Abstract
Hillstream fishes live in the current with high velocity of flow and with unpredictable water impact. Therefore, they evolved various adhesive apparatus to survive in rapid flow. Adaptations to stream current can offer hillstream fishes advantages in underwater adhesion on substrates with different properties. In this study, Pulin river loach (Sinogatromyzon puliensis) was investigated to understand the relationship between micro/-nano- structure and attachment mechanisms. The hierarchical structures on ventral fin were characterized by optical microscopy and scanning electron microscopy. Pull-off force measurements were also conducted to measure the critical adhesive force that river loach can adhere to different substrates. Adhesive apparatus and mechanism for river loach are discussed and compared with the commercial sucker. Commercial sucker has better adhesive ability to smooth surface while river loach can adhere equally well to surfaces with different roughness. Moreover, the functions of microstructures were also characterized. It has been shown that river loach performed well on both PDMS substrates and sandpaper, which are composed of relatively soft and hard material respectively. The specialized apparatus and adhesion capability of such suction system could enlighten us on fabricating innovative bio-inspired devices for underwater attachment.