Floating Micro-Stimulators for Neural Prosthetics

DESCRIPTION (provided by applicant): Electrical activation of the peripheral and central nervous system has been investigated for treatment of neural disorders for many decades and a number of devices have already moved into the clinical phase with success. Cochlear prostheses, sacral root stimulation for bladder and bowel control in spinal cord injury, and vagus nerve stimulation in epilepsy are some of the well-known examples of such devices that are being implanted in thousands of patients every year. A major obstacle that has been preventing or otherwise impeding the implementation of many other neural prosthetic devices is the mechanical mismatch of the stimulation electrodes with the neural tissue and the tethering of the wire connections that result in tissue trauma. Electrical stimulators that are remotely controllable with no interconnects and sufficiently small so that a good spatial selectivity is achieved with minimal replacement of the neural tissue are greatly needed. We propose to develop very small (approximately 200 um) photovoltaic elements that can be implanted into the spinal cord or the brain cortex and activated from outside the dura mater through the neural tissue using near infrared laser beams. The geometry and the interface properties of these floating light activated micro electrical stimulators (FLAMES) will be optimized for maximum transfer of energy into the tissue while minimizing the device size. Devices with various sizes will be designed to meet the requirements of different neural stimulation applications. The stimulation properties of the optimized FLAMES will be tested in medium (agar/saline) and in vivo (rat). Future designs will include advanced versions of the FLAMES that are tuned for different wavelengths of light for selective activation. The silicon technology of optical communication has already been developed and studied extensively and can be modified for neural stimulation with reasonable amount of research. Some of the immediate applications include but not limited to visual and auditory cortex stimulation for substitution of these senses, and micro-stimulation of the lumbo-sacral cord for bladder control and locomotion in spinal cord injury.