Geckos adhere to smooth surfaces due to what forces generated by their toe pads?

Geckos adhere to smooth surfaces due to what forces generated by their toe pads?

• A. Capillary suction
• B. Magnetic attraction
• C. Electrostatic attraction
• D. van der Waals forces generated by setae.

Answer: (D)

Geckos stick to smooth surfaces because their toes are covered with countless tiny fibers called setae. Each seta ends in an even finer tip that can make extremely close contact with the surface, and all those microscopic contacts add up to a large overall contact area. The attractions at those contacts are van der Waals forces—weak intermolecular pulls that become strong when summed over millions of contact points. This dry adhesion works on dry surfaces without any liquid or suction, which is why geckos can climb walls and even ceilings. When they want to detach, they peel their toes to break many of these contacts in sequence, allowing a smooth release.

Geckos stick to smooth surfaces because their toes are covered with countless tiny fibers called setae. Each seta ends in an even finer tip that can make extremely close contact with the surface, and all those microscopic contacts add up to a large overall contact area. The attractions at those contacts are van der Waals forces—weak intermolecular pulls that become strong when summed over millions of contact points. This dry adhesion works on dry surfaces without any liquid or suction, which is why geckos can climb walls and even ceilings. When they want to detach, they peel their toes to break many of these contacts in sequence, allowing a smooth release.