Abstract

Research on the adhesive locomotion of terrestrial gastropods is gaining renewed interest as it provides a source of guidance for the design of soft biomimetic robots that can perform functions currently not achievable by conventional rigid vehicles. The locomotion of terrestrial gastropods is driven by a train of periodic muscle contractions (pedal waves) and relaxations (interwaves) that propagate from their tail to their head (direct waves). We study the locomotion of these animals on smooth flat surfaces by measuring the three-dimensional displacements of the ventral foot surface induced by the passage of the waves. Moreover, we also measure, with high temporal and spatial resolution, the propulsive forces that terrestrial gastropods generate while crawling on smooth flat surfaces. Finally, a simple model based on lubrication theory is proposed in accordance with the experimental observations. This model uncovers a new mode of locomotion that works even when the lubricant between the foot and the animal is Newtonian, thanks to the synchronization between the vertical and the horizontal motion of the foot. The model can also be adapted to situations where the animal’s foot is in contact with the ground only at discrete points, as is the case when it crawls on a wire mesh or on rough soil surfaces.