88 / 2018-06-21 19:11:23

Bioinspired strong wet attachment surface based on the strong boundary friction of tree frog's toe pad

tree frog,bioinspired surface,wet friction,capillary force,medical devices

全体主题 > iv. Design and fabrication of organ-on-a-chip, disease models, bioreactors, and medical and diagnostic devices

Strong wet attachment is always anticipated on medical and healthy instruments, such as surgical graspers and wearable sensors, whereas the mucus on soft tissues and sweat on skins can work as lubricant and easily leads to poor attaching performance. In nature, tree frog can easily climb on various types of wet surfaces and is ideal for strong wet attaching studying. Structural characterization shows that the toe pad is constructed with micropillar array and each micropillar is covered with nanopillars, which forms hierarchical structure. With secretion volume gradually decreasing during successive testing steps, secretion film on toe pad starts to split from channels and its friction shows 10 times increasing even without any normal force, here defined as boundary friction. When bioinspired hexagonal pillar surface separating from substrate, liquid film between interfaces exhibits self-splitting effect just like on tree frog’s toe pad, which uniformly distributes the liquid over the surface. During successive testing steps, friction on bioinspired surface also demonstrates a strong rise, i.e. the boundary friction is about 50 times higher than wet and dry friction. The underlying mechanism is ascribed to the extremely strong capillary force induced by nano-thick liquid film, which forcefully presses soft pillar to substrate and generates strong friction without any normal force. Finally, the application of strong wet attachment on surgical graspers and wearable sensors have been validated. This study further expands the understanding of wet friction on soft material and can improve the wet contact performance on surgical graspers and wearable sensors.