The last 20 years have seen two trends that will make the development of new interfaces between man-made devices and the living brain increasingly important. Advances in computational power and robotics have made the practical use of such interfaces possible. The aging of the populations of developing nations will make such interfaces a necessity. The use of electrodes for both recording from and stimulating elements within the nervous system is becoming increasingly important for basic research as well as clinical applications. This is a proposal for the development of an electrode technology that is based on the use of Chemical Deposited Vapor (CVD) diamond film as both an electrode substrate and coating. What is known of the tissue compatibility of diamond film suggests that it is totally inert in physiological environments, and its mechanical strength and reliability is well documented. It is also free of artifact when using MRI imaging. Our fabrication laboratory supports selective ion-implantation of these films in order to make them electrically conductive where necessary. We will design and fabricate both single electrodes with full diamond coating on a tungsten core and multiple electrode arrays with eight sensitive regions, each consisting of an array of 16 microtips. We will test the physical and electrical characteristics of these electrodes in saline and in a typical recording/stimulation scenario involving insertion into cat primary visual cortex. Electrode parameters to be varied include tip size and configuration, doping level and surface texture. To test long-term stability of the material and tissue compatibility, we will implant two of the array electrodes in Bush Baby visual cortex for six months. Performance characteristics will be tested at regular intervals and at explanation time both tissue and electrodes will be examined for any deterioration. Our ultimate goal is to take advantage of this technology for both designs of hitherto impossible configurations (e.g., a fully three dimensional array) as well as development of reliable and safe electrodes suitable for long-term implantation. ? ?
