十万个为什么·科学阅读30篇（2）

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壁虎如何不靠胶水就能在玻璃上倒立行走？

Geckos cling to smooth surfaces using billions of microscopic hair-like structures called setae on their toe pads.
Each seta splits into hundreds of even tinier spatulae that make contact at the molecular level with surfaces.
Van der Waals forces—weak electrostatic attractions between molecules—collectively create strong adhesion.
These forces work equally well in vacuum, underwater, or zero gravity, unlike suction or glue-based methods.
A gecko can support its entire body weight with just one toe, and detach instantly by changing toe angle.
Their feet self-clean with every step, shedding dirt particles that might reduce grip efficiency.
No sticky secretions are involved; the mechanism relies purely on physical surface interaction.
Engineers mimicked this design to create reusable dry adhesives for space tools and medical devices.
Interestingly, larger animals cannot scale up this system due to square-cube law limitations on surface-area-to-mass ratios.
Ongoing research explores how humidity and temperature subtly modulate van der Waals bonding strength.