Tough Ion-Conductive Hydrogel with Anti-Dehydration as a Stretchable Strain Sensor for Gesture Recognition

Abstract

Stretchable hydrogel-based strain sensors have attracted considerable interest for their potential applications in human motion detection, physiological monitoring, and electronic skin. Yet, the durability of hydrogel sensors is seriously hindered due to inevitable water evaporation and weak mechanical properties. Herein, we report modified polyampholyte (PA) hydrogels that show anti-dehydration and ion conductivity via a simple metal-ion solution soaking and drying-out strategy. In this strategy, an as-prepared PA hydrogel (with ionic bonds) is dialyzed in FeCl3 solutions (Step-I) and annealed at 65 °C for (Step-II) successively to reconstruct its network with numerous synergistic ionic and metal–ligand bonds. The resulting hydrogels demonstrate superior mechanical properties, ultralong anti-dehydration life span (>30 days), and high ion conductivity (≈15 S m–1). To understand the reinforcement mechanisms, we evaluate the viscoelastic and elastic contributions to the mechanical properties of the hydrogels via a viscoelastic model. This gel can be further engineered to a stretchable strain sensor to recognize hand gestures with a well-trained machine learning algorithm. The proposed strategy is straightforward and effective for achieving anti-dehydration and highly ion-conductive tough hydrogels.