Flexible Strain Sensor Based on Thermosensitive Hydrogel with Switchable Interfacial Adhesion

Hydrogels have attracted extensive attention for flexible wearable sensors because of their flexibility and biocompatibility. However, existing bionic adhesion strategies (catechol-Fe 3+ coordination) often suffer from excessively strong adhesion, leading to structural damage or residue upon stripping, which limits reusability and biosafety. Here, we address this by incorporating a thermosensitive monomer (NIPAM) into a poly(acrylic acid) network via a catechol-Fe 3+ catalytic initiation system while introducing a zwitterionic monomer (DMAPS) to inhibit NIPAM self-aggregation without compromising temperature responsiveness. The resulting NPAE hydrogel exhibits switchable interfacial adhesion with sufficient toughness. It also shows high conductivity (1.13 S/m) and a fast response/recovery (60.1 ms). In human motion monitoring and gesture recognition, the hydrogel delivers stable, repeatable signals, demonstrating its promise for flexible electronics and wearable sensors.