Green Durable Biomechanical Sensor Based on a Cation-Enhanced Hydrogel

Abstract

The multinetwork hydrogel-based biomechanical sensor has attracted considerable attention due to its excellent mechanical properties. However, in most cases, due to the weak binding force of the hydrogel matrix to water and the uneven structure of the sensing layer, it is difficult to prepare pressure (strain) sensors that can quantify stimuli-response and be durable for long periods. Moreover, the preparation of hydrogels often involves the intervention and residue of toxic substances, making them unsuitable for monitoring biomechanical indicators. In this paper, we prepared a flexible, conductive biohydrogel capable of long-term storage using low-cost, biocompatible materials. The hydrogel is composed of lignosulfonate sodium and poly(vinyl alcohol), blended with acrylic acid and enhanced with various cations with different hydration abilities. The pressure sensor based on the as-prepared hydrogel exhibits a high sensitivity of 1.145 kPa^–1 to medium pressure encountered by the human body (i.e., 0.1 to 10 kPa). Due to the high flexibility and toughness of the hydrogel, the corresponding pressure sensor demonstrates 2500 cycles of cycling stability. Also, the strain sensor based on the as-prepared hydrogel shows a wide testing range from 0 to 1100% and quantifies the strain–response physical process based on its mechanical and electrical properties, making it suitable for use. Due to the compressibility, high sensitivity, and long-term stability, the proposed sensors could show great potential in wearable electronic devices for monitoring biological activities.