A Wireless Power Transfer System Based on a Hybrid Transmitting Coil for Targeted Therapy Microrobots in the Intestine

A wireless power transfer system for targeted therapy microrobots has been received more attention recently. However, it usually fails to work due to weak coupling caused by misalignment in position and angle between the transmitting coil and the receiving coil. It will not be tolerated even if it occurs at certain angles. To address this issue, a three-dimensional hybrid transmitting coil, combining a fixed Helmholtz coil pair and an adjustable curved rectangular coil pair, is proposed. Based on the novel structure, the proposed hybrid transmitting coil could produce a three-dimensional magnetic field, realizing well coupled with the receiving coil embedded on the microrobot at any posture. To verify the efficiency and practical applicability of the transmitting coil proposed in this paper, we build the coil model via both analytical calculation and simulation analysis. Finally, the designed hybrid transmitting coil is also implemented in the wireless power transfer system with a receiving coil. The magnetic field distribution indicates that a large and uniform magnetic field could be obtained. The experimental results demonstrate that in the central zone of the transmitting coil, 300 x 200 mm, the magnetic field distribution is uniform, which can meet the requirements of the microrobot system working area. And the maximum output efficiency and power can be reached at 5% and 1001 mW, respectively. What's more, the proposed hybrid transmitting coil has solved the weak coupling problem due to misalignment in position and angle with which the electromagnetic energy decays quickly.