Department Functional Morphology and Biomechanics, Zoological Institute of the University of Kiel, Am Botanischen Garten 1-9, Kiel, Germany.
J R Soc Interface. 2013 Jan 6;10(78):20120639. doi: 10.1098/rsif.2012.0639. Epub 2012 Oct 3.
Reliable attachment ability of insect adhesive pads is proposed to be due to pad secretion. It has been shown that surface roughness strongly reduces adhesion forces of insect pads. This effect has been explained by decreased contact area and rapid fluid absorption from the pad surface by rough surfaces. However, it remains unclear how the fluid flows on rough substrates having different roughness parameters and surface energy. In this paper, we numerically studied the fluid flow on rough substrates during contact formation. The results demonstrate that an increase in the density of the substrate structures leads to an increase in fluid loss from the pad: substrates with a fine roughness absorb pad fluid faster. Decreased affinity of the solid substrate to the fluid has a more remarkable effect on the fluid loss and leads to a decrease in the fluid loss. With an increase in the aspect ratio of the substrate irregularities (porosity), the fluid loss is decreased. The numerical results obtained agree well with previous observations on insects and experimental results on nanoporous substrata. The significance of the obtained results for understanding biological wet adhesives is discussed.
昆虫粘性垫的可靠附着能力据说是由于垫的分泌。已经表明，表面粗糙度强烈降低昆虫垫的粘附力。这种效应可以通过粗糙表面减小接触面积和从垫表面快速吸收流体来解释。然而，对于具有不同粗糙度参数和表面能的粗糙基底，流体如何流动仍不清楚。在本文中，我们通过数值研究了接触形成过程中粗糙基底上的流体流动。结果表明，基底结构密度的增加会导致从垫中流失的流体增加：具有精细粗糙度的基底吸收垫中的流体更快。固体基底对流体的亲和力降低对流体损失的影响更为显著，导致流体损失减少。随着基底不规则性（孔隙率）的纵横比增加，流体损失减少。获得的数值结果与先前对昆虫的观察结果和纳米多孔基底的实验结果一致。讨论了所获得的结果对理解生物湿粘合剂的意义。
