Design of a wireless power transfer system for devices carried by a freely moving animal in cage

Techniques of long-term in-vivo electrophysiological recording play important roles in brain research and neural rehabilitation. To avoid interruption of experiment and risk of infection, use of wireless power transfer (WPT) technique has recently been suggested to eliminate cumbersome wires and batteries attached to the animals in rodent electrophysiological applications. This paper presents a holistic assessment of the relationships among the physical sizes of the transmitting and receiving coils, power transfer characteristics, and specific absorption rate (SAR) in animals of a simple WPT system using two rectangular coaxial transmitting coils. A 100mW prototype with an operating zone of 400 × 240 × 40mm³ and a receiving coil with a diameter of 11.45mm is built and studied. The SAR in the animal is evaluated and compared with the recommended restriction level.