The focus of this paper was the flexible electrode and flexible coil components in which parylene C is used not simply as a coating, but as the structural material as well.  Parylene C was chosen as the structural material because parylene is pinhole-free, uniformly conforming, its low water permeability, its USP Class VI biocompatibility, and its high flexibility and mechanical strength.

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 of 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 bio-stability when chronically implanted in contact with canine retinas.

Sources:

Parylene-Enbled Flexible Prosthetic Devices.  Y.C. Tai, et. al.  California Institute of Technology.  05/03/2007.