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 revolutionize how we receive annual flu shots, childhood immunizations, 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 adapter 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.
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.
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