弱溶胀作用制备的模量异质微结构纤维膜应变传感器

随着柔性可穿戴电子设备的普及,制备具有高力学弹性、优异力电响应性能的电阻型可拉伸应变传感器颇具研究意义。其中,双层结构的电阻型应变传感器因为优异的应变传感性能近年来备受关注。然而,在应用过程中,导电层通常会产生不可逆的贯穿式微裂纹,造成应变作用下电阻的不稳定增长,限制了其在实际场景中的应用。基于“微裂纹”传感机理,通过同轴纺丝的加工方法在低模量的热塑性聚氨酯(TPU)取向电纺纤维膜表面引入高模量的羧基化聚苯乙烯微球(PSNSs)形成模量异质微结构,这种微结构可以在应变过程中有效耗散局部应力,从而有效抑制贯穿式微裂纹的扩展。利用物理/化学作用对复合纤维膜进行界面作用改性处理,通过调控PSNSs分散体系的浓度及溶剂配比来构筑不同表面特性的异质模量微结构,以便调节材料的应变响应行为。所制备的可拉伸导电薄膜能够实现快速应变响应与回复(49.7ms/62.5ms),并且在0~30%应变范围内保持线性的相对电阻-应变响应特征(应变敏感因子GF=257)。

Enhanced Ion-Selective Diffusion Achieved by Supramolecular Interaction for High Thermovoltage and Thermal Stability

Thermoelectric(TE)generators capable of converting thermal energy into applicable electricity have gained great popularity among emerging energy conversion technologies.Biopolymer-based ionic thermoelectric(i-TE)materials are promising candidates for energy conversion systems because of their wide sources,innocuity,and low manufacturing cost.However,common physically crosslinked biopolymer gels induced by single hydrogen bonding or hydrophobic interaction suffer from low differential thermal voltage and poor thermodynamic stability.Here,we develop a novel i-TE gel with supramolecular structures through multiple noncovalent interactions between ionic liquids(ILs)and gelatin molecular chains.The thermopower and thermoelectric power factor of the ionic gels are as high as 2.83 mV K-1 and 18.33μW m^(-1)K^(-2),respectively.The quasi-solid-state gelatin-[EMIM]DCA i-TE cells achieve ultrahigh 2 h output energy density(E_(2h)=9.9 mJ m^(-2))under an optimal temperature range.Meanwhile,the remarkable stability of the supramolecular structure provides the i-TE hydrogels with a thermal stability of up to 80℃.It breaks the limitation that biopolymer-based i-TE gels can only be applied in the low temperature range and enables biopolymer-based i-TE materials to pursue better performance in a higher temperature range.

高强高韧聚乙烯醇导电水凝胶的结构与传感性能

为了制备高强高韧导电水凝胶,采用能与聚乙烯醇(PVA)形成氢键相互作用的单宁酸(TA)为物理交联剂,以丙三醇和水为共溶剂制备得到具有纳米纤维网络结构的PVA/TA有机水凝胶;通过浸泡1 mol/L硝酸银溶液得到金属络合作用和氢键作用协同增强增韧的导电水凝胶。研究结果表明,当PVA和TA质量比为2:3时,水凝胶中TA与银离子能形成强烈的络合作用,进一步增强了TA与PVA分子链间形成的物理交联网络,凝胶内部形成了更为致密的网络结构,从而赋予导电水凝胶优异的力学性能,其强度、模量和韧性相较于未引入TA的PVA水凝胶分别提高了4.5倍、5倍和5倍。该导电水凝胶用于应变传感时,表现出优异的灵敏性(GF=99.4)、极高的线性度(R~2>0.99)和良好的循环稳定性(>500圈)。

Piezoresistive behavior of elastomer composites with segregated network of carbon nanostructures and alumina

Electrically conductive elastomer composites(CECs)with segregated networks of conductive nanofillers show high potential in stretchable strain sensors due to balanced mechanical and electrical properties,yet the sensitivity at low strain is generally insufficient for practical application.Herein,we report an easy and effective way to improve the resistive response to low strain for CECs with segregated network structure via adding stiff alumina into carbon nanostructures(CNS).The CEC containing 0.7 wt%CNS and 5 wt%Al_(2)O_(3) almost sustains the same elasticity(elongation at break of~900%)and conductivity(0.8 S/m)as the control,while the piezoresistive sensitivity is significantly improved.Thermoplastic polyurethane(TPU)composites with a segregated network of hybrid nanofillers(CNS and Al_(2)O_(3))show much higher strain sensitivity(Gauge factor,GF-566)at low strain(45%strain)due to a local stress concentration effect,this sensitivity is superior to that of TPU/CNS composites(GF-11).Such a local stress concentration effect depends on alumina content and its distribution at the TPU particle interface.In addition,CECs with hybrid fillers show better reproducibility in cyclic piezoresistive behavior testing than the control.This work offers an easy method for fabricating CECs with a segregated filler network offering stretchable strain sensors with a high strain sensitivity.

Silk fibroin-based flexible pressure sensors:processing and application

With the advent of the internet of things and artificial intelligence,flexible and portable pressure sensors have shown great application potential in human-computer interaction,personalized medicine and other fields.By comparison with traditional inorganic materials,flexible polymeric materials conformable to the human body are more suitable for the fabrication of wearable pressure sensors.Given the consumption of a huge amount of flexible wearable electronics in near future,it is necessary to turn their attention to biodegradable polymers for the fabrication of flexible pressure sensors toward the development requirement of green and sustainable electronics.In this paper,the structure and properties of silk fibroin(SF)are introduced,and the source and research progress of the piezoelectric properties of SF are systematically discussed.In addition,this paper summarizes the advance in the studies on SF-based capacitive,resistive,triboelectric,and piezoelectric sensors reported in recent years,and focuses on their fabrication methods and applications.Finally,this paper also puts forward the future development trend of high-efficiency fabrication and corresponding application of SF-based piezoelectric sensors.It offers new insights into the design and fabrication of green and biodegradable bioelectronics for in vitro and in vivo sensing applications.

Self-assembled core-shell polydopamine@MXene with synergistic solar absorption capability for highly efficient solar-to-vapor generation

As a renewable and environment-friendly technology for seawater desalination and wastewater purification,solar energy triggered steam generation is attractive to address the long-standing global water scarcity issues.However,practical utilization of solar energy for steam generation is severely restricted by the complex synthesis,low energy conversion efficiency,insufficient solar spectrum absorption and water extraction capability of state-of-the-art technologies.Here,for the first time,we report a facile strategy to realize hydrogen bond induced self-assembly of a polydopamine(PDA)@MXene microsphere photothermal layer for synergistically achieving wide-spectrum and highly efficient solar absorption capability(≈96%in a wide solar spectrum range of 250–1,500 nm wavelength).Moreover,such a system renders fast water transport and vapor escaping due to the intrinsically hydrophilic nature of both MXene and PDA,as well as the interspacing between core-shell microspheres.The solar-to-vapor conversion efficiencies under the solar illumination of 1 sun and 4 sun are as high as 85.2%and 93.6%,respectively.Besides,the PDA@MXene photothermal layer renders the system durable mechanical properties,allowing producing clean water from seawater with the salt rejection rate beyond 99%.Furthermore,stable light absorption performance can be achieved and well maintained due to the formation of ternary TiO2/C/MXene complex caused by oxidative degradation of MXene.Therefore,this work proposes an attractive MXene-assisted strategy for fabricating high performance photothermal composites for advanced solar-driven seawater desalination applications.

Facile Synthesis and in situ TEM Observation of Nanoporous Pd for Enhanced Catalytic Applications

A facile, efficient and green photochemical synthetic approach has been used to prepare sponge-like porous Pd nanoparticles. Obtained by ultraviolet irradiation using a K2PdCl4 precursor solution, the final products exhibited three dimensionally interconnected porous structures made up of ~3.6 nm sized Pd nanoparticles. In situ liquid cell TEM results indicated such porous structures are in a dynamic stable state when the particles are distributed in aqueous solution. The porous Pd nanoparticles exhibited electrochemical active surface area (ECSA) of up to 43 m^2·g^–1 and mass activity of 1144 mA·mg^–1 in menthol oxidation, kapp of 0.22 min^–1 and normalized kapp/m (kn) of 8.3×10^4 min^–1·g^-1 in 4-nitrophenol (4-NP) reduction reactions. Comparing with the literature, it is demonstrated that our porous Pd nanoparticles with clean surfaces exhibited very high catalytic performances. This work may shed a light on facile and green synthesis of noble-metal particles with better catalytic performances.

Anti-fatigue ionic gels for long-term multimodal respiratory abnormality monitoring

Wearable electronics integrated with stretchable sensors are considered a promising and non-invasive strategy to monitor respiratory status for health assessment.However,long-term and stable monitoring of respiratory abnormality is still a grand challenge.Here,we report a facile one-step thermal stretching strategy to fabricate an anti-fatigue ionic gel(AIG)sensor with high fatigue threshold(0=1130 J m^(–2)),high stability(>20,000 cycles),high linear sensitivity,and recyclability.A multimodal wearable respiratory monitoring system(WRMS)developed with AIG sensors can continuously measure respiratory abnormality(single-sensor mode)and compliance(multi-sensor mode)by monitoring the movement of the ribcage and abdomen in a long-term manner.For single-sensor mode,the respiratory frequency(Fr),respiratory energy(Er),and inspire/expire time(I/E ratio)can be extracted to evaluate the respiratory status during sitting,sporting,and sleeping.Further,the multi-sensors mode is developed to evaluate patientventilator asynchrony through validated clinical criteria by monitoring the incongruous movement of the chest and abdomen,which shows great potential for both daily home care and clinical applications.