Breaking the Trade-Off between Strain and Electric Properties in Starch-Based Hydrogel Flexible Sensors via Multinetwork Structures Featuring Ag–S Bonds

Leveraging the superior conductivity and stretchability of hydrogels to promote their application in flexible electronic devices represents an effective approach to advancing the field of flexible sensors. Starch-based hydrogels, which possess advantages such as biodegradability, biocompatibility, and nontoxicity, are highly desirable for flexible sensors. However, the numerous hydrogen bonds within starch chains and the poor dispersibility of conductive materials in the hydrogel restrict the balance between stretchability and conductivity, posing a significant challenge in the development of flexible sensors. Herein, a multinetwork structure is designed to prepare a potato starch (S–S)/poly(vinyl alcohol)/N-isopropylacrylamide/carboxymethyl cellulose-Ag nanowires1.5 (PTS/PVA/NIPAM/CMC-Ag1.5) hydrogel material featuring favorable stretchability (1343% elongation) and conductivity (1.6 S/m). Functionally, the multinetwork and reversible dynamic bonds enable the PPNC-Ag1.5 hydrogel to achieve high self-healing efficiency (up to 90%) and recyclability. Antimicrobial tests show that the PPNC-Ag1.5 hydrogel exhibits excellent inactivation of Escherichia coli and Staphylococcus aureus, with sterilization rates of 99.44% and 91.91%, respectively. Furthermore, the PPNC-Ag1.5 hydrogel is used to develop strain/temperature sensors that exhibit high sensitivity to strain (gauge factor, F = 1.3) and temperature (temperature coefficient of resistance, TCR = 2.5%/°C). This strategy overcomes the trade-off between strain and electrical properties of starch-based hydrogels, thereby demonstrating significant potential for applications in the fields of fever monitors and motion monitors.