A Low Reynolds Predator

Here we introduce a two-dimensional (2D) low-Reynolds swimmer and discuss the motion of the swimmer both in noise-free and stochastic regimes. Three spheres, linked by extensible arms, in a plane form the triangle body of micro-swimmer. Expansion and contraction of two-stated linkers in appropriate order causes both translational and rotational movement of the swimmer. It is shown that the motion of the swimmer could be controlled from a rotor to a directed linear swimmer depend on the sequence of the linkers activities. A few amount of noise in the the rhythm of the cycles introduces an interesting "random arc", while in the case of completely stochastic activity of the linkers the swimmer goes to a regular diffusive regime. Moreover, we show that in response to an external source of disturbance, the swimmer may approach or escape the source and shows interesting chemotaxis behavior. It is also shown that the model swimmer can easily be generalized to three dimensions or more complicated geometries.