Synthetic muscles can restore the ability of patients with facial paralysis to blink, potentially benefiting thousands who can't shut their eyelids due to stroke, nerve injury or facial surgery.
The technique, which uses a combination of electrode leads and silicon polymers, could be used to develop synthetic muscles to control other parts of the body.
“This is the first-wave use of artificial muscle in any biological system,” said Travis Tollefson, facial plastic surgeon at the University of California-Davis Medical Centre (UCDMC) Otolaryngology department.
Tollefson and colleagues were seeking to develop the protocol and device design for human implantation of electroactive polymer artificial muscle (EPAM) to create a long-lasting eyelid blink that will protect the eye and improve facial appearance.
EPAM is an emerging technology that has the potential for use in rehabilitating facial movement in patients with paralysis. Electroactive polymers act like human muscles by expanding and contracting, based on variable voltage input levels.
For people with other types of paralysis, the use of artificial muscles could someday mean regaining the ability to smile or control the bladder.
Re-animating faces is a natural first step in developing synthetic muscles to control other parts of the body, said UCDMC otolaryngologist Craig Senders.
“Facial muscles require relatively low forces, much less than required to move the fingers or flex an arm,” said Senders.
Blinking is an essential part of maintaining a healthy eye. The lid wipes the surface of the eye clean and spreads tears across the cornea.
Without this lubrication, the eye is soon at risk of developing corneal ulcers that eventually can cause blindness.
Eyelid paralysis currently is treated by one of two approaches. One is to transfer a muscle from the leg into face. However, this option requires six to 10 hours of surgery, creates a second wound, and is not always suitable for elderly or medically fragile patients.
The other treatment involves suturing a small gold weight inside the eyelid. The weight closes the eye with the help of gravity. Though successful in more than 90 percent of patients, the resulting eye blink is slower than normal and cannot be synchronized with the opposite eye, said a UCDMC release.
These findings appear in the January-February issue of the Archives of Facial Plastic Surgery.