Researchers have pioneered a new method using optogenetics, which could revolutionize advanced prosthetics and biohybrid robots. This technique, developed at MIT’s K. Lisa Yang Center for Bionics and detailed in Science Robotics, involves using light to stimulate genetically engineered muscle fibers. This innovation aims to enable precise muscle control, potentially benefiting individuals with neurological conditions or paralysis.
Electric signals in FES can cause muscle fatigue
Scientists have traditionally employed electrical stimulation to activate muscles in individuals with motor impairments. Although functional electrical stimulation (FES) has advanced prosthetic limbs and rehabilitation, it has significant limitations. Electrical signals can cause muscle fatigue rapidly and lack the precise control necessary for tasks requiring dexterity, such as grasping objects or playing instruments.
Optogenetics, a cutting-edge field that uses light to control genetically modified cells, involves inserting light-sensitive proteins called opsins into specific neurons, allowing scientists to activate or inhibit these cells with light. While this technique has revolutionized neuroscience, its use in muscle control has been less explored.
The MIT research team, led by Guillermo Herrera-Arcos, proposed that light could more naturally and effectively stimulate muscles through peripheral nerves compared to electrical stimulation. Researchers tested their theory using an advanced light-based stimulation platform designed to target specific nerves with precision. By adjusting the pulse width and frequency of the light signals, they achieved highly accurate, graded control of muscle force.
Optogenetic approach produces gradual and maximum force compared to FES
This optogenetic approach produced higher maximum forces and allowed for a more gradual, step-wise increase in force, unlike the binary activation seen with traditional electrical stimulation. Functional Electrical Stimulation (FES) initially recruits the largest muscle units when electrical signals are applied. This results in a sudden, excessive force after no initial force, as the signal strength increases.
Optogenetics offers more effective muscle control than electrical stimulation due to its alignment with the nervous system’s natural recruitment of motor units. The brain activates smaller motor units first for fine tasks and progressively engages larger ones for greater force. Electrical stimulation, however, triggers the largest units first, causing rapid fatigue and poor force control.
