Artificial Eyelid Muscles Restore the Ability to Blink

A new study demonstrates that artificial muscles can restore the ability of patients with facial paralysis to blink, a development that could benefit those that are no longer are able to close their eyelids due to stroke, nerve injury, or facial surgery.

Researchers from the University of California (UC) Davis Medical Center (UCDMC; USA) developed the new technique, which uses a combination of electrode leads and silicon polymers to form electroactive polymer artificial muscles

(EPAMs) that construct an eyelid sling mechanism that generates an eyelid blink when actuated by the artificial muscle. To test the mechanism, the researchers used cadavers, inserted a sling into muscle fascia or implantable fabric around the eye. Titanium screws secured the eyelid sling to the orbit of the eye. The sling was the attached to a battery-operated EPAM, and both artificial muscle device and battery were placed into the temporal fossa to disguise their presence.

The researchers found that the force and stroke required to close the eyelid with the sling were well within the attainable range of the artificial muscle. This capability may allow the creation of a realistic and functional eyelid blink that is both symmetric and synchronous with the normal, functioning blink. For patients who have one functioning eyelid, a sensor wire threaded over the normal eyelid could detect the natural blink impulse and fire the artificial muscle at the same time. Among patients lacking control of either eyelid, an electronic pacemaker similar to those used to regulate heartbeats could blink the eye at a steady rate, and be deactivated by a magnetic switch. The new procedure is described in an article in the January-February 2010 issue of the Archives of Facial Plastic Surgery.

"The amount of force and movement the artificial muscle generates is very similar to natural muscle,” said codeveloper Travis Tollefson, M.D., a facial plastic surgeon in the UC Davis Department of Otolaryngology – Head and Neck Surgery. "This is the first-wave use of artificial muscle in any biological system, but there are many ideas and concepts where this technology may play a role.”

The three-layered EPAM was developed by engineers at SRI International (Palo Alto, CA, USA) in the 1990's. Inside it is a piece of soft acrylic or silicon layered with carbon grease. When a current is applied, electrostatic attractions causes the outer layers to pull together and compress the soft center. This motion expands the artificial muscle. The muscle contracts when the charge is removed and flattens the shape of the sling, blinking the eye. When the charge is reactivated, the muscle relaxes and the soft center reverts to its original shape.

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UC Davis Medical Center