Bionic Wet Adhesive Surface with Micronano Hierarchical Structure for Robust Biosignal Monitoring

In current medical diagnostics, skin patches often experience reduced adhesion forces or even complete failure due to perspiration, thereby compromising the quality and stability of biosignal monitoring. Inspired by the hexagonal prism structure of tree frogs and the hexagonal frame structure of honeybees, we designed a honeybee-treefrog bionic hierarchical patterned surface (HTP) fabricated with polydimethylsiloxane (PDMS), integrating the advantages of both organisms to significantly enhance wet adhesion performance. The adhesion performance of the HTP under various wetting conditions was systematically evaluated by constructing different types and sizes of adhesive surfaces. The results indicate that the HTP can effectively drain excess liquid from the contact interface and maintain high adhesion force. The HTP demonstrated remarkable improvements in both normal and shear adhesion force, with shear adhesion increased by approximately 8-fold and normal adhesion by 4-fold, compared to that of nonpatterned surfaces. Through theoretical modeling and experimental validation, the HTP reduces the height of the liquid bridge at the adhesion interface via the liquid film self-absorption effect, thereby enhancing both normal and shear adhesion. Additionally, the shear adhesion is further improved by the air embolism effect, which is formed by stagnant air pockets under low fluid volume conditions. Beyond superior wet adhesion performance, the HTP also exhibited excellent liquid drainage capability and reusability. Applied to skin patches, the HTP showcased its potential for electrocardiogram (ECG) monitoring, demonstrating strong biocompatibility and biosignal detection capabilities, offering new solutions for wearable medical devices.