Izadi Hadi, Stewart Katherine M E, Penlidis Alexander
Department of Chemical Engineering, Institute for Polymer Research (IPR), University of Waterloo, Waterloo, Ontario, Canada N2L 3G1.
Department of Chemical Engineering, Institute for Polymer Research (IPR), University of Waterloo, Waterloo, Ontario, Canada N2L 3G1
J R Soc Interface. 2014 Sep 6;11(98):20140371. doi: 10.1098/rsif.2014.0371.
Geckos, which are capable of walking on walls and hanging from ceilings with the help of micro-/nano-scale hierarchical fibrils (setae) on their toe pads, have become the main prototype in the design and fabrication of fibrillar dry adhesives. As the unique fibrillar feature of the toe pads of geckos allows them to develop an intimate contact with the substrate the animal is walking on or clinging to, it is expected that the toe setae exchange significant numbers of electric charges with the contacted substrate via the contact electrification (CE) phenomenon. Even so, the possibility of the occurrence of CE and the contribution of the resulting electrostatic interactions to the dry adhesion of geckos have been overlooked for several decades. In this study, by measuring the magnitude of the electric charges, together with the adhesion forces, that gecko foot pads develop in contact with different materials, we have clarified for the first time that CE does contribute effectively to gecko adhesion. More importantly, we have demonstrated that it is the CE-driven electrostatic interactions which dictate the strength of gecko adhesion, and not the van der Waals or capillary forces which are conventionally considered as the main source of gecko adhesion.
壁虎能够借助其脚趾垫上的微米/纳米级分层纤维（刚毛）在墙壁上行走并倒挂在天花板上，这使其成为纤维状干粘合剂设计与制造的主要原型。由于壁虎脚趾垫独特的纤维状特征使其能够与它行走或附着的底物紧密接触，因此预计脚趾刚毛会通过接触起电（CE）现象与被接触的底物交换大量电荷。即便如此，几十年来，CE发生的可能性以及由此产生的静电相互作用对壁虎干附着力的贡献一直被忽视。在本研究中，通过测量壁虎脚垫与不同材料接触时产生的电荷量以及附着力，我们首次阐明CE确实对壁虎的附着力有有效贡献。更重要的是，我们已经证明是CE驱动的静电相互作用决定了壁虎附着力的强度，而不是传统上被认为是壁虎附着力主要来源的范德华力或毛细力。
