Design And Experiments Of A Magnetically Actuated Microrobot System At The Air-liquid Interface

Micron-sized robots have huge potential applications in microfabrication, life science experiments, bio-medical fields and so on. For microobjects at the air/water interface, surface microforces dominate the gravity and buoyancy force, then the objects under certain conditions will always float at the air/water interface stably. The air-liquid interfaces have low drag force compared with solid surfaces, then it is another choice for microfabrication and microassembly at those interfaces. It is therefore important to study microrobots at the air/water interfaces.In this paper, a magnetically actuated microrobot at the air/water interface was designed, The main contents include the static analysis and dynamic model of the microrobot at the air/liquid, the generation and control of magnetic field and magnetic force, structural design of the magnetic actuation device and experimental platform building to accomplish the relevant motion experiments.Firstly, the static models of the typical parts such as microspheres and micro cylinders were established to calculate the forces acting on them. Based on the solution of Young-Laplace equation, the force-distance curve for microsphere and micro cylinders respectively, Influence of contact angles, and geometric parameters on the force were analyzed. Hydrophobic surface treatment measurements were performed to increase the contact angle for obtaining greater load-bearing capacity, then related experiments were executed to verify the theoretical analysis. Based on the analysis of two different manufacture methods, laser cutting was used to fabricate the microrobots.Secondly, according to the analysis and comparison of the different ways to generate a magnetic field, magnetic model of an air-core solenoid was established, calculation and simulation of the magnetic field and magnetic force as well as control strategy were accomplished. Based on the influence of coil parameters on the magnetic field and magnetic field gradient and the requirements of system, the spatial arrangement of coils were determined, and the magnetic field in the work area was analyzed. Some experiments were carried on to verify the relationship between magnetic field and currents as well as the superposition of magnetic field produced by multiple coils. The dynamic model and the control strategy of the microrobot were also built.Finally, the microrobot system actuated by electromagnetic coils was built, including hardware modules and software modules. Some motion tests were accomplished by using various parameters of waveform and amplitude of the current, shape and size of the microrobot, liquid medium during the motion experiments. Motion towards different directions was realized, and track deviation and motion repeatability were calculated. The results showed that the maximμm average speed of the microrobot at the deionized water was 470μm/s and the maximμm repeatability was 30.2μm.