A MEMS intraocular origami coil
This work presents a MEMS intraocular coil which is designed to be flexible, biocompatible and electrically efficient as the secondary power coil of inductive coupling links for retinal prostheses applications. A microfabricated structure of parylene-gold-parylene is combined with a folding technique to create a conducting strip with increased cross-section and length than is possible without folding, which is then wound to form a single-layer coil. Compared with the wire-wound coil and MEMS planar coil, our strip-fold-and-wound origami coil can better fulfill the size, mass, and flexibility requirements of an intraocular implant, and also reduce the proximity effect and achieve high quality factor at the targeted frequency. As an example, a 5-turn prototype coil of 10 mm outer diameter, 1 mm thickness and 10 mg weight in saline, has an inductance of 480 nH and reaches a maximum Q factor of 12.5 at 30 MHz. A further increase of Q factor can be achieved by increasing the equivalent cross-sectional area by depositing thicker metal.