Biocompatibility and implant of a less invasive intraocular pressure sensor

Abstract

We discussed the design and fabrication consideration for an Intraocular Pressure (IOP) systems according to surgical and biocompatibility implant limitations. A new less invasive IOP system is implanted successfully in the eye of a rabbit by a minimum invasive surgical procedure. The MEMS array is over a flexible, biocompatible polyimide substrate in a maximum 8×8mm area. The substrate flexibility allows it to fit a small surface of the eye. The implanted coil is under the conjunctiva, out of the interior chamber. However, the pressure sensor is deposed inside the interior chamber through a minimum invasive procedure. The capacitive sensor is fabricated considering a maximum area of 0.5×0.5mm2. Increasing sensor capacitance is achieved by a set of windows cavities getting a sensible reduction of the separation of its capacitor plates at the base of the windows anchored. The coil and pressure sensor consist of alternating layers of polyimide–metal–polyimide, patterned using reactive ion etching over a thin silicon wafer that is used only as a sacrificial layer. We pointed out the way micron-scale metal layers can be incorporated in a thin flexible plastic substrate to integrate into the same process both: the coil and the intraocular pressure sensor. The whole structure encapsulated in a biocompatible polymer fits into the shape of the ocular globe.