Streamline theory reveals bypass/trap effects in bio-inspired spine engagement dynamics

Abstract This study introduces a streamline theory to reveal the micro-engagement dynamics of bio-inspired spines on rough surfaces. It first defines two key phenomena: the "bypass effect" and the "trap effect." Simulations demonstrate that the bypass effect reduces engagement effectiveness on convex asperities, while the trap effect significantly enhances engagement capacity on concave valleys. Experiments confirm these findings, revealing that the gain from the trap effect (252.2%) far outweighs the loss from the bypass effect (9.7%). Furthermore, analysis on fractal surfaces found that stable self-locking engagement occurs almost exclusively in concave regions (80%~90%) due to the trap effect. This research provides a theoretical foundation for bio-inspired gripping technology and functional surface design, with implications for future applications in effective grippers, robotics, and space exploration.