Close to half a million people around the world suffer from a serious hearing impairment. In some cases, they can find relief in cochlear and other types of implants. Yet these devices do not help people whose inner ear is damaged or whose auditory nerve does not function properly. For these patients to recover their sense of hearing, electrical signals must be sent directly to the auditory brainstem. The neuroprosthetic used for this purpose is called an auditory brainstem implant (ABI); however, the outcomes of ABIs are mixed and in many cases, patients recover only sound perception. Clinical ABIs are also stiff and cannot conform precisely to the curvature of the auditory brainstem.
Researchers from EPFL, Harvard Medical School, and Massachusetts Eye and Ear developed a soft electronic interface. The highly elastic implant conforms neatly to the curved surface of the auditory brainstem and can send highly targeted electrical signals. It has been produced at a size suitable for human use and in a form that is compatible with current surgical techniques. The new implant consists of a conformable array of platinum electrodes encased in silicone.
Unfortunately, platinum is a rigid metal that cannot be distorted without being damaged. This hurdle was overcome by applying the traditional Japanese paper-cutting technique called kirigami, etching a Y-shaped pattern into metalized plastic segments. The metal was then machined at the micron scale using techniques commonly found in the microfabrication of integrated circuits. The result is a very compliant and highly conductive electrode implant.
The properties of the device would be of value for many types of implantable neuroprosthetics such as those used to stimulate or record neural activity in the spine, brain, or peripheral nerves.