Electronic implants for the eyes, spinal cord and brain are offering real hope to people who are experiencing the debilitating effects of Parkinson's disease, macular degeneration and a host of other medical conditions. New devices under development by SSIM researchers are designed to reroute brain-to-body connections around disease-ravaged or accident-damaged areas, and therefore at least partially restore muscle movement, vision and other normal functions most people take for granted.
The human central nervous system is an inhospitable environment for electronic devices, because the brain's glial cells attack the foreign material and surround it with a sheath, also called a scar, that interferes with the device function and sometimes physically pushes the implant right out of the brain. The scar can also cause an inflammation in the person's nervous system. An SSIM team of medical scientists and engineers is now developing implants selectively coated with neuroprotective materials that are safe for the body as well as the implant.
One of the major SSIM projects is a sensor implant that tracks pressure inside the skull. High intracranial pressures from such conditions as hydrocephalus, or "water on the brain," can cause brain damage and at times death. Newborns and infants are sometimes born with hydrocephalus, and it is also quite common among those who have suffered a stroke or other head injury. SSIM researchers are working on an implant to monitor the pressure so that physicians can treat high levels, and are also developing a smart shunt that relieves pressure on demand (see below).
For the vision work, they are using wide bandgap semiconductors and excimer-laser micromachining to build a microfluidic prosthesis that delivers targeted chemicals, or neurotransmitters, as needed to the retina. The neural transmitters are caged with an extra molecule that renders them inactive. Ultraviolet light then severs the caging molecule and activates the neural transmitter. The activation, which is spatial in nature, can form a visual picture when the activated neural transmitters interact with the retina. In another project, SSIM researchers are proposing a retinal implant chip placed on the back of the eye and fabricated to generate electrical impulses that send a sight pattern to the brain. There, a second circuit receives those patterns and turns them into a rough image. Through practice, the patient should become adept at translating the images and regaining their vision.
In addition, researchers are working on neurological implants to use precisely conveyed electrical impulses to contract muscle tissue and promote controlled movement in patients with Parkinson's and other neuromuscular diseases.