Performance characterization of ionic-hydrogel based strain sensors  

作　　者：XU HaiPeng SHEN ZeQun GU GuoYing 

机构地区：[1]Robotics Institute,School of Mechanical Engineering,Shanghai Jiao Tong University,Shanghai 200240,China [2]State Key Laboratory of Mechanical System and Vibration,Shanghai Jiao Tong University,Shanghai 200240,China

出　　处：《Science China(Technological Sciences)》2020年第6期923-930,共8页中国科学（技术科学英文版）

基　　金：supported by the National Natural Science Foundation of China(Grant Nos.91848204;51622506 and 91948302);the Shanghai Jiao Tong University Scientific and Technological Innovation Funds。

摘　　要：Ionic hydrogels,owing to the advantages of stretchability,conductivity and transparency,have attracted more attention for developing new soft sensors and artificial skins.Existing works on ionic-hydrogel based sensors mostly focus on material synthesis,structure design and functional integration,while few studies investigate the characterization of their sensing performances.In this paper,we present a method to characterize the performance(e.g.,sensitivity,linearity and repeatability)of a kind of ionic-hydrogel based strain sensors by varying the testing frequencies and the sensors’geometry(e.g.,length-width(L/W)ratio).To this end,we first develop an experimental testing platform and fabricate a series of strain sensors made of the polyacrylamide(PAAm)hydrogel containing ionic conductive medium.We establish an equivalent electrical model to represent the ionic-hydrogel based strain sensors,indicating the influence of the testing frequencies and L/W ratio of the ionic hydrogels on their sensing performances.These theoretical predictions are in agreement with results obtained through experimental measurements.We further demonstrate that(1)the sensitivity of the strain sensors,characterized by the gauge factor(GF),increases with the rise of testing frequencies but tends to be stable over the frequency of 5 kHz;(2)the sensitivity GF has a nonlinear relation with the L/W ratio of the strain sensors,but with a certain maximum value under the same testing frequency when the L/W ratio equals to 4.80.We verify the above experimental observations with two commonly used electrolytes,including lithium chloride and sodium chloride.With the optimum testing frequency and L/W ratio,we finally conduct various experiments to demonstrate the low hysteresis and good repeatability of our ionic-hydrogel based strain sensors.This work provides an approach to characterize the performance of the ionic-hydrogel based strain sensors,which may be an important step forward in further applications of ionic hydrogels in soft robotics.

关 键 词：ionic hydrogels sensor characterization large-strain sensor stretchable electronics 

分 类 号：TP212[自动化与计算机技术—检测技术与自动化装置] O648.17[自动化与计算机技术—控制科学与工程]