Science.gov

Sample records for polymer based self-healing

  1. Self-Healing of a Polyurethane-based Polymer Composite

    NASA Astrophysics Data System (ADS)

    Considine, Melissa

    2005-03-01

    An attempt has been made to extend the development of a self-healing polymer system to polyurethane polymers. Self-healing materials can improve reliability and prevent catastrophic failure of critical components that are inaccessible for routine maintenance and inspection. Previous work by others has shown that monomer-filled microcapsules embedded in an epoxy matrix containing dispersed solid catalyst can autonomously heal stress induced cracking. Synthesis of in-situ dicyclopentadiene (DCPD) encapsulated in poly(urea-formaldehyde) is embedded in a two-part (rigid) polyurethane matrix containing dispersed Grubb's catalyst. The modified composite is subsequently characterized. Characterization and testing of the as-fabricated polymer composite samples includes optical microscopy, scanning electron microscopy, FTIR spectroscopy, tensile testing and Izod impact testing. Following microcracking, induced toughening of the polymer matrix is anticipated as a result of microcapsule rupture that will release monomer to polymerize upon reaction with the embedded catalyst.

  2. Self-healing polymers

    NASA Technical Reports Server (NTRS)

    Klein, Daniel J. (Inventor)

    2011-01-01

    A three dimensional structure fabricated from a self-healing polymeric material, comprising poly(ester amides) obtained from ethylene glycol, azelaic acid and 1,1-aminoundecanoic acid, wherein polymeric material has a melt index above 2.5 g/10 min. as determined by ASTM D1238 at 190.degree. C. and 2.16kg, impact resistance and ductility sufficient to resist cracking and brittle fracture upon impact by a 9 mm bullet fired at a temperature of about 29.degree. C. at subsonic speed in a range from about 800 feet/sec to about 1000 feet/sec. It has been determined that the important factors necessary for self-healing behavior of polymers include sufficient impact strength, control of the degree of crystallinity, low melting point and the ability to instantly melt at impacted area.

  3. A multiple-responsive self-healing supramolecular polymer gel network based on multiple orthogonal interactions.

    PubMed

    Zhan, Jiayi; Zhang, Mingming; Zhou, Mi; Liu, Bin; Chen, Dong; Liu, Yuanyuan; Chen, Qianqian; Qiu, Huayu; Yin, Shouchun

    2014-08-01

    Supramolecular polymer networks have attracted considerable attention not only due to their topological importance but also because they can show some fantastic properties such as stimuli-responsiveness and self-healing. Although various supramolecular networks are constructed by supramolecular chemists based on different non-covalent interactions, supramolecular polymer networks based on multiple orthogonal interactions are still rare. Here, a supramolecular polymer network is presented on the basis of the host-guest interactions between dibenzo-24-crown-8 (DB24C8) and dibenzylammonium salts (DBAS), the metal-ligand coordination interactions between terpyridine and Zn(OTf)2 , and between 1,2,3-triazole and PdCl2 (PhCN)2 . The topology of the networks can be easily tuned from monomer to main-chain supramolecular polymer and then to the supramolecular networks. This process is well studied by various characterization methods such as (1) H NMR, UV-vis, DOSY, viscosity, and rheological measurements. More importantly, a supramolecular gel is obtained at high concentrations of the supramolecular networks, which demonstrates both stimuli-responsiveness and self-healing properties. PMID:24943122

  4. Self-Healing Polymer Networks

    NASA Astrophysics Data System (ADS)

    Tournilhac, Francois

    2012-02-01

    Supramolecular chemistry teaches us to control non-covalent interactions between organic molecules, particularly through the use of optimized building blocks able to establish several hydrogen bonds in parallel. This discipline has emerged as a powerful tool in the design of new materials through the concept of supramolecular polymers. One of the fascinating aspects of such materials is the possibility of controlling the structure, adding functionalities, adjusting the macroscopic properties of and taking profit of the non-trivial dynamics associated to the reversibility of H-bond links. Applications of these compounds may include adhesives, coatings, rheology additives, high performance materials, etc. However, the synthesis of such polymers at the industrial scale still remains a challenge. Our first ambition is to design supramolecular polymers with original properties, the second ambition is to devise simple and environmentally friendly methods for their industrial production. In our endeavours to create novel supramolecular networks with rubbery elasticity, self-healing ability and as little as possible creep, the strategy to prolongate the relaxation time and in the same time, keep the system flexible was to synthesize rather than a single molecule, an assembly of randomly branched H-bonding oligomers. We propose a strategy to obtain through a facile one-pot synthesis a large variety of supramolecular materials that can behave as differently as associating low-viscosity liquids, semi-crystalline or amorphous thermoplastics, viscoelastic melts or self-healing rubbers.

  5. Photothermal triggering of self-healing processes applied to the reparation of bio-based polymer networks

    NASA Astrophysics Data System (ADS)

    Altuna, F. I.; Antonacci, J.; Arenas, G. F.; Pettarin, V.; Hoppe, C. E.; Williams, R. J. J.

    2016-04-01

    Green laser irradiation successfully activated self-healing processes in epoxy-acid networks modified with low amounts of gold nanoparticles (NPs). A bio-based polymer matrix, obtained by crosslinking epoxidized soybean oil (ESO) with an aqueous citric acid (CA) solution, was self-healed through molecular rearrangements produced by transesterification reactions of β-hydroxyester groups generated in the polymerization reaction. The temperature increase required for the triggering of these thermally activated reactions was attained by green light irradiation of the damaged area. Compression force needed to assure a good contact between crack faces was achieved by volume dilatation generated by the same temperature rise. Gold NPs dispersed in the polymer efficiently generated heat in the presence of electromagnetic radiation under plasmon resonance, acting as nanometric heating sources and allowing remote activation of the self-healing in the crosslinked polymer.

  6. A self healing model based on polymer-mediated chromophore correlations

    NASA Astrophysics Data System (ADS)

    Ramini, Shiva K.; Kuzyk, Mark G.

    2012-08-01

    Here we present a model of self healing in which correlations between chromophores, as mediated by the polymer, are key to the recovery process. Our model determines the size distribution of the correlation volume using a grand canonical ensemble through a free energy advantage parameter. Choosing a healing rate that is proportional to the number of undamaged molecules in a correlated region, and a decay rate proportional to the intensity normalized to the correlation volume, the ensemble average is shown to correctly predict decay and recovery of the population of disperse orange 11-DO11 (1-amino-2-methylanthraquinone) molecules doped in PMMA polymer as a function of time and concentration as measured with amplified spontaneous emission and linear absorption spectroscopy using only three parameters that apply to the full set of data. Our model also predicts the temperature dependence of the process. One set of parameters should be characteristic of a particular polymer and dopant chromophore combination. Thus, the use of the model in determining these parameters for various materials systems should provide the data needed to test fundamental models of the underlying mechanism responsible for self healing.

  7. Developing Flexible, High Performance Polymers with Self-Healing Capabilities

    NASA Technical Reports Server (NTRS)

    Jolley, Scott T.; Williams, Martha K.; Gibson, Tracy L.; Caraccio, Anne J.

    2011-01-01

    Flexible, high performance polymers such as polyimides are often employed in aerospace applications. They typically find uses in areas where improved physical characteristics such as fire resistance, long term thermal stability, and solvent resistance are required. It is anticipated that such polymers could find uses in future long duration exploration missions as well. Their use would be even more advantageous if self-healing capability or mechanisms could be incorporated into these polymers. Such innovative approaches are currently being studied at the NASA Kennedy Space Center for use in high performance wiring systems or inflatable and habitation structures. Self-healing or self-sealing capability would significantly reduce maintenance requirements, and increase the safety and reliability performance of the systems into which these polymers would be incorporated. Many unique challenges need to be overcome in order to incorporate a self-healing mechanism into flexible, high performance polymers. Significant research into the incorporation of a self-healing mechanism into structural composites has been carried out over the past decade by a number of groups, notable among them being the University of I1linois [I]. Various mechanisms for the introduction of self-healing have been investigated. Examples of these are: 1) Microcapsule-based healant delivery. 2) Vascular network delivery. 3) Damage induced triggering of latent substrate properties. Successful self-healing has been demonstrated in structural epoxy systems with almost complete reestablishment of composite strength being achieved through the use of microcapsulation technology. However, the incorporation of a self-healing mechanism into a system in which the material is flexible, or a thin film, is much more challenging. In the case of using microencapsulation, healant core content must be small enough to reside in films less than 0.1 millimeters thick, and must overcome significant capillary and surface

  8. Synthesis of a Self-Healing Polymer Based on Reversible Diels-Alder Reaction: An Advanced Undergraduate Laboratory at the Interface of Organic Chemistry and Materials Science

    ERIC Educational Resources Information Center

    Weizman, Haim; Nielsen, Christian; Weizman, Or S.; Nemat-Nasser, Sia

    2011-01-01

    This laboratory experiment exposes students to the chemistry of self-healing polymers based on a Diels-Alder reaction. Students accomplish a multistep synthesis of a monomer building block and then polymerize it to form a cross-linked polymer. The healing capability of the polymer is verified by differential scanning calorimetry (DSC) experiments.…

  9. Puncture Self-Healing Polymers for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Gordon, Keith L.; Penner, Ronald K.; Bogert, Phil B.; Yost, W. T.; Siochi, Emilie J.

    2011-01-01

    Space exploration launch costs on the order of $10K per pound provide ample incentive to seek innovative, cost-effective ways to reduce structural mass without sacrificing safety and reliability. Damage-tolerant structural systems can provide a route to avoiding weight penalty while enhancing vehicle safety and reliability. Self-healing polymers capable of spontaneous puncture repair show great promise to mitigate potentially catastrophic damage from events such as micrometeoroid penetration. Effective self-repair requires these materials to heal instantaneously following projectile penetration while retaining structural integrity. Poly(ethylene-co-methacrylic acid) (EMMA), also known as Surlyn is an ionomer-based copolymer that undergoes puncture reversal (self-healing) following high impact puncture at high velocities. However EMMA is not a structural engineering polymer, and will not meet the demands of aerospace applications requiring self-healing engineering materials. Current efforts to identify candidate self-healing polymer materials for structural engineering systems are reported. Rheology, high speed thermography, and high speed video for self-healing semi-crystalline and amorphous polymers will be reported.

  10. Responsive Polymers as Sensors, Muscles, and Self-Healing Materials.

    PubMed

    Zhang, Qiang Matthew; Serpe, Michael J

    2015-01-01

    Responsive polymer-based materials can adapt to their surrounding environment by expanding and shrinking. This swelling and shrinking (mechanotransduction) can result in a number of functions. For example, the response can be used to lift masses, move objects, and can be used for sensing certain species in a system. Furthermore, responsive polymers can also yield materials capable of self-healing any damage affecting their mechanical properties. In this chapter we detail many examples of how mechanical responses can be triggered by external electric and/or magnetic fields, hygroscopicity, pH, temperature, and many other stimuli. We highlight how the specific responses can be used for artificial muscles, self-healing materials, and sensors, with particular focus on detailing the polymer response yielding desired effects.

  11. A polymer scaffold for self-healing perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Zhao, Yicheng; Wei, Jing; Li, Heng; Yan, Yin; Zhou, Wenke; Yu, Dapeng; Zhao, Qing

    2016-01-01

    Advancing of the lead halide perovskite solar cells towards photovoltaic market demands large-scale devices of high-power conversion efficiency, high reproducibility and stability via low-cost fabrication technology, and in particular resistance to humid environment for long-time operation. Here we achieve uniform perovskite film based on a novel polymer-scaffold architecture via a mild-temperature process. These solar cells exhibit efficiency of up to ~16% with small variation. The unencapsulated devices retain high output for up to 300 h in highly humid environment (70% relative humidity). Moreover, they show strong humidity resistant and self-healing behaviour, recovering rapidly after removing from water vapour. Not only the film can self-heal in this case, but the corresponding devices can present power conversion efficiency recovery after the water vapour is removed. Our work demonstrates the value of cheap, long chain and hygroscopic polymer scaffold in perovskite solar cells towards commercialization.

  12. A polymer scaffold for self-healing perovskite solar cells.

    PubMed

    Zhao, Yicheng; Wei, Jing; Li, Heng; Yan, Yin; Zhou, Wenke; Yu, Dapeng; Zhao, Qing

    2016-01-01

    Advancing of the lead halide perovskite solar cells towards photovoltaic market demands large-scale devices of high-power conversion efficiency, high reproducibility and stability via low-cost fabrication technology, and in particular resistance to humid environment for long-time operation. Here we achieve uniform perovskite film based on a novel polymer-scaffold architecture via a mild-temperature process. These solar cells exhibit efficiency of up to ∼ 16% with small variation. The unencapsulated devices retain high output for up to 300 h in highly humid environment (70% relative humidity). Moreover, they show strong humidity resistant and self-healing behaviour, recovering rapidly after removing from water vapour. Not only the film can self-heal in this case, but the corresponding devices can present power conversion efficiency recovery after the water vapour is removed. Our work demonstrates the value of cheap, long chain and hygroscopic polymer scaffold in perovskite solar cells towards commercialization. PMID:26732479

  13. A polymer scaffold for self-healing perovskite solar cells

    PubMed Central

    Zhao, Yicheng; Wei, Jing; Li, Heng; Yan, Yin; Zhou, Wenke; Yu, Dapeng; Zhao, Qing

    2016-01-01

    Advancing of the lead halide perovskite solar cells towards photovoltaic market demands large-scale devices of high-power conversion efficiency, high reproducibility and stability via low-cost fabrication technology, and in particular resistance to humid environment for long-time operation. Here we achieve uniform perovskite film based on a novel polymer-scaffold architecture via a mild-temperature process. These solar cells exhibit efficiency of up to ∼16% with small variation. The unencapsulated devices retain high output for up to 300 h in highly humid environment (70% relative humidity). Moreover, they show strong humidity resistant and self-healing behaviour, recovering rapidly after removing from water vapour. Not only the film can self-heal in this case, but the corresponding devices can present power conversion efficiency recovery after the water vapour is removed. Our work demonstrates the value of cheap, long chain and hygroscopic polymer scaffold in perovskite solar cells towards commercialization. PMID:26732479

  14. Chemistry of crosslinking processes for self-healing polymers.

    PubMed

    Billiet, Stijn; Hillewaere, Xander K D; Teixeira, Roberto F A; Du Prez, Filip E

    2013-02-25

    Recent developments in material design have seen an exponential increase of polymers and polymer composites that can repair themselves in response to damage. In this review, a distinction is made between extrinsic materials, where the self-healing property is obtained by adding healing agents to the material to be repaired, and intrinsic materials, where self-healing is achieved by the material itself through its chemical nature. An overview of the crosslinking chemistries used in self-healing materials will be given, discussing the advantages and drawbacks of each system. The review is not only aiming to enable researchers to compare their ongoing research with the state-of-the-art but also to serve as a guide for the newcomers, which allows for a selection of the most promising self-healing chemistries.

  15. Fatigue crack arrest in a self-healing polymer composite

    SciTech Connect

    Brown, E. N.; White, S. R.; Sottos, Nancy R.

    2004-01-01

    A comprehensive experimental program is performed to assess the in situ fatigue behavior of a self-healing polymer. A fatigue-life-extension protocol is established for characterizing healing efficiency of the self-healing epoxy under cyclic loading. At moderate {Delta}K{sub I} and at high {Delta}K{sub I}, when a rest period is employed, in situ healing extends fatigue life though temporary crack arrest and retardation. In situ self-healing permanently arrests crack growth at low {delta}K{sub I} and at moderate {Delta}K{sub I}, when a rest period is employed. Fatigue crack retardation and arrest result from two primary crack-tip shielding mechanisms: hydrodynamic pressure in the viscous healing agent and artificial crack closure. Application of self-healing functionality to fatigue slows the crack growth rate and increases the fatigue threshold.

  16. Impression Testing of Self-Healing Polymers

    NASA Technical Reports Server (NTRS)

    Hinkley, Jeffrey A.; Huber, Amy

    2005-01-01

    As part of the BIOSANT program (biologically-inspired smart nanotechnology), scientists at NASA-Langley have identified a "self-healing" plastic that spontaneously closes the hole left by the passage of a bullet. To understand and generalize the phenomenon in question, the mechanical properties responsible for this ability are being explored. Low-rate impression testing was chosen to characterize post-yield material properties, and it turned out that materials that heal following ballistic puncture also show up to 80% healing of the low-rate impression. Preliminary results on the effects of temperature and rate of puncture are presented.

  17. A self-healing polymer composite for extended fatigue life

    SciTech Connect

    Brown, E. N.; Jones, A. S.; White, S. R.; Sottos, Nancy R.

    2004-01-01

    A novel approach is explored for improving the fatigue life of thermosetting polymers through the addition of self-healing functionality. Thermosetting polymers are used in a wide variety of applications, but are susceptible to the initiation and propagation of small cracks deep within the structure where detection is difficult and repair is virtually impossible. The material under investigation is an epoxy matrix composite, which utilizes embedded microcapsules to store a healing agent and an embedded catalyst. A propagating crack exposes particles of catalyst and ruptures the microcapsules, which release healing agent into the crack plane. Polymerization of the healing agent is triggered by contact with the catalyst. Fatigue crack retardation and arrest from self-healing functionality result from crack-tip shielding mechanisms, such as hydrodynamic pressure and artificial-crack closure. In situ healing is observed to significantly extended fatigue life or permanently arrested fatigue crack growth over a wide range of loading conditions.

  18. Self-Healing of Polymer Networks with Reversible Bonds

    NASA Astrophysics Data System (ADS)

    Rubinstein, Michael

    2015-03-01

    Self-healing polymeric materials are systems that after damage can revert to their original state with full or partial recovery of mechanical strength. Using scaling theory we study a simple model of autonomic self-healing of polymer networks. In this model one of the two end monomers of each polymer chain is fixed in space mimicking dangling chains attachment to a polymer network, while the sticky monomer at the other end of each chain can form pairwise reversible bond with the sticky end of another chain. We study the reaction kinetics of reversible bonds in this simple model and analyze the different stages in the self-repair process. The formation of bridges and the recovery of the material strength across the fractured interface during the healing period occur appreciably faster after shorter waiting time, during which the fractured surfaces are kept apart. We observe the slowest formation of bridges for self-adhesion after bringing into contact two bare surfaces with equilibrium (very low) density of open stickers in comparison with self-healing. The primary role of anomalous diffusion in material self-repair for short waiting times is established, while at long waiting times the recovery of bonds across fractured interface is due to hopping diffusion of stickers between different bonded partners. Acceleration in bridge formation for self-healing compared to self-adhesion is due to excess nonequilibrium concentration of open stickers. Full recovery of reversible bonds across fractured interface (formation of bridges) occurs after appreciably longer time than the equilibration time of the concentration of reversible bonds in the bulk. The model is extended to describe enhanced toughness of dual networks with both permanent and reversible cross-links. This work was done in collaboration with Drs. Ludwik Leibler, Li-Heng Cai, Evgeny B. Stukalin, N. Arun Kumar and supported by the National Science Foundation.

  19. Self-Healing of Unentangled Polymer Networks with Reversible Bonds

    PubMed Central

    Stukalin, Evgeny B.; Cai, Li-Heng; Kumar, N. Arun; Leibler, Ludwik; Rubinstein, Michael

    2013-01-01

    Self-healing polymeric materials are systems that after damage can revert to their original state with full or partial recovery of mechanical strength. Using scaling theory we study a simple model of autonomic self-healing of unentangled polymer networks. In this model one of the two end monomers of each polymer chain is fixed in space mimicking dangling chains attachment to a polymer network, while the sticky monomer at the other end of each chain can form pairwise reversible bond with the sticky end of another chain. We study the reaction kinetics of reversible bonds in this simple model and analyze the different stages in the self-repair process. The formation of bridges and the recovery of the material strength across the fractured interface during the healing period occur appreciably faster after shorter waiting time, during which the fractured surfaces are kept apart. We observe the slowest formation of bridges for self-adhesion after bringing into contact two bare surfaces with equilibrium (very low) density of open stickers in comparison with self-healing. The primary role of anomalous diffusion in material self-repair for short waiting times is established, while at long waiting times the recovery of bonds across fractured interface is due to hopping diffusion of stickers between different bonded partners. Acceleration in bridge formation for self-healing compared to self-adhesion is due to excess non-equilibrium concentration of open stickers. Full recovery of reversible bonds across fractured interface (formation of bridges) occurs after appreciably longer time than the equilibration time of the concentration of reversible bonds in the bulk. PMID:24347684

  20. Dynamic sulfur chemistry as a key tool in the design of self-healing polymers

    NASA Astrophysics Data System (ADS)

    Martin, Roberto; Rekondo, Alaitz; Ruiz de Luzuriaga, Alaitz; Casuso, Pablo; Dupin, Damien; Cabañero, Germán; Grande, Hans J.; Odriozola, Ibon

    2016-08-01

    The rich variety of reversible or dynamic covalent chemistries based on sulfur offers a unique opportunity for the design of self-healing polymer networks. The reversibility of such chemical bonds can be used to create soft systems which can self-mend at ambient conditions. Here we focus on the mechanism of three different dynamic sulfur chemistries which have been used for the development of self-healing elastomers and hydrogels: thiolate/nanoparticle exchange, aromatic disulfide exchange and gold(I)-thiolate/disulfide exchange.

  1. Nature's Mechanisms for Tough, Self-healing Polymers and Polymer Adhesives

    NASA Astrophysics Data System (ADS)

    Hansma, Paul

    2007-03-01

    Spider silk^2 and the natural polymer adhesives in abalone shells^3 and bone^4,5 can give us insights into nature's mechanisms for tough, self-healing polymers and polymer adhesives. The natural polymer adhesives in biomaterials have been optimized by evolution. An optimized polymer adhesive has five characteristics. 1) It holds together the strong elements of the composite. 2) It yields just before the strong elements would otherwise break. 3) It dissipates large amounts of energy as it yields. 4) It self heals after it yields. 5) It takes just a few percent by weight. Both natural polymer adhesives and silk rely on sacrificial bonds and hidden length for toughness and self-healing.^6 A relatively large energy, of order 100eV, is required to stretch a polymer molecule after a weak bond, a sacrificial bond, breaks and liberates hidden length, which was previously hidden, typically in a loop or folded domain, from whatever was stretching the polymer. The bond is called sacrificial if it breaks at forces well below the forces that could otherwise break the polymer backbone, typically greater than 1nN. In many biological cases, the breaking of sacrificial bonds has been found to be reversible, thereby also providing a ``self-healing'' property to the material.^2-4 Individual polymer adhesive molecules based on sacrificial bonds and hidden length can supply forces of order 300pN over distances of 100s of nanometers. Model calculations show that a few percent by weight of adhesives based on these principles could be optimized adhesives for high performance composite materials including nanotube and graphene sheet composites. ^2N. Becker, E. Oroudjev, S. Mutz et al., Nature Materials 2 (4), 278 (2003). ^3B. L. Smith, T. E. Schaffer, M. Viani et al., Nature 399 (6738), 761 (1999). ^4J. B. Thompson, J. H. Kindt, B. Drake et al., Nature 414 (6865), 773 (2001). ^5G. E. Fantner, T. Hassenkam, J. H. Kindt et al., Nature Materials 4, 612 (2005). ^6G. E. Fantner, E. Oroudjev, G

  2. A rapidly self-healing supramolecular polymer hydrogel with photostimulated room-temperature phosphorescence responsiveness.

    PubMed

    Chen, Hui; Ma, Xiang; Wu, Shuaifan; Tian, He

    2014-12-15

    Development of self-healing and photostimulated luminescent supramolecular polymeric materials is important for artificial soft materials. A supramolecular polymeric hydrogel is reported based on the host-guest recognition between a β-cyclodextrin (β-CD) host polymer (poly-β-CD) and an α-bromonaphthalene (α-BrNp) polymer (poly-BrNp) without any additional gelator, which can self-heal within only about one minute under ambient atmosphere without any additive. This supramolecular polymer system can be excited to engender room-temperature phosphorescence (RTP) signals based on the fact that the inclusion of β-CD macrocycle with α-BrNp moiety is able to induce RTP emission (CD-RTP). The RTP signal can be adjusted reversibly by competitive complexation of β-CD with azobenzene moiety under specific irradiation by introducing another azobenzene guest polymer (poly-Azo). PMID:25323299

  3. Self-Healing Behavior of Ethylene-Based Ionomers

    NASA Technical Reports Server (NTRS)

    Kalista, Stephen J., Jr.; Ward, Thomas C.; Oyetunji, Zainab

    2004-01-01

    The self-healing behavior of poly(ethylene-co-methacrylic acid) (EMAA)-based ionomers holds tremendous potential for use in a wide variety of unique applications. However, to effectively utilize this self-healing behavior and to design novel materials which possess this ability, the mechanism by which they heal must first be understood ionomers are a class of polymers that can be described as copolymers containing less than 15 mol% ionic content whereby the bulk properties are governed by ionic interactions within the polymer. These ionic groups aggregate into discrete regions known as multiplets which overlap forming clusters that act as physical cross-links profoundly influencing the bulk physical properties. These clusters possess an order-disorder transition (T(sub i)) where the clustered regions may rearrange themselves given time and stimuli. Recognizing the strong influence of these ionic regions on other well understood ionomer properties, their role in self-heating behavior will be assessed. The self-healing behavior is observed following projectile puncture. It has been suggested that during impact energy is passed to the ionomer material, heating it to the melt state. After penetration, it is proposed that the ionic regions maintain their attractions and flow together patching the hole. Thus, the importance of this ionic character and is unique interaction must be established. This will be accomplished through examination of materials with varying ionic content and through the analysis of the T(sub i). The specific ionomer systems examined include a number of ethylene-based materials. Materials of varying ionic content, including the non-ionic base copolymers, will be examined by peel tests, projectile impact and DSC analysis. The information will also be compared with some basic data on LDPE material.

  4. Life extension of self-healing polymers with rapidly growing fatigue cracks.

    PubMed

    Jones, A S; Rule, J D; Moore, J S; Sottos, N R; White, S R

    2007-04-22

    Self-healing polymers, based on microencapsulated dicyclopentadiene and Grubbs' catalyst embedded in the polymer matrix, are capable of responding to propagating fatigue cracks by autonomic processes that lead to higher endurance limits and life extension, or even the complete arrest of the crack growth. The amount of fatigue-life extension depends on the relative magnitude of the mechanical kinetics of crack propagation and the chemical kinetics of healing. As the healing kinetics are accelerated, greater fatigue life extension is achieved. The use of wax-protected, recrystallized Grubbs' catalyst leads to a fourfold increase in the rate of polymerization of bulk dicyclopentadiene and extends the fatigue life of a polymer specimen over 30 times longer than a comparable non-healing specimen. The fatigue life of polymers under extremely fast fatigue crack growth can be extended through the incorporation of periodic rest periods, effectively training the self-healing polymeric material to achieve higher endurance limits.

  5. Self-healing graphene-based composites with sensing capabilities.

    PubMed

    D'Elia, Eleonora; Barg, Suelen; Ni, Na; Rocha, Victoria G; Saiz, Eduardo

    2015-08-26

    A self-healing composite is fabricated by confining a supramolecular polymer in a graphene network. The network provides electrical conductivity. Upon damage, the polymer is released and flows to reform the material. Healing is repeatable and autonomous. The composite is sensitive to pressure and flexion and recovers its mechanical and electrical properties even when rejoining cut surfaces after long exposure times. PMID:26178801

  6. Correlated aggregate model of self-healing in dye-doped polymers

    NASA Astrophysics Data System (ADS)

    Kuzyk, Mark G.; Ramini, Shiva

    2012-10-01

    Self healing of chromophores in a dye-doped polymer after photodegradation is a counterintuitive process based on the nearly universal observation that molecular damage is a thermodynamically irreversible process. We propose a new simple model of this phenomenon that takes into account all observations, including the effects of concentration, temperature, and bystander states. Critical to this model are correlations between chromophores, perhaps mediated by the polymer, which actively favors the undamaged species in analogy to Bose-Einstein condensation. We use this model to predict the behavior of decay and recovery experiments as measured with amplified spontaneous emission and absorption spectroscopy.

  7. Microcapsule-Type Organogel-Based Self-Healing System Having Secondary Damage Preventing Capability.

    PubMed

    Yang, Hye-In; Kim, Dong-Min; Yu, Hwan-Chul; Chung, Chan-Moon

    2016-05-01

    We have developed a novel microcapsule-type organogel-based self-healing system in which secondary damage does not occur in the healed region. A mixture of an organogelator, poor and good solvents for the gelator is used as the healing agent; when the good solvent evaporates from this agent, a viscoelastic organogel forms. The healing agent is microencapsulated with urea-formaldehyde polymer, and the resultant microcapsules are integrated into a polymer coating to prepare self-healing coatings. When the coatings are scratched, they self-heal, as demonstrated by means of corrosion testing, electrochemical testing, optical microscopy, and scanning electron microscopy (SEM). After the healed coatings are subjected to vigorous vibration, it is demonstrated that no secondary damage occurs in the healed region. The secondary damage preventing capability of the self-healing coating is attributable to the viscoelasticity of the organogel. The result can give insight into the development of a "permanent" self-healing system. PMID:27070306

  8. Thermally responsive polymer systems for self-healing, reversible adhesion and shape memory applications

    NASA Astrophysics Data System (ADS)

    Luo, Xiaofan

    /matrix structure, allowing them to function in a synergistic fashion yet remain physically separated. This latter aspect is critical since it enables the control of overall composite properties and functions by separately tuning each component. Utilizing the intrinsic versatility of this approach, composites with novel properties and functions (in addition to "regular" shape memory) have been developed, including (1) shape memory elastomeric composites (SMECs; Chapter 4), (2) triple-shape polymeric composites (TSPCs; Chapter 5), and (3) electrically conductive nanocomposites (Chapter 6). Then in Chapter 7, by combining the success in both thermoplastic based self-healing and shape memory polymer composites, we demonstrate a thermally triggered self-healing coating. This coating features a unique "shape memory assisted self-healing" mechanism in which crack closure (via shape memory) and crack re-bonding (via melting and diffusion of the thermoplastic healing agent) are achieved simultaneously upon a single heating step, leading to both structural and functional (corrosion resistance) recovery. Finally, Chapter 8 presents for the first time the preparation of functionally graded shape memory polymers (SMPs) that, unlike conventional SMPs, have a range of glass transition temperatures that are spatially graded. This was achieved using a temperature gradient curing method that imposes different vitrification limits at different positions along the gradient. The resulting material is capable of responding to a wide range of thermal triggers and a good candidate for low-cost, material based temperature sensors. All the aforementioned materials and methods show great potential for practical applications due to their high performance, low cost and broad applicability. Some recommendations for future research and development are given in Chapter 9.

  9. Self-Healing Polymer Dielectric for a High Capacitance Gate Insulator.

    PubMed

    Ko, Jieun; Kim, Young-Jae; Kim, Youn Sang

    2016-09-14

    Self-healing materials are required for development of various flexible electronic devices to repair cracks and ruptures caused by repetitive bending or folding. Specifically, a self-healing dielectric layer has huge potential to achieve healing electronics without mechanical breakdown in flexible operations. Here, we developed a high performance self-healing dielectric layer with an ionic liquid and catechol-functionalized polymer which exhibited a self-healing ability for both bulk and film states under mild self-healing conditions at 55 °C for 30 min. Due to the sufficient ion mobility of the ionic liquid in the polymer matrix, it had a high capacitance value above 1 μF/cm(2) at 20 Hz. Moreover, zinc oxide (ZnO) thin-film transistors (TFTs) with a self-healing dielectric layer exhibited a high field-effect mobility of 16.1 ± 3.07 cm(2) V(-1) s(-1) at a gate bias of 3 V. Even after repetitive self-healing of the dielectric layer from mechanical breaking, the electrical performance of the TFTs was well-maintained. PMID:27559823

  10. Self-Healing Polymer Dielectric for a High Capacitance Gate Insulator.

    PubMed

    Ko, Jieun; Kim, Young-Jae; Kim, Youn Sang

    2016-09-14

    Self-healing materials are required for development of various flexible electronic devices to repair cracks and ruptures caused by repetitive bending or folding. Specifically, a self-healing dielectric layer has huge potential to achieve healing electronics without mechanical breakdown in flexible operations. Here, we developed a high performance self-healing dielectric layer with an ionic liquid and catechol-functionalized polymer which exhibited a self-healing ability for both bulk and film states under mild self-healing conditions at 55 °C for 30 min. Due to the sufficient ion mobility of the ionic liquid in the polymer matrix, it had a high capacitance value above 1 μF/cm(2) at 20 Hz. Moreover, zinc oxide (ZnO) thin-film transistors (TFTs) with a self-healing dielectric layer exhibited a high field-effect mobility of 16.1 ± 3.07 cm(2) V(-1) s(-1) at a gate bias of 3 V. Even after repetitive self-healing of the dielectric layer from mechanical breaking, the electrical performance of the TFTs was well-maintained.

  11. Self-Healing Supramolecular Self-Assembled Hydrogels Based on Poly(L-glutamic acid).

    PubMed

    Li, Guifei; Wu, Jie; Wang, Bo; Yan, Shifeng; Zhang, Kunxi; Ding, Jianxun; Yin, Jingbo

    2015-11-01

    Self-healing polymeric hydrogels have the capability to recover their structures and functionalities upon injury, which are extremely attractive in emerging biomedical applications. This research reports a new kind of self-healing polypeptide hydrogels based on self-assembly between cholesterol (Chol)-modified triblock poly(L-glutamic acid)-block-poly(ethylene glycol)-block-poly(L-glutamic acid) ((PLGA-b-PEG-b-PLGA)-g-Chol) and β-cyclodextrin (β-CD)-modified poly(L-glutamic acid) (PLGA-g-β-CD). The hydrogel formation relied on the host and guest linkage between β-CD and Chol. This study demonstrates the influences of polymer concentration and β-CD/Chol molar ratio on viscoelastic behavior of the hydrogels. The results showed that storage modulus was highest at polymer concentration of 15% w/v and β-CD/Chol molar ratio of 1:1. The effect of the PLGA molecular weight in (PLGA-b-PEG-b-PLGA)-g-Chol on viscoelastic behavior, mechanical properties and in vitro degradation of the supramolecular hydrogels was also studied. The hydrogels showed outstanding self-healing capability and good cytocompatibility. The multilayer structure was constructed using hydrogels with self-healing ability. The developed hydrogels provide a fascinating glimpse for the applications in tissue engineering. PMID:26414083

  12. Self-Healing Supramolecular Self-Assembled Hydrogels Based on Poly(L-glutamic acid).

    PubMed

    Li, Guifei; Wu, Jie; Wang, Bo; Yan, Shifeng; Zhang, Kunxi; Ding, Jianxun; Yin, Jingbo

    2015-11-01

    Self-healing polymeric hydrogels have the capability to recover their structures and functionalities upon injury, which are extremely attractive in emerging biomedical applications. This research reports a new kind of self-healing polypeptide hydrogels based on self-assembly between cholesterol (Chol)-modified triblock poly(L-glutamic acid)-block-poly(ethylene glycol)-block-poly(L-glutamic acid) ((PLGA-b-PEG-b-PLGA)-g-Chol) and β-cyclodextrin (β-CD)-modified poly(L-glutamic acid) (PLGA-g-β-CD). The hydrogel formation relied on the host and guest linkage between β-CD and Chol. This study demonstrates the influences of polymer concentration and β-CD/Chol molar ratio on viscoelastic behavior of the hydrogels. The results showed that storage modulus was highest at polymer concentration of 15% w/v and β-CD/Chol molar ratio of 1:1. The effect of the PLGA molecular weight in (PLGA-b-PEG-b-PLGA)-g-Chol on viscoelastic behavior, mechanical properties and in vitro degradation of the supramolecular hydrogels was also studied. The hydrogels showed outstanding self-healing capability and good cytocompatibility. The multilayer structure was constructed using hydrogels with self-healing ability. The developed hydrogels provide a fascinating glimpse for the applications in tissue engineering.

  13. Self-healing supramolecular gels formed by crown ether based host-guest interactions.

    PubMed

    Zhang, Mingming; Xu, Donghua; Yan, Xuzhou; Chen, Jianzhuang; Dong, Shengyi; Zheng, Bo; Huang, Feihe

    2012-07-01

    Automatic repair: a polymer with pendent dibenzo[24]crown-8 units (purple in picture) was cross-linked by two bisammonium salts (green) to form two supramolecular gels based on host-guest interactions. These two gels are stimuli-responsive materials that respond to changes of the pH value and are also self-healing materials, as can be seen by eye and as evidenced by rheological data.

  14. Self-healing supramolecular gels formed by crown ether based host-guest interactions.

    PubMed

    Zhang, Mingming; Xu, Donghua; Yan, Xuzhou; Chen, Jianzhuang; Dong, Shengyi; Zheng, Bo; Huang, Feihe

    2012-07-01

    Automatic repair: a polymer with pendent dibenzo[24]crown-8 units (purple in picture) was cross-linked by two bisammonium salts (green) to form two supramolecular gels based on host-guest interactions. These two gels are stimuli-responsive materials that respond to changes of the pH value and are also self-healing materials, as can be seen by eye and as evidenced by rheological data. PMID:22653895

  15. Redox-responsive self-healing materials formed from host–guest polymers

    PubMed Central

    Nakahata, Masaki; Takashima, Yoshinori; Yamaguchi, Hiroyasu; Harada, Akira

    2011-01-01

    Expanding the useful lifespan of materials is becoming highly desirable, and self-healing and self-repairing materials may become valuable commodities. The formation of supramolecular materials through host–guest interactions is a powerful method to create non-conventional materials. Here we report the formation of supramolecular hydrogels and their redox-responsive and self-healing properties due to host–guest interactions. We employ cyclodextrin (CD) as a host molecule because it is environmentally benign and has diverse applications. A transparent supramolecular hydrogel quickly forms upon mixing poly(acrylic acid) (pAA) possessing β-CD as a host polymer with pAA possessing ferrocene as a guest polymer. Redox stimuli induce a sol−gel phase transition in the supramolecular hydrogel and can control self-healing properties such as re-adhesion between cut surfaces. PMID:22027591

  16. Ultra-thin Solid-State Li-Ion Electrolyte Membrane Facilitated by a Self-Healing Polymer Matrix.

    PubMed

    Whiteley, Justin M; Taynton, Philip; Zhang, Wei; Lee, Se-Hee

    2015-11-18

    Thin solid membranes are formed by a new strategy, whereby an in situ derived self-healing polymer matrix that penetrates the void space of an inorganic solid is created. The concept is applied as a separator in an all-solid-state battery with an FeS2 -based cathode and achieves tremendous performance for over 200 cycles. Processing in dry conditions represents a paradigm shift for incorporating high active-material mass loadings into mixed-matrix membranes.

  17. Seawater-Assisted Self-Healing of Catechol Polymers via Hydrogen Bonding and Coordination Interactions.

    PubMed

    Li, Jincai; Ejima, Hirotaka; Yoshie, Naoko

    2016-07-27

    It is highly desirable to prevent crack formation in polymeric materials at an early stage and to extend their lifespan, particularly when repairs to these materials would be difficult for humans. Here, we designed and synthesized catechol-functionalized polymers that can self-heal in seawater through hydrogen bonding and coordination. These bioinspired acrylate polymers are originally viscous materials, but after coordination with environmentally safe, common metal cations in seawater, namely, Ca(2+) and Mg(2+), the mechanical properties of the polymers were greatly enhanced from viscous to tough, hard materials. Reduced swelling in seawater compared with deionized water owing to the higher osmotic pressure resulted in greater toughness (∼5 MPa) and self-healing efficiencies (∼80%). PMID:27377859

  18. Unveiling the molecular mechanism of self-healing in a telechelic, supramolecular polymer network

    PubMed Central

    Yan, Tingzi; Schröter, Klaus; Herbst, Florian; Binder, Wolfgang H.; Thurn-Albrecht, Thomas

    2016-01-01

    Reversible polymeric networks can show self-healing properties due to their ability to reassemble after application of stress and fracture, but typically the relation between equilibrium molecular dynamics and self-healing kinetics has been difficult to disentangle. Here we present a well-characterized, self-assembled bulk network based on supramolecular assemblies, that allows a clear distinction between chain dynamics and network relaxation. Small angle x-ray scattering and rheological measurements provide evidence for a structurally well-defined, dense network of interconnected aggregates giving mechanical strength to the material. Different from a covalent network, the dynamic character of the supramolecular bonds enables macroscopic flow on a longer time scale and the establishment of an equilibrium structure. A combination of linear and nonlinear rheological measurements clearly identifies the terminal relaxation process as being responsible for the process of self-healing. PMID:27581380

  19. Unveiling the molecular mechanism of self-healing in a telechelic, supramolecular polymer network

    NASA Astrophysics Data System (ADS)

    Yan, Tingzi; Schröter, Klaus; Herbst, Florian; Binder, Wolfgang H.; Thurn-Albrecht, Thomas

    2016-09-01

    Reversible polymeric networks can show self-healing properties due to their ability to reassemble after application of stress and fracture, but typically the relation between equilibrium molecular dynamics and self-healing kinetics has been difficult to disentangle. Here we present a well-characterized, self-assembled bulk network based on supramolecular assemblies, that allows a clear distinction between chain dynamics and network relaxation. Small angle x-ray scattering and rheological measurements provide evidence for a structurally well-defined, dense network of interconnected aggregates giving mechanical strength to the material. Different from a covalent network, the dynamic character of the supramolecular bonds enables macroscopic flow on a longer time scale and the establishment of an equilibrium structure. A combination of linear and nonlinear rheological measurements clearly identifies the terminal relaxation process as being responsible for the process of self-healing.

  20. Unveiling the molecular mechanism of self-healing in a telechelic, supramolecular polymer network.

    PubMed

    Yan, Tingzi; Schröter, Klaus; Herbst, Florian; Binder, Wolfgang H; Thurn-Albrecht, Thomas

    2016-01-01

    Reversible polymeric networks can show self-healing properties due to their ability to reassemble after application of stress and fracture, but typically the relation between equilibrium molecular dynamics and self-healing kinetics has been difficult to disentangle. Here we present a well-characterized, self-assembled bulk network based on supramolecular assemblies, that allows a clear distinction between chain dynamics and network relaxation. Small angle x-ray scattering and rheological measurements provide evidence for a structurally well-defined, dense network of interconnected aggregates giving mechanical strength to the material. Different from a covalent network, the dynamic character of the supramolecular bonds enables macroscopic flow on a longer time scale and the establishment of an equilibrium structure. A combination of linear and nonlinear rheological measurements clearly identifies the terminal relaxation process as being responsible for the process of self-healing. PMID:27581380

  1. Repeated self-healing of microvascular carbon fibre reinforced polymer composites

    NASA Astrophysics Data System (ADS)

    Coope, T. S.; Wass, D. F.; Trask, R. S.; Bond, I. P.

    2014-11-01

    A self-healing, high performance, carbon fibre reinforced polymer (CFRP) composite is demonstrated by embedding a Lewis-acid catalytic curing agent within a laminate, manufactured using out of autoclave (OOA) composite manufacturing methods. Two configurations of healing agent delivery, pre-mixed and autonomous mixing, are investigated via injection of a healing agent through bio-inspired microvascular channels exposed on Mode I fractured crack planes. Healing is effected when an epoxy resin-solvent healing agent mixture reaches the boundary of embedded solid-state scandium(III) triflate (Sc(OTf)3) catalyst, located on the crack plane, to initiate the ring-opening polymerisation (ROP) of epoxides. Tailored self-healing agents confer high healing efficiency values after multiple healing cycles (69-108%) to successfully mitigate against crack propagation within the composite microstructure.

  2. Polymer damage mitigation---predictive lifetime models of polymer insulation degradation and biorenewable thermosets through cationic polymerization for self-healing applications

    NASA Astrophysics Data System (ADS)

    Hondred, Peter Raymond

    repairing damage before the damage causes a failure in the polymer's function. In this work, the healing agent (adhesive) is developed using bio-renewable oils instead of solely relying on petroleum based feedstocks. Several bio-renewable thermosetting polymers were successfully prepared from tung oil through cationic polymerization for the use as the healing agent in self-healing microencapsulated applications. Modifications to both the monomers in the resin and the catalyst for polymerization were made and the subsequent changes to mechanical, thermal, and structural properties were identified. Furthermore, compressive lap shear testing was used to confirm that the adhesive properties would be beneficial for self-healing applications. Finally, scanning electron microscopy of the crack plane was used to study the fracture mechanism of the crack.

  3. Self-Healing Nanofiber-Reinforced Polymer Composites. 1. Tensile Testing and Recovery of Mechanical Properties.

    PubMed

    Lee, Min Wook; An, Seongpil; Jo, Hong Seok; Yoon, Sam S; Yarin, Alexander L

    2015-09-01

    the composites reinforced by such mats. This is the first work, to the best of our knowledge, where self-healing nanofibers and composites based on them were developed, tested, and revealed restoration of mechanical properties (stiffness) in a 24 h rest period at room temperature. PMID:26284888

  4. Self-healing antimicrobial polymer coating with efficacy in the presence of organic matter

    NASA Astrophysics Data System (ADS)

    Bastarrachea, Luis J.; Goddard, Julie M.

    2016-08-01

    A method to prepare a self-healing, antimicrobial polymer coating that retains efficacy against Escherichia coli O157:H7 in the presence of organic matter is reported. A coating composed of branched polyethyleneimine (PEI) and styrene maleic anhydride copolymer (SMA) was applied to a maleic anhydride functionalized polypropylene support. The chemistry of the polymer coating was designed to impart hydrophobicity due to the styrene subunits, intrinsic antimicrobial character (>99.9% reduction) from the cationic primary amine groups, and enhanced antimicrobial character (> 99.99% reduction) after chlorination of N-halamine forming groups. Antimicrobial effectiveness was demonstrated under conditions of increasing organic load. Up to 500 ppm horse serum, chlorinated coatings retained full antimicrobial character (>99.99% reduction). Even at 50,000 ppm of horse serum, the coating provided ∼90% reduction as prepared, and between ∼75% and ∼80% reduction in the form of N-halamines. Microscopy confirmed no evidence of bacterial adhesion on the coating surface. Finally, the coating exhibited self-healing properties after exposure to acid and alkaline solutions and restoration by heat, as confirmed through spectroscopy from the rebuilding of characteristic chemical bonds. Such robust antimicrobial polymer coatings with efficacy under conditions of increasing organic load may support reducing microbial cross-contamination in food and biomedical industries.

  5. Surface-initiated self-healing of polymers in aqueous media

    NASA Astrophysics Data System (ADS)

    Ahn, B. Kollbe; Lee, Dong Woog; Israelachvili, Jacob N.; Waite, J. Herbert

    2014-09-01

    Polymeric materials that intrinsically heal at damage sites under wet or moist conditions are urgently needed for biomedical and environmental applications. Although hydrogels with self-mending properties have been engineered by means of mussel-inspired metal-chelating catechol-functionalized polymer networks, biological self-healing in wet conditions, as occurs in self-assembled holdfast proteins in mussels and other marine organisms, is generally thought to involve more than reversible metal chelates. Here we demonstrate self-mending in metal-free water of synthetic polyacrylate and polymethacrylate materials that are surface-functionalized with mussel-inspired catechols. Wet self-mending of scission in these polymers is initiated and accelerated by hydrogen bonding between interfacial catechol moieties, and consolidated by the recruitment of other non-covalent interactions contributed by subsurface moieties. The repaired and pristine samples show similar mechanical properties, suggesting that the triggering of complete self-healing is enabled underwater by the formation of extensive catechol-mediated interfacial hydrogen bonds.

  6. Surface-initiated self-healing of polymers in aqueous media.

    PubMed

    Ahn, B Kollbe; Lee, Dong Woog; Israelachvili, Jacob N; Waite, J Herbert

    2014-09-01

    Polymeric materials that intrinsically heal at damage sites under wet or moist conditions are urgently needed for biomedical and environmental applications. Although hydrogels with self-mending properties have been engineered by means of mussel-inspired metal-chelating catechol-functionalized polymer networks, biological self-healing in wet conditions, as occurs in self-assembled holdfast proteins in mussels and other marine organisms, is generally thought to involve more than reversible metal chelates. Here we demonstrate self-mending in metal-free water of synthetic polyacrylate and polymethacrylate materials that are surface-functionalized with mussel-inspired catechols. Wet self-mending of scission in these polymers is initiated and accelerated by hydrogen bonding between interfacial catechol moieties, and consolidated by the recruitment of other non-covalent interactions contributed by subsurface moieties. The repaired and pristine samples show similar mechanical properties, suggesting that the triggering of complete self-healing is enabled underwater by the formation of extensive catechol-mediated interfacial hydrogen bonds.

  7. Dynamic urea bond for the design of reversible and self-healing polymers

    PubMed Central

    Ying, Hanze; Zhang, Yanfeng; Cheng, Jianjun

    2014-01-01

    Polymers bearing dynamic covalent bonds may exhibit dynamic properties, such as self-healing, shape memory and environmental adaptation. However, most dynamic covalent chemistries developed so far require either catalyst or change of environmental conditions to facilitate bond reversion and dynamic property change in bulk materials. Here we report the rational design of hindered urea bonds (urea with bulky substituent attached to its nitrogen) and the use of them to make polyureas and poly(urethane-ureas) capable of catalyst-free dynamic property change and autonomous repairing at low temperature. Given the simplicity of the hindered urea bond chemistry (reaction of a bulky amine with an isocyanate), incorporation of the catalyst-free dynamic covalent urea bonds to conventional polyurea or urea-containing polymers that typically have stable bulk properties may further broaden the scope of applications of these widely used materials. PMID:24492620

  8. Synthetic Self-Healing Methods

    SciTech Connect

    Bello, Mollie

    2014-06-02

    Given enough time, pressure, temperature fluctuation, and stress any material will fail. Currently, synthesized materials make up a large part of our everyday lives, and are used in a number of important applications such as; space travel, under water devices, precise instrumentation, transportation, and infrastructure. Structural failure of these material scan lead to expensive and dangerous consequences. In an attempt to prolong the life spans of specific materials and reduce efforts put into repairing them, biologically inspired, self-healing systems have been extensively investigated. The current review explores recent advances in three methods of synthesized self-healing: capsule based, vascular, and intrinsic. Ideally, self-healing materials require no human intervention to promote healing, are capable of surviving all the steps of polymer processing, and heal the same location repeatedly. Only the vascular method holds up to all of these idealities.

  9. Self-healing phenomenon and dynamic hardness of C60-based nanocomposite coatings.

    PubMed

    Penkov, Oleksiy V; Pukha, Volodymyr E; Devizenko, Alexander Yu; Kim, Hae-Jin; Kim, Dae-Eun

    2014-05-14

    The phenomenon of surface self-healing in C60-based polymer coatings deposited by ion-beam assisted physical vapor deposition was investigated. Nanoindentation of the coatings led to the formation of a protrusion rather than an indent. This protrusion was accompanied by an abnormal shape of the force-distance curve, where the unloading curve lies above the loading curve due to an additional force applied in pulling the indenter out of the media. The coatings exhibited a nanocomposite structure that was strongly affected by the ratio of C60 ion and C60 molecular beam intensities during deposition. The coatings also demonstrated the dynamic hardness effect, where the effective value of the hardness depends significantly on the indentation speed.

  10. Self-healing gels based on constitutional dynamic chemistry and their potential applications.

    PubMed

    Wei, Zhao; Yang, Jian Hai; Zhou, Jinxiong; Xu, Feng; Zrínyi, Miklós; Dussault, Patrick H; Osada, Yoshihito; Chen, Yong Mei

    2014-12-01

    As representative soft materials with widespread applications, gels with various functions have been developed. However, traditional gels are vulnerable to stress-induced formation of cracks. The propagation of these cracks may affect the integrity of network structures of gels, resulting in the loss of functionality and limiting the service life of the gels. To address this challenge, self-healing gels that can restore their functionalities and structures after damage have been developed as "smart" soft materials. In this paper, we present an overview of the current strategies for synthesizing self-healing gels based on the concept of constitutional dynamic chemistry, which involves molecular structures capable of establishing dynamic networks based upon physical interactions or chemical reactions. The characterization methods of self-healing gels and the key factors that affect self-healing properties are analyzed. We also illustrate the emerging applications of self-healing gels, with emphasis on their usage in industry (coatings, sealants) and biomedicine (tissue adhesives, agents for drug or cell delivery). We conclude with a perspective on challenges facing the field, along with prospects for future development. PMID:25144925

  11. Synthesis and characterization of melamine-urea-formaldehyde microcapsules containing ENB-based self-healing agents

    NASA Astrophysics Data System (ADS)

    Liu, Xing; Sheng, Xia; Lee, Jong Keun; Kessler, Michael R.

    2007-07-01

    Microcapsules for self-healing applications were produced with a melamine-urea-formaldehyde (MUF) polymer shell containing two different healing agent candidates, ENB (5-ethylidene-2-norbornene) and ENB with 10 wt.% of a norbornene based crosslinking agent (CL), by in-situ polymerization in an oil-in-water emulsion. Relatively neat outer surfaces with minor roughness were observed on the MUF microcapsules under optical and scanning electron microscopy. Shell thickness of the capsules ranged from 700 to 900 nm. Particle size analysis of the microcapsules showed narrow size distributions with a mean diameter of 113 μm for ENB-filled and 122 μm for ENB+CL-filled microcapsules at an agitation rate of 500 rpm. The microcapsules were found to be thermally stable up to 300°C and exhibited a 10 to 15 % weight loss when isothermally held at 150°C for 2 hr from thermogravimetric analysis. Overall, these MUF microcapsules exhibited superior properties compared to the urea-formaldehyde (UF) microcapsules used extensively for self-healing composites to date. In addition, the manufacturing process of MUF microcapsules is much simpler than those made from UF. Additional advantages of MUF microcapsules for self-healing composites are discussed.

  12. Effect of Polymer Porosity on Aqueous Self-Healing Encapsulation of Proteins in PLGA Microspheres

    PubMed Central

    Reinhold, Samuel E.

    2014-01-01

    Self-healing (SH) poly(lactic-co-glycolic acid) (PLGA) microspheres are a unique class of functional biomaterials capable of microencapsulating process-sensitive proteins by simple mixing and heating the drug-free polymer in aqueous protein solution. Drug-free SH microspheres of PLGA 50/50 with percolating pore networks of varying porosity (ε = 0.49–73) encapsulate increasing lysozyme (~1–10% w/w) with increasing ε, with typically ~20–25% pores estimated assessible to entry by the enzyme from the external solution. Release kinetics of lysozyme under physiological conditions is continuous over > 2 weeks and most strongly influenced by ε and protein loading before reaching a lag phase until 28 days at the study completion. Recovered enzyme after release is typically predominantly monomeric and active. Formulations containing acid-neutralizing MgCO3 at >4.3% exhibit >97% monomeric and active protein after the release with full mass balance recovery. Hence, control of SH polymer ε is a key parameter to development of this new class of biomaterials. PMID:24285573

  13. Novel Diels-Alder based self-healing epoxies for aerospace composites

    NASA Astrophysics Data System (ADS)

    Coope, T. S.; Turkenburg, D. H.; Fischer, H. R.; Luterbacher, R.; van Bracht, H.; Bond, I. P.

    2016-08-01

    Epoxy resins containing Diels-Alder (DA) furan and maleimide moieties are presented with the capability to self-heal after exposure to an external heat source. A conventional epoxy amine system has been combined with furfuryl and maleimide functional groups in a two-step process, to avoid major side-reactions, and the concentration of a thermo-reversibly binding cross-linker was considered to balance thermoset and thermoplastic behaviours, and the subsequent self-healing performance. In the context of self-repair technologies an inbuilt ‘intrinsic’ self-healing system is deemed favourable as the healing agent can be placed in known ‘hot spot’ regions (i.e. skin-stringer run outs, ply drops and around drilled holes) where operational damage predominately occurs in load bearing aerospace structures. In this study, the mechanical and self-healing performance of furan functionalised epoxy resins containing varying amounts (10, 20, 30 or 40 pph) of bismaleimide were investigated using a bulk epoxy polymer tapered double cantilever beam test specimen geometry. Two forms, a thin film and a bulk material, were evaluated to account for future integration methods into fibre reinforced polymer (FRP) composites. The highest healing efficiency, with respect to the obtained initial load value, was observed from the 20 pph bulk material derivative. The polymers were successful in achieving consistent multiple (three) healing cycles when heated at 150 °C for 5 min. This novel investigated DA material exhibits favourable processing characteristics for FRP composites as preliminary studies have shown successful coextrution with reinforcing fibres to form free standing films and dry fibre impregnation.

  14. Self-Healing and Thermoresponsive Dual-Cross-Linked Alginate Hydrogels Based on Supramolecular Inclusion Complexes.

    PubMed

    Miao, Tianxin; Fenn, Spencer L; Charron, Patrick N; Oldinski, Rachael A

    2015-12-14

    β-Cyclodextrin (β-CD), with a lipophilic inner cavity and hydrophilic outer surface, interacts with a large variety of nonpolar guest molecules to form noncovalent inclusion complexes. Conjugation of β-CD onto biomacromolecules can form physically cross-linked hydrogel networks upon mixing with a guest molecule. Herein, the development and characterization of self-healing, thermoresponsive hydrogels, based on host-guest inclusion complexes between alginate-graft-β-CD and Pluronic F108 (poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol)), are described. The mechanics, flow characteristics, and thermal response were contingent on the polymer concentration and the host-guest molar ratio. Transient and reversible physical cross-linking between host and guest polymers governed self-assembly, allowing flow to occur under shear stress and facilitating complete recovery of the material's properties within a few seconds of unloading. The mechanical properties of the dual-cross-linked, multi-stimuli-responsive hydrogels were tuned as high as 30 kPa at body temperature and are advantageous for biomedical applications such as drug delivery and cell transplantation. PMID:26509214

  15. A Stretchable Graphitic Carbon/Si Anode Enabled by Conformal Coating of a Self-Healing Elastic Polymer.

    PubMed

    Sun, Yongming; Lopez, Jeffrey; Lee, Hyun-Wook; Liu, Nian; Zheng, Guangyuan; Wu, Chun-Lan; Sun, Jie; Liu, Wei; Chung, Jong Won; Bao, Zhenan; Cui, Yi

    2016-03-23

    A high-capacity stretchable graphitic carbon/Si foam electrode is enabled by a conformal self-healing elastic polymer coating. The composite electrode exhibits high stretchability (up to 88%) and endures 1000 stretching-releasing cycles at 25% strain with detrimental resistance increase. Meanwhile, the electrode delivers a high reversible specific capacity of 719 mA g(-1) and good cycling stability with 81% capacity retention after 100 cycles. PMID:26813780

  16. Induction and Tunability of Self-Healing Property of Dendron Based Hydrogel Using Clay Nanocomposite.

    PubMed

    Vivek, Balachandran; Kumar, Prashant; Prasad, Edamana

    2016-06-16

    Low molecular weight gels have relatively poor self-healing capacity compared to that of polymeric gels. Induction and tuning of the healing capacity of low molecular weight gels to achieve desired applications are thus challenging tasks. The present work describes the achievement of remarkable tunability of self-healing property for a low molecular weight hybrid gel, based on poly(aryl ether) dendron derivative (PAD). The hybrid gel has been synthesized using PAD and poly(amido amine) {PAMAM} dendrimer derivative (QPD), which are intercalated in the montmorillonite clay (MMT) layers. The self-healing of the hybrid gel (QPD-MMT-PAD) was demonstrated through experiments where the distorted gel regained the initial value of storage modulus (G') within a few minutes. Further, the propensity of self-healing of the gel has been tuned as a function of QPD concentration. The mechanically stable QPD-MMT-PAD hybrid gel has been utilized for the adsorption of ppm level concentration of polycyclic aromatic hydrocarbons (PAHs) such as β-naphthol, pyrene, and phenenathrene from water with excellent efficiency (80-98%). PMID:27193239

  17. Solvent-based self-healing approaches for fiber-reinforced composites

    NASA Astrophysics Data System (ADS)

    Jones, Amanda R.

    Damage in composite materials spans many length scales and is often difficult to detect or costly to repair. The incorporation of self-healing functionality in composite materials has the potential to greatly extend material lifetime and reliability. Although there has been remarkable progress in self-healing polymers over the past decade, self-repair in fiber-reinforced composite materials presents significant technical challenges due to stringent manufacturing and performance requirements. For high performance, fiber-reinforced composites, the self-healing components need to survive high temperature processing, reside in matrix interstitial regions to retain a high fiber volume fraction, and have minimal impact on the mechanical properties of the host material. This dissertation explores several microencapsulated solvent-based self-healing approaches for fiber-reinforced composites at the fiber/ matrix interface size scale as well as matrix cracking. Systems are initially developed for room temperature cured epoxies/ glass fiber interfaces and successfully transitioned to carbon fibers and high temperature-cured, thermoplastic-toughened matrices. Full recovery of interfacial bond strength after complete fiber/matrix debonding is achieved with a microencapsulated solvent-based healing chemistry. The surface of a glass fiber is functionalized with microcapsules containing varying concentrations of reactive epoxy resin and ethyl phenyl acetate (EPA) solvent. Microbond specimens consisting of a single fiber and a microdroplet of epoxy are cured at 35°C, tested, and the interfacial shear strengths (IFSS) during the initial (virgin) debonding and subsequent healing events are measured. Debonding of the fiber/matrix interface ruptures the capsules, releasing resin and solvent into the crack plane. The solvent swells the matrix, initiating transport of residual amine functionality for further curing with the epoxy resin delivered to the crack plane. Using a resin

  18. An Easily Accessible Self-Healing Transparent Film Based on a 2D Supramolecular Network of Hydrogen-Bonding Interactions between Polymeric Chains.

    PubMed

    Roy, Nabarun; Tomović, Željko; Buhler, Eric; Lehn, Jean-Marie

    2016-09-12

    Self-healing polymers hold great promise for the future, enhancing in particular the longevity of polymeric materials. We describe a self-healing covalent polymer, presenting an extensive array of hydrogen-bonding sites based on the combination of urea, urethane, and bis-acyl-hydrazine units. Solvent-cast thin-films prepared by polycondensation of a commercially available dihydrazide and a diisocyanate prepolymer exhibited excellent room temperature autonomous healing with almost full recovery of mechanical properties when two parts of a cut film were overlapped and gently pressed together. This autonomous healing upon damage may be attributed to the supramolecular dynamics of multiple lateral inter-chain hydrogen-bonding interactions between the polymer chains. The solid-state structure of a model compound incorporating the same structural backbone corroborates the existence of an extensive two-dimensional supramolecular hydrogen-bonding network. PMID:27226034

  19. Correlation between molecular structure and self-healing in a series of Anthraquinone derivatives doped in PMMA polymer

    NASA Astrophysics Data System (ADS)

    Dhakal, P.; Ramini, S. K.; Kuzyk, Mark G.

    2012-10-01

    We observe that many different derivatives of anthraquinone chromophores doped in PMMA self heal after undergoing photodegradation. We are interested to know the mechanisms that are responsible for photodegradation and photorecovery, which are not yet fully understood. We used fluorescence and absorption spectroscopy as a probe of the photodegradation and recovery process while the temperature dependence is used to determine the energies of the species involved. We hypothesize that the host polymer mediates the formation of a quasi-stable state. In this scenario, once photo - damaged by intense pump laser, the molecules non radiatively decay into a tautomer state by intra molecule proton transfer, which subsequently leads to the formation of a damaged species - leading to decay of the fluorescence intensity. This hypothesis is consistent with our observation. The temperature dependent fluorescence decay and recovery studies give an insight about the different energy levels participating in optical excitation, decay and recovery. Comparing the experimental parameters such as decay and recovery rates of the fluorescence signal associated with the evolution of peaks in the fluorescence and absorbance spectrum helps us understand correlations between the efficiency of the recovery process and the structures of the dye molecules. Based on the temperature and the time-dependent observations of fluorescence and absorption, we validate qualitatively a new theoretical model which qualitatively takes into account the observed behavior and sheds light on the underlying mechanism. Preliminary measurements show good agreement with the theoretical model. More careful experiments and calculations are in process for further validation of the model.

  20. Injectable and Self-Healing Carbohydrate-Based Hydrogel for Cell Encapsulation.

    PubMed

    Lü, Shaoyu; Gao, Chunmei; Xu, Xiubin; Bai, Xiao; Duan, Haogang; Gao, Nannan; Feng, Chen; Xiong, Yun; Liu, Mingzhu

    2015-06-17

    With the fast development of cell therapy, there has been a shift toward the development of injectable hydrogels as cell carriers that can overcome current limitations in cell therapy. However, the hydrogels are prone to damage during use, inducing cell apoptosis. Therefore, this study was carried out to develop an injectable and self-healing hydrogel based on chondroitin sulfate multiple aldehyde (CSMA) and N-succinyl-chitosan (SC). By varying the CSMA to SC ratio, the hydrogel stiffness, water content, and kinetics of gelation could be controlled. Gelation readily occurred at physiological conditions, predominantly due to a Schiff base reaction between the aldehyde groups on CSMA and amino groups on SC. Meanwhile, because of the dynamic equilibrium of Schiff base linkage, the hydrogel was found to be self-healing. Cells encapsulated in the hydrogel remained viable and metabolically active. In addition, the hydrogel produced minimal inflammatory response when injected subcutaneously in a rat model and showed biodegradability in vivo. This work establishes an injectable and self-healing hydrogel derived from carbohydrates with potential applications as a cell carrier and in tissue engineering.

  1. Injectable and Self-Healing Carbohydrate-Based Hydrogel for Cell Encapsulation.

    PubMed

    Lü, Shaoyu; Gao, Chunmei; Xu, Xiubin; Bai, Xiao; Duan, Haogang; Gao, Nannan; Feng, Chen; Xiong, Yun; Liu, Mingzhu

    2015-06-17

    With the fast development of cell therapy, there has been a shift toward the development of injectable hydrogels as cell carriers that can overcome current limitations in cell therapy. However, the hydrogels are prone to damage during use, inducing cell apoptosis. Therefore, this study was carried out to develop an injectable and self-healing hydrogel based on chondroitin sulfate multiple aldehyde (CSMA) and N-succinyl-chitosan (SC). By varying the CSMA to SC ratio, the hydrogel stiffness, water content, and kinetics of gelation could be controlled. Gelation readily occurred at physiological conditions, predominantly due to a Schiff base reaction between the aldehyde groups on CSMA and amino groups on SC. Meanwhile, because of the dynamic equilibrium of Schiff base linkage, the hydrogel was found to be self-healing. Cells encapsulated in the hydrogel remained viable and metabolically active. In addition, the hydrogel produced minimal inflammatory response when injected subcutaneously in a rat model and showed biodegradability in vivo. This work establishes an injectable and self-healing hydrogel derived from carbohydrates with potential applications as a cell carrier and in tissue engineering. PMID:26016388

  2. A bacteria-based bead for possible self-healing marine concrete applications

    NASA Astrophysics Data System (ADS)

    Palin, D.; Wiktor, V.; Jonkers, H. M.

    2016-08-01

    This work presents a bacteria-based bead for potential self-healing concrete applications in low-temperature marine environments. The bead consisting of calcium alginate encapsulated bacterial spores and mineral precursor compounds was assessed for: oxygen consumption, swelling, and its ability to form a biocomposite in a simulative marine concrete crack solution (SMCCS) at 8 °C. After six days immersion in the SMCCS the bacteria-based beads formed a calcite crust on their surface and calcite inclusions in their network, resulting in a calcite–alginate biocomposite. Beads swelled by 300% to a maximum diameter of 3 mm, while theoretical calculations estimate that 0.112 g of the beads were able to produce ∼1 mm3 of calcite after 14 days immersion; providing the bead with considerable crack healing potential. The bacteria-based bead shows great potential for the development of self-healing concrete in low-temperature marine environments, while the formation of a biocomposite healing material represents an exciting avenue for self-healing concrete research.

  3. A bacteria-based bead for possible self-healing marine concrete applications

    NASA Astrophysics Data System (ADS)

    Palin, D.; Wiktor, V.; Jonkers, H. M.

    2016-08-01

    This work presents a bacteria-based bead for potential self-healing concrete applications in low-temperature marine environments. The bead consisting of calcium alginate encapsulated bacterial spores and mineral precursor compounds was assessed for: oxygen consumption, swelling, and its ability to form a biocomposite in a simulative marine concrete crack solution (SMCCS) at 8 °C. After six days immersion in the SMCCS the bacteria-based beads formed a calcite crust on their surface and calcite inclusions in their network, resulting in a calcite-alginate biocomposite. Beads swelled by 300% to a maximum diameter of 3 mm, while theoretical calculations estimate that 0.112 g of the beads were able to produce ˜1 mm3 of calcite after 14 days immersion; providing the bead with considerable crack healing potential. The bacteria-based bead shows great potential for the development of self-healing concrete in low-temperature marine environments, while the formation of a biocomposite healing material represents an exciting avenue for self-healing concrete research.

  4. Self-healing polymers---The importance of choosing an adequate healing monomer, and the olefin metathesis polymerization of agricultural oils

    NASA Astrophysics Data System (ADS)

    Mauldin, Timothy C.

    Modern society's immense and ill-fated reliance on petrochemical-based polymeric materials will likely necessitate a shift in polymer production paradigms in the near future. The work presented herein attempts to address this issue via a two-pronged approach. First, efforts to improve the duration of composite materials by incorporation of a self-healing function are discussed, the fruitful application of which can potentially reduce or eliminate the massive carbon footprints associated with the repair/replacement of damaged materials. And second, polymeric materials derived predominately from natural and renewable feedstock---namely vegetable oils---are developed. Early microcapsule-based self-healing materials utilized dicyclopentadiene-filled microcapsules and Grubbs' olefin metathesis catalyst to initiate the healing mechanism. However, the patent-protected catalyst, made from the precious metal ruthenium and sometimes costly ligands, will likely never be inexpensive and therefore limit large-scale applications. Hence, clever approaches to reduce the healing catalyst loading in self-healing polymers are of great interest. To this end, our efforts have revolved around solving the problem of the relatively inefficient use of Grubbs' catalyst during the healing mechanism. Given that the mismatch of the olefin metathesis polymerization and Grubbs' catalyst dissolution (in monomer) kinetics is a known cause of this inefficient use of the catalyst, we attempted to tune the "latency" (i.e. pot life) of the olefin metathesis polymerization to ensure more complete dissolution of catalyst in monomer. In an alternative approach to improving efficient catalyst dissolution, we developed a simple model to predict relative dissolution rates of Grubbs' catalyst in a small library of healing monomers. This model was shown experimentally to be able to aid in the selection of, for example, reactive monomer additives that can yield impressive improvements in catalyst dissolution

  5. Design of new disulfide-based organic compounds for the improvement of self-healing materials.

    PubMed

    Matxain, Jon M; Asua, José M; Ruipérez, Fernando

    2016-01-21

    Self-healing materials are a very promising kind of materials due to their capacity to repair themselves. Among others, diphenyl disulfide-based compounds (Ph2S2) appear to be among the best candidates to develop materials with optimum self-healing properties. However, few is known regarding both the reaction mechanism and the electronic structure that make possible such properties. In this vein, theoretical approaches are of great interest. In this work, we have carried out theoretical calculations on a wide set of different disulfide compounds, both aromatic and aliphatic, in order to elucidate the prevalent reaction mechanism and the necessary electronic conditions needed for improved self-healing properties. Two competitive mechanisms were considered, namely, the metathesis and the radical-mediated mechanism. According to our calculations, the radical-mediated mechanism is the responsible for this process. The formation of sulfenyl radicals strongly depends on the S-S bond strength, which can be modulated chemically by the use of proper derivatives. At this point, amino derivatives appear to be the most promising ones. In addition to the S-S bond strength, hydrogen bonding between disulfide chains seems to be relevant to favour the contact among disulfide units. This is crucial for the reaction to take place. The calculated hydrogen bonding energies are of the same order of magnitude as the S-S bond energies. Finally, reaction barriers have been analysed for some promising candidates. Two reaction mechanisms were compared, namely, the [2+2] metathesis reaction mechanism and the [2+1] radical-mediated mechanism. No computational evidence for the existence of any transition state for the metathesis mechanism was found, which indicates that the radical-mediated mechanism is the one responsible in the self-healing process of these materials. Interestingly, the calculated reaction barriers are around 10 kcal mol(-1) regardless the substituent employed. All these

  6. Design of new disulfide-based organic compounds for the improvement of self-healing materials.

    PubMed

    Matxain, Jon M; Asua, José M; Ruipérez, Fernando

    2016-01-21

    Self-healing materials are a very promising kind of materials due to their capacity to repair themselves. Among others, diphenyl disulfide-based compounds (Ph2S2) appear to be among the best candidates to develop materials with optimum self-healing properties. However, few is known regarding both the reaction mechanism and the electronic structure that make possible such properties. In this vein, theoretical approaches are of great interest. In this work, we have carried out theoretical calculations on a wide set of different disulfide compounds, both aromatic and aliphatic, in order to elucidate the prevalent reaction mechanism and the necessary electronic conditions needed for improved self-healing properties. Two competitive mechanisms were considered, namely, the metathesis and the radical-mediated mechanism. According to our calculations, the radical-mediated mechanism is the responsible for this process. The formation of sulfenyl radicals strongly depends on the S-S bond strength, which can be modulated chemically by the use of proper derivatives. At this point, amino derivatives appear to be the most promising ones. In addition to the S-S bond strength, hydrogen bonding between disulfide chains seems to be relevant to favour the contact among disulfide units. This is crucial for the reaction to take place. The calculated hydrogen bonding energies are of the same order of magnitude as the S-S bond energies. Finally, reaction barriers have been analysed for some promising candidates. Two reaction mechanisms were compared, namely, the [2+2] metathesis reaction mechanism and the [2+1] radical-mediated mechanism. No computational evidence for the existence of any transition state for the metathesis mechanism was found, which indicates that the radical-mediated mechanism is the one responsible in the self-healing process of these materials. Interestingly, the calculated reaction barriers are around 10 kcal mol(-1) regardless the substituent employed. All these

  7. Hierarchical Nacre Mimetics with Synergistic Mechanical Properties by Control of Molecular Interactions in Self-Healing Polymers.

    PubMed

    Zhu, Baolei; Jasinski, Nils; Benitez, Alejandro; Noack, Manuel; Park, Daesung; Goldmann, Anja S; Barner-Kowollik, Christopher; Walther, Andreas

    2015-07-20

    Designing the reversible interactions of biopolymers remains a grand challenge for an integral mimicry of mechanically superior biological composites. Yet, they are the key to synergistic combinations of stiffness and toughness by providing sacrificial bonds with hidden length scales. To address this challenge, dynamic polymers were designed with low glass-transition temperature T(g) and bonded by quadruple hydrogen-bonding motifs, and subsequently assembled with high-aspect-ratio synthetic nanoclays to generate nacre-mimetic films. The high dynamics and self-healing of the polymers render transparent films with a near-perfectly aligned structure. Varying the polymer composition allows molecular control over the mechanical properties up to very stiff and very strong films (E≈45 GPa, σ(UTS)≈270 MPa). Stable crack propagation and multiple toughening mechanisms occur in situations of balanced dynamics, enabling synergistic combinations of stiffness and toughness. Excellent gas barrier properties complement the multifunctional property profile. PMID:26095789

  8. Imaging studies of temperature dependent photodegradation and self-healing in disperse orange 11 dye-doped polymers

    NASA Astrophysics Data System (ADS)

    Anderson, Benjamin R.; Hung, Sheng-Ting; Kuzyk, Mark G.

    2016-07-01

    Using confocal transmission imaging microscopy, we measure the temperature dependence of photodegradation and self-healing in disperse orange 11 (DO11) dye-doped (poly)methyl-methacrylate (PMMA) and polystyrene (PS). In both dye-doped polymers, an increase in sample temperature results in a greater photodegradation rate and degree of degradation, while also resulting in a slower recovery rate and larger recovery fraction. These results confirm the temperature dependence predictions of the modified correlated chromophore domain model (mCCDM) [B. R. Anderson and M. G. Kuzyk, Phys. Rev. E 89, 032601 (2014)]. Additionally, using quantitative fitting of the imaging data for DO11/PMMA, we determine the domain density parameter to be ρ = 1.19 (±0.25) × 10-2 and the domain free energy advantage to be λ = 0.282 ± 0.015 eV, which are within the uncertainty of the values previously determined using amplified spontaneous emission as the probe method [S. K. Ramini et al., Polym. Chem. 4, 4948 (2013)]. Finally, while we find photodegradation and self-healing of DO11/PS to be qualitatively consistent with the mCCDM, we find that it is quantitatively incompatible with the mCCDM as recovery in DO11/PS is found to behave as a stretched (or double) exponential as a function of time.

  9. Imaging studies of temperature dependent photodegradation and self-healing in disperse orange 11 dye-doped polymers.

    PubMed

    Anderson, Benjamin R; Hung, Sheng-Ting; Kuzyk, Mark G

    2016-07-14

    Using confocal transmission imaging microscopy, we measure the temperature dependence of photodegradation and self-healing in disperse orange 11 (DO11) dye-doped (poly)methyl-methacrylate (PMMA) and polystyrene (PS). In both dye-doped polymers, an increase in sample temperature results in a greater photodegradation rate and degree of degradation, while also resulting in a slower recovery rate and larger recovery fraction. These results confirm the temperature dependence predictions of the modified correlated chromophore domain model (mCCDM) [B. R. Anderson and M. G. Kuzyk, Phys. Rev. E 89, 032601 (2014)]. Additionally, using quantitative fitting of the imaging data for DO11/PMMA, we determine the domain density parameter to be ρ = 1.19 (±0.25) × 10(-2) and the domain free energy advantage to be λ = 0.282 ± 0.015 eV, which are within the uncertainty of the values previously determined using amplified spontaneous emission as the probe method [S. K. Ramini et al., Polym. Chem. 4, 4948 (2013)]. Finally, while we find photodegradation and self-healing of DO11/PS to be qualitatively consistent with the mCCDM, we find that it is quantitatively incompatible with the mCCDM as recovery in DO11/PS is found to behave as a stretched (or double) exponential as a function of time. PMID:27421424

  10. Self-Healing Wire Insulation

    NASA Technical Reports Server (NTRS)

    Parrish, Clyde F. (Inventor)

    2012-01-01

    A self-healing system for an insulation material initiates a self-repair process by rupturing a plurality of microcapsules disposed on the insulation material. When the plurality of microcapsules are ruptured, reactants within the plurality of microcapsules react to form a replacement polymer in a break of the insulation material. This self-healing system has the ability to repair multiple breaks in a length of insulation material without exhausting the repair properties of the material.

  11. Development of a Mechanistic-Based Healing Model for Self-Healing Glass Seals

    SciTech Connect

    Xu, Wei; Stephens, Elizabeth V.; Sun, Xin; Khaleel, Mohammad A.; Zbib, Hussein M.

    2012-10-01

    Self-healing glass, a recent development of hermetic sealant materials, has the ability to effectively repair damage when heated to elevated temperatures; thus, able to extend its service life. Since crack healing morphological changes in the glass material are usually temperature and stress dependent, quantitative studies to determine the effects of thermo-mechanical conditions on the healing behavior of the self-healing glass sealants are extremely useful to accommodate the design and optimization of the sealing systems within SOFCs. The goal of this task is to develop a mechanistic-based healing model to quantify the stress and temperature dependent healing behavior. A two-step healing mechanism was developed and implemented into finite element (FE) models through user-subroutines. Integrated experimental/kinetic Monte Carlo (kMC) simulation methodology was taken to calibrate the model parameters. The crack healing model is able to investigate the effects of various thermo-mechanical factors; therefore, able to determine the critical conditions under which the healing mechanism will be activated. Furthermore, the predicted results can be used to formulate the continuum damage-healing model and to assist the SOFC stack level simulations in predicting and evaluating the effectiveness and the performance of various engineering seal designs.

  12. A galinstan-based inkjet printing system for highly stretchable electronics with self-healing capability.

    PubMed

    Li, Guangyong; Wu, Xuan; Lee, Dong-Weon

    2016-04-21

    We report a galinstan-based inkjet printing system to realize highly stretchable electronics with self-healing capability. The printing head made of polydimethylsiloxane (PDMS) consists of a main microfluidic channel and a coplanar channel. The main channel containing the oxidized galinstan is surrounded by the coplanar channel, which is filled with HCl. The HCl vapor effectively permeates the channel wall due to the high gas permeability of PDMS. The oxide skin of galinstan is consistently removed by chemical reaction with the HCl vapor. This allows one to maintain galinstan in a true liquid phase in the main channel. After the fabrication of the printing head with PDMS, the sizes of droplets ejected from the printing head with various flow rates have been characterized. The fabricated inkjet printing system is also utilized to generate complex galinstan patterns on various substrates. An LED-integrated circuit with self-healing capability shows excellent electrical and mechanical performance even after it is twisted more than 180° or stretched up to ∼60% more than 2000 times. The experimental results reveal that the proposed system has tremendous potential for stretchable electronic applications in the future. PMID:26987310

  13. Optimization of process factors for self-healing vanadium-based conversion coating on AZ31 magnesium alloy

    NASA Astrophysics Data System (ADS)

    Li, Kun; Liu, Junyao; Lei, Ting; Xiao, Tao

    2015-10-01

    A self-healing vanadium-based conversion coating was prepared on AZ31 magnesium alloy. The optimum operating conditions including vanadia solution concentration, pH and treating temperature for obtaining the best corrosion protective vanadia coatings and improved localized corrosion resistance to the magnesium substrate were determined by an orthogonal experiment design. Surface morphology and composition of the resultant conversion coatings were investigated by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). The self-healing behavior of the coating was investigated by cross-cut immersion test and electrochemical impedance spectroscopy (EIS) measurements in 3.5% NaCl solution.

  14. A Rule-Based Modeling for the Description of Flexible and Self-healing Business Processes

    NASA Astrophysics Data System (ADS)

    Boukhebouze, Mohamed; Amghar, Youssef; Benharkat, Aïcha-Nabila; Maamar, Zakaria

    In this paper we discuss the importance of ensuring that business processes are label robust and agile at the same time robust and agile. To this end, we consider reviewing the way business processes are managed. For instance we consider offering a flexible way to model processes so that changes in regulations are handled through some self-healing mechanisms. These changes may raise exceptions at run-time if not properly reflected on these processes. To this end we propose a new rule based model that adopts the ECA rules and is built upon formal tools. The business logic of a process can be summarized with a set of rules that implement an organization’s policies. Each business rule is formalized using our ECAPE formalism (Event-Condition-Action-Post condition- post Event). This formalism allows translating a process into a graph of rules that is analyzed in terms of reliably and flexibility.

  15. Self-Healing and Thermo-Responsive Dual-Crosslinked Alginate Hydrogels based on Supramolecular Inclusion Complexes

    PubMed Central

    Miao, Tianxin; Fenn, Spencer L.; Charron, Patrick N.; Oldinski, Rachael A.

    2015-01-01

    β-cyclodextrin (β-CD), with a lipophilic inner cavity and hydrophilic outer surface, interacts with a large variety of non-polar guest molecules to form non-covalent inclusion complexes. Conjugation of β-CD onto biomacromolecules can form physically-crosslinked hydrogel networks upon mixing with a guest molecule. Herein describes the development and characterization of self-healing, thermo-responsive hydrogels, based on host-guest inclusion complexes between alginate-graft-β-CD and Pluronic® F108 (poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol)). The mechanics, flow characteristics, and thermal response were contingent on the polymer concentrations, and the host-guest molar ratio. Transient and reversible physical crosslinking between host and guest polymers governed self-assembly, allowing flow under shear stress, and facilitating complete recovery of the material properties within a few seconds of unloading. The mechanical properties of the dual-crosslinked, multi-stimuli responsive hydrogels were tuned as high as 30 kPa at body temperature, and are advantageous for biomedical applications such as drug delivery and cell transplantation. PMID:26509214

  16. Self-healing of early age cracks in cement-based materials by mineralization of carbonic anhydrase microorganism

    PubMed Central

    Qian, Chunxiang; Chen, Huaicheng; Ren, Lifu; Luo, Mian

    2015-01-01

    This research investigated the self-healing potential of early age cracks in cement-based materials incorporating the bacteria which can produce carbonic anhydrase. Cement-based materials specimens were pre-cracked at the age of 7, 14, 28, 60 days to study the repair ability influenced by cracking time, the width of cracks were between 0.1 and 1.0 mm to study the healing rate influenced by width of cracks. The experimental results indicated that the bacteria showed excellent repairing ability to small cracks formed at early age of 7 days, cracks below 0.4 mm was almost completely closed. The repair effect reduced with the increasing of cracking age. Cracks width influenced self-healing effectiveness significantly. The transportation of CO2and Ca2+ controlled the self-healing process. The computer simulation analyses revealed the self-healing process and mechanism of microbiologically precipitation induced by bacteria and the depth of precipitated CaCO3 could be predicted base on valid Ca2+. PMID:26583014

  17. UV-Triggered Self-Healing of a Single Robust SiO2 Microcapsule Based on Cationic Polymerization for Potential Application in Aerospace Coatings.

    PubMed

    Guo, Wanchun; Jia, Yin; Tian, Kesong; Xu, Zhaopeng; Jiao, Jiao; Li, Ruifei; Wu, Yuehao; Cao, Ling; Wang, Haiyan

    2016-08-17

    UV-triggered self-healing of single microcapsules has been a good candidate to enhance the life of polymer-based aerospace coatings because of its rapid healing process and healing chemistry based on an accurate stoichiometric ratio. However, free radical photoinitiators used in single microcapsules commonly suffer from possible deactivation due to the presence of oxygen in the space environment. Moreover, entrapment of polymeric microcapsules into coatings often involves elevated temperature or a strong solvent, probably leading to swelling or degradation of polymer shell, and ultimately the loss of active healing species into the host matrix. We herein describe the first single robust SiO2 microcapsule self-healing system based on UV-triggered cationic polymerization for potential application in aerospace coatings. On the basis of the similarity of solubility parameters of the active healing species and the SiO2 precursor, the epoxy resin and cationic photoinitiator are successfully encapsulated into a single SiO2 microcapsule via a combined interfacial/in situ polymerization. The single SiO2 microcapsule shows solvent resistance and thermal stability, especially a strong resistance for thermal cycling in a simulated space environment. In addition, the up to 89% curing efficiency of the epoxy resin in 30 min, and the obvious filling of scratches in the epoxy matrix demonstrate the excellent UV-induced healing performance of SiO2 microcapsules, attributed to a high load of healing species within the capsule (up to 87 wt %) and healing chemistry based on an accurate stoichiometric ratio of the photoinitiator and epoxy resin at 9/100. More importantly, healing chemistry based on a UV-triggered cationic polymerization mechanism is not sensitive to oxygen, extremely facilitating future embedment of this single SiO2 microcapsule in spacecraft coatings to achieve self-healing in a space environment with abundant UV radiation and oxygen.

  18. UV-Triggered Self-Healing of a Single Robust SiO2 Microcapsule Based on Cationic Polymerization for Potential Application in Aerospace Coatings.

    PubMed

    Guo, Wanchun; Jia, Yin; Tian, Kesong; Xu, Zhaopeng; Jiao, Jiao; Li, Ruifei; Wu, Yuehao; Cao, Ling; Wang, Haiyan

    2016-08-17

    UV-triggered self-healing of single microcapsules has been a good candidate to enhance the life of polymer-based aerospace coatings because of its rapid healing process and healing chemistry based on an accurate stoichiometric ratio. However, free radical photoinitiators used in single microcapsules commonly suffer from possible deactivation due to the presence of oxygen in the space environment. Moreover, entrapment of polymeric microcapsules into coatings often involves elevated temperature or a strong solvent, probably leading to swelling or degradation of polymer shell, and ultimately the loss of active healing species into the host matrix. We herein describe the first single robust SiO2 microcapsule self-healing system based on UV-triggered cationic polymerization for potential application in aerospace coatings. On the basis of the similarity of solubility parameters of the active healing species and the SiO2 precursor, the epoxy resin and cationic photoinitiator are successfully encapsulated into a single SiO2 microcapsule via a combined interfacial/in situ polymerization. The single SiO2 microcapsule shows solvent resistance and thermal stability, especially a strong resistance for thermal cycling in a simulated space environment. In addition, the up to 89% curing efficiency of the epoxy resin in 30 min, and the obvious filling of scratches in the epoxy matrix demonstrate the excellent UV-induced healing performance of SiO2 microcapsules, attributed to a high load of healing species within the capsule (up to 87 wt %) and healing chemistry based on an accurate stoichiometric ratio of the photoinitiator and epoxy resin at 9/100. More importantly, healing chemistry based on a UV-triggered cationic polymerization mechanism is not sensitive to oxygen, extremely facilitating future embedment of this single SiO2 microcapsule in spacecraft coatings to achieve self-healing in a space environment with abundant UV radiation and oxygen. PMID:27463101

  19. Self-Healing Composite of Thermoset Polymer and Programmed Super Contraction Fibers

    NASA Technical Reports Server (NTRS)

    Li, Guoqiang (Inventor); Meng, Harper (Inventor)

    2016-01-01

    A composition comprising thermoset polymer, shape memory polymer to facilitate macro scale damage closure, and a thermoplastic polymer for molecular scale healing is disclosed; the composition has the ability to resolve structural defects by a bio-mimetic close-then heal process. In use, the shape memory polymer serves to bring surfaces of a structural defect into approximation, whereafter use of the thermoplastic polymer for molecular scale healing allowed for movement of the thermoplastic polymer into the defect and thus obtain molecular scale healing. The thermoplastic can be fibers, particles or spheres which are used by heating to a level at or above the thermoplastic's melting point, then cooling of the composition below the melting temperature of the thermoplastic. Compositions of the invention have the ability to not only close macroscopic defects, but also to do so repeatedly even if another wound/damage occurs in a previously healed/repaired area.

  20. Self-healing of drying shrinkage cracks in cement-based materials incorporating reactive MgO

    NASA Astrophysics Data System (ADS)

    Qureshi, T. S.; Al-Tabbaa, A.

    2016-08-01

    Excessive drying shrinkage is one of the major issues of concern for longevity and reduced strength performance of concrete structures. It can cause the formation of cracks in the concrete. This research aims to improve the autogenous self-healing capacity of traditional Portland cement (PC) systems, adding expansive minerals such as reactive magnesium oxide (MgO) in terms of drying shrinkage crack healing. Two different reactive grades (high ‘N50’and moderately high ‘92–200’) of MgO were added with PC. Cracks were induced in the samples with restraining end prisms through natural drying shrinkage over 28 days after casting. Samples were then cured under water for 28 and 56 days, and self-healing capacity was investigated in terms of mechanical strength recovery, crack sealing efficiency and improvement in durability. Finally, microstructures of the healing materials were investigated using FT-IR, XRD, and SEM-EDX. Overall N50 mixes show higher expansion and drying shrinkage compared to 92–200 mixes. Autogenous self-healing performance of the MgO containing samples were much higher compared to control (only PC) mixes. Cracks up to 500 μm were sealed in most MgO containing samples after 28 days. In the microstructural investigations, highly expansive Mg-rich hydro-carbonate bridges were found along with traditional calcium-based, self-healing compounds (calcite, portlandite, calcium silicate hydrates and ettringite).

  1. Self-healing of drying shrinkage cracks in cement-based materials incorporating reactive MgO

    NASA Astrophysics Data System (ADS)

    Qureshi, T. S.; Al-Tabbaa, A.

    2016-08-01

    Excessive drying shrinkage is one of the major issues of concern for longevity and reduced strength performance of concrete structures. It can cause the formation of cracks in the concrete. This research aims to improve the autogenous self-healing capacity of traditional Portland cement (PC) systems, adding expansive minerals such as reactive magnesium oxide (MgO) in terms of drying shrinkage crack healing. Two different reactive grades (high ‘N50’and moderately high ‘92-200’) of MgO were added with PC. Cracks were induced in the samples with restraining end prisms through natural drying shrinkage over 28 days after casting. Samples were then cured under water for 28 and 56 days, and self-healing capacity was investigated in terms of mechanical strength recovery, crack sealing efficiency and improvement in durability. Finally, microstructures of the healing materials were investigated using FT-IR, XRD, and SEM-EDX. Overall N50 mixes show higher expansion and drying shrinkage compared to 92-200 mixes. Autogenous self-healing performance of the MgO containing samples were much higher compared to control (only PC) mixes. Cracks up to 500 μm were sealed in most MgO containing samples after 28 days. In the microstructural investigations, highly expansive Mg-rich hydro-carbonate bridges were found along with traditional calcium-based, self-healing compounds (calcite, portlandite, calcium silicate hydrates and ettringite).

  2. Manganite-based three level memristive devices with self-healing capability

    NASA Astrophysics Data System (ADS)

    Acevedo, W. Román; Rubi, D.; Lecourt, J.; Lüders, U.; Gomez-Marlasca, F.; Granell, P.; Golmar, F.; Levy, P.

    2016-08-01

    We report on non-volatile memory devices based on multifunctional manganites. The electric field induced resistive switching of Ti/La1/3Ca2/3MnO3/n-Si devices is explored using different measurement protocols. We show that using current as the electrical stimulus (instead of standard voltage-controlled protocols) improves the electrical performance of our devices and unveils an intermediate resistance state. We observe three discrete resistance levels (low, intermediate and high), which can be set either by the application of current-voltage ramps or by means of single pulses. These states exhibit retention and endurance capabilities exceeding 104 s and 70 cycles, respectively. We rationalize our experimental observations by proposing a mixed scenario were a metallic filament and a SiOx layer coexist, accounting for the observed resistive switching. Overall electrode area dependence and temperature dependent resistance measurements support our scenario. After device failure takes place, the system can be turned functional again by heating up to low temperature (120 °C), a feature that could be exploited for the design of memristive devices with self-healing functionality. These results give insight into the existence of multiple resistive switching mechanisms in manganite-based memristive systems and provide strategies for controlling them.

  3. An Assessment of Self-Healing Fiber Reinforced Composites

    NASA Technical Reports Server (NTRS)

    Smith, Joseph G., Jr.

    2012-01-01

    Several reviews and books have been written concerning self-healing polymers over the last few years. These have focused primarily on the types of self-healing materials being studied, with minor emphasis given to composite properties. The purpose of this review is to assess the self-healing ability of these materials when utilized in fiber reinforced composites

  4. Injectable and Self-Healing Dynamic Hydrogels Based on Metal(I)-Thiolate/Disulfide Exchange as Biomaterials with Tunable Mechanical Properties.

    PubMed

    Casuso, Pablo; Odriozola, Ibon; Pérez-San Vicente, Adrián; Loinaz, Iraida; Cabañero, Germán; Grande, Hans-Jürgen; Dupin, Damien

    2015-11-01

    Despite numerous strategies involving dynamic covalent bonds to produce self-healing hydrogels with similar frequency-dependent stiffness to native tissues, it remains challenging to use biologically relevant thiol/disulfide exchange to confer such properties to polymeric networks. Herein, we report a new method based on Metal(I) [Au(I) or Ag(I)] capping to protect thiolates from aerial oxidation without preventing thiolate/disulfide exchange. Dynamic hydrogels were readily prepared by injecting simultaneously aqueous solutions of commercially available HAuCl4 and 4-arm thiol-terminated polyethylene glycol [(PEGSH)4], resulting in a network containing a mixture of Au(I)-thiolate (Au-S) and disulfide bonds (SS). While the dynamic properties of the hydrogel were closely dependent on the pH, the mechanical properties could be easily tuned by adjusting (PEGSH)4 concentration and amount of Au-S, as judged by dynamic rheology studies. Permanent Au-S/SS exchange at physiological pH conferred self-healing behavior and frequency-dependent stiffness to the hydrogel. In addition, in vitro studies confirmed that Au-based dynamic material was not cytotoxic to human dermal fibroblasts, demonstrating its potential use as a medical device. Dynamic hydrogels obtained using Ag(I) ions demonstrated that the exchange reaction was not affected by the nature of the Metal(I) capping. Finally, this efficient thiolate capping strategy offers a simple way to produce injectable and self-healing dynamic hydrogels from virtually any thiol-containing polymers. PMID:26418440

  5. Dual self-healing abilities of composite gels consisting of polymer-brush-afforded particles and an azobenzene-doped liquid crystal.

    PubMed

    Kawata, Yuki; Yamamoto, Takahiro; Kihara, Hideyuki; Ohno, Kohji

    2015-02-25

    We prepared the composite gels from polymer-brush-afforded silica particles (P-SiPs) and an azobenzene-doped liquid crystal, and investigated their inner structure, dynamic viscoelastic properties, thermo- and photoresponsive properties, and self-healing behaviors. It was found that the composite gels had a sponge-like inner structure formed with P-SiPs and exhibited good elastic property and shape recoverability. The surface dents made on the composite gel could be repaired spontaneously at room temperature. Moreover, the composite gel exhibited a gel-sol transition induced by the trans-cis photoisomerization of the azo dye, and the transition could be used as a mending mechanism for surface cracks. Consequently, we successfully developed a material exhibiting two types of self-healing abilities simultaneously: (1) spontaneous repair of surface dents by means of the excellent elasticity of the composite gel and (2) light-assisted mending of surface cracks by photoinduced gel-sol transition.

  6. An Implicational View of Self-Healing and Personality Change Based on Gendlin's Theory of Experiencing.

    ERIC Educational Resources Information Center

    Bohart, Arthur C.

    There is relatively little theory on how psychotherapy clients self-heal since most theories of therapy stress the magic of the therapist's interventions. Of the theories that exist, this paper briefly discusses Carl Rogers' theory of self-actualization; and the dialectical theories of Greenberg and his colleagues, Jenkins, and Rychlak. Gendlin's…

  7. Self-healing mortar with pH-sensitive superabsorbent polymers: testing of the sealing efficiency by water flow tests

    NASA Astrophysics Data System (ADS)

    Gruyaert, Elke; Debbaut, Brenda; Snoeck, Didier; Díaz, Pilar; Arizo, Alejandro; Tziviloglou, Eirini; Schlangen, Erik; De Belie, Nele

    2016-08-01

    Superabsorbent polymers (SAPs) have potential to be used as healing agent in self-healing concrete due to their property to attract moisture from the environment and their capacity to promote autogenous healing. A possible drawback, however, is their uptake of mixing water during concrete manufacturing, resulting in an increased volume of macro-pores in the hardened concrete. To limit this drawback, newly developed SAPs with a high swelling and pH-sensitiveness were developed and tested within the FP7 project HEALCON. Evaluation of their self-sealing performance occurred through a water permeability test via water flow, a test method also developed within HEALCON. Three different sizes of the newly developed SAP were compared with a commercial SAP. Swelling tests in cement filtrate solution indicated that the commercial and in-house synthesized SAPs performed quite similar, but the difference between the swelling capacity at pH 9 and pH 13 is more pronounced for the self-synthesized SAPs. Moreover, in comparison to the commercial SAPs, less macro-pores are formed in the cement matrix of mixes with self-synthesized SAPs and the effect on the mechanical properties is lower, but not negligible, when using high amounts of SAPs. Although the immediate sealing effect of cracks in mortar was the highest for the commercial SAPs, the in-house made SAPs with a particle size between 400 and 600 μm performed the best with regard to crack closure (mainly CaCO3 precipitation) and self-sealing efficiency, after exposing the specimens to 28 wet-dry cycles. Some specimens could even withstand a water pressure of 2 bar.

  8. Self-healing mortar with pH-sensitive superabsorbent polymers: testing of the sealing efficiency by water flow tests

    NASA Astrophysics Data System (ADS)

    Gruyaert, Elke; Debbaut, Brenda; Snoeck, Didier; Díaz, Pilar; Arizo, Alejandro; Tziviloglou, Eirini; Schlangen, Erik; De Belie, Nele

    2016-08-01

    Superabsorbent polymers (SAPs) have potential to be used as healing agent in self-healing concrete due to their property to attract moisture from the environment and their capacity to promote autogenous healing. A possible drawback, however, is their uptake of mixing water during concrete manufacturing, resulting in an increased volume of macro-pores in the hardened concrete. To limit this drawback, newly developed SAPs with a high swelling and pH-sensitiveness were developed and tested within the FP7 project HEALCON. Evaluation of their self-sealing performance occurred through a water permeability test via water flow, a test method also developed within HEALCON. Three different sizes of the newly developed SAP were compared with a commercial SAP. Swelling tests in cement filtrate solution indicated that the commercial and in-house synthesized SAPs performed quite similar, but the difference between the swelling capacity at pH 9 and pH 13 is more pronounced for the self-synthesized SAPs. Moreover, in comparison to the commercial SAPs, less macro-pores are formed in the cement matrix of mixes with self-synthesized SAPs and the effect on the mechanical properties is lower, but not negligible, when using high amounts of SAPs. Although the immediate sealing effect of cracks in mortar was the highest for the commercial SAPs, the in-house made SAPs with a particle size between 400 and 600 μm performed the best with regard to crack closure (mainly CaCO3 precipitation) and self-sealing efficiency, after exposing the specimens to 28 wet–dry cycles. Some specimens could even withstand a water pressure of 2 bar.

  9. A Mechanistic-Based Healing Model for Self-Healing Glass Seals Used in Solid Oxide Fuel Cells

    SciTech Connect

    Xu, Wei; Sun, Xin; Stephens, Elizabeth V.; Mastorakos, Ioannis; Khaleel, Mohammad A.; Zbib, Hussein M.

    2012-09-01

    The usage of self-healing glass as hermetic seals is a recent advancement in sealing technology development for the planar solid oxide fuel cells (SOFCs). Because of its capability of restoring the mechanical properties at elevated temperatures, the self-healing glass seal is expected to provide high reliability in maintaining the long-term structural integrity and functionality of SOFCs. In order to accommodate the design and to evaluate the effectiveness of such engineering seals under various thermo-mechanical operating conditions, computational modeling framework needs to be developed to accurately capture and predict the healing behavior of the glass material. In the present work, a mechanistic-based two-stage model was developed to study the stress and temperature-dependent crack healing of the self-healing glass materials. The model was first calibrated by experimental measurements combined with the kinetic Monte Carlo (kMC) simulation results and then implemented into the finite element analysis (FEA). The effects of various factors, i.e. stress, temperature, crack morphology, on the healing behavior of the glass were investigated and discussed.

  10. Application of a silver-olefin coordination polymer as a catalytic curing agent for self-healing epoxy polymers

    NASA Astrophysics Data System (ADS)

    Everitt, D. T.; Coope, T. S.; Trask, R. S.; Wass, D. F.; Bond, I. P.

    2015-05-01

    A silver-olefin based coordination polymer was prepared in a simple, one step process to act as an initiator to facilitate the ring-opening polymerization of epoxides. Thermal analysis found the complex to be capable of curing a range of commercially available epoxy resins used in the manufacture of conventional composite materials. Curing of the oligomeric diglycidyl ether bisphenol A resin, Epon 828, in combination with a non-toxic solvent, ethyl phenylacetate, was studied by differential scanning calorimetry. The mechanical characterization of the resultant cured polymers was conducted by single lap shear tests. Tapered double cantilever beam (TDCB) test specimens containing 2.5 pph of silver-olefin initiator, both with and without embedded microcapsules, were analyzed for their healing performance. Healing efficiency values were found to be strongly dependent on the applied healing temperature. A mean recovery of 74% fracture load was found in TDCB samples after being healed at 70 °C for 48 h.

  11. Self-Healing of biocompatible polymeric nanocomposities

    NASA Astrophysics Data System (ADS)

    Espino, Omar; Chipara, Dorina

    2014-03-01

    Polymers are vulnerable to damage in form of cracks deep within the structure, where detection is difficult and repair is near to impossible. These cracks lead to mechanical degradation of the polymer. A method has been created to solve this problem named polymeric self healing. Self healing capabilities implies the dispersion within the polymeric matrix of microcapsules filled with a monomer and of catalyst. Poly urea-formaldehyde microcapsules used in this method are filled with dicyclopentadiene that is liberated after being ruptured by the crack propagation in the material. Polymerization is assisted by a catalyst FGGC that ignites the self healing process. Nanocomposites, such as titanium oxide, will be used as an integration of these polymers that will be tested by rupturing mechanically slowly. In order to prove the self healing process, Raman spectroscopy, FTIR, and SEM are used.

  12. Self-Healing Underwater Superoleophobic and Antibiofouling Coatings Based on the Assembly of Hierarchical Microgel Spheres.

    PubMed

    Chen, Kunlin; Zhou, Shuxue; Wu, Limin

    2016-01-26

    Marine biofouling has been plaguing people for thousands of years. While various strategies have been developed for antifouling (including superoleophobic) coatings, none of these exhibits self-healing properties because the bestowal of a zoetic self-repairing function to lifeless artificial water/solid interfacial materials is usually confronted with tremendous challenges. Here, we present a self-repairing underwater superoleophobic and antibiofouling coating through the self-assembly of hydrophilic polymeric chain modified hierarchical microgel spheres. The obtained surface material not only has excellent underwater superoleophobicity but also has very good subaqueous antibiofouling properties. More importantly, this surface material can recover the oil- and biofouling-resistant properties once its surface is mechanically damaged, similar to the skins of some marine organisms such as sharks or whales. This approach is feasible and easily mass-produced and could open a pathway and possibility for the fabrication of other self-healing functional water/solid interfacial materials. PMID:26687925

  13. Self-healing minefield

    NASA Astrophysics Data System (ADS)

    Rolader, Glenn E.; Rogers, John; Batteh, Jad

    2004-07-01

    The Self Healing Minefield (SHM) is comprised of a networked system of mobile anti-tank landmines. When the mines detect a breach, each calculates an appropriate response, and some fire small rockets to "hop" into the breach path, healing the breach. The purpose of the SHM is to expand the capabilities of traditional obstacles and provide an effective anti-tank obstacle that does not require Anti-Personnel (AP) submunitions. The DARPA/ATO sponsored program started in June 2000 and culminated in a full 100-unit demonstration at Fort Leonard Wood, MO in April 2003. That program went from "a concept" to a prototype system demonstration in approximately 21 months and to a full tactically significant demonstration in approximately 33 months. Significant accomplishments included the following: (1) Demonstration of a working, scalable (order of a hundred nodes), ad hoc, self-healing RF network. (2) Demonstration of an innovative distributed time synchronization scheme that does not rely on GPS. (3) Demonstration of a non-GPS based, self-mapping, relative geolocation system. (4) Development of an innovative distributed safe, arm, and fire system that allows for independent firing of eight rockets within a single node. (5) Development of a small rocket design with a novel geometry that meets the propulsion requirements.

  14. Self-healing biomaterials.

    PubMed

    Brochu, Alice B W; Craig, Stephen L; Reichert, William M

    2011-02-01

    The goal of this review is to introduce the biomaterials community to the emerging field of self-healing materials, and also to suggest how one could utilize and modify self-healing approaches to develop new classes of biomaterials. A brief discussion of the in vivo mechanical loading and resultant failures experienced by biomedical implants is followed by presentation of the self-healing methods for combating mechanical failure. If conventional composite materials that retard failure may be considered zeroth generation self-healing materials, then taxonomically speaking, first generation self-healing materials describe approaches that "halt" and "fill" damage, whereas second generation self-healing materials strive to "fully restore" the prefailed material structure. In spite of limited commercial use to date, primarily because the technical details have not been suitably optimized, it is likely from a practical standpoint that first generation approaches will be the first to be employed commercially, whereas second generation approaches may take longer to implement. For self-healing biomaterials the optimization of technical considerations is further compounded by the additional constraints of toxicity and biocompatibility, necessitating inclusion of separate discussions of design criteria for self-healing biomaterials.

  15. Self Healing Percolation

    NASA Astrophysics Data System (ADS)

    Scala, Antonio

    2015-03-01

    We introduce the concept of self-healing in the field of complex networks modelling; in particular, self-healing capabilities are implemented through distributed communication protocols that exploit redundant links to recover the connectivity of the system. Self-healing is a crucial in implementing the next generation of smart grids allowing to ensure a high quality of service to the users. We then map our self-healing procedure in a percolation problem and analyse the interplay between redundancies and topology in improving the resilience of networked infrastructures to multiple failures. We find exact results both for planar lattices and for random lattices, hinting the role of duality in the design of resilient networks. Finally, we introduce a cavity method approach to study the recovery of connectivity after damage in self-healing networks. CNR-PNR National Project ``Crisis-Lab,'' EU HOME/2013/CIPS/AG/4000005013 project CI2C and EU FET project MULTIPLEX nr.317532.

  16. On the use of crystalline admixtures in cement based construction materials: from porosity reducers to promoters of self healing

    NASA Astrophysics Data System (ADS)

    Ferrara, Liberato; Krelani, Visar; Moretti, Fabio

    2016-08-01

    The project detailed in this paper aims at a thorough characterization of the effects of crystalline admixtures, currently employed as porosity reducing admixtures, on the self-healing capacity of the cementitious composites, i.e. their capacity to completely or partially re-seal cracks and, in case, also exhibit recovery of mechanical properties. The problem has been investigated with reference to both a normal strength concrete (NSC) and a high performance fibre reinforced cementitious composite (HPFRCC). In the latter case, the influence of flow-induced fibre alignment has also been considered in the experimental investigation. With reference to either 3-point (for NSC) or 4-point (for HPFRCC) bending tests performed up to controlled crack opening and up to failure, respectively before and after exposure/conditioning recovery of stiffness and stress bearing capacity has been evaluated to assess the self-healing capacity. In a durability-based design framework, self-healing indices to quantify the recovery of mechanical properties will also be defined. In NSC, crystalline admixtures are able to promote up to 60% of crack sealing even under exposure to open air. In the case of HPFRCCs, which would already feature autogenous healing capacity because of their peculiar mix compositions, the synergy between the dispersed fibre reinforcement and the action of the crystalline admixture has resulted in a likely ‘chemical pre-stressing’ of the same reinforcement, from which the recovery of mechanical performance of the material has greatly benefited, up to levels even higher than the performance of the virgin un-cracked material.

  17. Fatigue of Self-Healing Nanofiber-based Composites: Static Test and Subcritical Crack Propagation.

    PubMed

    Lee, Min Wook; Sett, Soumyadip; Yoon, Sam S; Yarin, Alexander L

    2016-07-20

    Here, we studied the self-healing of composite materials filled with epoxy-containing nanofibers. An initial incision in the middle of a composite sample stretched in a static fatigue test can result in either crack propagation or healing. In this study, crack evolution was observed in real time. A binary epoxy, which acted as a self-healing agent, was encapsulated in two separate types of interwoven nano/microfibers formed by dual-solution blowing, with the core containing either epoxy or hardener and the shell being formed from poly(vinylidene fluoride)/ poly(ethylene oxide) mixture. The core-shell fibers were encased in a poly(dimethylsiloxane) matrix. When the fibers were damaged by a growing crack in this fiber-reinforced composite material because of static stretching in the fatigue test, they broke and released the healing agent into the crack area. The epoxy used in this study was cured and solidified for approximately an hour at room temperature, which then conglutinated and healed the damaged location. The observations were made for at least several hours and in some cases up to several days. It was revealed that the presence of the healing agent (the epoxy) in the fibers successfully prevented the propagation of cracks in stretched samples subjected to the fatigue test. A theoretical analysis of subcritical cracks was performed, and it revealed a jumplike growth of subcritical cracks, which was in qualitative agreement with the experimental results. PMID:27332924

  18. Exponential Arithmetic Based Self-Healing Group Key Distribution Scheme with Backward Secrecy under the Resource-Constrained Wireless Networks

    PubMed Central

    Guo, Hua; Zheng, Yandong; Zhang, Xiyong; Li, Zhoujun

    2016-01-01

    In resource-constrained wireless networks, resources such as storage space and communication bandwidth are limited. To guarantee secure communication in resource-constrained wireless networks, group keys should be distributed to users. The self-healing group key distribution (SGKD) scheme is a promising cryptographic tool, which can be used to distribute and update the group key for the secure group communication over unreliable wireless networks. Among all known SGKD schemes, exponential arithmetic based SGKD (E-SGKD) schemes reduce the storage overhead to constant, thus is suitable for the the resource-constrained wireless networks. In this paper, we provide a new mechanism to achieve E-SGKD schemes with backward secrecy. We first propose a basic E-SGKD scheme based on a known polynomial-based SGKD, where it has optimal storage overhead while having no backward secrecy. To obtain the backward secrecy and reduce the communication overhead, we introduce a novel approach for message broadcasting and self-healing. Compared with other E-SGKD schemes, our new E-SGKD scheme has the optimal storage overhead, high communication efficiency and satisfactory security. The simulation results in Zigbee-based networks show that the proposed scheme is suitable for the resource-restrained wireless networks. Finally, we show the application of our proposed scheme. PMID:27136550

  19. Exponential Arithmetic Based Self-Healing Group Key Distribution Scheme with Backward Secrecy under the Resource-Constrained Wireless Networks.

    PubMed

    Guo, Hua; Zheng, Yandong; Zhang, Xiyong; Li, Zhoujun

    2016-04-28

    In resource-constrained wireless networks, resources such as storage space and communication bandwidth are limited. To guarantee secure communication in resource-constrained wireless networks, group keys should be distributed to users. The self-healing group key distribution (SGKD) scheme is a promising cryptographic tool, which can be used to distribute and update the group key for the secure group communication over unreliable wireless networks. Among all known SGKD schemes, exponential arithmetic based SGKD (E-SGKD) schemes reduce the storage overhead to constant, thus is suitable for the the resource-constrained wireless networks. In this paper, we provide a new mechanism to achieve E-SGKD schemes with backward secrecy. We first propose a basic E-SGKD scheme based on a known polynomial-based SGKD, where it has optimal storage overhead while having no backward secrecy. To obtain the backward secrecy and reduce the communication overhead, we introduce a novel approach for message broadcasting and self-healing. Compared with other E-SGKD schemes, our new E-SGKD scheme has the optimal storage overhead, high communication efficiency and satisfactory security. The simulation results in Zigbee-based networks show that the proposed scheme is suitable for the resource-restrained wireless networks. Finally, we show the application of our proposed scheme.

  20. Exponential Arithmetic Based Self-Healing Group Key Distribution Scheme with Backward Secrecy under the Resource-Constrained Wireless Networks.

    PubMed

    Guo, Hua; Zheng, Yandong; Zhang, Xiyong; Li, Zhoujun

    2016-01-01

    In resource-constrained wireless networks, resources such as storage space and communication bandwidth are limited. To guarantee secure communication in resource-constrained wireless networks, group keys should be distributed to users. The self-healing group key distribution (SGKD) scheme is a promising cryptographic tool, which can be used to distribute and update the group key for the secure group communication over unreliable wireless networks. Among all known SGKD schemes, exponential arithmetic based SGKD (E-SGKD) schemes reduce the storage overhead to constant, thus is suitable for the the resource-constrained wireless networks. In this paper, we provide a new mechanism to achieve E-SGKD schemes with backward secrecy. We first propose a basic E-SGKD scheme based on a known polynomial-based SGKD, where it has optimal storage overhead while having no backward secrecy. To obtain the backward secrecy and reduce the communication overhead, we introduce a novel approach for message broadcasting and self-healing. Compared with other E-SGKD schemes, our new E-SGKD scheme has the optimal storage overhead, high communication efficiency and satisfactory security. The simulation results in Zigbee-based networks show that the proposed scheme is suitable for the resource-restrained wireless networks. Finally, we show the application of our proposed scheme. PMID:27136550

  1. Progress in the remote-controlled activation of self-healing processes

    NASA Astrophysics Data System (ADS)

    Shaaban, Ahmad; Schmidt, Annette M.

    2016-08-01

    Self-healing materials, able to heal themselves either spontaneously or after activation, and ultimately restore diverse properties such as mechanical, optical or electrical properties, are under intense investigation for various classes of material, including polymers, cementous materials, asphalts, metals, composites, and more. Among these, on-command self-healing systems can be classified as an approach towards a spatially resolved, externally controlled activation of self-healing behavior. Towards this goal, the last decade has experienced significant progress. Various methods, mainly based on indirect heating mechanisms, such as resistive, induction, or photo-induced heating, have been presented, depending on different antenna materials and energy sources, and tailored for different applications. This review discusses the up-to-date achievements in the field of on-command self-healing materials with a focus on electromagnetic and mechanochemical activation.

  2. Dual self-healing abilities of composite gels consisting of polymer-brush-afforded particles and an azobenzene-doped liquid crystal.

    PubMed

    Kawata, Yuki; Yamamoto, Takahiro; Kihara, Hideyuki; Ohno, Kohji

    2015-02-25

    We prepared the composite gels from polymer-brush-afforded silica particles (P-SiPs) and an azobenzene-doped liquid crystal, and investigated their inner structure, dynamic viscoelastic properties, thermo- and photoresponsive properties, and self-healing behaviors. It was found that the composite gels had a sponge-like inner structure formed with P-SiPs and exhibited good elastic property and shape recoverability. The surface dents made on the composite gel could be repaired spontaneously at room temperature. Moreover, the composite gel exhibited a gel-sol transition induced by the trans-cis photoisomerization of the azo dye, and the transition could be used as a mending mechanism for surface cracks. Consequently, we successfully developed a material exhibiting two types of self-healing abilities simultaneously: (1) spontaneous repair of surface dents by means of the excellent elasticity of the composite gel and (2) light-assisted mending of surface cracks by photoinduced gel-sol transition. PMID:25686486

  3. pH-induced metal-ligand cross-links inspired by mussel yield self-healing polymer networks with near-covalent elastic moduli

    PubMed Central

    Holten-Andersen, Niels; Harrington, Matthew J.; Birkedal, Henrik; Lee, Bruce P.; Messersmith, Phillip B.; Lee, Ka Yee C.; Waite, J. Herbert

    2011-01-01

    Growing evidence supports a critical role of metal-ligand coordination in many attributes of biological materials including adhesion, self-assembly, toughness, and hardness without mineralization [Rubin DJ, Miserez A, Waite JH (2010) Advances in Insect Physiology: Insect Integument and Color, eds Jérôme C, Stephen JS (Academic Press, London), pp 75–133]. Coordination between Fe and catechol ligands has recently been correlated to the hardness and high extensibility of the cuticle of mussel byssal threads and proposed to endow self-healing properties [Harrington MJ, Masic A, Holten-Andersen N, Waite JH, Fratzl P (2010) Science 328:216–220]. Inspired by the pH jump experienced by proteins during maturation of a mussel byssus secretion, we have developed a simple method to control catechol-Fe3+ interpolymer cross-linking via pH. The resonance Raman signature of catechol-Fe3+ cross-linked polymer gels at high pH was similar to that from native mussel thread cuticle and the gels displayed elastic moduli (G′) that approach covalently cross-linked gels as well as self-healing properties. PMID:21278337

  4. Self-healing materials with microvascular networks.

    PubMed

    Toohey, Kathleen S; Sottos, Nancy R; Lewis, Jennifer A; Moore, Jeffrey S; White, Scott R

    2007-08-01

    Self-healing polymers composed of microencapsulated healing agents exhibit remarkable mechanical performance and regenerative ability, but are limited to autonomic repair of a single damage event in a given location. Self-healing is triggered by crack-induced rupture of the embedded capsules; thus, once a localized region is depleted of healing agent, further repair is precluded. Re-mendable polymers can achieve multiple healing cycles, but require external intervention in the form of heat treatment and applied pressure. Here, we report a self-healing system capable of autonomously repairing repeated damage events. Our bio-inspired coating-substrate design delivers healing agent to cracks in a polymer coating via a three-dimensional microvascular network embedded in the substrate. Crack damage in the epoxy coating is healed repeatedly. This approach opens new avenues for continuous delivery of healing agents for self-repair as well as other active species for additional functionality.

  5. Solitary Type of Congenital Self-healing Reticulohistiocytosis

    PubMed Central

    Dorjsuren, Gantsetseg; Kim, Hee Jung; Jung, Jin Young; Bae, Byung Gi

    2011-01-01

    Congenital self-healing reticulohistiocytosis is a rare, congenital, benign, self-healing variant of Langerhans cell histiocytosis. It usually appears as multiple papules or nodules; however, occurrence of the solitary type is very rare. We report on a case of solitary congenital self-healing reticulohistiocytosis in a 29-day-old girl who presented with a papule on her sole. Two months later, the lesion regressed with a slight scar. Based upon clinical and histologic findings, we made a diagnosis of solitary congenital self-healing reticulohistiocytosis. In this report, we summarized reported cases of solitary congenital self-healing retioculohistiocytosis in Korea with a review of the literature. PMID:22028569

  6. Centrally controlled self-healing wavelength division multiplexing passive optical network based on optical carrier suppression technique

    NASA Astrophysics Data System (ADS)

    Zhu, Min; Zhang, Jiao; Sun, Xiaohan

    2015-12-01

    We proposed and demonstrated a centrally controlled and self-healing wavelength division multiplexing passive optical network with colorless optical network units (ONUs) based on optical carrier suppression technique. By switching the affected data in the OCS signal sideband to an alternate protection path, only one optical switch is provisioned at the optical line terminal, which is controlled by a logic control circuit upon monitoring of power outage on the working path. The proposed scheme can reliably protect against both distribution and feeder fiber failures. Moreover, gain-saturated reflective semiconductor optical amplifiers are used as colorless transmitters in ONUs. The protection scheme feasibility and system performances are experimentally verified with 10 Gb/s downstream and 1.25 Gb/s upstream data in both working and protection modes. The protection switching time was measured to be around 1 ms.

  7. Biomimetic Self-Healing.

    PubMed

    Diesendruck, Charles E; Sottos, Nancy R; Moore, Jeffrey S; White, Scott R

    2015-09-01

    Self-healing is a natural process common to all living organisms which provides increased longevity and the ability to adapt to changes in the environment. Inspired by this fitness-enhancing functionality, which was tuned by billions of years of evolution, scientists and engineers have been incorporating self-healing capabilities into synthetic materials. By mimicking mechanically triggered chemistry as well as the storage and delivery of liquid reagents, new materials have been developed with extended longevity that are capable of restoring mechanical integrity and additional functions after being damaged. This Review describes the fundamental steps in this new field of science, which combines chemistry, physics, materials science, and mechanical engineering.

  8. Self-healing vs. Crack-like Rupture Propagation in Presence of Thermal Weakening Processes Based on Realistic Physical Properties

    NASA Astrophysics Data System (ADS)

    Noda, H.; Dunham, E. M.; Rice, J. R.

    2006-12-01

    friction level. Our calculations show that the effect of evolving changes in T and p is to extend the crack-like (vs. self-healing) solution regime in the parameter space, although we are still examining the way nucleation may interact with rupture mode. Given a steady state shear stress which is a function only of slip rate, Zheng and Rice [BSSA, 1998] derive a critical background shear stress, τpulse, below which a growing crack-like solution does not exist for mode III rupture. In our case, such a steady-state function cannot be defined due to strength dependency on T and p. We then can obtain crack-like solutions with background shear stress lower than τpulse defined by the ZR concept based on steady-state flash heating only, at the initial T and p. With decreasing background shear stress, the type of solution changes from crack-like to self-healing after a clear threshold. The flash heating constitutive relation has steep velocity weakening around its critical slip rate, which effectively decelerates fault motion in the cases of self-healing solutions. By changing hydraulic parameters, the threshold background shear stress between the two types of solutions changes so that low hydro-thermal diffusivity favors crack-like solutions. The size of perturbation also matters and a larger (in length or amplitude) perturbation favors crack-like solutions.

  9. Silicone-based tough hydrogels with high resilience, fast self-recovery, and self-healing properties.

    PubMed

    Si, Liqi; Zheng, Xiaowen; Nie, Jun; Yin, Ruixue; Hua, Yujie; Zhu, Xiaoqun

    2016-06-28

    Tough hydrogels are prepared from two monomers via photopolymerization of hydroxyethyl acrylate and sol-gel of methyltrimethoxysilane. Constitution and water content could be tuned easily because of the good water solubility of both monomers and two non-interfering polymerization processes. The hydrogels exhibit excellent integrated performance with toughness, high resilience, fast self-recovery, and self-healing. PMID:27257636

  10. Self-healing of hierarchical materials.

    PubMed

    Bosia, Federico; Abdalrahman, Tamer; Pugno, Nicola M

    2014-02-01

    We present a theoretical and numerical analysis of the mechanical behavior of self-healing materials using an analytical model and numerical calculations both based on a Hierarchical Fiber Bundle Model, and applying them to graphene- or carbon-nanotube-based materials. The self-healing process can be described essentially through a single parameter, that is, the healing rate, but numerical simulations also highlight the influence of the location of the healing process on the overall strengthening and toughening of the material. The role of hierarchy is discussed, showing that full-scale hierarchical structures can in fact acquire more favorable properties than smaller, nonhierarchical ones through interaction with the self-healing process, thus inverting the common notion in fracture mechanics that specimen strength increases with decreasing size. Further, the study demonstrates that the developed analytical and numerical tools can be useful to develop strategies for the optimization of strength and toughness of synthetic bioinspired materials. PMID:24364755

  11. Base metal alloys with self-healing native conductive oxides for electrical contact materials

    NASA Astrophysics Data System (ADS)

    Aindow, M.; Alpay, S. P.; Liu, Y.; Mantese, J. V.; Senturk, B. S.

    2010-10-01

    Base metals for electrical contacts exhibit high bulk conductivities but form low-conductivity native oxide scales in air, leading to unacceptably high contact resistances. Here we show that alloying base metals can lead to higher conductivity native scales by: doping to enhance carrier concentration; inducing mixed oxidation states to give electron/polaron hopping; and/or phase separation for conducting pathways. Data from Cu-La, Fe-V, and Ni-Ru alloys demonstrate the viability of these approaches, yielding contact resistances up to 106 times lower than that for oxidized Cu.

  12. Self-healing biomaterials(3)

    PubMed Central

    Brochu, Alice B. W.; Craig, Stephen L.; Reichert, William M.

    2010-01-01

    The goal of this review is to introduce the biomaterials community to the emerging field of self-healing materials, and also to suggest how one could utilize and modify self-healing approaches to develop new classes of biomaterials. A brief discussion of the in vivo mechanical loading and resultant failures experienced by biomedical implants is followed by presentation of the self-healing methods for combating mechanical failure. If conventional composite materials that retard failure may be considered zeroth generation self-healing materials, then taxonomically-speaking, first generation self-healing materials describe approaches that “halt” and “fill” damage, whereas second generation self-healing materials strive to “fully restore” the pre-failed material structure. In spite of limited commercial use to date, primarily because the technical details have not been suitably optimized, it is likely from a practical standpoint that first generation approaches will be the first to be employed commercially, whereas second generation approaches may take longer to implement. For self-healing biomaterials the optimization of technical considerations is further compounded by the additional constraints of toxicity and biocompatibility, necessitating inclusion of separate discussions of design criteria for self-healing biomaterials. PMID:21171168

  13. Self-Healing Laminate System

    NASA Technical Reports Server (NTRS)

    Beiermann, Brett A. (Inventor); Keller, Michael W. (Inventor); White, Scott R. (Inventor); Sottos, Nancy R. (Inventor)

    2016-01-01

    A laminate material may include a first flexible layer, and a self-healing composite layer in contact with the first flexible layer. The composite layer includes an elastomer matrix, a plurality of first capsules including a polymerizer, and a corresponding activator for the polymerizer. The laminate material may self-heal when subjected to a puncture or a tear.

  14. Assessment of Composite Delamination Self-Healing Under Cyclic Loading

    NASA Technical Reports Server (NTRS)

    O'Brien, T. Kevin

    2009-01-01

    Recently, the promise of self-healing materials for enhanced autonomous durability has been introduced using a micro-encapsulation technique where a polymer based healing agent is encapsulated in thin walled spheres and embedded into a base polymer along with a catalyst phase. For this study, composite skin-stiffener flange debonding specimens were manufactured from composite prepreg containing interleaf layers with a polymer based healing agent encapsulated in thin-walled spheres. Constant amplitude fatigue tests in three-point bending showed the effect of self-healing on the fatigue response of the skin-stiffener flange coupons. After the cycling that created debonding, fatigue tests were held at the mean load for 24 hours. For roughly half the specimens tested, when the cyclic loading was resumed a decrease in compliance (increase in stiffness) was observed, indicating that some healing had occurred. However, with continued cycling, the specimen compliance eventually increased to the original level before the hold, indicating that the damage had returned to its original state. As was noted in a prevoius study conducted with specimens tested under monotonically increasing loads to failure, healing achieved via the micro-encapsulation technique may be limited to the volume of healing agent available relative to the crack volume.

  15. Segmented molecular design of self-healing proteinaceous materials

    PubMed Central

    Sariola, Veikko; Pena-Francesch, Abdon; Jung, Huihun; Çetinkaya, Murat; Pacheco, Carlos; Sitti, Metin; Demirel, Melik C.

    2015-01-01

    Hierarchical assembly of self-healing adhesive proteins creates strong and robust structural and interfacial materials, but understanding of the molecular design and structure–property relationships of structural proteins remains unclear. Elucidating this relationship would allow rational design of next generation genetically engineered self-healing structural proteins. Here we report a general self-healing and -assembly strategy based on a multiphase recombinant protein based material. Segmented structure of the protein shows soft glycine- and tyrosine-rich segments with self-healing capability and hard beta-sheet segments. The soft segments are strongly plasticized by water, lowering the self-healing temperature close to body temperature. The hard segments self-assemble into nanoconfined domains to reinforce the material. The healing strength scales sublinearly with contact time, which associates with diffusion and wetting of autohesion. The finding suggests that recombinant structural proteins from heterologous expression have potential as strong and repairable engineering materials. PMID:26323335

  16. Segmented molecular design of self-healing proteinaceous materials

    NASA Astrophysics Data System (ADS)

    Sariola, Veikko; Pena-Francesch, Abdon; Jung, Huihun; Çetinkaya, Murat; Pacheco, Carlos; Sitti, Metin; Demirel, Melik C.

    2015-09-01

    Hierarchical assembly of self-healing adhesive proteins creates strong and robust structural and interfacial materials, but understanding of the molecular design and structure-property relationships of structural proteins remains unclear. Elucidating this relationship would allow rational design of next generation genetically engineered self-healing structural proteins. Here we report a general self-healing and -assembly strategy based on a multiphase recombinant protein based material. Segmented structure of the protein shows soft glycine- and tyrosine-rich segments with self-healing capability and hard beta-sheet segments. The soft segments are strongly plasticized by water, lowering the self-healing temperature close to body temperature. The hard segments self-assemble into nanoconfined domains to reinforce the material. The healing strength scales sublinearly with contact time, which associates with diffusion and wetting of autohesion. The finding suggests that recombinant structural proteins from heterologous expression have potential as strong and repairable engineering materials.

  17. Segmented molecular design of self-healing proteinaceous materials.

    PubMed

    Sariola, Veikko; Pena-Francesch, Abdon; Jung, Huihun; Çetinkaya, Murat; Pacheco, Carlos; Sitti, Metin; Demirel, Melik C

    2015-09-01

    Hierarchical assembly of self-healing adhesive proteins creates strong and robust structural and interfacial materials, but understanding of the molecular design and structure-property relationships of structural proteins remains unclear. Elucidating this relationship would allow rational design of next generation genetically engineered self-healing structural proteins. Here we report a general self-healing and -assembly strategy based on a multiphase recombinant protein based material. Segmented structure of the protein shows soft glycine- and tyrosine-rich segments with self-healing capability and hard beta-sheet segments. The soft segments are strongly plasticized by water, lowering the self-healing temperature close to body temperature. The hard segments self-assemble into nanoconfined domains to reinforce the material. The healing strength scales sublinearly with contact time, which associates with diffusion and wetting of autohesion. The finding suggests that recombinant structural proteins from heterologous expression have potential as strong and repairable engineering materials.

  18. Workshop on Concepts for Self-Healing Critical Infrastructures

    SciTech Connect

    GOLDSMITH, STEVEN Y.

    2003-06-01

    This report describes a workshop on self-healing infrastructures conducted jointly by Sandia National Laboratories, Infrastructure & Information Division, and the Massachusetts Institute of Technology, Engineering Systems Division. The workshop was held in summer, 2002 and funded under Laboratory-Directed Research and Development (LDRD) No.5 1540. The purpose of the workshop was to obtain a working definition of a self-healing infrastructure, explore concepts for self-healing infrastructures systems, and to propose engineering studies that would lay the foundation for the realization of such systems. The workshop produced a number of useful working documents that clarified the concept of self-healing applied to large-scale system-of-systems exemplified by the US National Critical Infrastructure. The workshop eventually resulted in a joint proposal to the National Science Foundation and a continuing collaboration on intelligent agent based approaches to coordination of infrastructure systems in a self-healing regime.

  19. Congenital Self-Healing Reticulohistiocytosis

    PubMed Central

    Lee, Young H.; Talekar, Mala K.; Chung, Catherine G.; Bell, Moshe D.

    2014-01-01

    Congenital self-healing reticulohistiocytosis, also known as congenital self-healing Langerhans cell histiocytosis or Hashimoto-Pritzker disease, is a Langerhans cell histiocytosis. It is characterized by skin lesions in the newborn period in an otherwise healthy infant that show a Langerhans cell infiltrate in the skin on histological analysis. These findings subsequently spontaneously involute. This report describes two newborns who presented at birth with differing presentations of congenital self-healing reticulohistiocytosis. A review of the disorder, including diagnosis and evaluation, is presented. PMID:24578781

  20. High-Strength, Tough, Fatigue Resistant, and Self-Healing Hydrogel Based on Dual Physically Cross-Linked Network.

    PubMed

    Gong, Zhengyu; Zhang, Guoping; Zeng, Xiaoliang; Li, Jinhui; Li, Gang; Huang, Wangping; Sun, Rong; Wong, Chingping

    2016-09-14

    Hydrogels usually suffer from low mechanical strength, which largely limit their application in many fields. In this Research Article, we prepared a dual physically cross-linked hydrogel composed of poly(acrylamide-co-acrylic acid) (PAM-co-PAA) and poly(vinyl alcohol) (PVA) by simple two-steps methods of copolymerization and freezing/thawing. The hydrogen bond-associated entanglement of copolymer chains formed as cross-linking points to construct the first network. After being subjected to the freezing/thawing treatment, PVA crystalline domains were formed to serve as knots of the second network. The hydrogels were demonstrated to integrate strength and toughness (1230 ± 90 kPa and 1250 ± 50 kJ/m(3)) by the introduction of second physically cross-linked network. What̀s more, the hydrogels exhibited rapid recovery, excellent fatigue resistance, and self-healing property. The dynamic property of the dual physically cross-linked network contributes to the excellent energy dissipation and self-healing property. Therefore, this work provides a new route to understand the toughness mechanism of dual physically cross-linked hydrogels, hopefully promoting current hydrogel research and expanding their applications. PMID:27548327

  1. Self-Healing, Inflatable, Rigidizable Shelter

    NASA Technical Reports Server (NTRS)

    Haight, Andrea; Gosau, Jan-Michael; Dixit, Anshu; Gleeson, Dan

    2012-01-01

    An inflatable, rigidizable shelter system was developed based on Rigi dization on Command (ROC) technology incorporating not only the requ ired low-stowage volume and lightweight character achieved from an i nflatable/rigidizable system, but also a self-healing foam system inc orporated between the rigidizable layers of the final structure to m inimize the damage caused by any punctures to the structure.

  2. Self healing of defected graphene

    SciTech Connect

    Chen, Jianhui; Shi, Tuwan; Cai, Tuocheng; Wu, Xiaosong; Yu, Dapeng; Xu, Tao; Sun, Litao

    2013-03-11

    For electronics applications, defects in graphene are usually undesirable because of their ability to scatter charge carriers, thereby reduce the carrier mobility. It would be extremely useful if the damage can be repaired. In this work, we employ Raman spectroscopy, X-ray photoemission spectroscopy, transmission electron microscopy, and electrical measurements to study defects in graphene introduced by argon plasma bombardment. We have found that majority of these defects can be cured by a simple thermal annealing process. The self-healing is attributed to recombination of mobile carbon adatoms with vacancies. With increasing level of plasma induced damage, the self-healing becomes less effective.

  3. Stretchable Self-Healing Polymeric Dielectrics Cross-Linked Through Metal-Ligand Coordination.

    PubMed

    Rao, Ying-Li; Chortos, Alex; Pfattner, Raphael; Lissel, Franziska; Chiu, Yu-Cheng; Feig, Vivian; Xu, Jie; Kurosawa, Tadanori; Gu, Xiaodan; Wang, Chao; He, Mingqian; Chung, Jong Won; Bao, Zhenan

    2016-05-11

    A self-healing dielectric elastomer is achieved by the incorporation of metal-ligand coordination as cross-linking sites in nonpolar polydimethylsiloxane (PDMS) polymers. The ligand is 2,2'-bipyridine-5,5'-dicarboxylic amide, while the metal salts investigated here are Fe(2+) and Zn(2+) with various counteranions. The kinetically labile coordination between Zn(2+) and bipyridine endows the polymer fast self-healing ability at ambient condition. When integrated into organic field-effect transistors (OFETs) as gate dielectrics, transistors with FeCl2 and ZnCl2 salts cross-linked PDMS exhibited increased dielectric constants compared to PDMS and demonstrated hysteresis-free transfer characteristics, owing to the low ion conductivity in PDMS and the strong columbic interaction between metal cations and the small Cl(-) anions which can prevent mobile anions drifting under gate bias. Fully stretchable transistors with FeCl2-PDMS dielectrics were fabricated and exhibited ideal transfer characteristics. The gate leakage current remained low even after 1000 cycles at 100% strain. The mechanical robustness and stable electrical performance proved its suitability for applications in stretchable electronics. On the other hand, transistors with gate dielectrics containing large-sized anions (BF4(-), ClO4(-), CF3SO3(-)) displayed prominent hysteresis due to mobile anions drifting under gate bias voltage. This work provides insights on future design of self-healing stretchable dielectric materials based on metal-ligand cross-linked polymers.

  4. Stretchable Self-Healing Polymeric Dielectrics Cross-Linked Through Metal-Ligand Coordination.

    PubMed

    Rao, Ying-Li; Chortos, Alex; Pfattner, Raphael; Lissel, Franziska; Chiu, Yu-Cheng; Feig, Vivian; Xu, Jie; Kurosawa, Tadanori; Gu, Xiaodan; Wang, Chao; He, Mingqian; Chung, Jong Won; Bao, Zhenan

    2016-05-11

    A self-healing dielectric elastomer is achieved by the incorporation of metal-ligand coordination as cross-linking sites in nonpolar polydimethylsiloxane (PDMS) polymers. The ligand is 2,2'-bipyridine-5,5'-dicarboxylic amide, while the metal salts investigated here are Fe(2+) and Zn(2+) with various counteranions. The kinetically labile coordination between Zn(2+) and bipyridine endows the polymer fast self-healing ability at ambient condition. When integrated into organic field-effect transistors (OFETs) as gate dielectrics, transistors with FeCl2 and ZnCl2 salts cross-linked PDMS exhibited increased dielectric constants compared to PDMS and demonstrated hysteresis-free transfer characteristics, owing to the low ion conductivity in PDMS and the strong columbic interaction between metal cations and the small Cl(-) anions which can prevent mobile anions drifting under gate bias. Fully stretchable transistors with FeCl2-PDMS dielectrics were fabricated and exhibited ideal transfer characteristics. The gate leakage current remained low even after 1000 cycles at 100% strain. The mechanical robustness and stable electrical performance proved its suitability for applications in stretchable electronics. On the other hand, transistors with gate dielectrics containing large-sized anions (BF4(-), ClO4(-), CF3SO3(-)) displayed prominent hysteresis due to mobile anions drifting under gate bias voltage. This work provides insights on future design of self-healing stretchable dielectric materials based on metal-ligand cross-linked polymers. PMID:27099162

  5. Rapid self-healing hydrogels

    PubMed Central

    Phadke, Ameya; Zhang, Chao; Arman, Bedri; Hsu, Cheng-Chih; Mashelkar, Raghunath A.; Lele, Ashish K.; Tauber, Michael J.; Arya, Gaurav; Varghese, Shyni

    2012-01-01

    Synthetic materials that are capable of autonomous healing upon damage are being developed at a rapid pace because of their many potential applications. Despite these advancements, achieving self-healing in permanently cross-linked hydrogels has remained elusive because of the presence of water and irreversible cross-links. Here, we demonstrate that permanently cross-linked hydrogels can be engineered to exhibit self-healing in an aqueous environment. We achieve this feature by arming the hydrogel network with flexible-pendant side chains carrying an optimal balance of hydrophilic and hydrophobic moieties that allows the side chains to mediate hydrogen bonds across the hydrogel interfaces with minimal steric hindrance and hydrophobic collapse. The self-healing reported here is rapid, occurring within seconds of the insertion of a crack into the hydrogel or juxtaposition of two separate hydrogel pieces. The healing is reversible and can be switched on and off via changes in pH, allowing external control over the healing process. Moreover, the hydrogels can sustain multiple cycles of healing and separation without compromising their mechanical properties and healing kinetics. Beyond revealing how secondary interactions could be harnessed to introduce new functions to chemically cross-linked polymeric systems, we also demonstrate various potential applications of such easy-to-synthesize, smart, self-healing hydrogels. PMID:22392977

  6. Self Healing Coating/Film Project

    NASA Technical Reports Server (NTRS)

    Summerfield, Burton; Thompson, Karen; Zeitlin, Nancy; Mullenix, Pamela; Calle, Luz; Williams, Martha

    2015-01-01

    Kennedy Space Center (KSC) has been developing self healing materials and technologies. This project seeks to further develop self healing functionality in thin films for applications such as corrosion protective coatings, inflatable structures, space suit materials, and electrical wire insulation.

  7. Self-healing fuse development

    NASA Technical Reports Server (NTRS)

    Jones, N. D.; Kinsinger, R. E.; Harris, L. P.

    1973-01-01

    The mercury-filled self-healing fuses developed for this program afford very good protection from circuit faults with rapid reclosure. Fuse performance and design parameters have been characterized. Life tests indicate a capability of 500 fuse operations. Fuse ratings are 150 v at 5, 15, 25 and 50 circuit A. A series of sample fuses using alumina and beryllia insulation have been furnished to NASA for circuit evaluation.

  8. Development of a self-healing soft pneumatic actuator: a first concept.

    PubMed

    Terryn, Seppe; Mathijssen, Glenn; Brancart, Joost; Lefeber, Dirk; Assche, Guy Van; Vanderborght, Bram

    2015-07-07

    Inspired by the intrinsic softness and the corresponding embodied intelligence principles, soft pneumatic actuators (SPA) have been developed, which ensure safe interaction in unstructured, unknown environments. Due to their intrinsic softness, these actuators have the ability to resist large mechanical impacts. However, the soft materials used in these structures are in general susceptible to damage caused by sharp objects found in the unstructured environments. This paper proposes to integrate a self-healing (SH-) mechanism in SPAs, such that cuts, tears and perforations in the actuator can be self-healed. Diels-Alder (DA-) polymers, covalent polymer network systems based on the thermoreversible DA-reaction, were selected and their mechanical, as well as SH-properties, are described. To evaluate the feasibility of developing an SPA constructed out of SH-material, a single cell prototype, a SH-soft pneumatic cell (SH-SPC), was constructed entirely out of DA-polymers. Exploiting the SH-property of the DA-polymers, a completely new shaping process is presented in this paper, referred to as 'shaping through folding and self-healing'. 3D polygon structures, like the cubic SH-SPC, can be constructed by folding SH-polymer sheet. The sides of the structures can be sealed and made airtight using a SH-procedure at relatively low temperatures (<90 °C). Both the (thermo) mechanical and SH-properties of the SH-SPC prototype were experimentally validated and showed excellent performances. Macroscopic incisions in the prototype were completely healed using a SH-procedure (<70 °C). Starting from this single-cell prototype, it is straight-forward to develop a multi-cell prototype, the first SPA ever built completely out of SH-polymers.

  9. Self-healing fuse development.

    NASA Technical Reports Server (NTRS)

    Jones, N. D.

    1972-01-01

    The self-healing fuse is a very fast acting current overload protective device which opens and recloses in a few milliseconds. The fuse confines a mercury column in an insulated channel and returns the mercury to the channel after firing. Ratings 5 to 50 A at 600 peak volts are possible with a life of hundreds of cycles. Compared to conventional fuses, much less fault current energy fires the fuse by heating the mercury to boiling temperature. Next an arc discharge develops while explosive forces expel the liquid mercury from the channel. Then the high impedance arc either extinguishes immediately, or operates for a few milliseconds, until a switch opens the circuit.

  10. Self-healing Characteristics of Collagen Coatings with Respect to Surface Abrasion

    PubMed Central

    Kim, Chang-Lae; Kim, Dae-Eun

    2016-01-01

    A coating based on collagen with self-healing properties was developed for applications in mechanical components that are prone to abrasion due to contact with a counter surface. The inherent swelling behavior of collagen in water was exploited as the fundamental mechanism behind self-healing of a wear scar formed on the surface. The effects of freeze-drying process and water treatment of the collagen coatings on their mechanical and self-healing properties were analyzed. Water was also used as the medium to trigger the self-healing effect of the collagen coatings after the wear test. It was found that collagen coatings without freeze-drying did not demonstrate any self-healing effect whereas the coatings treated by freeze-drying process showed remarkable self-healing effect. Overall, collagen coatings that were freeze-dried and water treated showed the best friction and self-healing properties. Repeated self-healing ability of these coatings with respect to wear scar was also demonstrated. It was also confirmed that the self-healing property of the collagen coating was effective over a relatively wide range of temperature. PMID:27010967

  11. Self-healing Characteristics of Collagen Coatings with Respect to Surface Abrasion

    NASA Astrophysics Data System (ADS)

    Kim, Chang-Lae; Kim, Dae-Eun

    2016-03-01

    A coating based on collagen with self-healing properties was developed for applications in mechanical components that are prone to abrasion due to contact with a counter surface. The inherent swelling behavior of collagen in water was exploited as the fundamental mechanism behind self-healing of a wear scar formed on the surface. The effects of freeze-drying process and water treatment of the collagen coatings on their mechanical and self-healing properties were analyzed. Water was also used as the medium to trigger the self-healing effect of the collagen coatings after the wear test. It was found that collagen coatings without freeze-drying did not demonstrate any self-healing effect whereas the coatings treated by freeze-drying process showed remarkable self-healing effect. Overall, collagen coatings that were freeze-dried and water treated showed the best friction and self-healing properties. Repeated self-healing ability of these coatings with respect to wear scar was also demonstrated. It was also confirmed that the self-healing property of the collagen coating was effective over a relatively wide range of temperature.

  12. Self-healing Characteristics of Collagen Coatings with Respect to Surface Abrasion.

    PubMed

    Kim, Chang-Lae; Kim, Dae-Eun

    2016-01-01

    A coating based on collagen with self-healing properties was developed for applications in mechanical components that are prone to abrasion due to contact with a counter surface. The inherent swelling behavior of collagen in water was exploited as the fundamental mechanism behind self-healing of a wear scar formed on the surface. The effects of freeze-drying process and water treatment of the collagen coatings on their mechanical and self-healing properties were analyzed. Water was also used as the medium to trigger the self-healing effect of the collagen coatings after the wear test. It was found that collagen coatings without freeze-drying did not demonstrate any self-healing effect whereas the coatings treated by freeze-drying process showed remarkable self-healing effect. Overall, collagen coatings that were freeze-dried and water treated showed the best friction and self-healing properties. Repeated self-healing ability of these coatings with respect to wear scar was also demonstrated. It was also confirmed that the self-healing property of the collagen coating was effective over a relatively wide range of temperature. PMID:27010967

  13. Generalizing the self-healing diffusion Monte Carlo approach to finite temperature: A path for the optimization of low-energy many-body bases

    SciTech Connect

    Reboredo, Fernando A.; Kim, Jeongnim

    2014-02-21

    A statistical method is derived for the calculation of thermodynamic properties of many-body systems at low temperatures. This method is based on the self-healing diffusion Monte Carlo method for complex functions [F. A. Reboredo, J. Chem. Phys. 136, 204101 (2012)] and some ideas of the correlation function Monte Carlo approach [D. M. Ceperley and B. Bernu, J. Chem. Phys. 89, 6316 (1988)]. In order to allow the evolution in imaginary time to describe the density matrix, we remove the fixed-node restriction using complex antisymmetric guiding wave functions. In the process we obtain a parallel algorithm that optimizes a small subspace of the many-body Hilbert space to provide maximum overlap with the subspace spanned by the lowest-energy eigenstates of a many-body Hamiltonian. We show in a model system that the partition function is progressively maximized within this subspace. We show that the subspace spanned by the small basis systematically converges towards the subspace spanned by the lowest energy eigenstates. Possible applications of this method for calculating the thermodynamic properties of many-body systems near the ground state are discussed. The resulting basis can also be used to accelerate the calculation of the ground or excited states with quantum Monte Carlo.

  14. Improved One-Way Hash Chain and Revocation Polynomial-Based Self-Healing Group Key Distribution Schemes in Resource-Constrained Wireless Networks

    PubMed Central

    Chen, Huifang; Xie, Lei

    2014-01-01

    Self-healing group key distribution (SGKD) aims to deal with the key distribution problem over an unreliable wireless network. In this paper, we investigate the SGKD issue in resource-constrained wireless networks. We propose two improved SGKD schemes using the one-way hash chain (OHC) and the revocation polynomial (RP), the OHC&RP-SGKD schemes. In the proposed OHC&RP-SGKD schemes, by introducing the unique session identifier and binding the joining time with the capability of recovering previous session keys, the problem of the collusion attack between revoked users and new joined users in existing hash chain-based SGKD schemes is resolved. Moreover, novel methods for utilizing the one-way hash chain and constructing the personal secret, the revocation polynomial and the key updating broadcast packet are presented. Hence, the proposed OHC&RP-SGKD schemes eliminate the limitation of the maximum allowed number of revoked users on the maximum allowed number of sessions, increase the maximum allowed number of revoked/colluding users, and reduce the redundancy in the key updating broadcast packet. Performance analysis and simulation results show that the proposed OHC&RP-SGKD schemes are practical for resource-constrained wireless networks in bad environments, where a strong collusion attack resistance is required and many users could be revoked. PMID:25529204

  15. Self-healing hyperbranched poly(aroyltriazole)s

    PubMed Central

    Wei, Qiang; Wang, Jian; Shen, Xiaoyuan; Zhang, Xiao A.; Sun, Jing Zhi; Qin, Anjun; Tang, Ben Zhong

    2013-01-01

    The research on self-healing polymers has been a hot topic. The encapsulated-monomer/catalyst, supramolecular self-assembly, and reversible or dynamic covalent bond formation are the prevailingly adopted strategies. The alternative of irreversible covalent bond formation is, however, to be further developed. In this contribution, self-healing hyperbranched poly(aroyltriazole)s of PI and PII sharing such mechanism were developed. The polymers were synthesized by our developed metal-free click polymerizations of bis(aroylacetylene)s and triazide. They are processible and have excellent film-forming ability. High quality homogeneous films and sticks free from defects could be obtained by casting. The scratched films could be self-repaired upon general heating. The cut films and sticks could be healed by stacking or pressing the halves together at elevated temperature. Thus, these hyperbranched polymers could find broad applications in diverse areas, and our design concept for self-healing materials should be generally applicable to other hyperbranched polymers with reactive groups on their peripheries.

  16. Biomimetic, Self-Healing Nanocomposites for Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Morse, Daniel E.

    2003-01-01

    This final report contains a summary of significant findings, and bibliographies of publications and patents resulting from the research. The findings are grouped as follows: A) Lustrin-Mimetic Self-Healing Polymer Networks; B) Nanostructure-Directing Catalysis of Synthesis of Electronically and Optoelectronically Active Metallo-oxanes and Organometallics; C) New Discovery that Molecular Stencils Control Directional Growth to Form Light-Weight Mineral Foams.

  17. Self-healing cable for extreme environments

    NASA Technical Reports Server (NTRS)

    Huston, Dryver R. (Inventor); Tolmie, Bernard R. (Inventor)

    2009-01-01

    Self-healing cable apparatus and methods disclosed. The self-healing cable has a central core surrounded by an adaptive cover that can extend over the entire length of the self-healing cable or just one or more portions of the self-healing cable. The adaptive cover includes an axially and/or radially compressible-expandable (C/E) foam layer that maintains its properties over a wide range of environmental conditions. A tape layer surrounds the C/E layer and is applied so that it surrounds and axially and/or radially compresses the C/E layer. When the self-healing cable is subjected to a damaging force that causes a breach in the outer jacket and the tape layer, the corresponding localized axially and/or radially compressed portion of the C/E foam layer expands into the breach to form a corresponding localized self-healed region. The self-healing cable is manufacturable with present-day commercial self-healing cable manufacturing tools.

  18. Microencapsulation of Self Healing Agents for Corrosion Control Coatings

    NASA Technical Reports Server (NTRS)

    Jolley, S. T.; Li, W.; Buhrow, J. W.; Calle, L. M.

    2011-01-01

    Corrosion, the environmentally induced degradation of materials, is a very costly problem that has a major impact on the global economy. Results from a 2-year breakthrough study released in 2002 by the U.S. Federal Highway Administration (FHWA) showed that the total annual estimated direct cost associated with metallic corrosion in nearly every U.S. industry sector was a staggering $276 billion, approximately 3.1% of the nation's Gross Domestic Product (GOP). Corrosion protective coatings are widely used to protect metallic structures from the detrimental effects of corrosion but their effectiveness can be seriously compromised by mechanical damage, such as a scratch, that exposes the metallic substrate. The incorporation of a self healing mechanism into a corrosion control coating would have the potential to significantly increase its effectiveness and useful lifetime. This paper describes work performed to incorporate a number of microcapsule-based self healing systems into corrosion control coatings. The work includes the preparation and evaluation of self-healing systems based on curable epoxy, acrylate, and siloxane resins, as well as, microencapsulated systems based on passive, solvent born, healing agent delivery. The synthesis and optimization of microcapsule-based self healing systems for thin coating (less than 100 micron) will be presented.

  19. Effect of blast furnace slag on self-healing of microcracks in cementitious materials

    SciTech Connect

    Huang, Haoliang; Ye, Guang; Damidot, Denis

    2014-06-01

    The physico-chemical process of self-healing in blast furnace slag cement paste was investigated in this paper. With a high slag content i.e., 66% in cement paste and saturated Ca(OH)₂ solution as activator, it was found that the reaction products formed in cracks are composed of C-S-H, ettringite, hydrogarnet and OH–hydrotalcite. The fraction of C-S-H in the reaction products is much larger than the other minerals. Large amount of ettringite formed in cracks indicates the leaching of SO₄⁻² ions from the bulk paste and consequently the recrystallization. Self-healing proceeds fast within 50 h and then slows down. According to thermodynamic modeling, when the newly formed reaction products are carbonated, the filling fraction of crack increases first and then decreases. Low soluble minerals such as silica gel, gibbsite and calcite are formed. Compared to Portland cement paste, the potential of self-healing in slag cement paste is higher when the percentage of slag is high. Highlights: • Self-healing reaction products in slag cement paste were characterized. • Self-healing reaction products formed in time were quantified with image analysis. • Self-healing in slag cement paste was simulated with a reactive transport model. • Effect of carbonation on self-healing was investigated by thermodynamic modeling. • Effect of slag on self-healing was discussed based on experiments and simulation.

  20. The use of azide-alkyne click chemistry in recent syntheses and applications of polytriazole-based nanostructured polymers

    NASA Astrophysics Data System (ADS)

    Shi, Yi; Cao, Xiaosong; Gao, Haifeng

    2016-02-01

    The rapid development of efficient organic click coupling reactions has significantly facilitated the construction of synthetic polymers with sophisticated branched nanostructures. This Feature Article summarizes the recent progress in the application of efficient copper-catalyzed and copper-free azide-alkyne cycloaddition (CuAAC and CuFAAC) reactions in the syntheses of dendrimers, hyperbranched polymers, star polymers, graft polymers, molecular brushes, and cyclic graft polymers. Literature reports on the interesting properties and functions of these polytriazole-based nanostructured polymers are also discussed to illustrate their potential applications as self-healing polymers, adhesives, polymer catalysts, opto-electronic polymer materials and polymer carriers for drug and imaging molecules.

  1. Highly flexible transparent self-healing composite based on electrospun core-shell nanofibers produced by coaxial electrospinning for anti-corrosion and electrical insulation.

    PubMed

    An, Seongpil; Liou, Minho; Song, Kyo Yong; Jo, Hong Seok; Lee, Min Wook; Al-Deyab, Salem S; Yarin, Alexander L; Yoon, Sam S

    2015-11-14

    Coaxial electrospinning was used to fabricate two types of core-shell fibers: the first type with liquid resin monomer in the core and polyacrylonitrile in the shell, and the second type with liquid curing agent in the core and polyacrylonitrile in the shell. These two types of core-shell fibers were mutually entangled and embedded into two flexible transparent matrices thus forming transparent flexible self-healing composite materials. Such materials could be formed before only using emulsion electrospinning, rather than coaxial electrospinning. The self-healing properties of such materials are associated with release of healing agents (resin monomer and cure) from nanofiber cores in damaged locations with the subsequent polymerization reaction filing the micro-crack with polydimethylsiloxane. Transparency of these materials is measured and the anti-corrosive protection provided by them is demonstrated in electrochemical experiments.

  2. Highly flexible transparent self-healing composite based on electrospun core-shell nanofibers produced by coaxial electrospinning for anti-corrosion and electrical insulation

    NASA Astrophysics Data System (ADS)

    An, Seongpil; Liou, Minho; Song, Kyo Yong; Jo, Hong Seok; Lee, Min Wook; Al-Deyab, Salem S.; Yarin, Alexander L.; Yoon, Sam S.

    2015-10-01

    Coaxial electrospinning was used to fabricate two types of core-shell fibers: the first type with liquid resin monomer in the core and polyacrylonitrile in the shell, and the second type with liquid curing agent in the core and polyacrylonitrile in the shell. These two types of core-shell fibers were mutually entangled and embedded into two flexible transparent matrices thus forming transparent flexible self-healing composite materials. Such materials could be formed before only using emulsion electrospinning, rather than coaxial electrospinning. The self-healing properties of such materials are associated with release of healing agents (resin monomer and cure) from nanofiber cores in damaged locations with the subsequent polymerization reaction filing the micro-crack with polydimethylsiloxane. Transparency of these materials is measured and the anti-corrosive protection provided by them is demonstrated in electrochemical experiments.

  3. Highly flexible transparent self-healing composite based on electrospun core-shell nanofibers produced by coaxial electrospinning for anti-corrosion and electrical insulation.

    PubMed

    An, Seongpil; Liou, Minho; Song, Kyo Yong; Jo, Hong Seok; Lee, Min Wook; Al-Deyab, Salem S; Yarin, Alexander L; Yoon, Sam S

    2015-11-14

    Coaxial electrospinning was used to fabricate two types of core-shell fibers: the first type with liquid resin monomer in the core and polyacrylonitrile in the shell, and the second type with liquid curing agent in the core and polyacrylonitrile in the shell. These two types of core-shell fibers were mutually entangled and embedded into two flexible transparent matrices thus forming transparent flexible self-healing composite materials. Such materials could be formed before only using emulsion electrospinning, rather than coaxial electrospinning. The self-healing properties of such materials are associated with release of healing agents (resin monomer and cure) from nanofiber cores in damaged locations with the subsequent polymerization reaction filing the micro-crack with polydimethylsiloxane. Transparency of these materials is measured and the anti-corrosive protection provided by them is demonstrated in electrochemical experiments. PMID:26456716

  4. Hydrogen-Bonding-Supported Self-Healing Antifogging Thin Films

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaojie; He, Junhui

    2015-03-01

    Inspired by the repair of DNA through efficient reformation of hydrogen bonds (H-bonds), herein we report a facile one-step approach to construction of self-healing antifogging thin films on the basis of partly cross-linked poly(vinyl alcohol)(PVA) and poly(acrylic acid)(PAA). By designing the molar ratio of hydroxyl groups to carboxyl groups, the cross-linked polymer thin films maintain abundant free hydroxyl groups to present excellent antifogging property, which is derived from the hydrophilicity and hygroscopicity of the thin films. The thin films showed smart intrinsic self-healing characteristics towards wounds caused by external forces, which is attributed to sufficient free hydroxyl groups at the scratched interfaces to reform H-bonds across the interfaces and a sufficient chain mobility that is indispensable for chain diffusion across the interfaces and hydroxyl groups association to form H-bonds. No synthetic surfaces reported so far possess all the unique characteristics of the polymer thin films: intrinsic self-healing, long-term antifogging, excellent mechanical property, high transmittance and large-scale feasibility.

  5. Hydrogen-Bonding-Supported Self-Healing Antifogging Thin Films

    PubMed Central

    Zhang, Xiaojie; He, Junhui

    2015-01-01

    Inspired by the repair of DNA through efficient reformation of hydrogen bonds (H-bonds), herein we report a facile one-step approach to construction of self-healing antifogging thin films on the basis of partly cross-linked poly(vinyl alcohol)(PVA) and poly(acrylic acid)(PAA). By designing the molar ratio of hydroxyl groups to carboxyl groups, the cross-linked polymer thin films maintain abundant free hydroxyl groups to present excellent antifogging property, which is derived from the hydrophilicity and hygroscopicity of the thin films. The thin films showed smart intrinsic self-healing characteristics towards wounds caused by external forces, which is attributed to sufficient free hydroxyl groups at the scratched interfaces to reform H-bonds across the interfaces and a sufficient chain mobility that is indispensable for chain diffusion across the interfaces and hydroxyl groups association to form H-bonds. No synthetic surfaces reported so far possess all the unique characteristics of the polymer thin films: intrinsic self-healing, long-term antifogging, excellent mechanical property, high transmittance and large-scale feasibility. PMID:25784188

  6. Magnetic Field Triggered Multicycle Damage Sensing and Self Healing

    NASA Astrophysics Data System (ADS)

    Ahmed, Anansa S.; Ramanujan, R. V.

    2015-09-01

    Multifunctional materials inspired by biological structures have attracted great interest, e.g. for wearable/ flexible “skin” and smart coatings. A current challenge in this area is to develop an artificial material which mimics biological skin by simultaneously displaying color change on damage as well as self healing of the damaged region. Here we report, for the first time, the development of a damage sensing and self healing magnet-polymer composite (Magpol), which actively responds to an external magnetic field. We incorporated reversible sensing using mechanochromic molecules in a shape memory thermoplastic matrix. Exposure to an alternating magnetic field (AMF) triggers shape recovery and facilitates damage repair. Magpol exhibited a linear strain response upto 150% strain and complete recovery after healing. We have demonstrated the use of this concept in a reusable biomedical device i.e., coated guidewires. Our findings offer a new synergistic method to bestow multifunctionality for applications ranging from medical device coatings to adaptive wing structures.

  7. Magnetic Field Triggered Multicycle Damage Sensing and Self Healing.

    PubMed

    Ahmed, Anansa S; Ramanujan, R V

    2015-01-01

    Multifunctional materials inspired by biological structures have attracted great interest, e.g. for wearable/ flexible "skin" and smart coatings. A current challenge in this area is to develop an artificial material which mimics biological skin by simultaneously displaying color change on damage as well as self healing of the damaged region. Here we report, for the first time, the development of a damage sensing and self healing magnet-polymer composite (Magpol), which actively responds to an external magnetic field. We incorporated reversible sensing using mechanochromic molecules in a shape memory thermoplastic matrix. Exposure to an alternating magnetic field (AMF) triggers shape recovery and facilitates damage repair. Magpol exhibited a linear strain response upto 150% strain and complete recovery after healing. We have demonstrated the use of this concept in a reusable biomedical device i.e., coated guidewires. Our findings offer a new synergistic method to bestow multifunctionality for applications ranging from medical device coatings to adaptive wing structures.

  8. Damage properties simulations of self-healing composites.

    PubMed

    Chen, Cheng; Ji, Hongwei; Wang, Huaiwen

    2013-10-01

    Self-healing materials are inspired by biological systems in which damage triggers an autonomic healing response. The damage properties of a self-healing polymer composite were investigated by numerical simulation in this paper. Unit cell models with single-edge centered crack and single-edge off-centered crack were employed to investigate the damage initiation and crack evolution by the extended finite element method (XFEM) modeling. The effect of microcapsule's Young's modulus on composites was investigated. Result indicates the microcapsule's Young's modulus has little effect on the unit cell's carrying capacity. It was found that during the crack propagation process, its direction is attracted toward the microcapsules, which makes it helpful for the microcapsules to be ruptured by the propagating crack fronts resulting in release of the healing agent into the cracks by capillary action. PMID:24245129

  9. Novel self-healing materials chemistries for targeted applications

    NASA Astrophysics Data System (ADS)

    Wilson, Gerald O.

    Self-healing materials of the type developed by White and co-workers [1] were designed to autonomically heal themselves when damaged, thereby extending the lifetime of various applications in which such material systems are employed. The system was based on urea-formaldehyde microcapsules containing dicyclopentadiene (DCPD) and Grubbs' catalyst particles embedded together in an epoxy matrix. When a crack propagates through the material, it ruptures the microcapsules, releasing DCPD into the crack plane, where it comes in contact and reacts with the catalyst to initiate a ring opening metathesis polymerization (ROMP), bonding the crack and restoring structural continuity. The present work builds on this concept in several ways. Firstly, it expands the scope and versatility of the ROMP self-healing chemistry by incorporation into epoxy vinyl ester matrices. Major technical challenges in this application include protection of the catalyst from deactivation by aggressive curing agents, and optimization of the concentration of healing agents in the matrix. Secondly, new ruthenium catalysts are evaluated for application in ROMP-based self-healing materials. The use of alternative derivatives of Grubbs' catalyst gave rise to self-healing systems with improved healing efficiencies and thermal properties. Evaluation of the stability of these new catalysts to primary amine curing agents used in the curing of common epoxy matrices also led to the discovery and characterization of new ruthenium catalysts which exhibited ROMP initiation kinetics superior to those of first and second generation Grubbs' catalysts. Finally, free radical polymerization was evaluated for application in the development of bio-compatible self-healing materials. [1] White, S. R.; Sottos, N. R.; Geubelle, P. R.; Moore, J. S.; Kessler, M. R.; Sriram, S. R.; Brown, E. N.; Viswanathan, S. Nature 2001, 409, 794.

  10. Self-healing cable apparatus and methods

    NASA Technical Reports Server (NTRS)

    Huston, Dryver (Inventor); Esser, Brian (Inventor)

    2007-01-01

    Self-healing cable apparatus and methods are disclosed. The cable has a central core surrounded by an adaptive cover that can extend over the entire length of the cable or just one or more portions of the cable. The adaptive cover includes a protective layer having an initial damage resistance, and a reactive layer. When the cable is subjected to a localized damaging force, the reactive layer responds by creating a corresponding localized self-healed region. The self-healed region provides the cable with enhanced damage resistance as compared to the cable's initial damage resistance. Embodiments of the invention utilize conventional epoxies or foaming materials in the reactive layer that are released to form the self-healed region when the damaging force reaches the reactive layer.

  11. Self-Healing Nanocomposites for Reusable Composite Cryotanks

    NASA Technical Reports Server (NTRS)

    Eberly, Daniel; Ou, Runqing; Karcz, Adam; Skandan, Ganesh

    2013-01-01

    Composite cryotanks, or composite overwrapped pressure vessels (COPVs), offer advantages over currently used aluminum-lithium cryotanks, particularly with respect to weight savings. Future NASA missions are expected to use COPVs in spaceflight propellant tanks to store fuels, oxidizers, and other liquids for launch and space exploration vehicles. However, reliability, reparability, and reusability of the COPVs are still being addressed, especially in cryogenic temperature applications; this has limited the adoption of COPVs in reusable vehicle designs. The major problem with composites is the inherent brittleness of the epoxy matrix, which is prone to microcrack formation, either from exposure to cryogenic conditions or from impact from different sources. If not prevented, the microcracks increase gas permeation and leakage. Accordingly, materials innovations are needed to mitigate microcrack damage, and prevent damage in the first place, in composite cryotanks. The self-healing technology being developed is capable of healing the microcracks through the use of a novel engineered nanocomposite, where a uniquely designed nanoparticle additive is incorporated into the epoxy matrix. In particular, this results in an enhancement in the burst pressure after cryogenic cycling of the nanocomposite COPVs, relative to the control COPVs. Incorporating a novel, self-healing, epoxy-based resin into the manufacture of COPVs allows repeatable self-healing of microcracks to be performed through the simple application of a low-temperature heat source. This permits COPVs to be reparable and reusable with a high degree of reliability, as microcracks will be remediated. The unique phase-separated morphology that was imparted during COPV manufacture allows for multiple self-healing cycles. Unlike single-target approaches where one material property is often improved at the expense of another, robustness has been introduced to a COPV by a combination of a modified resin and

  12. A highly stretchable autonomous self-healing elastomer

    NASA Astrophysics Data System (ADS)

    Li, Cheng-Hui; Wang, Chao; Keplinger, Christoph; Zuo, Jing-Lin; Jin, Lihua; Sun, Yang; Zheng, Peng; Cao, Yi; Lissel, Franziska; Linder, Christian; You, Xiao-Zeng; Bao, Zhenan

    2016-06-01

    It is a challenge to synthesize materials that possess the properties of biological muscles—strong, elastic and capable of self-healing. Herein we report a network of poly(dimethylsiloxane) polymer chains crosslinked by coordination complexes that combines high stretchability, high dielectric strength, autonomous self-healing and mechanical actuation. The healing process can take place at a temperature as low as -20 °C and is not significantly affected by surface ageing and moisture. The crosslinking complexes used consist of 2,6-pyridinedicarboxamide ligands that coordinate to Fe(III) centres through three different interactions: a strong pyridyl-iron one, and two weaker carboxamido-iron ones through both the nitrogen and oxygen atoms of the carboxamide groups. As a result, the iron-ligand bonds can readily break and re-form while the iron centres still remain attached to the ligands through the stronger interaction with the pyridyl ring, which enables reversible unfolding and refolding of the chains. We hypothesize that this behaviour supports the high stretchability and self-healing capability of the material.

  13. A highly stretchable autonomous self-healing elastomer

    NASA Astrophysics Data System (ADS)

    Li, Cheng-Hui; Wang, Chao; Keplinger, Christoph; Zuo, Jing-Lin; Jin, Lihua; Sun, Yang; Zheng, Peng; Cao, Yi; Lissel, Franziska; Linder, Christian; You, Xiao-Zeng; Bao, Zhenan

    2016-06-01

    It is a challenge to synthesize materials that possess the properties of biological muscles—strong, elastic and capable of self-healing. Herein we report a network of poly(dimethylsiloxane) polymer chains crosslinked by coordination complexes that combines high stretchability, high dielectric strength, autonomous self-healing and mechanical actuation. The healing process can take place at a temperature as low as ‑20 °C and is not significantly affected by surface ageing and moisture. The crosslinking complexes used consist of 2,6-pyridinedicarboxamide ligands that coordinate to Fe(III) centres through three different interactions: a strong pyridyl–iron one, and two weaker carboxamido–iron ones through both the nitrogen and oxygen atoms of the carboxamide groups. As a result, the iron–ligand bonds can readily break and re-form while the iron centres still remain attached to the ligands through the stronger interaction with the pyridyl ring, which enables reversible unfolding and refolding of the chains. We hypothesize that this behaviour supports the high stretchability and self-healing capability of the material.

  14. A highly stretchable autonomous self-healing elastomer.

    PubMed

    Li, Cheng-Hui; Wang, Chao; Keplinger, Christoph; Zuo, Jing-Lin; Jin, Lihua; Sun, Yang; Zheng, Peng; Cao, Yi; Lissel, Franziska; Linder, Christian; You, Xiao-Zeng; Bao, Zhenan

    2016-06-01

    It is a challenge to synthesize materials that possess the properties of biological muscles-strong, elastic and capable of self-healing. Herein we report a network of poly(dimethylsiloxane) polymer chains crosslinked by coordination complexes that combines high stretchability, high dielectric strength, autonomous self-healing and mechanical actuation. The healing process can take place at a temperature as low as -20 °C and is not significantly affected by surface ageing and moisture. The crosslinking complexes used consist of 2,6-pyridinedicarboxamide ligands that coordinate to Fe(III) centres through three different interactions: a strong pyridyl-iron one, and two weaker carboxamido-iron ones through both the nitrogen and oxygen atoms of the carboxamide groups. As a result, the iron-ligand bonds can readily break and re-form while the iron centres still remain attached to the ligands through the stronger interaction with the pyridyl ring, which enables reversible unfolding and refolding of the chains. We hypothesize that this behaviour supports the high stretchability and self-healing capability of the material. PMID:27219708

  15. Self-healing of polymeric materials: The effect of the amount of DCPD confined within microcapsules

    NASA Astrophysics Data System (ADS)

    Chipara, Dorina M.; Perez, Alma; Lozano, Karen; Elamin, Ibrahim; Villarreal, Jahaziel; Salinas, Alfonso; Chipara, Mircea

    2013-03-01

    The self-healing SH) of polymers is based on the dispersion of a catalyst and of microcapsules filled with monomer within the polymeric matrix. Sufficiently large external stresses will rupture the microcapsule, releasing the monomer which will diffuse through the polymer and eventually will reach a catalyst particle igniting a polymerization reaction. The classical SH system includes first generation Grubbs catalyst and poly-urea formaldehyde microcapsules filled with DCPD. The polymerization reaction is a ring-opening metathesis. The size and the mechanical features of microcapsules are critical in controlling the SH process. Research was focused on the effect of DCPD on the size and thickness of microcapsules. Microscopy was used to determine the size of microcapsules (typically in the range of 10-4 m) and the thickness of the microcapsules (ranging between 10-6 to 10-8 m). Research revealed a thick disordered layer over a thin and more compact wall. Raman spectroscopy confirmed the confinement of DCPD, TGA measurements aimed to a better understanding of the degradation processes in inert atmosphere, and mechanical tests supported the ignition of self-healing properties. This research has been supported by National Science Foundation under DMR (PREM) grant 0934157.

  16. Polysiloxane-Based Autonomic Self-Healing Elastomers Obtained through Dynamic Boronic Ester Bonds Prepared by Thiol-Ene "Click" Chemistry.

    PubMed

    Zuo, Yujing; Gou, Zhiming; Zhang, Changqiao; Feng, Shengyu

    2016-07-01

    Cross-linked silicone elastomers constructed with dynamic-covalent boronic esters are first synthesized by photoinitiated radical thiol-ene "click" chemistry. The resultant samples can be cut with a sharp knife into two pieces and then healed via the reversibility of the boronic ester cross-linkages to restore the original silicone sample within 30 min. Regulation of luminescent properties is achieved by incorporating organic dye into the elastomers through a "one-pot" thiol-ene reaction. The proposed synthesis procedure demonstrates a new strategy to produce boronic acid silicone materials capable of self-healing without external forces. PMID:27159536

  17. Self-Healing Nanocomposite Hydrogel with Well-Controlled Dynamic Mechanics

    NASA Astrophysics Data System (ADS)

    Li, Qiaochu; Mishra, Sumeet; Chen, Pangkuan; Tracy, Joseph; Holten-Andersen, Niels

    Network dynamics is a crucial factor that determines the macroscopic self-healing rate and efficiency in polymeric hydrogel materials, yet its controllability is seldom studied in most reported self-healing hydrogel systems. Inspired by mussel's adhesion chemistry, we developed a novel approach to assemble inorganic nanoparticles and catechol-decorated PEG polymer into a hydrogel network. When utilized as reversible polymer-particle crosslinks, catechol-metal coordination bonds yield a unique gel network with dynamic mechanics controlled directly by interfacial crosslink structure. Taking advantage of this structure-property relationship at polymer-particle interfaces, we next designed a hierarchically structured hybrid gel with two distinct relaxation timescales. By tuning the relative contribution of the two hierarchical relaxation modes, we are able to finely control the gel's dynamic mechanical behavior from a viscoelastic fluid to a stiff solid, yet preserving its fast self-healing property without the need for external stimuli.

  18. Self-healing Microencapsulation of Biomacromolecules without Organic Solvents**

    PubMed Central

    Reinhold, Samuel E.; Desai, Kashappa-Goud H.; Zhang, Li; Olsen, Karl F.

    2012-01-01

    Microencapsulation of biomacromolecules in PLGA is routinely performed with organic solvent through multiple complex steps deleterious to the biomacromolecule. The new self-healing based PLGA microencapsulation obviates micronization- and organic solvent-induced protein damage, provides very high encapsulation efficiency, exhibit stabilization and slow release of labile tetanus protein antigen, and provides long-term testosterone suppression in rats following a single injection of encapsulated leuprolide. PMID:23011773

  19. Self-Healing Networks: Redundancy and Structure

    PubMed Central

    Quattrociocchi, Walter; Caldarelli, Guido; Scala, Antonio

    2014-01-01

    We introduce the concept of self-healing in the field of complex networks modelling; in particular, self-healing capabilities are implemented through distributed communication protocols that exploit redundant links to recover the connectivity of the system. We then analyze the effect of the level of redundancy on the resilience to multiple failures; in particular, we measure the fraction of nodes still served for increasing levels of network damages. Finally, we study the effects of redundancy under different connectivity patterns—from planar grids, to small-world, up to scale-free networks—on healing performances. Small-world topologies show that introducing some long-range connections in planar grids greatly enhances the resilience to multiple failures with performances comparable to the case of the most resilient (and least realistic) scale-free structures. Obvious applications of self-healing are in the important field of infrastructural networks like gas, power, water, oil distribution systems. PMID:24533065

  20. Self healing nature of bilayer graphene

    NASA Astrophysics Data System (ADS)

    Debroy, Sanghamitra; Pavan Kumar Miriyala, V.; Vijaya Sekhar, K.; Acharyya, Swati Ghosh; Acharyya, Amit

    2016-08-01

    The phenomenon of self healing of cracks in bilayer graphene sheet has been studied using molecular dynamics simulations. The bilayer graphene sheet was subjected to uniaxial tensile load resulting in initiation and propagation of cracks on exceeding the ultimate tensile strength. Subsequently, all forces acting on the sheet were removed and sheet was relaxed. The cracks formed in the graphene sheet healed without any external aid within 0.4 ps The phenomenon of self healing of the cracks in graphene sheet was found to be independent of the length of the crack, but occurred for critical crack opening distance less than 5 Å for AA stacked sheet and 13 Å for AB stacked bilayer graphene sheet. Self healing was observed for both AB (mixed stacking of armchair and zigzag graphene sheet) and AA (both sheets of similar orientation i.e. either armchair-armchair or zigzag-zigzag) stacking of bilayer graphene sheet.

  1. SELF-HEALING PSEUDOCANCERS OF THE SKIN

    PubMed Central

    Nelson, Lawrence M.

    1959-01-01

    It is believed that a group of self-healing tumors which clinically and microscopically may be confused with squamous cell carcinomas are all variants of one entity, although there are certain differences between the members of the group. The clinical, as well as the histologic evaluation of these tumors is necessary to differentiate them from true squamous cell carcinomas. Some should be treated for cosmetic purposes since the scars following self-healing may be more unsightly than those caused by treatment. ImagesFigure 1.Figure 2.Figure 3.Figure 4.Figure 5.Figure 6.Figure 7.Figure 8. PMID:13618746

  2. Providing self-healing ability for wireless sensor node by using reconfigurable hardware.

    PubMed

    Yuan, Shenfang; Qiu, Lei; Gao, Shang; Tong, Yao; Yang, Weiwei

    2012-10-29

    Wireless sensor networks (WSNs) have received tremendous attention over the past ten years. In engineering applications of WSNs, a number of sensor nodes are usually spread across some specific geographical area. Some of these nodes have to work in harsh environments. Dependability of the Wireless Sensor Network (WSN) is very important for its successful applications in the engineering area. In ordinary research, when a node has a failure, it is usually discarded and the network is reorganized to ensure the normal operation of the WSN. Using appropriate WSN re-organization methods, though the sensor networks can be reorganized, this causes additional maintenance costs and sometimes still decreases the function of the networks. In those situations where the sensor networks cannot be reorganized, the performance of the whole WSN will surely be degraded. In order to ensure the reliable and low cost operation of WSNs, a method to develop a wireless sensor node with self-healing ability based on reconfigurable hardware is proposed in this paper. Two self-healing WSN node realization paradigms based on reconfigurable hardware are presented, including a redundancy-based self-healing paradigm and a whole FPAA/FPGA based self-healing paradigm. The nodes designed with the self-healing ability can dynamically change their node configurations to repair the nodes’ hardware failures. To demonstrate these two paradigms, a strain sensor node is adopted as an illustration to show the concepts. Two strain WSN sensor nodes with self-healing ability are developed respectively according to the proposed self-healing paradigms. Evaluation experiments on self-healing ability and power consumption are performed. Experimental results show that the developed nodes can self-diagnose the failures and recover to a normal state automatically. The research presented can improve the robustness of WSNs and reduce the maintenance cost of WSNs in engineering applications.

  3. Providing Self-Healing Ability for Wireless Sensor Node by Using Reconfigurable Hardware

    PubMed Central

    Yuan, Shenfang; Qiu, Lei; Gao, Shang; Tong, Yao; Yang, Weiwei

    2012-01-01

    Wireless sensor networks (WSNs) have received tremendous attention over the past ten years. In engineering applications of WSNs, a number of sensor nodes are usually spread across some specific geographical area. Some of these nodes have to work in harsh environments. Dependability of the Wireless Sensor Network (WSN) is very important for its successful applications in the engineering area. In ordinary research, when a node has a failure, it is usually discarded and the network is reorganized to ensure the normal operation of the WSN. Using appropriate WSN re-organization methods, though the sensor networks can be reorganized, this causes additional maintenance costs and sometimes still decreases the function of the networks. In those situations where the sensor networks cannot be reorganized, the performance of the whole WSN will surely be degraded. In order to ensure the reliable and low cost operation of WSNs, a method to develop a wireless sensor node with self-healing ability based on reconfigurable hardware is proposed in this paper. Two self-healing WSN node realization paradigms based on reconfigurable hardware are presented, including a redundancy-based self-healing paradigm and a whole FPAA/FPGA based self-healing paradigm. The nodes designed with the self-healing ability can dynamically change their node configurations to repair the nodes' hardware failures. To demonstrate these two paradigms, a strain sensor node is adopted as an illustration to show the concepts. Two strain WSN sensor nodes with self-healing ability are developed respectively according to the proposed self-healing paradigms. Evaluation experiments on self-healing ability and power consumption are performed. Experimental results show that the developed nodes can self-diagnose the failures and recover to a normal state automatically. The research presented can improve the robustness of WSNs and reduce the maintenance cost of WSNs in engineering applications. PMID:23202176

  4. Cytocompatible, Photoreversible, and Self-Healing Hydrogels for Regulating Bone Marrow Stromal Cell Differentiation.

    PubMed

    Yu, Lianlian; Xu, Kaige; Ge, Liangpeng; Wan, Wenbing; Darabi, Ali; Xing, Malcolm; Zhong, Wen

    2016-09-01

    Photo-crosslinking and self-healing have received considerable attention for the design of intelligent materials. A novel photostimulated, self-healing, and cytocompatible hydrogel system is reported. A coumarin methacrylate crosslinker is synthesized to modify the polyacrylamide-based hydrogels. With the [2+2] cyclo-addition of coumarin moieties, the hydrogels exhibit excellent self-healing capacity when they are exposed to light with wavelengths at 280 and 365 nm, respectively. To enhance cell compatibility, a poly (amidoamine) crosslinker is also synthesized. Variations in light exposure times and irradiation wavelengths are found to alter the self-healing property of the hydrogels. The hydrogels are shown to induce a regular cellular pattern. The hydrogels are used to regulate bone marrow stromal cells differentiation. The relative mRNA expressions are recorded to monitor the osteogenic differentiation of the cells.

  5. Methyl methacrylate as a healing agent for self-healing cementitious materials

    NASA Astrophysics Data System (ADS)

    Van Tittelboom, K.; Adesanya, K.; Dubruel, P.; Van Puyvelde, P.; De Belie, N.

    2011-12-01

    Different types of healing agents have already been tested on their efficiency for use in self-healing cementitious materials. Generally, commercial healing agents are used while their properties are adjusted for manual crack repair and not for autonomous crack healing. Consequently, the amount of regain in properties due to self-healing of cracks is limited. In this research, a methyl methacrylate (MMA)-based healing agent was developed specifically for use in self-healing cementitious materials. Various parameters were optimized including the viscosity, curing time, strength, etc. After the desired properties were obtained, the healing agent was encapsulated and screened for its self-healing efficiency. The decrease in water permeability due to autonomous crack healing using MMA as a healing agent was similar to the results obtained for manually healed cracks. First results seem promising: however, further research needs to be undertaken in order to obtain an optimal healing agent ready for use in practice.

  6. Cytocompatible, Photoreversible, and Self-Healing Hydrogels for Regulating Bone Marrow Stromal Cell Differentiation.

    PubMed

    Yu, Lianlian; Xu, Kaige; Ge, Liangpeng; Wan, Wenbing; Darabi, Ali; Xing, Malcolm; Zhong, Wen

    2016-09-01

    Photo-crosslinking and self-healing have received considerable attention for the design of intelligent materials. A novel photostimulated, self-healing, and cytocompatible hydrogel system is reported. A coumarin methacrylate crosslinker is synthesized to modify the polyacrylamide-based hydrogels. With the [2+2] cyclo-addition of coumarin moieties, the hydrogels exhibit excellent self-healing capacity when they are exposed to light with wavelengths at 280 and 365 nm, respectively. To enhance cell compatibility, a poly (amidoamine) crosslinker is also synthesized. Variations in light exposure times and irradiation wavelengths are found to alter the self-healing property of the hydrogels. The hydrogels are shown to induce a regular cellular pattern. The hydrogels are used to regulate bone marrow stromal cells differentiation. The relative mRNA expressions are recorded to monitor the osteogenic differentiation of the cells. PMID:27280860

  7. A Multiple-Action Self-Healing Coating

    NASA Astrophysics Data System (ADS)

    Lutz, Alexander; van den Berg, Otto; Wielant, Jan; De Graeve, Iris; Terryn, Herman

    2015-12-01

    This paper describes a self-healing coating for corrosion protection of metals which combines two different types of self-healing mechanisms in one coating with multiple-healing functionality. 2-Mercaptobenzothiazole (MBT) was loaded into layered double hydroxide (LDH) carriers which were mixed into an acrylated polycaprolactone polyurethane based shape recovery coating and applied on Hot Dip Galvanized steel (HDG). The effect of triggered release of MBT on the protection of HDG became visible when samples with manually applied defects in the coating were immersed in 0.05 M NaCl solution (first, autonomous healing mechanism). The shape recovery (second, non-autonomous healing mechanism) was triggered by heating the samples for 2 minutes to 60°C. SEM-EDX and Raman Spectroscopy proved the presence of MBT in the LDH, in the MBT-loaded LDH in the coating and the released MBT on the HDG surface in the damaged area after being in contact with a solution containing corrosive ions. Electrochemical impedance spectroscopy (EIS) and scanning vibrating electrode technique (SVET) demonstrate the corrosion protection effect of MBT in the coating with a defect and the restoration of the barrier properties of the coating after defect closure. This way, the independent mechanisms of this multi-action self-healing coating could be demonstrated.

  8. Development of self-healing coatings for corrosion protection on metallic structures

    NASA Astrophysics Data System (ADS)

    Stankiewicz, Alicja; Barker, Michael B.

    2016-08-01

    Inspired by biological systems, artificial self-healing materials are designed for repairing local damage caused by external factors. The rapidly expanding field of self-healing systems contains, among others, materials with well-defined surface properties. Undoubtedly, enhancing surface functionalisation, by applying smart coatings, enjoys an extensive interest. The self-healing ability is particularly essential property for corrosion protection strategies, especially when the use of one of the most effective corrosion systems, based on chromium(VI) compounds, is now banned by the current registration, evaluation, authorisation and restriction of chemicals legislation. Self-healing protective coatings are produced using macromolecular compounds, ceramics, metals and composites. Considering the wide range of available materials, the number of potential combinations seems to be unlimited. The self-healing action of such coatings is activated by appropriate stimuli: temperature changes, radiation, pH changes, pressure changes and mechanical action. In this paper, the research and practical implications of the various approaches to achieving self-healing functionality of protective coatings, as well as potential developments in this area, are explored.

  9. Self-healing in segmented metallized film capacitors: Experimental and theoretical investigations for engineering design

    NASA Astrophysics Data System (ADS)

    Belko, V. O.; Emelyanov, O. A.

    2016-01-01

    A significant increase in the efficiency of modern metallized film capacitors has been achieved by the application of special segmented nanometer-thick electrodes. The proper design of the electrode segmentation guarantees the best efficiency of the capacitor's self-healing (SH) ability. Meanwhile, the reported theoretical and experimental results have not led to the commonly accepted model of the SH process, since the experimental SH dissipated energy value is several times higher than the calculated one. In this paper, we show that the difference is caused by the heat outflow into polymer film. Based on this, a mathematical model of the metallized electrode destruction is developed. These insights in turn are leading to a better understanding of the SH development. The adequacy of the model is confirmed by both the experiments and the numerical calculations. A procedure of optimal segmented electrode design is offered.

  10. Robust synthesis of epoxy resin-filled microcapsules for application to self-healing materials.

    PubMed

    Bolimowski, Patryk A; Bond, Ian P; Wass, Duncan F

    2016-02-28

    Mechanically and thermally robust microcapsules containing diglycidyl ether bisphenol A-based epoxy resin and a high-boiling-point organic solvent were synthesized in high yield using in situ polymerization of urea and formaldehyde in an oil-in-water emulsion. Microcapsules were characterized in terms of their size and size distribution, shell surface morphology and thermal resistance to the curing cycles of commercially used epoxy polymers. The size distribution of the capsules and characteristics such as shell thickness can be controlled by the specific parameters of microencapsulation, including concentrations of reagents, stirrer speed and sonication. Selected microcapsules, and separated core and shell materials, were analysed using thermogravimetric analysis and differential scanning calorimetry. It is demonstrated that capsules lose minimal 2.5 wt% at temperatures no higher than 120°C. These microcapsules can be applied to self-healing carbon fibre composite structural materials, with preliminary results showing promising performance. PMID:26755765

  11. Magnetic Field Triggered Multicycle Damage Sensing and Self Healing

    PubMed Central

    Ahmed, Anansa S.; Ramanujan, R. V.

    2015-01-01

    Multifunctional materials inspired by biological structures have attracted great interest, e.g. for wearable/ flexible “skin” and smart coatings. A current challenge in this area is to develop an artificial material which mimics biological skin by simultaneously displaying color change on damage as well as self healing of the damaged region. Here we report, for the first time, the development of a damage sensing and self healing magnet-polymer composite (Magpol), which actively responds to an external magnetic field. We incorporated reversible sensing using mechanochromic molecules in a shape memory thermoplastic matrix. Exposure to an alternating magnetic field (AMF) triggers shape recovery and facilitates damage repair. Magpol exhibited a linear strain response upto 150% strain and complete recovery after healing. We have demonstrated the use of this concept in a reusable biomedical device i.e., coated guidewires. Our findings offer a new synergistic method to bestow multifunctionality for applications ranging from medical device coatings to adaptive wing structures. PMID:26348284

  12. Bioconcrete: next generation of self-healing concrete.

    PubMed

    Seifan, Mostafa; Samani, Ali Khajeh; Berenjian, Aydin

    2016-03-01

    Concrete is one of the most widely used construction materials and has a high tendency to form cracks. These cracks lead to significant reduction in concrete service life and high replacement costs. Although it is not possible to prevent crack formation, various types of techniques are in place to heal the cracks. It has been shown that some of the current concrete treatment methods such as the application of chemicals and polymers are a source of health and environmental risks, and more importantly, they are effective only in the short term. Thus, treatment methods that are environmentally friendly and long-lasting are in high demand. A microbial self-healing approach is distinguished by its potential for long-lasting, rapid and active crack repair, while also being environmentally friendly. Furthermore, the microbial self-healing approach prevails the other treatment techniques due to the efficient bonding capacity and compatibility with concrete compositions. This study provides an overview of the microbial approaches to produce calcium carbonate (CaCO3). Prospective challenges in microbial crack treatment are discussed, and recommendations are also given for areas of future research. PMID:26825821

  13. Bioconcrete: next generation of self-healing concrete.

    PubMed

    Seifan, Mostafa; Samani, Ali Khajeh; Berenjian, Aydin

    2016-03-01

    Concrete is one of the most widely used construction materials and has a high tendency to form cracks. These cracks lead to significant reduction in concrete service life and high replacement costs. Although it is not possible to prevent crack formation, various types of techniques are in place to heal the cracks. It has been shown that some of the current concrete treatment methods such as the application of chemicals and polymers are a source of health and environmental risks, and more importantly, they are effective only in the short term. Thus, treatment methods that are environmentally friendly and long-lasting are in high demand. A microbial self-healing approach is distinguished by its potential for long-lasting, rapid and active crack repair, while also being environmentally friendly. Furthermore, the microbial self-healing approach prevails the other treatment techniques due to the efficient bonding capacity and compatibility with concrete compositions. This study provides an overview of the microbial approaches to produce calcium carbonate (CaCO3). Prospective challenges in microbial crack treatment are discussed, and recommendations are also given for areas of future research.

  14. Self-healing coatings containing microcapsule

    NASA Astrophysics Data System (ADS)

    Zhao, Yang; Zhang, Wei; Liao, Le-ping; Wang, Si-jie; Li, Wu-jun

    2012-01-01

    Effectiveness of epoxy resin filled microcapsules was investigated for healing of cracks generated in coatings. Microcapsules were prepared by in situ polymerization of urea-formaldehyde resin to form shell over epoxy resin droplets. Characteristics of these capsules were studied by 3D measuring laser microscope, particle size analyzer, Fourier-transform infrared spectroscopy (FTIR) and differential scanning calorimeter (DSC) to investigate their surface morphology, size distribution, chemical structure and thermal stability, respectively. The results indicate that microcapsules containing epoxy resins can be synthesized successfully. The size is around 100 μm. The rough outer surface of microcapsule is composed of agglomerated urea-formaldehyde nanoparticles. The size and surface morphology of microcapsule can be controlled by selecting different processing parameters. The microcapsules basically exhibit good storage stability at room temperature, and they are chemically stable before the heating temperature is up to approximately 200 °C. The model system of self-healing coating consists of epoxy resin matrix, 10 wt% microencapsulated healing agent, 2 wt% catalyst solution. The self-healing function of this coating system is evaluated through self-healing testing of damaged and healed coated steel samples.

  15. Scratch Cell Test: A Simple, Cost Effective Screening Tool to Evaluate Self-Healing in Anti-Corrosion Coatings

    NASA Astrophysics Data System (ADS)

    Rani, Amitha; Somaiah, Durga; Megha; Poddar, Mitalee

    2014-09-01

    A quick and simple scratch cell set up to evaluate the self-healing of an hybrid sol-gel (ormosil) coating was fabricated. This methacrylate-based anti-corrosion coating was applied on the aerospace aluminium alloy AA2024-T3, and cured at room temperature. This technique of evaluation requires minimum instrumentation. The inhibitors cerium nitrate, benzotriazole and 8-hydroxy quinoline (8-HQ) were used in the study. The self-healing ability of the inhibitors decreased in the following order: 8-HQ, BTZ and Ce. 8-HQ showed the highest self-healing ability and was comparable to the commercial hexavalent chromium conversion coating—Alodine. Spectroscopic analysis of the electrolyte and EDX of the coatings indicated the movement of the inhibitor from the coating to the site of damage, thereby effecting self-healing. It was observed that an increased inhibitor concentration in the coatings did not accelerate the healing process. Inhibitor release was slower in the coatings doped with inhibitor-loaded nano-containers, when compared to inhibitor-spiked coatings. This property of controlled release is desirable in self-healing coatings. Electro impedance studies further confirmed self-healing efficiency of the coatings. The scratch cell study reported here is the first of its kind with the ormosil under study on AA2024-T3 aluminium alloy. The results are encouraging and warranty a quick and simple qualitative screening of the self-healing potential of the inhibitors with minimum instrumentation.

  16. A self-healing poly(dimethyl siloxane) elastomer

    NASA Astrophysics Data System (ADS)

    Keller, Michael Wade

    2007-12-01

    microcapsule-based self-healing PDMS is capable of recovering a significant portion of the original torsional stiffness and retards dynamic crack growth rate. Depending on the matrix material, a nearly complete recovery of the original torsional stiffness is possible.

  17. Layer-by-Layer Assembly of a Self-Healing Anticorrosion Coating on Magnesium Alloys.

    PubMed

    Fan, Fan; Zhou, Chunyu; Wang, Xu; Szpunar, Jerzy

    2015-12-16

    Fabrication of self-healing anticorrosion coatings has attracted attention as it has the ability to extend the service life and prevent the substrate from corrosive attack. However, a coating system with a rapid self-healing ability and an improved corrosion resistance is rarely reported. In this work, we developed a self-healing anticorrosion coating on a magnesium alloy (AZ31). The coating comprises a cerium-based conversion layer, a graphene oxide layer, and a branched poly(ethylene imine) (PEI)/poly(acrylic acid) (PAA) multilayer. We incorporated the graphene oxide as corrosion inhibitors and used the PEI/PAA multilayers to provide the self-healing ability to the coating systems. X-ray diffraction (XRD) and Raman spectroscopy were used to characterize the composition of the multilayers, and scanning electron microscopy (SEM) was used to analyze the surface morphology. The electrochemical impedance spectroscopy (EIS) results illustrate the improved corrosion resistance of the coating. The proposed coating also has a rapid self-healing ability in the presence of water. PMID:26583562

  18. Effects of self-healing microcapsules on bending performance in composite brake pads

    NASA Astrophysics Data System (ADS)

    Zhang, Li; Dong, Xiu-ping; Wang, Hui

    2009-07-01

    For the purpose of reducing self-weight, friction noise and cost, improving shock absorption, enhancing corrosion and wear resistance, brake pads made of composite materials with self-healing function are prepared to substitute metal ones by designing ingredients and applying optimized production technology. As self-healing capsules are chosen, new method with technology of self-healing microcapsules, dicyclpentadiene (DCPD) microcapsules coated with poly (urea-formaldehyde), is put forward in this paper. In the crack's extending process, the stress is concentrated at the crack end, where the microcapsule is designed to be located. When the stress goes through the microcapsules and causes them to break, the self-healing liquid runs out to fill the crack by the capillary and it will poly-react with catalyst in the composite. As a result, the crack is healed. In this paper, polymer matrix composite brake pads with 6 prescriptions are prepared and studied. Three-point bending tests are carried out according to standards in GB/T 3356-1999 and the elastic constants of these polymer matrix composites are obtained by experiments. In accordance with the law of the continuous fiber composite, elastic constants of the short-fiber composite can be calculated by proportions of each ingredient. Results show that the theoretical expected results and the experimental values are consistent. 0.3-1.2 % mass proportion of microcapsules has little effects on the composite's bending intensity and modulus of elasticity. These studies also show that self-healing microcapsules used in composite brake pads is feasible.

  19. Characterization and performance of a self-healing composite material

    NASA Astrophysics Data System (ADS)

    Kessler, Michael Richard

    The development of a self-healing polymer-matrix composite material that possesses the ability to heal cracks autonomically is described. The system uses a monomer repair agent, dicyclopentadiene (DCPD), which is stored in an epoxy matrix by dispersing microcapsules containing the liquid repair agent throughout the matrix. When the material is damaged, cracks propagate through the material and break open the microcapsules, releasing the repair agent into the crack plane. Finally, the DCPD repair agent solidifies by ring-opening metathesis polymerization (ROMP) after coming in contact with a ruthenium-based catalyst (Grubbs' catalyst) dispersed in the matrix. The process by which the DCPD-filled microcapsules are prepared and the various techniques to characterize the microcapsules are discussed. The cure kinetics of poly dicyclopentadiene (pDCPD) prepared by ROMP with three different concentrations of Grubbs' catalyst are examined using differential scanning calorimetry (DSC). The experimental data are used to test several different phenomenological kinetic models. The data are best modeled with a "model-free" isoconversional method. This analysis reveals that the activation energy increases significantly for degree of cure greater than 60%. Catalyst concentration is shown to have a large effect on the cure kinetics. Differential scanning calorimetry measurements on the catalyzed healing agent are also used to study the stability of the system to environmental conditions. A study of the healing of delamination damage in woven reinforced epoxy composites is performed. Three types of healing process are studied. In the first, a catalyzed monomer is manually injected into the delamination. In the second, a self-activated material is created by embedding the catalyst directly into the matrix of the composite, then manually injecting the monomer. In the third, a fully integrated in situ system is described with embedded microcapsules and catalyst. Double

  20. Supramolecular polymer networks: hydrogels and bulk materials.

    PubMed

    Voorhaar, Lenny; Hoogenboom, Richard

    2016-07-21

    Supramolecular polymer networks are materials crosslinked by reversible supramolecular interactions, such as hydrogen bonding or electrostatic interactions. Supramolecular materials show very interesting and useful properties resulting from their dynamic nature, such as self-healing, stimuli-responsiveness and adaptability. Here we will discuss recent progress in polymer-based supramolecular networks for the formation of hydrogels and bulk materials. PMID:27206244

  1. Processing and damage recovery of intrinsic self-healing glass fiber reinforced composites

    NASA Astrophysics Data System (ADS)

    Sordo, Federica; Michaud, Véronique

    2016-08-01

    Glass fiber reinforced composites with a self-healing, supramolecular hybrid network matrix were produced using a modified vacuum assisted resin infusion moulding process adapted to high temperature processing. The quality and fiber volume fraction (50%) of the obtained materials were assessed through microscopy and matrix burn-off methods. The thermo-mechanical properties were quantified by means of dynamic mechanical analysis, revealing very high damping properties compared to traditional epoxy-based glass fiber reinforced composites. Self-healing properties were assessed by three-point bending tests. A high recovery of the flexural properties, around 72% for the elastic modulus and 65% of the maximum flexural stress, was achieved after a resting period of 24 h at room temperature. Recovery after low velocity impact events was also visually observed. Applications for this intrinsic and autonomic self-healing highly reinforced composite material point towards semi-structural applications where high damping and/or integrity recovery after impact are required.

  2. Autonomous self-healing structural composites with bio-inspired design

    NASA Astrophysics Data System (ADS)

    D'Elia, Eleonora; Eslava, Salvador; Miranda, Miriam; Georgiou, Theoni K.; Saiz, Eduardo

    2016-05-01

    Strong and tough natural composites such as bone, silk or nacre are often built from stiff blocks bound together using thin interfacial soft layers that can also provide sacrificial bonds for self-repair. Here we show that it is possible exploit this design in order to create self-healing structural composites by using thin supramolecular polymer interfaces between ceramic blocks. We have built model brick-and-mortar structures with ceramic contents above 95 vol% that exhibit strengths of the order of MPa (three orders of magnitude higher than the interfacial polymer) and fracture energies that are two orders of magnitude higher than those of the glass bricks. More importantly, these properties can be fully recovered after fracture without using external stimuli or delivering healing agents. This approach demonstrates a very promising route towards the design of strong, ideal self-healing materials able to self-repair repeatedly without degradation or external stimuli.

  3. Autonomous self-healing structural composites with bio-inspired design

    PubMed Central

    D’Elia, Eleonora; Eslava, Salvador; Miranda, Miriam; Georgiou, Theoni K.; Saiz, Eduardo

    2016-01-01

    Strong and tough natural composites such as bone, silk or nacre are often built from stiff blocks bound together using thin interfacial soft layers that can also provide sacrificial bonds for self-repair. Here we show that it is possible exploit this design in order to create self-healing structural composites by using thin supramolecular polymer interfaces between ceramic blocks. We have built model brick-and-mortar structures with ceramic contents above 95 vol% that exhibit strengths of the order of MPa (three orders of magnitude higher than the interfacial polymer) and fracture energies that are two orders of magnitude higher than those of the glass bricks. More importantly, these properties can be fully recovered after fracture without using external stimuli or delivering healing agents. This approach demonstrates a very promising route towards the design of strong, ideal self-healing materials able to self-repair repeatedly without degradation or external stimuli. PMID:27146382

  4. Autonomous self-healing structural composites with bio-inspired design.

    PubMed

    D'Elia, Eleonora; Eslava, Salvador; Miranda, Miriam; Georgiou, Theoni K; Saiz, Eduardo

    2016-01-01

    Strong and tough natural composites such as bone, silk or nacre are often built from stiff blocks bound together using thin interfacial soft layers that can also provide sacrificial bonds for self-repair. Here we show that it is possible exploit this design in order to create self-healing structural composites by using thin supramolecular polymer interfaces between ceramic blocks. We have built model brick-and-mortar structures with ceramic contents above 95 vol% that exhibit strengths of the order of MPa (three orders of magnitude higher than the interfacial polymer) and fracture energies that are two orders of magnitude higher than those of the glass bricks. More importantly, these properties can be fully recovered after fracture without using external stimuli or delivering healing agents. This approach demonstrates a very promising route towards the design of strong, ideal self-healing materials able to self-repair repeatedly without degradation or external stimuli. PMID:27146382

  5. Recent Development of Durable and Self-Healing Surfaces with Special Wettability.

    PubMed

    Chen, Kunlin; Wu, Yi; Zhou, Shuxue; Wu, Limin

    2016-03-01

    Artificial special wetting surfaces have drawn much interest due to their important applications in many fields. Nevertheless, tremendous challenges still remain for the fabrication of wetting surfaces with durable and self-healing properties. Here, recent progress of durable, self-healing wetting surfaces is highlighted by discussing the fabrications of several typical wetting surfaces including superhydrophobic surfaces, superamphiphobic surfaces, underwater superoleophobic surfaces, and high hydrophilic antifouling surfaces based on expertise and related research experience. To conclude, some perspectives on the future research and development of these special wetting surfaces are presented.

  6. Recent Development of Durable and Self-Healing Surfaces with Special Wettability.

    PubMed

    Chen, Kunlin; Wu, Yi; Zhou, Shuxue; Wu, Limin

    2016-03-01

    Artificial special wetting surfaces have drawn much interest due to their important applications in many fields. Nevertheless, tremendous challenges still remain for the fabrication of wetting surfaces with durable and self-healing properties. Here, recent progress of durable, self-healing wetting surfaces is highlighted by discussing the fabrications of several typical wetting surfaces including superhydrophobic surfaces, superamphiphobic surfaces, underwater superoleophobic surfaces, and high hydrophilic antifouling surfaces based on expertise and related research experience. To conclude, some perspectives on the future research and development of these special wetting surfaces are presented. PMID:26833559

  7. Extremely Stretchable and Fast Self-Healing Hydrogels.

    PubMed

    Jeon, Insu; Cui, Jiaxi; Illeperuma, Widusha R K; Aizenberg, Joanna; Vlassak, Joost J

    2016-06-01

    Dynamic crosslinking of extremely stretchable hydrogels with rapid self-healing ability is described. Using this new strategy, the obtained hydrogels are able to elongate 100 times compared to their initial length and to completely self-heal within 30 s without external energy input. PMID:27061799

  8. Assisted self-healing in ripped graphene

    SciTech Connect

    Blaeckberg, L.; Sjoestrand, H.; Klintenberg, M.; Ringbom, A.

    2010-11-15

    A monolayer of sp{sup 2}-bonded carbon (graphene) is a material with great technological promise because of, for example, its transport, electrical, optical, and mechanical properties. In this work noble gas diffusion through ripped graphene sheets is explored. The motivation is improved detection systems used worldwide to verify compliance of the Comprehensive Nuclear-Test-Ban Treaty. It is demonstrated that even ripped graphene sheets and/or nonoverlapping graphene flakes inhibit noble gas diffusion. The latter has been shown for He and Xe where an infinitely long rip was constructed to have Stone-Wales edges. It is also shown that the ripped graphene layer self-heal in an alternating pentagon, hexagon, heptagon (5-6-7) and 7-6-5 pattern perpendicular to the rip. Moreover, the noble gas (He and Xe) assists in the healing process of wider rips.

  9. Assisted self-healing in ripped graphene

    NASA Astrophysics Data System (ADS)

    Bläckberg, L.; Ringbom, A.; Sjöstrand, H.; Klintenberg, M.

    2010-11-01

    A monolayer of sp2 -bonded carbon (graphene) is a material with great technological promise because of, for example, its transport, electrical, optical, and mechanical properties. In this work noble gas diffusion through ripped graphene sheets is explored. The motivation is improved detection systems used worldwide to verify compliance of the Comprehensive Nuclear-Test-Ban Treaty. It is demonstrated that even ripped graphene sheets and/or nonoverlapping graphene flakes inhibit noble gas diffusion. The latter has been shown for He and Xe where an infinitely long rip was constructed to have Stone-Wales edges. It is also shown that the ripped graphene layer self-heal in an alternating pentagon, hexagon, heptagon (5-6-7) and 7-6-5 pattern perpendicular to the rip. Moreover, the noble gas (He and Xe) assists in the healing process of wider rips.

  10. Reflexive composites: self-healing composite structures

    NASA Astrophysics Data System (ADS)

    Margraf, Thomas W., Jr.; Barnell, Thomas J.; Havens, Ernie; Hemmelgarn, Christopher D.

    2008-03-01

    Cornerstone Research Group Inc. has developed reflexive composites achieving increased vehicle survivability through integrated structural awareness and responsiveness to damage. Reflexive composites can sense damage through integrated piezoelectric sensing networks and respond to damage by heating discrete locations to activate the healable polymer matrix in areas of damage. The polymer matrix is a modified thermoset shape memory polymer that heals based on phenomena known as reptation. In theory, the reptation healing phenomena should occur in microseconds; however, during experimentation, it has been observed that to maximize healing and restore up to 85 % of mechanical properties a healing cycle of at least three minutes is required. This paper will focus on work conducted to determine the healing mechanisms at work in CRG's reflexive composites, the optimal healing cycles, and an explanation of the difference between the reptation model and actual healing times.

  11. Active self-healing encapsulation of vaccine antigens in PLGA microspheres

    PubMed Central

    Desai, Kashappa-Goud H.; Schwendeman, Steven P.

    2013-01-01

    Herein, we describe the detailed development of a simple and effective method to microencapsulate vaccine antigens in poly(lactic-co-glycolic acid) (PLGA) by simple mixing of preformed active self-microencapsulating (SM) PLGA microspheres in a low concentration aqueous antigen solution at modest temperature (10-38 °C). Co-encapsulating protein-sorbing vaccine adjuvants and polymer plasticizers were used to “actively” load the protein in the polymer pores and facilitate polymer self-healing at temperature > hydrated polymer glass transition temperature, respectively. The microsphere formulation parameters and loading conditions to provide optimal active self-healing microencapsulation of vaccine antigen in PLGA was investigated. Active self-healing encapsulation of two vaccine antigens, ovalbumin and tetanus toxoid (TT), in PLGA microspheres was adjusted by preparing blank microspheres containing different vaccine adjuvant (aluminum hydroxide (Al(OH)3) or calcium phosphate). Active loading of vaccine antigen in Al(OH)3-PLGA microspheres was found to: a) increase proportionally with an increasing loading of Al(OH)3 (0.88-3 wt%) and addition of porosigen, b) decrease when the inner Al(OH)3/trehalose phase to 1 mL outer oil phase and size of microspheres was respectively > 0.2 mL and 63 μm, and c) change negligibly by PLGA concentration and initial incubation (loading) temperature. Encapsulation of protein sorbing Al(OH)3 in PLGA microspheres resulted in suppression of self-healing of PLGA pores, which was then overcome by improving polymer chain mobility, which in turn was accomplished by coincorporating hydrophobic plasticizers in PLGA. Active self-healing microencapsulation of manufacturing process-labile TT in PLGA was found to: a) obviate micronization- and organic solvent-induced TT degradation, b) improve antigen loading (1.4-1.8 wt% TT) and encapsulation efficiency (~ 97%), c) provide nearly homogeneous distribution and stabilization of antigen in polymer

  12. A probabilistic method for determining the volume fraction of pre-embedded capsules in self-healing materials

    NASA Astrophysics Data System (ADS)

    Lv, Zhong; Chen, Huisu

    2014-10-01

    Autonomous healing of cracks using pre-embedded capsules containing healing agent is becoming a promising approach to restore the strength of damaged structures. In addition to the material properties, the size and volume fraction of capsules influence crack healing in the matrix. Understanding the crack and capsule interaction is critical in the development and design of structures made of self-healing materials. Assuming that the pre-embedded capsules are randomly dispersed we theoretically model flat ellipsoidal crack interaction with capsules and determine the probability of a crack intersecting the pre-embedded capsules i.e. the self-healing probability. We also develop a probabilistic model of a crack simultaneously meeting with capsules and catalyst carriers in two-component self-healing system matrix. Using a risk-based healing approach, we determine the volume fraction and size of the pre-embedded capsules that are required to achieve a certain self-healing probability. To understand the effect of the shape of the capsules on self-healing we theoretically modeled crack interaction with spherical and cylindrical capsules. We compared the results of our theoretical model with Monte-Carlo simulations of crack interaction with capsules. The formulae presented in this paper will provide guidelines for engineers working with self-healing structures in material selection and sustenance.

  13. An attempt to prepare nonchromate, self-healing protective films containing molybdate on iron

    SciTech Connect

    Aramaki, K.

    1999-11-01

    Preparation of a nonchromate, self-healing protective film on an Fe surface was attempted. A protective film of 1,2-bis(triethoxysilyl)ethane ([C{sub 2}H{sub 5}O]{sub 3} Si[CH{sub 2}]{sub 2} Si[OC{sub 2}H{sub 5}]{sub 3}) polymer containing a fine powder of ammonium heptamolybdate tetrahydrate ([NH{sub 4}]{sub 6}Mo{sub 7}O{sub 24} {center{underscore}dot} 4H{sub 2}O) was prepared on a surface of Fe electrode passivated in aerated 0.1-M sodium molybdate (Na{sub 2}MoO{sub 4}). The protective ability of this film was examined on the covered electrode in an aerated 0.1-M sodium chloride (NaCl) solution at 30 C by polarization measurement. The protection efficiency (P) of the film was significantly high, 99.0%. After the electrode coated with the film was scratched with a knife edge, the self-healing ability of the film was estimated on the electrode in the NaCl solution by polarization measurement. The P value of the film on the scratched electrode was still high, 98.8%. The anodic process of Fe corrosion markedly was suppressed by the formation of a passive film at the scratched surface with molybdate ion (MoO{sub 4}{sup {minus}}) incorporated in the polymer film, resulting in a self-healing activity of the film.

  14. Hybrid self-healing matrix using core-shell nanofibers and capsuleless microdroplets.

    PubMed

    Lee, Min Wook; An, Seongpil; Lee, Changmin; Liou, Minho; Yarin, Alexander L; Yoon, Sam S

    2014-07-01

    In this work, we developed novel self-healing anticorrosive hierarchical coatings that consist of several components. Namely, as a skeleton we prepared a core-shell nanofiber mat electrospun from emulsions of cure material (dimethyl methylhydrogen siloxane) in a poly(acrylonitrile) (PAN) solution in dimethylformamide. In these nanofibers, cure is in the core, while PAN is in the shell. The skeleton deposited on a protected surface is encased in an epoxy-based matrix, which contains emulsified liquid droplets of dimethylvinyl-terminated dimethylsiloxane resin monomer. When such hierarchical coatings are damaged, cure is released from the nanofiber cores and the resin monomer, released from the damaged matrix, is polymerized in the presence of cure. This polymerization and solidification process takes about 1-2 days and eventually heals the damaged material when solid poly(dimethylsiloxane) resin is formed. The self-healing effect was demonstrated using an electrochemical analogue of the scanning vibrating electrode technique. Damaged samples were left for 2 days. After that, the electric current through a damaged coating was found to be negligibly small for the samples with self-healing properties. On the other hand, for the samples without self-healing properties, the electric current was significant.

  15. Self-healing multilayer polyelectrolyte composite film with chitosan and poly(acrylic acid).

    PubMed

    Zhu, Yanxi; Xuan, Hongyun; Ren, Jiaoyu; Ge, Liqin

    2015-11-21

    If self-healing materials can be prepared via simple technology and methods using nontoxic materials, this would be a great step forward in the creation of environmentally friendly self-healing materials. In this paper, the specific structural parameters of the various hydrogen bonds between chitosan (CS) and polyacrylic acid (PAA) were calculated. Then, multilayer polyelectrolyte films were fabricated with CS and PAA based on layer-by-layer (LbL) self-assembly technology at different pH values. The possible influence of pH on the (CS/PAA) × 30 multilayer polyelectrolyte film was investigated. The results show that the interactions between CS and PAA, swelling capacity, microstructure, wettability, and self-healing ability are all governed by the pH of the CS solution. When the pH value of the CS solution is 3.0, the prepared multilayer polyelectrolyte film (CS3.0/PAA2.8) × 30 has fine-tuned interactions, a network-like structure, good swelling ability, good hydrophilicity, and excellent self-healing ability. This promises to greatly widen the future applications of environmentally friendly materials and bio-materials. PMID:26364567

  16. Geometric optimization of self-healing power capacitor with consideration of multiple factors

    NASA Astrophysics Data System (ADS)

    Wang, Zijian; Yan, Fei; Hua, Zheng; Qi, Lingna; Hou, Zhijian; Xu, Zhiniu

    2016-08-01

    To decrease temperature rise in self-healing power capacitor and lay foundation for improvement of applied voltage and lifetime, the influence of elements orientation on the temperature distribution of self-healing capacitor is investigated using Fluent15.0 and validated by thermal stability test. Based on the above investigations, the influences of parameters of film, electrode and element on power loss and temperature rise of capacitor are systematically investigated. The results reveal that if geometry and volume of capacitor remain constant, orientation of spray coating has little influence on temperature rise. In view of manufacturing processes, the mode of spray coating close to the large surface should be selected. The power loss will decrease with increasing/decreasing in film thickness/width. Therefore, thicker film should be selected and its width should be less than 75 mm. Temperature rise decreases slowly with element diameter. However, the element diameter should be a moderate value because of the influence of it on the number of self-healing point. A capacitor group with rated voltage of 11/ √{ 3} kV and capacity of 334 kvar is designed and the scheme with the lowest temperature rise is selected. This study provides a reference to self-healing capacitor geometric optimization and lifetime improvement.

  17. Molecular self-healing mechanisms between C60-fullerene and anthracene unveiled by Raman and two-dimensional correlation spectroscopy.

    PubMed

    Geitner, R; Kötteritzsch, J; Siegmann, M; Fritzsch, R; Bocklitz, T W; Hager, M D; Schubert, U S; Gräfe, S; Dietzek, B; Schmitt, M; Popp, J

    2016-07-21

    The self-healing polymer P(LMA-co-MeAMMA) crosslinked with C60-fullerene has been studied by FT-Raman spectroscopy in combination with two-dimensional (2D) correlation analysis and density functional theory calculations. To unveil the molecular changes during the self-healing process mediated by the Diels-Alder equilibrium between 10-methyl-9-anthracenyl groups and C60-fullerene different anthracene-C60-fullerene adducts have been synthesized and characterized by time-, concentration- and temperature-dependent FT-Raman measurements. The self-healing process could be monitored via the C60-fullerene vibrations at 270, 432 and 1469 cm(-1). Furthermore, the detailed analysis of the concentration-dependent FT-Raman spectra point towards the formation of anthracene-C60-fullerene adducts with an unusual high amount of anthracene bound to C60-fullerene in the polymer film, while the 2D correlation analysis of the temperature-dependent Raman spectra suggests a stepwise dissociation of anthracene-C60-fullerene adducts, which are responsible for the self-healing of the polymer. PMID:27327116

  18. Self-Healing Elastin-Bioglass Hydrogels.

    PubMed

    Zeng, Qiongyu; Desai, Malav S; Jin, Hyo-Eon; Lee, Ju Hun; Chang, Jiang; Lee, Seung-Wuk

    2016-08-01

    Tailorable hydrogels that are mechanically robust, injectable, and self-healable, are useful for many biomedical applications including tissue repair and drug delivery. Here we use biological and chemical engineering approaches to develop a novel in situ forming organic/inorganic composite hydrogel with dynamic aldimine cross-links using elastin-like polypeptides (ELP) and bioglass (BG). The resulting ELP/BG biocomposites exhibit tunable gelling behavior and mechanical characteristics in a composition and concentration dependent manner. We also demonstrate self-healing in the ELP/BG hydrogels by successfully reattaching severed pieces as well as through rheology. In addition, we show the strength of genetic engineering to easily customize ELP by fusing cell-stimulating "RGD" peptide motifs. We showed that the resulting composite materials are cytocompatible as they support the cellular growth and attachment. Our robust in situ forming ELP/BG composite hydrogels will be useful as injectable scaffolds for delivering cell and drug molecules to promote soft tissue regeneration in the future. PMID:27380227

  19. Self-healing, an intrinsic property of biomineralization processes.

    PubMed

    Müller, Werner E G; Wang, Xiaohong; Jochum, Klaus Peter; Schröder, Heinz C

    2013-05-01

    The sponge siliceous spicules are formed enzymatically via silicatein, in contrast to other siliceous biominerals. Originally, silicatein had been described as a major structural protein of the spicules that has the property to allow a specific deposition of silica onto their surface. More recently, it had been unequivocally demonstrated that silicatein displays a genuine enzyme activity, initiating and maintaining silica biopolycondensation at low precursor concentrations (<2 mM). Even more, as silicatein becomes embedded into the biosilica polymer, formed by the enzyme, it retains its functionality to enable a controlled biosilica deposition. The protection of silicatein through the biosilica mantel is so strong that it conserves the functionality of the enzyme for thousands of years. The implication of this finding, the preservation of the enzyme function over such long time periods, is that the intrinsic property of silicatein to display its enzymatic activity remains in the biosilica deposits. This self-healing property of sponge biosilica can be utilized to engineer novel hybrid materials, with silicatein as a functional template, which are more resistant toward physical stress and fracture. Those hybrid materials can even be used for the fabrication of silica dielectrics coupled to optical nanowires.

  20. Molecular structure of self-healing polyampholyte hydrogels analyzed from tensile behaviors.

    PubMed

    Sun, Tao Lin; Luo, Feng; Kurokawa, Takayuki; Karobi, Sadia Nazneen; Nakajima, Tasuku; Gong, Jian Ping

    2015-12-28

    Recently, charge balanced polyampholytes (PA) have been found to form tough and self-healing hydrogels. This class of physical hydrogels have a very high equilibrated polymer concentration in water (ca. 40-50 wt%), and are strongly viscoelastic. They are synthesized by random copolymerization of equal amounts of oppositely charged monomers at a high concentration, followed by a dialysis process of the small counter-ions and co-ions in water. The randomly distributed, opposite charges of the polymer form multiple ionic bonds of intra- and inter-chains with strength distribution. The strong inter-chain bonds, stabilized by topological entanglement, serve as quasi-permanent crosslinks, imparting the elasticity, while the weak bonds, both inter- and intra-chains, reversibly break and re-form to dissipate energy to toughen the materials. In this work, we intend to clarify the structure of the physical PA hydrogels from the tensile behaviors of the PA hydrogels. To clarify the structure and its formation mechanism, we analysed the tensile behaviors of the samples before and after the dialysis. We separated the quasi-permanent crosslinking of strong inter-chain bonds and the dynamic crosslinking of weak inter-chain bonds by using a combined model that consists of the Upper Convected Maxwell model and the Gent strain hardening model. The model fitting of the tensile behaviors extracts quantitative structural parameters, including the densities of weak and strong inter-chain bonds and the theoretical finite extensibility of polymer chains. Based on the fitting results of the combined model, the structural parameters of partial chains at a fixed observation time, including the Kuhn number, Kuhn length, and chain conformation, are determined using the scaling theory. The effects of monomer concentration at preparation, the effect of dialysis and the initial strain rate on the dynamic structure of PA gels, are discussed based on these analyses.

  1. Polylactic acid with improved heat deflection temperatures and self-healing properties for durable goods applications.

    PubMed

    Wertz, J T; Mauldin, T C; Boday, D J

    2014-11-12

    A method to recover fracture toughness after failure and increase thermal properties of polylactic acid (PLA) for use within durable goods applications is presented. Microcapsules were incorporated into PLA to form a composite material in which the microcapsules served the dual purpose of (1) releasing self-healing additives to fracture regions and (2) serving as nucleating agents to improve the PLA composite's thermal tolerance. Self-healing was achieved though embedment of dicyclopentadiene-filled microcapsules and Grubbs' first generation ruthenium metathesis catalyst, the former being autonomically released into damage volumes and undergoing polymerization in the presence of the catalyst. This approach led to up to 84% recovery of the polymer composite's initial fracture toughness. Additionally, PLA's degree of crystallinity and heat deflection temperature were improved by ∼ 11% and ∼ 21 °C, respectively, relative to nonfilled virgin PLA, owing to microcapsule-induced nucleation. The self-healing system developed here overcomes many property limitations of PLA that can potentially lead to its incorporation into various durable goods.

  2. Solution-Blown Core-Shell Self-Healing Nano- and Microfibers.

    PubMed

    Lee, Min Wook; Yoon, Sam S; Yarin, Alexander L

    2016-02-01

    Self-healing microfibers with core-shell geometry were studied. A commercial binary epoxy was encased in solution-blown polymer nano-/microfibers in the 0.2-2.6 μm diameter range. The core-shell microfibers were formed by coaxial nozzles, which encapsulated the epoxy resin and its hardener in separate cores. Solution blowing, the fiber-forming process used in this work, was at least 30 times faster than the electrospinning method used previously and has already been scaled up to the industrial level. These core-shell microfibers show self-healing capability, in which epoxy and hardener are released from the cores of damaged fibers, resulting in polymerization. The epoxy used had a higher strength and shorter solidification time than poly(dimethylsiloxane) (PDMS) used previously. Also, the larger fiber diameters in the present study facilitated faster release of the epoxy resin and its hardener from the fiber cores, shortening the solidification time in comparison to the previous studies. Blister tests were conducted, which measured the adhesion energy of microfiber mats to substrates and the cohesion energy between layers of microfiber mats before and after fatigue damage followed by self-healing. PMID:26836581

  3. Processing and Damage Tolerance of Continuous Carbon Fiber Composites Containing Puncture Self-Healing Thermoplastic Matrix

    NASA Technical Reports Server (NTRS)

    Grimsley, Brian W.; Gordon, Keith L.; Czabaj, Michael W.; Cano, Roberto J.; Siochi, Emilie J.

    2012-01-01

    Research at NASA Langley Research Center (NASA LaRC) has identified several commercially available thermoplastic polymers that self-heal after ballistic impact and through-penetration. One of these resins, polybutadiene graft copolymer (PB(sub g)), was processed with unsized IM7 carbon fibers to fabricate reinforced composite material for further evaluation. Temperature dependent characteristics, such as the degradation point, glass transition (T(sub g)), and viscosity of the PBg polymer were characterized by thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), and dynamic parallel plate rheology. The PBg resin was processed into approximately equal to 22.0 cm wide unidirectional prepreg tape in the NASA LaRC Advanced Composites Processing Research Laboratory. Data from polymer thermal characterization guided the determination of a processing cycle used to fabricate quasi-isotropic 32-ply laminate panels in various dimensions up to 30.5cm x 30.5cm in a vacuum press. The consolidation quality of these panels was analyzed by optical microscopy and acid digestion. The process cycle was further optimized based on these results and quasi-isotropic, [45/0/-45/90]4S, 15.24cm x 15.24cm laminate panels were fabricated for mechanical property characterization. The compression strength after impact (CAI) of the IM7/pBG composites was measured both before and after an elevated temperature and pressure healing cycle. The results of the processing development effort of this composite material as well as the results of the mechanical property characterization are presented in this paper.

  4. Assessment of Composite Delamination Self-Healing Via Micro-Encapsulation

    NASA Technical Reports Server (NTRS)

    O'Brien, T. Kevin; White, Scott R.

    2008-01-01

    Composite skin/stringer flange debond specimens manufactured from composite prepreg containing interleaf layers with a polymer based healing agent encapsulated in thin walled spheres were tested. As a crack develops and grows in the base polymer, the spheres fracture releasing the healing agent. The agent reacts with catalyst and polymerizes healing the crack. In addition, through-thickness reinforcement, in the form of pultruded carbon z-pins were included near the flange tips to improve the resistance to debonding. Specimens were manufactured with 14 plies in the skin and 10 plies in the stiffener flange. Three-point bend tests were performed to measure the skin/stiffener debonding strength and the recovered strength after healing. The first three tests performed indicated no healing following unloading and reloading. Micrographs showed that delaminations could migrate to the top of the interleaf layer due to the asymmetric loading, and hence, bypass most of the embedded capsules. For two subsequent tests, specimens were clamped in reverse bending before reloading. In one case, healing was observed as evidenced by healing agent that leaked to the specimen edge forming a visible "scar". The residual strength measured upon reloading was 96% of the original strength indicating healing had occurred. Hence, self-healing is possible in fiber reinforced composite material under controlled conditions, i.e., given enough time and contact with pressure on the crack surfaces. The micro-encapsulation technique may prove more robust when capsule sizes can be produced that are small enough to be embedded in the matrix resin without the need for using an interleaf layer. However, in either configuration, the amount of healing that can occur may be limited to the volume of healing agent available relative to the crack volume that must be filled.

  5. Damage initiated self-healing in ionomer blends

    NASA Astrophysics Data System (ADS)

    Rahman, Md. Arifur; Penco, Maurizio; Spagnoli, Gloria; Peroni, Isabella; Ramorino, Giorgio; Sartore, Luciana; Bignotti, Fabio; Landro, Luca Di

    2012-07-01

    The development and understanding of self-healing mechanisms have been investigated in blends of ionomers (Poly(ethyelene-co-methacrylic acid), sodium & zinc ions) (EMNa & EMZn) containing both elastomers (Epoxidized natural rubbers (ENR) and cis-1,4-Polyisoprene (PISP)) and crystalline component (Poly(vinly alcohol-co-ethylene) [PVAcE]) as secondary phases. All the blends were prepared by melt-blending and self-healing behavior was studied in ballistic puncture tests. Self-healing behavior of each material was evaluated by observing the impact zones under a stereo-optical microscope and the micrographic results were further supported by the fluid flow test in the punctured zones. Interestingly, ENR50 blends of sodium ion containing ionomers exhibited complete self-repairing behavior while zinc ion containing ionomer showed limited mending but EMNa/ENR25 and EMNa/PISP blends did not show any self-healing behavior following the damage. On the other hand, a composition dependent healing behavior was observed in the EMNa/PVAcE blends where healing was observed up to 30wt% PVAcE containing blends. The chemical structure studied by FTIR analysis showed that both ion content of ionomer and functionality of ENR have significant influence on the self-repairing behavior of blends. TEM analysis revealed that self-healing occurs in the blends when the dispersed phase has a dimension of 100 to 400 nm.

  6. Self-healing concrete by use of microencapsulated bacterial spores

    SciTech Connect

    Wang, J.Y.; Soens, H.; Verstraete, W.; De Belie, N.

    2014-02-15

    Microcapsules were applied to encapsulate bacterial spores for self-healing concrete. The viability of encapsulated spores and the influence of microcapsules on mortar specimens were investigated first. Breakage of the microcapsules upon cracking was verified by Scanning Electron Microscopy. Self-healing capacity was evaluated by crack healing ratio and the water permeability. The results indicated that the healing ratio in the specimens with bio-microcapsules was higher (48%–80%) than in those without bacteria (18%–50%). The maximum crack width healed in the specimens of the bacteria series was 970 μm, about 4 times that of the non-bacteria series (max 250 μm). The overall water permeability in the bacteria series was about 10 times lower than that in non-bacteria series. Wet–dry cycles were found to stimulate self-healing in mortar specimens with encapsulated bacteria. No self-healing was observed in all specimens stored at 95%RH, indicating that the presence of liquid water is an essential component for self-healing.

  7. Quantitative comparison of self-healing ability between Bessel–Gaussian beam and Airy beam

    SciTech Connect

    Wen, Wei; Chu, Xiuxiang

    2015-09-15

    The self-healing ability during propagation process is one of the most important properties of non-diffracting beams. This ability has crucial advantages to light sheet-based microscopy to reduce scattering artefacts, increase the quality of the image and enhance the resolution of microscopy. Based on similarity between two infinite-dimensional complex vectors in Hilbert space, the ability to a Bessel–Gaussian beam and an Airy beam have been studied and compared. Comparing the evolution of the similarity of Bessel–Gaussian beam with Airy beam under the same conditions, we find that Bessel–Gaussian beam has stronger self-healing ability and is more stable than that of Airy beam. To confirm this result, the intensity profiles of Bessel–Gaussian beam and Airy beam with different similarities are numerically calculated and compared.

  8. Thermosetting epoxy resin/thermoplastic system with combined shape memory and self-healing properties

    NASA Astrophysics Data System (ADS)

    Yao, Yongtao; Wang, Jingjie; Lu, Haibao; Xu, Ben; Fu, Yongqing; Liu, Yanju; Leng, Jinsong

    2016-01-01

    A novel and facile strategy was proposed to construct a thermosetting/thermoplastic system with both shape memory and self-healing properties based on commercial epoxy resin and poly(ɛ-caprolactone)-PCL. Thermoplastic material is capable of re-structuring and changing the stiffness/modulus when the temperature is above melting temperature. PCL microfiber was used as a plasticizer in epoxy resin-based blends, and served as a ‘hard segment’ to fix a temporary shape of the composites during shape memory cycles. In this study, the electrospun PCL membrane with a porous network structure enabled a homogenous PCL fibrous distribution and optimized interaction between fiber and epoxy resin. The self-healing capability is achieved by phase transition during curing of the composites. The mechanism of the shape memory effect of the thermosetting (rubber)/thermoplastic composite is attributed to the structural design of the thermoplastic network inside the thermosetting resin/rubber matrix.

  9. An electrically and mechanically self-healing composite with pressure- and flexion-sensitive properties for electronic skin applications.

    PubMed

    Tee, Benjamin C-K; Wang, Chao; Allen, Ranulfo; Bao, Zhenan

    2012-12-01

    Pressure sensitivity and mechanical self-healing are two vital functions of the human skin. A flexible and electrically conducting material that can sense mechanical forces and yet be able to self-heal repeatably can be of use in emerging fields such as soft robotics and biomimetic prostheses, but combining all these properties together remains a challenging task. Here, we describe a composite material composed of a supramolecular organic polymer with embedded nickel nanostructured microparticles, which shows mechanical and electrical self-healing properties at ambient conditions. We also show that our material is pressure- and flexion-sensitive, and therefore suitable for electronic skin applications. The electrical conductivity can be tuned by varying the amount of nickel particles and can reach values as high as 40 S cm(-1). On rupture, the initial conductivity is repeatably restored with ∼90% efficiency after 15 s healing time, and the mechanical properties are completely restored after ∼10 min. The composite resistance varies inversely with applied flexion and tactile forces. These results demonstrate that natural skin's repeatable self-healing capability can be mimicked in conductive and piezoresistive materials, thus potentially expanding the scope of applications of current electronic skin systems.

  10. An electrically and mechanically self-healing composite with pressure- and flexion-sensitive properties for electronic skin applications

    NASA Astrophysics Data System (ADS)

    Tee, Benjamin C.-K.; Wang, Chao; Allen, Ranulfo; Bao, Zhenan

    2012-12-01

    Pressure sensitivity and mechanical self-healing are two vital functions of the human skin. A flexible and electrically conducting material that can sense mechanical forces and yet be able to self-heal repeatably can be of use in emerging fields such as soft robotics and biomimetic prostheses, but combining all these properties together remains a challenging task. Here, we describe a composite material composed of a supramolecular organic polymer with embedded nickel nanostructured microparticles, which shows mechanical and electrical self-healing properties at ambient conditions. We also show that our material is pressure- and flexion-sensitive, and therefore suitable for electronic skin applications. The electrical conductivity can be tuned by varying the amount of nickel particles and can reach values as high as 40 S cm-1. On rupture, the initial conductivity is repeatably restored with ~90% efficiency after 15 s healing time, and the mechanical properties are completely restored after ~10 min. The composite resistance varies inversely with applied flexion and tactile forces. These results demonstrate that natural skin's repeatable self-healing capability can be mimicked in conductive and piezoresistive materials, thus potentially expanding the scope of applications of current electronic skin systems.

  11. Hydrophobic Light-to-Heat Conversion Membranes with Self-Healing Ability for Interfacial Solar Heating.

    PubMed

    Zhang, Lianbin; Tang, Bo; Wu, Jinbo; Li, Renyuan; Wang, Peng

    2015-09-01

    Self-healing hydrophobic light-to-heat conversion membranes for interfacial solar heating are fabricated by deposition of light-to-heat conversion material of polypyrrole onto a porous stainless-steel mesh, followed by hydrophobic fluoroalkylsilane modification. The mesh-based membranes spontaneously stay at the water-air interface, collect and convert solar light into heat, and locally heat only the water surface for enhanced evaporation.

  12. Impact of self-healing capability on network robustness.

    PubMed

    Shang, Yilun

    2015-04-01

    A wide spectrum of real-life systems ranging from neurons to botnets display spontaneous recovery ability. Using the generating function formalism applied to static uncorrelated random networks with arbitrary degree distributions, the microscopic mechanism underlying the depreciation-recovery process is characterized and the effect of varying self-healing capability on network robustness is revealed. It is found that the self-healing capability of nodes has a profound impact on the phase transition in the emergence of percolating clusters, and that salient difference exists in upholding network integrity under random failures and intentional attacks. The results provide a theoretical framework for quantitatively understanding the self-healing phenomenon in varied complex systems. PMID:25974544

  13. Impact of self-healing capability on network robustness

    NASA Astrophysics Data System (ADS)

    Shang, Yilun

    2015-04-01

    A wide spectrum of real-life systems ranging from neurons to botnets display spontaneous recovery ability. Using the generating function formalism applied to static uncorrelated random networks with arbitrary degree distributions, the microscopic mechanism underlying the depreciation-recovery process is characterized and the effect of varying self-healing capability on network robustness is revealed. It is found that the self-healing capability of nodes has a profound impact on the phase transition in the emergence of percolating clusters, and that salient difference exists in upholding network integrity under random failures and intentional attacks. The results provide a theoretical framework for quantitatively understanding the self-healing phenomenon in varied complex systems.

  14. Self-Healing Metals and Metal Matrix Composites

    NASA Astrophysics Data System (ADS)

    Ferguson, J. B.; Schultz, Benjamin F.; Rohatgi, Pradeep K.

    2014-06-01

    Self-healing in inorganic materials is a relatively new area in materials science and engineering that draws inspiration from biological systems that can self-repair damage. This article reviews the preliminary attempts to impart self-healing behavior to metals. Several challenges yet exist in the development of metallic alloys that can self-repair damage, including surface bonding issues, such as liquid/solid contact angle (wetting) and oxidation, and practical issues, such as capillary pressure for delivery of a liquid metal to a damaged area or crack, and the overall mechanical properties of a composite system. Although the applied research approaches reviewed have obtained marginal success, the development of self-healing metallic systems has the potential to benefit a wide range of industrial applications and thus deserves greater investment in fundamental research.

  15. Generation of self-healing and transverse accelerating optical vortices

    NASA Astrophysics Data System (ADS)

    Wei, Bing-Yan; Chen, Peng; Ge, Shi-Jun; Duan, Wei; Hu, Wei; Lu, Yan-Qing

    2016-09-01

    Self-healing and transverse accelerating optical vortices are generated via modulating Gaussian beams through subsequent liquid crystal q-plate and polarization Airy mask. We analyze the propagation dynamics of these vortex Airy beams, and find that they possess the features of both optical vortices and Airy beams. Topological charges and characteristics of nondiffraction, self-healing, and transverse acceleration are experimentally verified. In addition, vortex Airy beams with both topological charge and radial index are demonstrated and mode switch among Gaussian, vortex, vector, Airy beams and their combinations can be acquired easily. Our design provides a flexible and highly efficient way to generate unique optical vortices with self-healing and transverse acceleration properties, and facilitates prospective applications in optics and photonics.

  16. Self-imaging, self-healing beams generated by photorefractive volume holography

    NASA Astrophysics Data System (ADS)

    Manigo, Jonathan P.; Guerrero, Raphael A.

    2015-10-01

    Self-imaging beams consisting of three-dimensional intensity voids are generated via photorefractive volume holography. Reconstruction of a volume hologram recorded at 594 nm is performed with a Bessel readout beam. The holographic output is similar in appearance to a Bessel beam, with the central spot oscillating between maximum and zero intensity over a propagation distance of 10 to 55 cm. The oscillation period for the on-axis intensity is 30 cm. The reconstruction is capable of self-healing, with a fully recovered central core after the beam propagates 40 cm. Dual-wavelength reconstruction at 632.8 nm produces an output beam with similar self-imaging and self-healing properties. A theoretical framework based on the interference of a plane wave and a Bessel beam simultaneously reconstructed from a volume hologram is able to describe our experimental results.

  17. Damage, Self-Healing, and Hysteresis in Spider Silks

    PubMed Central

    De Tommasi, D.; Puglisi, G.; Saccomandi, G.

    2010-01-01

    Abstract In this article, we propose a microstructure-based continuum model to describe the material behavior of spider silks. We suppose that the material is composed of a soft fraction with entropic elasticity and a hard, damageable fraction. The hard fraction models the presence of stiffer, crystal-rich, oriented regions and accounts for the effect of softening induced by the breaking of hydrogen bonds. To describe the observed presence of crystals with different size, composition, and orientation, this hard fraction is modeled as a distribution of materials with variable properties. The soft fraction describes the remaining regions of amorphous material and is here modeled as a wormlike chain. During stretching, we consider the effect of bond-breaking as a transition from the hard- to the soft-material phase. As we demonstrate, a crucial effect of bond-breaking that accompanies the softening of the material is an increase in contour length associated with chains unraveling. The model describes also the self-healing properties of the material by assuming partial bond reconnection upon unloading. Despite its simplicity, the proposed mechanical system reproduces the main experimental effects observed in cyclic loading of spider silks. Moreover, our approach is amenable to two- or three-dimensional extensions and may prove to be a useful tool in the field of microstructure optimization for bioinspired materials. PMID:20441758

  18. Self-Healing in Mollusks, Lessons from Biology

    NASA Astrophysics Data System (ADS)

    Hinkley, Karen M.

    We will study major mechanisms of self-healing in Molluscan hard tissues taking lessons from biology. We are interested in mollusks because of the ease in monitoring the healing process using existing characterization techniques. The ability to self-heal their non-living hard tissues externally, make mollusks remarkable from both an evolutionary perspective and a materials perspective. Biological systems have evolved to repair their own hard tissues such as bone and dentin, but bone and tooth repair is accomplished with a specific blood supply for nutrient delivery at the cellular level. The Molluscan process of "self-healing" takes place in an aqueous environment where there are no direct supplies of nutrients. In fact the nutrients may be washed away from the injury site with the flow of water. This self-healing process is interesting to materials scientists as a possible model for synthesizing new Smart materials that do not need an in situ location for growth and gaining insight into biomineralization and its interaction with the organics regulating the process. This project will focus on two objectives firstly understanding the growth rates of shell deposition, growth and scar formation and secondly characterizing the biomineralization, microstructure, and mechanical properties of scar tissue as compared to normal tissue. By performing controlled injury experiments on two mollusk species, we can initiate the self-healing process and characterize all phases of its development. Using mechanical tests including micro-bend tests and atomic force microscopy with nanoindentation we can determine the hardness, micro-hardness, Young's modulus, strength and ductility of the self-healed tissue. In addition, scanning electron microscopy, transmission electron microscopy, atomic force microscopy, and x-ray crystallography will be used to determine the characteristics of the self-healed tissues. Molluscan self-healing is an excellent model for a self-assembly, highly

  19. Self-Healing Spongy Coating for Drug "Cocktail" Delivery.

    PubMed

    Chen, Xia-chao; Ren, Ke-feng; Lei, Wen-xi; Zhang, Jia-hui; Martins, M Cristina L; Barbosa, Mário A; Ji, Jian

    2016-02-01

    Optimized ratio in the codelivery of therapeutics is of crucial importance to promote the synergism rather than the antagonistic effects. In this study, a self-healing spongy coating was described to facilitate the surface-mediated delivery of drug "cocktails" proportionally. The formation of spongy structures within the coating was achieved by acidic treatment and freeze-drying. Various drug combinations can be readily integrated through wicking method and subsequent micropore self-healing. The ratio of drug loading can be precisely regulated by the composition of loading solution and the embedded drugs were released in proportion according to the initial ratio of drug combination. PMID:26844588

  20. Fast-acting self-healing metallic fuse.

    NASA Technical Reports Server (NTRS)

    Schwartz, F. C.; Renton, C. A.; Rabinovici, B.

    1971-01-01

    Description of a fast-acting nonmechanical self-healing mercury fuse capable of protecting a high current circuit or device from overcurrent fault damages. Basically the self-healing fuse consists of two enclosed mercury reservoirs connected by a fine capillary tube filled with mercury that serves as the fusing element. It is pointed out that a better understanding of the energy conversion process involved in the operation of the device could help explore other device configurations (such as a tapering geometry and use of magnetic field to drive the arc into the fuse wall on inductive loads, etc.) and thus extend the range of capabilities for this type of protective device.

  1. Bioinspired engineering study of Plantae vascules for self-healing composite structures

    PubMed Central

    Trask, R. S.; Bond, I. P.

    2010-01-01

    This paper presents the first conceptual study into creating a Plantae-inspired vascular network within a fibre-reinforced polymer composite laminate, which provides an ongoing self-healing functionality without incurring a mass penalty. Through the application of a ‘lost-wax’ technique, orthogonal hollow vascules, inspired by the ‘ray cell’ structures found in ring porous hardwoods, were successfully introduced within a carbon fibre-reinforced epoxy polymer composite laminate. The influence on fibre architecture and mechanical behaviour of single vascules (located on the laminate centreline) when aligned parallel and transverse to the local host ply was characterized experimentally using a compression-after-impact test methodology. Ultrasonic C-scanning and high-resolution micro-CT X-ray was undertaken to identify the influence of and interaction between the internal vasculature and impact damage. The results clearly show that damage morphology is influenced by vascule orientation and that a 10 J low-velocity impact damage event is sufficient to breach the vasculature; a prerequisite for any subsequent self-healing function. The residual compressive strength after a 10 J impact was found to be dependent upon vascule orientation. In general, residual compressive strength decreased to 70 per cent of undamaged strength when vasculature was aligned parallel to the local host ply and a value of 63 per cent when aligned transverse. This bioinspired engineering study has illustrated the potential that a vasculature concept has to offer in terms of providing a self-healing function with minimum mass penalty, without initiating premature failure within a composite structure. PMID:19955122

  2. Functional Metal Matrix Composites: Self-lubricating, Self-healing, and Nanocomposites-An Outlook

    NASA Astrophysics Data System (ADS)

    Dorri Moghadam, Afsaneh; Schultz, Benjamin F.; Ferguson, J. B.; Omrani, Emad; Rohatgi, Pradeep K.; Gupta, Nikhil

    2014-06-01

    Many different types of advanced metal matrix composites are now available, some of which possess functional properties. Recent work on particle-reinforced, self-lubricating and self-healing metals and metal matrix nanocomposites (MMNCs) synthesized by solidification synthesis is reviewed. Particle-based MMNCs have been developed by several modern processing tools based on either solid- or liquid-phase synthesis techniques that are claimed to exhibit exciting mechanical properties including improvements of modulus, yield strength, and ultimate tensile strength. This article presents a brief and objective review of the work done over the last decade to identify the challenges and future opportunities in the area of functional nanocomposites. Increasing interest in lightweight materials has resulted in studies on hollow particle-filled metal matrix syntactic foams. Syntactic foams seem especially suitable for development with functional properties such as self-healing and self-lubrication. The metal matrix micro and nanocomposites, and syntactic foams having combinations of ultrahigh strength and wear resistance, self-lubricating, and/or self-healing properties can lead to increased energy efficiency, reliability, comfort of operation, reparability, and safety of vehicles. The focus of the present review is aluminum and magnesium matrix functional materials.

  3. Polymer based tunneling sensor

    NASA Technical Reports Server (NTRS)

    Cui, Tianhong (Inventor); Wang, Jing (Inventor); Zhao, Yongjun (Inventor)

    2006-01-01

    A process for fabricating a polymer based circuit by the following steps. A mold of a design is formed through a lithography process. The design is transferred to a polymer substrate through a hot embossing process. A metal layer is then deposited over at least part of said design and at least one electrical lead is connected to said metal layer.

  4. Use of composite materials, health monitoring and self-healing concepts to refurbish our civil and military infrastructure.

    SciTech Connect

    Roach, Dennis Patrick; Delong, Waylon Anthony; White, Scott; Yepez, Esteban; Rackow, Kirk A.; Reedy, Earl David, Jr.

    2007-09-01

    An unavoidable by-product of a metallic structure's use is the appearance of crack, corrosion, erosion and other flaws. Economic barriers to the replacement of these structures have created an aging civil and military infrastructure and placed even greater demands on efficient and safe repair and inspection methods. As a result of Homeland Security issues and these aging infrastructure concerns, increased attention has been focused on the rapid repair and preemptive reinforcement of structures such as buildings and bridges. This Laboratory Directed Research and Development (LDRD) program established the viability of using bonded composite patches to repair metallic structures. High modulus fiber-reinforced polymer (FRP) material may be used in lieu of mechanically fastened metallic patches or welds to reinforce or repair damaged structures. Their use produces a wide array of engineering and economic advantages. Current techniques for strengthening steel structures have several drawbacks including requiring heavy equipment for installation, poor fatigue performance, and the need for ongoing maintenance due to continued corrosion attack or crack growth. The use of bonded composite doublers has the potential to correct the difficulties associated with current repair techniques and the ability to be applied where there are currently no rehabilitation options. Applications include such diverse structures as: buildings, bridges, railroad cars, trucks and other heavy machinery, steel power and communication towers, pipelines, factories, mining equipment, ships, tanks and other military vehicles. This LDRD also proved the concept of a living infrastructure by developing custom sensors and self-healing chemistry and linking this technology with the application of advanced composite materials. Structural Health Monitoring (SHM) systems and mountable, miniature sensors were designed to continuously or periodically assess structural integrity. Such systems are able to detect

  5. Self-healing chemistry enables the stable operation of silicon microparticle anodes for high-energy lithium-ion batteries.

    PubMed

    Wang, Chao; Wu, Hui; Chen, Zheng; McDowell, Matthew T; Cui, Yi; Bao, Zhenan

    2013-12-01

    The ability to repair damage spontaneously, which is termed self-healing, is an important survival feature in nature because it increases the lifetime of most living creatures. This feature is highly desirable for rechargeable batteries because the lifetime of high-capacity electrodes, such as silicon anodes, is shortened by mechanical fractures generated during the cycling process. Here, inspired by nature, we apply self-healing chemistry to silicon microparticle (SiMP) anodes to overcome their short cycle-life. We show that anodes made from low-cost SiMPs (~3-8 µm), for which stable deep galvanostatic cycling was previously impossible, can now have an excellent cycle life when coated with a self-healing polymer. We attain a cycle life ten times longer than state-of-art anodes made from SiMPs and still retain a high capacity (up to ~3,000 mA h g(-1)). Cracks and damage in the coating during cycling can be healed spontaneously by the randomly branched hydrogen-bonding polymer used.

  6. A strong and stretchable self-healing film with self-activated pressure sensitivity for potential artificial skin applications

    PubMed Central

    Hou, Chengyi; Huang, Tao; Wang, Hongzhi; Yu, Hao; Zhang, Qinghong; Li, Yaogang

    2013-01-01

    Artificial skin, which mimics the functions of natural skin, will be very important in the future for robots used by humans in daily life. However, combining skin's pressure sensitivity and mechanical self-healing properties in a man-made material remains a challenging task. Here, we show that graphene and polymers can be integrated into a thin film which mimics both the mechanical self-healing and pressure sensitivity behavior of natural skin without any external power supply. Its ultimate strain and tensile strength are even two and ten times larger than the corresponding values of human skin, respectively. It also demonstrates highly stable sensitivity to a very light touch (0.02 kPa), even in bending or stretching states. PMID:24190511

  7. A strong and stretchable self-healing film with self-activated pressure sensitivity for potential artificial skin applications

    NASA Astrophysics Data System (ADS)

    Hou, Chengyi; Huang, Tao; Wang, Hongzhi; Yu, Hao; Zhang, Qinghong; Li, Yaogang

    2013-11-01

    Artificial skin, which mimics the functions of natural skin, will be very important in the future for robots used by humans in daily life. However, combining skin's pressure sensitivity and mechanical self-healing properties in a man-made material remains a challenging task. Here, we show that graphene and polymers can be integrated into a thin film which mimics both the mechanical self-healing and pressure sensitivity behavior of natural skin without any external power supply. Its ultimate strain and tensile strength are even two and ten times larger than the corresponding values of human skin, respectively. It also demonstrates highly stable sensitivity to a very light touch (0.02 kPa), even in bending or stretching states.

  8. A strong and stretchable self-healing film with self-activated pressure sensitivity for potential artificial skin applications.

    PubMed

    Hou, Chengyi; Huang, Tao; Wang, Hongzhi; Yu, Hao; Zhang, Qinghong; Li, Yaogang

    2013-01-01

    Artificial skin, which mimics the functions of natural skin, will be very important in the future for robots used by humans in daily life. However, combining skin's pressure sensitivity and mechanical self-healing properties in a man-made material remains a challenging task. Here, we show that graphene and polymers can be integrated into a thin film which mimics both the mechanical self-healing and pressure sensitivity behavior of natural skin without any external power supply. Its ultimate strain and tensile strength are even two and ten times larger than the corresponding values of human skin, respectively. It also demonstrates highly stable sensitivity to a very light touch (0.02 kPa), even in bending or stretching states. PMID:24190511

  9. Design of Self-Healing Supramolecular Rubbers by Introducing Ionic Cross-Links into Natural Rubber via a Controlled Vulcanization.

    PubMed

    Xu, Chuanhui; Cao, Liming; Lin, Baofeng; Liang, Xingquan; Chen, Yukun

    2016-07-13

    Introducing ionic associations is one of the most effective approaches to realize a self-healing behavior for rubbers. However, most of commercial rubbers are nonpolar rubbers without now available functional groups to be converted into ionic groups. In this paper, our strategy was based on a controlled peroxide-induced vulcanization to generate massive ionic cross-links via polymerization of zinc dimethacrylate (ZDMA) in natural rubber (NR) and exploited it as a potential self-healable material. We controlled vulcanization process to retard the formation of covalent cross-link network, and successfully generated a reversible supramolecular network mainly constructed by ionic cross-links. Without the restriction of covalent cross-linkings, the NR chains in ionic supramolecular network had good flexibility and mobility. The nature that the ionic cross-links was easily reconstructed and rearranged facilitating the self-healing behavior, thereby enabling a fully cut sample to rejoin and retain to its original properties after a suitable self-healing process at ambient temperature. This study thus demonstrates a feasible approach to impart an ionic association induced self-healing function to commercial rubbers without ionic functional groups.

  10. Design of Self-Healing Supramolecular Rubbers by Introducing Ionic Cross-Links into Natural Rubber via a Controlled Vulcanization.

    PubMed

    Xu, Chuanhui; Cao, Liming; Lin, Baofeng; Liang, Xingquan; Chen, Yukun

    2016-07-13

    Introducing ionic associations is one of the most effective approaches to realize a self-healing behavior for rubbers. However, most of commercial rubbers are nonpolar rubbers without now available functional groups to be converted into ionic groups. In this paper, our strategy was based on a controlled peroxide-induced vulcanization to generate massive ionic cross-links via polymerization of zinc dimethacrylate (ZDMA) in natural rubber (NR) and exploited it as a potential self-healable material. We controlled vulcanization process to retard the formation of covalent cross-link network, and successfully generated a reversible supramolecular network mainly constructed by ionic cross-links. Without the restriction of covalent cross-linkings, the NR chains in ionic supramolecular network had good flexibility and mobility. The nature that the ionic cross-links was easily reconstructed and rearranged facilitating the self-healing behavior, thereby enabling a fully cut sample to rejoin and retain to its original properties after a suitable self-healing process at ambient temperature. This study thus demonstrates a feasible approach to impart an ionic association induced self-healing function to commercial rubbers without ionic functional groups. PMID:27337545

  11. Mussel-Inspired Materials: Self-Healing through Coordination Chemistry.

    PubMed

    Krogsgaard, Marie; Nue, Vicki; Birkedal, Henrik

    2016-01-18

    Improved understanding of the underwater attachment strategy of the blue mussels and other marine organisms has inspired researchers to find new routes to advanced materials. Mussels use polyphenols, such as the catechol-containing amino acid 3,4-dihydroxyphenylalanine (DOPA), to attach to surfaces. Catechols and their analogues can undergo both oxidative covalent cross-linking under alkaline conditions and take part in coordination chemistry. The former has resulted in the widespread use of polydopamine and related materials. The latter is emerging as a tool to make self-healing materials due to the reversible nature of coordination bonds. We review how mussel-inspired materials have been made with a focus on the less developed use of metal coordination and illustrate how this chemistry can be widely to make self-healing materials.

  12. Self-healing flexible laminates for resealing of puncture damage

    NASA Astrophysics Data System (ADS)

    Beiermann, B. A.; Keller, M. W.; Sottos, N. R.

    2009-08-01

    A flexible self-healing system capable of healing puncture damage has been manufactured. Our material consists of three layers: a poly(dimethyl siloxane) (PDMS) composite, embedded with a self-healing microcapsule system, sandwiched between two layers of poly(urethane) coated nylon. The total structure thickness ranges between 0.84 and 1.5 mm. A protocol is established in which samples are damaged using a hypodermic needle or a razor blade, and a successful heal is defined as the ability to reseal the damage to withstand a pressure differential across the laminate of 103 kPa (~1 atm). Trends in healing success are analyzed as a function of microcapsule size, self-healing layer thickness, and puncture diameter. Healing varied significantly with microcapsule size, with the maximum healing success rate (100% successfully healed) occurring in samples with 220 µm microcapsules and a puncture diameter of 0.49 mm. For this puncture size, an increase in microcapsule diameter corresponds to a decrease in healing efficiency. However, samples with larger microcapsules (up to 500 µm avg.) demonstrate more effective healing for larger puncture diameters, up to 1.61 mm. Additionally, healing increased with composite layer thickness, and decreased with increasing puncture hole size.

  13. Self-Healing Conductive Injectable Hydrogels with Antibacterial Activity as Cell Delivery Carrier for Cardiac Cell Therapy.

    PubMed

    Dong, Ruonan; Zhao, Xin; Guo, Baolin; Ma, Peter X

    2016-07-13

    Cell therapy is a promising strategy to regenerate cardiac tissue for myocardial infarction. Injectable hydrogels with conductivity and self-healing ability are highly desirable as cell delivery vehicles for cardiac regeneration. Here, we developed self-healable conductive injectable hydrogels based on chitosan-graft-aniline tetramer (CS-AT) and dibenzaldehyde-terminated poly(ethylene glycol) (PEG-DA) as cell delivery vehicles for myocardial infarction. Self-healed electroactive hydrogels were obtained after mixing CS-AT and PEG-DA solutions at physiological conditions. Rapid self-healing behavior was investigated by rheometer. Swelling behavior, morphology, mechanical strength, electrochemistry, conductivity, adhesiveness to host tissue and antibacterial property of the injectable hydrogels were fully studied. Conductivity of the hydrogels is ∼10(-3) S·cm(-1), which is quite close to native cardiac tissue. Proliferation of C2C12 myoblasts in the hydrogel showed its good biocompatibility. After injection, viability of C2C12 cells in the hydrogels showed no significant difference with that before injection. Two different cell types were successfully encapsulated in the hydrogels by self-healing effect. Cell delivery profile of C2C12 myoblasts and H9c2 cardiac cells showed a tunable release rate, and in vivo cell retention in the conductive hydrogels was also studied. Subcutaneous injection and in vivo degradation of the hydrogels demonstrated their injectability and biodegradability. Together, these self-healing conductive biodegradable injectable hydrogels are excellent candidates as cell delivery vehicle for cardiac repair. PMID:27311127

  14. Gamma Irradiation of Active Self-healing PLGA Microspheres for Efficient Aqueous Encapsulation of Vaccine Antigens

    PubMed Central

    Desai, Kashappa-Goud H.; Kadous, Samer; Schwendeman, Steven P.

    2013-01-01

    Purpose To investigate the effect of γ-irradiation of poly(lactic-co-glycolic acid) (PLGA)/Al(OH)3/0 or 5 wt% diethyl phthalate (DEP) microspheres for active self-healing encapsulation of vaccine antigens. Methods Microspheres were irradiated with 60Co at 2.5 and 1.8 MRad and 0.37 and 0.20 MRad/h. Encapsulation of tetanus toxoid (TT) was achieved by mixing Al(OH)3-PLGA microspheres with TT solution at 10-38°C. Electron paramagnetic resonance (EPR) spectroscopy was used to examine free radical formation. Glass transition temperature (Tg) and molecular weight of PLGA was measured by differential scanning calorimetry and gel permeation chromatography, respectively. Loading and release of TT were examined by modified Bradford, amino acid analysis, and ELISA assays. Results EPR spectroscopy results indicated absence of free radicals in PLGA microspheres after γ-irradiation. Antigen-sorbing capacity, encapsulation efficiency, and Tg of the polymer were also not adversely affected. When DEP-loaded microspheres were irradiated at 0.2 MRad/h, some PLGA pores healed during irradiation and PLGA healing during encapsulation was suppressed. The molecular weight of PLGA was slightly reduced when DEP-loaded microspheres were irradiated at the same dose rate. These trends were not observed at 0.37 MRad/h. Gamma irradiation slightly increased TT initial burst release. Apart from the slightly higher polymer molecular weight decline caused by higher irradiation dose in case of DEP-loaded microspheres, the small increase in total irradiation dose from 1.8 to 2.5 MRad had insignificant effect on the polymer and microspheres properties analyzed. Conclusion Gamma irradiation is a plausible approach to provide a terminally sterilized, self-healing encapsulation PLGA excipient for vaccine delivery. PMID:23515830

  15. Self-healing supramolecular bioelastomers with shape memory property as a multifunctional platform for biomedical applications via modular assembly.

    PubMed

    Wu, Yaobin; Wang, Ling; Zhao, Xin; Hou, Sen; Guo, Baolin; Ma, Peter X

    2016-10-01

    Mimicking native functional dynamics for traditional biomaterials such as thermoset elastomers is limited due to their lack of responsiveness to biological stimuli and difficulties to incorporate biofunctionalities. Furthermore, the mechanical fracture of traditional thermoset elastomers caused by irreversible covalent bond rupture would lead to their permanent loss of properties. To overcome these challenges, degradable self-healed supramolecular bioelastomers are designed by an elastic poly(glycerol sebacate) (PGS) backbone and multiple hydrogen-bonding ureido-pyrimidinone (UPy) grafts. These supramolecular elastic polymers exhibit efficient self-healing, rapid shape-memory abilities and highly tunable mechanical properties due to the dynamic supramolecular interactions, and perform a good biocompatibility in vitro and a mild host response in vivo. By combining modular approaches, these supramolecular bioelastomers have been further assembled into a multifunctional platform to expand their applications in different biomedical fields. These include a complex 3D scaffold with shape-memory capacity and anisotropic mechanical properties, a controllable drug delivery model via a layer-by-layer technique, a surface antibacterial composite by physical modification, and a spatial oriented cell co-culture system via incorporating different cell-laden self-healing films, demonstrating their potential as building blocks in a wide range of biomedical applications where dynamic properties and biological functions are desired.

  16. Self-healing supramolecular bioelastomers with shape memory property as a multifunctional platform for biomedical applications via modular assembly.

    PubMed

    Wu, Yaobin; Wang, Ling; Zhao, Xin; Hou, Sen; Guo, Baolin; Ma, Peter X

    2016-10-01

    Mimicking native functional dynamics for traditional biomaterials such as thermoset elastomers is limited due to their lack of responsiveness to biological stimuli and difficulties to incorporate biofunctionalities. Furthermore, the mechanical fracture of traditional thermoset elastomers caused by irreversible covalent bond rupture would lead to their permanent loss of properties. To overcome these challenges, degradable self-healed supramolecular bioelastomers are designed by an elastic poly(glycerol sebacate) (PGS) backbone and multiple hydrogen-bonding ureido-pyrimidinone (UPy) grafts. These supramolecular elastic polymers exhibit efficient self-healing, rapid shape-memory abilities and highly tunable mechanical properties due to the dynamic supramolecular interactions, and perform a good biocompatibility in vitro and a mild host response in vivo. By combining modular approaches, these supramolecular bioelastomers have been further assembled into a multifunctional platform to expand their applications in different biomedical fields. These include a complex 3D scaffold with shape-memory capacity and anisotropic mechanical properties, a controllable drug delivery model via a layer-by-layer technique, a surface antibacterial composite by physical modification, and a spatial oriented cell co-culture system via incorporating different cell-laden self-healing films, demonstrating their potential as building blocks in a wide range of biomedical applications where dynamic properties and biological functions are desired. PMID:27424213

  17. Propagation and self-healing ability of a Bessel-Gaussian beam modulated by Bessel gratings

    NASA Astrophysics Data System (ADS)

    Qiao, Chunhong; Feng, Xiaoxing; Chu, Xiuxiang

    2016-04-01

    A new type of Bessel-like beam which can be generated by using Bessel gratings to modulate the amplitude and phase of a Bessel beam is proposed. In analogy to study a Bessel beam in free space, the intensity evolution and self-healing property of the Bessel-like beam have been studied. Meanwhile, based on the Fresnel diffraction integral, the propagation of the Bessel-like beam in free space has also been investigated. Results show that the Bessel-like beam and the Bessel-Gaussian-like beams have some special and interesting properties.

  18. Innovative Self-Healing Seals for Solid Oxide Fuel Cells (SOFC)

    SciTech Connect

    Raj Singh

    2012-06-30

    Solid oxide fuel cell (SOFC) technology is critical to several national initiatives. Solid State Energy Conversion Alliance (SECA) addresses the technology needs through its comprehensive programs on SOFC. A reliable and cost-effective seal that works at high temperatures is essential to the long-term performance of the SOFC for 40,000 hours at 800°C. Consequently, seals remain an area of highest priority for the SECA program and its industry teams. An innovative concept based on self-healing glasses was advanced and successfully demonstrated through seal tests for 3000 hours and 300 thermal cycles to minimize internal stresses under both steady state and thermal transients for making reliable seals for the SECA program. The self-healing concept requires glasses with low viscosity at the SOFC operating temperature of 800°C but this requirement may lead to excessive flow of the glass in areas forming the seal. To address this challenge, a modification to glass properties by addition of particulate fillers is pursued in the project. The underlying idea is that a non-reactive ceramic particulate filler is expected to form glass-ceramic composite and increase the seal viscosity thereby increasing the creep resistance of the glass-composite seals under load. The objectives of the program are to select appropriate filler materials for making glass-composite, fabricate glass-composites, measure thermal expansion behaviors, and determine stability of the glass-composites in air and fuel environments of a SOFC. Self-healing glass-YSZ composites are further developed and tested over a longer time periods under conditions typical of the SOFCs to validate the long-term stability up to 2000 hours. The new concepts of glass-composite seals, developed and nurtured in this program, are expected to be cost-effective as these are based on conventional processing approaches and use of the inexpensive materials.

  19. Electrosprayed Multi-Core Alginate Microcapsules as Novel Self-Healing Containers

    NASA Astrophysics Data System (ADS)

    Hia, Iee Lee; Pasbakhsh, Pooria; Chan, Eng-Seng; Chai, Siang-Piao

    2016-10-01

    Alginate microcapsules containing epoxy resin were developed through electrospraying method and embedded into epoxy matrix to produce a capsule-based self-healing composite system. These formaldehyde free alginate/epoxy microcapsules were characterized via light microscope, field emission scanning electron microscope, fourier transform infrared spectroscopy and thermogravimetric analysis. Results showed that epoxy resin was successfully encapsulated within alginate matrix to form porous (multi-core) microcapsules with pore size ranged from 5–100 μm. The microcapsules had an average size of 320 ± 20 μm with decomposition temperature at 220 °C. The loading capacity of these capsules was estimated to be 79%. Under in situ healing test, impact specimens showed healing efficiency as high as 86% and the ability to heal up to 3 times due to the multi-core capsule structure and the high impact energy test that triggered the released of epoxy especially in the second and third healings. TDCB specimens showed one-time healing only with the highest healing efficiency of 76%. The single healing event was attributed by the constant crack propagation rate of TDCB fracture test. For the first time, a cost effective, environmentally benign and sustainable capsule-based self-healing system with multiple healing capabilities and high healing performance was developed.

  20. Electrosprayed Multi-Core Alginate Microcapsules as Novel Self-Healing Containers

    PubMed Central

    Hia, Iee Lee; Pasbakhsh, Pooria; Chan, Eng-Seng; Chai, Siang-Piao

    2016-01-01

    Alginate microcapsules containing epoxy resin were developed through electrospraying method and embedded into epoxy matrix to produce a capsule-based self-healing composite system. These formaldehyde free alginate/epoxy microcapsules were characterized via light microscope, field emission scanning electron microscope, fourier transform infrared spectroscopy and thermogravimetric analysis. Results showed that epoxy resin was successfully encapsulated within alginate matrix to form porous (multi-core) microcapsules with pore size ranged from 5–100 μm. The microcapsules had an average size of 320 ± 20 μm with decomposition temperature at 220 °C. The loading capacity of these capsules was estimated to be 79%. Under in situ healing test, impact specimens showed healing efficiency as high as 86% and the ability to heal up to 3 times due to the multi-core capsule structure and the high impact energy test that triggered the released of epoxy especially in the second and third healings. TDCB specimens showed one-time healing only with the highest healing efficiency of 76%. The single healing event was attributed by the constant crack propagation rate of TDCB fracture test. For the first time, a cost effective, environmentally benign and sustainable capsule-based self-healing system with multiple healing capabilities and high healing performance was developed. PMID:27694922

  1. Self-healing of Bessel-like beams with longitudinally dependent cone angles

    NASA Astrophysics Data System (ADS)

    Litvin, I.; Burger, L.; Forbes, A.

    2015-10-01

    Bessel beams have been extensively studied, but to date have been created over a finite region inside the laboratory. Recently Bessel-like beams with longitudinally dependent cone angles have been introduced allowing for a potentially infinite quasi non-diffracting propagation region. Here we show that such beams can self-heal. Moreover, in contrast to Bessel beams where the self-healing distance is constant, here the self-healing distance is dependent on where the obstruction is placed in the field, with the distance increasing as the Bessel-like beam propagates farther. We outline the theoretical concept for this self-healing and confirm it experimentally.

  2. Networked Microgrids for Self-healing Power Systems

    SciTech Connect

    Wang, Zhaoyu; Chen, Bokan; Wang, Jianhui; Chen, Chen

    2015-06-17

    This paper proposes a transformative architecture for the normal operation and self-healing of networked microgrids (MGs). MGs can support and interchange electricity with each other in the proposed infrastructure. The networked MGs are connected by a physical common bus and a designed two-layer cyber communication network. The lower layer is within each MG where the energy management system (EMS) schedules the MG operation; the upper layer links a number of EMSs for global optimization and communication. In the normal operation mode, the objective is to schedule dispatchable distributed generators (DGs), energy storage systems (ESs) and controllable loads to minimize the operation costs and maximize the supply adequacy of each MG. When a generation deficiency or fault happens in a MG, the model switches to the self-healing mode and the local generation capacities of other MGs can be used to support the on-emergency portion of the system. A consensus algorithm is used to distribute portions of the desired power support to each individual MG in a decentralized way. The allocated portion corresponds to each MG’s local power exchange target which is used by its EMS to perform the optimal schedule. The resultant aggregated power output of networked MGs will be used to provide the requested power support. Test cases demonstrate the effectiveness of the proposed methodology.

  3. Encapsulation methods for photo-polymerisable self-healing formulations.

    PubMed

    Ballout, Wael; Périchaud, Alain; Caserta, Laura; Devassine, Mickael; Nistor, Cristina Lavinia; Iskakov, Rinat

    2016-06-01

    The aim of this work is to encapsulate a self-healing photo-polymerisable material for aerospace applications. To meet the technical requirements of space applications - low and high temperatures: -120 °C (dark side) to +250 °C (solar side); UV radiations: 200-400 nm; low pressure: 10(-4 )Pa - we chose trimethylolpropane triacrylate as healing agent. This monomer polymerises at 190 °C. To avoid its earlier thermal polymerisation, an inhibitor was added to the monomer/photo-initiator formulation. Moreover, among several microencapsulation techniques tested, we chose the sol-gel process to form silica microcapsules containing the self-healing formulation. These microcapsules were characterised by different analysis (scanning electron microscopy (SEM), thermo gravimetric analysis (TGA), Fourier transform infra-red spectroscopy (FTIR), etc.) and satisfied our requirements (size 1-30 μm, thermal stability >250 °C). After the microcapsules breakage, the generation of poly(TMPTA) film by radical photopolymerisation of the released TMPTA monomer was proved by disappearance of the IR peak at 1635 cm(-1) (assigned to TMPTA). The obtained film has a thermal stability above 300 °C. PMID:27283106

  4. Performance characteristics of a self-sealing/self-healing barrier

    SciTech Connect

    McGregor, R.G. |; Stegemann, J.A.

    1997-12-31

    Environment Canada and the Netherlands Energy Research Foundation are co-developers of a patented Self-Sealing/Self-Healing (SS/SH) Barrier system for containment of wastes which is licensed to Water Technology International Corporation. The SS/SH Barrier is intended for use as either a liner or cover for landfills, contaminated sites, secondary containment areas, etc., in the industrial, chemical, mining and municipal sectors, and also as a barrier to hydraulic flow for the transportation and construction industry. The SS/SH Barrier`s most significant feature is its capability for self-repair in the event of a breach. By contrast, conventional barrier systems, such as clay, geomembrane, or geosynthetic clay liners can not be repaired without laborious excavation and reconstruction. Laboratory investigations have shown that the SS/SH Barrier concept will function with a variety of reactive materials. Self-Sealing/Self-Healing Barriers are cost competitive and consistently exhibit hydraulic conductivities ranging from 10{sup -9} to 10{sup -13} m/s, which decrease with time. These measurements meet or exceed the recommended hydraulic conductivity required by EPA for clay liners (<1x10{sup -9} m/s) used in landfills and hazardous waste sites. Results of mineralogical examination of the seal, diffusion testing, hydraulic conductivity measurement, and durability testing, including wet/dry, freeze/thaw cycling and leachate compatibility are also presented.

  5. Processing and performance of self-healing materials

    NASA Astrophysics Data System (ADS)

    Tan, P. S.; Zhang, M. Q.; Bhattacharyya, D.

    2009-08-01

    Two self-healing methods were implemented into composite materials with self-healing capabilities, using hollow glass fibres (HGF) and microencapsulated epoxy resin with mercaptan as the hardener. For the HGF approach, two perpendicular layers of HGF were put into an E-glass/epoxy composite, and were filled with coloured epoxy resin and hardener. The HGF samples had a novel ball indentation test method done on them. The samples were analysed using micro-CT scanning, confocal microscopy and penetrant dye. Micro-CT and confocal microscopy produced limited success, but their viability was established. Penetrant dye images showed resin obstructing flow of dye through damage regions, suggesting infiltration of resin into cracks. Three-point bend tests showed that overall performance could be affected by the flaws arising from embedding HGF in the material. For the microcapsule approach, samples were prepared for novel double-torsion tests used to generate large cracks. The samples were compared with pure resin samples by analysing them using photoelastic imaging and scanning electron microscope (SEM) on crack surfaces. Photoelastic imaging established the consolidation of cracks while SEM showed a wide spread of microcapsules with their distribution being affected by gravity. Further double-torsion testing showed that healing recovered approximately 24% of material strength.

  6. Influence of Functionalization of Nanocontainers on Self-Healing Anticorrosive Coatings.

    PubMed

    Zheng, Zhaoliang; Schenderlein, Matthias; Huang, Xing; Brownbill, Nick J; Blanc, Frédéric; Shchukin, Dmitry

    2015-10-21

    Feedback coating based on pH-induced release of inhibitor from organosilyl-functionalized containers is considered as a compelling candidate to achieve smart self-healing corrosion protection. Four key factors that determine the overall coating performance include (1) the uptake and release capacity of containers, (2) prevention of the premature leakage, (3) compatibility of containers in coating matrix, and (4) cost and procedure simplicity consideration. The critical influence introduced by organosilyl-functionalization of containers is systematically demonstrated by investigating MCM-41 silica nanoparticles modified with ethylenediamine (en), en-4-oxobutanoic acid salt (en-COO(-)), and en-triacetate (en-(COO(-))3) with higher and lower organic contents. The properties of the modified silica nanoparticles as containers were mainly characterized by solid-state (13)C nuclear magnetic resonance, scanning and transmission electron microscopy, N2 sorption, thermogravimetric analysis, small-angle X-ray scattering, dynamic light scattering, and UV-vis spectroscopy. Finally, the self-healing ability and anticorrosive performances of hybrid coatings were examined through scanning vibrating electrode technique (SVET) and electrochemical impedance spectroscopy (EIS). We found that en-(COO(-))3-type functionalization with content of only 0.23 mmol/g performed the best as a candidate for establishing pH-induced release system because the resulting capped and loaded (C-L) functionalized silica nanocontainers (FSNs) exhibit high loading (26 wt %) and release (80%) capacities for inhibitor, prevention of premature leakage (less than 2%), good dispersibility in coating matrix, and cost effectiveness.

  7. Ant aggregations self-heal to compensate for the Ringelmann effect.

    PubMed

    Phonekeo, Sulisay; Dave, Tanvi; Kern, Matthew; Franklin, Scott V; Hu, David L

    2016-05-14

    Fire ants, Solenopsis invicta, link their bodies together to form structures such as rafts, bivouacs and bridges. Such structures are in danger of being damaged by natural disturbances such as passing water currents. In this combined experimental and theoretical study, we investigate the self-healing of ant assemblages. We press two ant aggregations together and measure the forces to pull them apart. As the group size increases, the contribution of each ant decreases. This phenomenon, known as the Ringelmann effect, or social loafing, has previously been shown for cattle and humans. In this study, we show that it is a challenge for ants as well. We rationalize this effect with an agent-based simulation which exhibits the Ringelmann effect of ants that periodically make and break links with each other, but grip with higher probability if the ants are stretched. Over time, ants compensate for the Ringelmann effect by building more links. We use a mathematical model to show that the rate of new links is proportional to the number of free ants in the cluster. The principles found here may inspire new directions in self-healing and active materials. PMID:27040612

  8. Abalone water-soluble matrix for self-healing biomineralization of tooth defects.

    PubMed

    Wen, Zhenliang; Chen, Jingdi; Wang, Hailiang; Zhong, Shengnan; Hu, Yimin; Wang, Zhili; Zhang, Qiqing

    2016-10-01

    Enamel cannot heal by itself if damaged. Hydroxyapatite (HAP) is main component of human enamel. Formation of enamel-like materials for healing enamel defects remains a challenge. In this paper, we successfully isolated the abalone water-soluble matrix (AWSM) with 1.53wt% the abalone water-soluble protein (AWSPro) and 2.04wt% the abalone water-soluble polysaccharide (AWSPs) from abandoned abalone shell, and self-healing biomineralization of tooth defects was successfully achieved in vitro. Based on X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), hot field emission scanning electron microscopy (HFESEM) and energy dispersive spectrometer (EDS) analysis, the results showed that the AWSM can efficiently induce remineralization of HAP. The enamel-like HAP was successfully achieved onto etched enamel's surface due to the presence of the AWSM. Moreover, the remineralized effect of eroded enamel was growing with the increase of the AWSM. This study provides a solution to the resource waste and environmental pollution caused by abandoned abalone shell, and we provides a new method for self-healing remineralization of enamel defects by AWSM and develops a novel dental material for potential clinical dentistry application.

  9. Abalone water-soluble matrix for self-healing biomineralization of tooth defects.

    PubMed

    Wen, Zhenliang; Chen, Jingdi; Wang, Hailiang; Zhong, Shengnan; Hu, Yimin; Wang, Zhili; Zhang, Qiqing

    2016-10-01

    Enamel cannot heal by itself if damaged. Hydroxyapatite (HAP) is main component of human enamel. Formation of enamel-like materials for healing enamel defects remains a challenge. In this paper, we successfully isolated the abalone water-soluble matrix (AWSM) with 1.53wt% the abalone water-soluble protein (AWSPro) and 2.04wt% the abalone water-soluble polysaccharide (AWSPs) from abandoned abalone shell, and self-healing biomineralization of tooth defects was successfully achieved in vitro. Based on X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), hot field emission scanning electron microscopy (HFESEM) and energy dispersive spectrometer (EDS) analysis, the results showed that the AWSM can efficiently induce remineralization of HAP. The enamel-like HAP was successfully achieved onto etched enamel's surface due to the presence of the AWSM. Moreover, the remineralized effect of eroded enamel was growing with the increase of the AWSM. This study provides a solution to the resource waste and environmental pollution caused by abandoned abalone shell, and we provides a new method for self-healing remineralization of enamel defects by AWSM and develops a novel dental material for potential clinical dentistry application. PMID:27287112

  10. "Smart" drug loaded nanoparticle delivery from a self-healing hydrogel enabled by dynamic magnesium-biopolymer chemistry.

    PubMed

    Shi, Liyang; Han, Yuanyuan; Hilborn, Jöns; Ossipov, Dmitri

    2016-09-25

    We report a strategy to generate a self-healing and pH responsive hydrogel network between drug-loaded nanoparticles and natural polysaccharides via magnesium-bisphosphonate ligand interactions. The injectable drug depot disassembles in a tumor-specific environment, providing localized uptake of the nanoparticles, which is highly appreciated in drug delivery applications and manufacturing of drug-loaded biomaterials using a syringe-based deposition technique. PMID:27550535

  11. Microfluidic encapsulation for self-healing material and investigation of its impacts on composite performance

    NASA Astrophysics Data System (ADS)

    Lemmens, Ryan J.

    Encapsulation is a key enabling technology of self-healing materials for which incorporation of reactive materials into a composite, without loss of functionality, is required for damage repair. The functionalized particles resulting from such processes must be readily incorporable into a composite and have minimal detrimental impact on its undamaged properties. At the same time, their morphology must preferentially promote the release of their content during a damage event. However, there is still a need for new techniques capable of fine tuning particle properties for the controlled design of composite performance. To introduce superior processing control, two microfluidics based encapsulation processes have been developed, one each for the individual components of a two-part chemical healing system, namely dicyclopentadiene and Grubb's catalyst. These processes have enabled significantly enhanced performance of self-healing epoxy composites by introducing unprecedented control over particle morphology. The microfluidics based encapsulation platform is first demonstrated by emulsification, using droplet microfluidics, and subsequent encapsulation of dicyclopentadiene. The reported approach allows for facile control of mean microcapsule diameter thru variation of fluid flow rates. The microcapsules exhibit coefficients of variation (CV) of diameter in the range 1-3 (i.e. monodisperse is typically defined as CV smaller than 5), an order of magnitude reduction when compared with conventional batch emulsification methods whose typical CV is 20-40. This control over microcapsule uniformity has led to significant improvement in self-healing composite performance as exemplified by ˜25% higher undamaged fracture toughness. A microfluidic solution spinning process is then developed to encapsulate Grubb's catalyst, the most expensive component of this particular material system, in a novel fibrous morphology. The continuous, on-chip fiber production allows for

  12. Self-healing properties of nanocrystalline materials: a first-principles analysis of the role of grain boundaries.

    PubMed

    Xu, Jian; Liu, Jian-Bo; Li, Shun-Ning; Liu, Bai-Xin; Jiang, Yong

    2016-07-21

    Understanding the self-healing mechanisms of defects in nanocrystalline materials is of particular importance for developing structural materials that can support the extended lifetime of components under extremely hostile conditions in nuclear reactors. Since grain boundaries are prevalent in nanocrystalline materials, they must affect, to some extent, the overall self-healing properties and the resultant mechanical responses. In the present work, first principles calculations are carried out to investigate the energetic landscape of point defects (i.e. self-interstitials, He-interstitials, and vacancies) induced by the irradiation damage and the kinetics of the self-healing process in the vicinity of grain boundaries (GBs) in copper, focusing on six symmetric tilt grain boundaries that vary in their energies. Our results indicate that the interaction of vacancies with the self-interstitial- and He-interstitial-loaded GBs is very sensitive to the GB character. Low-energy GBs are generally accompanied by a higher propensity for self-healing behavior, in which the inter-granular interstitials and intra-granular vacancies recombine with each other. The recombination process is proved to be regulated by two mechanisms: the interstitial emission mechanism and the vacancy mediated mechanism. For low-energy GBs, the former mechanism demonstrates its efficiency in describing the atomic motion, while for the high-energy ones, the latter turns out to be superior. With the aid of these mechanisms, we conclude that low-energy GBs are comparatively more radiation-resistant than the high-energy counterparts, which may shed light on the rational design of high-performance structural materials based on nanocrystalline alloys. PMID:27326789

  13. Building Self-Healing Alloy Architecture for Stable Sodium-Ion Battery Anodes: A Case Study of Tin Anode Materials.

    PubMed

    Mao, Jianfeng; Fan, Xiulin; Luo, Chao; Wang, Chunsheng

    2016-03-23

    The rational design of anode materials is a challenge in developing sodium ion batteries. Alloy anodes provide high gravimetric and volumetric capacities but suffer the short cycle life as a result of the continuous and accumulated pulverization, resulting from a large volume change during the cycling process. Herein, using pure Sn, an irreversible conversion reaction combined with an alloy reaction (SnO), and a reversible conversion reaction combined with an alloy reaction (Sn4P3) as samples, we demonstrate that the pulverization and aggregation of the alloy anode can be partially recovered and the accumulation of pulverization and aggregation during charge/discharge cycles can be terminated using a reversible conversion reaction combined with an alloy reaction. The cycling stability of three Sn-based anodes increases in order of Sn4P3 > SnO > Sn. The enhancement in Sn4P3 can be attributed to a reversible reaction of Sn4P3 + 9Na ↔ 4Sn + 3Na3P, which repairs the cracks, damage, and aggregation of Sn particles that occurred in the alloy process of 4Sn + 15Na ↔ Na15Sn4 during cycling and, hence, terminates the pulverization. The repair mechanism looks like the self-healing feature in nature, where the damage can be healed by itself. Therefore, the suggested mechanism can be called self-healing, while the repaired anode can be termed as the self-healing anode. The use of self-healing strategies to build an electrode architecture is new and highly desirable because it can increase the cycle life and provide a general approach toward stable electrode materials. PMID:26937998

  14. Self-healing properties of nanocrystalline materials: a first-principles analysis of the role of grain boundaries.

    PubMed

    Xu, Jian; Liu, Jian-Bo; Li, Shun-Ning; Liu, Bai-Xin; Jiang, Yong

    2016-07-21

    Understanding the self-healing mechanisms of defects in nanocrystalline materials is of particular importance for developing structural materials that can support the extended lifetime of components under extremely hostile conditions in nuclear reactors. Since grain boundaries are prevalent in nanocrystalline materials, they must affect, to some extent, the overall self-healing properties and the resultant mechanical responses. In the present work, first principles calculations are carried out to investigate the energetic landscape of point defects (i.e. self-interstitials, He-interstitials, and vacancies) induced by the irradiation damage and the kinetics of the self-healing process in the vicinity of grain boundaries (GBs) in copper, focusing on six symmetric tilt grain boundaries that vary in their energies. Our results indicate that the interaction of vacancies with the self-interstitial- and He-interstitial-loaded GBs is very sensitive to the GB character. Low-energy GBs are generally accompanied by a higher propensity for self-healing behavior, in which the inter-granular interstitials and intra-granular vacancies recombine with each other. The recombination process is proved to be regulated by two mechanisms: the interstitial emission mechanism and the vacancy mediated mechanism. For low-energy GBs, the former mechanism demonstrates its efficiency in describing the atomic motion, while for the high-energy ones, the latter turns out to be superior. With the aid of these mechanisms, we conclude that low-energy GBs are comparatively more radiation-resistant than the high-energy counterparts, which may shed light on the rational design of high-performance structural materials based on nanocrystalline alloys.

  15. Building Self-Healing Alloy Architecture for Stable Sodium-Ion Battery Anodes: A Case Study of Tin Anode Materials.

    PubMed

    Mao, Jianfeng; Fan, Xiulin; Luo, Chao; Wang, Chunsheng

    2016-03-23

    The rational design of anode materials is a challenge in developing sodium ion batteries. Alloy anodes provide high gravimetric and volumetric capacities but suffer the short cycle life as a result of the continuous and accumulated pulverization, resulting from a large volume change during the cycling process. Herein, using pure Sn, an irreversible conversion reaction combined with an alloy reaction (SnO), and a reversible conversion reaction combined with an alloy reaction (Sn4P3) as samples, we demonstrate that the pulverization and aggregation of the alloy anode can be partially recovered and the accumulation of pulverization and aggregation during charge/discharge cycles can be terminated using a reversible conversion reaction combined with an alloy reaction. The cycling stability of three Sn-based anodes increases in order of Sn4P3 > SnO > Sn. The enhancement in Sn4P3 can be attributed to a reversible reaction of Sn4P3 + 9Na ↔ 4Sn + 3Na3P, which repairs the cracks, damage, and aggregation of Sn particles that occurred in the alloy process of 4Sn + 15Na ↔ Na15Sn4 during cycling and, hence, terminates the pulverization. The repair mechanism looks like the self-healing feature in nature, where the damage can be healed by itself. Therefore, the suggested mechanism can be called self-healing, while the repaired anode can be termed as the self-healing anode. The use of self-healing strategies to build an electrode architecture is new and highly desirable because it can increase the cycle life and provide a general approach toward stable electrode materials.

  16. Durable and self-healing superamphiphobic coatings repellent even to hot liquids.

    PubMed

    Li, Bucheng; Zhang, Junping

    2016-02-14

    Durable and self-healing superamphiphobic coatings with high repellency to both cool and hot liquids are successfully prepared on various substrates by the combination of rodlike palygorskite and organosilanes via spray-coating. The coatings feature high mechanical, environmental and chemical durability, and are self-healing.

  17. Development of Micro and Nanostructured Materials for Interfacial Self-Healing

    ERIC Educational Resources Information Center

    Blaiszik, Benjamin James

    2009-01-01

    Damage in polymeric coatings, adhesives, microelectronic components, and composites spans many length scales. For small scale damage, autonomic self-healing can repair multiple damage modes without manual intervention. In autonomic self-healing materials, a healing response is triggered by damage to the material. Size scale considerations, such as…

  18. A self-healing hydrogel formation strategy via exploiting endothermic interactions between polyelectrolytes.

    PubMed

    Ren, Ying; Lou, Ruyun; Liu, Xiaocen; Gao, Meng; Zheng, Huizhen; Yang, Ting; Xie, Hongguo; Yu, Weiting; Ma, Xiaojun

    2016-05-01

    We report a strategy to synthesize self-healing hydrogels via exploiting endothermic interactions between polyelectrolytes. Natural polysaccharides and their derivatives were used to form reversible polyelectrolyte complexes by selecting appropriately charged chemical groups and counterions. This simple and effective method to fabricate self-healing hydrogels will find applications in diverse fields such as surface coating and 3D printing. PMID:27078585

  19. Durable and self-healing superamphiphobic coatings repellent even to hot liquids.

    PubMed

    Li, Bucheng; Zhang, Junping

    2016-02-14

    Durable and self-healing superamphiphobic coatings with high repellency to both cool and hot liquids are successfully prepared on various substrates by the combination of rodlike palygorskite and organosilanes via spray-coating. The coatings feature high mechanical, environmental and chemical durability, and are self-healing. PMID:26758697

  20. Congenital self-healing reticulohistiocytosis: an underreported entity.

    PubMed

    Kassardjian, Michael; Patel, Mayha; Shitabata, Paul; Horowitz, David

    2016-04-01

    Langerhans cell histiocytosis (LCH), also known as histiocytosis X, is a group of rare disorders characterized by the continuous replication of a particular white blood cell called Langerhans cells. These cells are derived from the bone marrow and are found in the epidermis, playing a large role in immune surveillance and the elimination of foreign substances from the body. Additionally, Langerhans cells are capable of migrating from the skin to lymph nodes, and in LCH, these cells begin to congregate on the bone, particularly in the head and neck region, causing a multitude of problems. Langerhans cell histiocytosis is classified into 4 variants: congenital self-healing reticulohistiocytosis (CSHR)(also known as Hashimoto-Pritzker disease), Letterer-Siwe disease, Hand-Schüller-Christian disease, and eosinophilic granuloma. Despite various clinical presentations and severity, all subtypes are pathologically caused by the proliferation of the Langerhans cell. PMID:27163913

  1. Self-healing patterns in ferromagnetic-superconducting hybrids

    NASA Astrophysics Data System (ADS)

    Vlasko-Vlasov, V. K.; Palacious, E.; Rosenmann, D.; Pearson, J.; Jia, Y.; Wang, Y. L.; Welp, U.; Kwok, W.-K.

    2015-03-01

    We study magnetic flux dynamic effects in a superconducting (SC) bridge with thin soft magnetic stripes placed either on top or under the bridge. Voltage-current (VI) measurements reveal that the edges of magnetic stripes oriented transvers or along the bridge introduce channels or barriers for vortex motion, resulting in the decrease or increase of the critical current, respectively. We propose a self-healing mechanism for the hybrid with longitudinal stripes whereby the magnetic pinning strength increases with current. The self-field of the current polarizes the magnetic stripes across their length, which enhances the stray fields at their long edges and creates a dynamic vortex pinning landscape to impede vortex flow. We show a qualitative confirmation of the proposed mechanism which offers new strategies to engineer adaptive pinning topologies in SC-ferromagnetic hybrids.

  2. Pressurized vascular systems for self-healing materials

    PubMed Central

    Hamilton, A. R.; Sottos, N. R.; White, S. R.

    2012-01-01

    An emerging strategy for creating self-healing materials relies on embedded vascular networks of microchannels to transport reactive fluids to regions of damage. Here we investigate the use of active pumping for the pressurized delivery of a two-part healing system, allowing a small vascular system to deliver large volumes of healing agent. Different pumping strategies are explored to improve the mixing and subsequent polymerization of healing agents in the damage zone. Significant improvements in the number of healing cycles and in the overall healing efficiency are achieved compared with prior passive schemes that use only capillary forces for the delivery of healing agents. At the same time, the volume of the vascular system required to achieve this superior healing performance is significantly reduced. In the best case, nearly full recovery of fracture toughness is attained throughout 15 cycles of damage and healing, with a vascular network constituting just 0.1 vol% of the specimen. PMID:21957119

  3. Solid state self-healing system: Effects of using PDGEBA, PVC and PVA as linear healing agents

    NASA Astrophysics Data System (ADS)

    Muhamad, Noor Nabilah; Jamil, Mohd. Suzeren Md.; Abdullah, Shahrum

    2014-09-01

    The solid state self-healing system was obtained by employing a thermosetting epoxy resin, into which a thermoplastic is dissolved. In this study, the effect of healing efficiency was investigated by using different thermoplastic polymers which are poly(bisphenol-A-co-epichlorohydrin), polyvinyl chloride and polyvinyl alcohol as healing agents. Healing was achieved by heating the fractured resins to a specific temperature i.e. above their glass transition temperature (Tg) which obtained from dynamic mechanical analysis (DMA) to mobilize the polymeric chains of the healing agent. The curing reaction in the epoxy resins were characterized by means of Fourier transform infrared spectroscopy (FTIR). Izod impact test was been performed to demonstrate self-healing of the different specimens. Under test, it was found that healable resin with PDGEBA has highest healing efficiency followed by PVC and PVA, with 63%, 35% and 18% of average percentage healing efficiencies respectively. These results are due to the different solubility parameters of the thermoset/network and thermoplastic polymer which led to the phase separation. Morphological studies prove the fracture-healing process and morphological properties of the resins.

  4. Piezoelectric and mechanical properties of fatigue resistant, self-healing PZT-ionomer composites

    NASA Astrophysics Data System (ADS)

    James, N. K.; Lafont, U.; van der Zwaag, S.; Groen, W. A.

    2014-05-01

    Piezoelectric ceramic-polymer composites with 0-3 connectivity were fabricated using lead zirconium titanate (PZT) powder dispersed in an ionomer (Zn ionomer) and its reference ethylene methacrylic acid copolymer (EMAA) polymer matrix. The PZT-Zn ionomer and PZT-EMAA composites were prepared by melt extrusion followed by hot pressing. The effects of poling conditions such as temperature, time and electric field on the piezoelectric properties of the composites were investigated. The experimentally observed piezoelectric charge coefficient and dielectric constant of the composites were compared with theoretical models. The results show that PZT-Zn ionomer composites have better piezoelectric properties compared to PZT-EMAA composites. The static and fatigue properties of the composites were investigated. The PZT-Zn ionomer composites were found to have excellent fatigue resistance even at strain levels of 4%. Due to the self-healing capabilities of the ionomer matrix, the loss of piezoelectric properties after high strain tensile cyclic loading could be partially recovered by thermal healing.

  5. Effect of using miscible and immiscible healing agent on solid state self-healing system

    NASA Astrophysics Data System (ADS)

    Makenan, Siti Mastura; Jamil, Mohd Suzeren Md.

    2014-09-01

    The aim of this study is to identify the effect of using various healing agent which are miscible; poly(bisphenol-A-co-epichlorohydrin), and immiscible; poly(ethylene-co-acetate) and poly(ethylene-co-acrylic acid), on self-healing resin system. The specimens were analysed by Fourier-transform Infrared Spectrometer (FTIR), Dynamic Mechanical Thermal Analysis (DMTA), and izod test. Optical image of the sample morphology was observed using optical microscope. Healing efficiencies (HE) were evaluated using izod test. The concept of healing recovery was proved based on the use of miscible and immiscible healing agent. From the results, it can be concluded that the healable resin with miscible healing agent has the highest HE within the third healing cycle.

  6. Repetitive Biomimetic Self-healing of Ca(2+)-Induced Nanocomposite Protein Hydrogels.

    PubMed

    Chen, Jun; Dong, Qiuchen; Ma, Xiaoyu; Fan, Tai-Hsi; Lei, Yu

    2016-01-01

    Self-healing is a capacity observed in most biological systems in which the healing processes are autonomously triggered after the damage. Inspired by this natural behavior, researchers believed that a synthetic material possessing similar self-recovery capability could also be developed. Albeit various intrinsic self-healing systems have been developed over the past few decades, restriction on the biocompatibility due to the required synthetic conditions under extreme pH and with poisonous cross-linker significantly limits their application in biomedical field. In this study, a highly biocompatible nanocomposite protein hydrogel with excellent biomimetic self-healing property is presented. The self-healing protein gel is made by inducing calcium ions into the mixture of heat-induced BSA nano-aggregates and pristine BSA molecules at room temperature and under physiological pH due to the ion-mediated protein-protein association and the bridging effect of divalent Ca(2+) ions. The as-prepared protein hydrogel shows excellent repetitive self-healing properties without using any external stimuli at ambient condition. Such outstanding self-recovery performance was quantitatively evaluated/validated by both dynamic and oscillatory rheological analysis. Moreover, with the presence of calcium ions, the self-healing behavior can be significantly facilitated/enhanced. Finally, the superior biocompatibility demonstrated by in vitro cytotoxicity analysis suggests that it is a promising self-healing material well-suited for biomedical applications. PMID:27545280

  7. Repetitive Biomimetic Self-healing of Ca2+-Induced Nanocomposite Protein Hydrogels

    NASA Astrophysics Data System (ADS)

    Chen, Jun; Dong, Qiuchen; Ma, Xiaoyu; Fan, Tai-Hsi; Lei, Yu

    2016-08-01

    Self-healing is a capacity observed in most biological systems in which the healing processes are autonomously triggered after the damage. Inspired by this natural behavior, researchers believed that a synthetic material possessing similar self-recovery capability could also be developed. Albeit various intrinsic self-healing systems have been developed over the past few decades, restriction on the biocompatibility due to the required synthetic conditions under extreme pH and with poisonous cross-linker significantly limits their application in biomedical field. In this study, a highly biocompatible nanocomposite protein hydrogel with excellent biomimetic self-healing property is presented. The self-healing protein gel is made by inducing calcium ions into the mixture of heat-induced BSA nano-aggregates and pristine BSA molecules at room temperature and under physiological pH due to the ion-mediated protein-protein association and the bridging effect of divalent Ca2+ ions. The as-prepared protein hydrogel shows excellent repetitive self-healing properties without using any external stimuli at ambient condition. Such outstanding self-recovery performance was quantitatively evaluated/validated by both dynamic and oscillatory rheological analysis. Moreover, with the presence of calcium ions, the self-healing behavior can be significantly facilitated/enhanced. Finally, the superior biocompatibility demonstrated by in vitro cytotoxicity analysis suggests that it is a promising self-healing material well-suited for biomedical applications.

  8. Repetitive Biomimetic Self-healing of Ca2+-Induced Nanocomposite Protein Hydrogels

    PubMed Central

    Chen, Jun; Dong, Qiuchen; Ma, Xiaoyu; Fan, Tai-Hsi; Lei, Yu

    2016-01-01

    Self-healing is a capacity observed in most biological systems in which the healing processes are autonomously triggered after the damage. Inspired by this natural behavior, researchers believed that a synthetic material possessing similar self-recovery capability could also be developed. Albeit various intrinsic self-healing systems have been developed over the past few decades, restriction on the biocompatibility due to the required synthetic conditions under extreme pH and with poisonous cross-linker significantly limits their application in biomedical field. In this study, a highly biocompatible nanocomposite protein hydrogel with excellent biomimetic self-healing property is presented. The self-healing protein gel is made by inducing calcium ions into the mixture of heat-induced BSA nano-aggregates and pristine BSA molecules at room temperature and under physiological pH due to the ion-mediated protein-protein association and the bridging effect of divalent Ca2+ ions. The as-prepared protein hydrogel shows excellent repetitive self-healing properties without using any external stimuli at ambient condition. Such outstanding self-recovery performance was quantitatively evaluated/validated by both dynamic and oscillatory rheological analysis. Moreover, with the presence of calcium ions, the self-healing behavior can be significantly facilitated/enhanced. Finally, the superior biocompatibility demonstrated by in vitro cytotoxicity analysis suggests that it is a promising self-healing material well-suited for biomedical applications. PMID:27545280

  9. Adhesion and Long-Term Barrier Restoration of Intrinsic Self-Healing Hybrid Sol-Gel Coatings.

    PubMed

    Abdolah Zadeh, Mina; van der Zwaag, Sybrand; Garcia, Santiago J

    2016-02-17

    Self-healing polymeric coatings aiming at smart and on-demand protection of metallic substrates have lately attracted considerable attention. In the present paper, the potential application of a dual network hybrid sol-gel polymer containing reversible tetrasulfide groups as a protective coating for the AA2024-T3 substrate is presented. Depending on the constituent ratio, the developed polymer exhibited a hydrophobic surface, high adhesion strength, and an effective long-term corrosion protection in 0.5 M NaCl solution. Upon thermal treatment, the healable hybrid sol-gel coating demonstrated full restoration of the barrier properties as well as recovery of the coating adhesion and surface properties (e.g., hydrophobicity and surface topology) necessary for lifetime extension of corrosion protective coatings. Excellent long-term barrier restoration of the coating was only obtained if the scratch width was less than the coating thickness. PMID:26780101

  10. A key management scheme for tiered wireless sensor network with self-healing capability

    NASA Astrophysics Data System (ADS)

    Wang, Maoyu; Tang, Helen; Yu, F. R.

    2013-05-01

    This paper presents a novel key management scheme for a tiered self-healing wireless sensor network. A tiered wireless sensor network with self-healing features draws extensive attention because of its scalability, robustness and reliability. A tiered key management scheme to support the cluster membership and the self-healing features is proposed with emphasis on the control of a node's participation and re-keying when joining a new cluster. The security and overhead analysis demonstrates the proposed scheme is effective and efficient with respect to communication, computation, and memory overhead for operation in a hostile environment.

  11. High Temperature Lightweight Self-Healing Ceramic Composites for Aircraft Engine Applications

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.; Singh, Mrityunjay; Bhatt, Ramakrishna T.

    2014-01-01

    The present research effort was undertaken to develop a new generation of SiC fiber- reinforced engineered matrix composites (EMCs) with sufficient high temperature plasticity to reduce crack propagation and self-healing capabilities to fill surface-connected cracks to prevent the oxygen ingress to the fibers. A matrix engineered with these capabilities is expected to increase the load bearing capabilities of SiCSiC CMCs at high temperatures. Several matrix compositions were designed to match the coefficient of thermal expansion (CTE) of the SiC fibers using a rule of mixture (ROM) approach. The CTE values of these matrices were determined and it was demonstrated that they were generally in good agreement with that of monolithic SiC between room temperature and 1525 K. The parameters to hot press the powders were optimized, and specimens were fabricated for determining bend strength, CTE, oxidation and microstructural characteristics of the engineered matrices. The oxidation tests revealed that some of the matrices exhibited catastrophic oxidation, and therefore, these were eliminated from further consideration. Two promising compositions were down selected based on these results for further development. Four-point bend tests were conducted on these two promising matrices between room temperature and 1698 K. Although theses matrices were brittle and failed at low stresses at room temperature, they exhibited high temperature ductility and higher stresses at the higher temperatures. The effects of different additives on the self-healing capabilities of these matrices were investigated. The results of preliminary studies conducted to slurry and melt infiltration trials with CrSi2 are described.

  12. Diagnostic of the self-healing of metallized polypropylene film by modeling of the broadening emission lines of aluminum emitted by plasma discharge

    SciTech Connect

    Tortai, J.-H.; Bonifaci, N.; Denat, A.; Trassy, C.

    2005-03-01

    Metallized-film capacitors have the property, even under high continuous voltage, to self-heal i.e., to clear a defect in the dielectric. The self-healing process is a consequence of a transient arc discharge. It has been previously shown that during the discharge, due to Joule effect, the metal is vaporized until the arc extinguishes. The discharge duration has been found to be inversely proportional to the mechanical pressure applied on the layers of metallized films making up a capacitor. The aim of this study is to understand the physical processes involved in this spontaneous extinction of the arc discharge. Emission spectroscopy has been used to provide information about the physical properties (temperatures, electronic and neutral particles densities, etc.) of the plasma induces by a self-healing. An analysis, based on the broadenings and shifts of Al atomic lines, of the experimental light spectra obtained has shown that the self-healing process leads to the generation, from the vaporized metal, of a high-density and relatively weakly ionized aluminum plasma. The plasma density increases with the pressure applied on the film layers and, consequently, the density power needed to extend the plasma zone increases as well and the arc discharge goes out faster as experimentally observed.

  13. Using feedback control to actively regulate the healing rate of a self-healing process subjected to low cycle dynamic stress

    NASA Astrophysics Data System (ADS)

    Kuponu, O. S.; Kadirkamanathan, V.; Bhattacharya, B.; Pope, S. A.

    2016-05-01

    Intrinsic and extrinsic self-healing approaches through which materials can be healed generally suffer from several problems. One key problem is that to ensure effective healing and to minimise the propagation of a fault, the healing rate needs to be matched to the damage rate. This requirement is usually not met with passive approaches. An alternative to passive healing is active self-healing, whereby the healing mechanism and in particular the healing rate, is controlled in the face of uncertainty and varying conditions. Active self-healing takes advantage of sensing and added external energy to achieve a desired healing rate. To demonstrate active self-healing, an electrochemical material based on the principles of piezoelectricity and electrolysis is modelled and adaptive feedback control is implemented. The adaptive feedback control compensates for the insufficient piezo-induced voltage and guarantees a response that meets the desired healing rate. Importantly, fault propagation can be eliminated or minimised by attaining a match between the healing and damage rate quicker than can be achieved with the equivalent passive system. The desired healing rate is a function of the fault propagation and is assumed known in this paper, but can be estimated in practice through established prognostic techniques.

  14. Autonomous stimulus triggered self-healing in smart structural composites

    NASA Astrophysics Data System (ADS)

    Norris, C. J.; White, J. A. P.; McCombe, G.; Chatterjee, P.; Bond, I. P.; Trask, R. S.

    2012-09-01

    Inspired by the ability of biological systems to sense and autonomously heal damage, this research has successfully demonstrated the first autonomous, stimulus triggered, self-healing system in a structural composite material. Both the sensing and healing mechanisms are reliant on microvascular channels incorporated within a laminated composite material. For the triggering mechanism, a single air filled vessel was pressurized, sealed and monitored. Upon drop weight impact (10 J), delamination and microcrack connectivity between the pressurized vessel and those open to ambient led to a pressure loss which, with the use of a suitable sensor, triggered a pump to deliver a healing agent to the damage zone. Using this autonomous healing approach, near full recovery of post-impact compression strength was achieved (94% on average). A simplified alternative system with healing agent continuously flowing through the vessels, akin to blood flow, was found to offer 100% recovery of the material’s virgin strength. Optical microscopy and ultrasonic C-scanning provided further evidence of large-scale infusion of matrix damage with the healing agent. The successful implementation of this bioinspired technology could substantially enhance the integrity and reliability of aerospace structures, whilst offering benefits through improved performance/weight ratios and extended lifetimes.

  15. Multiscale Modeling of Biomimetic Self-Healing Materials

    NASA Astrophysics Data System (ADS)

    Kolmakov, German; Scarbrough, Amy; Gnegy, Chet; Salib, Isaac; Matyjaszewski, Krzysztof; Balazs, Anna

    2011-03-01

    We use a hybrid computational approach to examine the self-healing behavior of polymeric materials composed of soft nanogel particles crosslinked by a network of both stable and labile bonds. The latter are highly reactive and therefore, can break and readily reform. To capture the multiscale structure of the material, we take advantage of the multi-level Hierarchical Bell Model (mHBM) where the labile crosslinks are organized into M levels of interconnected elements, each of them represents a number of bonds that lie in parallel and is described by a single-level HBM. We vary the number of hierarchical levels M and the number of labile bonds in each element to determine optimal conditions for improving strength and toughness of the material. We also compare the properties of the multiscale material with those for the gel, in which only single-level interconnections are presented. This study takes its inspiration from biological systems that show remarkable resilience in response to mechanical deformation.

  16. A computational model for the flow of resin in self-healing composites

    NASA Astrophysics Data System (ADS)

    Hall, J.; Qamar, I. P. S.; Rendall, T. C. S.; Trask, R. S.

    2015-03-01

    To explore the flow characteristics of healing agent leaving a vascular network and infusing a damage site within a fibre reinforced polymer composite, a numerical model of healing agent flow from an orifice has been developed using smoothed particle hydrodynamics. As an initial validation the discharge coefficient for low Reynolds number flow from a cylindrical tank is calculated numerically, using two different viscosity formulations, and compared to existing experimental data. Results of this comparison are very favourable; the model is able to reproduce experimental results for the discharge coefficient in the high Reynolds number limit, together with the power-law behaviour for low Reynolds numbers. Results are also presented for a representative delamination geometry showing healing fluid behaviour and fraction filled inside the delamination for a variety of fluid viscosities. This work provides the foundations for the vascular self-healing community in calculating not only the flow rate through the network, but also, by simulating a representative damage site, the final location of the healing fluid within the damage site in order to assess the improvement in local and global mechanical properties and thus healing efficiency.

  17. Robust, superamphiphobic fabric with multiple self-healing ability against both physical and chemical damages.

    PubMed

    Wang, Hongxia; Zhou, Hua; Gestos, Adrian; Fang, Jian; Lin, Tong

    2013-10-23

    Superamphiphobic coatings with excellent repellency to low surface tension liquids and multiple self-healing abilities are very useful for practical applications, but remain challenging to realize. Previous papers on self-healing superamphiphobic coatings have demonstrated limited liquid repellency with single self-healing ability against either physical or chemical damage. Herein, we describe a superamphiphobic fabric that has remarkable multi-self-healing ability against both physical and chemical damages. The superamphiphobicity was prepared by a two-step surface coating technique. Fabric after coating treatment showed exceptional liquid-repellency to low surface tension liquids including ethanol. The fabric coating was also durable to withstand 200 cycles of laundries and 5000 cycles of Martindale abrasion without apparently changing the superamphiphobicity. This highly robust, superamphiphobic fabric may find applications for the development of "smart" functional textiles for various applications.

  18. Self-healing of Hermite-Gauss and Ince-Gauss beams

    NASA Astrophysics Data System (ADS)

    Aguirre-Olivas, Dilia; Mellado-Villaseñor, Gabriel; Arrizón, Victor; Chávez-Cerda, Sabino

    2015-08-01

    We analyze and demonstrate, numerically and experimentally, the self-healing effect in scaled propagation invariant beams, subject to opaque obstructions. The effect is quantitatively evaluated employing the Root Mean Square deviation and the similarity function.

  19. Robust, superamphiphobic fabric with multiple self-healing ability against both physical and chemical damages.

    PubMed

    Wang, Hongxia; Zhou, Hua; Gestos, Adrian; Fang, Jian; Lin, Tong

    2013-10-23

    Superamphiphobic coatings with excellent repellency to low surface tension liquids and multiple self-healing abilities are very useful for practical applications, but remain challenging to realize. Previous papers on self-healing superamphiphobic coatings have demonstrated limited liquid repellency with single self-healing ability against either physical or chemical damage. Herein, we describe a superamphiphobic fabric that has remarkable multi-self-healing ability against both physical and chemical damages. The superamphiphobicity was prepared by a two-step surface coating technique. Fabric after coating treatment showed exceptional liquid-repellency to low surface tension liquids including ethanol. The fabric coating was also durable to withstand 200 cycles of laundries and 5000 cycles of Martindale abrasion without apparently changing the superamphiphobicity. This highly robust, superamphiphobic fabric may find applications for the development of "smart" functional textiles for various applications. PMID:24073919

  20. An Injectable, Self-Healing Hydrogel to Repair the Central Nervous System.

    PubMed

    Tseng, Ting-Chen; Tao, Lei; Hsieh, Fu-Yu; Wei, Yen; Chiu, Ing-Ming; Hsu, Shan-hui

    2015-06-17

    An injectable, self-healing hydrogel (≈1.5 kPa) is developed for healing nerve-system deficits. Neurosphere-like progenitors proliferate in the hydrogel and differentiate into neuron-like cells. In the zebrafish injury model, the central nervous system function is partially rescued by injection of the hydrogel and significantly rescued by injection of the neurosphere-laden hydrogel. The self-healing hydrogel may thus potentially repair the central nervous system.

  1. Self-Healing Textile: Enzyme Encapsulated Layer-by-Layer Structural Proteins.

    PubMed

    Gaddes, David; Jung, Huihun; Pena-Francesch, Abdon; Dion, Genevieve; Tadigadapa, Srinivas; Dressick, Walter J; Demirel, Melik C

    2016-08-10

    Self-healing materials, which enable an autonomous repair response to damage, are highly desirable for the long-term reliability of woven or nonwoven textiles. Polyelectrolyte layer-by-layer (LbL) films are of considerable interest as self-healing coatings due to the mobility of the components comprising the film. In this work mechanically stable self-healing films were fabricated through construction of a polyelectrolyte LbL film containing squid ring teeth (SRT) proteins. SRTs are structural proteins with unique self-healing properties and high elastic modulus in both dry and wet conditions (>2 GPa) due to their semicrystalline architecture. We demonstrate LbL construction of multilayers containing native and recombinant SRT proteins capable of self-healing defects. Additionally, we show these films are capable of utilizing functional biomolecules by incorporating an enzyme into the SRT multilayer. Urease was chosen as a model enzyme of interest to test its activity via fluorescence assay. Successful construction of the SRT films demonstrates the use of mechanically stable self-healing coatings, which can incorporate biomolecules for more complex protective functionalities for advanced functional fabrics. PMID:27419265

  2. Self-Healing Textile: Enzyme Encapsulated Layer-by-Layer Structural Proteins.

    PubMed

    Gaddes, David; Jung, Huihun; Pena-Francesch, Abdon; Dion, Genevieve; Tadigadapa, Srinivas; Dressick, Walter J; Demirel, Melik C

    2016-08-10

    Self-healing materials, which enable an autonomous repair response to damage, are highly desirable for the long-term reliability of woven or nonwoven textiles. Polyelectrolyte layer-by-layer (LbL) films are of considerable interest as self-healing coatings due to the mobility of the components comprising the film. In this work mechanically stable self-healing films were fabricated through construction of a polyelectrolyte LbL film containing squid ring teeth (SRT) proteins. SRTs are structural proteins with unique self-healing properties and high elastic modulus in both dry and wet conditions (>2 GPa) due to their semicrystalline architecture. We demonstrate LbL construction of multilayers containing native and recombinant SRT proteins capable of self-healing defects. Additionally, we show these films are capable of utilizing functional biomolecules by incorporating an enzyme into the SRT multilayer. Urease was chosen as a model enzyme of interest to test its activity via fluorescence assay. Successful construction of the SRT films demonstrates the use of mechanically stable self-healing coatings, which can incorporate biomolecules for more complex protective functionalities for advanced functional fabrics.

  3. Lap shear strength and healing capability of self-healing adhesive containing epoxy/mercaptan microcapsules

    NASA Astrophysics Data System (ADS)

    Ghazali, Habibah; Ye, Lin; Zhang, Ming-Qiu

    2016-03-01

    The aim of this work is to develop a self-healing polymeric adhesive formulation with epoxy/mercaptan microcapsules. Epoxy/mercaptan microcapsules were dispersed into a commercialize two-part epoxy adhesive for developing self-healing epoxy adhesive. The influence of different content of microcapsules on the shear strength and healing capability of epoxy adhesive were investigated using single-lap-joints with average thickness of adhesive layer of about 180 µm. This self-healing adhesive was used in bonding of 5000 series aluminum alloys adherents after mechanical and alkaline cleaning surface treatment. The adhesion strength was measured and presented as function of microcapsules loading. The results indicated that the virgin lap shear strength was increased by about 26% with addition of 3 wt% of self-healing microcapsules. 12% to 28% recovery of the shear strength is achieved after self-healing depending on the microcapsules content. Scanning electron microscopy was used to study fracture surface of the joints. The self-healing adhesives exhibit recovery of both cohesion and adhesion properties with room temperature healing.

  4. Poly(vinyl alcohol)-Poly(ethylene glycol) Double-Network Hydrogel: A General Approach to Shape Memory and Self-Healing Functionalities.

    PubMed

    Li, Guo; Zhang, Hongji; Fortin, Daniel; Xia, Hesheng; Zhao, Yue

    2015-10-27

    A double-network polymer hydrogel composed of chemically cross-linked poly(ethylene glycol) (PEG) and physically cross-linked poly(vinyl alcohol) (PVA) was prepared. When the hydrogel (70 wt % of water) is subjected to freezing/thawing treatment under strain, the enhanced physical network as a result of crystallization of PVA chains can stabilize the hydrogel deformation after removal of the external force at room temperature. Subsequent disruption of the physical network of PVA by heating allows for the recovery of the initial shape of the hydrogel. Moreover, the double-network hydrogel exhibits self-healing capability stemming from the physical network of PVA by virtue of the extensive interchain hydrogen bonding between the hydroxyl side groups. This study thus demonstrates a general approach to imparting both the shape memory and self-healing properties to chemically cross-linked hydrogels that otherwise do not have such functionalities. Moreover, by making use of the fixed hydrogel elongation, the effect of anisotropy arising from chain orientation on the self-healing was also observed.

  5. Microencapsulation of self-healing agents with melamine-urea-formaldehyde by the Shirasu Porous Glass (SPG) emulsification technique

    NASA Astrophysics Data System (ADS)

    Liu, Xing; Lee, Jong Keun; Kessler, Michael R.

    2009-07-01

    Norbornene-based healing agent candidates, ENB (5-ethylidene-2-norbornene) and ENB with a custom crosslinker, were prepared into a uniform microsphere utilizing a Shirasu Porous Glass (SPG) emulsification technique, and microencapsulated by in-situ polymerization of melamine-urea-formaldehyde (MUF). Resulting microcapsules were observed under optical and scanning electron microscopy for their morphology, outer and inner surface, and shell thickness. Particle size analysis showed more uniform size distribution with a mean diameter of 40 μm, compared to a conventional method using a mechanical impeller. The thermal and mechanical properties of the microcapsules were also examined considering fabrication of self-healing composites.

  6. Polymer compositions based on PXE

    SciTech Connect

    Yang, Jin; Eitouni, Hany Basam; Singh, Mohit

    2015-09-15

    New polymer compositions based on poly(2,6-dimethyl-1,4-phenylene oxide) and other high-softening-temperature polymers are disclosed. These materials have a microphase domain structure that has an ionically-conductive phase and a phase with good mechanical strength and a high softening temperature. In one arrangement, the structural block has a softening temperature of about 210.degree. C. These materials can be made with either homopolymers or with block copolymers.

  7. Photodegradation and self-healing in a Rhodamine 6G dye and nanoparticle-doped polyurethane random laser

    NASA Astrophysics Data System (ADS)

    Anderson, Benjamin R.; Gunawidjaja, Ray; Eilers, Hergen

    2015-07-01

    One of the fundamental difficulties in implementing organic dyes in random lasers is irreversible photodegradation of the dye molecules, leading to loss of performance and the need to replace the dye. We report the observation of self-healing after photodegradation in a Rhodamine 6G dye and nanoparticle-doped polyurethane random laser. During irradiation, we observe two distinct temporal regions in which the random lasing emission first increases in intensity and redshifts, followed by further redshifting, spectral broadening, and decay in the emission intensity. After irradiation, the emission intensity is found to recover back to its peak value, while still being broadened and redshifted, which leads to the result of an enhancement of the spectrally integrated intensity. We also perform IR-VIS absorbance measurements and find that the results suggest that during irradiation, some of the dye molecules form dimers and trimers and that the polymer host is irreversibly damaged by photooxidation and Norrish type I photocleavage.

  8. Conductive polymer-based material

    SciTech Connect

    McDonald, William F.; Koren, Amy B.; Dourado, Sunil K.; Dulebohn, Joel I.; Hanchar, Robert J.

    2007-04-17

    Disclosed are polymer-based coatings and materials comprising (i) a polymeric composition including a polymer having side chains along a backbone forming the polymer, at least two of the side chains being substituted with a heteroatom selected from oxygen, nitrogen, sulfur, and phosphorus and combinations thereof; and (ii) a plurality of metal species distributed within the polymer. At least a portion of the heteroatoms may form part of a chelation complex with some or all of the metal species. In many embodiments, the metal species are present in a sufficient concentration to provide a conductive material, e.g., as a conductive coating on a substrate. The conductive materials may be useful as the thin film conducting or semi-conducting layers in organic electronic devices such as organic electroluminescent devices and organic thin film transistors.

  9. Polyphosphazine-based polymer materials

    DOEpatents

    Fox, Robert V.; Avci, Recep; Groenewold, Gary S.

    2010-05-25

    Methods of removing contaminant matter from porous materials include applying a polymer material to a contaminated surface, irradiating the contaminated surface to cause redistribution of contaminant matter, and removing at least a portion of the polymer material from the surface. Systems for decontaminating a contaminated structure comprising porous material include a radiation device configured to emit electromagnetic radiation toward a surface of a structure, and at least one spray device configured to apply a capture material onto the surface of the structure. Polymer materials that can be used in such methods and systems include polyphosphazine-based polymer materials having polyphosphazine backbone segments and side chain groups that include selected functional groups. The selected functional groups may include iminos, oximes, carboxylates, sulfonates, .beta.-diketones, phosphine sulfides, phosphates, phosphites, phosphonates, phosphinates, phosphine oxides, monothio phosphinic acids, and dithio phosphinic acids.

  10. Development of novel self-healing and antibacterial dental composite containing calcium phosphate nanoparticles

    PubMed Central

    Wu, Junling; Weir, Michael D.; Melo, Mary Anne S.; Xu, Hockin H. K.

    2015-01-01

    Objectives Fracture and secondary caries are the primary reasons for dental restoration failure. The objective of this study was to develop a self-healing composite to heal cracks, while containing dimethylaminohexadecyl methacrylate (DMAHDM) for antibacterial function and nanoparticles of amorphous calcium phosphate (NACP) for remineralization. Methods Microcapsules were synthesized with poly(urea-formaldehyde) (PUF) shells containing triethylene glycol dimethacrylate (TEGDMA) and N,N-dihydroxyethyl-p-toluidine (DHEPT) as healing liquid. Composite contained 20 mass% of NACP and 35% glass fillers. In addition, composite contained 0%, 2.5%, 5%, 7.5%, or 10% of microcapsules. A single edge V-notched beam method measured fracture toughness (KIC) and self-healing efficiency. A dental plaque microcosm biofilm model was used to test the antibacterial properties. Results Incorporation of microcapsules up to 7.5% into the composite did not adversely affect the mechanical properties (p > 0.1). Successful self-healing was achieved, with KIC recovery of 65–81% (mean ± sd; n = 6) to regain the load-bearing capability after composite fracture. The self-healing DMAHDM-NACP composite displayed a strong antibacterial potency, inhibiting biofilm viability and lactic acid production, and reducing colony-forming units by 3–4 orders of magnitude, compared to control composite without DMAHDM. Conclusions A dental composite was developed with triple benefits of self-healing after fracture, antibacterial activity, and remineralization capability for the first time. Clinical significance The self-healing, antibacterial and remineralizing composite may be promising for tooth cavity restorations to combat bulk fracture and secondary caries. The method of using triple agents (self-healing microcapsules, DMAHDM, and NACP) may have wide applicability to other dental composites, adhesives, sealants and cements. PMID:25625674

  11. Self healing of high strength concrete after deterioration by freeze/thaw

    SciTech Connect

    Jacobsen, S.; Sellevold, E.J.

    1996-01-01

    Some experiments have been performed to investigate the self healing of concretes deteriorated by internal cracking in the ASTM C666 procedure A rapid freeze/thaw test. Six different well cured concretes were deteriorated to various degrees. Then the specimens (concrete beams) were stored in water for 2--3 months. Resonance frequency, weight, volume and compressive strength were measured during deterioration and self healing. Concretes that lost as much as 50% of their initial relative dynamic modulus during freeze/thaw could recover almost completely during subsequent storage in water, somewhat varying with concrete composition and degree of deterioration. Compressive strength showed reductions of 22--29% on deterioration, but only 4--5% recovery on self healing. Freeze/thaw tests on deteriorated and self-healed specimens in partly sealed condition showed clearly that the deterioration was governed by the ability to take up water; the more water that leaked through the plastic foil during freeze/thaw, the larger the deterioration. Self healing may be an important factor giving concrete better frost durability in field than when submitting specimens to freeze/thaw cycles in water.

  12. Monitoring the self-healing process of biomimetic mortar using coda wave interferometry method

    NASA Astrophysics Data System (ADS)

    Liu, Shukui; Basaran, Zeynep; Zhu, Jinying; Ferron, Raissa

    2014-02-01

    Internal stresses might induce microscopic cracks in concrete, which can provide pathways for ingress of harmful chemicals and can lead to loss of strength. Recent research in concrete materials suggests that it might be possible to develop a smart cement-based material that is capable of self-healing by leveraging the metabolic activity of microorganisms to provide biomineralization. Limited research on biomineralization in cement-based systems has shown promising results that healing of cracks can occur on the surface of concrete and reduce permeability. This paper presents the results from an investigation regarding the potential for a cement-based material to repair itself internally through biomineralization. Compressive strength test and coda wave interferometry (CWI) analyses were conducted on mortar samples that were loaded to 70% of their compressive strength and cured in different conditions. Experimental results indicate that the damaged mortar samples with microorganisms showed significantly higher strength development and higher increase of ultrasonic wave velocity compared to samples without microorganisms at 7 and 28 days.

  13. Screening of bacteria for self-healing of concrete cracks and optimization of the microbial calcium precipitation process.

    PubMed

    Zhang, J L; Wu, R S; Li, Y M; Zhong, J Y; Deng, X; Liu, B; Han, N X; Xing, F

    2016-08-01

    A novel high-throughput strategy was developed to determine the calcium precipitation activity (CPA) of mineralization bacteria used for self-healing of concrete cracks. A bacterial strain designated as H4 with the highest CPA of 94.8 % was screened and identified as a Bacillus species based on 16S rDNA sequence and phylogenetic tree analysis. Furthermore, the effects of certain influential factors on the microbial calcium precipitation process of H4 were evaluated. The results showed that lactate and nitrate are the best carbon and nitrogen sources, with optimal concentrations of approximately 25 and 18 mM, respectively. The H4 strain is able to maintain a high CPA in the pH range of 9.5-11.0, and a suitable initial spore concentration is 4.0 × 10(7) spores/ml. Moreover, an ambient Ca(2+) concentration greater than 60 mM resulted in a serious adverse impact not only on the CPA but also on the growth of H4, suggesting that the maintenance of the Ca(2+) concentration at a low level is necessary for microbial self-healing of concrete cracks.

  14. Application of modified-alginate encapsulated carbonate producing bacteria in concrete: a promising strategy for crack self-healing

    PubMed Central

    Wang, Jianyun; Mignon, Arn; Snoeck, Didier; Wiktor, Virginie; Van Vliergerghe, Sandra; Boon, Nico; De Belie, Nele

    2015-01-01

    Self-healing concrete holds promising benefits to reduce the cost for concrete maintenance and repair as cracks are autonomously repaired without any human intervention. In this study, the application of a carbonate precipitating bacterium Bacillus sphaericus was explored. Regarding the harsh condition in concrete, B. sphaericus spores were first encapsulated into a modified-alginate based hydrogel (AM-H) which was proven to have a good compatibility with the bacteria and concrete regarding the influence on bacterial viability and concrete strength. Experimental results show that the spores were still viable after encapsulation. Encapsulated spores can precipitate a large amount of CaCO3 in/on the hydrogel matrix (around 70% by weight). Encapsulated B. sphaericus spores were added into mortar specimens and bacterial in situ activity was demonstrated by the oxygen consumption on the mimicked crack surface. While specimens with free spores added showed no oxygen consumption. This indicates the efficient protection of the hydrogel for spores in concrete. To conclude, the AM-H encapsulated carbonate precipitating bacteria have great potential to be used for crack self-healing in concrete applications. PMID:26528254

  15. Screening of bacteria for self-healing of concrete cracks and optimization of the microbial calcium precipitation process.

    PubMed

    Zhang, J L; Wu, R S; Li, Y M; Zhong, J Y; Deng, X; Liu, B; Han, N X; Xing, F

    2016-08-01

    A novel high-throughput strategy was developed to determine the calcium precipitation activity (CPA) of mineralization bacteria used for self-healing of concrete cracks. A bacterial strain designated as H4 with the highest CPA of 94.8 % was screened and identified as a Bacillus species based on 16S rDNA sequence and phylogenetic tree analysis. Furthermore, the effects of certain influential factors on the microbial calcium precipitation process of H4 were evaluated. The results showed that lactate and nitrate are the best carbon and nitrogen sources, with optimal concentrations of approximately 25 and 18 mM, respectively. The H4 strain is able to maintain a high CPA in the pH range of 9.5-11.0, and a suitable initial spore concentration is 4.0 × 10(7) spores/ml. Moreover, an ambient Ca(2+) concentration greater than 60 mM resulted in a serious adverse impact not only on the CPA but also on the growth of H4, suggesting that the maintenance of the Ca(2+) concentration at a low level is necessary for microbial self-healing of concrete cracks. PMID:26883348

  16. Application of modified-alginate encapsulated carbonate producing bacteria in concrete: a promising strategy for crack self-healing.

    PubMed

    Wang, Jianyun; Mignon, Arn; Snoeck, Didier; Wiktor, Virginie; Van Vliergerghe, Sandra; Boon, Nico; De Belie, Nele

    2015-01-01

    Self-healing concrete holds promising benefits to reduce the cost for concrete maintenance and repair as cracks are autonomously repaired without any human intervention. In this study, the application of a carbonate precipitating bacterium Bacillus sphaericus was explored. Regarding the harsh condition in concrete, B. sphaericus spores were first encapsulated into a modified-alginate based hydrogel (AM-H) which was proven to have a good compatibility with the bacteria and concrete regarding the influence on bacterial viability and concrete strength. Experimental results show that the spores were still viable after encapsulation. Encapsulated spores can precipitate a large amount of CaCO3 in/on the hydrogel matrix (around 70% by weight). Encapsulated B. sphaericus spores were added into mortar specimens and bacterial in situ activity was demonstrated by the oxygen consumption on the mimicked crack surface. While specimens with free spores added showed no oxygen consumption. This indicates the efficient protection of the hydrogel for spores in concrete. To conclude, the AM-H encapsulated carbonate precipitating bacteria have great potential to be used for crack self-healing in concrete applications.

  17. Self-healing of cracks in Ag joining layer for die-attachment in power devices

    NASA Astrophysics Data System (ADS)

    Chen, Chuantong; Nagao, Shijo; Suganuma, Katsuaki; Jiu, Jinting; Zhang, Hao; Sugahara, Tohru; Iwashige, Tomohito; Sugiura, Kazuhiko; Tsuruta, Kazuhiro

    2016-08-01

    Sintered silver (Ag) joining has attracted significant interest in power devices modules for its ability to form stable joints with a porous interconnection layer. A function for the self-healing of cracks in sintered porous Ag interlayers at high temperatures is discovered and reported here. A crack which was prepared on a Ag joining layer was closed after heating at 200 °C in air. The tensile strength of pre-cracked Ag joining layer specimens recovers to the value of non-cracked specimens after heating treatment. Transmission electron microscopy (TEM) was used to probe the self-healing mechanism. TEM images and electron diffraction patterns show that a large quantity of Ag nanoparticles formed at the gap with the size less than 10 nm, which bridges the crack in the self-healing process. This discovery provides additional motivation for the application of Ag as an interconnection material for power devices at high temperature.

  18. Modeling of plasma-induced self-healing in organic dielectrics

    NASA Astrophysics Data System (ADS)

    Kammermaier, J.; Rittmayer, G.; Birkle, S.

    1989-08-01

    Plasma-induced self-healing in organic dielectrics, which is of extremely great importance for capacitor technology, is dependent, in a complicated manner, upon electrical and physicochemical processes, which cannot be determined by metrology. Accordingly, a theoretical model was developed which describes the spatiotemporal distribution of potential and current in the plasma of a self-healing breakdown, the formation of gas as a consequence of decomposition of material, and the consequent graphite deposition in the insulating areas. In this way it is also possible to compute the insulating areas as well as the entire gas formation as a function of voltage, capacitance, and thickness of the metal electrodes, and the limits for reliable self-healing.

  19. Measuring the self-healing of the spatially inhomogeneous states of polarization of vector Bessel beams

    NASA Astrophysics Data System (ADS)

    Milione, Giovanni; Dudley, Angela; Nguyen, Thien An; Chakraborty, Ougni; Karimi, Ebrahim; Forbes, Andrew; Alfano, Robert R.

    2015-03-01

    We experimentally measured the self-healing of the spatially inhomogeneous states of polarization of vector Bessel beams. Radially and azimuthally polarized vector Bessel beams were experimentally generated via a digital version of Durnin's method, using a spatial light modulator in concert with a liquid crystal q-plate. As a proof of principle, their intensities and spatially inhomogeneous states of polarization were experimentally measured using Stokes polarimetry as they propagated through two disparate obstructions. It was found, similar to their intensities, that their spatially inhomogeneous states of polarization self-healed. The self-healing can be understood via geometric optics, i.e., the interference of the unobstructed conical rays in the shadow region of the obstruction, and may have applications in, for example, optical trapping.

  20. Microencapsulation of 2-octylcyanoacrylate tissue adhesive for self-healing acrylic bone cement

    PubMed Central

    Brochu, Alice B. W.; Chyan, William J.; Reichert, William M.

    2014-01-01

    Here, we report the first phase of developing self-healing acrylic bone cement: the preparation and characterization of polyurethane (PUR) microcapsules containing a medical cyanoacrylate tissue adhesive. Capsules were prepared by interfacial polymerization of a toluene-2,4-diisocyanate-based polyurethane prepolymer with 1,4-butanediol to encapsulate 2-octylcyanoacrylate (OCA). Various capsule characteristics, including: resultant morphology, average size and size distribution, shell thickness, content and reactivity of encapsulated agent, and shelf life are investigated and their reliance on solvent type and amount, surfactant type and amount, temperature, pH, agitation rate, reaction time, and mode of addition of the oil phase to the aqueous phase are presented. Capsules had average diameters ranging from 74 to 222 μm and average shell thicknesses ranging from 1.5 to 6 μm. The capsule content was determined via thermogravimetric analysis and subsequent analysis of the capsules following up to 8 weeks storage revealed minimal loss of core contents. Mechanical testing of OCA-containing capsules showed individual capsules withstood compressive forces up to a few tenths of Newtons, and the contents released from crushed capsules generated tensile adhesive forces of a few Newtons. Capsules were successfully mixed into the poly(- methyl methacrylate) bone cement, surviving the mixing process, exposure to methyl methacrylate monomer, and the resulting exothermic matrix curing. PMID:22807313

  1. High-Temperature, Lightweight, Self-Healing Ceramic Composites for Aircraft Engine Applications

    NASA Technical Reports Server (NTRS)

    Raj, Sai V.; Bhatt, Ramkrishna

    2013-01-01

    The use of reliable, high-temperature, lightweight materials in the manufacture of aircraft engines is expected to result in lower fossil and biofuel consumption, thereby leading to cost savings and lower carbon emissions due to air travel. Although nickel-based superalloy blades and vanes have been successfully used in aircraft engines for several decades, there has been an increased effort to develop high-temperature, lightweight, creep-resistant substitute materials under various NASA programs over the last two decades. As a result, there has been a great deal of interest in developing SiC/SiC ceramic matrix composites (CMCs) due to their higher damage tolerance compared to monolithic ceramics. Current-generation SiC/SiC ceramic matrix composites rely almost entirely on the SiC fibers to carry the load, owing to the premature cracking of the matrix during loading. Thus, the high-temperature usefulness of these CMCs falls well below their theoretical capabilities. The objective of this work is to develop a new class of high-temperature, lightweight, self-healing, SiC fiber-reinforced, engineered matrix ceramic composites.

  2. Microencapsulation of 2-octylcyanoacrylate tissue adhesive for self-healing acrylic bone cement.

    PubMed

    Brochu, Alice B W; Chyan, William J; Reichert, William M

    2012-10-01

    Here, we report the first phase of developing self-healing acrylic bone cement: the preparation and characterization of polyurethane (PUR) microcapsules containing a medical cyanoacrylate tissue adhesive. Capsules were prepared by interfacial polymerization of a toluene-2,4-diisocyanate-based polyurethane prepolymer with 1,4-butanediol to encapsulate 2-octylcyanoacrylate (OCA). Various capsule characteristics, including: resultant morphology, average size and size distribution, shell thickness, content and reactivity of encapsulated agent, and shelf life are investigated and their reliance on solvent type and amount, surfactant type and amount, temperature, pH, agitation rate, reaction time, and mode of addition of the oil phase to the aqueous phase are presented. Capsules had average diameters ranging from 74 to 222 μm and average shell thicknesses ranging from 1.5 to 6 μm. The capsule content was determined via thermogravimetric analysis and subsequent analysis of the capsules following up to 8 weeks storage revealed minimal loss of core contents. Mechanical testing of OCA-containing capsules showed individual capsules withstood compressive forces up to a few tenths of Newtons, and the contents released from crushed capsules generated tensile adhesive forces of a few Newtons. Capsules were successfully mixed into the poly(methyl methacrylate) bone cement, surviving the mixing process, exposure to methyl methacrylate monomer, and the resulting exothermic matrix curing. PMID:22807313

  3. Healing efficiency and dynamic mechanical properties of self-healing epoxy systems

    NASA Astrophysics Data System (ADS)

    Guadagno, Liberata; Raimondo, Marialuigia; Naddeo, Carlo; Longo, Pasquale; Mariconda, Annaluisa; Binder, Wolfgang H.

    2014-03-01

    Several systems to develop self-repairing epoxy resins have recently been formulated. In this paper the effect of matrix nature and curing cycle on the healing efficiency and dynamic mechanical properties of self-healing epoxy resins were investigated. We discuss several aspects by transferring self-healing systems from the laboratory scale to real applications in the aeronautic field, such as the possibility to choose systems with increased glass transition temperature, high storage modulus and high values in the healing functionality under real working conditions.

  4. Self-healing of optical functions by molecular metabolism in a swollen elastomer

    NASA Astrophysics Data System (ADS)

    Saito, Mitsunori; Nishimura, Tatsuya; Sakiyama, Kohei; Inagaki, Sota

    2012-12-01

    Optical functions of organic dyes, e.g., fluorescence or photochromism, tend to degrade by light irradiation, which causes a short lifetime of photonic devices. Self-healing of optical functions is attainable by metabolizing bleached molecules with nonirradiated ones. A polydimethylsiloxane elastomer provides a useful matrix for dye molecules, since its flexible structure with nano-sized intermolecular spaces allows dye diffusion from a reservoir to an operation region. Swelling the elastomer with a suitable solvent promotes both dissolution and diffusion of dye molecules. This self-healing function was demonstrated by an experiment in which a photochromic elastomer exhibited improved durability against a repeated coloring-decoloring process.

  5. Intumescent flame-retardant and self-healing superhydrophobic coatings on cotton fabric.

    PubMed

    Chen, Shanshan; Li, Xiang; Li, Yang; Sun, Junqi

    2015-04-28

    Flame-retardant and self-healing superhydrophobic coatings are fabricated on cotton fabric by a convenient solution-dipping method, which involves the sequential deposition of a trilayer of branched poly(ethylenimine) (bPEI), ammonium polyphosphate (APP), and fluorinated-decyl polyhedral oligomeric silsesquioxane (F-POSS). When directly exposed to flame, such a trilayer coating generates a porous char layer because of its intumescent effect, successfully giving the coated fabric a self-extinguishing property. Furthermore, the F-POSS embedded in cotton fabric and APP/bPEI coating produces a superhydrophobic surface with a self-healing function. The coating can repetitively and autonomically restore the superhydrophobicity when the superhydrophobicity is damaged. The resulting cotton fabric, which is flame-resistant, waterproof, and self-cleaning, can be easily cleaned by simple water rinsing. Thus, the integration of self-healing superhydrophobicity with flame retardancy provides a practical way to resolve the problem of washing durability of the flame-retardant coatings. The flame-retardant and superhydrophobic fabric can endure more than 1000 cycles of abrasion under a pressure of 44.8 kPa without losing its flame retardancy and self-healing superhydrophobicity, showing potential applications as multifunctional advanced textiles.

  6. Anti-Fogging/Self-Healing Properties of Clay-Containing Transparent Nanocomposite Thin Films.

    PubMed

    England, Matt W; Urata, Chihiro; Dunderdale, Gary J; Hozumi, Atsushi

    2016-02-01

    Highly transparent antifogging films were successfully prepared on various substrates, including glass slides, silicon, copper and PMMA, by spin-coating a mixture of polyvinylpyrrolidone and aminopropyl-functionalized, nanoscale clay platelets. The resulting films were superhydrophilic and showed more than 90% transmission of visible light, as well as excellent antifogging and self-healing properties. PMID:26845075

  7. A novel methodology for self-healing at the nanoscale in CNT/epoxy composites

    NASA Astrophysics Data System (ADS)

    Quigley, E.; Datta, S.; Chattopadhyay, A.

    2016-04-01

    Self-healing materials have the potential to repair induced damage and extend the service life of aerospace or civil components as well as prevent catastrophic failure. A novel technique to provide self-healing capabilities at the nanoscale in carbon nanotube/epoxy nanocomposites is presented in this paper. Carbon nanotubes (CNTs) functionalized with the healing agent (dicyclopentadiene) were used to fabricate self-healing CNT/epoxy nanocomposite films. The structure of CNTs was considered suitable for this application since they are nanosized, hollow, and provide a more consistent size distribution than polymeric nanocapsules. Specimens with different weight fractions of the functionalized CNTs were fabricated to explore the effect of weight fraction of functionalized CNTs on the extent of healing. Optical micrographs with different fluorescent filters showed partial or complete healing of damage approximately two to three weeks after damage was induced. Results indicate that by using CNTs to encapsulate a healing agent, crack growth in self-healing CNT/epoxy nanocomposites can be retarded, leading to safer materials that can autonomously repair itself.

  8. Self-Healing Glassy Thin Coating for High-Temperature Applications.

    PubMed

    Castanié, Sandra; Carlier, Thibault; Méar, François O; Saitzek, Sébastien; Blach, Jean-François; Podor, Renaud; Montagne, Lionel

    2016-02-17

    Glass thin films (with nanometer to micrometer thicknesses) are promising in numerous applications, both as passive coatings and as active components. Self-healing is a feature of many current technological developments as a means of increasing the lifetime of materials. In the context of these developments, we report on the elaboration of the first self-healing glassy thin-film coating developed specifically for high-temperature applications. This coating is obtained by pulsed laser deposition of alternating layers of vanadium boride (VB) and a multicomponent oxide glass. Self-healing is obtained through the oxidation of VB at the operating temperature. The investigation of the effect of elaboration parameters on the coating composition and morphology made it possible to obtain up to seven-layer coatings, with good homogeneity and perfect interfaces, and with a total thickness of less than 1 μm. The autonomic self-healing capacity of the coating has been demonstrated by an in situ experiment, which shows that a crack of nanometric dimension can be healed within a few minutes at 700 °C. PMID:26808059

  9. Robust Self-Healing Hydrogels Assisted by Cross-Linked Nanofiber Networks

    PubMed Central

    Fang, Yuan; Wang, Cai-Feng; Zhang, Zhi-Hong; Shao, Huan; Chen, Su

    2013-01-01

    Given increasing environmental and energy issues, mimicking nature to confer synthetic materials with self-healing property to expand their lifespan is highly desirable. Just like human skin recovers itself upon damage with the aid of nutrient-laden blood vascularization, designing smart materials with microvascular network to accelerate self-healing is workable but continues to be a challenge. Here we report a new strategy to prepare robust self-healing hydrogels assisted by a healing layer composed of electrospun cross-linked nanofiber networks containing redox agents. The hydrogels process high healing rate ranging from seconds to days and great mechanical strengths with storage modulus up to 0.1 MPa. More interestingly, when the healing layer is embedded into the crack of the hydrogel, accelerated self-healing is observed and the healing efficiency is about 80%. The healing layer encourages molecular diffusion as well as further cross-linking in the crack region of the hydrogel, responsible for enhanced healing efficiency. PMID:24091865

  10. Novel mussel-inspired injectable self-healing hydrogel with anti-biofouling property.

    PubMed

    Li, Lin; Yan, Bin; Yang, Jingqi; Chen, Lingyun; Zeng, Hongbo

    2015-02-18

    A novel mussel-inspired injectable hydrogel with self-healing and anti-biofouling capabilities is developed and it possesses great potential as a drug-delivery carrier. The hydrogel can heal autonomously from repeated structural damage and also effectively prevent non-specific cell attachment and biofilm formation.

  11. Effect of link oriented self-healing on resilience of networks

    NASA Astrophysics Data System (ADS)

    Shang, Yilun

    2016-08-01

    Many real, complex systems, such as the human brain and skin with their biological networks or intelligent material systems consisting of composite functional liquids, exhibit a noticeable capability of self-healing. Here, we study a network model with arbitrary degree distributions possessing natural link oriented recovery mechanisms, whereby a failed link can be recovered if its two end nodes maintain a sufficient proportion of functional links. These mechanisms are pertinent for many spontaneous healing and manual repair phenomena, interpolating smoothly between complete healing and no healing scenarios. We show that the self-healing strategies have profound impact on resilience of homogeneous and heterogeneous networks employing a percolation threshold, fraction of giant cluster, and link robustness index. The self-healing effect induces distinct resilience characteristics for scale-free networks under random failures and intentional attacks, and a resilience crossover has been observed at certain level of self-healing. Our work highlights the significance of understanding the competition between healing and collapsing in the resilience of complex networks.

  12. Intumescent flame-retardant and self-healing superhydrophobic coatings on cotton fabric.

    PubMed

    Chen, Shanshan; Li, Xiang; Li, Yang; Sun, Junqi

    2015-04-28

    Flame-retardant and self-healing superhydrophobic coatings are fabricated on cotton fabric by a convenient solution-dipping method, which involves the sequential deposition of a trilayer of branched poly(ethylenimine) (bPEI), ammonium polyphosphate (APP), and fluorinated-decyl polyhedral oligomeric silsesquioxane (F-POSS). When directly exposed to flame, such a trilayer coating generates a porous char layer because of its intumescent effect, successfully giving the coated fabric a self-extinguishing property. Furthermore, the F-POSS embedded in cotton fabric and APP/bPEI coating produces a superhydrophobic surface with a self-healing function. The coating can repetitively and autonomically restore the superhydrophobicity when the superhydrophobicity is damaged. The resulting cotton fabric, which is flame-resistant, waterproof, and self-cleaning, can be easily cleaned by simple water rinsing. Thus, the integration of self-healing superhydrophobicity with flame retardancy provides a practical way to resolve the problem of washing durability of the flame-retardant coatings. The flame-retardant and superhydrophobic fabric can endure more than 1000 cycles of abrasion under a pressure of 44.8 kPa without losing its flame retardancy and self-healing superhydrophobicity, showing potential applications as multifunctional advanced textiles. PMID:25777158

  13. Photoresponsive self-healing supramolecular hydrogels for light-induced release of DNA and doxorubicin.

    PubMed

    Pianowski, Zbigniew L; Karcher, Johannes; Schneider, Knut

    2016-02-21

    An azobenzene-containing cyclic dipeptide PAP-DKP-Lys is a photoresponsive low-MW hydrogelator. The gelation process can be triggered with temperature, pH, light, and ionic strength. The resulting self-healing gels can encapsulate dsDNA or an anticancer drug doxorubicin, and release them in a light-dependent manner. PMID:26804160

  14. X-ray computed microtomography of three-dimensional microcracks and self-healing in engineered cementitious composites

    NASA Astrophysics Data System (ADS)

    Fan, Shuai; Li, Mo

    2015-01-01

    Concrete cracking and deterioration can potentially be addressed by innovative self-healing cementitious materials, which can autogenously regain transport properties and mechanical characteristics after the damage self-healing process. For the development of such materials, it is crucial, but challenging, to precisely characterize the extent and quality of self-healing due to a variety of factors. This study adopted x-ray computed microtomography (μCT) to derive three-dimensional morphological data on microcracks before and after healing in engineered cementitious composite (ECC). Scanning electron microscope and energy dispersive x-ray spectroscopy were also used to morphologically and chemically analyze the healing products. This work showed that the evolution of the microcrack 3D structure due to self-healing in cementitious materials can be directly and quantitatively characterized by μCT. A detailed description of the μCT image analysis method applied to ECC self-healing was presented. The results revealed that the self-healing extent and rate strongly depended on initial surface crack width, with smaller crack width favoring fast and robust self-healing. We also found that the self-healing mechanism in cementitious materials is dependent on crack depth. The region of a crack close to the surface (from 0 to around 50-150 μm below the surface) can be sealed quickly with crystalline precipitates. However, at greater depths the healing process inside the crack takes a significantly longer time to occur, with healing products more likely resulting from continued hydration and pozzolanic reactions. Finally, the μCT method was compared with other self-healing characterization methods, with discussions on its importance in generating new scientific knowledge for the development of robust self-healing cementitious materials.

  15. Polymer Chemistry

    NASA Technical Reports Server (NTRS)

    Williams, Martha; Roberson, Luke; Caraccio, Anne

    2010-01-01

    This viewgraph presentation describes new technologies in polymer and material chemistry that benefits NASA programs and missions. The topics include: 1) What are Polymers?; 2) History of Polymer Chemistry; 3) Composites/Materials Development at KSC; 4) Why Wiring; 5) Next Generation Wiring Materials; 6) Wire System Materials and Integration; 7) Self-Healing Wire Repair; 8) Smart Wiring Summary; 9) Fire and Polymers; 10) Aerogel Technology; 11) Aerogel Composites; 12) Aerogels for Oil Remediation; 13) KSC's Solution; 14) Chemochromic Hydrogen Sensors; 15) STS-130 and 131 Operations; 16) HyperPigment; 17) Antimicrobial Materials; 18) Conductive Inks Formulations for Multiple Applications; and 19) Testing and Processing Equipment.

  16. Synthesis of cyanopyridine based conjugated polymer.

    PubMed

    Hemavathi, B; Ahipa, T N; Pillai, Saju; Pai, Ranjith Krishna

    2016-06-01

    This data file contains the detailed synthetic procedure for the synthesis of two new cyanopyridine based conjugated polymer P1 and P2 along with the synthesis of its monomers. The synthesised polymers can be used for electroluminescence and photovoltaic (PV) application. The physical data of the polymers are provided in this data file along with the morphological data of the polymer thin films. The data provided here are in association with the research article entitled 'Cyanopyridine based conjugated polymer-synthesis and characterisation' (Hemavathi et al., 2015) [3]. PMID:27158642

  17. Water-assisted self-healing and property recovery in a natural dermal armor of pangolin scales.

    PubMed

    Liu, Z Q; Jiao, D; Weng, Z Y; Zhang, Z F

    2016-03-01

    Self-healing capacity, of which the inspiration comes from biological systems, is significant for restoring the mechanical properties of materials by autonomically repairing damages. Clarifying the naturally occurring self-healing behaviors and mechanisms may provide valuable inspiration for designing synthetic self-healing materials. In this study, water-assisted self-healing behavior was revealed in a natural dermal armor of pangolin scales. The indentation damages which imitate the injury caused by predatory attack can be continuously mitigated through hydration. The healing kinetics was characterized according to the variations of indentation crater dimension and quantitatively described in terms of the viscoelastic behavior of biopolymer. The mechanical properties of original, damaged, and recovered scales in both dry and wet states were systematically evaluated by three-point bending and compared through statistical analysis. The hydration effects and mechanisms were explored by examining the dynamic mechanical properties and thermal behaviors. The promoted self-healing process can be attributed to the improved flexibility of macromolecules in the biopolymer. This study may stimulate useful self-healing strategies in bio-inspired design and aid in developing high-performance synthetic self-healing materials. PMID:26651064

  18. Water-assisted self-healing and property recovery in a natural dermal armor of pangolin scales.

    PubMed

    Liu, Z Q; Jiao, D; Weng, Z Y; Zhang, Z F

    2016-03-01

    Self-healing capacity, of which the inspiration comes from biological systems, is significant for restoring the mechanical properties of materials by autonomically repairing damages. Clarifying the naturally occurring self-healing behaviors and mechanisms may provide valuable inspiration for designing synthetic self-healing materials. In this study, water-assisted self-healing behavior was revealed in a natural dermal armor of pangolin scales. The indentation damages which imitate the injury caused by predatory attack can be continuously mitigated through hydration. The healing kinetics was characterized according to the variations of indentation crater dimension and quantitatively described in terms of the viscoelastic behavior of biopolymer. The mechanical properties of original, damaged, and recovered scales in both dry and wet states were systematically evaluated by three-point bending and compared through statistical analysis. The hydration effects and mechanisms were explored by examining the dynamic mechanical properties and thermal behaviors. The promoted self-healing process can be attributed to the improved flexibility of macromolecules in the biopolymer. This study may stimulate useful self-healing strategies in bio-inspired design and aid in developing high-performance synthetic self-healing materials.

  19. Self-Healing, Expansion-Contraction, and Shape-Memory Properties of a Preorganized Supramolecular Hydrogel through Host-Guest Interactions.

    PubMed

    Miyamae, Kohei; Nakahata, Masaki; Takashima, Yoshinori; Harada, Akira

    2015-07-27

    Supramolecular materials cross-linked between polymer chains by noncovalent bonds have the potential to provide dynamic functions that are not produced by covalently cross-linked polymeric materials. We focused on the formation of supramolecular polymeric materials through host-guest interactions: a powerful method for the creation of nonconventional materials. We employed two different kinds of host-guest inclusion complexes of β-cyclodextrin (βCD) with adamantane (Ad) and ferrocene (Fc) to bind polymers together to form a supramolecular hydrogel (βCD-Ad-Fc gel). The βCD-Ad-Fc gel showed self-healing ability when damaged and responded to redox stimuli by expansion or contraction. Moreover, the βCD-Ad-Fc gel showed a redox-responsive shape-morphing effect. We thus succeeded in deriving three functions from the introduction of two kinds of functional units into a supramolecular material.

  20. Heat transfer and fluid flow analysis of self-healing in metallic materials

    NASA Astrophysics Data System (ADS)

    Martínez Lucci, J.; Amano, R. S.; Rohatgi, P. K.

    2016-06-01

    This paper explores imparting self-healing characteristics to metal matrices similar to what are observed in biological systems and are being developed for polymeric materials. To impart self-healing properties to metal matrices, a liquid healing method was investigated; the met hod consists of a container filled with low melting alloy acting as a healing agent, embedded into a high melting metal matrix. When the matrix is cracked; self-healing is achieved by melting the healing agent allowing the liquid metal to flow into the crack. Upon cooling, solidification of the healing agent occurs and seals the crack. The objective of this research is to investigate the fluid flow and heat transfer to impart self-healing property to metal matrices. In this study, a dimensionless healing factor, which may help predict the possibility of healing is proposed. The healing factor is defined as the ratio of the viscous forces and the contact area of liquid metal and solid which prevent flow, and volume expansion, density, and velocity of the liquid metal, gravity, crack size and orientation which promote flow. The factor incorporates the parameters that control self-healing mechanism. It was observed that for lower values of the healing factor, the liquid flows, and for higher values of healing factor, the liquid remains in the container and healing does not occur. To validate and identify the critical range of the healing factor, experiments and simulations were performed for selected combinations of healing agents and metal matrices. The simulations were performed for three-dimensional models and a commercial software 3D Ansys-Fluent was used. Three experimental methods of synthesis of self-healing composites were used. The first method consisted of creating a hole in the matrices, and liquid healing agent was poured into the hole. The second method consisted of micro tubes containing the healing agent, and the third method consisted of incorporating micro balloons containing

  1. Conversion in denture base polymers.

    PubMed

    Ruyter, I E; Oysaed, H

    1982-09-01

    The purpose of this investigation was to determine residual monomers, the insoluble gel fraction, and singly reacted dimethacrylate monomers in heat-polymerized, auto-polymerized conventional and pour-type denture base materials. Residual monomers were determined by HPLC analysis of tetrahydrofuran extracts of denture base polymers. The gel fraction was determined by gravimetric analysis of the nonextractable portion. The pendant methacrylate groups in the gel fraction were determined by quantitative IR (infrared) spectrometry. It was demonstrated that the heat-polymerized materials had the lowest content of residual monomers. Generally, the content of pendant methacrylate groups in the gel was dependent on the initial quantity of crosslinking agent in the monomer liquids. The gel fractions of the heat-polymerized materials were larger than the quantity of reacted monomers and were also dependent on the quantity of crosslinking agent. These findings showed that some of the linear prepolymer, poly(methyl methacrylate) (PMMA), had been incorporated into the crosslinked polymer system. The gel fraction of the auto-polymerized pour-type materials corresponded to the quantity of reacted monomers, whereas the conventional auto-polymerized materials took an intermediate position between pour type materials and heat-polymerized materials in this respect.

  2. Polymer-Based Carbon Monoxide Sensors

    NASA Technical Reports Server (NTRS)

    Homer, M. L.; Shevade, A. V.; Zhou, H.; Kisor, A. K.; Lara, L. M.; Yen, S.-P. S.; Ryan, M. A.

    2010-01-01

    Polymer-based sensors have been used primarily to detect volatile organics and inorganics; they are not usually used for smaller, gas phase molecules. We report the development and use of two types of polymer-based sensors for the detection of carbon monoxide. Further understanding of the experimental results is also obtained by performing molecular modeling studies to investigate the polymer-carbon monoxide interactions. The first type is a carbon-black-polymer composite that is comprised of a non-conducting polymer base that has been impregnated with carbon black to make it conducting. These chemiresistor sensors show good response to carbon monoxide but do not have a long lifetime. The second type of sensor has a non-conducting polymer base but includes both a porphyrin-functionalized polypyrrole and carbon black. These sensors show good, repeatable and reversible response to carbon monoxide at room temperature.

  3. Acoustic and ultrasonic characterization constraints of self-healing (ethylene-co-methacrylic acid) copolymers

    NASA Astrophysics Data System (ADS)

    Pestka, Kenneth, II; Buckley, Jonathan; Kalista, Stephen; Bowers, Nicholas

    Recent experiments indicate that small sample poly (ethylene-co-methacrylic acid) copolymers (EMAA copolymers) exhibit time dependent variation in their acoustic and ultrasonic resonant spectra after exposure to a damage event. However, due to the relatively soft nature of these thermoplastic materials, several experimental constraints affect efficacy of resonant spectral analysis. In this work we will the address the effect of several characterization constraints on a self-healing EMAA ionomer (commercially known as Dupont Surlyn 8920) including the effects of transducer loading, continuous rapid resonant excitation and temporally separated long-term resonant excitation. In some circumstances, these experimental constraints can influence the time dependence of sample resonant frequency evolution, quality factor, and variation in spectral waveform. By quantifying these effects, robust characterization of post-damage self-healing EMAA samples is possible and will be presented.

  4. Self-healing of the superhydrophobicity by ironing for the abrasion durable superhydrophobic cotton fabrics

    NASA Astrophysics Data System (ADS)

    Wu, Jingxia; Li, Jingye; Deng, Bo; Jiang, Haiqing; Wang, Ziqiang; Yu, Ming; Li, Linfan; Xing, Chenyang; Li, Yongjin

    2013-10-01

    Self-healing of the superhydrophobic cotton fabric (SCF) obtained by the radiation-induced graft polymerization of lauryl methacrylate (LMA) and n-hexyl methacrylate (HMA), can be achieved by ironing. Through the steam ironing process, the superhydrophobicity of the SCFs will be regenerated even after the yarns are ruptured during the abrasion test under a load pressure of 44.8 kPa. SCFs made from LMA grafted cotton fabric can ultimately withstand at least 24,000 cycles of abrasion with periodic steam ironing. The FT-IR microscope results show that the migration of the polymethacrylates graft chains from the interior to the surface is responsible for the self-healing effect.

  5. Structural health management technologies for inflatable/deployable structures: Integrating sensing and self-healing

    NASA Astrophysics Data System (ADS)

    Brandon, Erik J.; Vozoff, Max; Kolawa, Elizabeth A.; Studor, George F.; Lyons, Frankel; Keller, Michael W.; Beiermann, Brett; White, Scott R.; Sottos, Nancy R.; Curry, Mark A.; Banks, David L.; Brocato, Robert; Zhou, Lisong; Jung, Soyoun; Jackson, Thomas N.; Champaigne, Kevin

    2011-04-01

    Inflatable/deployable structures are under consideration as habitats for future Lunar surface science operations. The use of non-traditional structural materials combined with the need to maintain a safe working environment for extended periods in a harsh environment has led to the consideration of an integrated structural health management system for future habitats, to ensure their integrity. This article describes recent efforts to develop prototype sensing technologies and new self-healing materials that address the unique requirements of habitats comprised mainly of soft goods. A new approach to detecting impact damage is discussed, using addressable flexible capacitive sensing elements and thin film electronics in a matrixed array. Also, the use of passive wireless sensor tags for distributed sensing is discussed, wherein the need for on-board power through batteries or hardwired interconnects is eliminated. Finally, the development of a novel, microencapuslated self-healing elastomer with applications for inflatable/deployable habitats is reviewed.

  6. Self-healing in defective carbon nanotubes: a molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Zhang, Chen-Li; Shen, Hui-Shen

    2007-09-01

    The self-healing phenomenon of defective single-walled carbon nanotubes (SWCNTs) is observed at the atomic level from a molecular dynamics (MD) simulation test. The ideal network of carbon nanotubes is unable to avoid damage under destabilizing loads at high temperature, leading to unforeseen patterns in bond breakages and vacancy defects on the wall. We observe that (10, 10) and (17, 0) carbon nanotubes containing such vacancies are energetically unstable. In the situation of unloading or increasing temperature, the local structures around the vacancies reconstruct through dangling bond saturation, forming non-hexagonal rings, 5-7-7-5 defects or an ideal graphite network. We find that a defective carbon nanotube with large vacancies is re-mendable, and the Stone-Wales (SW) construction is energetically preferred in self-healing processes.

  7. Adult Variant of Self-healing Cutaneous Mucinosis in a Patient with Epilepsy.

    PubMed

    Yaghoobi, Reza; Bagherzade, Arezou; Aliabdi, Maryam; Kheradmand, Parvin; Kazerouni, Afshin; Feily, Amir

    2016-01-01

    A 52-year-old woman was admitted with a 3 weeks history of periorbital edema and lips swelling. She developed several subcutaneous firm erythematous papules and nodules on the face, scalp and two indurated plaques on the upper back and left forearm. These lesions grew rapidly. The patient had a positive history of epileptic seizures since childhood. General examination was normal. There was a mild pitting edema on her hands and feet. Laboratory data were within normal limits. Histopathological examination revealed a well circumscribed accumulation of mucin in the dermis. Alcian blue stain was positive. Clinical and histopathological findings followed by spontaneous resolution of the lesions within a period of 4 months was compatible with diagnosis of self-healing cutaneous mucinosis. Herein we report the first case of self-healing cutaneous mucinosis associated with epilepsy. PMID:27241546

  8. Self-healing of the superhydrophobicity by ironing for the abrasion durable superhydrophobic cotton fabrics

    PubMed Central

    Wu, Jingxia; Li, Jingye; Deng, Bo; Jiang, Haiqing; Wang, Ziqiang; Yu, Ming; Li, Linfan; Xing, Chenyang; Li, Yongjin

    2013-01-01

    Self-healing of the superhydrophobic cotton fabric (SCF) obtained by the radiation-induced graft polymerization of lauryl methacrylate (LMA) and n-hexyl methacrylate (HMA), can be achieved by ironing. Through the steam ironing process, the superhydrophobicity of the SCFs will be regenerated even after the yarns are ruptured during the abrasion test under a load pressure of 44.8 kPa. SCFs made from LMA grafted cotton fabric can ultimately withstand at least 24,000 cycles of abrasion with periodic steam ironing. The FT-IR microscope results show that the migration of the polymethacrylates graft chains from the interior to the surface is responsible for the self-healing effect. PMID:24135813

  9. Integration of the Reconfigurable Self-Healing eDNA Architecture in an Embedded System

    NASA Technical Reports Server (NTRS)

    Boesen, Michael Reibel; Keymeulen, Didier; Madsen, Jan; Lu, Thomas; Chao, Tien-Hsin

    2011-01-01

    In this work we describe the first real world case study for the self-healing eDNA (electronic DNA) architecture by implementing the control and data processing of a Fourier Transform Spectrometer (FTS) on an eDNA prototype. For this purpose the eDNA prototype has been ported from a Xilinx Virtex 5 FPGA to an embedded system consisting of a PowerPC and a Xilinx Virtex 5 FPGA. The FTS instrument features a novel liquid crystal waveguide, which consequently eliminates all moving parts from the instrument. The addition of the eDNA architecture to do the control and data processing has resulted in a highly fault-tolerant FTS instrument. The case study has shown that the early stage prototype of the autonomous self-healing eDNA architecture is expensive in terms of execution time.

  10. Research on spectral resource optimization and self-healing technology of hybrid optical fiber sensing network

    NASA Astrophysics Data System (ADS)

    Chen, Cheng; Sang, Mei; Ge, Chunfeng; Chen, Guanghui; Liu, Tiegen

    2015-08-01

    We propose an optical-fiber-sensing-network (OFSN) to allow hybrid fiber sensors working in the same network and it achieves self-healing function. The discrete and distributed optical fiber sensors can be connected in sub-layers of the network. WDM-OTDM technique is introduced to convert multi-wavelengths of light source into a specific arranged wavelength in each sub-layer. Thus every sub-layer can share the system spectrum resources, and sensing signals of each sub-layer are transmitted together in the backbone network. To achieve self-healing function, double-ring structure is adopted in the backbone network. Node microprocessor program is designed to make switching to the protect fiber when working fiber is broken. The experimental backbone setup of the network demonstrates the practical reliability and intelligence of the optical sensing network.

  11. Injectable Self-Healing Glucose-Responsive Hydrogels with pH-Regulated Mechanical Properties.

    PubMed

    Yesilyurt, Volkan; Webber, Matthew J; Appel, Eric A; Godwin, Colin; Langer, Robert; Anderson, Daniel G

    2016-01-01

    Dynamically restructuring pH-responsive hydrogels are synthesized, employing dynamic covalent chemistry between phenylboronic acid and cis-diol modified poly(ethylene glycol) macromonomers. These gels display shear-thinning behavior, followed by a rapid structural recovery (self-healing). Size-dependent in vitro controlled and glucose-responsive release of proteins from the hydrogel network, as well as the biocompatibility of the gels, are evaluated both in vitro and in vivo.

  12. Preliminary report on self-healing minefield (frogs) concepts and utility in battle

    SciTech Connect

    Greenwalt, R J; Magnoli, D

    2000-01-13

    The purpose of this study is to determine battlefield effectiveness of the self-healing minefield (''Frogs'') concept system compared to basecases of the standard AP/AT (anti-personnel/anti-tank) mixed minefield, the AT (anti-tank) pure minefield, and no minefields. This involves tactical modeling where a basecase with and without mines is compared to the concept system. However, it is first necessary to establish system characteristics and behavior of the Frog mine and minefield in order to do the tactical modeling. This initial report provides emerging insights into various minefield parameters in order to allow better program definition early in the conceptual development. In the following sections of this report, we investigate the self-healing minefield's ground pattern and several concepts for movement (''jump'') of a mine. Basic enemy breaching techniques are compared for the different mine movement concepts. These results are then used in the (Joint Conflict and Tactical Simulation) JCATS tactical model to evaluate minefield effects in a combat situation. The three basecases and the Frogs concept are used against a North Korean mechanized rifle battalion and outcomes are compared. Preliminary results indicate: (1) Possible breaching techniques for the self-healing minefield were proposed and compared through simulation modeling. Of these, the best breaching counter to the self-healing minefield is the ''wide-lane'' breach technique. (2) Several methods for mine movement are tested and the optimal method from this group was selected for use in the modeling. However, continued work is needed on jump criteria; a more sophisticated model may reduce the advantage of the breach counter. (3) The battle scenario used in this study is a very difficult defense for Blue. In the three baseline cases (no mines, AT mines only, and mixed AT/AP minefield), Blue loses. Only in the Frog case does Blue win, and it is a high casualty win.

  13. Self-Healing and Moldable Metallogels as the Recyclable Materials for Selective Dye Adsorption and Separation.

    PubMed

    Karan, Chandan Kumar; Bhattacharjee, Manish

    2016-03-01

    Four multiresponsive and self-sustaining metallogels were synthesized by the reaction of the disodium salt of the ligand carboxymethyl-(3,5-di-tert-butyl-2-hydroxy-benzyl)amino acetic acid with Cd(II) and Zn(II) halides, which were found to show excellent selectivity for dye adsorption and separation, and one of the gels shows a rare self-healing property. PMID:26854670

  14. Electrochemical Sensors Based on Organic Conjugated Polymers

    PubMed Central

    Rahman, Md. Aminur; Kumar, Pankaj; Park, Deog-Su; Shim, Yoon-Bo

    2008-01-01

    Organic conjugated polymers (conducting polymers) have emerged as potential candidates for electrochemical sensors. Due to their straightforward preparation methods, unique properties, and stability in air, conducting polymers have been applied to energy storage, electrochemical devices, memory devices, chemical sensors, and electrocatalysts. Conducting polymers are also known to be compatible with biological molecules in a neutral aqueous solution. Thus, these are extensively used in the fabrication of accurate, fast, and inexpensive devices, such as biosensors and chemical sensors in the medical diagnostic laboratories. Conducting polymer-based electrochemical sensors and biosensors play an important role in the improvement of public health and environment because rapid detection, high sensitivity, small size, and specificity are achievable for environmental monitoring and clinical diagnostics. In this review, we summarized the recent advances in conducting polymer-based electrochemical sensors, which covers chemical sensors (potentiometric, voltammetric, amperometric) and biosensors (enzyme based biosensors, immunosensors, DNA sensors).

  15. Poly(sebacoyl diglyceride) Cross-Linked by Dynamic Hydrogen Bonds: A Self-Healing and Functionalizable Thermoplastic Bioelastomer.

    PubMed

    Chen, Shuo; Bi, Xiaoping; Sun, Lijie; Gao, Jin; Huang, Peng; Fan, Xianqun; You, Zhengwei; Wang, Yadong

    2016-08-17

    Biodegradable and biocompatible elastomers (bioelastomers) could resemble the mechanical properties of extracellular matrix and soft tissues and, thus, are very useful for many biomedical applications. Despite significant advances, tunable bioelastomers with easy processing, facile biofunctionalization, and the ability to withstand a mechanically dynamic environment have remained elusive. Here, we reported new dynamic hydrogen-bond cross-linked PSeD-U bioelastomers possessing the aforementioned features by grafting 2-ureido-4[1H]-pyrimidinones (UPy) units with strong self-complementary quadruple hydrogen bonds to poly(sebacoyl diglyceride) (PSeD), a refined version of a widely used bioelastomer poly(glycerol sebacate) (PGS). PSeD-U polymers exhibited stronger mechanical strength than their counterparts of chemically cross-linked PSeD and tunable elasticity by simply varying the content of UPy units. In addition to the good biocompatibility and biodegradability as seen in PSeD, PSeD-U showed fast self-healing (within 30 min) at mild conditions (60 °C) and could be readily processed at moderate temperature (90-100 °C) or with use of solvent casting at room temperature. Furthermore, the free hydroxyl groups of PSeD-U enabled facile functionalization, which was demonstrated by the modification of PSeD-U film with FITC as a model functional molecule. PMID:27419538

  16. Ionic Modification Turns Commercial Rubber into a Self-Healing Material.

    PubMed

    Das, Amit; Sallat, Aladdin; Böhme, Frank; Suckow, Marcus; Basu, Debdipta; Wiessner, Sven; Stöckelhuber, Klaus Werner; Voit, Brigitte; Heinrich, Gert

    2015-09-23

    Invented by Charles Goodyear, chemical cross-linking of rubbers by sulfur vulcanization is the only method by which modern automobile tires are manufactured. The formation of these cross-linked network structures leads to highly elastic properties, which substantially reduces the viscous properties of these materials. Here, we describe a simple approach to converting commercially available and widely used bromobutyl rubber (BIIR) into a highly elastic material with extraordinary self-healing properties without using conventional cross-linking or vulcanising agents. Transformation of the bromine functionalities of BIIR into ionic imidazolium bromide groups results in the formation of reversible ionic associates that exhibit physical cross-linking ability. The reversibility of the ionic association facilitates the healing processes by temperature- or stress-induced rearrangements, thereby enabling a fully cut sample to retain its original properties after application of the self-healing process. Other mechanical properties, such as the elastic modulus, tensile strength, ductility, and hysteresis loss, were found to be superior to those of conventionally sulfur-cured BIIR. This simple and easy approach to preparing a commercial rubber with self-healing properties offers unique development opportunities in the field of highly engineered materials, such as tires, for which safety, performance, and longer fatigue life are crucial factors. PMID:26332010

  17. Building adaptive self-healing systems within a resource contested environment.

    PubMed

    Phillips, Brian; Blackburn, Mark

    2016-04-01

    Critical Software systems must recover when they experience degradation, either through external actors or internal system failures. There is currently no accepted generic methodology used by the software engineering community to design self-healing systems. Such systems identify when they require healing resources, and then change their own behavior to acquire and utilize these same resources. This study investigates using a design pattern to build such a system. It uses simulated robot tank combat to represent a challenge faced by an adaptive self-healing system. It also investigates how an adaptive system chooses different behaviors balancing its actions between healing activities, movement activities, and combat activities. The results of this study demonstrate how an adaptive self-healing system utilizes behavior selection within a contested environment where other external actors attempt to deny resources to it. It demonstrates how a multi-system architecture inspired by cognitive science its behavior to maximize its ability to both win matches, and survive. This study investigates system characteristics such as how behaviors are organized and how computer memory is utilized. The performance of the adaptive system is compared with the performance of 840 non-adapting systems that compete within this same environment.

  18. Ionic Modification Turns Commercial Rubber into a Self-Healing Material.

    PubMed

    Das, Amit; Sallat, Aladdin; Böhme, Frank; Suckow, Marcus; Basu, Debdipta; Wiessner, Sven; Stöckelhuber, Klaus Werner; Voit, Brigitte; Heinrich, Gert

    2015-09-23

    Invented by Charles Goodyear, chemical cross-linking of rubbers by sulfur vulcanization is the only method by which modern automobile tires are manufactured. The formation of these cross-linked network structures leads to highly elastic properties, which substantially reduces the viscous properties of these materials. Here, we describe a simple approach to converting commercially available and widely used bromobutyl rubber (BIIR) into a highly elastic material with extraordinary self-healing properties without using conventional cross-linking or vulcanising agents. Transformation of the bromine functionalities of BIIR into ionic imidazolium bromide groups results in the formation of reversible ionic associates that exhibit physical cross-linking ability. The reversibility of the ionic association facilitates the healing processes by temperature- or stress-induced rearrangements, thereby enabling a fully cut sample to retain its original properties after application of the self-healing process. Other mechanical properties, such as the elastic modulus, tensile strength, ductility, and hysteresis loss, were found to be superior to those of conventionally sulfur-cured BIIR. This simple and easy approach to preparing a commercial rubber with self-healing properties offers unique development opportunities in the field of highly engineered materials, such as tires, for which safety, performance, and longer fatigue life are crucial factors.

  19. Building adaptive self-healing systems within a resource contested environment.

    PubMed

    Phillips, Brian; Blackburn, Mark

    2016-04-01

    Critical Software systems must recover when they experience degradation, either through external actors or internal system failures. There is currently no accepted generic methodology used by the software engineering community to design self-healing systems. Such systems identify when they require healing resources, and then change their own behavior to acquire and utilize these same resources. This study investigates using a design pattern to build such a system. It uses simulated robot tank combat to represent a challenge faced by an adaptive self-healing system. It also investigates how an adaptive system chooses different behaviors balancing its actions between healing activities, movement activities, and combat activities. The results of this study demonstrate how an adaptive self-healing system utilizes behavior selection within a contested environment where other external actors attempt to deny resources to it. It demonstrates how a multi-system architecture inspired by cognitive science its behavior to maximize its ability to both win matches, and survive. This study investigates system characteristics such as how behaviors are organized and how computer memory is utilized. The performance of the adaptive system is compared with the performance of 840 non-adapting systems that compete within this same environment. PMID:27441273

  20. Self-healing metal wire using electric field trapping of metal nanoparticles

    NASA Astrophysics Data System (ADS)

    Koshi, Tomoya; Iwase, Eiji

    2015-06-01

    We propose a self-healing metal wire using electric field trapping of gold nanoparticles by a dielectrophoresis force. A cracked gold wire can retrieve its conductivity through the self-healing function. In this paper, we examine the healing voltage causing the electric field trapping and determine the healing time, which is relevant to future device applications. First, the forces acting on a nanoparticle are analyzed and a theoretical healing voltage curve is calculated. Then, gold wires with 200- to 1,600-nm-wide cracks are fabricated on glass substrate and the self-healing function is verified through healing experiments. As a result, gold wires with cracks of up to 1,200 nm in width are successfully healed by applying less than ∼2.5 V (on average), and the experimental results correspond almost exactly with the calculated healing voltage curve. The average healing times are 10 to 285 s for 200- to 1,200-nm-wide cracks. Through scanning electron microscope analysis after the healing experiments, we confirm that the cracks are healed by assembled nanoparticles.

  1. Dual-responsive two-component supramolecular gels for self-healing materials and oil spill recovery.

    PubMed

    Yan, Liwei; Li, Guangzhe; Ye, Zhongbin; Tian, Feng; Zhang, Shihong

    2014-12-01

    Dual-responsive two-component supramolecular gels with self-healing properties were prepared using tetrazolyl derivatives and alkylamine, and were also applied in selectively congealing crude oil from an oil-water mixture.

  2. Morphing Metal and Elastomer Bicontinuous Foams for Reversible Stiffness, Shape Memory, and Self-Healing Soft Machines.

    PubMed

    Van Meerbeek, Ilse M; Mac Murray, Benjamin C; Kim, Jae Woo; Robinson, Sanlin S; Zou, Perry X; Silberstein, Meredith N; Shepherd, Robert F

    2016-04-13

    A metal-elastomer-foam composite that varies in stiffness, that can change shape and store shape memory, that self-heals, and that welds into monolithic structures from smaller components is presented. PMID:26872152

  3. Electrospun N-Substituted Polyurethane Membranes with Self-Healing Ability for Self-Cleaning and Oil/Water Separation.

    PubMed

    Fang, Wenyuan; Liu, Libin; Li, Ting; Dang, Zhao; Qiao, Congde; Xu, Jinku; Wang, Yanyan

    2016-01-18

    Membranes with special functionalities, such as self-cleaning, especially those for oil/water separation, have attracted much attention due to their wide applications. However, they are difficult to recycle and reuse after being damaged. Herein, we put forward a new N-substituted polyurethane membrane concept with self-healing ability to address this challenge. The membrane obtained by electrospinning has a self-cleaning surface with an excellent self-healing ability. Importantly, by tuning the membrane composition, the membrane exhibits different wettability for effective separation of oil/water mixtures and water-in-oil emulsions, whilst still displaying a self-healing ability and durability against damage. To the best of our knowledge, this is the first report to demonstrate a self-healing membrane for oil/water separation, which provides the fundamental research for the development of advanced oil/water separation materials.

  4. Polymer based nanocomposites with tailorable optical properties

    NASA Astrophysics Data System (ADS)

    Colombo, Annalisa; Simonutti, Roberto

    2014-09-01

    Transparent polymers are extensively used in everyday life, from windows to computer displays, from food packaging to lenses. A possible approach for modulating their optical properties (refractive index, transparency, color and luminescence) is to change the chemical structure of the polymer, however this option is in many cases economically prohibitive. Our approach, instead, relies in the use of standard polymers with the supplement of specific nanostructured additives able to tune the final property of the material. Among others, the cases of luminescent solar concentrators based on poly(methylmethacrylate) containing luminescent quantum dots and highly transparent polymer nanocomposites with high refractive index will be presented.

  5. Dynamic Ordering and Phase Segregation in Hydrogen-Bonded Polymers.

    PubMed

    Chen, Senbin; Binder, Wolfgang H

    2016-07-19

    Hydrogen bonds (H-bonds) constitute highly relevant structural units of molecular self-assembly. They bridge biological and synthetic sciences, implementing dynamic properties into materials and molecules, not achieved via purely covalent bonds. Phase segregation on the other hand represents another important assembly principle, responsible for, e.g., cell compartimentation, membrane-formation, and microphase segregation in polymers. Yet, despite the expanding elegant synthetic strategies of supramolecular polymers, the investigation of phase behavior of macromolecules driven by H-bonding forces still remains in its infancy. Compared to phase segregation arising from covalently linked block copolymers, the generation of phase segregated nanostructures via supramolecular polymers facilitates the design of novel functional materials, such as those with stimuli-responsive, self-healing, and erasable-material properties. We here discuss the phase segregation of H-bonding polymers in both the solution and solid state, wherein the molecular recognition elements are based on multiple H-bonding moieties, such as thymine/2,6-diamino-pyridine (THY/DAP), thymine/diamino triazine (THY/DAT), and barbiturate/Hamilton wedge (Ba/HW) elements. The specific aggregation of a series of different H-bonding polymers in solution, both linear and dendritic polymers, bearing heterocomplementary H-bonding moieties are described, in particular focusing on the issue of phase segregation. The exploitation of H-bonded supramolecular dendrons with segregating polymer chains leads to the formation of three-phase segregated hierarchical micelles in solution, purely linking the components via H-bonds, in turn displaying a versatile spectrum of segregated morphologies. We also focus on segregation effects of H-bonded amorphous and crystalline polymers: thus the formation of nanostructures, such as disordered micelles and well-ordered body centered cubic (BCC) packed spheres from telechelic polymers

  6. Dynamic Ordering and Phase Segregation in Hydrogen-Bonded Polymers.

    PubMed

    Chen, Senbin; Binder, Wolfgang H

    2016-07-19

    Hydrogen bonds (H-bonds) constitute highly relevant structural units of molecular self-assembly. They bridge biological and synthetic sciences, implementing dynamic properties into materials and molecules, not achieved via purely covalent bonds. Phase segregation on the other hand represents another important assembly principle, responsible for, e.g., cell compartimentation, membrane-formation, and microphase segregation in polymers. Yet, despite the expanding elegant synthetic strategies of supramolecular polymers, the investigation of phase behavior of macromolecules driven by H-bonding forces still remains in its infancy. Compared to phase segregation arising from covalently linked block copolymers, the generation of phase segregated nanostructures via supramolecular polymers facilitates the design of novel functional materials, such as those with stimuli-responsive, self-healing, and erasable-material properties. We here discuss the phase segregation of H-bonding polymers in both the solution and solid state, wherein the molecular recognition elements are based on multiple H-bonding moieties, such as thymine/2,6-diamino-pyridine (THY/DAP), thymine/diamino triazine (THY/DAT), and barbiturate/Hamilton wedge (Ba/HW) elements. The specific aggregation of a series of different H-bonding polymers in solution, both linear and dendritic polymers, bearing heterocomplementary H-bonding moieties are described, in particular focusing on the issue of phase segregation. The exploitation of H-bonded supramolecular dendrons with segregating polymer chains leads to the formation of three-phase segregated hierarchical micelles in solution, purely linking the components via H-bonds, in turn displaying a versatile spectrum of segregated morphologies. We also focus on segregation effects of H-bonded amorphous and crystalline polymers: thus the formation of nanostructures, such as disordered micelles and well-ordered body centered cubic (BCC) packed spheres from telechelic polymers

  7. Behavior of Aging, Micro-Void, and Self-Healing of Glass/Ceramic Materials and Its Effect on Mechanical Properties

    SciTech Connect

    Liu, Wenning N.; Sun, Xin; Khaleel, Mohammad A.

    2011-06-30

    This chapter first describes tests to investigate the temporal evolution of the volume fraction of ceramic phases, the evolution of micro-damage, and the self-healing behavior of the glass ceramic sealant used in SOFCs, then a phenomenological model based on mechanical analogs is developed to describe the temperature dependent Young’s modulus of glass ceramic seal materials. It was found that after the initial sintering process, further crystallization of the glass ceramic sealant does not stop, but slows down and reduces the residual glass content while boosting the ceramic crystalline content. Under the long-term operating environment, distinct fibrous and needle-like crystals in the amorphous phase disappeared, and smeared/diffused phase boundaries between the glass phase and ceramic phase were observed. Meanwhile, the micro-damage was induced by the cooling-down process from the operating temperature to the room temperature, which can potentially degrade the mechanical properties of the glass/ceramic sealant. The glass/ceramic sealant self-healed upon reheating to the SOFC operating temperature, which can restore the mechanical performance of the glass/ceramic sealant. The phenomenological model developed here includes the effects of continuing aging and devitrification on the ceramic phase volume fraction and the resulted mechanical properties of glass ceramic seal material are considered. The effects of micro-voids and self-healing are also considered using a continuum damage mechanics (CDM) model. The formulation is for glass/ceramic seal in general, and it can be further developed to account for effects of various processing parameters. This model was applied to G18, and the temperature-dependent experimental measurements were used to calibrate the modeling parameters and to validate the model prediction.

  8. Monitoring of self-healing phenomena towards enhanced sustainability of historic mortars

    NASA Astrophysics Data System (ADS)

    Amenta, M.; Karatasios, I.; Maravelaki, P.; Kilikoglou, V.

    2016-05-01

    Mortars are known for their ability to heal their defects in an autogenic way. This phenomenon is expressed by the filling of microcracks by secondary products, restoring or enhancing the material's performance. Parameterization of self-healing phenomenon could be a key factor for the enhanced sustainability of these materials in terms of reduced repair cost and consumption of natural raw materials and thus reduced environmental fingerprint. The fact that this phenomenon takes place autogenously suggests that the material can self-repair its defects, without external intervention, thus leading to a prolonged life cycle. In the present study, the autogenic self-healing phenomenon was studied in natural hydraulic lime mortars, considering aspects of curing time before initial cracking, duration and conditions of the healing period. Furthermore, strength recovery due to autogenic self-healing was measured under high humidity conditions, and thermo-gravimetric analysis (DTA/TG) was performed in all specimens in order to quantitatively assess the available unreacted components in the binder at all ages. Regarding the microstructure of the healing phases, the main products formed during healing consist of calcite and various C-S-H/C-A-H phases. Depending on the parameters mentioned above, there is a wide diversity in the intensity, typology and topography of the secondary phases inside the cracks. The main differences discussed were observed between specimens cracked at very early age and those damaged after 30 days of curing. Similarly, the mechanical properties of the crack-healed specimens were associated with the above findings and especially with the available each-time amount of lime, determined by thermo-gravimetric analysis.

  9. Electromigration in Gold Films on Flexible Polyimide Substrates as a Self-healing Mechanism

    PubMed Central

    Putz, Barbara; Glushko, Oleksandr; Cordill, Megan J.

    2016-01-01

    The study of electromigration (EM) in metallisations for flexible thin film systems has not been a major concern due to low applied current densities in today's flexible electronic devices. However, the trend towards smaller and more powerful devices demands increasing current densities for future applications, making EM a reliability matter. This work investigates EM in 50 nm Au thin films with a 10 nm Cr adhesion layer on a flexible polyimide substrate at high current densities. Results indicate that EM does occur and could be used as a self-healing mechanism for flexible electronics. PMID:27158564

  10. Scanning electron microscopy of the collodion membrane from a self-healing collodion baby*

    PubMed Central

    de Almeida Jr., Hiram Larangeira; Isaacsson, Henrique; Guarenti, Isabelle Maffei; Silva, Ricardo Marques e; de Castro, Luis Antônio Suita

    2015-01-01

    Abstract Self-healing collodion baby is a well-established subtype of this condition. We examined a male newborn, who was covered by a collodion membrane. The shed membrane was examined with scanning electron microscopy. The outer surface showed a very compact keratin without the normal elimination of corneocytes. The lateral view of the specimen revealed a very thick, horny layer. The inner surface showed the structure of lower corneocytes with polygonal contour. With higher magnifications villous projections were seen in the cell membrane. PMID:26375232

  11. A Note on an Improved Self-Healing Group Key Distribution Scheme

    PubMed Central

    Guo, Hua; Zheng, Yandong; Wang, Biao; Li, Zhoujun

    2015-01-01

    In 2014, Chen et al. proposed a one-way hash self-healing group key distribution scheme for resource-constrained wireless networks in the journal of Sensors (14(14):24358-24380, doi: 10.3390/s141224358). They asserted that their Scheme 2 achieves mt-revocation capability, mt-wise forward secrecy, any-wise backward secrecy and has mt-wise collusion attack resistance capability. Unfortunately, this paper pointed out that their scheme does not satisfy the forward security, mt-revocation capability and mt-wise collusion attack resistance capability. PMID:26426018

  12. Polymer-based electrocaloric cooling devices

    DOEpatents

    Zhang, Qiming; Lu, Sheng-Guo; Li, Xinyu; Gorny, Lee; Cheng, Jiping; Neese, Bret P; Chu, Baojin

    2014-10-28

    Cooling devices (i.e., refrigerators or heat pumps) based on polymers which exhibit a temperature change upon application or removal of an electrical field or voltage, (e.g., fluoropolymers or crosslinked fluoropolymers that exhibit electrocaloric effect).

  13. Study of Geometric Stability and Structural Integrity of Self-Healing Glass Seal System Used in Solid Oxide Fuel Cells

    SciTech Connect

    Liu, Wenning N.; Sun, Xin; Khaleel, Mohammad A.

    2011-02-15

    A self-healing glass seal has the potential of restoring its mechanical properties upon being reheated to SOFC stack operating temperature, even when it has experienced some cooling induced damage/cracking at room temperature. Such a self-healing feature is desirable for achieving high seal reliability during thermal cycling. On the other hand, self-healing glass is also characterized by its low mechanical stiffness and high creep rate at the typical operating temperature of SOFCs. Therefore, geometry stability and structural integrity of the glass seal system becomes critical to its successful application in SOFCs. In this paper, the geometry stability of the self-healing glass and the influence of various interfacial conditions of ceramic stoppers with the PEN, IC, and glass seal on the structural integrity of the glass seal during the operating and cooling down processes are studied using finite element analyses. For this purpose, the test cell used in the leakage tests for compliant glass seals conducted at PNNL is taken as the initial modeling geometry. The effect of the ceramic stopper on the geometry stability of the self-healing glass sealants is studied first. Two interfacial conditions of the ceramic stopper and glass seals, i.e., bonded (strong) or un-bonded (weak), are considered. Then the influences of interfacial strengths at various interfaces, i.e., stopper/glass, stopper/PEN, as well as stopper/IC plate, on the geometry stability and reliability of glass during the operating and cooling processes are examined.

  14. Damage detection monitoring applications in self-healing concrete structures using embedded piezoelectric transducers and recovery

    NASA Astrophysics Data System (ADS)

    Karaiskos, G.; Tsangouri, E.; Aggelis, D. G.; Deraemaeker, A.; Van Hemelrijck, D.

    2015-07-01

    The ageing, operational and ambient loadings have a great impact in the operational and maintenance cost of concrete structures. Their service life prolongation is of utmost importance and this can be efficiently achieved by using reliable and low-cost monitoring and self-healing techniques. In the present study, the ultrasonic pulse velocity (UPV) method using embedded small-size and low-cost piezoelectric PZT (lead zirconate titanate) ceramic transducers in concrete with self-healing properties is implemented for monitoring not only the setting and hardening phases of concrete since casting time, but also for the detection of damage initiation, propagation and recovery of integrity after healing. A couple of small-scale notched unreinforced concrete beams are subjected to mode-I fracture through three-point bending tests. After a 24-hour healing agent curing period, the beams are reloaded using the same loading scenario. The results demonstrate the excellent performance of the proposed monitoring technique during the hydration, damage generation and recovery periods.

  15. Notch insensitive and self-healing PNIPAm-PAM-clay nanocomposite hydrogels.

    PubMed

    Wang, Tao; Zheng, Shudian; Sun, Weixiang; Liu, Xinxing; Fu, Shiyu; Tong, Zhen

    2014-05-21

    In the present work, hydrophilic monomer acrylamide (AM) was copolymerized with N-isopropylacrylamide (NIPAm) in an aqueous hectorite clay suspension to prepare PNIPAm-PAM-clay nanocomposite hydrogels (NC gels). With increasing AM content, the elongation at break of the copolymerized NC gels increased but the strength as well as the hysteresis during the loading-unloading cycle decreased, showing faster relaxation due to the more hydrophilic copolymer chains with the AM segments. The elongation at break of the copolymerized NC gels was independent of the notch length and notch type, while the fracture energy was greatly increased to 3000-5000 J m(-2) from 700 J m(-2) for the pure PNIPAm NC gels. The copolymer chains resulted in this notch insensitivity by easily dispersing the stress concentration at the notch tip through disorientation of the copolymer chains and clay platelets. The copolymerized NC gels also exhibited excellent self-healing capability; the cut surfaces were connected together by simply keeping in contact for a period of time (about 4 days at 20 °C). This self-healing was accelerated by increasing the treatment temperature (about 4 h at 80 °C). PMID:24652073

  16. A continuum thermo-inelastic model for damage and healing in self-healing glass materials

    SciTech Connect

    Xu, Wei; Sun, Xin; Koeppel, Brian J.; Zbib, Hussein M.

    2014-07-08

    Self-healing glass, a recent advancement in the class of smart sealing materials, has attracted great attention from both research and industrial communities because of its unique capability of repairing itself at elevated temperatures. However, further development and optimization of this material rely on a more fundamental and thorough understanding of its essential thermo-mechanical response characteristics, which is also pivotal in predicting the coupling and interactions between the nonlinear stress and temperature dependent damage and healing behaviors. In the current study, a continuum three-dimensional thermo-inelastic damage-healing constitutive framework has been developed for the compliant self-healing glass material. The important feature of the present model is that various phenomena governing the mechanical degradation and recovery process, i.e. the nucleation, growth, and healing of the cracks and pores, are described with distinct mechanism-driven kinetics, where the healing constitutive relations are propagated from lower-length scale simulations. The proposed formulations are implemented into finite element analyses and the effects of various loading conditions and material properties on the material’s mechanical resistance are investigated.

  17. Simple and efficient self-healing strategy for damaged complex networks

    NASA Astrophysics Data System (ADS)

    Gallos, Lazaros K.; Fefferman, Nina H.

    2015-11-01

    The process of destroying a complex network through node removal has been the subject of extensive interest and research. Node loss typically leaves the network disintegrated into many small and isolated clusters. Here we show that these clusters typically remain close to each other and we suggest a simple algorithm that is able to reverse the inflicted damage by restoring the network's functionality. After damage, each node decides independently whether to create a new link depending on the fraction of neighbors it has lost. In addition to relying only on local information, where nodes do not need knowledge of the global network status, we impose the additional constraint that new links should be as short as possible (i.e., that the new edge completes a shortest possible new cycle). We demonstrate that this self-healing method operates very efficiently, both in model and real networks. For example, after removing the most connected airports in the USA, the self-healing algorithm rejoined almost 90% of the surviving airports.

  18. The resilient hybrid fiber sensor network with self-healing function

    NASA Astrophysics Data System (ADS)

    Xu, Shibo; Liu, Tiegen; Ge, Chunfeng; Chen, Qinnan; Zhang, Hongxia

    2015-03-01

    This paper presents a novel resilient fiber sensor network (FSN) with multi-ring architecture, which could interconnect various kinds of fiber sensors responsible for more than one measurands. We explain how the intelligent control system provides sensors with self-healing function meanwhile sensors are working properly, besides each fiber in FSN is under real-time monitoring. We explain the software process and emergency mechanism to respond failures or other circumstances. To improve the efficiency in the use of limited spectrum resources in some situations, we have two different structures to distribute the light sources rationally. Then, we propose a hybrid sensor working in FSN which is a combination of a distributed sensor and a FBG (Fiber Bragg Grating) array fused in a common fiber sensing temperature and vibrations simultaneously with neglectable crosstalk to each other. By making a failure to a working fiber in experiment, the feasibility and effectiveness of the network with a hybrid sensor has been demonstrated, hybrid sensors could not only work as designed but also survive from destructive failures with the help of resilient network and smart and quick self-healing actions. The network has improved the viability of the fiber sensors and diversity of measurands.

  19. The resilient hybrid fiber sensor network with self-healing function.

    PubMed

    Xu, Shibo; Liu, Tiegen; Ge, Chunfeng; Chen, Qinnan; Zhang, Hongxia

    2015-03-01

    This paper presents a novel resilient fiber sensor network (FSN) with multi-ring architecture, which could interconnect various kinds of fiber sensors responsible for more than one measurands. We explain how the intelligent control system provides sensors with self-healing function meanwhile sensors are working properly, besides each fiber in FSN is under real-time monitoring. We explain the software process and emergency mechanism to respond failures or other circumstances. To improve the efficiency in the use of limited spectrum resources in some situations, we have two different structures to distribute the light sources rationally. Then, we propose a hybrid sensor working in FSN which is a combination of a distributed sensor and a FBG (Fiber Bragg Grating) array fused in a common fiber sensing temperature and vibrations simultaneously with neglectable crosstalk to each other. By making a failure to a working fiber in experiment, the feasibility and effectiveness of the network with a hybrid sensor has been demonstrated, hybrid sensors could not only work as designed but also survive from destructive failures with the help of resilient network and smart and quick self-healing actions. The network has improved the viability of the fiber sensors and diversity of measurands.

  20. The resilient hybrid fiber sensor network with self-healing function

    SciTech Connect

    Xu, Shibo Liu, Tiegen; Ge, Chunfeng; Chen, Qinnan; Zhang, Hongxia

    2015-03-15

    This paper presents a novel resilient fiber sensor network (FSN) with multi-ring architecture, which could interconnect various kinds of fiber sensors responsible for more than one measurands. We explain how the intelligent control system provides sensors with self-healing function meanwhile sensors are working properly, besides each fiber in FSN is under real-time monitoring. We explain the software process and emergency mechanism to respond failures or other circumstances. To improve the efficiency in the use of limited spectrum resources in some situations, we have two different structures to distribute the light sources rationally. Then, we propose a hybrid sensor working in FSN which is a combination of a distributed sensor and a FBG (Fiber Bragg Grating) array fused in a common fiber sensing temperature and vibrations simultaneously with neglectable crosstalk to each other. By making a failure to a working fiber in experiment, the feasibility and effectiveness of the network with a hybrid sensor has been demonstrated, hybrid sensors could not only work as designed but also survive from destructive failures with the help of resilient network and smart and quick self-healing actions. The network has improved the viability of the fiber sensors and diversity of measurands.

  1. Preparation of polyurea/melamine formaldehyde double-layered self-healing microcapsules and investigation on core fraction.

    PubMed

    Ming, Yaoqiang; Hu, Jianfeng; Xing, Junheng; Wu, Minghua; Qu, Jinqing

    2016-06-01

    Moisture curing type self-healing microcapsules become more attractive, while instability of active core material crippled the efficiency of self-healing behaviour. Polyurea (PU)/melamine formaldehyde (MF) double-layered self-healing microcapsules containing isophorone diisocyanate (IPDI) core with high and stable core fraction were prepared. The structure, morphology, particle size and distribution were studied with Fourier transform infra-red spectroscopy, optical microscopy, scanning electron microscopy and Mastersizer 3000. The influences of process conditions were investigated to uncover the principle of core fraction and morphology of microcapsules. The core fraction of microcapsules was reduced with the increase of ageing time, and microcapsules prepared with ice-bath, polyetheramine (PEA) and prepolymer of melamine formaldehyde (P-MF) had higher core fraction and better morphology. PEA D230 and 1500 rpm agitation rate were chosen according to optimised trade-offs in the core fraction and morphology of the microcapsules.

  2. Preparation of polyurea/melamine formaldehyde double-layered self-healing microcapsules and investigation on core fraction.

    PubMed

    Ming, Yaoqiang; Hu, Jianfeng; Xing, Junheng; Wu, Minghua; Qu, Jinqing

    2016-06-01

    Moisture curing type self-healing microcapsules become more attractive, while instability of active core material crippled the efficiency of self-healing behaviour. Polyurea (PU)/melamine formaldehyde (MF) double-layered self-healing microcapsules containing isophorone diisocyanate (IPDI) core with high and stable core fraction were prepared. The structure, morphology, particle size and distribution were studied with Fourier transform infra-red spectroscopy, optical microscopy, scanning electron microscopy and Mastersizer 3000. The influences of process conditions were investigated to uncover the principle of core fraction and morphology of microcapsules. The core fraction of microcapsules was reduced with the increase of ageing time, and microcapsules prepared with ice-bath, polyetheramine (PEA) and prepolymer of melamine formaldehyde (P-MF) had higher core fraction and better morphology. PEA D230 and 1500 rpm agitation rate were chosen according to optimised trade-offs in the core fraction and morphology of the microcapsules. PMID:27145990

  3. Fracture Toughness of Carbon Fiber Composites Containing Various Fiber Sizings and a Puncture Self-Healing Thermoplastic Matrix

    NASA Technical Reports Server (NTRS)

    Cano, Roberto J.; Grimsley, Brian W.; Ratcliffe, James G.; Gordon, Keith L.; Smith, Joseph G.; Siochi, Emilie J.

    2015-01-01

    Ongoing efforts at NASA Langley Research Center (LaRC) have resulted in the identification of several commercially available thermoplastic resin systems which self-heal after ballistic impact and through penetration. One of these resins, polybutylene graft copolymer (PBg), was selected as a matrix for processing with unsized carbon fibers to fabricate reinforced composites for further evaluation. During process development, data from thermo-physical analyses was utilized to determine a processing cycle to fabricate laminate panels, which were analyzed by photo microscopy and acid digestion. The process cycle was further optimized based on these results to fabricate panels for mechanical property characterization. The results of the processing development effort of this composite material, as well as the results of the mechanical property characterization, indicated that bonding between the fiber and PBg was not adequate. Therefore, three sizings were investigated in this work to assess their potential to improve fiber/matrix bonding compared to previously tested unsized IM7 fiber. Unidirectional prepreg was made at NASA LaRC from three sized carbon fibers and utilized to fabricate test coupons that were tested in double cantilever beam configurations to determine GIc fracture toughness.

  4. The effect of filler parameters on the healing of thermal conductivity and mechanical properties of a thermal interface material based on a self-healable organic–inorganic polymer matrix

    NASA Astrophysics Data System (ADS)

    Zhong, Nan; Garcia, Santiago J.; van der Zwaag, Sybrand

    2016-08-01

    Thermal interface materials (TIMs) are widely used in all kinds of electronic devices to handle the heat dissipation and the mechanical anchoring of the heat producing component. The aging of TIMs may lead to delamination and internal crack formation causing a loss of heat transfer and mechanical integrity both leading to premature device failure. In the present work, a novel TIM system based on a self-healing organic–inorganic polymer matrix filled with spherical glass beads is presented which is capable of healing both the thermal conductivity and the mechanical properties upon thermal activation. The effect of particle volume concentration (PVC) and particle size on tensile strength and thermal conductivity healing behavior is investigated. The results show that a higher PVC increases the mechanical property but decreases mechanical healing. For the same PVC, bigger particles lead to lower mechanical properties but higher thermal conductivities and higher mechanical healing efficiencies.

  5. The effect of filler parameters on the healing of thermal conductivity and mechanical properties of a thermal interface material based on a self-healable organic-inorganic polymer matrix

    NASA Astrophysics Data System (ADS)

    Zhong, Nan; Garcia, Santiago J.; van der Zwaag, Sybrand

    2016-08-01

    Thermal interface materials (TIMs) are widely used in all kinds of electronic devices to handle the heat dissipation and the mechanical anchoring of the heat producing component. The aging of TIMs may lead to delamination and internal crack formation causing a loss of heat transfer and mechanical integrity both leading to premature device failure. In the present work, a novel TIM system based on a self-healing organic-inorganic polymer matrix filled with spherical glass beads is presented which is capable of healing both the thermal conductivity and the mechanical properties upon thermal activation. The effect of particle volume concentration (PVC) and particle size on tensile strength and thermal conductivity healing behavior is investigated. The results show that a higher PVC increases the mechanical property but decreases mechanical healing. For the same PVC, bigger particles lead to lower mechanical properties but higher thermal conductivities and higher mechanical healing efficiencies.

  6. Evidence for and implications of self-healing pulses of slip in earthquake rupture

    USGS Publications Warehouse

    Heaton, T.H.

    1990-01-01

    Dislocation time histories of models derived from waveforms of seven earthquakes are discussed. In each model, dislocation rise times (the duration of slip for a given point on the fault) are found to be short compared to the overall duration of the earthquake (??? 10%). However, in many crack-like numerical models of dynamic rupture, the slip duration at a given point is comparable to the overall duration of the rupture; i.e. slip at a given point continues until information is received that the rupture has stopped propagating. Alternative explanations for the discrepancy between the short slip durations used to model waveforms and the long slip durations inferred from dynamic crack models are: (1) the dislocation models are unable to resolve the relatively slow parts of earthquake slip and have seriously underestimated the dislocations for these earthquakes; (2) earthquakes are composed of a sequence of small-dimension (short duration) events that are separated by locked regions (barriers); (3) rupture occurs in a narrow self-healing pulse of slip that travels along the fault surface. Evidence is discussed that suggests that slip durations are indeed short and that the self-healing slip-pulse model is the most appropriate explanation. A qualitative model is presented that produces self-healing slip pulses. The key feature of the model is the assumption that friction on the fault surface is inversely related to the local slip velocity. The model has the following features: high static strength of materials (kilobar range), low static stress drops (in the range of tens of bars), and relatively low frictional stress during slip (less than several hundreds of bars). It is suggested that the reason that the average dislocation scales with fault length is because large-amplitude slip pulses are difficult to stop and hence tend to propagate large distances. This model may explain why seismicity and ambient stress are low along fault segments that have experienced large

  7. Mechanisms of Hydrocarbon Based Polymer Etch

    NASA Astrophysics Data System (ADS)

    Lane, Barton; Ventzek, Peter; Matsukuma, Masaaki; Suzuki, Ayuta; Koshiishi, Akira

    2015-09-01

    Dry etch of hydrocarbon based polymers is important for semiconductor device manufacturing. The etch mechanisms for oxygen rich plasma etch of hydrocarbon based polymers has been studied but the mechanism for lean chemistries has received little attention. We report on an experimental and analytic study of the mechanism for etching of a hydrocarbon based polymer using an Ar/O2 chemistry in a single frequency 13.56 MHz test bed. The experimental study employs an analysis of transients from sequential oxidation and Ar sputtering steps using OES and surface analytics to constrain conceptual models for the etch mechanism. The conceptual model is consistent with observations from MD studies and surface analysis performed by Vegh et al. and Oehrlein et al. and other similar studies. Parameters of the model are fit using published data and the experimentally observed time scales.

  8. Polymer containing functional end groups is base for new polymers

    NASA Technical Reports Server (NTRS)

    Hirshfield, S. M.

    1971-01-01

    Butadiene is polymerized with lithium-p-lithiophenoxide to produce linear polymer containing oxy-lithium group at one end and active carbon-lithium group at other end. Living polymers represent new approach to preparation of difunctional polymers in which structural features, molecular weight, type and number of end groups are controlled.

  9. Wave-optics description of self-healing mechanism in Bessel beams.

    PubMed

    Aiello, Andrea; Agarwal, Girish S

    2014-12-15

    Bessel beams' great importance in optics lies in that these propagate without spreading and can reconstruct themselves behind an obstruction placed across their path. However, a rigorous wave-optics explanation of the latter property is missing. In this work, we study the reconstruction mechanism by means of a wave-optics description. We obtain expressions for the minimum distance beyond the obstruction at which the beam reconstructs itself, which are in close agreement with the traditional one determined from geometrical optics. Our results show that the physics underlying the self-healing mechanism can be entirely explained in terms of the propagation of plane waves with radial wave vectors lying on a ring.

  10. Robust, Self-Healing Superhydrophobic Fabrics Prepared by One-Step Coating of PDMS and Octadecylamine

    NASA Astrophysics Data System (ADS)

    Xue, Chao-Hua; Bai, Xue; Jia, Shun-Tian

    2016-06-01

    A robust, self-healing superhydrophobic poly(ethylene terephthalate) (PET) fabric was fabricated by a convenient solution-dipping method using an easily available material system consisting of polydimethylsiloxane and octadecylamine (ODA). The surface roughness was formed by self-roughening of ODA coating on PET fibers without any lithography steps or adding any nanomaterials. The fabric coating was durable to withstand 120 cycles of laundry and 5000 cycles of abrasion without apparently changing the superhydrophobicity. More interestingly, the fabric can restore its super liquid-repellent property by 72 h at room temperature even after 20000 cycles of abrasion. Meanwhile, after being damaged chemically, the fabric can restore its superhydrophobicity automatically in 12 h at room temperature or by a short-time heating treatment. We envision that this simple but effective coating system may lead to the development of robust protective clothing for various applications.

  11. Robust, Self-Healing Superhydrophobic Fabrics Prepared by One-Step Coating of PDMS and Octadecylamine

    PubMed Central

    Xue, Chao-Hua; Bai, Xue; Jia, Shun-Tian

    2016-01-01

    A robust, self-healing superhydrophobic poly(ethylene terephthalate) (PET) fabric was fabricated by a convenient solution-dipping method using an easily available material system consisting of polydimethylsiloxane and octadecylamine (ODA). The surface roughness was formed by self-roughening of ODA coating on PET fibers without any lithography steps or adding any nanomaterials. The fabric coating was durable to withstand 120 cycles of laundry and 5000 cycles of abrasion without apparently changing the superhydrophobicity. More interestingly, the fabric can restore its super liquid-repellent property by 72 h at room temperature even after 20000 cycles of abrasion. Meanwhile, after being damaged chemically, the fabric can restore its superhydrophobicity automatically in 12 h at room temperature or by a short-time heating treatment. We envision that this simple but effective coating system may lead to the development of robust protective clothing for various applications. PMID:27264995

  12. Self healing of open circuit faults: With active re-configurability and mimicry of synaptic plasticity

    NASA Astrophysics Data System (ADS)

    Yaswant, Vaddi; Kumar, Amit; Sambandan, Sanjiv

    2016-07-01

    We discuss the self-repair of open faults in circuits using electrically conductive particles dispersed in an insulating fluid. The repair is triggered by the electric field developed across the open circuit in a current carrying interconnect and results in the formation of a bridge of particles across the gap. We illustrate and model the dynamics of the resistance of the self-healed route, Rb, in low field conditions. Furthermore, active control of Rb and active re-wiring are also demonstrated. Considering Rb to be akin to weights between nodes, the formation and re-wiring of routes and the control of Rb mimic synaptic plasticity in biological systems and open interesting possibilities for computing.

  13. Fabrication of non-modified metallic superhydrophobic surfaces with temperature insensitivity and self-healing ability

    NASA Astrophysics Data System (ADS)

    Zhang, Wenwen; Wang, Shanlin; Yu, Xinquan; Zhang, Youfa

    2016-07-01

    Metallic hierarchical texture was prepared by nickel-cobalt electro-deposition and subsequent replacement reaction to coat silver. Due to energetically favorable hydrocarbon adsorption on the silver film, contact angle of the surface increased gradually over time after exposure to laboratory air. The substrate became superhydrophobic after three days to aqueous droplets with various pH values. It was found that the surface remained stable after exposing to extreme temperatures in the wide range from -196 °C to 200 °C. Importantly, self-healing of superhydrophobicity can be easily accomplished and repeated in an ambient environment while hydrocarbon desorption occurred under high temperature. Furthermore, this approach can be easily applied to other conductive substrates.

  14. Adatom complexes and self-healing mechanisms on graphene and single-wall carbon nanotubes

    SciTech Connect

    Tsetseris, Leonidas; Pantelides, Sokrates T

    2009-01-01

    Point defects play a role in the functionalization, chemical activation, carrier transport, and nano-engineering of graphitic systems. Here, we use first-principles calculations to describe several processes that alter the properties of graphene and single-wall carbon nanotubes (SWCNTs) in the presence of self-interstitials (SI's). We find that, while two or four SI's are stabilized in hillock-like structures that stay idle unless the system is heated to very high temperatures, clustering of three C adatoms leads to the formation of mobile protrusions on graphene and large enough SWCNTs. For different SI concentrations and SWCNT size, the interplay between mobile and immobile species may favor one of the two competing processes, self-healing or formation of adatom superstructures.

  15. Robust, Self-Healing Superhydrophobic Fabrics Prepared by One-Step Coating of PDMS and Octadecylamine.

    PubMed

    Xue, Chao-Hua; Bai, Xue; Jia, Shun-Tian

    2016-01-01

    A robust, self-healing superhydrophobic poly(ethylene terephthalate) (PET) fabric was fabricated by a convenient solution-dipping method using an easily available material system consisting of polydimethylsiloxane and octadecylamine (ODA). The surface roughness was formed by self-roughening of ODA coating on PET fibers without any lithography steps or adding any nanomaterials. The fabric coating was durable to withstand 120 cycles of laundry and 5000 cycles of abrasion without apparently changing the superhydrophobicity. More interestingly, the fabric can restore its super liquid-repellent property by 72 h at room temperature even after 20000 cycles of abrasion. Meanwhile, after being damaged chemically, the fabric can restore its superhydrophobicity automatically in 12 h at room temperature or by a short-time heating treatment. We envision that this simple but effective coating system may lead to the development of robust protective clothing for various applications.

  16. Microscopic observations of self-healing products in calcareous fly ash mortars.

    PubMed

    Jóźwiak-Niedźwiedzka, Daria

    2015-01-01

    The results of microstructural characterization of mortars containing fly ash class C (High Calcium Fly Ash) from combustion of lignite are presented. The evaluation of the microstructure was performed using scanning electron microscope, optical, and confocal microscope. The tested beams were bent till the crack and microcracks opening, which were healed during the different curing time. The results showed that the replacement of cement with fly ash class C influenced the process of crack healing. The addition of HCFA, at both 30% and 60%, speeds up the self-healing process in cracks and particularly in micro-cracks. In the research, the completely filling up of the cracks by new phases has not been observed, only the beginning of such process has been noticed.

  17. Microencapsulation of gallium-indium (Ga-In) liquid metal for self-healing applications.

    PubMed

    Blaiszik, B J; Jones, A R; Sottos, N R; White, S R

    2014-01-01

    Microcapsules containing a liquid metal alloy core of gallium-indium (Ga-In) are prepared via in situ urea-formaldehyde (UF) microencapsulation. The capsule size, shape, thermal properties, and shell wall thickness are investigated. We prepare ellipsoidal capsules with major and minor diameter aspect ratios ranging from 1.64 to 1.08 and with major diameters ranging from 245 µm to 3 µm. We observe that as the capsule major diameter decreases, the aspect ratio approaches 1. The thermal properties of the prepared microcapsules are investigated by thermogravimetric (TGA) and differential scanning calorimetry (DSC). Microcapsules are shown to survive incorporation into an epoxy matrix and to trigger via mechanical damage to the cured matrix. Microcapsules containing liquid metal cores may have diverse applications ranging from self-healing to contrast enhancement or the demonstration of mechano-adaptive circuitry.

  18. Fabrication of self-healing super-hydrophobic surfaces on aluminium alloy substrates

    SciTech Connect

    Wang, Yang; Wei Liu, Xiao; Zhang, Hai Feng Zhou, Zhi Ping

    2015-04-15

    We present a method to fabricate a super-hydrophobic surface with a self-healing ability on an aluminium alloy substrate. The coatings are obtained by combining a two-step process (first, the substrate is immersed in a solution of HCl, HF and H{sub 2}O, and then in boiling water) and succeeding surface fluorination with a solution of poly(vinylidene-fluoride-co-hexafluoropropylene) and a fluoroalkyl silane. The morphological features and chemical composition were studied by scanning electron micrometry and energy-dispersive X-ray spectroscopy. The prepared super-hydrophobic aluminium surfaces showed hierarchical structures forming pores, petals and particles with a contact angle of 161° and a sliding angle of 3°.

  19. Self-Healing Superhydrophobic Fluoropolymer Brushes as Highly Protein-Repellent Coatings.

    PubMed

    Wang, Zhanhua; Zuilhof, Han

    2016-06-28

    Superhydrophobic surfaces with micro/nanostructures are widely used to prevent nonspecific adsorption of commercial polymeric and/or biological materials. Herein, a self-healing superhydrophobic and highly protein-repellent fluoropolymer brush was grafted onto nanostructured silicon by surface-initiated atom transfer radical polymerization (ATRP). Both the superhydrophobicity and antifouling properties (as indicated for isolated protein solutions and for 10% blood plasma) are well repaired upon serious chemical degradation (by e.g. air plasma). This brush still maintains excellent superhydrophobicity and good antifouling properties even after 5 damage-repair cycles, which opens a new door to fabricate long-term antifouling coatings on various substrates that can be used in harsh environments. PMID:27305351

  20. Fabrication of self-healing super-hydrophobic surfaces on aluminium alloy substrates

    NASA Astrophysics Data System (ADS)

    Wang, Yang; Wei Liu, Xiao; Zhang, Hai Feng; Zhou, Zhi Ping

    2015-04-01

    We present a method to fabricate a super-hydrophobic surface with a self-healing ability on an aluminium alloy substrate. The coatings are obtained by combining a two-step process (first, the substrate is immersed in a solution of HCl, HF and H2O, and then in boiling water) and succeeding surface fluorination with a solution of poly(vinylidene-fluoride-co-hexafluoropropylene) and a fluoroalkyl silane. The morphological features and chemical composition were studied by scanning electron micrometry and energy-dispersive X-ray spectroscopy. The prepared super-hydrophobic aluminium surfaces showed hierarchical structures forming pores, petals and particles with a contact angle of 161° and a sliding angle of 3°.

  1. Solitary Congenital Erosion in a Newborn: Report of a Solitary Congenital Self-Healing Reticulohistiocytosis

    PubMed Central

    Kim, Jung Eun; Kim, Byung Jik

    2014-01-01

    Congenital self-healing reticulohistiocytosis (CSHRH) is a rare, cutaneous, self-limited form of Langerhans cell histiocytosis. Whereas multiple lesions are common, a solitary lesion is rare. A 14-day-old neonate presented with a solitary, 5-mm, oval, reddish, and eroded papule with crust on the left thigh that had existed since birth. No systemic involvement was found. Histopathology revealed dense infiltration of large histiocytes with scattered eosinophils and lymphocytes in the dermis. Immunohistochemistry showed S-100 and CD1a positivity. Two months later, the skin lesion involuted spontaneously, without evidence of recurrence and extracutaneous involvement. On the basis of the characteristic clinical course and typical histopathological findings, a diagnosis of solitary CSHRH was made. PMID:24882983

  2. Self-healing photo-neuropathy and cervical spinal arthrosis in four sisters with brachioradial pruritus

    PubMed Central

    2009-01-01

    The cause of brachioradial pruritus (a localized itching on the arms or shoulders) is controversial. The role of sun and cervical spine disease has been discussed. This is a report on four sisters suffering from brachioradial pruritus recurring every summer. The sisters spent much time outdoors and exposed themselves extensively to the sun. They also had occupations requiring heavy lifting. Cervical radiographs indicated arthrosis. The density of sensory nerve fibers in the skin biopsies from the itchy skin of the arms, visualized by antibodies against a pan-neuronal marker, protein gene product 9.5, was reduced compared with biopsies from the same skin region during the symptom-free period in the winter. This data exemplifies that brachioradial pruritus is a self healing photoneuropathy occurring in middle aged adults predisposed by cervical arthrosis. PMID:19919691

  3. The kinetics and quality of acquired resistance in self-healing and metastatic leishmaniasis.

    PubMed Central

    Poulter, L W

    1979-01-01

    Quantitative methods for enumerating viable L. enriettii in tissues have been used to determine the course of cutaneous leishmaniasis in guinea-pigs. The development and kinetics of acquired resistance have been evaluated in self-healing and chronic metastatic forms of the disease. It is revealed that 3 weeks after a primary local infection, a standard challenge infection is totally eliminated within 7 days. This resistance is as strong in animals with a current infection as it is in those that have fully recovered from such an infection. Animals developing metastatic disease also develop resistance to the standard challenge. This is initially as strong as in animals with only localized disease, but wanes with the progression of the infection. Although the quality of resistance becomes poorer in animals with metastatic infection, it is not lost completely. The relationship between acquired resistance and the resolution of the primary infection is discussed. PMID:380855

  4. Robust, Self-Healing Superhydrophobic Fabrics Prepared by One-Step Coating of PDMS and Octadecylamine.

    PubMed

    Xue, Chao-Hua; Bai, Xue; Jia, Shun-Tian

    2016-01-01

    A robust, self-healing superhydrophobic poly(ethylene terephthalate) (PET) fabric was fabricated by a convenient solution-dipping method using an easily available material system consisting of polydimethylsiloxane and octadecylamine (ODA). The surface roughness was formed by self-roughening of ODA coating on PET fibers without any lithography steps or adding any nanomaterials. The fabric coating was durable to withstand 120 cycles of laundry and 5000 cycles of abrasion without apparently changing the superhydrophobicity. More interestingly, the fabric can restore its super liquid-repellent property by 72 h at room temperature even after 20000 cycles of abrasion. Meanwhile, after being damaged chemically, the fabric can restore its superhydrophobicity automatically in 12 h at room temperature or by a short-time heating treatment. We envision that this simple but effective coating system may lead to the development of robust protective clothing for various applications. PMID:27264995

  5. An immune-inspired swarm aggregation algorithm for self-healing swarm robotic systems.

    PubMed

    Timmis, J; Ismail, A R; Bjerknes, J D; Winfield, A F T

    2016-08-01

    Swarm robotics is concerned with the decentralised coordination of multiple robots having only limited communication and interaction abilities. Although fault tolerance and robustness to individual robot failures have often been used to justify the use of swarm robotic systems, recent studies have shown that swarm robotic systems are susceptible to certain types of failure. In this paper we propose an approach to self-healing swarm robotic systems and take inspiration from the process of granuloma formation, a process of containment and repair found in the immune system. We use a case study of a swarm performing team work where previous works have demonstrated that partially failed robots have the most detrimental effect on overall swarm behaviour. We have developed an immune inspired approach that permits the recovery from certain failure modes during operation of the swarm, overcoming issues that effect swarm behaviour associated with partially failed robots. PMID:27178784

  6. Smoking affects the self-healing capacity of periodontal tissues. A histological study in the rat.

    PubMed

    Benatti, Bruno Braga; César-Neto, João Batista; Gonçalves, Patrícia Furtado; Sallum, Enílson Antônio; Nociti, Francisco Humberto

    2005-10-01

    This study aimed to evaluate in rats the impact of cigarette smoke inhalation (CSI) and nicotine administration (NA) on a periodontal healing model in the absence of a plaque biofilm. Wistar rats (n = 42) were assigned to three groups: Group 1, control (n = 14); Group 2, NA (3 mg kg(-1)) (n = 14); and Group 3, CSI (n = 14). Thirty days after CSI and NA exposure, fenestration defects were created buccally to the distal root of the first mandibular molar. The animals were killed 21 d later and their mandibles were processed for histological examination. The percentage of bone fill and the density of newly formed bone were assessed histometrically. Intergroup analysis demonstrated that compared to the control and NA groups, CSI was associated with a reduced rate of bone repair. No new cementum had been formed along the root surface in any of the three groups. It is concluded that cigarette smoke reduces the self-healing capacity of periodontal tissues.

  7. Interlayer structure and self-healing in suspensions of brush-stabilized nanoplatelets with smectic order.

    PubMed

    White, K L; Wong, M; Li, P; Miyamoto, M; Higaki, Y; Takahara, A; Sue, H-J

    2015-02-01

    We have investigated the rheology of an uncured epoxy fluid containing high aspect ratio (length/thickness ≈ 160) α-zirconium phosphate (ZrP) nanoplatelets with smectic order. The nanoplatelets were exfoliated into monocrystalline sheets with uniform thickness using a monoamine-terminated oligomer. The oligomers were densely grafted to the plate surfaces and behave as a molecular brush. Suspensions containing ∼ 2 vol.% ZrP and above show liquid crystalline order with scattering peaks characteristic of a smectic (layered) mesophase. At much higher loading, ∼ 4 vol.% ZrP, there is a sharp transition in visual appearance, steady shear rheology, and linear and non-linear viscoelasticity that is attributed to the reversible interdigitation of oligomer chains between closely spaced layers. The oligomers are proposed to serve as inter-lamellar bridges that store elastic stresses for intermediate rates of deformation, but are able to relax on longer time scales. Under steady shearing conditions, the smectic suspensions with "overlapped" microstructure show a discontinuous flow curve characteristic of shear banding that is attributed to the dynamic pull-out of oligomer chains from the overlap region. At high shear rates, the limiting viscosity of the concentrated suspensions is on the same order of magnitude as the unfilled suspending fluid. When the rate of deformation is reduced below a critical time scale, the original network strength, and corresponding microstructure, is recovered through a passive self-healing process. The unique combination of concentration-dependent yield stress, low post-yield viscosity, and self-healing is potentially useful for various applications in the liquid state, and desirable for scalable processing of nanocomposite materials for structural applications. PMID:25519712

  8. Diatomaceous earth as a protective vehicle for bacteria applied for self-healing concrete.

    PubMed

    Wang, J Y; Belie, N De; Verstraete, W

    2012-04-01

    Crack repair is crucial since cracks are the main cause for the decreased service life of concrete structures. An original and promising way to repair cracks is to pre-incorporate healing agents inside the concrete matrix to heal cracks the moment they appear. Thus, the concrete obtains self-healing properties. The goal of our research is to apply bacterially precipitated CaCO₃ to heal cracks in concrete since the microbial calcium carbonate is more compatible with the concrete matrix and more environmentally friendly relative to the normally used polymeric materials. Diatomaceous earth (DE) was used in this study to protect bacteria from the high-pH environment of concrete. The experimental results showed that DE had a very good protective effect for bacteria. DE immobilized bacteria had much higher ureolytic activity (12-17 g/l urea was decomposed within 3 days) than that of un-immobilized bacteria (less than 1 g/l urea was decomposed within the same time span) in cement slurry. The optimal concentration of DE for immobilization was 60% (w/v, weight of DE/volume of bacterial suspension). Self-healing in cracked specimens was visualized under light microscopy. The images showed that cracks with a width ranging from 0.15 to 0.17 mm in the specimens containing DE immobilized bacteria were completely filled by the precipitation. Scanning electron microscopy (SEM) and energy dispersive spectrometry (EDS) were used to characterize the precipitation around the crack wall, which was confirmed to be calcium carbonate. The result from a capillary water absorption test showed that the specimens with DE immobilized bacteria had the lowest water absorption (30% of the reference ones), which indicated that the precipitation inside the cracks increased the water penetration resistance of the cracked specimens. PMID:21927907

  9. Demonstrating the self-healing behaviour of some selected ceramics under combustion chamber conditions

    NASA Astrophysics Data System (ADS)

    Farle, A.; Boatemaa, L.; Shen, L.; Gövert, S.; Kok, J. B. W.; Bosch, M.; Yoshioka, S.; van der Zwaag, S.; Sloof, W. G.

    2016-08-01

    Closure of surface cracks by self-healing of conventional and MAX phase ceramics under realistic turbulent combustion chamber conditions is presented. Three ceramics namely; Al2O3, Ti2AlC and Cr2AlC are investigated. Healing was achieved in Al2O3 by even dispersion of TiC particles throughout the matrix as the MAX phases, Ti2AlC and Cr2AlC exhibit intrinsic self-healing. Fully dense samples (>95%) were sintered by spark plasma sintering and damage was introduced by indentation, quenching and low perpendicular velocity impact methods. The samples were exposed to the oxidizing atmosphere in the post flame zone of a turbulent flame in a combustion chamber to heal at temperatures of approx. 1000 °C at low pO2 levels for 4 h. Full crack-gap closure was observed for cracks up to 20 mm in length and more than 10 μm in width. The reaction products (healing agents) were analysed by scanning electron microscope, x-ray microanalysis and XRD. A semi-quantification of the healing showed that cracks in Al2O3/TiC composite (width 1 μm and length 100 μm) were fully filled with TiO2. In Ti2AlC large cracks were fully filled with a mixture of TiO2 and Al2O3. And in the Cr2AlC, cracks of up to 1.0 μm in width and more than 100 μm in length were also completely filled with Al2O3.

  10. Interlayer structure and self-healing in suspensions of brush-stabilized nanoplatelets with smectic order.

    PubMed

    White, K L; Wong, M; Li, P; Miyamoto, M; Higaki, Y; Takahara, A; Sue, H-J

    2015-02-01

    We have investigated the rheology of an uncured epoxy fluid containing high aspect ratio (length/thickness ≈ 160) α-zirconium phosphate (ZrP) nanoplatelets with smectic order. The nanoplatelets were exfoliated into monocrystalline sheets with uniform thickness using a monoamine-terminated oligomer. The oligomers were densely grafted to the plate surfaces and behave as a molecular brush. Suspensions containing ∼ 2 vol.% ZrP and above show liquid crystalline order with scattering peaks characteristic of a smectic (layered) mesophase. At much higher loading, ∼ 4 vol.% ZrP, there is a sharp transition in visual appearance, steady shear rheology, and linear and non-linear viscoelasticity that is attributed to the reversible interdigitation of oligomer chains between closely spaced layers. The oligomers are proposed to serve as inter-lamellar bridges that store elastic stresses for intermediate rates of deformation, but are able to relax on longer time scales. Under steady shearing conditions, the smectic suspensions with "overlapped" microstructure show a discontinuous flow curve characteristic of shear banding that is attributed to the dynamic pull-out of oligomer chains from the overlap region. At high shear rates, the limiting viscosity of the concentrated suspensions is on the same order of magnitude as the unfilled suspending fluid. When the rate of deformation is reduced below a critical time scale, the original network strength, and corresponding microstructure, is recovered through a passive self-healing process. The unique combination of concentration-dependent yield stress, low post-yield viscosity, and self-healing is potentially useful for various applications in the liquid state, and desirable for scalable processing of nanocomposite materials for structural applications.

  11. Self-healing of cement fractures under dynamic flow of CO2-rich brine

    NASA Astrophysics Data System (ADS)

    Cao, Peilin; Karpyn, Zuleima T.; Li, Li

    2015-06-01

    Fractures and defects in wellbore cement can lead to increased possibilities of CO2 leakage from abandoned wells during geological carbon sequestration. To investigate the physicochemical response of defective wellbore cement to CO2-rich brine, we carried out a reactive flow-through experiment using an artificially fractured cement sample at a length of 224.8 mm. A brine solution with dissolved CO2 at a pH of approximately 3.9 was injected through the sample at a constant rate of 0.0083 cm3/s. Surface optical profilometry analysis and 3-D X-ray microtomography imaging confirmed fracture closure and self-healing behavior consistent with the measured permeability decrease. Visual inspection of the reacted fracture surface showed the development of reactive patterns mapping the flow velocity field inside the fracture, as well as restricted flow toward the sample outlet. The postexperiment permeability of the core sample was measured at half of its initial permeability. A reactive transport model was developed with parameters derived from the experiment to further examine property evolution of fractured cement under dynamic flow of CO2-rich brine. Sensitivity analysis showed that residence time and the size of initial fracture aperture are the key factors controlling the tendency to self-healing or fracture opening behavior and therefore determine the long-term integrity of the wellbore cement. Longer residence time and small apertures promote mineral precipitation, fracture closure, and therefore flow restriction. This work also suggests a narrow threshold separating the fracture opening and self-sealing behavior.

  12. Stretchable polymer-based electronic device

    DOEpatents

    Maghribi, Mariam N.; Krulevitch, Peter A.; Davidson, James Courtney; Wilson, Thomas S.; Hamilton, Julie K.; Benett, William J.; Tovar, Armando R.

    2008-02-26

    A stretchable electronic circuit or electronic device and a polymer-based process to produce a circuit or electronic device containing a stretchable conducting circuit. The stretchable electronic apparatus has a central longitudinal axis and the apparatus is stretchable in a longitudinal direction generally aligned with the central longitudinal axis. The apparatus comprises a stretchable polymer body and at least one circuit line operatively connected to the stretchable polymer body. The circuit line extends in the longitudinal direction and has a longitudinal component that extends in the longitudinal direction and has an offset component that is at an angle to the longitudinal direction. The longitudinal component and the offset component allow the apparatus to stretch in the longitudinal direction while maintaining the integrity of the circuit line.

  13. Magnetic-Assisted, Self-Healable, Yarn-Based Supercapacitor.

    PubMed

    Huang, Yang; Huang, Yan; Zhu, Minshen; Meng, Wenjun; Pei, Zengxia; Liu, Chang; Hu, Hong; Zhi, Chunyi

    2015-06-23

    Yarn-based supercapacitors have received considerable attention recently, offering unprecedented opportunities for future wearable electronic devices (e.g., smart clothes). However, the reliability and lifespan of yarn-based supercapacitors can be seriously limited by accidental mechanical damage during practical applications. Therefore, a supercapacitor endowed with mechanically and electrically self-healing properties is a brilliant solution to the challenge. Compared with the conventional planar-like or large wire-like structure, the reconnection of the broken yarn electrode composed of multiple tiny fibers (diameter <20 μm) is much more difficult and challenging, which directly affects the restoration of electrical conductivity after damage. Herein, a self-healable yarn-based supercapacitor that ensures the reconnection of broken electrodes has been successfully developed by wrapping magnetic electrodes around a self-healing polymer shell. The strong force from magnetic attraction between the broken yarn electrodes benefits reconnection of fibers in the yarn electrodes during self-healing and thus offers an effective strategy for the restoration of electric conductivity, whereas the polymer shell recovers the configuration integrity and mechanical strength. With the design, the specific capacitance of our prototype can be restored up to 71.8% even after four breaking/healing cycles with great maintenance of the whole device's mechanical properties. This work may inspire the design and fabrication of other distinctive self-healable and wearable electronic devices. PMID:26029976

  14. Dynamic gold nanoparticle, polymer-based composites

    NASA Astrophysics Data System (ADS)

    Firestone, Millicent; Junghans, Ann; Hayden, Steven; Majeski, Jaroslaw; CINT, Lujan Team

    2014-03-01

    Artificial polymer-based biomembranes may serve as a foundational architecture for the integration and spatial organization of metal nanoparticles forming functional nanocomposites. Nonionic triblock copolymer (PEO-PPO-PEO), lipid-based gels, containing Au nanoparticles (NPs) can be prepared by either external doping of the preformed nanoparticles or by in-situ reduction of Au 3+. Neutron reflectivity on quartz supported thin films of the Au NP -doped polymer-based biomembranes was used to determine the location of the Au. The nanoparticles were found to preferentially reside within the ethylene oxide chains located at the interface of the bulk water channels and the amphiphile bilayers. The embedded Au nanoparticles can act as localized heat sinks, inducing changes in the polymer conformation. The collective, thermally-triggered expansion and contraction of the EO chains modulate the mesophase structure of the gels. Synchrotron X-ray scattering (SAXS) was used to monitor mesophase structure as a function of both temperature and photo-irradiation. These studies represent a first step towards designingexternally-responsive polymer-nanoparticle composites.

  15. Dynamics of Self-Healing Slip Pulses on Velocity-Weakening Interfaces: Formation, steady propagation and interaction with stress heterogeneity

    NASA Astrophysics Data System (ADS)

    Elbanna, A. E.; Lapusta, N.; Heaton, T. H.

    2009-12-01

    Seismic inversions indicate that earthquake ruptures may propagate in a self-healing pulse-like mode. Prior studies have shown that velocity-weakening (VW) interfaces can produce crack-like, pulse-like, and multi-pulse ruptures, depending on fault prestress and the assumed weakening. Multiple pulses have been explained by destabilization of steady sliding behind the front of the crack-like rupture that forms after the nucleation stage. We explore the possibility that transition from the initial crack-like rupture to a self-healing pulse can also be understood based on such stability analysis. Prior numerical simulations of dynamic rupture on uniformly prestressed VW interfaces have found either growing or decaying pulse-like ruptures. We show that steady slip pulses can be produced on such interfaces by a special nucleation procedure and study response of such pulses to prestress changes. In particular, we find that such solutions lose their steadiness once they enter areas of different constant prestress. We study the formation and propagation of pulse-like ruptures in a 2D antiplane fault model with rate and state friction and enhanced VW at seismic slip velocities. The fault has uniform prestress, except in a small overstressed region of rupture nucleation. For a range of model parameters that favors slip pulses, we find that the decrease of slip velocity behind the front of the initial crack causes significant increase in the maximum growth rate and phase velocities of unstable modes. We hypothesize that this leads to the local rupture arrest and slip-pulse formation. Phase velocities of the growing wavelengths affect the healing-front speed of the resulting slip pulse and hence the evolution of the pulse width, since the difference between the healing-front speed and the rupture speed of the pulse determines how the pulse width changes with propagation. Using a special stress distribution in the nucleation region, we are able to produce steady pulse

  16. 40 CFR 721.10036 - Acetaldehyde based polymer (generic).

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Acetaldehyde based polymer (generic... Specific Chemical Substances § 721.10036 Acetaldehyde based polymer (generic). (a) Chemical substance and... based polymer (PMN P-02-406) is subject to reporting under this section for the significant new...

  17. 40 CFR 721.10036 - Acetaldehyde based polymer (generic).

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Acetaldehyde based polymer (generic... Specific Chemical Substances § 721.10036 Acetaldehyde based polymer (generic). (a) Chemical substance and... based polymer (PMN P-02-406) is subject to reporting under this section for the significant new...

  18. 40 CFR 721.10036 - Acetaldehyde based polymer (generic).

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Acetaldehyde based polymer (generic... Specific Chemical Substances § 721.10036 Acetaldehyde based polymer (generic). (a) Chemical substance and... based polymer (PMN P-02-406) is subject to reporting under this section for the significant new...

  19. 40 CFR 721.10036 - Acetaldehyde based polymer (generic).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Acetaldehyde based polymer (generic... Specific Chemical Substances § 721.10036 Acetaldehyde based polymer (generic). (a) Chemical substance and... based polymer (PMN P-02-406) is subject to reporting under this section for the significant new...

  20. 40 CFR 721.10036 - Acetaldehyde based polymer (generic).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Acetaldehyde based polymer (generic... Specific Chemical Substances § 721.10036 Acetaldehyde based polymer (generic). (a) Chemical substance and... based polymer (PMN P-02-406) is subject to reporting under this section for the significant new...

  1. Polyalkene-based shape-memory polymers

    NASA Astrophysics Data System (ADS)

    Alonso, J.; Cuevas, J. M.; Dios, J. R.; Vilas, J. L.; León, L. M.

    2007-07-01

    A series of polymers showing shape memory properties were developed based on polyalkenes derived from cyclooctene and related structures. These polymeric systems were synthesized via ring-opening metathesis polymerization (ROMP) using a well-defined ruthenium catalyst (Grubbs' type) by varying reaction conditions and proportions. Control over molecular weight was achieved by the inclusion of a chain transfer agent (CTA) and its influence on the behaviour of the obtained materials was evaluated. In order to provide them with shape memory behaviour the compounds were subjected to suitable chemical-thermal treatments and its characterization was accomplished by means of several techniques: differential scanning calorimetry (DSC), dynamic mechanical thermal analysis (DMTA), etc. Thus polymers developed herein could become a different alternative to the most studied and commercially available polyurethane based systems.

  2. Supramolecular Polymer Nanocomposites - Improvement of Mechanical Properties

    NASA Astrophysics Data System (ADS)

    Hinricher, Jesse; Neikirk, Colin; Priestley, Rodney

    2015-03-01

    Supramolecular polymers differ from traditional polymers in that their repeat units are connected by hydrogen bonds that can reversibly break and form under various stimuli. They can be more easily recycled than conventional materials, and their highly temperature dependent viscosities result in reduced energy consumption and processing costs. Furthermore, judicious selection of supramolecular polymer architecture and functionality allows the design of advanced materials including shape memory and self-healing materials. Supramolecular polymers have yet to see widespread use because they can't support much weight due to their inherent mechanical weakness. In order to address this issue, the mechanical strength of supramolecular polymer nanocomposites based on ureidopyrmidinone (UPy) telechelic poly(caprolactone) doped with surface activated silica nanoparticles was investigated by tensile testing and dynamic mechanical analysis. The effects of varying amounts and types of nanofiller surface functionality were investigated to glean insight into the contributions of filler-filler and filler-matrix interactions to mechanical reinforcement in supramolecular polymer nanocomposites. MRSEC NSF DMR 0819860 (PI: Prof. N. Phuan Ong) REU Site Grant: NSF DMR-1156422 (PI: Prof. Mikko Haataja)

  3. Dendrite-Free Lithium Deposition via Self-Healing Electrostatic Shield Mechanism

    SciTech Connect

    Ding, Fei; Xu, Wu; Graff, Gordon L.; Zhang, Jian; Sushko, Maria L.; Chen, Xilin; Shao, Yuyan; Engelhard, Mark H.; Nie, Zimin; Xiao, Jie; Liu, Xingjiang; Sushko, P. V.; Liu, Jun; Zhang, Jiguang

    2013-02-28

    Lithium metal batteries are called the “holy grail” of energy storage systems. However, lithium dendrite growth in these batteries has prevented their practical applications in the last 40 years. Here we show a novel mechanism which can fundamentally change the dendritic morphology of lithium deposition. A low concentration of the second cations (including ions of cesium, rubidium, potassium, and strontium) exhibits an effective reduction potential lower than the standard reduction potential of lithium ions when the chemical activities of these second cations are much lower than that of lithium ions. During lithium deposition, these second cations will form a self-healing electrostatic shield around the initial tip of lithium whenever it is formed. This shield will repel the incoming lithium ions and force them to deposit in the smoother region of the anode so a dendrite-free film is obtained. This mechanism is effective on dendrite prevention in both lithium metal and lithium ion batteries. They may also prevent dendrite growth in other metal batteries and have transformational impact on the smooth deposition in general electrodeposition processes.

  4. Ruthenium Grubbs' catalyst nanostructures grown by UV-excimer-laser ablation for self-healing applications

    NASA Astrophysics Data System (ADS)

    Aïssa, B.; Nechache, R.; Haddad, E.; Jamroz, W.; Merle, P. G.; Rosei, F.

    2012-10-01

    A self healing composite material consisting of 5-Ethylidene-2-Norbornene (5E2N) monomer reacted with Ruthenium Grubbs' Catalyst (RGC) was prepared. First, the kinetics of the 5E2N ring opening metathesis polymerization (ROMP) reaction RGC was studied as a function of temperature. We show that the polymerization reaction is still effective in a large temperature range (-15 to 45 °C), occurring at short time scales (less than 1 min at 40 °C). Second, the amount of RGC required for ROMP reaction significantly decreased through its nanostructuration by means of a UV-excimer laser ablation process. RGC nanostructures of few nanometers in size where successfully obtained directly on silicon substrates. The X-ray photoelectron spectroscopy data strongly suggest that the RGC still keep its original stoichiometry after nanostructuration. More importantly, the associated ROMP reaction was successfully achieved at an extreme low RGC concentration equivalent to (11.16 ± 1.28) × 10-4 Vol.%, occurring at very short time reaction. This approach opens new prospects for using healing agent nanocomposite materials for self-repair functionality, thereby obtaining a higher catalytic efficiency per unit mass.

  5. Self-healing of unitarity in effective field theories and the onset of new physics

    NASA Astrophysics Data System (ADS)

    Aydemir, Ufuk; Anber, Mohamed M.; Donoghue, John F.

    2012-07-01

    In effective field theories it is common to identify the onset of new physics with the violation of tree-level unitarity. However, we show that this is parametrically incorrect in the case of chiral perturbation theory, and is probably theoretically incorrect in general. In the chiral theory, we explore perturbative unitarity violation as a function of the number of colors and the number of flavors, holding the scale of the “new physics” (i.e. QCD) fixed. This demonstrates that the onset of new physics is parametrically uncorrelated with tree-unitarity violation. When the latter scale is lower than that of new physics, the effective theory must heal its unitarity violation itself, which is expected because the field theory satisfies the requirements of unitarity. In the chiral theory, the self-healing results in a resonant structure with scalar quantum numbers. In the electroweak variant of this argument, the structure must have the properties of the Higgs and must couple proportional to the mass in both gauge boson and fermion scattering. A similar example can be seen in the case of general relativity coupled to multiple matter fields, where iteration of the vacuum polarization diagram restores unitarity. We present arguments that suggest the correct identification should be connected to the onset of inelasticity rather than unitarity violation. We describe how the onset of inelasticity can occur in the effective theory, although it does not appear possible to predict the onset reliably.

  6. Controlling diffusion for a self-healing radiation tolerant nanostructured ferritic alloy

    DOE PAGES

    Miller, Michael K.; Parish, Chad M.; Bei, Hongbin

    2014-12-18

    Diffusion plays a major role in the stability of microstructures to extreme conditions of high temperature and high doses of irradiation. In nanostructured ferritic alloys, first principle calculations indicate that the binding energy of vacancies is reduced by the presence of oxygen, titanium and yttrium atoms. Therefore, the number of free vacancies available for diffusion can be greatly reduced. The mechanical properties of these alloys, compared to traditional wrought alloys of similar composition and grain structure, is distinctly different, and the ultrafine grained alloy is distinguished by a high number density of Ti–Y–O-enriched nanoclusters and solute clusters, which drives themore » mechanical response. When a displacement cascade interacts with a nanocluster, the solute atoms are locally dispersed into the matrix by ballistic collisions, but immediately a new nanocluster reforms due to the local supersaturation of solutes and vacancies until the excess vacancies are consumed. Furthermore, the result of these processes is a structural material for advanced energy systems with a microstructure that is self-healing and tolerant to high doses of radiation and high temperatures.« less

  7. Controlling diffusion for a self-healing radiation tolerant nanostructured ferritic alloy

    SciTech Connect

    Miller, Michael K.; Parish, Chad M.; Bei, Hongbin

    2014-12-18

    Diffusion plays a major role in the stability of microstructures to extreme conditions of high temperature and high doses of irradiation. In nanostructured ferritic alloys, first principle calculations indicate that the binding energy of vacancies is reduced by the presence of oxygen, titanium and yttrium atoms. Therefore, the number of free vacancies available for diffusion can be greatly reduced. The mechanical properties of these alloys, compared to traditional wrought alloys of similar composition and grain structure, is distinctly different, and the ultrafine grained alloy is distinguished by a high number density of Ti–Y–O-enriched nanoclusters and solute clusters, which drives the mechanical response. When a displacement cascade interacts with a nanocluster, the solute atoms are locally dispersed into the matrix by ballistic collisions, but immediately a new nanocluster reforms due to the local supersaturation of solutes and vacancies until the excess vacancies are consumed. Furthermore, the result of these processes is a structural material for advanced energy systems with a microstructure that is self-healing and tolerant to high doses of radiation and high temperatures.

  8. Light-activated photocurrent degradation and self-healing in perovskite solar cells.

    PubMed

    Nie, Wanyi; Blancon, Jean-Christophe; Neukirch, Amanda J; Appavoo, Kannatassen; Tsai, Hsinhan; Chhowalla, Manish; Alam, Muhammad A; Sfeir, Matthew Y; Katan, Claudine; Even, Jacky; Tretiak, Sergei; Crochet, Jared J; Gupta, Gautam; Mohite, Aditya D

    2016-01-01

    Solution-processed organometallic perovskite solar cells have emerged as one of the most promising thin-film photovoltaic technology. However, a key challenge is their lack of stability over prolonged solar irradiation. Few studies have investigated the effect of light soaking on hybrid perovskites and have attributed the degradation in the optoelectronic properties to photochemical or field-assisted ion migration. Here we show that the slow photocurrent degradation in thin-film photovoltaic devices is due to the formation of light-activated meta-stable deep-level trap states. However, the devices can self-heal completely by resting them in the dark for <1 min or the degradation can be completely prevented by operating the devices at 0 °C. We investigate several physical mechanisms to explain the microscopic origin for the formation of these trap states, among which the creation of small polaronic states involving localized cooperative lattice strain and molecular orientations emerges as a credible microscopic mechanism requiring further detailed studies.

  9. Light-activated photocurrent degradation and self-healing in perovskite solar cells

    NASA Astrophysics Data System (ADS)

    Nie, Wanyi; Blancon, Jean-Christophe; Neukirch, Amanda J.; Appavoo, Kannatassen; Tsai, Hsinhan; Chhowalla, Manish; Alam, Muhammad A.; Sfeir, Matthew Y.; Katan, Claudine; Even, Jacky; Tretiak, Sergei; Crochet, Jared J.; Gupta, Gautam; Mohite, Aditya D.

    2016-05-01

    Solution-processed organometallic perovskite solar cells have emerged as one of the most promising thin-film photovoltaic technology. However, a key challenge is their lack of stability over prolonged solar irradiation. Few studies have investigated the effect of light soaking on hybrid perovskites and have attributed the degradation in the optoelectronic properties to photochemical or field-assisted ion migration. Here we show that the slow photocurrent degradation in thin-film photovoltaic devices is due to the formation of light-activated meta-stable deep-level trap states. However, the devices can self-heal completely by resting them in the dark for <1 min or the degradation can be completely prevented by operating the devices at 0 °C. We investigate several physical mechanisms to explain the microscopic origin for the formation of these trap states, among which the creation of small polaronic states involving localized cooperative lattice strain and molecular orientations emerges as a credible microscopic mechanism requiring further detailed studies.

  10. Effects of Cesium Cations in Lithium Deposition via Self-Healing Electrostatic Shield Mechanism

    SciTech Connect

    Ding, Fei; Xu, Wu; Chen, Xilin; Zhang, Jian; Shao, Yuyan; Engelhard, Mark H.; Zhang, Yaohui; Blake, Thomas A.; Graff, Gordon L.; Liu, Xingjiang; Zhang, Jiguang

    2014-02-27

    Lithium (Li) dendrite formation is one of the critical challenges for rechargeable Li metal batteries. The traditional method to suppress Li dendrites by using high-quality solid electrolyte interface (SEI) films cannot effectively solve this problem. Recently, we proposed a novel self-healing electrostatic shield (SHES) mechanism to change the Li deposition behavior. The SHES mechanism forces Li to be deposited in the region away from protuberant tips by using non-Li cations as additives that preferentially accumulate but not deposit on the active sites of Li electrode. In this paper, the electrochemical behavior of cesium cation (Cs+) as the typical non-Li cation suitable for the SHES mechanism was further investigated in detail to reveal its effects on preventing Li dendrites and interactions with Li electrode. It is found that typical adsorption behavior instead of chemical reaction is observed. The existence of Cs+ cation in the electrolyte does not change the components and structure of the Li surface film and this is consistent with the projection of the SHES mechanism. Various factors affecting the effectiveness of SHES mechanism are also discussed. The morphologies of Li films deposited is smooth and uniform during the repeated deposition-stripping cycles and at various current densities (from 0.1 to 1.0 mA cm-2) by adding just a small amount (0.05 M) of Cs+-additive in the electrolyte.

  11. Enhancement of oxidation resistance via a self-healing boron carbide coating on diamond particles.

    PubMed

    Sun, Youhong; Meng, Qingnan; Qian, Ming; Liu, Baochang; Gao, Ke; Ma, Yinlong; Wen, Mao; Zheng, Weitao

    2016-02-02

    A boron carbide coating was applied to diamond particles by heating the particles in a powder mixture consisting of H3BO3, B and Mg. The composition, bond state and coverage fraction of the boron carbide coating on the diamond particles were investigated. The boron carbide coating prefers to grow on the diamond (100) surface than on the diamond (111) surface. A stoichiometric B4C coating completely covered the diamond particle after maintaining the raw mixture at 1200 °C for 2 h. The contribution of the boron carbide coating to the oxidation resistance enhancement of the diamond particles was investigated. During annealing of the coated diamond in air, the priory formed B2O3, which exhibits a self-healing property, as an oxygen barrier layer, which protected the diamond from oxidation. The formation temperature of B2O3 is dependent on the amorphous boron carbide content. The coating on the diamond provided effective protection of the diamond against oxidation by heating in air at 1000 °C for 1 h. Furthermore, the presence of the boron carbide coating also contributed to the maintenance of the static compressive strength during the annealing of diamond in air.

  12. Enhancement of oxidation resistance via a self-healing boron carbide coating on diamond particles

    PubMed Central

    Sun, Youhong; Meng, Qingnan; Qian, Ming; Liu, Baochang; Gao, Ke; Ma, Yinlong; Wen, Mao; Zheng, Weitao

    2016-01-01

    A boron carbide coating was applied to diamond particles by heating the particles in a powder mixture consisting of H3BO3, B and Mg. The composition, bond state and coverage fraction of the boron carbide coating on the diamond particles were investigated. The boron carbide coating prefers to grow on the diamond (100) surface than on the diamond (111) surface. A stoichiometric B4C coating completely covered the diamond particle after maintaining the raw mixture at 1200 °C for 2 h. The contribution of the boron carbide coating to the oxidation resistance enhancement of the diamond particles was investigated. During annealing of the coated diamond in air, the priory formed B2O3, which exhibits a self-healing property, as an oxygen barrier layer, which protected the diamond from oxidation. The formation temperature of B2O3 is dependent on the amorphous boron carbide content. The coating on the diamond provided effective protection of the diamond against oxidation by heating in air at 1000 °C for 1 h. Furthermore, the presence of the boron carbide coating also contributed to the maintenance of the static compressive strength during the annealing of diamond in air. PMID:26831205

  13. Enhancement of oxidation resistance via a self-healing boron carbide coating on diamond particles

    NASA Astrophysics Data System (ADS)

    Sun, Youhong; Meng, Qingnan; Qian, Ming; Liu, Baochang; Gao, Ke; Ma, Yinlong; Wen, Mao; Zheng, Weitao

    2016-02-01

    A boron carbide coating was applied to diamond particles by heating the particles in a powder mixture consisting of H3BO3, B and Mg. The composition, bond state and coverage fraction of the boron carbide coating on the diamond particles were investigated. The boron carbide coating prefers to grow on the diamond (100) surface than on the diamond (111) surface. A stoichiometric B4C coating completely covered the diamond particle after maintaining the raw mixture at 1200 °C for 2 h. The contribution of the boron carbide coating to the oxidation resistance enhancement of the diamond particles was investigated. During annealing of the coated diamond in air, the priory formed B2O3, which exhibits a self-healing property, as an oxygen barrier layer, which protected the diamond from oxidation. The formation temperature of B2O3 is dependent on the amorphous boron carbide content. The coating on the diamond provided effective protection of the diamond against oxidation by heating in air at 1000 °C for 1 h. Furthermore, the presence of the boron carbide coating also contributed to the maintenance of the static compressive strength during the annealing of diamond in air.

  14. Self-healing of vacancy defects in single-layer graphene and silicene

    NASA Astrophysics Data System (ADS)

    Özçelik, V. Ongun; Gurel, H. Hakan; Ciraci, S.

    2013-07-01

    Self-healing mechanisms of vacancy defects in graphene and silicene are studied using first-principles calculations. We investigated host adatom adsorption, diffusion, vacancy formation, and revealed atomistic mechanisms in the healing of single, double, and triple vacancies of single-layer graphene and silicene. Silicon adatom, which is adsorbed to silicene at the top site forms a dumbbell-like structure by pushing one Si atom underneath. The asymmetric reconstruction of the single vacancy in graphene is induced by the magnetization through the rebonding of two dangling bonds and acquiring a significant magnetic moment through the remaining unsaturated dangling bond. In silicene, three twofold coordinated atoms surrounding the single vacancy become fourfold coordinated and nonmagnetic through rebonding. The energy gained through new bond formation becomes the driving force for the reconstruction. Under the external supply of host atoms, while the vacancy defects of graphene heal perfectly, the Stone-Wales defect can form in the course of healing of silicene vacancy. The electronic and magnetic properties of suspended, single-layer graphene and silicene are modified by reconstructed vacancy defects.

  15. Self Healing of Vacancy Defects in Single Layer Graphene and Silicene

    NASA Astrophysics Data System (ADS)

    Ozcelik, V. Ongun; Gurel, Hakan; Ciraci, Salim

    2014-03-01

    Self healing mechanisms of vacancy defects in graphene and silicene are studied using first principles calculations. We investigated host adatom adsorption, diffusion, vacancy formation and revealed atomistic mechanisms in the healing of single, double and triple vacancies of single layer graphene and silicene. Silicon adatom, which is adsorbed to silicene at the top site forms a dumbbell like structure by pushing one Si atom underneath. The asymmetric reconstruction of the single vacancy in graphene is induced by the magnetization through the rebonding of two dangling bonds and acquiring a significant magnetic moment through remaining unsaturated dangling bond. In silicene, three two-fold coordinated atoms surrounding the single vacancy become four-fold coordinated and nonmagnetic through rebonding. The energy gained through new bond formation becomes the driving force for the reconstruction. Under the external supply of host atoms, while the vacancy defects of graphene heal perfectly, Stone-Wales defect can form in the course of healing of silicene vacancy. The electronic and magnetic properties of suspended, single layer graphene and silicene are modified by reconstructed vacancy defects.

  16. Controlling diffusion for a self-healing radiation tolerant nanostructured ferritic alloy

    NASA Astrophysics Data System (ADS)

    Miller, M. K.; Parish, C. M.; Bei, H.

    2015-07-01

    Diffusion plays a major role in the stability of microstructures to extreme conditions of high temperature and high doses of irradiation. In nanostructured ferritic alloys, first principle calculations indicate that the binding energy of vacancies is reduced by the presence of oxygen, titanium and yttrium atoms. Therefore, the number of free vacancies available for diffusion can be greatly reduced. The mechanical properties of these alloys, compared to traditional wrought alloys of similar composition and grain structure, is distinctly different, and the ultrafine grained alloy is distinguished by a high number density of Ti-Y-O-enriched nanoclusters and solute clusters, which drives the mechanical response. When a displacement cascade interacts with a nanocluster, the solute atoms are locally dispersed into the matrix by ballistic collisions, but immediately a new nanocluster reforms due to the local supersaturation of solutes and vacancies until the excess vacancies are consumed. The result of these processes is a structural material for advanced energy systems with a microstructure that is self-healing and tolerant to high doses of radiation and high temperatures.

  17. Experimental cutaneous leishmaniasis. V. Protective immunity in subclinical and self-healing infection in the mouse.

    PubMed Central

    Preston, P M; Dumonde, D C

    1976-01-01

    This study shows how infection of CBA mice with L. tropica can be manipulated so as to mimic the principal features of both subclinical and self-healing cutaneous leishmaniasis in man. CBA mice were infected with graded inocula of L. tropica promastigotes. The pattern of primary infection was found to be dependent on dose of infecting organisms: mice given low dose inocula (10(2), 10(3)) developed subclinical infections; those given high dose inocula (10(4), 10(5), 10(6)) developed overt, clinical lesions. Size and duration of lesions, and antibody production were directly proportional to dose; delayed hypersensitivity responses were inversely proportional to dose. Protective immunity to challenge infection was induced by both subclinical and clinical infection; and was manifest both during and after the healing stages of primary lesions. Protective immunity was also induced by artificial immunization with sonicated promastigotes in adjuvants but was only manifest if the challenge dose was not too large. The course of challenge infections differed depending on the method of immunization, i.e. whether by infection or artificial immunization. Lymphoid cells from immune CBA mice conferred protection on recipient syngeneic CBA mice against challenge infection; serum from immune mice did not, but suspension of immune peritoneal cells in immune serum enhanced their protective capacity. The experimental induction of protective immunity by low-dose infection, without a clinical allergic response at the site of inoculation, is of importance in designing an immunoprophylactic approach to human leishmaniasis. PMID:1261086

  18. Enhancement of oxidation resistance via a self-healing boron carbide coating on diamond particles.

    PubMed

    Sun, Youhong; Meng, Qingnan; Qian, Ming; Liu, Baochang; Gao, Ke; Ma, Yinlong; Wen, Mao; Zheng, Weitao

    2016-01-01

    A boron carbide coating was applied to diamond particles by heating the particles in a powder mixture consisting of H3BO3, B and Mg. The composition, bond state and coverage fraction of the boron carbide coating on the diamond particles were investigated. The boron carbide coating prefers to grow on the diamond (100) surface than on the diamond (111) surface. A stoichiometric B4C coating completely covered the diamond particle after maintaining the raw mixture at 1200 °C for 2 h. The contribution of the boron carbide coating to the oxidation resistance enhancement of the diamond particles was investigated. During annealing of the coated diamond in air, the priory formed B2O3, which exhibits a self-healing property, as an oxygen barrier layer, which protected the diamond from oxidation. The formation temperature of B2O3 is dependent on the amorphous boron carbide content. The coating on the diamond provided effective protection of the diamond against oxidation by heating in air at 1000 °C for 1 h. Furthermore, the presence of the boron carbide coating also contributed to the maintenance of the static compressive strength during the annealing of diamond in air. PMID:26831205

  19. Acoustic characterization of polyvinyl chloride and self-healing silicone as phantom materials

    NASA Astrophysics Data System (ADS)

    Ceh, Dennis; Peters, Terry M.; Chen, Elvis C. S.

    2015-03-01

    Phantoms are physical constructs used in procedure planning, training, medical imaging research, and machine calibration. Depending on the application, the material a phantom is made out of is very important. With ultrasound imaging, phantom materials used need to have similar acoustic properties, specifically speed of sound and attenuation, as a specified tissue. Phantoms used with needle insertion require a material with a similar tensile strength as tissue and, if possible, the ability to self heal increasing its overall lifespan. Soft polyvinyl chloride (PVC) and silicone were tested as possible needle insertion phantom materials. Acoustic characteristics were determined using a time of flight technique, where a pulse was passed through a sample contained in a water bath. The speed of sound and attenuation were both determined manually and through spectral analysis. Soft PVC was determined to have a speed of sound of approximately 1395 m/s and attenuation of 0.441 dB/cm (at 1 MHz). For the silicone mixture, the respective speed of sound values was within a range of 964.7 m/s and 1250.0 m/s with an attenuation of 0.547 dB/cm (at 1 MHz).

  20. Light-activated photocurrent degradation and self-healing in perovskite solar cells.

    PubMed

    Nie, Wanyi; Blancon, Jean-Christophe; Neukirch, Amanda J; Appavoo, Kannatassen; Tsai, Hsinhan; Chhowalla, Manish; Alam, Muhammad A; Sfeir, Matthew Y; Katan, Claudine; Even, Jacky; Tretiak, Sergei; Crochet, Jared J; Gupta, Gautam; Mohite, Aditya D

    2016-01-01

    Solution-processed organometallic perovskite solar cells have emerged as one of the most promising thin-film photovoltaic technology. However, a key challenge is their lack of stability over prolonged solar irradiation. Few studies have investigated the effect of light soaking on hybrid perovskites and have attributed the degradation in the optoelectronic properties to photochemical or field-assisted ion migration. Here we show that the slow photocurrent degradation in thin-film photovoltaic devices is due to the formation of light-activated meta-stable deep-level trap states. However, the devices can self-heal completely by resting them in the dark for <1 min or the degradation can be completely prevented by operating the devices at 0 °C. We investigate several physical mechanisms to explain the microscopic origin for the formation of these trap states, among which the creation of small polaronic states involving localized cooperative lattice strain and molecular orientations emerges as a credible microscopic mechanism requiring further detailed studies. PMID:27181192

  1. Light-activated photocurrent degradation and self-healing in perovskite solar cells

    PubMed Central

    Nie, Wanyi; Blancon, Jean-Christophe; Neukirch, Amanda J.; Appavoo, Kannatassen; Tsai, Hsinhan; Chhowalla, Manish; Alam, Muhammad A.; Sfeir, Matthew Y.; Katan, Claudine; Even, Jacky; Tretiak, Sergei; Crochet, Jared J.; Gupta, Gautam; Mohite, Aditya D.

    2016-01-01

    Solution-processed organometallic perovskite solar cells have emerged as one of the most promising thin-film photovoltaic technology. However, a key challenge is their lack of stability over prolonged solar irradiation. Few studies have investigated the effect of light soaking on hybrid perovskites and have attributed the degradation in the optoelectronic properties to photochemical or field-assisted ion migration. Here we show that the slow photocurrent degradation in thin-film photovoltaic devices is due to the formation of light-activated meta-stable deep-level trap states. However, the devices can self-heal completely by resting them in the dark for <1 min or the degradation can be completely prevented by operating the devices at 0 °C. We investigate several physical mechanisms to explain the microscopic origin for the formation of these trap states, among which the creation of small polaronic states involving localized cooperative lattice strain and molecular orientations emerges as a credible microscopic mechanism requiring further detailed studies. PMID:27181192

  2. Durability of self-healing woven glass fabric/epoxy composites

    NASA Astrophysics Data System (ADS)

    Yin, Tao; Rong, Min Zhi; Zhang, Ming Qiu; Zhao, Jian Qing

    2009-07-01

    In this work, the durability of the healing capability of self-healing woven glass fabric/epoxy laminates was investigated. The composites contained a two-component healing system with epoxy-loaded urea-formaldehyde microcapsules as the polymerizable binder and CuBr2(2-methylimidazole)4 (CuBr2(2-MeIm)4) as the latent hardener. It was found that the healing efficiency of the laminates firstly decreased with storage time at room temperature, and then leveled off for over two months. By means of a systematic investigation and particularly verification tests with dynamic mechanical analysis (DMA), diffusion of epoxy monomer from the microcapsules due to volumetric contraction of the composites during manufacturing was found to be the probable cause. The diffusing sites on the microcapsules were eventually blocked because the penetrated resin was gradually cured by the remnant amine curing agent in the composites' matrix, and eventually the healing ability was no longer reduced after a longer storage time. The results should help to develop approaches for improving the service stability of the laminates.

  3. FT-IR Investigation of Hoveyda-Grubbs'2{sup nd} Generation Catalyst in Self-Healing Epoxy Mixtures

    SciTech Connect

    Guadagno, Liberata; Naddeo, Carlo; Vittoria, Vittoria; Longo, Pasquale; Raimondo, Marialuigia; Mariconda, Annaluisa; Iannuzzo, Generoso; Russo, Salvatore

    2010-06-02

    The development of smart composites capable of self-repair on aeronautical structures is still at the planning stage owing to complex issues to overcome. A very important issue to solve concerns the components' stability of the proposed composites which are compromised at the cure temperatures necessary for good performance of the composite. In this work we analyzed the possibility to apply Hoveyda Grubbs' second generation catalyst (HG2) to develop self-healing systems. Our experimental results have shown critical issues in the use of epoxy precursors in conjunction with Hoveyda-Grubbs II metathesis catalyst. However, an appropriate curing cycle of the self-healing mixture permits to overcome the critical issues making possible high temperatures for the curing process without deactivating self-repair activity.

  4. An Analytical Model for the Probability Characteristics of a Crack Hitting an Encapsulated Self-healing Agent in Concrete

    NASA Astrophysics Data System (ADS)

    Zemskov, Serguey V.; Jonkers, Henk M.; Vermolen, Fred J.

    The present study is performed in the framework of the investigation of the potential of bacteria to act as a catalyst of the self-healing process in concrete, i.e. their ability to repair occurring cracks autonomously. Spherical clay capsules containing the healing agent (calcium lactate) are embedded in the concrete structure. Water entering a freshly formed crack releases the healing agent and activates the bacteria which will seal the crack through the process of metabolically mediated calcium carbonate precipitation. In the paper, an analytic formalism is developed for the computation of the probability that a crack hits an encapsulated particle, i.e. the probability that the self-healing process starts. Most computations are performed in closed algebraic form in the computer algebra system Mathematica which allows to perform the last step of calculations numerically with a higher accuracy.

  5. Air/water interfacial formation of freestanding, stimuli-responsive, self-healing catecholamine Janus-faced microfilms.

    PubMed

    Hong, Seonki; Schaber, Clemens F; Dening, Kirstin; Appel, Esther; Gorb, Stanislav N; Lee, Haeshin

    2014-12-01

    A catecholamine freestanding film is discovered to be spontaneously formed at the air-water interface, and the film has unique properties of robust surface adhesiveness, self-healing, and stimuli-responsive properties. The interfacial film-producing procedure is a simple single step containing polyamines and catechol(amine)s. It is found that oxygen-rich regions existing at an air-water interface greatly accelerate the catecholamine crosslinking reaction. PMID:25220108

  6. Testosterone-induced abrogation of self-healing of Plasmodium chabaudi malaria in B10 mice: mediation by spleen cells.

    PubMed Central

    Benten, W P; Bettenhaeuser, U; Wunderlich, F; Van Vliet, E; Mossmann, H

    1991-01-01

    This study investigates the suppressive effect of testosterone (Te) on the self-healing of Plasmodium chabaudi malaria in female mice of the strain C57BL/10, and, in particular, the possible role of spleen cells in mediating this Te effect. Our data show the following. (i) About 80% of B10 mice infected with 10(6) P. chabaudi-infected erythrocytes are capable of self-healing the infections. This capability is progressively impaired and finally abrogated after pretreating the B10 mice with Te for 3 weeks. (ii) The spleen is Te responsive. This becomes evident in a reduction of total spleen cells from 1.05 x 10(8) to 0.54 x 10(8) on average after Te treatment for 3 weeks. Moreover, Te treatment causes an increase in the relative proportion of CD8+ cells by about 4% and a decrease of Ig+ cells by about 4.5%, as revealed by flow cytometry. (iii) Spleen cells mediate the suppressive Te effect as revealed by adoptive transfer experiments. The percentage of self-healing mice dramatically decreases to about 8% when they receive, just prior to infection, nucleated spleen cells isolated from mice treated with Te for 3 weeks. This suppressive effect can be transferred by T cells in particular but also by non-T cells, though to a lesser extent. (iv) The adoptively transferred cells mediate their suppressive effect on self-healing only if the recipient mice receive Te during infection. Our data suggest that spleen cells become functionally changed by the Te treatment for 3 weeks. Particularly T cells, but also non-T cells, gain P. chabaudi-specific suppressive activities, and the cells require a Te-induced factor(s) to mediate these activities. PMID:1937807

  7. Air/water interfacial formation of freestanding, stimuli-responsive, self-healing catecholamine Janus-faced microfilms.

    PubMed

    Hong, Seonki; Schaber, Clemens F; Dening, Kirstin; Appel, Esther; Gorb, Stanislav N; Lee, Haeshin

    2014-12-01

    A catecholamine freestanding film is discovered to be spontaneously formed at the air-water interface, and the film has unique properties of robust surface adhesiveness, self-healing, and stimuli-responsive properties. The interfacial film-producing procedure is a simple single step containing polyamines and catechol(amine)s. It is found that oxygen-rich regions existing at an air-water interface greatly accelerate the catecholamine crosslinking reaction.

  8. Nanometrization of Lanthanide-Based Coordination Polymers.

    PubMed

    Neaime, Chrystelle; Daiguebonne, Carole; Calvez, Guillaume; Freslon, Stéphane; Bernot, Kevin; Grasset, Fabien; Cordier, Stéphane; Guillou, Olivier

    2015-11-23

    Heteronuclear lanthanide-based coordination polymers are microcrystalline powders, the luminescence properties of which can be precisely tuned by judicious choice of the rare-earth ions. In this study, we demonstrate that such materials can also be obtained as stable solutions of nanoparticles in non-toxic polyols. Bulk powders of the formula [Ln2-2x Ln'2x (bdc)3 ⋅4 H2 O]∞ (where H2 bdc denotes 1,4-benzene-dicarboxylic acid, 0≤x≤1, and Ln and Ln' denote lanthanide ions of the series La to Tm plus Y) afford nanoparticles that have been characterized by dynamic light-scattering (DLS) and transmission electron microscopy (TEM) measurements. Their luminescence properties are similar to those of the bulk materials. Stabilities versus time and versus dilution with another solvent have been studied. This study has revealed that it is possible to tune the size of the nanoparticles. This process offers a reliable means of synthesizing suspensions of nanoparticles with tunable luminescence properties and tunable size distributions in a green solvent (glycerol). The process is also extendable to other coordination polymers and other solvents (ethylene glycol, for example). It constitutes a new route for the facile solubilization of lanthanide-based coordination polymers. PMID:26471940

  9. Nanometrization of Lanthanide-Based Coordination Polymers.

    PubMed

    Neaime, Chrystelle; Daiguebonne, Carole; Calvez, Guillaume; Freslon, Stéphane; Bernot, Kevin; Grasset, Fabien; Cordier, Stéphane; Guillou, Olivier

    2015-11-23

    Heteronuclear lanthanide-based coordination polymers are microcrystalline powders, the luminescence properties of which can be precisely tuned by judicious choice of the rare-earth ions. In this study, we demonstrate that such materials can also be obtained as stable solutions of nanoparticles in non-toxic polyols. Bulk powders of the formula [Ln2-2x Ln'2x (bdc)3 ⋅4 H2 O]∞ (where H2 bdc denotes 1,4-benzene-dicarboxylic acid, 0≤x≤1, and Ln and Ln' denote lanthanide ions of the series La to Tm plus Y) afford nanoparticles that have been characterized by dynamic light-scattering (DLS) and transmission electron microscopy (TEM) measurements. Their luminescence properties are similar to those of the bulk materials. Stabilities versus time and versus dilution with another solvent have been studied. This study has revealed that it is possible to tune the size of the nanoparticles. This process offers a reliable means of synthesizing suspensions of nanoparticles with tunable luminescence properties and tunable size distributions in a green solvent (glycerol). The process is also extendable to other coordination polymers and other solvents (ethylene glycol, for example). It constitutes a new route for the facile solubilization of lanthanide-based coordination polymers.

  10. Sustainable self-healing at ultra-low temperatures in structural composites incorporating hollow vessels and heating elements

    NASA Astrophysics Data System (ADS)

    Wang, Yongjing; Pham, Duc Truong; Zhang, Zhichun; Li, Jinjun; Ji, Chunqian; Liu, Yanju; Leng, Jinsong

    2016-09-01

    Self-healing composites are able to restore their properties automatically. Impressive healing efficiencies can be achieved when conditions are favourable. On the other hand, healing might not be possible under adverse circumstances such as very low ambient temperature. Here, we report a structural composite able to maintain its temperature to provide a sustainable self-healing capability-similar to that in the natural world where some animals keep a constant body temperature to allow enzymes to stay active. The composite embeds three-dimensional hollow vessels with the purpose of delivering and releasing healing agents, and a porous conductive element to provide heat internally to defrost and promote healing reactions. A healing efficiency over 100% at around -60°C was obtained. The effects of the sheets on the interlaminar and tensile properties have been investigated experimentally. The proposed technique can be implemented in a majority of extrinsic self-healing composites to enable automatic recovery at ultra-low temperatures.

  11. The effect of a contemplative self-healing program on quality of life in women with breast and gynecologic cancers.

    PubMed

    Loizzo, Joseph J; Peterson, Janey C; Charlson, Mary E; Wolf, Emily J; Altemus, Margaret; Briggs, William M; Vahdat, Linda T; Caputo, Thomas A

    2010-01-01

    Stress-related symptoms-intense fear, avoidance, intrusive thoughts--are common among breast and gynecologic cancer patients after chemotherapy and radiation. The objective of this pilot study was to determine the impact of a 20-week contemplative self-healing program among breast and gynecologic cancer survivors on self-reported quality of life (QOL), the main outcome. Assessments were performed at the first session and at 20 weeks, including QOL (FACIT-G, FACIT subscales, SF-36), anxiety, and depression (HADS). Biologic markers of immune function were obtained. A 20-week program was implemented: the initial 8 weeks addressed open-mindfulness, social-emotional self-care, visualization, and deep breathing followed by 12 weeks of exposing stress-reactive habits and developing self-healing insights. Daily practice involved CD-guided meditation and manual contemplations. Sixty-eight women were enrolled, and 46 (68%) completed the program. Participants had significant within-patient changes on FACIT-G, improving by a mean of 6.4 points. In addition, they reported clinically important improvement in emotional and functional domains and social, role-emotional, and mental health status domains on SF-36. Biologic data revealed significant improvement in maximum AM cortisol and a reduction in resting heart rate at 20 weeks. These findings suggest a contemplative self-healing program can be effective in significantly improving QOL and reducing distress and disability among female breast and gynecologic cancer survivors.

  12. Self-healing guar gum and guar gum-multiwalled carbon nanotubes nanocomposite gels prepared in an ionic liquid.

    PubMed

    Sharma, Mukesh; Mondal, Dibyendu; Mukesh, Chandrakant; Prasad, Kamalesh

    2013-10-15

    Guar gum is a galactomannan extracted from the seed of the leguminous shrub Cyamopsis tetragonoloba. It was found to form a soft viscoelastic gel in 1-butyl-3-methylimidazolium chloride, an ionic liquid at an optimized concentration of 10%w/v. A nanocomposite gel of the gum with enhanced strength could be prepared with 0.2%w/v of multiwalled carbon nanotubes (MWCNTs) in the ionic liquid. When the gels thus prepared were subjected to surface fractures or bisected completely, they found to self-heal at room temperature without any external interventions. The self-healing process could be repeated several times. These viscoelastic gel systems showed thixotropic nature and recovery of the storage modulus with time for several cycles was observed upon rheological investigations. The interaction took place between ionic liquid, guar gum and MWCNT was studied by SEM, TEM, FT-IR, powder XRD and rheometry. The results suggested that, upon standing at room temperature development of electrostatic interactions and the van der Waals interactions among the ionic liquid molecules facilitated the formation of reversible noncovalent bonds and eventually activated the self-healing in the gel systems through appropriate chain entanglements.

  13. Sustainable self-healing at ultra-low temperatures in structural composites incorporating hollow vessels and heating elements

    PubMed Central

    Pham, Duc Truong; Zhang, Zhichun; Li, Jinjun; Ji, Chunqian; Liu, Yanju; Leng, Jinsong

    2016-01-01

    Self-healing composites are able to restore their properties automatically. Impressive healing efficiencies can be achieved when conditions are favourable. On the other hand, healing might not be possible under adverse circumstances such as very low ambient temperature. Here, we report a structural composite able to maintain its temperature to provide a sustainable self-healing capability—similar to that in the natural world where some animals keep a constant body temperature to allow enzymes to stay active. The composite embeds three-dimensional hollow vessels with the purpose of delivering and releasing healing agents, and a porous conductive element to provide heat internally to defrost and promote healing reactions. A healing efficiency over 100% at around −60°C was obtained. The effects of the sheets on the interlaminar and tensile properties have been investigated experimentally. The proposed technique can be implemented in a majority of extrinsic self-healing composites to enable automatic recovery at ultra-low temperatures. PMID:27703711

  14. A modeling study on the thermomechanical behavior of glass-ceramic and self-healing glass seals at elevated temperatures

    SciTech Connect

    Govindaraju, Nirmal; Liu, Wenning N.; Sun, Xin; Singh, Prabhakar; Singh, R.

    2009-05-15

    Hermetic gas seals are critical components for planar solid oxide fuel cells. This article focuses on comparative evaluation of a glass-ceramic developed by the Pacific Northwest National Laboratory (PNNL) and a self-healing glass seal developed by the University of Cincinnati. The stress and strain levels in the Positive electrode-Electrolyte-Negative electrode (PEN) seal in one cell stack are evaluated using a multi-physics simulation package developed at PNNL. Simulations were carried out with and without consideration of clamping force and stack body force, respectively. The results indicate that the overall stress and strain levels are dominated by the thermal expansion mismatches between the different cell components. Further, compared with glass-ceramic seal, the self-healing glass seal results in much lower steady state stress due to its much lower stiffness at the operating temperature of SOFC, and also exhibits much shorter relaxation times due to high creep rate. It is also noted that the self-healing glass seal will experience continuing creep deformation under the operating temperature of SOFC therefore resulting in possible overflow of the sealing materials. Further stopper material may need to be added to maintain its geometric stability during operation.

  15. Extended fatigue life of a catalyst-free self-healing acrylic bone cement using microencapsulated 2-octyl cyanoacrylate

    PubMed Central

    Brochu, Alice B.W.; Matthys, Oriane B.; Craig, Stephen L.; Reichert, William M.

    2014-01-01

    The tissue adhesive 2-octyl cyanoacrylate (OCA) was encapsulated in polyurethane microshells and incorporated into bone cement to form a catalyst free, self-healing bone cement comprised of all clinically approved components. The bending strength, modulus, and fatigue lifetime were investigated in accordance with ASTM and ISO standards for the testing of PMMA bone cement. The bending strength of bone cement specimens decreased with increasing wt% capsules content for capsules without or with OCA, with specimens of < 5 wt% capsule content showing minimal effect. In contrast, bone cement bending modulus was insensitive to capsule content. Load controlled fatigue testing was performed in air at room temperature on capsule free bone cement (0 wt%), bone cement with 5 wt% OCA-free capsules (5 wt% No OCA), and 5 wt% OCA-containing capsules (5 wt% OCA). Specimens were tested at a frequency of 5 Hz at maximum stresses of 90%, 80%, 70% and 50% of each specimen's bending strength until failure. The 5 wt% OCA exhibited significant self-healing at 70% and 50% of its reference strength (p < 0.05). Fatigue testing of all three specimen types in air at 22 MPa (50% of reference strength of the 5 wt% OCA specimens) showed that the cycles to failure of OCA-containing specimens was increased by two-fold compared to the OCA-free and capsule-free specimens. This study represents the first demonstration of dynamic, catalyst-free self-healing in a biomaterial formulation. PMID:24825796

  16. Extended fatigue life of a catalyst free self-healing acrylic bone cement using microencapsulated 2-octyl cyanoacrylate.

    PubMed

    Brochu, Alice B W; Matthys, Oriane B; Craig, Stephen L; Reichert, William M

    2015-02-01

    The tissue adhesive 2-octyl cyanoacrylate (OCA) was encapsulated in polyurethane microshells and incorporated into bone cement to form a catalyst free, self-healing bone cement comprised of all clinically approved components. The bending strength, modulus, and fatigue lifetime were investigated in accordance with ASTM and ISO standards for the testing of PMMA bone cement. The bending strength of bone cement specimens decreased with increasing wt % capsules content for capsules without or with OCA, with specimens of <5 wt % capsule content showing minimal effect. In contrast, bone cement bending modulus was insensitive to capsule content. Load controlled fatigue testing was performed in air at room temperature on capsule free bone cement (0 wt %), bone cement with 5 wt % OCA-free capsules (5 wt % No OCA), and 5 wt % OCA-containing capsules (5 wt % OCA). Specimens were tested at a frequency of 5 Hz at maximum stresses of 90%, 80%, 70%, and 50% of each specimen's bending strength until failure. The 5 wt % OCA exhibited significant self-healing at 70% and 50% of its reference strength (p < 0.05). Fatigue testing of all three specimen types in air at 22 MPa (50% of reference strength of the 5 wt % OCA specimens) showed that the cycles to failure of OCA-containing specimens was increased by two-fold compared with the OCA-free and capsule-free specimens. This study represents the first demonstration of dynamic, catalyst free self-healing in a biomaterial formulation. PMID:24825796

  17. Biomimetic, polymer-based microcantilever infrared sensors

    NASA Astrophysics Data System (ADS)

    Mueller, Michael Thomas

    This dissertation describes the initial development of a polymer-based, microcantilever infrared sensor. The development of the sensor is bio-inspired and based upon the long-range infrared sensor found in the pyrophilous jewel beetle Melanophila acuminata, which is able to seek out forest fires from more than 50 km away. Based on several proposed models of the infrared detector found in Melanophila acuminata, as well as published in vivo experiments, the feasibility of polymer-based infrared thermal sensors was explored and developed. Polymer materials were chosen due to their high absorptivity in the infrared range due to vibrational resonance modes characteristic of their organic bonds. Polymeric materials investigated in the course of this work include the polysaccharide and biomaterial chitin, its deacetylated derivative, chitosan, and the work-horse polymer of the semiconductor industry, novolak-resin-based photoresist. Chitin and chitosan are particularly noteworthy polymers for exploration in infrared detection due to their natural absorbance of infrared radiation near the 3 mum and 10 mum bands, which are important for the detection of the temperatures of warm engines and human body temperature, respectively. Because only limited work (primarily focused on electrodeposition) has been focused on the microscale patterning of chitosan, a photolithography process for chitosan and chitin was developed to allow the integration of the material into a variety of microelectromechanical systems processes. In addition to optical/infrared sensing, this process has a variety of potential applications in tissue engineering, protein engineering, and lab-on-a-chip devices. To demonstrate these areas of use, surface functionalization was demonstrated using bioconjugation to attach a protein to a patterned chitosan surface. Thin films of chitosan and chitin were characterized using laser profilometry to identify the effect of temperature on the film stress, and contact

  18. Tactile sensors based on conductive polymers

    NASA Astrophysics Data System (ADS)

    Castellanos-Ramos, Julian; Navas-Gonzalez, Rafael; Macicior, Haritz; Ochoteco, Estibalitz; Vidal-Verdú, Fernando

    2009-05-01

    This paper presents results from a few tactile sensors we have designed and fabricated. These sensors are based on a common approach that consists of placing a sheet of piezoresistive material on the top of a set of electrodes. If a force is exerted against the surface of the so obtained sensor, the contact area between the electrodes and the piezoresistive material changes. Therefore, the resistance at the interface changes. This is exploited as transconduction principle to measure forces and build advanced tactile sensors. For this purpose, we use a thin film of conductive polymers as the piezoresistive material. Specifically, a conductive water-based ink of these polymers is deposited by spin coating on a flexible plastic sheet, giving as a result a smooth, homogeneous and conducting thin film on it. The main interest in this procedure is it is cheap and it allows the fabrication of flexible and low cost tactile sensors. In this work we present results from sensors made with two technologies. First, we have used a Printed Circuit Board technology to fabricate the set of electrodes and addressing tracks. Then we have placed the flexible plastic sheet with the conductive polymer film on them to obtain the sensor. The result is a simple, flexible tactile sensor. In addition to these sensors on PCB, we have proposed, designed and fabricated sensors with a screen printing technology. In this case, the set of electrodes and addressing tracks are made by printing an ink based on silver nanoparticles. There is a very interesting difference with the other sensors, that consists of the use of an elastomer as insulation material between conductive layers. Besides of its role as insulator, this elastomer allows the modification of the force versus resistance relationship. It also improves the dynamic response of the sensor because it implements a restoration force that helps the sensor to relax quicker when the force is taken off.

  19. Bio-inspired multiproperty materials: strong, self-healing, and transparent artificial wood nanostructures.

    PubMed

    Merindol, Rémi; Diabang, Seydina; Felix, Olivier; Roland, Thierry; Gauthier, Christian; Decher, Gero

    2015-02-24

    Nanocomposite films possessing multiple interesting properties (mechanical strength, optical transparency, self-healing, and partial biodegradability) are discussed. We used Layer-by-Layer assembly to prepare micron thick wood-inspired films from anionic nanofibrillated cellulose and cationic poly(vinyl amine). The film growth was carried out at different pH values to obtain films of different chemical composition, whereby, and as expected, higher pH values led to a higher polycation content and also to 6 times higher film growth increments (from 9 to 55 nm per layer pair). In the pH range from 8 to 11, micron thick and optically transparent LbL films are obtained by automated dipping when dried regularly in a stream of air. Films with a size of 10 cm(2) or more can be peeled from flat surfaces; they show tensile strengths up to about 250 MPa and Young's moduli up to about 18 GPa as controlled by the polycation/polyanion ratio of the film. Experiments at different humidities revealed the plasticizing effect of water in the films and allowed reversible switching of their mechanical properties. Whereas dry films are strong and brittle (Young's modulus: 16 GPa, strain at break: 1.7%), wet films are soft and ductile (Young's modulus: 0.1 GPa, strain at break: 49%). Wet film surfaces even amalgamate upon contact to yield mechanically stable junctions. We attribute the switchability of the mechanical properties and the propensity for self-repair to changes in the polycation mobility that are brought about by the plastifying effect of water.

  20. Single conducting polymer nanowire based conductometric sensors

    NASA Astrophysics Data System (ADS)

    Bangar, Mangesh Ashok

    The detection of toxic chemicals, gases or biological agents at very low concentrations with high sensitivity and selectivity has been subject of immense interest. Sensors employing electrical signal readout as transduction mechanism offer easy, label-free detection of target analyte in real-time. Traditional thin film sensors inherently suffered through loss of sensitivity due to current shunting across the charge depleted/added region upon analyte binding to the sensor surface, due to their large cross sectional area. This limitation was overcome by use of nanostructure such as nanowire/tube as transducer where current shunting during sensing was almost eliminated. Due to their benign chemical/electrochemical fabrication route along with excellent electrical properties and biocompatibility, conducting polymers offer cost-effective alternative over other nanostructures. Biggest obstacle in using these nanostructures is lack of easy, scalable and cost-effective way of assembling these nanostructures on prefabricated micropatterns for device fabrication. In this dissertation, three different approaches have been taken to fabricate individual or array of single conducting polymer (and metal) nanowire based devices and using polymer by itself or after functionalization with appropriate recognition molecule they have been applied for gas and biochemical detection. In the first approach electrochemical fabrication of multisegmented nanowires with middle functional Ppy segment along with ferromagnetic nickel (Ni) and end gold segments for better electrical contact was studied. This multi-layered nanowires were used along with ferromagnetic contact electrode for controlled magnetic assembly of nanowires into devices and were used for ammonia gas sensing. The second approach uses conducting polymer, polypyrrole (Ppy) nanowires using simple electrophoretic alignment and maskless electrodeposition to anchor nanowire which were further functionalized with antibodies against

  1. Polymer-based separations: Synthesis and application of polymers for ionic and molecular recognition

    SciTech Connect

    Alexandratos, S.D.

    1992-01-01

    Polymer-based separations have utilized resins such as sulfonic, acrylic, and iminodiacetic acid resins and the XAD series. Selective polymeric reagents for reaction with a targeted metal ion were synthesized as polymers with two different types of functional groups, each operating on the ions through a different mechanism. There are 3 classes of DMBPs (dual mechanism bifunctional polymers). Research during this period dealing with metal ion recognition focused on two of these classes (reduction of metal ions to metal; selective complexation).

  2. Polymer-based platform for microfluidic systems

    DOEpatents

    Benett, William; Krulevitch, Peter; Maghribi, Mariam; Hamilton, Julie; Rose, Klint; Wang, Amy W.

    2009-10-13

    A method of forming a polymer-based microfluidic system platform using network building blocks selected from a set of interconnectable network building blocks, such as wire, pins, blocks, and interconnects. The selected building blocks are interconnectably assembled and fixedly positioned in precise positions in a mold cavity of a mold frame to construct a three-dimensional model construction of a microfluidic flow path network preferably having meso-scale dimensions. A hardenable liquid, such as poly (dimethylsiloxane) is then introduced into the mold cavity and hardened to form a platform structure as well as to mold the microfluidic flow path network having channels, reservoirs and ports. Pre-fabricated elbows, T's and other joints are used to interconnect various building block elements together. After hardening the liquid the building blocks are removed from the platform structure to make available the channels, cavities and ports within the platform structure. Microdevices may be embedded within the cast polymer-based platform, or bonded to the platform structure subsequent to molding, to create an integrated microfluidic system. In this manner, the new microfluidic platform is versatile and capable of quickly generating prototype systems, and could easily be adapted to a manufacturing setting.

  3. Solid polymer MEMS-based fuel cells

    DOEpatents

    Jankowski, Alan F.; Morse, Jeffrey D.

    2008-04-22

    A micro-electro-mechanical systems (MEMS) based thin-film fuel cells for electrical power applications. The MEMS-based fuel cell may be of a solid oxide type (SOFC), a solid polymer type (SPFC), or a proton exchange membrane type (PEMFC), and each fuel cell basically consists of an anode and a cathode separated by an electrolyte layer. The electrolyte layer can consist of either a solid oxide or solid polymer material, or proton exchange membrane electrolyte materials may be used. Additionally catalyst layers can also separate the electrodes (cathode and anode) from the electrolyte. Gas manifolds are utilized to transport the fuel and oxidant to each cell and provide a path for exhaust gases. The electrical current generated from each cell is drawn away with an interconnect and support structure integrated with the gas manifold. The fuel cells utilize integrated resistive heaters for efficient heating of the materials. By combining MEMS technology with thin-film deposition technology, thin-film fuel cells having microflow channels and full-integrated circuitry can be produced that will lower the operating temperature an will yield an order of magnitude greater power density than the currently known fuel cells.

  4. Polymer and small molecule based hybrid light source

    DOEpatents

    Choong, Vi-En; Choulis, Stelios; Krummacher, Benjamin Claus; Mathai, Mathew; So, Franky

    2010-03-16

    An organic electroluminescent device, includes: a substrate; a hole-injecting electrode (anode) coated over the substrate; a hole injection layer coated over the anode; a hole transporting layer coated over the hole injection layer; a polymer based light emitting layer, coated over the hole transporting layer; a small molecule based light emitting layer, thermally evaporated over the polymer based light emitting layer; and an electron-injecting electrode (cathode) deposited over the electroluminescent polymer layer.

  5. Research Trends of Soft Actuators based on Electroactive Polymers and Conducting Polymers

    NASA Astrophysics Data System (ADS)

    Kaneto, K.

    2016-04-01

    Artificial muscles (or soft actuators) based on electroactive polymers (EAPs) are attractive power sources to drive human-like robots in place of electrical motor, because they are quiet, powerful, light weight and compact. Among EAPs for soft actuators, conducting polymers are superior in strain, stress, deformation form and driving voltage compared with the other EAPs. In this paper, the research trends of EAPs and conducting polymers are reviewed by retrieval of the papers and patents. The research activity of EAP actuators showed the maximum around 2010 and somehow declining now days. The reasons for the reducing activity are found to be partly due to problems of conducting polymer actuators for the practical application. The unique characteristics of conducting polymer actuators are mentioned in terms of the basic mechanisms of actuation, creeping, training effect and shape retention under high tensile loads. The issues and limitation of conducting polymer soft actuators are discussed.

  6. Polymer waveguide couplers based on metal nanoparticle-polymer nanocomposites.

    PubMed

    Signoretto, M; Suárez, I; Chirvony, V S; Abargues, R; Rodríguez-Cantó, P J; Martínez-Pastor, J

    2015-11-27

    In this work Au nanoparticles (AuNPs) are incorporated into poly(methyl methacrylate) (PMMA) waveguides to develop optical couplers that are compatible with planar organic polymer photonics. A method for growing AuNPs (of 10 to 100 nm in size) inside the commercially available Novolak resist is proposed with the intention of tuning the plasmon resonance and the absorption/scattering efficiencies inside the patterned structures. The refractive index of the MNP-Novolak nanocomposite (MNPs: noble metal nanoparticles) is carefully analysed both experimentally and numerically in order to find the appropriate fabrication conditions (filling factor and growth time) to optimize the scattering cross section at a desired wavelength. Then the nanocomposite is patterned inside a PMMA waveguide to exploit its scattering properties to couple and guide a normal incident laser light beam along the polymer. In this way, light coupling is experimentally demonstrated in a broad wavelength range (404-780 nm). Due to the elliptical shape of the MNPs the nanocomposite demonstrates a birefringence, which enhances the coupling to the TE mode up to efficiencies of around 1%. PMID:26526708

  7. Self-healing slip pulses in dynamic rupture models due to velocity-dependent strength

    USGS Publications Warehouse

    Beeler, N.M.; Tullis, T.E.

    1996-01-01

    rise time and rupture propagation velocity depend on the choice of constitutive parameters. The second strength function is a natural log velocity-dependent form similar to constitutive laws that fit experimental rock friction data at lower velocities. Slip pulses also arise with this function. For a reasonable choice of constitutive parameters, slip pulses with this function do not propagate at speeds greater than the Raleighwave velocity. The calculated slip pulses are similar in many aspects to seismic observations of short rise time. In all cases of self-healing slip pulses, the residual stress increases with distance behind the trailing edge of the pulse so that the final stress drop is much less than the dynamic stress drop, in agreement with the model of Brune (1976) and some recent seismological observations of rupture.

  8. Digital Manufacturing of Gradient Meshed SOFC Sealing Composites with Self-Healing Capabilities

    SciTech Connect

    Kathy Lu; Christopher Story; W.T. Reynolds

    2007-12-21

    Solid oxide fuel cells (SOFC) hold great promise for clean power generation. However, high temperature stability and long term durability of the SOFC components have presented serious problems in SOFC technological advancement and commercialization. The seals of the fuel cells are the most challenging area to address. A high temperature gas seal is highly needed which is durable against cracking and gas leakage during thermal cycling and extended operation. This project investigates a novel composite seal by integrating 3D printed shape memory alloy (SMA) wires into a glass matrix. The SMA we use is TiNiHf and the glass matrix we use is SrO-La{sub 2}O{sub 3}-Al{sub 2}O{sub 3}-B{sub 2}O{sub 3}-SiO{sub 2} (SLABS). Dilatometry shows to be an extremely useful tool in providing the CTEs. It pinpoints regions of different CTEs under simulated SOFC thermal cycles for the same glass. For the studied SLABS glass system, the region with the greatest CTE mismatch between the glass seal and the adjacent components is 40-500 C, the typical heating and cooling regions for SOFCs. Even for low temperature SOFC development, this region is still present and needs to be addressed. We have demonstrated that the proposed SLABS glass has great potential in mitigating the thermal expansion mismatch issues that are limiting the operation life of SOFCs. TiNiHf alloy has been successfully synthesized with the desired particle size for the 3DP process. The TiNiHf SMA shape memory effect very desirably overlaps with the problematic low CTE region of the glass. This supports the design intent that the gradient structure transition, phase transformation toughening, and self-healing of the SMA can be utilized to mitigate/eliminate the seal problem. For the 3DP process, a new binder has been identified to match with the specific chemistry of the SMA particles. This enables us to directly print SMA particles. Neutron diffraction shows to be an extremely useful tool in providing information

  9. Self-healing gold mirrors and filters at liquid-liquid interfaces.

    PubMed

    Smirnov, Evgeny; Peljo, Pekka; Scanlon, Micheál D; Gumy, Frederic; Girault, Hubert H

    2016-04-14

    The optical and morphological properties of lustrous metal self-healing liquid-like nanofilms were systematically studied for different applications (e.g., optical mirrors or filters). These nanofilms were formed by a one-step self-assembly methodology of gold nanoparticles (AuNPs) at immiscible water-oil interfaces, previously reported by our group. We investigated a host of experimental variables and herein report their influence on the optical properties of nanofilms: AuNP mean diameter, interfacial AuNP surface coverage, nature of the organic solvent, and nature of the lipophilic organic molecule that caps the AuNPs in the interfacial nanofilm. To probe the interfacial gold nanofilms we used in situ (UV-vis-NIR spectroscopy and optical microscopy) as well as ex situ (SEM and TEM of interfacial gold nanofilms transferred to silicon substrates) techniques. The interfacial AuNP surface coverage strongly influenced the morphology of the interfacial nanofilms, and in turn their maximum reflectance and absorbance. We observed three distinct morphological regimes; (i) smooth 2D monolayers of "floating islands" of AuNPs at low surface coverages, (ii) a mixed 2D/3D regime with the beginnings of 3D nanostructures consisting of small piles of adsorbed AuNPs even under sub-full-monolayer conditions and, finally, (iii) a 3D regime characterised by the 2D full-monolayer being covered in significant piles of adsorbed AuNPs. A maximal value of reflectance reached 58% in comparison with a solid gold mirror, when 38 nm mean diameter AuNPs were used at a water-nitrobenzene interface. Meanwhile, interfacial gold nanofilms prepared with 12 nm mean diameter AuNPs exhibited the highest extinction intensities at ca. 690 nm and absorbance around 90% of the incident light, making them an attractive candidate for filtering applications. Furthermore, the interparticle spacing, and resulting interparticle plasmon coupling derived optical properties, varied significantly on replacing

  10. Self-healing gold mirrors and filters at liquid-liquid interfaces.

    PubMed

    Smirnov, Evgeny; Peljo, Pekka; Scanlon, Micheál D; Gumy, Frederic; Girault, Hubert H

    2016-04-14

    The optical and morphological properties of lustrous metal self-healing liquid-like nanofilms were systematically studied for different applications (e.g., optical mirrors or filters). These nanofilms were formed by a one-step self-assembly methodology of gold nanoparticles (AuNPs) at immiscible water-oil interfaces, previously reported by our group. We investigated a host of experimental variables and herein report their influence on the optical properties of nanofilms: AuNP mean diameter, interfacial AuNP surface coverage, nature of the organic solvent, and nature of the lipophilic organic molecule that caps the AuNPs in the interfacial nanofilm. To probe the interfacial gold nanofilms we used in situ (UV-vis-NIR spectroscopy and optical microscopy) as well as ex situ (SEM and TEM of interfacial gold nanofilms transferred to silicon substrates) techniques. The interfacial AuNP surface coverage strongly influenced the morphology of the interfacial nanofilms, and in turn their maximum reflectance and absorbance. We observed three distinct morphological regimes; (i) smooth 2D monolayers of "floating islands" of AuNPs at low surface coverages, (ii) a mixed 2D/3D regime with the beginnings of 3D nanostructures consisting of small piles of adsorbed AuNPs even under sub-full-monolayer conditions and, finally, (iii) a 3D regime characterised by the 2D full-monolayer being covered in significant piles of adsorbed AuNPs. A maximal value of reflectance reached 58% in comparison with a solid gold mirror, when 38 nm mean diameter AuNPs were used at a water-nitrobenzene interface. Meanwhile, interfacial gold nanofilms prepared with 12 nm mean diameter AuNPs exhibited the highest extinction intensities at ca. 690 nm and absorbance around 90% of the incident light, making them an attractive candidate for filtering applications. Furthermore, the interparticle spacing, and resulting interparticle plasmon coupling derived optical properties, varied significantly on replacing

  11. Supramolecular polymers constructed by crown ether-based molecular recognition.

    PubMed

    Zheng, Bo; Wang, Feng; Dong, Shengyi; Huang, Feihe

    2012-03-01

    Supramolecular polymers, polymeric systems beyond the molecule, have attracted more and more attention from scientists due to their applications in various fields, including stimuli-responsive materials, healable materials, and drug delivery. Due to their good selectivity and convenient enviro-responsiveness, crown ether-based molecular recognition motifs have been actively employed to fabricate supramolecular polymers with interesting properties and novel applications in recent years. In this tutorial review, we classify supramolecular polymers based on their differences in topology and cover recent advances in the marriage between crown ether-based molecular recognition and polymer science.

  12. Ionic-Liquid-Based Polymer Electrolytes for Battery Applications.

    PubMed

    Osada, Irene; de Vries, Henrik; Scrosati, Bruno; Passerini, Stefano

    2016-01-11

    The advent of solid-state polymer electrolytes for application in lithium batteries took place more than four decades ago when the ability of polyethylene oxide (PEO) to dissolve suitable lithium salts was demonstrated. Since then, many modifications of this basic system have been proposed and tested, involving the addition of conventional, carbonate-based electrolytes, low molecular weight polymers, ceramic fillers, and others. This Review focuses on ternary polymer electrolytes, that is, ion-conducting systems consisting of a polymer incorporating two salts, one bearing the lithium cation and the other introducing additional anions capable of plasticizing the polymer chains. Assessing the state of the research field of solid-state, ternary polymer electrolytes, while giving background on the whole field of polymer electrolytes, this Review is expected to stimulate new thoughts and ideas on the challenges and opportunities of lithium-metal batteries. PMID:26783056

  13. Ionic-Liquid-Based Polymer Electrolytes for Battery Applications.

    PubMed

    Osada, Irene; de Vries, Henrik; Scrosati, Bruno; Passerini, Stefano

    2016-01-11

    The advent of solid-state polymer electrolytes for application in lithium batteries took place more than four decades ago when the ability of polyethylene oxide (PEO) to dissolve suitable lithium salts was demonstrated. Since then, many modifications of this basic system have been proposed and tested, involving the addition of conventional, carbonate-based electrolytes, low molecular weight polymers, ceramic fillers, and others. This Review focuses on ternary polymer electrolytes, that is, ion-conducting systems consisting of a polymer incorporating two salts, one bearing the lithium cation and the other introducing additional anions capable of plasticizing the polymer chains. Assessing the state of the research field of solid-state, ternary polymer electrolytes, while giving background on the whole field of polymer electrolytes, this Review is expected to stimulate new thoughts and ideas on the challenges and opportunities of lithium-metal batteries.

  14. Self-healing of defects in CaO coatings on V-5%Cr-5%Ti in liquid lithium

    SciTech Connect

    Park, J.H.; Kassner, T.F.

    1994-11-01

    In-situ electrical resistance of CaO coatings produced on V-5%Cr-5%Ti by exposure of the alloy to liquid Li that contained 0.5-85 wt % dissolved Ca was measured as a function of time at temperatures between 250 and 600{degrees}C. Examination of the specimens after cooling to room temperature revealed no spallation, but homogeneous crazing cracks were present in the CaO coating. Additional tests to investigate the in-situ self-healing behavior of the cracks indicated that rapid healing occurred at >360{degrees}C.

  15. Ultra-compliant liquid metal electrodes with in-plane self-healing capability for dielectric elastomer actuators

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Gao, Meng; Mei, Shengfu; Han, Yanting; Liu, Jing

    2013-08-01

    The method of directly printing liquid metal films as highly conductive and super compliant electrodes for dielectric elastomer actuator (DEA) was proposed and experimentally demonstrated with working mechanisms interpreted. Such soft electrodes enable DE film to approach its maximum strain and stress at relatively low voltages. Further, its unique capability of achieving two-dimensional in-plane self-healing by merely actuating the DEA was disclosed, which would allow actuators more tolerant to fault and resilient to abusive environments. This high performance actuator has important value in a wide spectrum of situations ranging from artificial muscle, flexible electronics to smart clothing etc.

  16. Autonomous Dynamically Self-Organizing and Self-Healing Distributed Hardware Architecture - the eDNA Concept

    NASA Technical Reports Server (NTRS)

    Boesen, Michael Reibel; Madsen, Jan; Keymeulen, Didier

    2011-01-01

    This paper presents the current state of the autonomous dynamically self-organizing and self-healing electronic DNA (eDNA) hardware architecture (patent pending). In its current prototype state, the eDNA architecture is capable of responding to multiple injected faults by autonomously reconfiguring itself to accommodate the fault and keep the application running. This paper will also disclose advanced features currently available in the simulation model only. These features are future work and will soon be implemented in hardware. Finally we will describe step-by-step how an application is implemented on the eDNA architecture.

  17. Active media for tunable lasers based on hybrid polymers

    SciTech Connect

    Kopylova, T N; Eremina, N S; Vaitulevich, E A; Samsonova, L G; Maier, G V; Tel'minov, E N; Solodova, T A; Solodov, A M

    2008-02-28

    The lasing properties of rhodamine 6G (chloride and perchlorate) in synthesised hybrid polymers based on an organic polymer (methyl methacrylate with hydroxyethyl methacrylate) and an inorganic precursor (tetraethoxysilane) are studied. Rhodamine 6G samples were transversely pumped by the second harmonic of a Nd{sup 3+}:YAG laser. It is found that the active media based on hybrid polymers have a considerably longer service life compared to the active media based on organic polymers. The structure of the hybrid polymer is studied by the methods of IR Fourier spectroscopy, X-ray diffraction, and thermogravimetry. It is shown that the longer service life of hybrid-polymer active media is explained by the formation of an inorganic nanostructure network in them, which improves the thermooptic properties of the material and reduces the efficiency of thermal decomposition of active molecules. (lasers. amplifiers)

  18. Lignin-Based Triple Shape Memory Polymers.

    PubMed

    Sivasankarapillai, Gopakumar; Li, Hui; McDonald, Armando G

    2015-09-14

    Lignin-based triple shape memory polymers comprised of both permanent covalent cross-links and physical cross-links have been synthesized. A mixing phase with poly(ester-amine) and poly(ester-amide) network having two distinct glass transitions was hot mixed with more structurally homogenized methanol soluble lignin fraction by one-pot, two-step method. Triple shape properties arise from the combined effect of the glass transition of polyester copolymers and lignin and the dissociation of self-complementary hydrogen bonding and cross-link density. The percentage of recovery in each stage was investigated and it was proved that the first recovery is related with lignin-poly(ester-amine) rich network and the second recovery stage is related with lignin-poly(ester-amide) rich network. The thermal and mechanical properties of the lignin-copolymer networks were also investigated using differential scanning calorimetry and dynamic mechanical analysis.

  19. Self-healing gold mirrors and filters at liquid-liquid interfaces

    NASA Astrophysics Data System (ADS)

    Smirnov, Evgeny; Peljo, Pekka; Scanlon, Micheál D.; Gumy, Frederic; Girault, Hubert H.

    2016-03-01

    The optical and morphological properties of lustrous metal self-healing liquid-like nanofilms were systematically studied for different applications (e.g., optical mirrors or filters). These nanofilms were formed by a one-step self-assembly methodology of gold nanoparticles (AuNPs) at immiscible water-oil interfaces, previously reported by our group. We investigated a host of experimental variables and herein report their influence on the optical properties of nanofilms: AuNP mean diameter, interfacial AuNP surface coverage, nature of the organic solvent, and nature of the lipophilic organic molecule that caps the AuNPs in the interfacial nanofilm. To probe the interfacial gold nanofilms we used in situ (UV-vis-NIR spectroscopy and optical microscopy) as well as ex situ (SEM and TEM of interfacial gold nanofilms transferred to silicon substrates) techniques. The interfacial AuNP surface coverage strongly influenced the morphology of the interfacial nanofilms, and in turn their maximum reflectance and absorbance. We observed three distinct morphological regimes; (i) smooth 2D monolayers of ``floating islands'' of AuNPs at low surface coverages, (ii) a mixed 2D/3D regime with the beginnings of 3D nanostructures consisting of small piles of adsorbed AuNPs even under sub-full-monolayer conditions and, finally, (iii) a 3D regime characterised by the 2D full-monolayer being covered in significant piles of adsorbed AuNPs. A maximal value of reflectance reached 58% in comparison with a solid gold mirror, when 38 nm mean diameter AuNPs were used at a water-nitrobenzene interface. Meanwhile, interfacial gold nanofilms prepared with 12 nm mean diameter AuNPs exhibited the highest extinction intensities at ca. 690 nm and absorbance around 90% of the incident light, making them an attractive candidate for filtering applications. Furthermore, the interparticle spacing, and resulting interparticle plasmon coupling derived optical properties, varied significantly on replacing

  20. Asphaltenes-based polymer nano-composites

    DOEpatents

    Bowen, III, Daniel E

    2013-12-17

    Inventive composite materials are provided. The composite is preferably a nano-composite, and comprises an asphaltene, or a mixture of asphaltenes, blended with a polymer. The polymer can be any polymer in need of altered properties, including those selected from the group consisting of epoxies, acrylics, urethanes, silicones, cyanoacrylates, vulcanized rubber, phenol-formaldehyde, melamine-formaldehyde, urea-formaldehyde, imides, esters, cyanate esters, allyl resins.

  1. Isoindigo-based polymer photovoltaics: modifying polymer molecular structures to control the nanostructural packing motif.

    PubMed

    Kim, Yu Jin; Lee, Yun-Ji; Kim, Yun-Hi; Park, Chan Eon

    2016-07-21

    Donor molecular structures, and their packing aspects in donor:acceptor active blends, play a crucial role in the photovoltaic performance of polymer solar cells. We systematically investigated a series of isoindigo-based donor polymers within the framework of a three-dimensional (3D) crystalline motif by modifying their chemical structures, thereby affecting device performances. Although our isoindigo-based polymer series contained polymers that differed only by their alkyl side chains and/or donating units, they showed quite different nanoscale morphological properties, which resulted in significantly different device efficiencies. Notably, blends of our isoindigo-based donor polymer systems with an acceptor compound, whereby the blends had more intermixed network morphologies and stronger face-on orientations of the polymer crystallites, provided better-performing photovoltaic devices. This behavior was analyzed using atomic force microscopy (AFM) and two-dimensional grazing incidence wide angle X-ray diffraction (2D-GIWAXD). To the best of our knowledge, no correlation has been reported previously between 3D nano-structural donor crystallites and device performances, particularly for isoindigo-based polymer systems. PMID:27326694

  2. Isoindigo-based polymer photovoltaics: modifying polymer molecular structures to control the nanostructural packing motif.

    PubMed

    Kim, Yu Jin; Lee, Yun-Ji; Kim, Yun-Hi; Park, Chan Eon

    2016-07-21

    Donor molecular structures, and their packing aspects in donor:acceptor active blends, play a crucial role in the photovoltaic performance of polymer solar cells. We systematically investigated a series of isoindigo-based donor polymers within the framework of a three-dimensional (3D) crystalline motif by modifying their chemical structures, thereby affecting device performances. Although our isoindigo-based polymer series contained polymers that differed only by their alkyl side chains and/or donating units, they showed quite different nanoscale morphological properties, which resulted in significantly different device efficiencies. Notably, blends of our isoindigo-based donor polymer systems with an acceptor compound, whereby the blends had more intermixed network morphologies and stronger face-on orientations of the polymer crystallites, provided better-performing photovoltaic devices. This behavior was analyzed using atomic force microscopy (AFM) and two-dimensional grazing incidence wide angle X-ray diffraction (2D-GIWAXD). To the best of our knowledge, no correlation has been reported previously between 3D nano-structural donor crystallites and device performances, particularly for isoindigo-based polymer systems.

  3. Synthesis of Multiwalled Carbon Nanotube-Reinforced Polyborosiloxane Nanocomposites with Mechanically Adaptive and Self-Healing Capabilities for Flexible Conductors.

    PubMed

    Wu, Tongfei; Chen, Biqiong

    2016-09-14

    Intrinsic self-healing polyborosiloxane (PBS) and its multiwalled carbon nanotube (MWCNT)-reinforced nanocomposites were synthesized from hydroxyl terminated poly(dimethylsiloxane) (PDMS) and boric acid at room temperature. The formation of Si-O-B moiety in PBS was confirmed by Fourier transform infrared spectroscopy. PBS and its MWCNT-reinforced nanocomposites were found possessing water- or methanol-activated mechanically adaptive behaviors; the compressive modulus decreased substantially when exposed to water or methanol vapor and recovered their high value after the stimulus was removed. The compressive modulus was reduced by 76%, 86%, 90%, and 83% for neat PBS and its nanocomposites containing 3.0, 6.2, and 13.3 wt % MWCNTs, respectively, in water vapor, and the modulus reduction activated by methanol vapor was greater than by water vapor. MWCNTs at higher contents acted as a continuous electrical channel in PBS offering electrical conductivity, which was up to 1.21 S/cm for the nanocomposite containing 13.3 wt % MWCNTs. The MWCNT-reinforced PBS nanocomposites also showed excellent mechanically and electrically self-healing properties, moldability, and adhesion to PDMS elastomer substrate. These properties enabled a straightforward fabrication of self-repairing MWCNT/PBS electronic circuits on PDMS elastomer substrates. PMID:27530233

  4. Development and characterization of self-healing carbon fabric/ionomer composite through stitched polymeric artificial muscle

    NASA Astrophysics Data System (ADS)

    Gabriel, Mark Joseph

    Typical cracks in composite materials are hard to detect, because they may be very small or occur inside the material. This study investigates the development and characterization of carbon fiber and an ionomer, self-healing, laminate composite, enhanced with stitched artificial muscle elements. Although the carbon fiber is used as a structural reinforcement, the carbon fiber can also act as a resistive heating element in order to activate the healing elements in a Close-Then-Heal (CTH) approach. However in this study, hot air in an oven was used to activate the, SurlynRTM 8940, self-healing matrix. Artificial muscle was prepared from commercial fishing line to stitch reinforce the carbon laminate composite in the Z plane. Holes were drilled into the final composite and the muscle was stitched into the composite for active reinforcement. Differential scanning calorimetry was used to characterize the matrix and fishing line properties. The resulting smart composite was subjected to low velocity impact tests and consequential damage before healing in an oven, followed by three point bending flexure tests. Cracks in the carbon fiber reinforcement formed more easily than expected after impact because the holes were drilled to facilitate the muscle stitching. The matrix material could heal, but the reinforcement carbon could not. Several equipment issues and failures limited the amount of samples that could be created to continue testing with new parameters.

  5. Self-healing of cracks formed in Silicon-Aluminum anodes electrochemically cycled at high lithiation rates

    NASA Astrophysics Data System (ADS)

    Bhattacharya, Sandeep; Alpas, Ahmet T.

    2016-10-01

    Lithiation-induced volume changes in Si result in fracture and fragmentation of Si anodes in Li-ion batteries. This paper reports the self-healing behaviour of cracks observed in micron-sized Si particles dispersed in a ductile Al matrix of a Si-Al electrode electrochemically cycled vs. Li/Li+ using a high lithiation rate of 15.6 C. Cross-sectional high-resolution transmission electron microscopy and Raman spectroscopy revealed that an amorphous layer with a depth up to ∼100 nm was formed at the surface of Si particles. In-situ optical microscopy performed during electrochemical experiments revealed development of cracks in Si particles as the voltage decreased to 0.02 V during lithiation. Self-healing of cracks in Si particles occurred in two steps: i) arresting of the crack growth at the Si/Al interface as the surrounding Al matrix had a higher fracture toughness and thus acted as a barrier to crack propagation, and ii) closure of cracks due to compressive stresses applied to the crack faces by the amorphous zones formed on each side of the crack paths.

  6. Self-healing routing: a study in efficiency and resiliency of data delivery in wireless sensor networks

    NASA Astrophysics Data System (ADS)

    Wasilewski, Kamil; Branch, Joel W.; Lisee, Mark; Szymanski, Boleslaw K.

    2007-04-01

    This paper presents the results of implementation of a novel protocol, Self-Healing Routing (SHR) for opportunistic multi-hop wireless communication, on MicaZ sensor motes. The protocol uses broadcast communication and a prioritized transmission back-off delay scheme to empower a receiving mote to use its hop distance from the destination to decide autonomously whether to forward a packet. When severed routes are encountered, the protocol dynamically and locally re-routes packets so they traverse the surviving shortest route. We have implemented this protocol on a set of MicaZ motes as well as in the SENSE sensor network simulator and conducted field testing with different mote and network configurations. We also tested scenarios with the motes turned off (modeling permanent failures) and in simulation also temporarily off line (modeling transient failures). We compared SHR with two traditional protocols: MintRoute and AODV. The results, as shown by experimental measurement and simulations reported in the paper, demonstrate that Self-Healing Routing is an efficient fault-tolerant protocol that performs well even with spontaneous network topology changes.

  7. Experimental Study of the Aging and Self-Healing of Glass/Ceramic Sealant Used in SOFCs

    SciTech Connect

    Liu, Wenning N.; Sun, Xin; Koeppel, Brian J.; Khaleel, Mohammad A.

    2010-01-01

    High operating temperatures of solid oxide fuel cells (SOFCs) require that sealant must function at a high temperature between 600oC and 900oC and in the oxidizing and reducing environments of fuel and air. This paper describes tests to investigate the temporal evolution of the volume fraction of ceramic phases, the evolution of micro-damage, and the self-healing behavior of the glass ceramic sealant used in SOFCs. It was found that after the initial sintering process, further crystallization of the glass ceramic sealant does not stop, but slows down and reduces the residual glass content while boosting the ceramic crystalline content. Under the long-term operating environment, distinct fibrous and needle-like crystals in the amorphous phase disappeared, and smeared/diffused phase boundaries between the glass phase and ceramic phase were observed. Meanwhile, the micro-damage was induced by the cooling-down process from the operating temperature to the room temperature, which can potentially degrade the mechanical properties of the glass/ceramic sealant. The glass/ceramic sealant self-healed upon reheating to the SOFC operating temperature, which can restore the mechanical performance of the glass/ceramic sealant.

  8. Advanced self-healing asphalt composites in the pavement performance field: mechanisms at the nano level and new repairing methodologies.

    PubMed

    Agzenai, Yahya; Pozuelo, Javier; Sanz, Javier; Perez, Ignacio; Baselga, Juan

    2015-01-01

    In an effort to give a global view of this field of research, in this mini-review we highlight the most recent publications and patents focusing on modified asphalt pavements that contain certain reinforcing nanoparticles which impart desirable thermal, electrical and mechanical properties. In response to the increasing cost of asphalt binder and road maintenance, there is a need to look for alternative technologies and new asphalt composites, able to self-repair, for preserving and renewing the existing pavements. First, we will focus on the self-healing property of asphalt, the evidences that support that healing takes place immediately after the contact between the faces of a crack, and how the amount of healing can be measured in both the laboratory and the field. Next we review the hypothetical mechanisms of healing to understand the material behaviour and establish models to quantify the damage-healing process. Thereafter, we outline different technologies, nanotechnologies and methodologies used for self-healing paying particular attention to embedded micro-capsules, new nano-materials like carbon nanotubes and nano-fibres, ionomers, and microwave and induction heating processes.

  9. Synthesis of Multiwalled Carbon Nanotube-Reinforced Polyborosiloxane Nanocomposites with Mechanically Adaptive and Self-Healing Capabilities for Flexible Conductors.

    PubMed

    Wu, Tongfei; Chen, Biqiong

    2016-09-14

    Intrinsic self-healing polyborosiloxane (PBS) and its multiwalled carbon nanotube (MWCNT)-reinforced nanocomposites were synthesized from hydroxyl terminated poly(dimethylsiloxane) (PDMS) and boric acid at room temperature. The formation of Si-O-B moiety in PBS was confirmed by Fourier transform infrared spectroscopy. PBS and its MWCNT-reinforced nanocomposites were found possessing water- or methanol-activated mechanically adaptive behaviors; the compressive modulus decreased substantially when exposed to water or methanol vapor and recovered their high value after the stimulus was removed. The compressive modulus was reduced by 76%, 86%, 90%, and 83% for neat PBS and its nanocomposites containing 3.0, 6.2, and 13.3 wt % MWCNTs, respectively, in water vapor, and the modulus reduction activated by methanol vapor was greater than by water vapor. MWCNTs at higher contents acted as a continuous electrical channel in PBS offering electrical conductivity, which was up to 1.21 S/cm for the nanocomposite containing 13.3 wt % MWCNTs. The MWCNT-reinforced PBS nanocomposites also showed excellent mechanically and electrically self-healing properties, moldability, and adhesion to PDMS elastomer substrate. These properties enabled a straightforward fabrication of self-repairing MWCNT/PBS electronic circuits on PDMS elastomer substrates.

  10. Polymer Based Nanocomposites for Solar Energy Conversion

    SciTech Connect

    Shaheen, S.; Olson, D.; White, M.; Mitchell, W.; Miedaner, A.; Curtis, C.; Rumbles, G.; Gregg, B.; Ginley, D.

    2005-01-01

    Organic semiconductor-based photovoltaic devices offer the promise of low cost photovoltaic technology that can be manufactured via large-scale, roll-to-roll printing techniques. Existing organic photovoltaic devices are currently limited to solar power conversion efficiencies of 3?5%. This is because of poor overlap between the absorption spectrum of the organic chromophores and the solar spectrum, non-ideal band alignment between the donor and acceptor species, and low charge carrier mobilities. To address these issues, we are investigating the development of dendrimeric organic semiconductors that are readily synthesized with high purity. They also benefit from optoelectronic properties, such as band gap and band positions, which can be easily tuned by substituting different chemical groups into the molecule. Additionally, we are developing nanostructured oxide/conjugated polymer composite photovoltaics. These composites take advantage of the high electron mobilities attainable in oxide semiconductors and can be fabricated using low-temperature solution-based growth techniques. Here, we discuss the synthesis and preliminary device results of these novel materials and composites.

  11. Molecular cloning of protein-based polymers.

    PubMed

    Mi, Lixin

    2006-07-01

    Protein-based biopolymers have become a promising class of materials for both biomedical and pharmaceutical applications, as they have well-defined molecular weights, monomer compositions, as well as tunable chemical, biological, and mechanical properties. Using standard molecular biology tools, it is possible to design and construct genes encoding artificial proteins or protein-based polymers containing multiple repeats of amino acid sequences. This article reviews some of the traditional methods used for constructing DNA duplexes encoding these repeat-containing genes, including monomer generation, concatemerization, iterative oligomerization, and seamless cloning. A facile and versatile method, called modules of degenerate codons (MDC), which uses PCR and codon degeneracy to overcome some of the disadvantages of traditional methods, is introduced. Re-engineering of the random coil spacer domain of a bioactive protein, WPT2-3R, is used to demonstrate the utility of the MDC method. MDC re-constructed coding sequences facilitate further manipulations, such as insertion, deletion, and swapping of various sequence modules. A summary of some promising emerging techniques for synthesizing repetitive sequence-containing artificial proteins is also provided. PMID:16827576

  12. Polymer based interfaces as bioinspired 'smart skins'.

    PubMed

    De Rossi, Danilo; Carpi, Federico; Scilingo, Enzo Pasquale

    2005-11-30

    This work reports on already achieved results and ongoing research on the development of complex interfaces between humans and external environment, based on organic synthetic materials and used as smart 'artificial skins'. They are conceived as wearable and flexible systems with multifunctional characteristics. Their features are designed to mimic or augment a broad-spectrum of properties shown by biological skins of humans and/or animals. The discussion is here limited to those properties whose mimicry/augmentation is achievable with currently available technologies based on polymers and oligomers. Such properties include tactile sensing, thermal sensing/regulation, environmental energy harvesting, chromatic mimetism, ultra-violet protection, adhesion and surface mediation of mobility. Accordingly, bioinspired devices and structures, proposed as suitable functional analogous of natural architectures, are analysed. They consist of organic piezoelectric sensors, thermoelectric and pyroelectric sensors and generators, photoelectric generators, thermal and ultra-violet protection systems, electro-, photo- and thermo-chromic devices, as well as structures for improved adhesion and reduced fluid-dynamic friction.

  13. Superacid-Based Lithium Salts For Polymer Electrolytes

    NASA Technical Reports Server (NTRS)

    Nagasubramanian, Ganesan; Prakash, Surya; Shen, David H.; Surampudi, Subbarao; Olah, George

    1995-01-01

    Solid polymer electrolytes exhibiting high lithium-ion conductivities made by incorporating salts of superacids into thin films of polyethylene oxide (PEO). These and other solid-polymer electrolytes candidates for use in rechargeable lithium-based electrochemical cells. Increases in room-temperature lithium-ion conductivities of solid electrolytes desirable because they increase achievable power and energy densities.

  14. First principles calculations on oxygen vacant hydrated α-MnO2 for activating water oxidation and its self-healing mechanism.

    PubMed

    Ganesan, Kruthika; Murugan, P

    2016-08-10

    Understanding the mechanism behind water oxidation is the prime requirement for designing better catalysts for electrochemical energy devices. In this work, we demonstrate by employing first principles calculations that an initial step of water oxidation is observed to be associated with the dissociation of water dimers into hydronium and hydroxide ions, in the tunnel of a hydrated α-MnO2 compound with an oxygen vacancy. The former ion is intercalated within the network, while the latter ion occupies the oxygen vacant site and interacts strongly with the Mn atoms. Based on our calculations, the factor responsible for this dissociation of water molecules is observed to be the presence of mixed charge states of Mn atoms in the triangular lattice. Further, the coulombic attraction of a hydronium ion with a water molecule leads to the formation of a Zundel cation in the tunnel, while by dehydrogenating the adsorbed hydroxide ion, the self-healing property of the compound is achieved along with another hydronium ion as a reaction product. These cations can be exchanged with Li(+) ions. Thus, the protonic moieties formed in the tunnel of α-MnO2 leads to niche applications in the field of fuel cells and lithium ion batteries.

  15. Systematic reduction of sign errors in many-body problems: generalization of self-healing diffusion Monte Carlo to excited states

    SciTech Connect

    Reboredo, Fernando A

    2009-01-01

    A recently developed Self-Healing Diffusion Monte Carlo Algorithm [PRB {\\bf 79}, 195117 ] is extended to the calculation of excited states. The formalism is based on a excited-state fixed-node approximation and the mixed estimator of the excited-state probability density. The fixed-node ground state wave-functions of inequivalent nodal pockets are found simultaneously using a recursive approach. The decay of the wave-function into lower energy states is prevented using two methods: i) The projection of the improved trial-wave function into previously calculated eigenstates is removed. ii) The reference energy for each nodal pocket is adjusted in order to create a kink in the global fixed-node wave-function which, when locally smoothed out, increases the volume of the higher energy pockets at the expense of the lower energy ones until the energies of every pocket become equal. This reference energy method is designed to find nodal structures that are local minima for arbitrary fluctuations of the nodes within a given nodal topology. We demonstrate in a model system that the algorithm converges to many-body eigenstates in bosonic-like and fermionic cases.

  16. First principles calculations on oxygen vacant hydrated α-MnO2 for activating water oxidation and its self-healing mechanism.

    PubMed

    Ganesan, Kruthika; Murugan, P

    2016-08-10

    Understanding the mechanism behind water oxidation is the prime requirement for designing better catalysts for electrochemical energy devices. In this work, we demonstrate by employing first principles calculations that an initial step of water oxidation is observed to be associated with the dissociation of water dimers into hydronium and hydroxide ions, in the tunnel of a hydrated α-MnO2 compound with an oxygen vacancy. The former ion is intercalated within the network, while the latter ion occupies the oxygen vacant site and interacts strongly with the Mn atoms. Based on our calculations, the factor responsible for this dissociation of water molecules is observed to be the presence of mixed charge states of Mn atoms in the triangular lattice. Further, the coulombic attraction of a hydronium ion with a water molecule leads to the formation of a Zundel cation in the tunnel, while by dehydrogenating the adsorbed hydroxide ion, the self-healing property of the compound is achieved along with another hydronium ion as a reaction product. These cations can be exchanged with Li(+) ions. Thus, the protonic moieties formed in the tunnel of α-MnO2 leads to niche applications in the field of fuel cells and lithium ion batteries. PMID:27447447

  17. Interfacial Aspects of Polymer Based Photovoltaic Structures

    NASA Astrophysics Data System (ADS)

    Russell, Thomas

    2011-03-01

    Controlling thin film morphology is key in optimizing the efficiency of polymer-based photovoltaic (PV) devices. Poly(3- hexylthiophene) and [6,6]-penyl-C61 butyric acid methyl ester (P3HT:PCBM) based solar cell performance is dictated by nanostructure of the active layer, the interfaces between the active layer and the electrodes, and the P3HT chain orientation in the thin film. The above parameters were systematically studied by scanning transmission electron microscopy, scanning force microscopy, optical microscopy, grazing incident angle x- ray diffraction., dynamic secondary ion mass spectroscopy and near edge x-ray absorption fine structure analysis. The influence of thermal annealing on the morphology, interfaces and crystal structure was investigated in films that were either initially confined by two electrodes or confined by only one electrode. While the bulk morphology in these films were identical, significant differences in the concentration of components at the electrode interfaces were found, giving rise to a marked difference in performance. In addition, a model was established, based on the crystallization of the P3HTand the diffusion of the PCBM to describe the origins of the nanoscale morphology found in the active layer. The device performance parameters were quantitatively studied. In collaboration with D. Chen, H. Liu, Y. Gu and F. Lu at UMass Amherst, A. Nakahara at Kuraray Co., D. Wei at Carl Zeiss NTS LLC, D. Nordlund at SSRL and supported by the DOE-supported EFRC at the UMass Amherst (DE-PS02-08ER15944).

  18. Stimuli-responsive supramolecular polymers in aqueous solution.

    PubMed

    Ma, Xiang; Tian, He

    2014-07-15

    CONSPECTUS: Aiming to construct various novel supramolecular polymeric structures in aqueous solution beyond small supramolecular self-assembly molecules and develop functional supramolecular polymeric materials, research interest on functional supramolecular polymers has been prevailing in recent years. Supramolecular polymers are formed by bridging monomers or components together via highly directional noncovalent interactions such as hydrogen bonding, hydrophobic interaction, π-π interaction, metal-ligand coordination, electrostatic interaction, and so forth. They can be easily functionalized by employing diverse building components with specific functions besides the traditional polymeric properties, a number of which are responsive to such external stimuli as pH variance, photoirradiation, chemically or electrochemically redox with the controllable conformation or construction switching, polymerization building and rebuilding, and function adjustment reversibly owing to the reversibility of noncovalent interactions. Supramolecular polymers are "soft matters" and can be functionalized with specific properties such as morphology adjustment, controllable luminescence, shape memory, self-healing, and so forth. Supramolecular polymers constructed based on macrocycle recognition and interlocked structures represent one typical branch of the supramolecular polymer family. Cyclodextrin (CD), cucurbituril (CB), and hydrophilic calixarene derivatives are usually employed to construct hydrophilic supramolecular polymers in aqueous solution. Stimuli-responsive hydrophilic supramolecular polymers, constructed in aqueous solution particularly, can be promising candidates for mimicking biocompatible or vital functional materials. This Account mainly focuses on the recent stimuli-responsive supramolecular polymers based on the host-guest interaction in aqueous solution. We describe the hydrophilic supramolecular polymers constructed via hydrophobic effects, electrostatic

  19. Optical sensor based on sensitive polymer layer

    NASA Astrophysics Data System (ADS)

    Will, Matthias; Martan, Tomas; Müller, Ralf; Brodersen, Olaf; Mohr, Gerhard J.

    2008-11-01

    In chemical, oil, and food industries, there are still higher requirements on miniaturization of optical sensors for a concentration measurement of gases e.g. a CO2, O2, and NH3. The paper deals with development of miniaturised optical sensor for an aqueous carbon dioxide measurement using a sensitive polymer layer. The optical sensor module consists of two parts, a remission sensor and a removable layered structure (with incorporated dyed polymer) which is closely placed on the surface of a remission sensor. A dyed polymer film is used as an optical-chemical transducer working on a principle of colour changes caused by a chemical reaction of an analyte and indicator dye. A novel remission sensor module was developed for an evaluation of the spectral absorption changes of sensitive polymer layer. The remission sensor module composed of LED diodes located in a central cavity of the sensor module and PIN diodes situated around the cavity. The LEDs emit light with optimised wavelengths and irradiate the polymer film. Light response (the changes of the spectral absorption) of the irradiated polymer film is detected by PIN diodes. A colour shift is further analyzed and evaluated by electronics without using a photometer.

  20. Norbornene-Based Polymer Electrolytes for Lithium Cells

    NASA Technical Reports Server (NTRS)

    Cheung, Iris; Smart, Marshall; Prakash, Surya; Miyazawa, Akira; Hu, Jinbo

    2007-01-01

    Norbornene-based polymers have shown promise as solid electrolytes for lithium-based rechargeable electrochemical cells. These polymers are characterized as single-ion conductors. Single-ion-conducting polymers that can be used in lithium cells have long been sought. Single-ion conductors are preferred to multiple-ion conductors as solid electrolytes because concentration gradients associated with multiple-ion conduction lead to concentration polarization. By minimizing concentration polarization, one can enhance charge and discharge rates. Norbornene sulfonic acid esters have been synthesized by a ring-opening metathesis polymerization technique, using ruthenium-based catalysts. The resulting polymer structures (see figure) include sulfonate ionomers attached to the backbones of the polymer molecules. These molecules are single-ion conductors in that they conduct mobile Li+ ions only; the SO3 anions in these polymers, being tethered to the backbones, do not contribute to ionic conduction. This molecular system is especially attractive in that it is highly amenable to modification through functionalization of the backbone or copolymerization with various monomers. Polymers of this type have been blended with poly(ethylene oxide) to lend mechanical integrity to free-standing films, and the films have been fabricated into solid polymer electrolytes. These electrolytes have been demonstrated to exhibit conductivity of 2 10(exp -5)S/cm (which is high, relative to the conductivities of other solid electrolytes) at ambient temperature, plus acceptably high stability. This type of norbornene-based polymeric solid electrolyte is in the early stages of development. Inasmuch as the method of synthesis of these polymers is inherently flexible and techniques for the fabrication of the polymers into solid electrolytes are amenable to optimization, there is reason to anticipate further improvements.

  1. Cationic Polymer Based Gene Delivery: Uptake and Intracellular Trafficking

    NASA Astrophysics Data System (ADS)

    Ho, Yoonkhei; Too, Heng-Phon

    2014-04-01

    To date, low transfection efficiency remains the major drawback of polymer based gene delivery. Many cell types including stem cells, fibroblast and neurons are known to be poorly transfected with polymer based gene carriers and the high toxicity severely restrict their utility in gene delivery. Continual efforts are made to identify cellular barriers to efficient transfection as these carriers have low immunogenicity, ease of manufacturing and scalability. Here, we summarize the current status of understanding on uptake mechanism of polymer-DNA complexes (polyplexes), their endosomal escape, cytosolic transport and nuclear entry of pDNA.

  2. Maze solving automatons for self-healing of open interconnects: Modular add-on for circuit boards

    NASA Astrophysics Data System (ADS)

    Nair, Aswathi; Raghunandan, Karthik; Yaswant, Vaddi; Pillai, Sreelal S.; Sambandan, Sanjiv

    2015-03-01

    We present the circuit board integration of a self-healing mechanism to repair open faults. The electric field driven mechanism physically restores fractured interconnects in electronic circuits and has the ability to solve mazes. The repair is performed by conductive particles dispersed in an insulating fluid. We demonstrate the integration of the healing module onto printed circuit boards and the ability of maze solving. We model and perform experiments on the influence of the geometry of conductive particles as well as the terminal impedances of the route on the healing efficiency. The typical heal rate is 10 μm/s with healed route having mean resistance of 8 kΩ across a 200 micron gap and depending on the materials and concentrations used.

  3. Maze solving automatons for self-healing of open interconnects: Modular add-on for circuit boards

    SciTech Connect

    Nair, Aswathi; Raghunandan, Karthik; Yaswant, Vaddi; Sambandan, Sanjiv E-mail: ssanjiv@isu.iisc.ernet.in; Pillai, Sreelal S.

    2015-03-23

    We present the circuit board integration of a self-healing mechanism to repair open faults. The electric field driven mechanism physically restores fractured interconnects in electronic circuits and has the ability to solve mazes. The repair is performed by conductive particles dispersed in an insulating fluid. We demonstrate the integration of the healing module onto printed circuit boards and the ability of maze solving. We model and perform experiments on the influence of the geometry of conductive particles as well as the terminal impedances of the route on the healing efficiency. The typical heal rate is 10 μm/s with healed route having mean resistance of 8 kΩ across a 200 micron gap and depending on the materials and concentrations used.

  4. Atomistic simulation of graphene-based polymer nanocomposites

    NASA Astrophysics Data System (ADS)

    Rissanou, Anastassia N.; Bačová, Petra; Harmandaris, Vagelis

    2016-05-01

    Polymer/graphene nanostructured systems are hybrid materials which have attracted great attention the last years both for scientific and technological reasons. In the present work atomistic Molecular Dynamics simulations are performed for the study of graphene-based polymer nanocomposites composed of pristine, hydrogenated and carboxylated graphene sheets dispersed in polar (PEO) and nonpolar (PE) short polymer matrices (i.e., matrices containing chains of low molecular weight). Our focus is twofold; the one is the study of the structural and dynamical properties of short polymer chains and the way that they are affected by functionalized graphene sheets while the other is the effect of the polymer matrices on the behavior of graphene sheets.

  5. Lithium Ion Polymer Electrolyte Based on Pva-Pan

    NASA Astrophysics Data System (ADS)

    Genova, F. Kingslin Mary; Selvasekarapandian, S.; Rajeswari, N.; Devi, S. Siva; Karthikeyan, S.; Raja, C. Sanjeevi

    2013-07-01

    The polymer blend electrolytes based on polyvinylalcohol(PVA) and polyacrylonitrile (PAN) doped with lithium per chlorate (LiClO4) have been prepared by solution casting technique using DMF as solvent. The complex formation between blend polymer and the salt has been confirmed by Fourier transform infrared spectroscopy. The amorphous nature of the blend polymer electrolyte has been confirmed by X-ray diffraction analysis. The ionic conductivity of the prepared blend polymer electrolyte has been found by ac impedence spectroscopic analysis. The highest ionic conductivity has been found to be 5.0 X10-4 S cm -1 at room temperature for 92.5 PVA: 7.5PAN: 20 molecular wt. % of LiClO4. The effect of salt concentration on the conductivity of the blend polymer electrolyte has been discussed.

  6. Polymer composites based on gypsum matrix

    NASA Astrophysics Data System (ADS)

    Mucha, Maria; Mróz, Patrycja; Kocemba, Aleksandra

    2016-05-01

    The role of polymers as retarder additives is to prolong the workability connected with setting time of gypsum. Various cellulose derivatives, soluble in water in concentration up to 1,5% by weight were applied taking different water/binder ratio. The hydration process of calcium sulfate hemihydrate (gypsum binder) into dihydrate (gypsum plaster) was observed by setting and calorimetric techniques. Scanning electron microscopy confirmed that the gypsum microstructure was varied when polymers are used. The mechanical properties of gypsum plasters were studied by bending strength test and they are correlated with sample microstructure

  7. Functional Supramolecular Polymers*

    PubMed Central

    Aida, T.; Meijer, E.W.; Stupp, S.I.

    2012-01-01

    Supramolecular polymers can be random and entangled coils with the mechanical properties of plastics and elastomers, but with great capacity for processability, recycling, and self-healing due to their reversible monomer-to-polymer transitions. At the other extreme, supramolecular polymers can be formed by self-assembly among designed subunits to yield shape-persistent and highly ordered filaments. The use of strong and directional interactions among molecular subunits can achieve not only rich dynamic behavior but also high degrees of internal order that are not known in ordinary polymers. They can resemble, for example, the ordered and dynamic one-dimensional supramolecular assemblies of the cell cytoskeleton, and possess useful biological and electronic functions. PMID:22344437

  8. A self-healing photoinduced-deformable material fabricated by liquid crystalline elastomers using multivalent hydrogen bonds as cross-linkers.

    PubMed

    Ni, Bin; Xie, He-Lou; Tang, Jun; Zhang, Hai-Liang; Chen, Er-Qiang

    2016-08-11

    Liquid crystalline elastomers (LCEs) using multivalent hydrogen bonds as cross-linkers were successfully fabricated, which showed both self-healing and photoinduced-deformable properties. More interestingly, this LCE could be readily molded into different shapes through a versatile and efficient procedure, and the fibrous and filmy samples showed different photoinduced-deformable behavior originating from the difference in molecular orientations. PMID:27465691

  9. White Polymer Light-Emitting Diodes Based on Exciplex Electroluminescence from Polymer Blends and a Single Polymer.

    PubMed

    Liang, Junfei; Zhao, Sen; Jiang, Xiao-Fang; Guo, Ting; Yip, Hin-Lap; Ying, Lei; Huang, Fei; Yang, Wei; Cao, Yong

    2016-03-01

    In this Article, we designed and synthesized a series of polyfluorene derivatives, which consist of the electron-rich 4,4'-(9-alkyl-carbazole-3,6-diyl)bis(N,N-diphenylaniline) (TPA-Cz) in the side chain and the electron-deficient dibenzothiophene-5,5-dioxide (SO) unit in the main chain. The resulting copolymer PF-T25 that did not comprise the SO unit exhibited blue light-emission with the Commission Internationale de L'Eclairage coordinates of (0.16, 0.10). However, by physically blending PF-T25 with a blue light-emitting SO-based oligomer, a novel low-energy emission correlated to exciplex emerged due to the appropriate energy level alignment of TPA-Cz and the SO-based oligomers, which showed extended exciton lifetime as confirmed by time-resolved photoluminescent spectroscopy. The low-energy emission was also identified in copolymers consisting of SO unit in the main chain, which can effectively compensate for the high-energy emission to produce binary white light-emission. Polymer light-emitting diodes based on the exciplex-type single greenish-white polymer exhibit the peak luminous efficiency of 2.34 cd A(-1) and the maximum brightness of 12 410 cd m(-2), with Commission Internationale de L'Eclairage color coordinates (0.27, 0.39). The device based on such polymer showed much better electroluminescent stability than those based on blending films. These observations indicated that developing a single polymer with the generated exciplex emission can be a novel and effective molecular design strategy toward highly stable and efficient white polymer light-emitting diodes.

  10. Vegetable-oil-based polymers as future polymeric biomaterials.

    PubMed

    Miao, Shida; Wang, Ping; Su, Zhiguo; Zhang, Songping

    2014-04-01

    Vegetable oils are one of the most important classes of bio-resources for producing polymeric materials. The main components of vegetable oils are triglycerides - esters of glycerol with three fatty acids. Several highly reactive sites including double bonds, allylic positions and the ester groups are present in triglycerides from which a great variety of polymers with different structures and functionalities can be prepared. Vegetable-oil-based polyurethane, polyester, polyether and polyolefin are the four most important classes of polymers, many of which have excellent biocompatibilities and unique properties including shape memory. In view of these characteristics, vegetable-oil-based polymers play an important role in biomaterials and have attracted increasing attention from the polymer community. Here we comprehensively review recent developments in the preparation of vegetable-oil-based polyurethane, polyester, polyether and polyolefin, all of which have potential applications as biomaterials.

  11. Li conductivity in siloxane-based polymer electrolytes

    NASA Astrophysics Data System (ADS)

    Stacy, Eric; Fan, Fei; Feng, Hongbo; Gainaru, Catalin; Mays, Jimmy; Sokolov, Alexei

    Polymer electrolytes containing lithium ions are ideal candidates for electrochemical devices and energy storage applications. Understanding their ionic transport mechanism is the key for rational designing of highly conductive polymer matrices. Complementing dielectric spectroscopy investigations by results from rheology and differential scanning calorimetry we focused on the interplay between dynamics of lithium ions and the polymer matrix based on polysiloxane backbone. Our results demonstrate that the conductivity and the degree of decoupling between ion dynamics and structural relaxation depend strongly not only on the ions concentration, but also on the polarity and size of the polymeric side-groups. Chemical Science Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, United States.

  12. A novel supramolecular polymer gel constructed by crosslinking pillar[5]arene-based supramolecular polymers through metal-ligand interactions.

    PubMed

    Wang, Pi; Xing, Hao; Xia, Danyu; Ji, Xiaofan

    2015-12-21

    A novel heteroditopic A-B monomer was synthesized and used to construct linear supramolecular polymers utilizing pillar[5]arene-based host-guest interactions. Specifically, upon addition of Cu(2+) ions, the supramolecular polymer chains are crosslinked through metal-ligand interactions, resulting in the formation of a supramolecular polymer gel. Interestingly, this self-organized supramolecular polymer can be used as a novel fluorescent sensor for detecting Cu(2+) ions. PMID:26466511

  13. A self-sensing fiber reinforced polymer composite using mechanophore-based smart polymer

    NASA Astrophysics Data System (ADS)

    Zou, Jin; Liu, Yingtao; Chattopadhyay, Aditi; Dai, Lenore

    2015-04-01

    Polymer matrix composites (PMCs) are ubiquitous in engineering applications due to their superior mechanical properties at low weight. However, they are susceptible to damage due to their low interlaminar mechanical properties and poor heat and charge transport in the transverse direction to the laminate. Moreover, methods to inspect and ensure the reliability of composites are expensive and labor intensive. Recently, mechanophore-based smart polymer has attracted significant attention, especially for self-sensing of matrix damage in PMCs. A cyclobutane-based self-sensing approach using 1,1,1-tris (cinnamoyloxymethyl) ethane (TCE) and poly (vinyl cinnamate) (PVCi) has been studied in this paper. The self-sensing function was investigated at both the polymer level and composite laminate level. Fluorescence emissions were observed on PMC specimens subjected to low cycle fatigue load, indicating the presence of matrix cracks. Results are presented for graphite fiber reinforced composites.

  14. Molecularly Imprinted Polymer Based Sensor for the Detection of Theophylline

    NASA Astrophysics Data System (ADS)

    Braga, Guilherme S.; Paterno, Leonardo G.; Fonseca, Fernando J.; del Valle, Manel

    2011-11-01

    A molecularly imprinted polymer (MIP) impedance-based sensor was employed to detect theophylline in distilled water. To evaluate its sensibility, impedance measurements were carried out in a diluted solution of theophylline (1 mM) and distilled water using MIP and NIP (reference non-imprinted polymer) sensors. MIP showed higher sensitivity to theophylline than the NIP. This feature shows their suitability for developing an electronic tongue system for determination of methylxanthines.

  15. Gas Sensors Based on Conducting Polymers

    PubMed Central

    Bai, Hua; Shi, Gaoquan

    2007-01-01

    The gas sensors fabricated by using conducting polymers such as polyaniline (PAni), polypyrrole (PPy) and poly (3,4-ethylenedioxythiophene) (PEDOT) as the active layers have been reviewed. This review discusses the sensing mechanism and configurations of the sensors. The factors that affect the performances of the gas sensors are also addressed. The disadvantages of the sensors and a brief prospect in this research field are discussed at the end of the review.

  16. Microparticles prepared from sulfenamide-based polymers

    PubMed Central

    D’Mello, Sheetal R.; Yoo, Jun; Bowden, Ned B.; Salem, Aliasger K.

    2015-01-01

    Polysulfenamides (PSN), with a SN linkage (RSNR2) along the polymer backbone, are a new class of biodegradable and biocompatible polymers. These polymers were unknown prior to 2012 when their synthesis and medicinally relevant properties were reported. The aim of this study was to develop microparticles as a controlled drug delivery system using polysulfenamide as the matrix material. The microparticles were prepared by a water-in-oil-in-water double emulsion solvent evaporation method. For producing drug-loaded particles, FITC-dextran was used as a model hydrophilic compound. At the optimal formulation conditions, the external morphology of the PSN microparticles was examined by scanning electron microscopy to show the formation of smooth-surfaced spherical particles with low polydispersity. The microparticles had a net negative surface charge (−23 mV) as analyzed by the zetasizer. The drug encapsulation efficiency of the particles and the drug loading were found to be dependent on the drug molecular weight, amount of FITC-dextran used in fabricating FITC-dextran loaded microparticles, concentration of PSN and surfactant, and volume of the internal and external water phases. FITC-dextran was found to be distributed throughout the PSN microparticles and was released in an initial burst followed by more continuous release over time. Confocal laser scanning microscopy was used to qualitatively observe the cellular uptake of PSN microparticles and indicated localization of the particles in both the cytoplasm and the nucleus. PMID:23862723

  17. Estimation of critical conditions of polymers based on monitoring the polymer recovery.

    PubMed

    Bhati, S S; Macko, T; Brüll, R

    2016-06-17

    Liquid chromatography at critical conditions (LCCC) is a very attractive chromatographic technique on the border between the size exclusion and liquid adsorption mode of the liquid chromatography. The strong interest in LCCC arises from the fact that it is well suited to analyze the block lengths in segmented copolymers or the heterogeneities with regard to end groups present, for example, in functionalized polymers e.g., telechelics. In this paper a new method for identification of the critical conditions of synthetic polymers is proposed, which requires only one polymer sample with higher molar mass. The method is based on monitoring the recovery of the polymer sample from a column. The composition of the mobile phase is modified until the polymer sample is fully recovered from the column. The corresponding composition of the mobile phase is composition corresponding to LCCC. This new method was applied for the determination of critical conditions for polyethylene, syndiotactic polypropylene and isotactic polypropylene. The results of the new method will be compared to those of classical approaches and advantages will be pointed out.

  18. Terthiophene-based D-A polymer with an asymmetric arrangement of alkyl chains that enables efficient polymer solar cells.

    PubMed

    Hu, Huawei; Jiang, Kui; Yang, Guofang; Liu, Jing; Li, Zhengke; Lin, Haoran; Liu, Yuhang; Zhao, Jingbo; Zhang, Jie; Huang, Fei; Qu, Yongquan; Ma, Wei; Yan, He

    2015-11-11

    We report a series of difluorobenzothiadizole (ffBT) and oligothiophene-based polymers with the oligothiophene unit being quaterthiophene (T4), terthiophene (T3), and bithiophene (T2). We demonstrate that a polymer based on ffBT and T3 with an asymmetric arrangement of alkyl chains enables the fabrication of 10.7% efficiency thick-film polymer solar cells (PSCs) without using any processing additives. By decreasing the number of thiophene rings per repeating unit and thus increasing the effective density of the ffBT unit in the polymer backbone, the HOMO and LUMO levels of the T3 polymers are significantly deeper than those of the T4 polymers, and the absorption onset of the T3 polymers is also slightly red-shifted. For the three T3 polymers obtained, the positions and size of the alkyl chains play a critical role in achieving the best PSC performances. The T3 polymer with a commonly known arrangement of alkyl chains (alkyl chains sitting on the first and third thiophenes in a mirror symmetric manner) yields poor morphology and PSC efficiencies. Surprisingly, a T3 polymer with an asymmetric arrangement of alkyl chains (which is later described as having an "asymmetric bi-repeating unit") enables the best-performing PSCs. Morphological studies show that the optimized ffBT-T3 polymer forms a polymer:fullerene morphology that differs significantly from that obtained with T4-based polymers. The morphological changes include a reduced domain size and a reduced extent of polymer crystallinity. The change from T4 to T3 comonomer units and the novel arrangement of alkyl chains in our study provide an important tool to tune the energy levels and morphological properties of donor polymers, which has an overall beneficial effect and leads to enhanced PSC performance.

  19. Drug Delivery Vehicles Based on Albumin-Polymer Conjugates.

    PubMed

    Jiang, Yanyan; Stenzel, Martina

    2016-06-01

    Albumin has been a popular building block to create nanoparticles for drug delivery purposes. The performance of albumin as a drug carrier can be enhanced by combining protein with polymers, which allows the design of carriers to encompass a broader spectrum of drugs while features unique to synthetic polymers such as stimuli-responsiveness are introduced. Nanoparticles based on polymer-albumin hybrids can be divided into two classes: one that carries album as a bioactive surface coating and the other that uses albumin as biocompatible, although nonbioactive, building block. Nanoparticles with bioactive albumin surface coating can either be prepared by self-assembly of albumin-polymer conjugates or by postcoating of existing nanoparticles with albumin. Albumin has also been used as building block, either in its native or denatured form. Existing albumin nanoparticles are coated with polymers, which can influence the degradation of albumin or impact on the drug release. Finally, an alternative way of using albumin by denaturing the protein to generate a highly functional chain, which can be modified with polymer, has been presented. These albumin nanoparticles are designed to be extremely versatile so that they can deliver a wide variety of drugs, including traditional hydrophobic drugs, metal-based drugs and even therapeutic proteins and siRNA.

  20. Electroactive polymer gels based on epoxy resin

    NASA Astrophysics Data System (ADS)

    Samui, A. B.; Jayakumar, S.; Jayalakshmi, C. G.; Pandey, K.; Sivaraman, P.

    2007-04-01

    Five types of epoxy gels have been synthesized from common epoxy resins and hardeners. Fumed silica and nanoclay, respectively, were used as fillers and butyl methacrylate/acrylamide were used as monomer(s) for making interpenetrating polymer networks (IPNs) in three compositions. Swelling study, tensile property evaluation, dynamic mechanical thermal analysis, thermo-gravimetric analysis, scanning electron microscopy and electroactive property evaluation were done. The gels have sufficient mechanical strength and the time taken for bending to 20° was found to be 22 min for forward bias whereas it was just 12 min for reverse bias.