A dry-state electrode patterning strategy for electrically driven hydrogel actuators

Abstract

Electrically driven hydrogels have emerged as promising candidate materials for soft actuators due to their large deformation capability and intrinsic compliance. However, conventional wet-state fabrication protocols severely restrict the precise patterning of complex electrode geometries and conductive traces, ultimately limiting attainable deformation and system-level integration. Herein, a facile dry-state electrode patterning strategy is reported, enabling superior design versatility for soft machines. Sputtering gold electrodes directly onto lyophilized hydrogel substrates achieves robust interfacial adhesion via topographic mechanical interlocking. This structural integration exhibits exceptional fatigue resistance, maintaining a stable sheet resistance of 1.79–2.25 Ω/sq even after 5000 continuous bending cycles. Furthermore, this dry-state processing method facilitates arbitrary two-dimensional (2D) electrode topologies and through-thickness vertical interconnect access (VIA) channels, establishing complex three-dimensional (3D) electrical routing. A conformal silicone coating on the electrodes effectively mitigates electrolysis-induced delamination, ensuring extended operational stability in underwater environments. The resulting actuators deliver programmable and versatile morphing capabilities, achieving a maximum curvature of 0.37 mm−1. Finally, by tailoring the polymer network’s mechanical compliance, the inherent elastic mismatch between the metallic film and the hydrogel is exploited to create conductive crack networks for proprioceptive sensing, enabling real-time deformation monitoring.