A new family of transparent,biocompatible,self-adhesive,and self-healing elastomer has been developed by a convenient and efficient one-pot reaction between poly(acrylic acid)(PAA)and hydroxyl-terminated polydimethyls...A new family of transparent,biocompatible,self-adhesive,and self-healing elastomer has been developed by a convenient and efficient one-pot reaction between poly(acrylic acid)(PAA)and hydroxyl-terminated polydimethylsiloxane(PDMSOH).The condensation reaction between PAA and PDMS-OH has been confirmed by attenuated total reflection Fourier transform infrared(ATR-FTIR)spectra.The prepared PAA-PDMS elastomers possess robust mechanical strength and strong adhesiveness to human skin,and they have fast self-healing ability at room temperature(in^10 s with the efficiency of 98%).Specifically,strain sensors were fabricated by assembling PAA-PDMS as packaging layers and polyetherimide-reduced graphene oxide(PEI-rGO)as strain-sensing layers.The PAA-PDMS/PEI-rGO sensors are stably and reliably responsive to slight physical deformations,and they can be attached onto skin directly to monitor the body’s motions.Meanwhile,strain sensors can self-heal quickly and completely,and they can be reused for the motion detecting after shallowly scratching the surface.This work provides new opportunities to manufacture high performance self-adhesive and self-healing materials.展开更多
Triboelectric nanogenerators(TENGs)based on conjunctive effects of contact electrification(CE)and electrostatic induction are emerging as a new mechanical energy harvesting and sensing technique for promising applicat...Triboelectric nanogenerators(TENGs)based on conjunctive effects of contact electrification(CE)and electrostatic induction are emerging as a new mechanical energy harvesting and sensing technique for promising applications in smart wearables,Internet of Things(IoTs),etc.The surface microstructure of a flexible triboelectric material for the increase of surface area is a common strategy for performance enhancement of TENGs,but the real roles of surface microstructures on their output performance are still not explicit due to the lack of suitable analysis tool and rational experimental design.Taking advantages of the surface-sensitive characteristic of CE effect,this work exploited and developed the electric signal patterns generated by single impact of TENGs as a kind of CE spectrum to analyze and speculate the real roles of surface microstructures of flexible triboelectric materials on the output performance of TENGs.Firstly,four different kinds of surface microstructures,namely planar surface(PS)and three combinations of two basic surface microstructures,i.e.,micro lens arrays(MLAs),fabric textures(FTs),and hierarchical structures of MLAs on FTs(MLA/FTs),were elaborately designed and introduced for an identical triboelectric material(i.e.,silicone elastomer)by a(micro)molding synthesis route.Then they were used for assembly of TENGs based on vertical contact mode to conduct performance evaluation under the same triggering conditions.Through systematic analysis and comparison of their highly repeatable CE spectra by programmed machine,it was found that the surface microstructure for a flexible triboelectric material to maximally enhance the output performance of a TENG shall achieve a positive synergistic effect of increasing triboelectric charge density,effective contact area and contacting/separating velocity,rather than simple increase of its surface area.展开更多
Since the fouling-releasing ability of silicone elastomers increased as their modulus decreases, we designed and prepared composites with embedded tiny NaC1 crytals that were soluble after their immersion in water, re...Since the fouling-releasing ability of silicone elastomers increased as their modulus decreases, we designed and prepared composites with embedded tiny NaC1 crytals that were soluble after their immersion in water, resulting in water-filled porous elastomers. The scanning electron microscope images confirmed such a designed water-filling porous structure. The existence of many micro-drops of water in these specially designed elastomers decreased the shear storage modulus and increased the loss factors. The decrease of shear modulus plays a leading role here and is directly related to a lower critical peeling-off stress of a pseudo-barnacle on them. Therefore, such a novel preparation with cheap salts instead of an expensive silicone provides a better way to make fouling-release paints with a lower modulus, a lower critical peeling-off stress and a better fouling-release property without a significant decrease of the cross-linking density.展开更多
3D printing silicone elastomer has demonstrated great potential in diverse areas such as medical devices,flexible electronics and soft robotics.It is of great value to investigate how to improve the mechanical propert...3D printing silicone elastomer has demonstrated great potential in diverse areas such as medical devices,flexible electronics and soft robotics.It is of great value to investigate how to improve the mechanical properties,including tensile strength and elongation at break of printed parts.In this work,a light curing system that can be applied in silicone elastomer 3D printing is explored,which is composed of vinyl terminated polysiloxane as the macromer and thiol containing polysiloxane as the crosslinking agent,and a chain extension reaction is also introduced into this light curing system via the addition of the chain extender dithiol molecules,and a light curing system accompanied with chain extension is designed and realized based on the thiol-ene click reaction mechanism.After reinforced with silica fillers,the obtained light curing system can endow the light curing silicone elastomer with better mechanical properties under the condition of a lower viscosity of the precursor,the tensile strength and elongation at break can reach 525.5 k Pa and 601%,respectively.This light curing system provides a feasible method to solve the contradiction between the viscosity of the precursor and the mechanical properties of the light curing elastomer in the digital light processing(DLP)3D printing field.展开更多
The delicate serpentine structures are widely used in high-performance stretchable electronics over the past decade.The metal interconnects encapsulated in biocompatible polymer Parylene-C film is a superior choice fo...The delicate serpentine structures are widely used in high-performance stretchable electronics over the past decade.The metal interconnects encapsulated in biocompatible polymer Parylene-C film is a superior choice for long-term implantation in vivo,especially as neural interface to acquire electrophysiological signals or apply electrical stimulation.To avoid the physical contact damages from the neural tissues such as the brain or peripheral nerves,serpentine interconnects are utilized as stretchable electrodes and usually bonded to the soft elastomer substrate.The adhesion strength between the serpentine interconnects and the elastomer substrate becomes a considerable issue to ensure reliability and structural integrity.In this paper,the stretchable Parylene-C electrodes can be transfer printed onto arbitrary elastomer substrates by a thin layer of silicone rubber adhesive with low modulus for electrocorticogram(ECoG)recording.Mechanical simulation of serpentine structures consisting of same periodic arcs and different straight segments is investigated by uniaxial stretching.Then,the elastic stretchability of serpentine electrodes is further studied by simulation and experiments.After 5000 repetitive stretching cycles,the electrochemical impedance of microelectrodes remains in steady states.These results prove that the silicone rubber adhesive facilitates the interfacial bonding in the structure of stretchable electrodes as the compliant and reliable neural interface.展开更多
A large number of insulation/dielectric failures in power systems are related to thermally-induced dielectrical breakdown,also known as‘thermal breakdown’,at higher operating temperatures.In this work,the thermal br...A large number of insulation/dielectric failures in power systems are related to thermally-induced dielectrical breakdown,also known as‘thermal breakdown’,at higher operating temperatures.In this work,the thermal breakdown behavior of typical silicone formulations,used as dielectrics in stretchable electronic devices,is analyzed at practically relevant operating temperatures ranging from 20℃ to 80℃.An effective way of delaying the thermal breakdown of insulating materials is to blend micro-or nano-sized inorganic particles with high thermal conductivity,to dissipate better any losses generated during energy transduction.Therefore,two types of commercial silicone formulations,blended with two types of rutile hydrophobic,high-dielectric TiO_(2) fillers,are investigated in relation to their dielectric properties,namely,relative permittivity,the dissipation factor,and electrical breakdown strength.The breakdown strengths of these silicone composites are subsequently evaluated using Weibull analysis,which indicates a negative correlation between temperature and shape parameter for all compositions,thus illustrating that the homogeneity of the samples decreases in line with temperature,but the breakdown strengths nevertheless increase initially due to the trapping effect from the high-permittivity fillers.展开更多
Soft silicone films have garnered a great deal of interest for use in dielectric elastomer transducers due to their excellent properties,including high elongation to rupture,low viscoelasticity,and broad application t...Soft silicone films have garnered a great deal of interest for use in dielectric elastomer transducers due to their excellent properties,including high elongation to rupture,low viscoelasticity,and broad application temperature range.However,silicone films generally have higher stiffness and lower dielectric strength than VHB acrylic elastomers,which limits the achievable actuation strain.Devices based on silicone dielectric elastomers always experience high rates of premature dielectric failure when operated at high strains.The premature failure is characterized by the loss of functionality or mechanical rupture of the material when operated below the material’s dielectric strength and elongation to rupture.The use is reported of ultrathin coatings of single-walled carbon nanotubes(SWNTs)as the compliant electrodes,which can overcome the issue of premature failure.The self-clearing of the SWNT electrodes in the event of localized dielectric breakdown improves the apparent dielectric strength of the material by isolating the regions of reduced dielectric strength.The actuators may be operated at higher than 50%area strain with reasonably long lifetimes.High strains were measured between-40 and 80℃and in a broad frequency range up to 100 Hz.The fault tolerance introduced by the SWNT electrodes should broaden the application scope of silicone dielectric elastomers.展开更多
Silicone elastomers have been heavily investigated as candidates for the flexible insulator material in dielectric elastomer transducers and are as such almost ideal candidates because of their inherent softness and c...Silicone elastomers have been heavily investigated as candidates for the flexible insulator material in dielectric elastomer transducers and are as such almost ideal candidates because of their inherent softness and compliance.However,silicone elastomers suffer from low dielectric permittivity.This shortcoming has been attempted optimized through different approaches during recent years.Material optimization with the sole purpose of increasing the dielectric permittivity may lead to the introduction of problematic phenomena such as premature electrical breakdown due to high leakage currents of the thin elastomer film.Within this work,electrical breakdown phenomena of various types of permittivity-enhanced silicone elastomers are investigated.Results showed that different types of polymer backbone chemistries lead to differences in electrical breakdown patterns,which were revealed through SEM imaging.This may pave the way towards a better understanding of electrical breakdown mechanisms of dielectric elastomers and potentially lead to materials with increased electrical breakdown strengths.展开更多
基金supported by the National Science Funds for Excellent Young Scholars of China (Grant No. 61822106)National Science Funds for Creative Research Groups of China (Grant No. 61421002)+1 种基金Natural Science Foundation of China (Grant No. 61671115)Opening Project of State Key Laboratory of Polymer Materials Engineering (Sichuan University) (Grant No. sklpme 2018-4-28)
文摘A new family of transparent,biocompatible,self-adhesive,and self-healing elastomer has been developed by a convenient and efficient one-pot reaction between poly(acrylic acid)(PAA)and hydroxyl-terminated polydimethylsiloxane(PDMSOH).The condensation reaction between PAA and PDMS-OH has been confirmed by attenuated total reflection Fourier transform infrared(ATR-FTIR)spectra.The prepared PAA-PDMS elastomers possess robust mechanical strength and strong adhesiveness to human skin,and they have fast self-healing ability at room temperature(in^10 s with the efficiency of 98%).Specifically,strain sensors were fabricated by assembling PAA-PDMS as packaging layers and polyetherimide-reduced graphene oxide(PEI-rGO)as strain-sensing layers.The PAA-PDMS/PEI-rGO sensors are stably and reliably responsive to slight physical deformations,and they can be attached onto skin directly to monitor the body’s motions.Meanwhile,strain sensors can self-heal quickly and completely,and they can be reused for the motion detecting after shallowly scratching the surface.This work provides new opportunities to manufacture high performance self-adhesive and self-healing materials.
基金supported by the National Natural Science Foundation of China(No.52103278).
文摘Triboelectric nanogenerators(TENGs)based on conjunctive effects of contact electrification(CE)and electrostatic induction are emerging as a new mechanical energy harvesting and sensing technique for promising applications in smart wearables,Internet of Things(IoTs),etc.The surface microstructure of a flexible triboelectric material for the increase of surface area is a common strategy for performance enhancement of TENGs,but the real roles of surface microstructures on their output performance are still not explicit due to the lack of suitable analysis tool and rational experimental design.Taking advantages of the surface-sensitive characteristic of CE effect,this work exploited and developed the electric signal patterns generated by single impact of TENGs as a kind of CE spectrum to analyze and speculate the real roles of surface microstructures of flexible triboelectric materials on the output performance of TENGs.Firstly,four different kinds of surface microstructures,namely planar surface(PS)and three combinations of two basic surface microstructures,i.e.,micro lens arrays(MLAs),fabric textures(FTs),and hierarchical structures of MLAs on FTs(MLA/FTs),were elaborately designed and introduced for an identical triboelectric material(i.e.,silicone elastomer)by a(micro)molding synthesis route.Then they were used for assembly of TENGs based on vertical contact mode to conduct performance evaluation under the same triggering conditions.Through systematic analysis and comparison of their highly repeatable CE spectra by programmed machine,it was found that the surface microstructure for a flexible triboelectric material to maximally enhance the output performance of a TENG shall achieve a positive synergistic effect of increasing triboelectric charge density,effective contact area and contacting/separating velocity,rather than simple increase of its surface area.
文摘Since the fouling-releasing ability of silicone elastomers increased as their modulus decreases, we designed and prepared composites with embedded tiny NaC1 crytals that were soluble after their immersion in water, resulting in water-filled porous elastomers. The scanning electron microscope images confirmed such a designed water-filling porous structure. The existence of many micro-drops of water in these specially designed elastomers decreased the shear storage modulus and increased the loss factors. The decrease of shear modulus plays a leading role here and is directly related to a lower critical peeling-off stress of a pseudo-barnacle on them. Therefore, such a novel preparation with cheap salts instead of an expensive silicone provides a better way to make fouling-release paints with a lower modulus, a lower critical peeling-off stress and a better fouling-release property without a significant decrease of the cross-linking density.
基金the National Natural Science Foundation of China(Nos.52173054,51903009,51673014 and 51525301)the Fundamental Research Funds for the Central Universities(Nos.buctrc201923 and JD2009)。
文摘3D printing silicone elastomer has demonstrated great potential in diverse areas such as medical devices,flexible electronics and soft robotics.It is of great value to investigate how to improve the mechanical properties,including tensile strength and elongation at break of printed parts.In this work,a light curing system that can be applied in silicone elastomer 3D printing is explored,which is composed of vinyl terminated polysiloxane as the macromer and thiol containing polysiloxane as the crosslinking agent,and a chain extension reaction is also introduced into this light curing system via the addition of the chain extender dithiol molecules,and a light curing system accompanied with chain extension is designed and realized based on the thiol-ene click reaction mechanism.After reinforced with silica fillers,the obtained light curing system can endow the light curing silicone elastomer with better mechanical properties under the condition of a lower viscosity of the precursor,the tensile strength and elongation at break can reach 525.5 k Pa and 601%,respectively.This light curing system provides a feasible method to solve the contradiction between the viscosity of the precursor and the mechanical properties of the light curing elastomer in the digital light processing(DLP)3D printing field.
基金supported by the National Key R&D Program of China under grant 2017YFB1002501the National Natural Science Foundation of China(No.61728402,No.31600781 and 31972929)+2 种基金Research Program of Shanghai Science and Technology Committee(17JC1402800,17JC1400202 and 19ZR1475000)Program of Shanghai Academic/Technology Research Leader(18XD1401900)Interdisciplinary Program of Shanghai Jiao Tong University(YG2016MS06).
文摘The delicate serpentine structures are widely used in high-performance stretchable electronics over the past decade.The metal interconnects encapsulated in biocompatible polymer Parylene-C film is a superior choice for long-term implantation in vivo,especially as neural interface to acquire electrophysiological signals or apply electrical stimulation.To avoid the physical contact damages from the neural tissues such as the brain or peripheral nerves,serpentine interconnects are utilized as stretchable electrodes and usually bonded to the soft elastomer substrate.The adhesion strength between the serpentine interconnects and the elastomer substrate becomes a considerable issue to ensure reliability and structural integrity.In this paper,the stretchable Parylene-C electrodes can be transfer printed onto arbitrary elastomer substrates by a thin layer of silicone rubber adhesive with low modulus for electrocorticogram(ECoG)recording.Mechanical simulation of serpentine structures consisting of same periodic arcs and different straight segments is investigated by uniaxial stretching.Then,the elastic stretchability of serpentine electrodes is further studied by simulation and experiments.After 5000 repetitive stretching cycles,the electrochemical impedance of microelectrodes remains in steady states.These results prove that the silicone rubber adhesive facilitates the interfacial bonding in the structure of stretchable electrodes as the compliant and reliable neural interface.
基金supported by the Independent Research Fund Denmark.
文摘A large number of insulation/dielectric failures in power systems are related to thermally-induced dielectrical breakdown,also known as‘thermal breakdown’,at higher operating temperatures.In this work,the thermal breakdown behavior of typical silicone formulations,used as dielectrics in stretchable electronic devices,is analyzed at practically relevant operating temperatures ranging from 20℃ to 80℃.An effective way of delaying the thermal breakdown of insulating materials is to blend micro-or nano-sized inorganic particles with high thermal conductivity,to dissipate better any losses generated during energy transduction.Therefore,two types of commercial silicone formulations,blended with two types of rutile hydrophobic,high-dielectric TiO_(2) fillers,are investigated in relation to their dielectric properties,namely,relative permittivity,the dissipation factor,and electrical breakdown strength.The breakdown strengths of these silicone composites are subsequently evaluated using Weibull analysis,which indicates a negative correlation between temperature and shape parameter for all compositions,thus illustrating that the homogeneity of the samples decreases in line with temperature,but the breakdown strengths nevertheless increase initially due to the trapping effect from the high-permittivity fillers.
基金financial support from the General Motor Corporation,and the University of California Discovery Program.
文摘Soft silicone films have garnered a great deal of interest for use in dielectric elastomer transducers due to their excellent properties,including high elongation to rupture,low viscoelasticity,and broad application temperature range.However,silicone films generally have higher stiffness and lower dielectric strength than VHB acrylic elastomers,which limits the achievable actuation strain.Devices based on silicone dielectric elastomers always experience high rates of premature dielectric failure when operated at high strains.The premature failure is characterized by the loss of functionality or mechanical rupture of the material when operated below the material’s dielectric strength and elongation to rupture.The use is reported of ultrathin coatings of single-walled carbon nanotubes(SWNTs)as the compliant electrodes,which can overcome the issue of premature failure.The self-clearing of the SWNT electrodes in the event of localized dielectric breakdown improves the apparent dielectric strength of the material by isolating the regions of reduced dielectric strength.The actuators may be operated at higher than 50%area strain with reasonably long lifetimes.High strains were measured between-40 and 80℃and in a broad frequency range up to 100 Hz.The fault tolerance introduced by the SWNT electrodes should broaden the application scope of silicone dielectric elastomers.
基金The Danish Research Council is greatly acknowledged for the funding provided for Frederikke Bahrt Madsen.
文摘Silicone elastomers have been heavily investigated as candidates for the flexible insulator material in dielectric elastomer transducers and are as such almost ideal candidates because of their inherent softness and compliance.However,silicone elastomers suffer from low dielectric permittivity.This shortcoming has been attempted optimized through different approaches during recent years.Material optimization with the sole purpose of increasing the dielectric permittivity may lead to the introduction of problematic phenomena such as premature electrical breakdown due to high leakage currents of the thin elastomer film.Within this work,electrical breakdown phenomena of various types of permittivity-enhanced silicone elastomers are investigated.Results showed that different types of polymer backbone chemistries lead to differences in electrical breakdown patterns,which were revealed through SEM imaging.This may pave the way towards a better understanding of electrical breakdown mechanisms of dielectric elastomers and potentially lead to materials with increased electrical breakdown strengths.
