Nobody likes getting their shots, but whether childhood immunization, annual flu vaccination or whatever else, we're required to undergo the uncomfortable sensation of needle piercing skin multiple times throughout our lives. However, a new laser-based system promises to take the “ouch” out of injections by delivering shots as painlessly as being struck by a puff of air.
The system uses an adapted erbium-doped yttrium aluminum garnet (Er:YAG) laser, which is often implemented in facial treatments and the removal of warts. The Er:YAG laser is combined with a small adapter which houses the drug to be delivered, in liquid form, in addition to a chamber containing water, which acts as a “driving fluid."
The two liquids are kept apart by a flexible membrane and, as the Er:YAG laser is operated, each laser pulse (lasting just 250 millionths of a second) generates a vapor bubble inside the driving fluid. This bubble in the water produces enough pressure to put an elastic strain on the membrane, causing the liquid drug to be pushed out of a miniature nozzle in a narrow jet measuring 150 micrometers (millionths of a meter) in diameter – or slightly larger than the width of a human hair, with just the right amount of force to break the skin.
A time-lapse image showing a microjet fired through the air from the laser-based injection system, traveling at a velocity of 30 meters (98.5 feet) per second (Image: Optics Letters)
“The impacting jet pressure is higher than the skin tensile strength and thus causes the jet to smoothly penetrate into the targeted depth underneath the skin, without any splashback of the drug,” explains Jack Yoh, professor of mechanical and aerospace engineering at Seoul National University in South Korea, who developed the device along with his graduate students.
Yoh further details that while tests on guinea pig's skin show the drug-laden jet to be capable of penetrating several millimeters beneath the skin’s surface with no damage to the tissue and little or no pain, the ideal target for injection is the more accessible epidermal layer, which is located much closer to the skin surface and contains no nerve endings, thus allowing a pain-free shot.
Though alternative methods of injection have been available for some time, Yoh says that his method differs from these by not relying on a mechanically driven, "piston-like" device to force drugs into the skin, but rather utilizing the fine control that only a laser-based system can currently offer.
Yoh is presently collaborating with a company in order to produce low-cost, replaceable Er:YAG injectors for clinical use, and he states that we could soon see the technology adopted in situations where small doses of drugs are to be injected at multiple sites.
Profesor Yoh and his Seoul National University-based team describe their laser-based injector system in the Optical Society’s (OSA) journal Optics Letters.