Some people just really hate needles, even if they are for delivering an important medicine into your blood stream. This hate may be caused by the pain of the needle breaking the skin or just the appearance of the long, thin metal cylinder. The shots are important though, so many researchers are working to develop painless injection systems, and one from Seoul National University, as reported in the Optical Society of America's Optics Letters journal, uses a laser to push the medicine into your skin.
The main components of the injector are the laser, the liquid drug, water, and a flexible membrane between the medicine and the water. To inject the medicine the laser pulses for a quarter of a second, which is long enough to vaporize some of the water and create an air bubble. This bubble puts enough pressure on the membrane so quickly, that the medicine on the other side gets pushed through a nozzle fast enough to penetrate the skin. At only 150 micrometers wide, the spray from the nozzle should not be noticeable to a patient, and as the researchers were targeting a later of the skin with no nerve endings, there should be no pain at all.
This is not the first painless injector developed, as the researchers point out, but those before it use a mechanical system to drive the medicine through the nozzle. This makes the system somewhat more complex and may not offer the precision a laser can offer. The researchers are now working with a company to create a product for clinical use.