Water-proofing mechanism of coupling structures observed in ladybird elytra and its bionic application

Ladybirds (Coccinella septempunctata) are adept at living in humid conditions as their elytra can effectively shield their bodies from raindrops. However, due to technical difficulties in examining the delicate structure, the understanding of the water-proofing mechanism of the coupling structure and its impact on the dome-like elytra response to the raindrops remain elusive. In this combined experimental and theoretical study, we showed that the coupling structure on the ladybird elytra can ward off the raindrops traveling at a velocity of 6 m/s, which generates an impact force equivalent to 600 times the body weight. The waterproofing mechanism relies on the deformability of the elytra and their microstructures, which collectively impedes the formation of microchannels for liquids. The enhanced water-proofing capabilities enabled by the coupling structures are validated through experimental testing on comparative 3D-printed models, showing the effectiveness of these structures in improving water resistance. Subsequently, we showcased a water-proofing device, which substantially improved the efficiency of solar panels in converting solar energy. This multidisciplinary study not only advances our understanding of the biomechanics of coupling systems in insects but also inspires the design of water-proofing deployable structures.