Tunable rebound of millimeter-sized rigid balls by magnetic actuation of elastomer-based surface microstructures

A novel method for controlling the rebound behavior of small balls made of Al2O3 with a radius of 2.381 mm is presented. It uses different types of micro-structured surfaces of soft magnetoactive elastomers. These surfaces were fabricated via laser micromachining and include fully ablated surfaces as well as micrometer-sized lamellas with a fixed width of 90 mu m, height of 250 mu m and three different gap sizes (15, 60 and 105 mu m). The lamellas can change their orientation from edge-on to face-on configuration according to the direction of the external magnetic field from a permanent magnet. The orientation of the external magnetic field significantly influences the rebound behavior of the balls, from a coefficient of restitution e of approximate to 0.5 to < 0.1. The highest relative change in the coefficient of restitution between zero field and face-on configuration of approximate to 80% is observed for lamellas with a gap of 60 m. Other characteristics of the ball rebound such as the penetration depth into an Magnetoactive elastomer and the maximum deceleration are investigated as well. The proposed method does not require a constant power supply due to the use of permanent magnets. It may find novel applications in the field of impact engineering.