Facile preparation and high performance of wearable strain sensors based on ionically cross-linked composite hydrogels

Abstract

Flexible sensors that can respond to multiple mechanical excitation modes and have high sensitivity are of great significance in the fields of electronic skin and health monitoring. Simulating multiple signal responses to skin such as strain and temperature remains an important challenge. Therefore, new multifunctional ion-crosslinked hydrogels with toughness and conductivity were designed and prepared in this work. A chemical gel with high mechanical strength was prepared by cross-linking acrylamide with N,N′-methylene-bisacrylamide and ammonium persulfate. In addition, in order to enhance the conductive properties of the hydrogel, Ca²⁺, Mg²⁺ and Al³⁺ ions were added to the hydrogel during cross-linking. The double-layer network makes this ionic hydrogel show excellent mechanical properties. Moreover, the composite hydrogel containing Ca²⁺ can reach a maximum stretch of 1100% and exhibits ultra-high sensitivity (S _p = 10.690 MPa⁻¹). The obtained hydrogels can successfully prepare wearable strain sensors, as well as track and monitor human motion. The present prepared multifunctional hydrogels are expected to be further expanded to intelligent health sensor materials.

摘要

可响应多种机械激励模式且具有较高灵敏度的柔性传感器 在电子皮肤、健康监测等领域具有重要意义. 而模仿皮肤的多信 号响应, 如应变和温度, 仍然是一个重要的挑战. 因此, 本文设计了 具有韧性与导电性的多功能离子交联水凝胶. 通过将丙烯酰胺与 N,N′-亚甲基双丙烯酰胺、过硫酸铵交联, 可制备出具有高力学强 度特性的化学凝胶, 交联时加入Ca²⁺, Mg²⁺, Al³⁺等盐类物质赋予水 凝胶双层网络, 使这种离子型双网络水凝胶具有优良的导电特性. 这种双层网络结构使离子水凝胶表现出优异的力学性能. 此外, 含 有Ca²⁺离子的复合水凝胶最大拉伸可以达到1100%, 并表现出超高 的灵敏度(S _p = 10.690 MPa⁻¹). 所获得的水凝胶能够实现可穿戴应 力传感器的制备并跟踪监测人体运动, 有希望进一步拓展到人机 交互以及智能人体健康检测等领域.