Figure 5. Numerical simulation of propulsion by reciprocal motion in a shear thickening fluid.

(a) Fluid velocity and viscosity fields around the swimmer in shear thickening fluid (see also Supplementary Movie 4 and Supplementary Fig. 15 for enlarged images). The three images in the upper panel correspond to the fast closing half-cycle (~0.8 s) and the images in the lower panel correspond to the slow opening half-cycle (~3.2 s). The simulation result verifies that the net displacement is a result of the viscosity differences during the two half-cycles, which is caused by the differences in fluid shear rate (velocity gradient) under asymmetric actuation. (b) The displacement curves of the asymmetric actuated macro-scallop in shear thickening (blue) and Newtonian fluid (green) for three cycles. Simulation results (dashed lines) are consistent with experimental data (solid lines), where the macro-scallop exhibits net displacement in the shear thickening fluid but no net displacement in the Newtonian fluid.