Singla Saranshu, Jain Dharamdeep, Zoltowski Chelsea M, Voleti Sriharsha, Stark Alyssa Y, Niewiarowski Peter H, Dhinojwala Ali
School of Polymer Science and Polymer Engineering, University of Akron, Akron, OH 44325-3909, USA.
Integrated Bioscience Program, University of Akron, Akron, OH 44325-3908, USA.
Sci Adv. 2021 May 19;7(21). doi: 10.1126/sciadv.abd9410. Print 2021 May.
While it is generally accepted that van der Waals (vdW) forces govern gecko adhesion, several studies indicate contributions from non-vdW forces and highlight the importance of understanding the adhesive contact interface. Previous work hypothesized that the surface of gecko setae is hydrophobic, with nonpolar lipid tails exposed on the surface. However, direct experimental evidence supporting this hypothesis and its implications on the adhesion mechanism is lacking. Here, we investigate the sapphire-setae contact interface using interface-sensitive spectroscopy and provide direct evidence of the involvement of acid-base interactions between polar lipid headgroups exposed on the setal surface and sapphire. During detachment, a layer of unbound lipids is left as a footprint due to cohesive failure within the lipid layer, which, in turn, reduces wear to setae during high stress sliding. The absence of this lipid layer enhances adhesion, despite a small setal-substrate contact area. Our results show that gecko adhesion is not exclusively a vdW-based, residue-free system.
虽然普遍认为范德华力主导壁虎的黏附，但多项研究表明非范德华力也有贡献，并强调了解黏附接触界面的重要性。此前的研究假设壁虎刚毛表面是疏水的，非极性脂质尾部暴露在表面。然而，缺乏支持这一假设及其对黏附机制影响的直接实验证据。在这里，我们使用界面敏感光谱研究蓝宝石-刚毛接触界面，并提供直接证据表明刚毛表面暴露的极性脂质头部基团与蓝宝石之间存在酸碱相互作用。在分离过程中，由于脂质层内的内聚破坏，一层未结合的脂质作为痕迹残留下来，这反过来又减少了高应力滑动过程中刚毛的磨损。尽管刚毛与底物的接触面积很小，但这种脂质层的缺失增强了黏附力。我们的结果表明，壁虎的黏附并非完全基于范德华力的无残留系统。
