Enhanced biocompatibility and multidirectional wet adhesion of insect-like synergistic wrinkled pillars with microcavities

Various bioinspired adhesives have been used to develop adhesive medical patches capable of robust and comfortable attachment to dry and wet skin for healthcare applications. However, it is challenging to maintain adhesion on the application of shear and pulling forces, especially on rough, curved, and wet surfaces, such those of the human body. Here, highly biocompatible adhesive patch with wrinkled mushroom-shaped structures having suction-cup-like microcavities is presented for enhanced wet adhesion and biosignal monitoring. Inspired by the unique structures on the foreleg of male diving-beetles, the adhesive patch with microwrinkle structure shows enhanced multidirectional adhesion (i.e., normal and shear directions), as well as high water/air permeability when applied to rough skin under dry and wet conditions with minimal skin irritation. Based on the structural features of insect-inspired adhesives, a simple model was proposed to understand the enhanced wet adhesion in both the normal and shear directions due to the synergistic effect of suction and capillarity, resulting from microcavities and tiny wrinkles. In addition, to demonstrate the potential in wearable medical devices, we employed our bio-inspired patches as the interface material for the electrodes, which enabled direct electrocardiogram measurements on both wet and dry skin with minimal discomfort and signal noise.