Reconfigurable Electrical Networks within A Conductive Hydrogel Composite.

Soft materials that exhibit the compliance, programmability, and reconfigurability could have transformative impact as electronic skin for applications in wearable electronics/soft robotics. There has been significant progress in soft conductive materials; however, achieving electrically-controlled and reversible changes in conductivity and circuit connectivity remains challenging. To overcome this limitation, we present soft material architecture with reconfigurable conductive networks of silver flakes embedded within a hydrogel matrix. The conductive networks can be reversibly created/disconnected through various stimuli, including current, humidity, or temperature. Such stimuli affect electrical connectivity of the hydrogel by controlling its water content, which can be modulated by evaporation under ambient conditions (passive dehydration), evaporation through electrical Joule heating (active dehydration), or absorption of additional water (rehydration). Through passive dehydration, the volume fraction of conductive fillers increases as water evaporates, enhancing electrical conductivity. Applying electrical power across the composite accelerates water evaporation and forms conductive pathways faster with greater connectivity than composites subjected to passive dehydration. Alternatively, the percolating networks of silver flakes can be disrupted when the hydrogel absorbs water. The resulting change in electrical conductivity is reversible and repeatable, endowing the composite with on-demand reconfigurable conductivity. To highlight this material's unique properties, we show that conductive traces can be reconfigured after severe damage and revert to lower conductivity after rehydration. Additionally, we demonstrate a quadruped robot that can respond to stimuli by changing direction following exposure to excess water, thereby achieving reprogrammable locomotion behaviors. This article is protected by copyright. All rights reserved.