Hydrogel-elastomer-based stretchable strain sensor fabricated by a simple projection lithography method

Stretchable strain sensor detects a wide range of strain variation and is therefore a key component in various applications.Unlike traditional ones made of elastomers doped with conductive components or fabricated with liquid conductors,ionically conductive hydrogel-based strain sensors remain conductive under large deformations and are biocompatible.However,dehydration is a challenging issue for the latter.Researchers have developed hydrogel-elastomer-based strain sensors where an elastomer matrix encapsulates a hydrogel circuit to prevent its dehydration.However,the reported multistep approaches are generally time-consuming.Our group recently reported a multimaterial 3D printing approach that enables fast fabrication of such sensors,yet requires a self-built digital-light-processing-based multimaterial 3D printer.Here,we report a simple projection lithography method to fabricate hydrogel-elastomer-based stretchable strain sensors within 5 minutes.This method only requires a UV projector/lamp with photomasks;the chemicals are commercially available;the protocols for preparing the polymer precursors are friendly to users without chemistry background.Moreover,the manufacturing flexibility allows users to readily pattern the sensor circuit and attach the sensor to a 3D printed soft pneumatic actuator to enable strain sensing on the latter.The proposed approach paves a simple and versatile way to fabricate hydrogel-elastomer-based stretchable strain sensors and flexible electronic devices.

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.

The stretchable carbon black-based strain fiber with a remarkable linearity in a wide sensing range

Ascribed to its wide sensing range,high sensitivity,and low stiff-ness to match target objects with complex 3D shapes,the stretch-able strain sensor has shown its promising applications in various fields,ranging from healthcare,bodynet,and intelligent traffic system,to the robotic system.This paper presents a low-cost and straightforward fabrication technology for the stretchable strain fiber with the combined attributes of a wide sensing range,excep-tional linearity,and high durability.The hybrid composite consist-ing of carbon black and silicone is utilized as the functional material to respond to the external mechanical deformation due to the piezoresistive effect.To address the remarkable hysteresis of the CB-silicone composites,the latex tubes with excellent mechanical robustness and a considerable accessible tensile strain are intro-duced as the outer supporting components.After injecting the conductive CB-silicone composite into these tubes,the stretchable strain fibers are successfully prepared.Notably,the stretchable strain sensor exhibits linearity(R^(2)=0.9854)in a wide sensing range(0-400%)and remarkable durability even after the 2500 cycles under 100%tension.Additionally,the potential of this stretchable strain fiber as the wearable strain sensor and the realtime feedback is demonstrated by detecting the body motion and the expansion devices.

高灵敏度和高线性度的可拉伸应变传感器的分层结构设计

对柔性电子设备日益增长的需求使得开发具有高灵敏度和高线性度的传感器更加迫切.由于拉伸应变下不可逆结构损伤诱导电阻线性急剧增加,现有的可拉伸应变传感器难以完美地同时实现这两个特性.针对这一问题,本文提出了一种兼具表面褶皱和体相梯度孔隙的新型分级互连结构,利用水热活化机制精确控制纳米级褶皱间距,通过调控相分离中热力学和动力学行为构筑出体相梯度多孔结构,通过改变器件两侧曲率实现各向异性特征,深入研究各种设计的功效、量化几何结构对灵敏度的有效贡献和追踪形态演变.基于器件显著的灵敏度和各向异性,所制备的传感器能够有效监测静态和动态位移、表面运动、二维应变信号变化以及预测液位随时间变化.本工作为实现高质量的感知能力提供了一种广泛适用、适应性强、可扩展且具有成本效益的方法.