High Efficiency Double - Paired Inductive Coils for Wireless Powering of a Retinal Prosthesis

Wireless powering of a retinal prosthesis is necessary for continuous operation of the implanted device in a blind patient. Inductive link has the potential for transferring power wirelessly to such an implanted device inside the eye. However, constant motion of the eye and changes in electrode-tissue impedance results in a decrease in the inductive link efficiency. In this paper, we present a novel method to improve the efficiency of the inductive link by introducing an intermediate pair of coils to close the gap between two coils with large separation. Based on our theoretical formulation, the power transfer efficiency of the double-pair coil link is estimated to exceed the efficiency of a single-pair coil when the coupling coefficient can be improved by a conservative value of 3 times. We fabricated the double-pair coils using flexible printed circuit board technology. Measurement result confirms our initial expectation. By implementing this design, we aim to provide sufficient power for next generation retinal prosthesis which has electrode count exceeding 1000 and can consume upwards of 50 mW of power.