Multiresponsive Ionic Conductive Alginate/Gelatin Organohydrogels with Tunable Functions

Abstract

Materials combining stretchability and sensitivity to external stimuli are key for wearable electronics applications to enable the emergence of disruptive technologies in biosensing, health monitoring, photodetection and human motion recognition. Conductive organohydrogels have gained significant attention due to their high sensitivity and cost-effective preparation. Biopolymers like gelatin and alginate offer unique opportunities for developing responsive wearable devices, owing to their biocompatibility and sensitivity toward environmental factors. Here sustainable bio-inspired method is presented to produce alginategelatin organohydrogels combining transparency in the visible range, ionic conductivity, high stretchability, and multiresponsiveness. The controlled alginate's crosslinking with various metal cations like Mn²⁺, Cu²⁺, Fe³⁺, and Zr⁴⁺ enables modulating ionic conductivity as well as finely tuning the material's thermal and mechanical properties. These organohydrogels show responsiveness to temperature (from 10 to 50 degrees, with a sensitivity of 0.19 K⁻¹), relative humidity (from 20 to 80%, with a sensitivity of 0.022 RH(%)⁻¹), and strain (gauge factor >1.6), enabling real-time monitoring of environmental and physiological parameters. Remarkably, they also exhibit photoresponsivity of 9.2 µA W⁻¹ under visible light, a feature rarely reported in literature. The ease of tuning responsiveness to the chosen stimuli and the high sensitivities open perspectives for applying these materials as wearable stretchable sensors.