A cochlear implant is an electronic device that helps restore or re-establish hearing in deaf people by stimulating the auditory nerve with electrodes. Cochlear implants are now routinely used by medical institutions in various countries as a treatment for severe to total deafness, and the number of patients wearing cochlear implants has reached 100,000 worldwide. However, existing cochlear implant systems require a disc-shaped transmitter about 1 inch (about 2.5 cm) in diameter to be fixed to the skull and connected by wires to a microphone, power supply and other devices, looking like an oversized hearing aid and causing some degree of inconvenience to the user. Developed by scientists at MIT’s Microsystems Laboratory (MTL) and doctors at Harvard Medical School and the Massachusetts Eye and Ear Infirmary, this cochlear implant eliminates the need for such uncomfortable external hardware by using a new, low-power signal processing chip. The middle ear has three wonderful bones that are called auditory tuberosities, which are the smallest bones in the body, three in each of the left and right ears. They transmit vibrations from the tympanic membrane to the cochlea, causing cilia cells in the cochlea to generate nerve impulses, which then form hearing in the auditory centers of the cerebral cortex, allowing us to hear sounds. Deaf people often have problems in these areas, resulting in hearing loss. New cochlear implants include a small sensor that detects vibrations in the auditory tuberosity. When the sensor detects vibrations, the signal is sent to a microchip implanted in the ear, which converts the sound signal into an electrical signal and transmits it to an array of electrodes in the cochlea to re-establish hearing. Existing cochlear implants use an external microphone to collect sound, but the new implant will instead use the user’s own ear canal and middle ear, an almost unprecedented attempt in cochlear implant devices. Because of the fully built-in approach, reducing power consumption is critical to the success of such cochlear implants. To do this, the researchers used several technologies already developed at the MIT Microsystems Laboratory, such as custom low-power filters and amplifiers, devices that can accurately process and restore sound signals at very low power consumption. In addition, they have developed a new signal circuit that can reduce the energy consumption of the chip by 20 to 30 percent. For ease of use, the implantable cochlear implant will be wirelessly rechargeable and can operate continuously for eight hours on a full charge. The paper’s lead author, Marcus Yeh, PhD, of the Massachusetts Institute of Technology, and graduate students Ruijin and Nathan Ickes of the School of Electrical Engineering and Computer Science, also showed a prototype charger that can be combined with a regular cell phone to charge the new cochlear implant. In addition, the researchers plan to create a smart pillow to charge the cochlear implant while sleeping.