Hermetic Nanowire Interconnects for Neural Prostheses

DESCRIPTION (provided by applicant): Implantable microelectronic devices are becoming increasingly accepted as treatment options for a variety of disorders including: deafness, movement disorders, and urinary incontinence. These devices consist of microelectronic components housed inside of a biocompatible protective package. Electrical conductors called interconnects, penetrate through the package to allow stimulation and recording of neurons. Present-day devices like the cochlear implant have 22 interconnects. In contrast, visual and cortical prostheses under development may require hundreds of electrodes, each with its own interconnect, to meet the needs of patients. State of the art implantable electronic interconnects cannot meet these requirements. Advancement of interconnect technology for implantable microelectronics is limited by the availability of suitable fabrication processes. We propose to develop a hermetic, biocompatible microelectronics package that incorporates an interconnect substrate based on arrays of electrodeposited platinum nanowires embedded in nanoporous aluminum oxide. Our preliminary results suggest that the nanowire interconnect array (NIA) is hermetic. This hermeticity is a unique property and direct result of restricting the deposition to nanometer length scales. In contrast, electrodeposition does not fill micron scale pores completely. Thus, this nanotechnology is a novel method for interfacing electronics with neural tissue. The research plan places primary focus on the two most challenging aspects of the technology: 1) robust and repeatable NIA fabrication and 2) joining the NIA to a hermetic package. In addition to these two activities, initial system test and biocompatibility assessments will be performed. Helium leak testing will be used to assess hermeticity. Standard brazing methods will be used to join the NIA to a hermetic package. Accelerated soak testing will be used to predict package lifetime. Initial biocompatibility studies will be done using standard and custom tests. Neurological disorders pose difficult medical problems, since damaged neurons do not heal well if at all. Neurosensory diseases of the eye, like age-related macular degeneration (AMD) and retinitis pigmentosa (RP), are leading causes of retinal blindness. RP has an incidence of 1/4000 live births and AMD blinds 200,000 eyes each year. Paralysis afflicts 100,000s each year through stroke or spinal cord injury, among other causes. Disorders such as Parkinson's disease, essential tremor, epilepsy, and chronic pain are other neurological diseases that have a significant and negative impact on public health. Neural prostheses have the potential to treat these disorders through electrical stimulation of nerves. The proposed research plan would advance a key technology in support of future neural prosthetic systems.