Laser-powered 'needle' promises pain-free injections

Sep 13, 2012
To test the effectiveness of the drug delivery system, a special gel is used to mimic the behavior of human skin. Here the jet first creates a hole on the surface of the gel, then, at a lower jet pressure, the drug is delivered into the skin. This gel simulation also reveals that there is no “splashback” from the injection, which is an important patient safety factor. Credit: Optics Letters

From annual flu shots to childhood immunizations, needle injections are among the least popular staples of medical care. Though various techniques have been developed in hopes of taking the "ouch" out of injections, hypodermic needles are still the first choice for ease-of-use, precision, and control.

A new laser-based system, however, that blasts microscopic jets of drugs into the skin could soon make getting a shot as painless as being hit with a puff of air.

The system uses an erbium-doped , or Er:YAG, laser to propel a tiny, precise stream of medicine with just the right amount of force. This type of laser is commonly used by dermatologists, "particularly for facial esthetic treatments," says 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 and his team describe the injector in a paper published today in the Optical Society's (OSA) journal .

This shows the beam entrance view of the laser injector. Credit: Image courtesy Jack Yoh/Seoul National University.

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.

"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," Yoh says. Tests on skin show that the drug-laden jet can penetrate up to several millimeters beneath the , with no damage to the tissue. Because of the narrowness and quickness of the jet, it should cause little or no pain, 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 video is not supported by your browser at this time.
The movie shows the injector firing into open air without a skin or gel target. The jet, which is approximately 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. Credit: Video courtesy Jack You/Seoul National University.

In previous studies, the researchers used a laser wavelength that was not well absorbed by the water of the driving liquid, causing the formation of tiny shock waves that dissipated energy and hampered the formation of the vapor bubble. In the new work, Yoh and colleagues use a laser with a wavelength of 2,940 nanometers, which is readily absorbed by water. This allows the formation of a larger and more stable vapor bubble "which then induces higher pressure on the membrane," he explains. "This is ideal for creating the jet and significantly improves skin penetration."

Although other research groups have developed similar injectors, "they are mechanically driven," using piston-like devices to force drugs into the skin, which gives less control over the jet strength and the drug dosage, Yoh says. "The laser-driven microjet injector can precisely control dose and the depth of drug penetration underneath the skin. Control via laser power is the major advancement over other devices, I believe."

Yoh is now working with a company to produce low-cost replaceable injectors for clinical use. "In the immediate future, this technology could be most easily adopted to situations where small doses of drugs are injected at multiple sites," he says. "Further work would be necessary to adopt it for scenarios like mass vaccine injections for children."

Explore further: Researchers build reversible tractor beam that moves objects 100 times farther than other efforts

More information: "Er:YAG laser pulse for small-dose splashback-free microjet transdermal drug delivery," Optics Letters, Vol. 37, Issue 18, pp. 3894-3896 (2012). www.opticsinfobase.org/ol/abst… fm?uri=ol-37-18-3894

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User comments : 4

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roboferret
not rated yet Sep 14, 2012
At last, hypo-sprays!
PPihkala
4 / 5 (1) Sep 14, 2012
I wonder what is the result if this is used repeately at one location.
PeterD
1 / 5 (3) Sep 16, 2012
Since only fools get their children poisoned with vaccines,or take useless flu shots, who cares?
wkrasl
not rated yet Sep 16, 2012
Since only fools get their children poisoned with vaccines,or take useless flu shots, who cares?


I'm just wondering who poisoned your mind?