Researchers around the globe are working to engineer a pain-free method to deliver vaccines and other medications subcutaneously without the use of a hypodermic needle. Some have created patches comprised of microneedles, others have designed a needle modeled after the mosquito’s mouth and another group devised a magnetic jet injection device.
Now researchers in South Korea have developed a device using an erbium-doped yttrium aluminum garnet (Er:YAG) laser to propel a tiny, precise stream of medicine below the skin's surface. A paper describing researchers' work was published yesterday in Optics Letters. According to journal release:
The laser is combined with a small adaptor that contains the drug to be delivered, in liquid form, plus a chamber containing water that acts as a “driving” fluid. A flexible membrane separates these two liquids. Each laser pulse, which lasts just 250 millionths of a second, generates a vapor bubble inside the driving fluid. The pressure of that bubble puts elastic strain on the membrane, causing the drug to be forcefully ejected from a miniature nozzle in a narrow jet a mere 150 millionths of a meter (micrometers) in diameter, just a little larger than the width of a human hair.
Tests on guinea pig skin show that the drug-laden jet can penetrate up to several millimeters beneath the skin surface, with no damage to the tissue. Because of the narrowness and quickness of the jet, it should cause little or no pain, [ Seoul National University Jack Yoh] says. “However, our aim is the epidermal layer,” which is located closer to the skin surface, at a depth of only about 500 micrometers. This region of the skin has no nerve endings, so the method “will be completely pain-free,” he says.
This short video shows a demonstration of the injector firing into the open air without a skin or gel target. The jet, which is roughly the diameter of a human hair, seems dispersed but a target would be placed within the jet breakup distance of a few millimeters, so splash-free injection is achieved.