Dynamics of magnetoelastic robots in water-saturated granular beds

Abstract

We investigate the dynamics of magnetoelastic robots as they move through a water-saturated granular bed with transverse undulation of the body being actuated by an oscillating magnetic field. The robots create dynamic burrows as they fluidize the medium and move with speeds that depend on the field frequency and strength and the sediment depth. A transition from nearly rigid to anguilliform body motion is observed because of a subtle balance of thrust, drag, and elastic forces. The overall trends in the robot's speed are generally consistent with Lighthill's theory of elongated body swimming.