Self-Propelled Particles with Rotationally Asymmetric Shape

Abstract

The research into the controllable micron-sized self-propelled particles provides basic principles for various applications such as micro robots, cell manipulation, drug delivery, etc. It is well known that we can adopt the fields such as concentration fields, temperature fields, and electric fields as the power source of self-propelled particles. Generally, the symmetry of the fields around particles is highly related to the shape of the particles. Utilizing this fact, recently, there are many attempts to realize various types of motion using rotationally asymmetric particles. By the control of the shape, the net torque and the net force exerted to the particles are finely controlled. This review article highlights the pioneering studies of the motion control of the self-propelled particles by the shape control. Not only the particles with fixed shapes but also the deformable self-propelled particles are introduced. The motions induced by the deformation are discussed with both the experimental studies and the theoretical studies. For the further development, we also introduce the recent development of the methods to produce rotationally asymmetric microparticles including our new easy-to-use method. We expect that these approaches will be useful for the wide range of applications in physical, life and biomedical science. Keywords: Active matter, asymmetric shape, micro robots, nonequilibrium, self-propelled particle, soft matter.