Abstract
Robust and reversible wet attachments are important for medical engineering and wearable electronics. Although ultrastrong capillarity from interfacial nano-thick liquid bridges creates tree frog's strong wet friction, its unstable nano-liquid characteristic challenges further wet friction enhancement. Here, unique hierarchical micro-nano fibrous pillars have been discovered on Chinese bush crickets exhibiting a robust wet friction ~3.8 times higher than tree frog's bulk pillar. By introducing a nano-fibrous pillar array covered with thin films (NFPF), the pillar's separation position switches from the rear to front side compared with bulk pillars, indicating the interfacial contact stress shifting from compressing to stretching. This largely decreases the interfacial separation stress to form more stable and larger nano-liquid bridges. The NFPF array with self-splitting of interfacial liquid and contact stress further guards such interfacial stress shifting to ensure a ~1.9 times friction enhancement. Last, the theories are established, and the applications on wearable electronics are validated.