Multifunctional robust dual network hydrogels constructed via dynamic physical bonds and carbon nanotubes for use as strain and pressure sensors

Abstract

Carbon-based hydrogels have emerged as a promising material for wearable strain and pressure sensors due to their excellent conductive and mechanical flexibility. However, some shortcomings such as limited stretchability and susceptibility to phase separation have led to a narrow range of applications. In this study, a GPEC hydrogel was prepared by incorporating metal ions and oxidized multi-walled carbon nanotubes (oxCNTs) into a double-network (DN) hydrogel consisting of gum arabic (GA) and a copolymer polymerized by acrylamide (AM), acrylic acid (AA) and N-methylolacrylamide (NMAM). The uniformly distributed oxCNTs and metal ions formed a three-dimensional (3D) structure of the hydrogel through a large amount of metal complex bonds and hydrogen bonds. The strong interaction improved the mechanical properties of the hydrogels, with an elongation at break of 1957% and a strength at break of 915 kPa. Furthermore, the hydrogels exhibited excellent self-adhesive and self-healing properties. The hydrogel also exhibits high conductivity due to the embedded metal ions and oxCNTs forming a conductive network. The as-prepared strain sensor revealed ultra-high sensitivity (GF = 3.08) and fast response (72 ms). Moreover, the GPEC hydrogel exhibits high pressure sensitivity (2.27 kPa⁻¹ in the range of 0–10 kPa and 0.08 kPa⁻¹ in the range of 20–80 kPa) when assembled into a pressure sensor. Consequently, the GPEC hydrogel sensor could be used to monitor the full range of human motion and could be incorporated into pressure sensing devices for handwriting recognition.

Graphical Abstract