Meeting Abstract
Geckos agilely maneuver on smooth surfaces using millions of tiny foot hairs (setae) that attach via van der Waals interactions. The morphological arrangement of the setae results in toes possessing directional sensitivity generating more force when pulled by the foot. Geckos tend to align their toes more vertically against gravity when racing up walls. We hypothesized that toes represent an opportunity for distributed control, whereby their alignment can be actively adjusted to remain more oriented against the gravity vector as geckos change direction on vertical surfaces. To test the hypothesis, we ran Tokay geckos sideways on a transparent acrylic wall while measuring orientation with high-speed cameras and contact area of the setae using frustrated total internal reflection. We used vertical climbing of the same individual as our control. Sideways wall running geckos aligned the toes of their top fore and hind feet against gravity, more like the toe orientation observed in the front feet during vertical climbing. Contact area was not compromised, but redistributed among toes to generate adequate forces. To further test the hypothesis, we induced slipping and discovered strong passive toe alignment against gravity. We conclude that distributing control among multiple adjustable structures can increase the effectiveness of maneuvers in complex environments.
