Nanozyme-enabled antibacterial sponge hydrogel-based electronic skin for underwater tactile sensing and slip-direction recognition

Nanozyme-infused sponge hydrogels suppress swelling and enable intrinsic antibacterial activity. • Coupling vertical compression/lateral expansion allows simultaneous normal/shear stress detection. • A 2 × 2 electrode array generates unique signal patterns to identify sliding directions and motion trends. • Quantifies 20–1000 g objects and enables grip-force regulation via polynomial regression modeling. • A 4-channel tactile coding strategy converts characters into real-time electrical signals. Underwater wearable sensors are highly desirable for aquatic operations, soft robotics, and human-machine interaction. However, their practical deployment remains limited by hydrogel swelling, hydrostatic-pressure disturbance, biofouling, and insufficient multidirectional tactile feedback. Here, we report a nanozyme-enabled antibacterial sponge hydrogel-based electronic skin for underwater tactile sensing and slip-direction recognition. The electronic skin is fabricated by physically confining a prepolymerized chitosan/polyacrylamide/nanozyme precursor within a commercial open-cell poly(vinyl alcohol) (PVA) sponge, followed by repeated in situ UV polymerization to form a composite denoted as CS/PAM/CCN/PVA. The incorporated C 3 N 4 @CDs-ZIF nanozyme provides conductivity, fluorescence, and antibacterial activity, while the porous PVA scaffold mechanically supports the hydrogel network and effectively suppresses excessive re-swelling in water. Owing to the coupling between vertical compression and lateral expansion, the resulting three-dimensional (3D) sensors can simultaneously detect normal pressure and direction-dependent shear deformation. A 2 × 2 electrode array generates characteristic multidimensional signal patterns, enabling identification of sliding direction and recognition of relative motion trends. As a wearable fingertip device, the sensor supports underwater grasping experiments for objects with masses ranging from 20 to 1000 g and allows estimation of the minimum force required to avoid slippage through resistance-threshold analysis. In addition, a second-order polynomial empirical fit is established to describe the relationship among grasping pressure, object mass, and resistance change. A four-channel tactile coding strategy further enables rapid underwater message transmission by converting characters into real-time electrical signals. This work provides a multifunctional electronic-skin platform for tactile perception, grasp-force regulation, and low-infrastructure communication in freshwater environments. Download: Download high-res image (233KB) Download: Download full-size image