Highly stretchable anti-freeze hydrogel based on aloe polysaccharides with high ionic conductivity for multifunctional wearable sensors

Abstract

Conductive hydrogels have limitations such as non-degradability, loss of electrical conductivity at sub-zero temperatures, and single functionality, which limit their applicability as materials for wearable sensors. To overcome these limitations, this study proposes a bio-based hydrogel using aloe polysaccharides as the matrix and degradable polyvinyl alcohol as a reinforcing material. The hydrogel was crosslinked with borax in a glycerol–water binary solvent system, producing good toughness and compressive strength. Furthermore, the hydrogel was developed as a sensor that could detect both small and large deformations with a low detection limit of 1 % and high stretchability of up to 300 %. Moreover, the sensor exhibited excellent frost resistance at temperatures above −50 °C, and the gauge factor of the hydrogel was 2.86 at 20 °C and 2.12 at −20 °C. The Aloe-polysaccharide-based conductive hydrogels also functioned effectively as a wearable sensor; it detected a wide range of humidities (0–98 % relative humidity) and exhibited fast response and recovery times (1.1 and 0.9 s) while detecting normal human breathing. The polysaccharide hydrogel was also temperature sensitive (1.737 % °C−1) and allowed for information sensing during handwriting.