Propulsion devices for locomotion at low-Reynolds number

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2004.Includes bibliographical references (leaves 65-66).We have designed, built, and tested three novel devices that use low-Reynolds number flows for self propulsion. The three-link swimmer is designed to swim through in a free viscous fluid using cyclic flipping motion of two rigid fins attached to a rigid midsection. Robosnail 1 uses lubrication pressures underneath a flexible, sinusoidally waving boundary to generate thrust, and Robosnail 2 uses five independently controlled translating feet segments to move on a layer of 8 percent Laponite, a shear thinning clay suspension which gives it the ability to adhere to and scale inclines and inverted surfaces. The three link swimmer was found to travel up to 0.034 body lengths per four-stroke cycle, Robosnail 1 was found to move at a speed of roughly half the wave speed of the foot (measured with respect to the snail), a result consistent for wave speeds between 0 and 2 cm/s. Robosnail 2 was able to move forward at all inclines from zero to 180 degrees inverted, with back-slip ranging from 40 to 80 percent.by Brian Chan.S.M

Bio-inspired fluid locomotion

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2009.Includes bibliographical references (leaves 95-99).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.by Brian Chan.Ph.D