Braking Mechanism of Ladybird Foot Setae during Slope Rolling

The seven-spotted ladybird (Coccinella septempunctata) is a Coleoptera with dome-shaped elytra. It exhibits a unique braking ability during somersaults, which may be attributed to the typical hair-like structures coated on the surface of its foot. However, the mechanism by which this hair-like structure aids in braking during somersaults remains unexplored. In this study, we selected the seven-spotted ladybird as a representative model to demonstrate that the special geometric disc-shaped setae at the foot's end, combined with the adhesive secretion, can produce a stable peeling brake effect. During somersaults, live ladybirds with feet have a high probability (77.5%) of achieving effective braking through multiple peeling actions of their functional foot setae interacting with the slope surface. Furthermore, during each peeling phase, the angular velocity of the ladybird can be decreased by 22.57 ± 3.95 rad/s within an extremely short time of 40.00 ± 3 ms, effectively facilitating rapid dissipation of substantial kinetic energy. We proposed a theoretical model for the peeling braking behavior, considering both adhesive and frictional forces, which is demonstrated by the comparison with experimental results. The predicted energy dissipation closely matched experimental data in both magnitude and trend, validating the model and supporting its application in bioinspired design. We fabricated a bioinspired braking device and tested its efficacy in braking. This braking mechanism of a ladybird may inspire the braking systems used in microelectro-mechanical systems.