Research On Multi-Structure 3D Printing And Multimodal Motion Of Magnetically Driven Micro Soft Robots

Micro-robotics is an emerging research field dedicated to exploring the drive,control,and working capabilities of tiny automated devices in a microscopic environment.Due to scale effects,many phenomena at the microscopic scale differ greatly from those at the macroscopic scale,while the functional modules and mechanical structures used in macroscopic robots are difficult to miniaturize.Therefore,micro robots have completely different functional structures and motion mechanisms from macro robots.New designs and functions require new functional materials,processing methods,drive principles,and control methods to implement and support them,driving researchers to invent and discover untrodden practical approaches.Micro flexible robots are an important direction for micro robotics research.With the natural deformation of flexible materials,micro soft robots can achieve active or passive deformation without the use of complex mechanical structures to obtain the power to propel themselves forward.Most of the current methods for processing micro soft robots are limited by traditional machining techniques and soft material curing methods,which are not suitable for manufacturing more diverse micro soft robot shapes and structures,and are not conducive to exploring more novel and complex micro soft robot motion mechanisms.To address this current situation,this paper proposes a 3D printing manufacturing method of micro soft robots with multiple planar structures based on surface tension control of liquid material mobility.To explore more possibilities in the field of micro soft robots,this paper investigates the areas of a micro 3D printing system,composite magnetic field driving systems,fabrication and motion modes of micro soft robots with multiple structures,and independent control strategies for multiple different types of robots.In terms of the micro 3D printing system for micro soft robots,by analyzing the surface tension that the liquid is subjected to on the solid surface and the Marangoni effect due to the surface tension,the 3D printing method of changing the substrate surface tension distribution with the help of auxiliary materials,and controlling the horizontal shape and structure of various materials is proposed.The effectiveness of the 3D printing method is verified by finite element simulation,and the stability of the variable non-Newtonian fluid printing process is improved.A software framework that allows rapid adjustment of printing parameters and printing processes is developed based on a micro 3D printing system with micron-level printing accuracy.Using the micro 3D printing system,a variety of functional structures are printed,including UV-curable adhesive auxiliary lines for dividing areas,auxiliary blocks that can be used as mold borders,and silicone areas with and without magnetic powder for forming the robot body.Patterned printing and double-layer printing are also realized.In terms of the fabrication and motion mode of the head-and-tail micro soft robot,a two-dimensional composite magnetic field drive device consisting of two Helmholtz coil sets is constructed to realize the superposition drive of different types of magnetic fields with the help of finite element simulation results.A micro magnet robot floating on the water surface is precisely synchronized to control its own angle and motion direction to verify the control accuracy of the composite magnetic field drive system.Micro soft robots with single-tailed and double-tailed structures are designed and manufactured,then magnetized along different directions.Glycerol with high viscosity is selected as the experimental environment,and the robots are driven using a rotating magnetic field,an oscillating magnetic field,and a static gradient magnetic field.The effects of various types of magnetic fields on the swimming performance of robots with various structures and sizes are experimentally investigated.In terms of the fabrication and motion pattern of the micro soft robot with ring magnetization,a sheet-shaped micro soft robot is printed,bent into a ring shape,and then magnetized.The deformation and total magnetic moment of the robot under a magnetic field are obtained by finite element simulation,and the simulation results are verified by deformation and lifting experiments.A rotating magnetic field is used to drive the rotation of the robot,which is driven to roll along the solid-liquid interface by the effect of the solid interface on the fluid flow,and a static strength magnetic field is superimposed to adjust the rolling speed and direction of the robot.An oscillating magnetic field with alternating strength and direction is used to drive the robot in a double-ended walking motion at the solid-liquid interface,and a static gradient magnetic field is superimposed to adjust the robot’s walking speed and swimming height.Varying the oscillating mode of the oscillating magnetic field drives the robot to perform a single-end hopping motion along the solid-liquid interface,the robot’s hopping speed and direction are adjusted by a magnetic field gradient.In the independent motion control of multiple micro soft robots,the vector transformation from local to the global coordinate system is established to realize the superposition control of any type of magnetic field in any direction.The solution equations for the independent motion of two micro soft robots with different motion speeds at arbitrary distances are established,and the independent motion control effects of various combinations of different types of dual robots driven by different types of magnetic fields are experimentally verified.For the case of three micro soft robots moving independently,the total displacement of the ring magnetized micro soft robot is controlled to be zero when the other robot is moving with the help of an additional static magnetic field to regulate the motion performance of the ring magnetized micro soft robot.Based on this strategy the independent motion problem of three robots is simplified to the independent motion problem of two robots,and the independent motion control effect of various three-robot combinations is experimentally verified.