Hybrid control of magnetic micro-robot using three-axis Helm-holtz coil

Magnetic robots and their magnetic manipulation systems are innovative approaches for the diagnosis and therapy of minimally invasive medicine. Medical magnetic robots have been applied to targeted drug delivery, drilling in blood vessels, and a robotic capsule-endoscope for diagnosis and therapy [1–3]. Typically, the magnetic robots are controlled by various types of magnetic field: gradient, alternating, rotating, and uniform magnetic fields. The combination of Maxwell coil and Helmholtz coil are general configuration of magnetic manipulation system. However, the configuration is complicated and many power sources are required. To overcome these issues, we proposes a new method of hybrid control of magnetic fields for magnetic micro-robot manipulation based on three-axis Helmholtz coil. The hybrid control utilizes both gradient and uniform fields through switch control of the three-axis Helmholtz coil. For hybrid control, we utilizes 9 relay switches. Three switches separate the x, y and z coils. Six switches separate configuration of Helmholtz coil. In other words, three Helmholtz coils becomes six coils. When generating a rotating magnetic field, the six switches are turned on. When controlling the gradient field, the six switches are selectively turned off according to the moving direction. The hybrid control can provide precision control of micro/nano robot. In addition, the control method with system can be applied to micro/nano robot control without limitation to the robot mechanisms. To verify these advantages, we conducted various experimental tests.