Bio-inspired fluid locomotion

Abstract

We have developed several novel methods of locomotion at low Reynolds number, for both Newtonian and non-Newtonian fluids: Robosnails 1 and 2, which operate on a lubrication layer, and the three-link swimmer which moves in an unbounded fluid. Robosnail 1 utilizes lubrication pressures generated in a Newtonian fluid under a steadily undulating foot to propel itself forward. Tractoring force and velocity measurements are in agreement with analytic and numerical solutions. Robosnail 2, modeled after real land snails, uses in-plane compressions of a flat foot on a mucus substitute such as Laponite or Carbopol. Robosnail 2 exploits the non-Newtonian qualities (yield-stress, shear thinning) of the fluid solution to locomote. The glue-like behavior of the unyielded fluid allows Robosnail 2 to climb up a 90 degree incline or inverted 180 degree surfaces. The three-link swimmer is a device composed of three rigid links interconnected by two out-of-phase oscillating joints. It is the first experimental test that successfully demonstrates that a swimmer of its kind can translate in the Stokes limit.