Development of a biocompatible patch antenna for retinal prosthesis: comparison of biocompatible coatings

Implantable medical devices are attracting high scientific interest, as they can significantly improve the quality of life of people with chronic diseases. Retinal implants can partially restore vision to the blind with a functional optic nerve. This paper presents the design of biocompatible patch antennas for retinal implants operating at the MedRadio band (401-406MHz). Biocompatibility is ensured by encapsulating the antenna within a biocompatible material. First, a parametric microstrip patch antenna model is considered and the initial antenna design is modified for encapsulation in three different biocompatible materials (Silastic MDX4-4210 medical-grade elastomer, Zirconia and PEEK). Antenna design takes place inside a homogeneous spherical eyeball model in order to take into consideration mismatching caused by surrounding tissues. An automated Quasi-Newton method is used to refine the antenna design in order to achieve the desired tuning properties. The resulting three antenna designs are comparatively assessed in terms of size, tuning properties, safety and radiation performance for telemetry in the MedRadio band (401-406 MHz). Further validation and safety simulations are carried out for antennas implanted in an anatomical eyeball model consisting of four different tissues (sclera, cornea, vitreous humor and lens) in order to explore potential detuning of the antenna caused by its actual operation environment. Simulations for design optimization are performed using the Ansoft HFSS suite, based on the finite element (FE) method, while validation and safety performance studies are carried out using the SEMCAD X suite, based on the finite difference time domain (FDTD) method.