Parylene-Enabled Flexible Prosthetic Devices: A Review

The flexible electrode and coil components utilize Parylene C as both a coating and structural material. Parylene C is selected for its pinhole-free nature, uniform deposition, low water permeability, flexibility, mechanical strength, ISO 10993 biocompatibility and USP Class VI rating.

Inductive coupling of a pair of coils is a promising technology for wireless power and data transmissions to implanted medical devices. In order for a coil to remain inside the human eye, it has to be mechanically durable, flexible, small enough for intraocular implantation, and chemically stable. Current devices are thick and very stiff, often leading to notable degradation in the area of implantation.

The implantable coil was fabricated using a six-step process involving standard silicon wafers, metal etching and three layers of Parylene. The flexibility of Parylene was a large benefit during the manufacturing process.

Accelerated testing predicted that the Parylene package can remain intact at the body’s normal temperature (37ºC) for over 20 years. The Parylene arrays were chronically implanted in the right eye of two canines for four and five months with normal blood vessel filling.

Their revolutionary Parylene-based RF coils have shown remarkable accelerated-lifetime stability and excellent biostability when chronically implanted in contact with canine retinas.
 
Sources:
 Parylene-Enabled Flexible Prosthetic Devices. Y.C. Tai, et. al. California Institute of Technology. 05/03/2007.