Enhancing the performance of soft actuators with magnetic patterns

Abstract

This study presents a concept for a straightforward method to enhance the actuation performances of magneto-active elastomer membranes. The concept is based on a characteristic magnetization pattern and offers a solution to two major difficulties in the actuation of thin and mechanically soft magnetic actuators: the localization of actuation forces and the self-demagnetization. After the magnetization process, the membrane presents two regions with an oppositely oriented out-of-plane magnetization. The magnetized regions are separated by a transition zone which is called magnetic pole transition. Experimental investigations reveal a high magnetic flux density near the pole transition—even in the center of bidirectionally magnetized membranes—whereas the magnetic flux density of a uniformly magnetized membrane decreases toward the center. In additional experiments, membranes with both magnetization patterns are actuated by stiff permanent magnets. The resulting out-of-plane displacement of the bidirectionally magnetized membrane exceeds the displacement of the unidirectionally magnetized membrane by far. The investigations demonstrate that this enhancement stems from the presence of the magnetic pole transition. All experiments are reproduced using magnetic and magneto-mechanical numerical models; a good accordance between the results is achieved.