Design And Experiments Of Magnetically Actuated Helical-microswimmers System

The microrobots technology has made great progress, with the development of the micro-scale and nano-scale techniques, and increasing demand of health care and micro manufacturing systems,. The magnetically actuated helical swimmers gain wide attention for high efficiency and precision. So far, the researches on helical-swimmers mainly concentrate on millimeter- scale or larger, and there are differences in theoretical analysis among various scales. Thus, it is of great meaning to do some research on submillimeter-scale helical-swimmers.Here, the dynamics model is established for micro swimmers in fluid. The Helmholtz coils are designed to actuate the micro swimmers and based on which a motion control strategy is proposed. Magnetically actuated helical-microswimmers system is built and experiments analysis and verification are also presented.First, the dynamics of the helical micro swimmers is modeled and analyzed. In conditions of low Reynolds number, the dynamics is obtained based on the resistive force theory. Based on which the influence of radius, length and pitch of helical tail on the velocity and efficiency of swimmers are discussed, and the parameters are obtained which make the best performance of the swimmers. The maximum torque magnetic field can produced is calculated, the step-out frequency is introduced to develop the principle between the maximum velocity of the swimmers and structure parameters. Furthermore, the double-helix structure is proposed and analyzed.Secondly, the magnetically actuating system is built. The working principle of Helmholtz coils is analyzed and simulated by COMSOL Multiphysics, and the Magnetic field distribution characteristics of coils is obtained. Three-pair Helmholtz coils are designed based on simulation results to fulfill the requests of experiments. The motion of swimmers along any axis is controlled by use of rotation of coils magnetic field in the space. Experiments are carried out to test the characterization of the magnetic field produced by designed Helmholtz coils.Finally, experiments for magnetically actuated helical-microswimmers are carried out. The experiment system is built based on the magnetically actuated module, and magnetically actuated helical-microswimmers in different sizes are produced. Swimmers motion characteristics experiments are carried out in the conditions of different environment and different geometry parameters. The motion characteristics of double-helix swimmer and helix swimmer are compared through experiments results, and the superposition property of double-helix swimmers are verified. The magnetically actuated helical-microswimmers motion control experiment is carried out to verify the repeatability of the motion.