Highly stretchable, self-healing, self-adhesive and conductive nanocomposite hydrogels based on multi-reversible interactions as multifunctional strain sensors

Abstract

Construction of highly stretchable and sensitive flexible strain sensors is of great significance for wide applications in human–computer interaction, wearable devices, and electronic skins. However, it turned out to be not effortless to integrate the two seemingly contrary features of high stretchability and sensitivity into a system. Herein, we designed a nanocomposite conductive hydrogel (NCCH) composed of zwitterionic poly(HEAA-co-SBMA) polymers and lithium magnesium silicate (XLG) by means of multi-reversible molecular interactions (MRMIs) including borate ester bonds between polyHEAA and borax, hydrogen bonds, and polySBMA-XLG-based electrostatic interaction, endowing the NCCH with enhanced mechanical, self-healing, adhesive, biocompatible, and sensing performances. The MRMI method enabled NCCHs to obtain an excellent stretchability (∼1080 %)/compressibility (∼98.5 %), a tensile strength of ∼ 0.06 MPa, a good self-healing with a fracture strain recovery of 90.5 %, and a strong adhesion on various hard and soft substrates (e.g. a adhesive shear force of 60 kPa to pigskin tissues). Besides, the integration of zwitterionic polySBMA and conductive XLG promoted charge transfer.by optimal ioinic channels. Based on these outstanding strengths, the NCCHs were farther rationally fabricated as multifunctional strain sensors with remarkable sensing stability for fast and accurately detecting strain/pressure-induced deformation, joint motions, and animal heartbeats. Notably, the excellent self-healing property of NCCH sensors can facilitate their long-period usage and complete recyclability for avoiding wastes. The new MRMI-based NCCH sensor without any conductive additives is deemed to provide a new strategy for broadening their multifunctional strain sensor and healthcare monitoring applications.