Crawlers in viscous environments: Linear vs non-linear rheology

We study model self-propelled crawlers which derive their propulsive capabilities from the tangential resistance to motion offered by the environment. Two types of relationships between tangential forces and slip velocities are considered: a linear, Newtonian one and a non-linear one of Bingham-type. Different behaviors result from the two different rheologies. These differences and their implications in terms of motility performance are discussed. Our aim is to develop new tools and insight for future studies of cell motility by crawling.

► We analyze model, self-propelled crawlers on viscous substrates.
► Both linear (Newtonian) and non-linear (Bingham-type) substrates are considered.
► We show that exploiting non-linearities is the key to achieve motion by shape change.
► Large strains allow for net advancement even in the case of a linear rheology.
► The direction of motion can be inverted by changing the substrate's rheology.