A Mobile Paramagnetic Nanoparticle Swarm with Automatic Shape Deformation Control

Recently, swarm control of micro-/nanorobots has drawn much attention in the field of microrobotics. This paper reports a mobile paramagnetic nanoparticle swarm with the capability of active shape deformation that can improve its environment adaptability. We show that, by applying elliptical rotating magnetic fields, a swarm pattern called the elliptical paramagnetic nanoparticle swarm (EPNS) would be formed. When changing the field ratio-alpha (i.e. the strength ratio between the minor axis and major axis of the elliptical field), the shape ratio-beta of the EPNS (i.e. the length ratio between the major axis and minor axis) will change accordingly. However, automatically control this shape deformation process has difficulties because the deformation dynamics has strong nonlinearity, model variation and long time requirement. To solve this problem, we propose a fuzzy logic-based control scheme that utilizes the knowledge and control experience from skilled human operators. Experiments show that the proposed control scheme can stably maneuver the shape deformation of the EPNS with small overshoot, which cannot be achieved by conventional PI control. Moreover, experimental results show that, with the automatic shape deformation control, shape of the EPNS is controlled with high reversibility and also can be well maintained during the planar rotational and translational locomotion of the EPNS.