Sidewinding with minimal slip: Snake and robot ascent of sandy slopes

TLDR

Snakes, particularly sidewinder rattlesnakes, can navigate inclined sandy slopes that cause limbless robots to slip and pitch. By increasing body contact length on steeper sand, sidewinder rattlesnakes enable a robot to climb near the maximum stable slope, demonstrating that contact‑length control mitigates failure on granular media.

Abstract

Limbless organisms such as snakes can navigate nearly all terrain. In particular, desert-dwelling sidewinder rattlesnakes (Crotalus cerastes) operate effectively on inclined granular media (such as sand dunes) that induce failure in field-tested limbless robots through slipping and pitching. Our laboratory experiments reveal that as granular incline angle increases, sidewinder rattlesnakes increase the length of their body in contact with the sand. Implementing this strategy in a physical robot model of the snake enables the device to ascend sandy slopes close to the angle of maximum slope stability. Plate drag experiments demonstrate that granular yield stresses decrease with increasing incline angle. Together, these three approaches demonstrate how sidewinding with contact-length control mitigates failure on granular media.