On the snake-like lateral un-dulatory locomotion in terrestrial, aquatic and sand environments

Terrestrial snakes, aquatic snakes, and sandfish lizards are observed to adopt different configurations for locomotion, although they all employ the snake-like un-dulatory wriggling motion. Here we show that these differences may be dominated by the movement and energy efficiencies imposed by mechanical deformation and interaction with environments. Based on a slender soft beam model, a systematical framework is developed to explore and compare the movement and energy efficiencies of the snake-like lateral undulation in terrestrial, aquatic and sand environments. Indeed, it is found that the locomotion configuration of the soft body is highly relevant to the efficiency factors. Optimal un-dulatory configurations are obtained for each environment, which are qualitatively consistent with the biological ones. The present study reveals the mechanism behind the locomotion adaptation of the un-dulatory wriggling motion for navigating through different environments, which sheds light on developing amphibious/all-terrain soft robots, while, at the same time, broadens our cognition of nature's strategies for locomotion. © 2021 Elsevier Ltd