Injection‐on‐Skin Granular Adhesive for Interactive Human–Machine Interface

Abstract Realization of interactive human–machine interfaces (iHMI) is improved with development of soft tissue‐like strain sensors beyond hard robotic exosuits, potentially allowing cognitive behavior therapy and physical rehabilitation for patients with brain disorders. Here, this study reports on a strain‐sensitive granular adhesive inspired by the core–shell architectures of natural basil seeds for iHMI as well as human–metaverse interfacing. The granular adhesive sensor consists of easily fragmented hydropellets as a core and tissue‐adhesive catecholamine layers as a shell, satisfying great on‐skin injectability, ionic‐electrical conductivity, and sensitive resistance changes through reversible yet robust cohesion among the hydropellets. Particularly, it is found that the ionic‐electrical self‐doping of the catecholamine shell on hydrosurfaces leads to a compact ion density of the materials. Based on these physical and electrical properties of the sensor, it is demonstrated that successful iHMI integration with a robot arm in both real and virtual environments enables robotic control by finger gesture and haptic feedback. This study expresses benefits of using granular hydrogel‐based strain sensors for implementing on‐skin writable bioelectronics and their bridging into the metaverse world.