Research On Structure Design And Motion Mechanism Of Magnetic Driven Double Curved Conical Micro-helical Robot

With the maturity of micro/nano manufacturing technology and magnetic drive technology,as well as the increasing demand for micro/nano robots in biomedicine,microfluidic chips,micro/nano engineering and other fields,magnetic driven micro-helical robot technology has been developed rapidly.The biggest characteristic of the magnetic driven micro-helical robot is that it swims in a spiral propulsion mode driven by an external rotating uniform magnetic field,so it can realize efficient swimming in a liquid environment with a low Reynolds number.Although a variety of magnetic driven micro-helical robots with different structures have been successfully made,they still have some problems in the actual swimming process,such as weak propulsion force,low stability,easy to be interfered by external complex environment,and easy to appear uncontrollable swing under low-frequency spiral propulsion.Therefore,it is of great significance to study the structure and driving system of the magnetic driven micro-helical robot and improve the swimming performance of the micro-helical robot.In this paper,a magnetic driven micro-helical robot with micron scale was studied.The structure design and swimming mathematical model of micro-helical robot were studied by simulation.A magnetic drive system was built to drive the micro-helical robot,and the experimental research on the swimming performance of the micro-helical robot was carried out on the basis of the high-precision manufacturing of the micro-helical robot.(1)Based on the principle of helical propulsion,the dynamic characteristics of magnetic driven micro-helical robot were studied.The models of magnetic driven micro-helical robots with different geometric characteristics were established,and their magnetization characteristics and swimming performance were analyzed by simulation.A kind of double curved conical ribbon micro-helical robot was further proposed,then the influence of geometric parameters such as helix angle,helical length,cone angle and the number of thread on the swimming performance of the double curved conical ribbon micro-helical robot were explored.A mathematical model for preliminary calculation of the swimming speed of a ribbon micro-helical robot was established by using the element method.(2)Based on the driving mechanism of uniform magnetic field,the magnetic drive system of micro-helical robot was designed.The principle of uniform magnetic field generated by Helmholtz coil was analyzed.The relationship between the center strength of the uniform magnetic field generated by the Helmholtz coil and current,coil turns,coil average radius was obtained by simulation.The influence of coil section shape,coil shape,the ratio of the distance between two current-carrying coils and coil average radius on the performance of Helmholtz coil was explored.A 3D Helmholtz coil magnetic drive system was designed,and a conical rotating 3D uniform magnetic field was proposed to improve the swimming efficiency and controllability of the micro-helical robot at low speed.(3)The swimming performance of magnetic driven micro-helical robot was studied though experiments.The driving system of magnetic driven micro-helical robot was built.A transverse bidirectional fold-line scanning real 3D fabrication method based on two photon polymerization direct laser writing technology was proposed,and the high precision manufacturing of magnetic driven micro-helical robot was carried out on the basis of optimizing the processing parameters.The swimming performance of the magnetic driven micro-helical robot with different geometric characteristics and parameters was explored through experiments,which proved that the double curved conical structure was beneficial to improve the swimming performance of the micro-helical robot,and the results of dynamic theory analysis were verified.The high-stability,non-swinging,low-frequency spiral propulsion and high-precision controllable swimming of magnetic driven micro-helical robot were realized by using conical rotating 3D uniform magnetic field.