Wireless Implantable Intraocular Pressure Sensor with Parylene-Oil-Encapsulation and Forward-Angled RF Coil

This paper presents a wireless and implantable intraocular pressure (IOP) sensor with parylene-oil-encapsulation packaging using a novel folded PCB architecture accomplishing practical RF coupling for power and data in a rabbit. The sensor is operated with an air gap of 5 mm between the primary coil and the animal, coupling to an on-chip coil at an input power of 32 dBm at 915 MHz, and can also be operated when the eyelid covers the sensor. Additionally, two novel results for parylene-on-oil deposition in general are presented. First, we show that the thickness of the porous layer of parylene-C (PA-C) and parylene-HT (PA-HT) deposited on silicone oils have a logarithmic decrease in porous layer thickness (PLT) versus silicone oil molecular weight (MW) over a range of 2-139 kDa. Second, we directly verify that parylene-oil-encapsulated pressure sensors retain sensitivity despite material buildup for the first time.