No more needles: Painless laser injection could make jabs a thing of the past



South Korea team creates laser that uses 'just the right amount of force' to inject medicine



Future jabs could be as painful as 'a puff of fresh air'

Medical history: The research in Seoul could make the jab a thing of a past

Some people hate them, some people fear them, and the rest of us probably don't enjoy them that much.

But needle injections could finally become medical history, after scientists found a way to use lasers to take the 'ouch!' out of a medicine jab.

The process, developed at Seoul National University in South Korea, could revolutionise how we receive annual flu shots, childhood immunisations, and other treatments that involve piercing the skin with a needle.

The laser-based system blasts microscopic jets of drugs directly into the skin, and the creators say it is as gentle and painless as 'being hit with a puff of air'.

The system uses an 'yttrium aluminum garnet' 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.

Now Jack Yoh, a professor of mechanical and aerospace engineering, has combined the laser 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.

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 between the water and drug, causing the drug to be forcefully ejected from a miniature nozzle in a narrow jet.

The jet is a mere 150 millionths of a meter (micrometers) in diameter, just a little larger than the width of a human hair.

The beam entrance view of the laser injector: The technology could end the jab forever

Yoh said: '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.'



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, Yoh said - 'However, our aim is the epidermal layer,' which is located closer to the skin surface, at a depth of only about 500 micrometers.

Tested in gel: The laser creates a hole in the gel (the black line) before the drug is injected

This region of the skin has no nerve endings, so the method 'will be completely pain-free'.



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 said.

'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.

'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.



