Multi-electrode Arrays with Non-hermetic Encapsulation for Neural Prostheses

DESCRIPTION (provided by applicant): Neural prostheses presently in commercial use employ foil and wire electrodes connected to implantable pulse generators (IPGs) housed in hermetically sealed titanium cans. Each electrode is individually connected to the IPG by insulated multistrand wire assembled into a flexible lead. This construction constrains treatment options by limiting the number and size of the electrodes that can be used in a prosthesis. Our objective is the development of polymer-based multielectrode arrays that overcome these limitations. The arrays are polyimide-based with electrode sites suitable for iridium oxide and other low-impedance, high charge capacity coatings. The enabling innovations are 1) the use of a thin-film inorganic dielectric encapsulation and adhesion layer that provides hermetic-like barrier properties and 2) a non-hermetic encapsulation that employs thin films of surface-functionalized dielectrics and silicone-based sealants. The non-hermetic encapsulation will allow placement of application specific integrated circuits (ASICs) directly on the arrays and will replace the traditional titanium or ceramic case used to house batteries, pulse generators, and communications circuitry. The combination of silicone encapsulants covalently bonded to thin-film inorganic dielectrics is expected to protect active circuitry and electrical interconnects on the arrays for the life of the patient. The advantages of the proposed technology, relative to previous thin-film approaches and existing clinical multielectrode leads and IPGs include: 1) a non-hermetic encapsulation that provides chronic protection of metallization, ASICs, and interconnects on the arrays; and 2) an implanted electronic package that is small and flexible allowing placement of the device in locations that would be surgical difficult and poorly tolerant of rigid IPGs. The Phase I objective is to demonstrate the fabrication and functioning of non-hermetically encapsulated multielectrode arrays employing a 16-channel ASIC stimulator. These arrays and ASICs would be subjected to accelerated in vitro testing to establish the durability of the devices and to provide confidence in the long-term stability of the arrays for chronic animal testing in Phase II. The Phase I Aims are as follows: Aim 1. To develop and test non-hermetic encapsulation based on surface functionalized inorganic coatings and silicone encapsulants; Aim 2. To demonstrate the encapsulation of a 16-channel stimulation ASIC on a polyimide array and to conduct stimulation pulse testing and accelerated in vitro testing of the assembly. The program is a collaboration between EIC Laboratories (Norwood, MA) and Sigenics Inc. (Chicago, Ill). In Phase I, EIC will conduct the array fabrication and testing while Sigenics Inc. will provide ASICs, wire bonding, and expertise in testing polymer-based encapsulation. PUBLIC HEALTH RELEVANCE: The development of flexible polymer encapsulated multielectrode arrays and implanted electronics will allow the development of neural prostheses with a significantly greater number of electrodes than is possible with present technology. The small size of the electronic package resulting from replacement of titanium cans with polymer encapsulation will allow surgical placement of devices at sites in the body that would not be otherwise possible with conventional devices. These arrays will benefit patients with spinal cord injury, stroke, blindness and other diseases or disorders requiring electrical stimulation for treatment.