The myoneural actuator is a fatigue-resistant, implantable biohybrid actuator built from living skeletal muscle, engineered through a regenerative surgical approach to replace conventional mechanical actuators in implantable systems.
The MNA is constructed by denervating a native muscle's motor nerve and reinnervating it with a sensory nerve. This redirects control from the central nervous system to a computer-controlled framework via functional electrical stimulation (FES), while preserving the muscle's self-sustainability. A key discovery underlying the MNA is that sensory axons can form cholinergic synapses with skeletal muscle fibers — establishing functional neuromuscular junctions and enabling precise, electrically evoked contractions through a natural neural pathway.
Because sensory nerves have a more uniform axon diameter distribution compared to motor nerves, the MNA avoids the preferential large-fiber recruitment that typically accelerates fatigue under FES. The result is a 260% improvement in fatigue resistance over native muscle under continuous stimulation, with fundamentally different force dynamics. Extended closed-loop force control is demonstrated across a range of target levels, maintaining controllability where native muscles rapidly fail. Reversible electrical nerve block is integrated to neurally isolate the MNA from the CNS during operation, preventing unintended afferent signaling.
To illustrate its translational potential, two biohybrid system applications are demonstrated: a Proprioceptive Mechanoneural Interface (PMI) for bidirectional neuroprosthetic control, enabling both efferent prosthetic command and modulation of proprioceptive afferents, and a biohybrid organ system that wraps the MNA around the small intestine to mechanically modulate its contractions on demand.
The MNA is based on widely practiced reconstructive surgical techniques and standard nerve cuff electrodes, positioning it for near-term clinical translation in applications spanning limb loss, organ failure, and neural feedback for bionic systems.