01-01

386

Piezoelectric Vibration Damping Study for Rotating Composite Fan Blades  

NASA Technical Reports Server (NTRS)

Resonant vibrations of aircraft engine blades cause blade fatigue problems in engines, which can lead to thicker and aerodynamically lower performing blade designs, increasing engine weight, fuel burn, and maintenance costs. In order to mitigate undesirable blade vibration levels, active piezoelectric vibration control has been investigated, potentially enabling thinner blade designs for higher performing blades and minimizing blade fatigue problems. While the piezoelectric damping idea has been investigated by other researchers over the years, very little study has been done including rotational effects. The present study attempts to fill this void. The particular objectives of this study were: (a) to develop and analyze a multiphysics piezoelectric finite element composite blade model for harmonic forced vibration response analysis coupled with a tuned RLC circuit for rotating engine blade conditions, (b) to validate a numerical model with experimental test data, and (c) to achieve a cost-effective numerical modeling capability which enables simulation of rotating blades within the NASA Glenn Research Center (GRC) Dynamic Spin Rig Facility. A numerical and experimental study for rotating piezoelectric composite subscale fan blades was performed. It was also proved that the proposed numerical method is feasible and effective when applied to the rotating blade base excitation model. The experimental test and multiphysics finite element modeling technique described in this paper show that piezoelectric vibration damping can significantly reduce vibrations of aircraft engine composite fan blades.

Min, James B.; Duffy, Kirsten P.; Choi, Benjamin B.; Provenza, Andrew J.; Kray, Nicholas

2012-01-01

387

Photoacoustic measurement of internal quantum efficiency and observation of the exciton effect in GaSe with photoacoustic phase spectra  

Microsoft Academic Search

We studied the room temperature photoacoustic spectra of GaSe single crystals in the vicinity of the energy gap. Exciton formation was observed in both amplitude and phase spectra. The thermal source that arises in the illuminated sample because of optical absorption without free-carrier generation was incorporated in the heat diffusion equation in order to extend the theoretical approach of photoacoustic

Zoran D. Ristovski; Miroslav D. Dramicanin

1997-01-01

388

Enhanced piezoelectric response in the artificial ferroelectric polymer multilayers  

NASA Astrophysics Data System (ADS)

An actuator with a high piezoelectric response, the ferroelectric polymer multilayer actuator, is described. The ferroelectric polymer multilayers consisting of alternative ferroelectric poly(vinylidene fluoride-trifluoroethylene) (P(VDF-TrFE)) copolymer and relaxor poly(vinylidene fluoride-trifluoroethylene-chlorofloroethylene) (P(VDF-TrFE-CFE)) terpolymer with different periodicities and fixed total thickness are prepared by the Langmuir-Blodgett technique. Both X-ray diffraction and Raman spectroscopic measurements indicate that the structure of the multilayer with thin alternating layer is similar to that of the ferroelectric copolymer. Compared with that of the copolymer, it is found that the piezoelectric coefficient of the multilayer could be improved by 57%. We attributed the enhanced piezoelectric response of the multilayers to the internal electric fields that arises from the electrostatic couplings between different layers.

Zhao, X. L.; Wang, J. L.; Tian, B. B.; Liu, B. L.; Wang, X. D.; Sun, S.; Zou, Y. H.; Lin, T.; Sun, J. L.; Meng, X. J.; Chu, J. H.

2014-12-01

389

Photoacoustic discrimination of vascular and pigmented lesions using classical and Bayesian methods  

NASA Astrophysics Data System (ADS)

Discrimination of pigmented and vascular lesions in skin can be difficult due to factors such as size, subungual location, and the nature of lesions containing both melanin and vascularity. Misdiagnosis may lead to precancerous or cancerous lesions not receiving proper medical care. To aid in the rapid and accurate diagnosis of such pathologies, we develop a photoacoustic system to determine the nature of skin lesions in vivo. By irradiating skin with two laser wavelengths, 422 and 530 nm, we induce photoacoustic responses, and the relative response at these two wavelengths indicates whether the lesion is pigmented or vascular. This response is due to the distinct absorption spectrum of melanin and hemoglobin. In particular, pigmented lesions have ratios of photoacoustic amplitudes of approximately 1.4 to 1 at the two wavelengths, while vascular lesions have ratios of about 4.0 to 1. Furthermore, we consider two statistical methods for conducting classification of lesions: standard multivariate analysis classification techniques and a Bayesian-model-based approach. We study 15 human subjects with eight vascular and seven pigmented lesions. Using the classical method, we achieve a perfect classification rate, while the Bayesian approach has an error rate of 20%.

Swearingen, Jennifer A.; Holan, Scott H.; Feldman, Mary M.; Viator, John A.

2010-01-01

390

Pulsed photoacoustic Doppler flowmetry using time-domain cross-correlation: accuracy, resolution and scalability.  

PubMed

The feasibility of making spatially resolved measurements of blood velocity using a pulsed photoacoustic Doppler technique in acoustic resolution mode has been investigated. Doppler time shifts were quantified via cross-correlation of photoacoustic waveform pairs generated within a blood-simulating phantom using pairs of light pulses. The phantom comprised micron-scale absorbers imprinted on an acetate sheet and moved at known velocities. The photoacoustic waves were detected using PZT ultrasound transducers operating at center frequencies of 20 MHz, 5 MHz and 3.5 MHz; measurements of velocity and resolution were calculated from the mean cross-correlation function of 25 waveform pairs. Velocities in the range ±0.15 to ±1.5 ms(-1) were quantified with accuracies as low as 1%. The transducer focal beam width determines a maximum measurable velocity |V(max)| beyond which correlation is lost due to absorbers moving out of the focal beam between the two laser pulses. Below |V(max)| a measurement resolution of <4% of the measured velocity was achieved. Resolution and |V(max)| can be scaled to much lower velocities such as those encountered in microvasculature (< 50 mms(-1)). The advantage of pulsed rather than continuous-wave excitation is that spatially resolved velocity measurements can be made, offering the prospect of mapping flow within the microcirculation. PMID:22978905

Brunker, Joanna; Beard, Paul

2012-09-01

391

Acoustic attenuation compensation in photoacoustic tomography using time-variant filtering.  

PubMed

Most reconstruction algorithms used in photoacoustic tomography do not account for the effects of acoustic attenuation on the recorded signals. For experimental measurements made in biological tissue, the frequency dependent acoustic attenuation causes high frequency components of the propagating photoacoustic waves to be significantly reduced. This signal loss manifests as a depth dependent magnitude error and blurring of features within the reconstructed image. Here, a general method for compensating for this attenuation using time-variant filtering is presented. The time-variant filter is constructed to correct for acoustic attenuation and dispersion following a frequency power law under the assumption the distribution of attenuation parameters is homogeneous. The filter is then applied directly to the recorded time-domain signals using a form of nonstationary convolution. Regularization is achieved using a time-variant window where the cutoff frequency is based on the local time-frequency distribution of the recorded signals. The approach is computationally efficient and can be used in combination with any detector geometry or reconstruction algorithm. Numerical and experimental examples are presented to illustrate the utility of the technique. Clear improvements in the magnitude and resolution of reconstructed photoacoustic images are seen when acoustic attenuation compensation is applied. PMID:23503580

Treeby, Bradley E

2013-03-01

392

Deconvolution-based deblurring of reconstructed images in photoacoustic/thermoacoustic tomography.  

PubMed

Photoacoustic/thermoacoustic tomography is an emerging hybrid imaging modality combining optical/microwave imaging with ultrasound imaging. Here, a k-wave MATLAB toolbox was used to simulate various configurations of excitation pulse shape, width, transducer types, and target object sizes to see their effect on the photoacoustic/thermoacoustic signals. A numerical blood vessel phantom was also used to demonstrate the effect of various excitation pulse waveforms and pulse widths on the reconstructed images. Reconstructed images were blurred due to the broadening of the pressure waves by the excitation pulse width as well as by the limited transducer bandwidth. The blurring increases with increase in pulse width. A deconvolution approach is presented here with Tikhonov regularization to correct the photoacoustic/thermoacoustic signals, which resulted in improved reconstructed images by reducing the blurring effect. It is observed that the reconstructed images remain unaffected by change in pulse widths or pulse shapes, as well as by the limited bandwidth of the ultrasound detectors after the use of the deconvolution technique. PMID:24322855

Rejesh, Nadaparambil Aravindakshan; Pullagurla, Harish; Pramanik, Manojit

2013-10-01

393

Photoacoustic intra-operative nodal staging using clinically approved superparamagnetic iron oxide nanoparticles  

NASA Astrophysics Data System (ADS)

Detection of tumor metastases in the lymphatic system is essential for accurate staging of various malignancies, however fast, accurate and cost-effective intra-operative evaluation of the nodal status remains difficult to perform with common available medical imaging techniques. In recent years, numerous studies have confirmed the additional value of superparamagnetic iron oxide dispersions (SPIOs) for nodal staging purposes, prompting the clearance of different SPIO dispersions for clinical practice. We evaluate whether a combination of photoacoustic (PA) imaging and a clinically approved SPIO dispersion, could be applied for intra-operative nodal staging. Metastatic adenocarcinoma was inoculated in Copenhagen rats for 5 or 8 days. After SPIO injection, the lymph nodes were photoacoustically imaged both in vivo and ex vivo whereafter imaging results were correlated with MR and histology. Results were compared to a control group without tumor inoculation. In the tumor groups clear irregularities, as small as 1 mm, were observed in the PA contrast pattern of the nodes together with an decrease of PA response. These irregularities could be correlated to the absence of contrast in the MR images and could be linked to metastatic deposits seen in the histological slides. The PA and MR images of the control animals did not show these features. We conclude that the combination of photoacoustic imaging with a clinically approved iron oxide nanoparticle dispersion is able to detect lymph node metastases in an animal model. This approach opens up new possibilities for fast intra-operative nodal staging in a clinical setting.

Grootendorst, Diederik J.; Fratila, Raluca M.; Visscher, Martijn; Ten Haken, Bennie; van Wezel, Richard; Steenbergen, Wiendelt; Manohar, Srirang; Ruers, Theo J. M.

2013-02-01

394

Detection, isolation, and capture of circulating breast cancer cells with photoacoustic flow cytometry  

NASA Astrophysics Data System (ADS)

According to the CDC, breast cancer is the most common cancer and the second leading cause of cancer related deaths among women. Metastasis, or the presence of secondary tumors caused by the spread of cancer cells via the circulatory or lymphatic systems, significantly worsens the prognosis of any breast cancer patient. In this study, a technique is developed to detect circulating breast cancer cells in human blood using a photoacoustic flow cytometry method. A Q-switched laser with a 5 ns pulse at 532 nm is used to interrogate thousands of cells with one pulse as they flow through the beam path. Cells which are pigmented, either naturally or artificially, emit an ultrasound wave as a result of the photoacoustic (PA) effect. Breast cancer cells are targeted with chromophores through immunochemistry in order to provide pigment. After which, the device is calibrated to demonstrate a single-cell detection limit. Cultured breast cancer cells are added to whole blood to reach a biologically relevant concentration of about 25-45 breast cancer cells per 1 mL of blood. An in vitro photoacoustic flow cytometer is used to detect and isolate these cells followed by capture with the use of a micromanipulator. This method can not only be used to determine the disease state of the patient and the response to therapy, it can also be used for genetic testing and in vitro drug trials since the circulating cell can be captured and studied.

Bhattacharyya, Kiran; Njoroge, Martin; Goldschmidt, Benjamin S.; Gaffigan, Brian; Rood, Kyle; Viator, John A.

2013-03-01

395

3-D photoacoustic and pulse echo imaging of prostate tumor progression in the mouse window chamber  

NASA Astrophysics Data System (ADS)

Understanding the tumor microenvironment is critical to characterizing how cancers operate and predicting their response to treatment. We describe a novel, high-resolution coregistered photoacoustic (PA) and pulse echo (PE) ultrasound system used to image the tumor microenvironment. Compared to traditional optical systems, the platform provides complementary contrast and important depth information. Three mice are implanted with a dorsal skin flap window chamber and injected with PC-3 prostate tumor cells transfected with green fluorescent protein. The ensuing tumor invasion is mapped during three weeks or more using simultaneous PA and PE imaging at 25 MHz, combined with optical and fluorescent techniques. Pulse echo imaging provides details of tumor structure and the surrounding environment with 100-?m3 resolution. Tumor size increases dramatically with an average volumetric growth rate of 5.35 mm3/day, correlating well with 2-D fluorescent imaging (R = 0.97, p < 0.01). Photoacoustic imaging is able to track the underlying vascular network and identify hemorrhaging, while PA spectroscopy helps classify blood vessels according to their optical absorption spectrum, suggesting variation in blood oxygen saturation. Photoacoustic and PE imaging are safe, translational modalities that provide enhanced depth resolution and complementary contrast to track the tumor microenvironment, evaluate new cancer therapies, and develop molecular contrast agents in vivo.

Bauer, Daniel R.; Olafsson, Ragnar; Montilla, Leonardo G.; Witte, Russell S.

2011-02-01

396

Ultrasound and photoacoustic imaging to monitor mesenchymal stem cells labeled with gold nanoparticles  

NASA Astrophysics Data System (ADS)

Mesenchymal stem cells (MSCs) are versatile in many tissue engineering applications and have the potential to be used for cellular therapies because they can differentiate into many cell types. Specifically, the use of MSCs for the treatment of ischemic disease is promising because MSCs can express characteristics of vascular cells. MSCs can promote vascular growth at the site of injury after delivery using a PEGylated fibrin gel. In order to quantitatively assess in vivo delivery and differentiation of MSCs, a non-invasive and high-resolution imaging technique is required. In this study, the combined ultrasound and photoacoustic imaging was demonstrated to monitor MSCs labeled with citrate-stabilized gold nanoparticles (Au NPs). It was observed that uptake of nanoparticles did not have a significant effect on cell viability and proliferation over a two-week period. Four different cell concentrations of either the non-labeled MSCs or the Au NP labeled MSCs were embedded in the tissue mimicking gelatin phantom. The ultrasound and photoacoustic signals were acquired and quantitatively analyzed to assess sensitivity and accuracy of the developed imaging approach. Furthermore, based on the results, the feasibility of in vivo ultrasound and photoacoustic imaging of MSCs was discussed.

Nam, Seung Yun; Ricles, Laura M.; Sokolov, Konstantin; Suggs, Laura J.; Emelianov, Stanislav Y.

2011-03-01

397

3-D photoacoustic and pulse echo imaging of prostate tumor progression in the mouse window chamber  

PubMed Central

Understanding the tumor microenvironment is critical to characterizing how cancers operate and predicting their response to treatment. We describe a novel, high-resolution coregistered photoacoustic (PA) and pulse echo (PE) ultrasound system used to image the tumor microenvironment. Compared to traditional optical systems, the platform provides complementary contrast and important depth information. Three mice are implanted with a dorsal skin flap window chamber and injected with PC-3 prostate tumor cells transfected with green fluorescent protein. The ensuing tumor invasion is mapped during three weeks or more using simultaneous PA and PE imaging at 25 MHz, combined with optical and fluorescent techniques. Pulse echo imaging provides details of tumor structure and the surrounding environment with 100-?m3 resolution. Tumor size increases dramatically with an average volumetric growth rate of 5.35 mm3?day, correlating well with 2-D fluorescent imaging (R = 0.97, p < 0.01). Photoacoustic imaging is able to track the underlying vascular network and identify hemorrhaging, while PA spectroscopy helps classify blood vessels according to their optical absorption spectrum, suggesting variation in blood oxygen saturation. Photoacoustic and PE imaging are safe, translational modalities that provide enhanced depth resolution and complementary contrast to track the tumor microenvironment, evaluate new cancer therapies, and develop molecular contrast agents in vivo. PMID:21361696

Bauer, Daniel R.; Olafsson, Ragnar; Montilla, Leonardo G.; Witte, Russell S.

2011-01-01

398

Photoimprint Photoacoustic Microscopy for Three-Dimensional Label-Free Subdiffraction Imaging  

NASA Astrophysics Data System (ADS)

Subdiffraction optical microscopy allows the imaging of cellular and subcellular structures with a resolution finer than the diffraction limit. Here, combining the absorption-based photoacoustic effect and intensity-dependent photobleaching effect, we demonstrate a simple method for subdiffraction photoacoustic imaging of both fluorescent and nonfluorescent samples. Our method is based on a double-excitation process, where the first excitation pulse partially and inhomogeneously bleaches the molecules in the diffraction-limited excitation volume, thus biasing the signal contributions from a second excitation pulse striking the same region. The differential signal between the two excitations preserves the signal contribution mostly from the center of the excitation volume, and dramatically sharpens the lateral resolution. Moreover, due to the nonlinear nature of the signal, our method offers an inherent optical sectioning capability, which is lacking in conventional photoacoustic microscopy. By scanning the excitation beam, we performed three-dimensional subdiffraction imaging of varied fluorescent and nonfluorescent species. As any molecules have absorption, this technique has the potential to enable label-free subdiffraction imaging, and can be transferred to other optical imaging modalities or combined with other subdiffraction methods.

Yao, Junjie; Wang, Lidai; Li, Chiye; Zhang, Chi; Wang, Lihong V.

2014-01-01

399

Photoimprint photoacoustic microscopy for three-dimensional label-free subdiffraction imaging.  

PubMed

Subdiffraction optical microscopy allows the imaging of cellular and subcellular structures with a resolution finer than the diffraction limit. Here, combining the absorption-based photoacoustic effect and intensity-dependent photobleaching effect, we demonstrate a simple method for subdiffraction photoacoustic imaging of both fluorescent and nonfluorescent samples. Our method is based on a double-excitation process, where the first excitation pulse partially and inhomogeneously bleaches the molecules in the diffraction-limited excitation volume, thus biasing the signal contributions from a second excitation pulse striking the same region. The differential signal between the two excitations preserves the signal contribution mostly from the center of the excitation volume, and dramatically sharpens the lateral resolution. Moreover, due to the nonlinear nature of the signal, our method offers an inherent optical sectioning capability, which is lacking in conventional photoacoustic microscopy. By scanning the excitation beam, we performed three-dimensional subdiffraction imaging of varied fluorescent and nonfluorescent species. As any molecules have absorption, this technique has the potential to enable label-free subdiffraction imaging, and can be transferred to other optical imaging modalities or combined with other subdiffraction methods. PMID:24483902

Yao, Junjie; Wang, Lidai; Li, Chiye; Zhang, Chi; Wang, Lihong V

2014-01-10

400

Simulations of thermally induced photoacoustic wave propagation using a pseudospectral time-domain method.  

PubMed

Most physical models used to evaluate thermally induced photoacoustic waves in biomedical applications are approximations based on assumptions necessary to obtain analytical results, such as thermal and stress confinements. In contrast, using numerical methods to solve the general photoacoustic wave equations gives detailed information on the wave phenomenon without requiring as many assumptions to be made. The photoacoustic wave generated by thermal expansion is characterized by the heat conduction theorem and the state, continuity, and Navier-Stokes equations. This study developed a numerical solution in axis-symmetric cylindrical coordinates using a pseudospectral time-domain scheme. The method is efficient for large-scale simulations since it requires only 2 grid points per minimum wavelength, in contrast to conventional methods such as the finite-difference time-domain method requiring at least 10-20 grid points. The numerical techniques included Berenger's perfectly matched layers for free wave simulations, and a linear-perturbation analytical solution was used to validate the simulation results. The numerical results obtained using 4 grid points per minimum wavelength in the simulation domain agreed with the theoretical estimates to within an absolute difference error of 3.87 x 10(-2) for a detection distance of 3.1 mm. PMID:19473928

Sheu, Yae-Lin; Li, Pai-Chi

2009-05-01

401

Wide-field two-dimensional multifocal optical-resolution photoacoustic computed microscopy  

PubMed Central

Optical-resolution photoacoustic microscopy (OR-PAM) is an emerging technique that directly images optical absorption in tissue at high spatial resolution. To date, the majority of OR-PAM systems are based on single focused optical excitation and ultrasonic detection, limiting the wide-field imaging speed. While one-dimensional multifocal OR-PAM (1D-MFOR-PAM) has been developed, the potential of microlens and transducer arrays has not been fully realized. Here, we present the development of two-dimensional multifocal optical-resolution photoacoustic computed microscopy (2D-MFOR-PACM), using a 2D microlens array and a full-ring ultrasonic transducer array. The 10 × 10 mm2 microlens array generates 1800 optical foci within the focal plane of the 512-element transducer array, and raster scanning the microlens array yields optical-resolution photoacoustic images. The system has improved the in-plane resolution of a full-ring transducer array from ?100 µm to 29 µm and achieved an imaging time of 36 seconds over a 10 × 10 mm2 field of view. In comparison, the 1D-MFOR-PAM would take more than 4 minutes to image over the same field of view. The imaging capability of the system was demonstrated on phantoms and animals both ex vivo and in vivo. PMID:24322226

Xia, Jun; Li, Guo; Wang, Lidai; Nasiriavanaki, Mohammadreza; Maslov, Konstantin; Engelbach, John A.; Garbow, Joel R.; Wang, Lihong V.

2014-01-01

402

The piezoelectric sorption technique: a practical method  

E-print Network

resonance point. When mass is added to the surface of the quartz crystal, the series resonance frequency changes by an amount related to the amount of mass added. The proportionality constant depends on the crystal properties. Sauerbrey (1959) first... commercially available QCM to measure the adsorption and desorption of water. Their results were consistent with existing theory. Mecca and Bucur (1980) used a QCMSD for dynamic sorption studies. They used a single crystal to determine mass changes. King...

Flipse, Eugene Charles

2012-06-07

403

Influence of nanoscale temperature rises on photoacoustic generation: discrimination between optical absorbers based on nonlinear photoacoustics at high frequency  

E-print Network

In the thermoelastic regime, photoacoustic sensing of optical absorption relies on conversion from light to acoustic energy via the coefficient of thermal expansion \\beta. In this work, we confront confront experimental measurements to theoretical predictions of nonlinear photoacoustic generation based on the dynamic variation of \\beta(T) during the optical excitation of absorbers in aqueous solution. The photoacoustic generation from solutions of organic dye and gold nanospheres (with same optical densities), illuminated with 532 nm nanosecond pulses, was detected using a high frequency ultrasound transducer (center frequency 20 MHz). Photoacoustic emission was observed with gold nanospheres at low fluence (a few mJ/cm2) for an equilibrium temperature around 4{\\deg}C, where the linear photoacoustic effect in water vanishes, highlighting the nonlinear emission from the solution of nanospheres. Under the same condition, no emission was observed with the absorbing organic dye. At a fixed fluence of 5 mJ/cm2, th...

Simandoux, Oliver; Gâteau, Jérôme; Bossy, Emmanuel

2013-01-01

404

Observation of FT-IR/photoacoustic and FT-IR/photoacoustic reflection-absorption spectra of Langmuir-Blodgett films on a metal substrate  

SciTech Connect

Fourier transform infrared photoacoustic (FT-IR/PA) spectroscopy combined with the reflection-absorption (RA) technique is demonstrated for Langmuir-Blodgett (LB) films deposited on metal substrate FT-IR/PA and FT-IR/PA/RA spectra can be taken on the same LB film. By the use of FT-IR/PA and FT-IR/PA/RA methods. Spectra corresponding to transmission and RA spectra can bee identified for the same LB film on a metal substrate. The molecular orientation of the LB film can be analyzed with the use of these spectra.

Ochiai, S.; McClelland, J.F. (Ames Laboratory-USDOE, Iowa State University, Ames, Iowa 50011-3020 (United States)); Kobayashi, K.; Takaoka, K. (Department of Chemistry, Musashi Institute of Technology, Setagaya-ku, Tokyo 158 (Japan))

1994-10-01

405

Piezoelectric activity in Perovskite ferroelectric crystals.  

PubMed

Perovskite ferroelectrics (PFs) have been the dominant piezoelectric materials for various electromechanical applications, such as ultrasonic transducers, sensors, and actuators, to name a few. In this review article, the development of PF crystals is introduced, focusing on the crystal growth and piezoelectric activity. The critical factors responsible for the high piezoelectric activity of PFs (i.e., phase transition, monoclinic phase, domain size, relaxor component, dopants, and piezoelectric anisotropy) are surveyed and discussed. A general picture of the present understanding on the high piezoelectricity of PFs is described. At the end of this review, potential approaches to further improve the piezoelectricity of PFs are proposed. PMID:25585387

Li, Fei; Wang, Linghang; Jin, Li; Lin, Dabin; Li, Jinglei; Li, Zhenrong; Xu, Zhuo; Zhang, Shujun

2015-01-01

406

Effect of thermal nonlinearity in high-absorption media on the parameters of the photoacoustic signal detected by the gas microphone method: The fundamental and second harmonics  

NASA Astrophysics Data System (ADS)

A perturbation theory is put forward that describes the effect of thermal nonlinearity due to the temperature dependence of the thermophysical parameters of high-absorption systems with a low thermal conductivity on the parameters of the photoacoustic signal detected by the gas microphone technique. It is found that the dependence of the photoacoustic signal amplitude on incident beam intensity I 0 stems from the dependence of the illuminated surface temperature on I 0. This dependence is a complicated function instead of being a simple quadratic function as was expected. In the limiting cases (?s? ? 1 and ?s? ? 1), this contribution to the photoacoustic signal amplitude is described by simple expressions, which are convenient for determining the thermal coefficients of the thermophysical parameters of the medium. It is found that the thermal nonlinearity significantly affects the photoacoustic signal phase in the frequency region meeting the condition ?s? ˜ 1. In the above limiting cases, its effect is insignificant. A theory of generation of the photoacoustic signal second harmonic is proposed. The second harmonic is related to the temperature dependence of the thermophysical parameters of the buffer gas and sample. It is shown that the amplitude of the signal is a quadratic function of the incident beam intensity and varies with its frequency as ?-3/2 for ?s? ? 1 and ?-5/2 for ?s? ? 1.

Madvaliev, U.; Salikhov, T. Kh.; Sharifov, D. M.

2006-06-01

407

Bulk-wave and guided-wave photoacoustic evaluation of the mechanical properties of aluminum/silicon nitride double-layer thin films.  

PubMed

The development of devices made of micro- and nano-structured thin film materials has resulted in the need for advanced measurement techniques to characterize their mechanical properties. Photoacoustic techniques, which use pulsed laser irradiation to nondestructively induce very high frequency ultrasound in a test object via rapid thermal expansion, are suitable for nondestructive and non-contact evaluation of thin films. In this paper, we compare two photoacoustic techniques to characterize the mechanical parameters of edge-supported aluminum and silicon nitride double-layer thin films. The elastic properties and residual stresses in such films affect their mechanical performance. In a first set of experiments, a femtosecond transient pump-probe technique is used to investigate the Young's moduli of the aluminum and silicon nitride layers by launching ultra-high frequency bulk acoustic waves in the films. The measured transient signals are compared with simulated transient thermoelastic signals in multi-layer structures, and the elastic moduli are determined. Independent pump-probe tests on silicon substrate-supported region and unsupported region are in good agreement. In a second set of experiments, dispersion curves of the A(0) mode of the Lamb waves that propagate along the unsupported films are measured using a broadband photoacoustic guided-wave method. The residual stresses and flexural rigidities for the same set of double-layer membranes are determined from these dispersion curves. Comparisons of the results obtained by the two photoacoustic techniques are made and discussed. PMID:16899268

Zhang, Feifei; Krishnaswamy, Sridhar; Lilley, Carmen M

2006-12-01

408

Self-powered discrete time piezoelectric vibration damper  

NASA Astrophysics Data System (ADS)

Structural vibration suppression is of great interest to the aircraft industry as it can reduce the amplitude of excessive vibration in lightly damped panels caused by conditions in their operational environment. One technique of suppressing vibration is to use passive damping techniques such as constrained layered damping incorporating viscoelastic materials. However these techniques may not be acceptable because of weight concerns or extreme temperature variations. Over the past decade much work has been done by researchers on the use of piezoelectric ceramic devices, using passive and active techniques, for structural vibration suppression. The passive piezoelectric damping devices consist of a piezoelectric element and either a resistive or resonant shunt. The resonant circuit shunt, which is analogous to a mechanical vibration absorber, gives better vibration reduction compared to the resistor shunt. This device requires a large value of inductance in order to be tuned to a particular structural vibration mode. A large value inductor can be made by a using a gyrator type circuit however the circuit needs external power. A method of vibration control using a discrete time controller and piezoelectric devices is presented. That is, this paper describes the concept of a self-powered discrete time piezoelectric vibration damper which does not need tuning to the structural resonant frequency and is powered by piezoelectric elements, i.e. does not need an external power supply. This device is referred to as a strain amplitude minimization patch (STAMP) damper. A brief description of the theory used and of the scheme is presented. Also the operation of this device is compared with other 'passive' techniques, involving piezoelectric elements, such as the resistive passive damper and the parallel resonant passive damper cases. Experimental results presented, on a cantilevered beam, demonstrate the concept and show that the device, even in its current underdeveloped form, has better damping than the simple resistor damper. Measurements taken indicate that the maximum RMS tip accelerations, at resonance, are reduced by 17.3%, 62.7% and 39.5% for the resistor, parallel resonant and STAMP damper devices, respectively, when compared to the short circuit reference condition. The performance of each device is observed when the resonant frequency of the system changes when a mass is added to the tip of the cantilever. This paper also discusses areas where improvements in the performance of the STAMP damper can be achieved.

Konak, Michael J.; Powlesland, Ian G.; van der Velden, Stephen P.; Galea, Stephen C.

1997-11-01

409

Growth and characterization of lanthanum gallium silicate La 3Ga 5SiO 14 single crystals for piezoelectric applications  

Microsoft Academic Search

We have successfully grown a new piezoelectric La3Ga5SiO14 (LGS) single crystal, with dimensions of 1 or 2 inch in diameter, using the Czochralski technique. Coloring of the grown crystals was discussed. The device properties of LGS resonators and filters were demonstrated. The LGS single crystal showed superior properties for piezoelectric applications.

Kiyoshi Shimamura; Hiroaki Takeda; Takuya Kohno; Tsuguo Fukuda

1996-01-01

410

Piezoelectrically Initiated Pyrotechnic Igniter  

NASA Technical Reports Server (NTRS)

This innovation consists of a pyrotechnic initiator and piezoelectric initiation system. The device will be capable of being initiated mechanically; resisting initiation by EMF, RF, and EMI (electromagnetic field, radio frequency, and electromagnetic interference, respectively); and initiating in water environments and space environments. Current devices of this nature are initiated by the mechanical action of a firing pin against a primer. Primers historically are prone to failure. These failures are commonly known as misfires or hang-fires. In many cases, the primer shows the dent where the firing pin struck the primer, but the primer failed to fire. In devices such as "T" handles, which are commonly used to initiate the blowout of canopies, loss of function of the device may result in loss of crew. In devices such as flares or smoke generators, failure can result in failure to spot a downed pilot. The piezoelectrically initiated ignition system consists of a pyrotechnic device that plugs into a mechanical system (activator), which on activation, generates a high-voltage spark. The activator, when released, will strike a stack of electrically linked piezo crystals, generating a high-voltage, low-amperage current that is then conducted to the pyro-initiator. Within the initiator, an electrode releases a spark that passes through a pyrotechnic first-fire mixture, causing it to combust. The combustion of the first-fire initiates a primary pyrotechnic or explosive powder. If used in a "T" handle, the primary would ramp the speed of burn up to the speed of sound, generating a shock wave that would cause a high explosive to go "high order." In a flare or smoke generator, the secondary would produce the heat necessary to ignite the pyrotechnic mixture. The piezo activator subsystem is redundant in that a second stack of crystals would be struck at the same time with the same activation force, doubling the probability of a first strike spark generation. If the first activation fails to ignite, the device is capable of multiple attempts. Another unique aspect is in the design of the pyrotechnic device. There is an electrode that aids the generation of a directed spark and the use of a conductive matrix to support the first-fire material so that the spark will penetrate to the second electrode.

Quince, Asia; Dutton, Maureen; Hicks, Robert; Burnham, Karen

2013-01-01

411

Dedicated 3D photoacoustic breast imaging  

PubMed Central

Purpose: To report the design and imaging methodology of a photoacoustic scanner dedicated to imaging hemoglobin distribution throughout a human breast. Methods: The authors developed a dedicated breast photoacoustic mammography (PAM) system using a spherical detector aperture based on our previous photoacoustic tomography scanner. The system uses 512 detectors with rectilinear scanning. The scan shape is a spiral pattern whose radius varies from 24 to 96 mm, thereby allowing a field of view that accommodates a wide range of breast sizes. The authors measured the contrast-to-noise ratio (CNR) using a target comprised of 1-mm dots printed on clear plastic. Each dot absorption coefficient was approximately the same as a 1-mm thickness of whole blood at 756 nm, the output wavelength of the Alexandrite laser used by this imaging system. The target was immersed in varying depths of an 8% solution of stock Liposyn II-20%, which mimics the attenuation of breast tissue (1.1 cm?1). The spatial resolution was measured using a 6 ?m-diameter carbon fiber embedded in agar. The breasts of four healthy female volunteers, spanning a range of breast size from a brassiere C cup to a DD cup, were imaged using a 96-mm spiral protocol. Results: The CNR target was clearly visualized to a depth of 53 mm. Spatial resolution, which was estimated from the full width at half-maximum of a profile across the PAM image of a carbon fiber, was 0.42 mm. In the four human volunteers, the vasculature was well visualized throughout the breast tissue, including to the chest wall. Conclusions: CNR, lateral field-of-view and penetration depth of our dedicated PAM scanning system is sufficient to image breasts as large as 1335 mL, which should accommodate up to 90% of the women in the United States. PMID:24320471

Kruger, Robert A.; Kuzmiak, Cherie M.; Lam, Richard B.; Reinecke, Daniel R.; Del Rio, Stephen P.; Steed, Doreen

2013-01-01

412

Considering sources and detectors distributions for quantitative photoacoustic tomography  

PubMed Central

Photoacoustic tomography (PAT) is a hybrid imaging modality that takes advantage of high optical contrast brought by optical imaging and high spatial resolution brought by ultrasound imaging. However, the quantification in photoacoustic imaging is challenging. Multiple optical illumination approach has proven to achieve uncoupling of diffusion and absorption effects. In this paper, this protocol is adopted and synthetic photoacoustic data, blurred with some noise, were generated. The influence of the distribution of optical sources and transducers on the reconstruction of the absorption and diffusion coefficients maps is studied. Specific situations with limited view angles were examined. The results show multiple illuminations with a wide field improve the reconstructions. PMID:25426322

Song, Ningning; Deumié, Carole; Da Silva, Anabela

2014-01-01

413

A simulation study on photoacoustic signals from red blood cells.  

PubMed

A two dimensional simulation study was performed to investigate the photoacoustic signal properties of non-aggregated and aggregated erythrocytes. Spatial distributions of non-aggregated blood samples were generated by employing a Monte Carlo method and aggregated blood samples were simulated using a hexagonal packing scheme. For the non-aggregating case photoacoustic signals demonstrated a monotonic rise with hematocrit. For the aggregating case it was found that spectral (<20 MHz) intensity increased (11 dB at 15.6 MHz) when the aggregate size increased. This study strongly suggests that the assessment of erythrocyte aggregation level in human blood might be possible by using a photoacoustic spectroscopic method. PMID:21568396

Saha, Ratan K; Kolios, Michael C

2011-05-01

414

Photoacoustic tomography of water in phantoms and tissue.  

PubMed

Photoacoustic tomography (PAT) has been widely used to image optically absorptive objects in both human and animal tissues. For the first time, we present imaging of water with laser-based PAT. We photoacoustically measure the absorption spectra of water-ethanol mixtures at various water concentrations, and then image water-ethanol and pure-water inclusions in gel and a water inclusion in fat tissue. The significant difference in photoacoustic signals between water and fat tissue indicates that the laser-based PAT has the potential to detect water content in tissue. PMID:20615021

Xu, Zhun; Li, Changhui; Wang, Lihong V

2010-01-01

415

Determination of nitrogen dioxide by visible photoacoustic spectroscopy  

SciTech Connect

Visible, photoacoustic spectroscopy, performed with a CW krypton laser, is applied to the quantitative detection of NO/sub 2/ in air samples at total pressures of 1 atm. The optimization of the photoacoustic signal in accord with a theoretical model is discussed and a dual beam (sample signal minus reference signal) method of reducing the backyard noise level is described. Data were obtained by using two cell designs and two types of microphones. NO/sub 2/ concentrations as small as 2 ppB were detected, and the photoacoustic signal was linearily dependent on NO/sub 2/ pressure over approximately 6 orders of magnitude.

Poizat, O.; Atkinson, G.H.

1982-08-01

416

Wideband piezoelectric pressure transducer  

NASA Astrophysics Data System (ADS)

A piezoelectric pressure transducer for pressures of up to 100 MPa was developed, with an operating frequency range from 100 Hz to 1 MHz on the electrical side - sufficiently wide to reproduce pressure profiles of arc discharges with microsecond rise times and millisecond fall times. The sensing element is a disk of TsTS-19 piezoceramic material, 1 mm thick and 5 mm in diameter. It is thermally and electrically insulated from the arc plasma by a compound transmission rod consisting of two quartz crystals 5 mm in diameter and freely sliding inside a teflon sleeve. The 50 mm long waveguide for absorbing acoustic vibrations and thus separating the valid signal from the reflected one consists of brass wires acoustically insulated with epoxy resin and encapsulated into a textolite sleeve with epoxy resin at the other end. A copper housing shields the transducer from electromagnetic interference. The transducer output signal passes through a matching circuit and then a high-impedance voltage divider to a differential amplifier, the latter being shunted by a stabilizing low 1 Mohm resistance at the input. A special feature of this transducer is low-frequency compensation by means of a corrective RC-circuit. After calibration of oscillograms, the transducer has a sensitivity of 1 V/MPa over the 10(-2) to 10 MPa range. Its resolution corresponds to the 2 microsecond maximum rise time of its output signal, with the sensing element located at the end of a shock tube.

Godonyuk, V. A.; Zhuravlev, B. V.; Shedko, I. P.

1986-02-01

417

Integrated wireless piezoelectric sensors  

NASA Astrophysics Data System (ADS)

Piezoelectric sensor arrays and sensor networks have been suggested as a means to monitor the integrity of composite structures throughout the service life for instance of an aircraft. Complex sensor systems will require significant additional expenditures with respect to cabling and electronics, with the added weight and effort possibly outweighing any benefits. Sensor positions in remote locations of an aircraft will often necessitate accessibility to these locations for maintenance purposes. For these reasons wireless, integrated sensors have recently become an object of increasing interest. Within the framework of a feasibility study various aspects of integrated wireless sensor system were investigated in detail. Particular emphasis was thereby laid on issues that are essential form a practical point of view, but that have not been discussed in the literature extensively. As a starting point a trade-off study between different sensor network configurations was conducted, form passive, remotely queried senors without power supply to fully functional active sensor pads with integrated power supply and electronics. Various concepts for the on-board energy supply of remotely queried sensor pads were studied and a comparison between rechargeable, and single-use batteries was performed. The suitability of different electronic components for integration into carbon fiber composites was investigated with particular emphasis on their survivability under typical temperature cycles experienced in autoclave runs. Finally, a crackwire sensor as an example of a passive remotely queried sensor system was pursued further in order to show the feasibility of such a wireless system for composite health monitoring purposes.

Ihler, Elmar; Zaglauer, Helmut W.; Herold-Schmidt, Ursula; Dittrich, Kay W.; Wiesbeck, Werner

2000-06-01

418

Testing fruit quality by photoacoustic spectroscopy assay  

NASA Astrophysics Data System (ADS)

This study was conducted with the aim of testing the hypothesis that raspberry and strawberry fruits from nonorganic farming release more ethylene gas compounds compared to organic ones. At the same time, the experiments focused on evaluation of the potential and capabilities of the laser photoacoustic spectroscopy (LPAS) method in the assessment of fruit quality related to the effects of nitrogen. Ethylene gas can be harmful and carcinogenic, because it can accelerate the natural ripening process of physiologically mature fruits and makes the fruits more consistent in size. With the advantages of LPAS, we demonstrate that the concentration of ethylene from nonorganic raspberry and strawberry fruits is greater than from organic ones.

Popa, C.; Dumitras, D. C.; Patachia, M.; Banita, S.

2014-10-01

419

Thermally stable dynamic piezoelectricity in sandwich films of porous and nonporous amorphous fluoropolymer  

NASA Astrophysics Data System (ADS)

Porous amorphous fluoropolymer films of very low stiffness were produced by a solvent evaporation technique. Corona-charged sandwich films consisting of a porous and a nonporous layer exhibit piezoelectric thickness-extension resonances in their dielectric spectrum, through which the temperature dependence of their dynamic stiffness, coupling factor, and piezoelectric coefficient could be determined. Their strong piezoelectricity with coefficients of up to 600 pC/N at temperatures of at least 120 °C could make these polymer electret films interesting candidates for sensor and actuator applications in elevated temperature environments.

Mellinger, Axel; Wegener, Michael; Wirges, Werner; Gerhard-Multhaupt, Reimund

2001-09-01

420

Design of Multi-phase Piezoelectric Actuators  

Microsoft Academic Search

A new multi-objective topology optimization method is proposed in this study for systematic design of multi-phase piezoelectric actuators. The actuator under consideration is composed of a compliant host structure equipped with piezoelectric elements, where the host structure serves as a compliant amplifier to enlarge the small stroke output generated by the actuation force of piezoelectric materials. In the context of

Zhen Luo; Wei Gao; Chongmin Song

2010-01-01

421

Power Electronics Design Choice for Piezoelectric Microrobots  

E-print Network

. INTRODUCTION Piezoelectric actuators, both stack and cantilever type, have become increasingly popular srinath ronf} @eecs.berkeley.edu Abstract-- Piezoelectric actuators are advantageous for mi- crorobots due of integration. However, the main disadvantage of either stack or cantilever piezoelectric actuators are the high

Fearing, Ron

422

Polymer Piezoelectric Transducers for Ultrasonic NDE  

NASA Technical Reports Server (NTRS)

Piezoelectric polymers are associated with a low noise and inherent damping that makes them very effective receivers as well as broadband transmitters for high frequencies tasks. This paper reviews polymer piezoelectric materials, the origin of their piezoelectric behavior and their applications to ultrasonic NDE.

Bar-Cohen, Yoseph; Xue, Tianji; Lih, Shyh-Shiuh

1996-01-01

423

Thermal Image of Coffee-Seed Germ Obtained by Photoacoustic Microscopy  

NASA Astrophysics Data System (ADS)

Photoacoustic microscopy (PAM) has been shown to be a suitable technique to obtain thermal images of a wide variety of samples from semiconductors to biological material. In PAM, the incidence of a modulated laser beam on a sample within a photoacoustic (PA) cell, hermetically sealed, produces a PA signal which depends on the thermal and optical properties of the studied sample. By making a sweep of the modulated laser beam on the sample surface, it is possible to obtain the PA signal as a function of their x- y coordinates, and from this signal, it is possible to reconstruct thermal images of the sample. In this study, thermal images of a coffee-seed germ were obtained, with a difference of 12 h between them, by using the PAM technique. Thermal differences observed between images give information which reflects degradation due to the fact that germ cells undergo changes as a function of time. The thermal images obtained by the PAM technique could be applied to biological materials that have a complex constitution (not homogeneous) in their structures, and thermal differences can be observed. PAM is a non-destructive technique, which is an important feature for this type of study. Other applications of this technique can be performed in the agricultural and biotechnological areas.

Domínguez-Pacheco, A.; Hernández Aguilar, C.; Cruz-Orea, Alfredo; Isaac Alemán, E.; Martínez Ortiz, E.

2013-09-01

424

Influence of the Surface Mechanical Treatment on the Photothermal Piezoelectric Spectra of ZnSe Crystals  

NASA Astrophysics Data System (ADS)

This paper presents experimental and theoretical piezoelectric photoacoustic spectra of ZnSe samples after different surface treatments: grinding, polishing, and etching. The modification of the Jackson and Amer theory, presented in the paper, enabled numerical interpretation of the spectra in the model of a mechanically damaged surface layer. The nature of the characteristic peak observed at E = 2.65 eV below the energy gap is explained as caused by the Urbach absorption tail and the damaged surface layer of a sample. The correlation between the microhardness of the Zn1- x Be x Se and ZnSe crystals and the thickness of the mechanically damaged surface layer was observed.

Zakrzewski, J.; Mali?ski, M.; Strza?kowski, K.

2012-07-01

425

Photoacoustic measurement of internal quantum efficiency and observation of the exciton effect in GaSe with photoacoustic phase spectra.  

PubMed

We studied the room temperature photoacoustic spectra of GaSe single crystals in the vicinity of the energy gap. Exciton formation was observed in both amplitude and phase spectra. The thermal source that arises in the illuminated sample because of optical absorption without free-carrier generation was incorporated in the heat diffusion equation in order to extend the theoretical approach of photoacoustic signal generation. We calculated the optical absorption coefficient, which shows the exciton formation, and the electron-hole generation quantum efficiency eta(G) using an extended model from the phase and amplitude photoacoustic spectra, respectively. PMID:18250722

Ristovski, Z D; Dramí?anin, M D

1997-01-20

426

Piezoelectricity and electrostriction in biocompatible (Na,K)NbO3 nanofiber scaffolds  

NASA Astrophysics Data System (ADS)

Single phase and highly crystalline biocompatible ferroelectric (Na,K)NbO3 (NKN) nanofibers were synthesized by sol-gel assisted electrospinning technique. Low amplitude piezoelectric response as well as electrostriction effect in NKN fibers were examined using piezoelectric force microscopy technique. Piezoelectric coefficient d33 is strongly anisotropic varying from 75.8 to 18.3 pm/V for, respectively, out-of-axis and on-axis oriented ferroelectric domains in NKN fibers. Hysteresis P-E loop for individual nanofiber reconstructed from the bipolar E-field-induced butterfly strain curve yields: coercive field Ec = 31 kV/cm, remnant Pr = 6.2 ?C/cm2, and the maximum achieved polarization Pmax = 21.2 ?C/cm2. Enhanced piezoelectric effect and strong electrostriction promise NKN fibers as electrically polarizable scaffolds for tissue engineering and for energy harvesting biocompatible nanogenerators.

Jalalian, A.; Grishin, A. M.

2014-06-01

427

[Tunable fiber laser based photoacoustic spectroscopy for acetylene detection].  

PubMed

An acetylene detection system has been constructed with a tunable erbium-doped fiber laser (TEDFL) based photoacoustic spectrometer. Combining wavelength modulation and second harmonic signal detection technique, the system is able to effectively eliminate the background noise generated by absorption of the cell windows and the wall of the acoustic resonator. The system was applied to low concentration acetylene flowing measurement, through optimizing the systemic optics, acoustics and electron detection technique condition. The experimental results show that the second harmonic amplitude is directly proportional to gas concentration. Their linear pertinence coefficient is 0.999 53. The system sensitivity limit for acetylene detection is 0.3 ppm under atmosphere pressure with 100 ms time constant and 3. 5 mW average optical power. The TEDFL was used as light source in stead of the DFB diode laser which is relatively costly. The system appears promising as a basis for developing cheap, practical, portable spectroscopy instruments for trace gas detection. The detection sensitivity could be greatly improved by using multi-path cell or increasing the laser power with EDFA. PMID:19839300

Peng, Yong; Yu, Qing-Xu

2009-08-01

428

Total internal reflection photoacoustic spectroscopy for the detection of ?-hematin  

NASA Astrophysics Data System (ADS)

Evanescent field sensing methods are currently used to detect many different types of disease markers and biologically important chemicals such as the HER2 breast cancer receptor. Hinoue et al. used Total Internal Reflection Photoacoustic Spectroscopy (TIRPAS) as a method of using the evanescent field to detect an optically opaque dye at a sample interface. Although their methods were successful at detecting dyes, the results at that time did not show a very practical spectroscopic technique, which was due to the less than typical sensitivity of TIRPAS as a spectroscopy modality given the low power (~1 to 2 W) lasers being used. Contrarily, we have used an Nd:YAG laser with a five nanosecond pulse that gives peak power of 1 MW coupled with the TIRPAS system to increase the sensitivity of this technique for biological material sensing. All efforts were focused on the eventual detection of the optically absorbing material, hemozoin, which is created as a byproduct of a malarial infection in blood. We used an optically analogous material, ?-hematin, to determine the potential for detection in the TIRPAS system. In addition, four properties which control the sensitivity were investigated to increase understanding about the sensor's function as a biosensing method.

Goldschmidt, Benjamin S.; Sudduth, Amanda S. M.; Samson, Edward B.; Whiteside, Paul J. D.; Bhattacharyya, Kiran D.; Viator, John A.

2012-06-01

429

Total internal reflection photoacoustic spectroscopy for the detection of ?-hematin  

PubMed Central

Abstract. Evanescent field sensing methods are currently used to detect many different types of disease markers and biologically important chemicals such as the HER2 breast cancer receptor. Hinoue et al. used Total Internal Reflection Photoacoustic Spectroscopy (TIRPAS) as a method of using the evanescent field to detect an optically opaque dye at a sample interface. Although their methods were successful at detecting dyes, the results at that time did not show a very practical spectroscopic technique, which was due to the less than typical sensitivity of TIRPAS as a spectroscopy modality given the low power (?1 to 2 W) lasers being used. Contrarily, we have used an Nd:YAG laser with a five nanosecond pulse that gives peak power of 1 MW coupled with the TIRPAS system to increase the sensitivity of this technique for biological material sensing. All efforts were focused on the eventual detection of the optically absorbing material, hemozoin, which is created as a byproduct of a malarial infection in blood. We used an optically analogous material, ?-hematin, to determine the potential for detection in the TIRPAS system. In addition, four properties which control the sensitivity were investigated to increase understanding about the sensor’s function as a biosensing method. PMID:22734742

Goldschmidt, Benjamin S.; Sudduth, Amanda S. M.; Samson, Edward B.; Whiteside, Paul J. D.; Bhattacharyya, Kiran D.; Viator, John A.

2012-01-01

430

Non-contact photoacoustic tomography and ultrasonography for brain imaging  

NASA Astrophysics Data System (ADS)

Photoacoustic tomography (PAT) and ultrasonography (US) of biological tissues usually rely on transducer arrays for the detection of ultrasound. Obtaining the best sensitivity requires a physical contact with the tissue using an intermediate coupling fluid (water or gel). This type of contact is a major drawback for several applications such as neurosurgery. Laser-ultrasonics is an established optical technique for the non-contact generation and detection of ultrasound in industrial materials. In this paper, the non-contact detection scheme used in laser-ultrasonics is adapted to allow probing of ultrasound in biological tissues while remaining below laser exposure safety limits. Both non-contact PAT (NCPAT) and non-contact US (NCUS) are demonstrated experimentally using a single-frequency detection laser emitting suitably shaped pulses and a confocal Fabry-Perot interferometer. It is shown that an acceptable sensitivity is obtained while remaining below the maximum permissible exposure (MPE) of biological tissues. Results obtained ex vivo with a calf brain specimen show that sub-mm endogenous and exogenous inclusions can be detected at depths exceeding 1 cm. When fully developed, the technique could be a unique diagnostic tool in neurosurgery providing deep imaging of blood vessels, blood clots and blood oxygenation.

Rousseau, Guy; Blouin, Alain; Monchalin, Jean-Pierre

2012-02-01

431

Inhibition by ethoxyzolamide of a photoacoustic uptake signal in leaves: Evidence for carbonic anhydrase catalyzed CO2-solubilisation  

Microsoft Academic Search

A photoacoustic pulse-modulation technique is applied for the study of a CO2-stimulated gas uptake signal in leaves (Reising and Schreiber, Photosynthe Res 31: 227–238, 1992). It is shown that this uptake signal can be substantially suppressed by application of the carbonic anhydrase inhibitor, ethoxyzolamide, to leaf discs. This inhibitor does not affect the O2-evolution signal in air or the chlorophyll

Heinz Reising; Ulrich Schreiber

1994-01-01

432

Comparative analysis of the planar capacitor and IDT piezoelectric thin-film micro-actuator models  

NASA Astrophysics Data System (ADS)

A comparison of the analysis of similarly developed microactuators is presented. Accurate modeling and simulation techniques are vital for piezoelectrically actuated microactuators. Coupling analytical and numerical modeling techniques with variational design parameters, accurate performance predictions can be realized. Axi-symmetric two-dimensional and three-dimensional static deflection and harmonic models of a planar capacitor actuator are presented. Planar capacitor samples were modeled as unimorph diaphragms with sandwiched piezoelectric material. The harmonic frequencies were calculated numerically and compared well to predicted values and deformations. The finite element modeling reflects the impact of the d31 piezoelectric constant. Two-dimensional axi-symmetric models of circularly interdigitated piezoelectrically membranes are also presented. The models include the piezoelectric material and properties, the membrane materials and properties, and incorporates various design considerations of the model. These models also include the electro-mechanical coupling for piezoelectric actuation and highlight a novel approach to take advantage of the higher d33 piezoelectric coupling coefficient. Performance is evaluated for varying parameters such as electrode pitch, electrode width, and piezoelectric material thickness. The models also showed that several of the design parameters were naturally coupled. The static numerical models correlate well with the maximum static deflection of the experimental devices. Finally, this paper deals with the development of numerical harmonic models of piezoelectrically actuated planar capacitor and interdigitated diaphragms. The models were able to closely predict the first two harmonics, conservatively predict the third through sixth harmonics and predict the estimated values of center deflection using plate theory. Harmonic frequency and deflection simulations need further correlation by conducting extensive iterative harmonic simulations and experiments. The results, conclusions and potential improvements are discussed.

Myers, Oliver J.; Anjanappa, M.; Freidhoff, Carl B.

2011-03-01

433

Piezoelectricity and growth polarization in III-V nitrides  

NASA Astrophysics Data System (ADS)

GaN, AlN and InN form a relatively new class of semiconductors being utilized for their direct wide bandgap and polarization effects. Novel transistors using only piezoelectric doping have already surpassed the power handling capabilities of traditional silicon transistors. GaN light emitting diodes and solid state lasers, sensitive to the effects of piezoelectric polarization, are rapidly proliferating for use in lighting and next generation optical storage devices. GaN and AIN sensors and MEMS devices using the strong piezoelectric coupling coefficients of these materials are slowly being introduced into communications and chemical sensing applications. Despite the importance of the piezoelectric effect in each of these devices, relatively little is known of the magnitude of the effect in GaN and AIN as measured experimentally. The present work seeks to develop an experimental method of measuring the piezoelectric effect in thin films of GaN and AIN. Using a stress pulse induced by the single shot of a Nd:YAG laser, substrates of polar GaAs and ZnO are subject to short duration loading which generates piezoelectric dipoles. The orientation and magnitude of these dipoles induces current flow in an external circuit which is measured as a function time. By comparing the magnitude of the current generated in this circuit and the applied stress, it is shown that the axial piezoelectric constant, e 33, can be determined. Extending the measurement technique to thin films of GaN and AIN on sapphire and silicon, we have observed the magnitude and orientation of the piezoelectric dipoles in these materials. A value of 0.45 C/m2 for e33 in GaN was determined. This work motivated a closer investigation of the polarity of GaN during crystal growth. The addition of Mg during MOCVD was found to cause a uniform inversion of the growth axis producing nitrogen terminated surfaces under certain growth conditions. Chemical-mechanical polishing of these surfaces with colloidal silica was found to produce smooth, damage free surfaces suitable for regrowth or additional processing. Growth of GaN and InGaN along the nitrogen polar direction was characterized by AFM, TEM, SIMS, x-ray, PL, and Hall measurements revealing surprisingly high quality material suitable for optical and electrical devices.

Tavernier, Philip Ross

434

Hydrogen Materials Compatibility in Piezoelectrics  

NASA Astrophysics Data System (ADS)

Hydrogen materials compatibility is an important materials science issue for hydrogen storage and delivery in hydrogen vehicle technology and infrastructure and to a lesser degree the microelectronics industry where hydrogen passivation is required. Piezoelectrics are one such material. They are used in direct injection hydrogen internal combustion engines (H2ICE) as actuators but tend to foul rapidly in high pressure hydrogen. Ferroelectric random access memory (FERAM) also suffers similar degradation issues. We present high pressure hydrogen absorption and diffusion findings for PZT and BaTiO3 piezoelectric materials. Data is based on quasi-elastic neutron (QENS) scattering and elastic recoil detection analysis (ERDA).

Alvine, Kyle; Pitman, Stan; Henager, Charles; Shutthanandan, Vaithiyalingam; Brown, Craig; Tyagi, Madhu; Jenkins, Tim; Udovic, Terry

2010-03-01

435

Piezoelectric Driver for Incremental Motion  

NASA Technical Reports Server (NTRS)

Vibrating device containing two piezoelectric ceramic slabs acts as mechanical driver. Eventually substitutes for small continuous or stepping electric motors of slow to moderate speeds. Piezoelectric driver simple in construction, requires no precise dimensions, inexpensive to make, and needs no lubrication. Not damaged by stalling or overloads and safe for use in explosive atmospheres; Motion controllable in micron-size increments, and holds position when power turned off. Potential applications as positioner or mover. Used to position instrument pointers, antennas, or solar panels; to focus lenses; or operate tuners, recording instruments, or valves.

Bruman, Joseph R.

1987-01-01

436

Application of the Pulsed Photoacoustic Spectroscopy in Biomedicine  

SciTech Connect

The use of optical spectroscopy as a diagnostic tool in biomedical applications and research has grown considerably in the last two decades. One of them is the pulsed photoacoustic or optoacoustic, which promises to be one of the most important tools for disease diagnostic studies, because while most spectroscopies exploit the optical nature of the light-tissue interaction, this field of photoacoustics uses optical energy to generate an acoustic wave which propagates in the tissue environment. The acoustic wave propagation is fundamentally related to various tissue properties and an analysis of the wave dynamics can provide insights into these properties. This work presents a review on pulsed photoacoustic spectroscopy of several photoacoustic methods to derive information about tissue and tissue phantoms.

Gutierrez-Juarez, G.; Sims, M. J.; Gupta, S. K.; Viator, J. A. [Department of Biological Engineering and Department of Dermatology University of Missouri, Columbia, Missouri 65211 (United States)

2008-08-11

437

Photoacoustic measurement of the Grüneisen parameter of tissue.  

PubMed

The Grüneisen parameter, a constitutive parameter in photoacoustics, is usually measured from isobaric thermal expansion, which may not be valid for a biological medium due to its heterogeneity. Here, we directly measured the Grüneisen parameter by applying photoacoustic spectroscopy. Laser pulses at wavelengths between 460 and 1800 nm were delivered to tissue samples, and photoacoustic signals were detected by flat water-immersion ultrasonic transducers. Least-squares fitting photoacoustic spectra to molar optical absorption spectra showed that the Grüneisen parameter was 0.81±0.05 (mean±SD) for porcine subcutaneous fat tissue and 0.69±0.02 for porcine lipid at room temperature (22°C). The Grüneisen parameter of a red blood cell suspension was linearly related to hemoglobin concentration, and the parameter of bovine serum was 9% greater than that of water at room temperature. PMID:24474512

Yao, Da-Kang; Zhang, Chi; Maslov, Konstantin; Wang, Lihong V

2014-01-01

438

Photoacoustic measurement of the Grüneisen parameter of tissue  

NASA Astrophysics Data System (ADS)

The Grüneisen parameter, a constitutive parameter in photoacoustics, is usually measured from isobaric thermal expansion, which may not be valid for a biological medium due to its heterogeneity. Here, we directly measured the Grüneisen parameter by applying photoacoustic spectroscopy. Laser pulses at wavelengths between 460 and 1800 nm were delivered to tissue samples, and photoacoustic signals were detected by flat water-immersion ultrasonic transducers. Least-squares fitting photoacoustic spectra to molar optical absorption spectra showed that the Grüneisen parameter was 0.81±0.05 (mean±SD) for porcine subcutaneous fat tissue and 0.69±0.02 for porcine lipid at room temperature (22°C). The Grüneisen parameter of a red blood cell suspension was linearly related to hemoglobin concentration, and the parameter of bovine serum was 9% greater than that of water at room temperature.

Yao, Da-Kang; Zhang, Chi; Maslov, Konstantin; Wang, Lihong V.

2014-01-01

439

Video-rate photoacoustic microscopy of micro-vasculatures  

NASA Astrophysics Data System (ADS)

We report the development of photoacoustic microscopy capable of video-rate high-resolution in-vivo imaging in deep tissue. A lightweight photoacoustic probe is made of a single-element broadband ultrasound transducer, a compact photoacoustic beam combiner, and a bright-field light delivery system. Focused broadband ultrasound detection provides a 44-?m lateral resolution and a 28-?m axial resolution. A multimode optical fiber is used to deliver laser pulses. The bright-field light delivery system can effectively improve the illumination efficiency. The photoacoustic probe weighs less than 40 grams and is mounted on a voice-coil scanner to acquire 40 cross-sectional images per second over several-mm range. The fast speed can effectively improve imaging throughput, reduce motion artifacts, and enable the visualization of highly dynamic biomedical processes. High-resolution micro-vascular imaging is successfully demonstrated.

Wang, Lidai; Maslov, Konstantin; Xing, Wenxin; Garcia-Uribe, Alejandro; Wang, Lihong V.

2013-03-01

440

Photoacoustic and thermoacoustic tomography: system development for biomedical applications  

E-print Network

Photoacoustic tomography (PAT), as well as thermoacoustic tomography (TAT), utilize electromagnetic radiation in its visible, near infrared, microwave, and radiofrequency forms, respectively, to induce acoustic waves in biological tissues...

Ku, Geng

2006-04-12

441

Photoacoustic measurement of methane concentrations with a compact pulsed  

E-print Network

Photoacoustic measurement of methane concentrations with a compact pulsed optical parametric, and Peter Hess A pulsed periodically poled lithium niobate optical parametric oscillator operating practical utilization of these lasers: low power, complex operation, limited continuous scan- ning range

Kung, Andy

442

Photoacoustic image-guided needle biopsy of sentinel lymph nodes  

NASA Astrophysics Data System (ADS)

We have implemented a hand-held photoacoustic and ultrasound probe for image-guided needle biopsy using a modified clinical ultrasound array system. Pulsed laser light was delivered via bifurcated optical fiber bundles integrated with the hand-held ultrasound probe. We photoacoustically guided needle insertion into rat sentinel lymph nodes (SLNs) following accumulation of indocyanine green (ICG). Strong photoacoustic image contrast of the needle was achieved. After intradermal injection of ICG in the left forepaw, deeply positioned SLNs (beneath 2-cm thick chicken breast) were easily indentified in vivo and in real time. Further, we confirmed ICG uptake in axillary lymph nodes with in vivo and ex vivo fluorescence imaging. These results demonstrate the clinical potential of this hand-held photoacoustic system for facile identification and needle biopsy of SLNs for cancer staging and metastasis detection in humans.

Kim, Chulhong; Erpelding, Todd N.; Akers, Walter J.; Maslov, Konstantin; Song, Liang; Jankovic, Ladislav; Margenthaler, Julie A.; Achilefu, Samuel; Wang, Lihong V.

2011-03-01

443

Theoretical aspects of photoacoustic spectroscopy with light scattering samples  

Microsoft Academic Search

A theoretical model for photoacoustic spectroscopy with light scattering samples is discussed. Some special cases are derived and the nature of the measured signal and the underlying physics are analyzed. Comparisons with transmission and diffuse reflectance spectroscopy are made.

Per Helander

1983-01-01

444

Enhancement of photoacoustic emission from self-supported plasmonic multilayers  

NASA Astrophysics Data System (ADS)

In this paper, we demonstrate remarkable photoacoustic emission from self-supported Au nanoparticle/dielectric/Ag mirror structures. They were prepared by depositing thin films on both sides of a 50-nm-thick silicon nitride membrane. The photoacoustic emission generated by the self-supported sample is more than 2 orders of magnitude larger than that of a similar structure supported by a Si wafer at a laser modulation frequency of 1 kHz. In this frequency region, the thermal diffusion length becomes much greater than the thickness of the multilayers, so that the photoacoustic amplitude is determined mainly by the thermal conductivity of the substrate. Therefore, the large enhancement of the photoacoustic emission can be understood in terms of the reduced thermal conductivity of the substrate.

Namura, Kyoko; Nakajima, Kaoru; Kimura, Kenji; Suzuki, Motofumi

2014-07-01

445

Functional photoacoustic microscopy of diabetic vasculature  

NASA Astrophysics Data System (ADS)

We used functional photoacoustic microscopy to image diabetes-induced damage to the microvasculature. To produce an animal model for Type 1 diabetes, we used streptozotocin (STZ), which is particularly toxic to the insulin-producing beta cells of the pancreas in mammals. A set number of ND4 Swiss Webster mice received intraperitoneal injections of STZ for five consecutive days at 50 mg/kg. Most mice developed a significant rise in blood glucose level (~400 mg/dL) within three weeks of the first injection. Changes in vasculature and hemodynamics were monitored for six weeks. The mouse ear was imaged with an optical-resolution photoacoustic microscope at a main blood vessel branch from the root of the ear. There are noticeable and measurable changes associated with the disease, including decreased vessel diameter and possible occlusion due to vessel damage and polyurea. We also observed an increase in the blood flow speed in the vein and a decrease in the artery, which could be due to compensation for the dehydration and vessel diameter changes. Functional and metabolic parameters such as hemoglobin oxygen saturation, oxygen extraction fraction, and oxygen consumption rate were also measured, but showed no significant change.

Krumholz, Arie; Wang, Lidai; Yao, Junjie; Wang, Lihong V.

2012-06-01

446

Application of piezoelectric sensors for stress-related measurements in wellbores  

E-print Network

simple external mechanical pulse initiates free vibrations, and the response are sensed by piezoelectric patches. Ultrasonic waves can also be used to measure stresses, and powerful piezoelectric materials are available to generate ultrasound . Yasui.... This ultrasonic technique uses electromagnetic transducers to measure applied stresses. To measure the stresses developed in structures or bridges embedded sensors, ultrasonic waves are used, because it works on painted, pitted, or rusted surfaces 17 Studies...