LAUSR

We study the motility of model cells and biomimetic soft objects crawling over a substrate covered with adhesive linkers. The cell exerts traction forces on the substrate through the active periodic motion of molecular complexes to which the linkers bind and unbind stochastically. We first show that the diffusion coefficient of a force dipole (unable by symmetry to perform directed motion) is maximal for a finite ratio of the unbinding to binding rates, highlighting the role of adhesion kinetics on cell translocation. We next show that cells exerting more complex traction force distributions may exhibit directed motion only if the linkers are mechanosensitive, i.e., if the bonds' lifetime decreases (slip bonds) or increases (catch bonds) under stress. The average migration speed is higher in the catch-bond regime but so are the fluctuations, yielding a biased diffusive motion characterized by a Peclet number smaller than in the slip-bond regime.