A wide-temperature-range sensor based on wide-strain-range self-healing and adhesive organogels

Abstract

Traditional hydrogels have been widely studied for intelligent wearable, soft mechanical, and biological medical applications due to their high water content and good biocompatibility. However, when hydrogels are used at high and low temperatures, they will inevitably face two defects: water loss and freezing. It is difficult to maintain the tensile properties, self-healing properties, and electrical conductivity of hydrogels modified to overcome these two defects. To this end, we study the mechanical properties of organogels obtained via covalently cross-linking polyacrylic acid with vinyl functionalized silicon nanoparticles (Vsnp) to form a mechanical skeleton, with dynamic reversible cross-linking network between acrylic acid and iron ions supporting the high tensile properties of the gel. The introduction of the conductive polymer polypyrrole as a conductive skeleton grafted onto gelatin can effectively avoid the issues relating to low-temperature water environment conductive gel ion transport, allowing a suitable wide temperature region for a new physically and chemically crosslinked glycerin/water organogel network structure, so as to realize organogels with balanced mechanical, electrical, and self-healing properties. The prepared organogel has good tensile properties (1140% strain), self-healing properties (3 h healing efficiency: 96%), and strong adhesion over a wide temperature range from −26 °C to 60 °C. A strain sensor based on this gel exhibits high sensitivity (GF = 13.6), low hysteresis, and a life span over a wide strain range (350%), and it can be used to monitor human tiny movements (such as swallowing, pulse, etc.). This indicates that this kind of organogel-based sensor can break through restrictions relating to the external environment and show outstanding application potential in the fields of human-machine interfaces and soft robots.