Manufacture of a next-generation artificial limb system with sensory function that can be driven voluntarily using a neuro-machine interface

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We constructed a prototype of an artificial limb system with which subjects were able to feel somatic sensations exactly as if they were touching the object with their own hands and were also able to move the artificial arm voluntarily exactly as intended using needle EMG information.We used microelectrical stimulation of the sensory nerve fibers in order to evoke somatic sensations in the subjects and we attempted to control the movement of the hand and fingers of the artificial limb system using information of the motor nerve activities recorded from the concerned peripheral nerves. However, the performance of the sieve electrode which we developed was not yet sufficient for steadily recording motor nerve signals, we used needle EMG signals of the concerned muscles instead of motor nerve signals in order to control the movement of the artificial limb system.The experiment for evaluation was performed by a healthy subject in a master-slave format using a robot hand system with the shape of human hand; pressure or vibration stimuli detected by the sensor on the robot hand were transferred to a computer and the frequency of the electrical pulses for stimulating the sensory nerve fiber was determined. These electrical pulses were then output to the concerned sensory nerve fiber via a tungsten microelectrode.Needle EMG information was measured from the concerned muscles using the same tungsten micro-needle electrodes as were used with the sensory system and the grasping power and the positions of the finger joints were determined from the needle EMG information.The results showed that the system worked satisfactorily. Development of nerve electrodes that can measure activity of motor nerve fibers and can stimulate sensory nerve fibers with a sufficient number of channels remains an urgent demand for the creation of a system acceptable for clinical use.