A Fully Wireless Implantable Multi-Channel Muscle Stimulator with Closed-Loop Feedback Control

We have developed an implantable four-channel high-current biphasic stimulator device for controlling the muscles of the hand, and successfully tested it in a non-human primate (NHP). The charge-balanced stimulator features an external unit which connects to a personal computer via WiFi, and provides wireless power and data control commands to the implant across biological tissue. The stimulator obtained realtime grip force from the hand using a force sensor to perform automated closed-loop control of the stimulation amplitude to ensure that we were able to produce sustained gripping force in the hand of the animal in the event of muscle fatigue. The device was encapsulated using a FDA-compliant biocompatible polymer for reliable long-term study. In-vivo experiments performed after the stimulator (with electrodes embedded in different muscles) had been implanted for one month demonstrated that the system was able to evoke, and automatically maintain, a targeted range of gripping force in the animal's hand. Our results demonstrate the utility of our closed-loop muscle stimulator as a neuroprosthesis for restoring functional hand movements in patients with upper-limb peripheral nerve injuries.