There are three main problems with needles.
One of them is 'needlestick injuries' where doctors and nurses stick themselves - often leading to sickness and even death. Problem two is that they can't delivery very precise doses. And the third problem is just that needles hurt. The fear of needles causes people, in some cases even fully-grown authors, to avoid treatment.
Plenty of people have tried to solve these problems before, but until now inventions to deliver drugs without a needle have been noisy, often painful machines involving springs, compressed gases or explosive chemicals that don't allow precision in how much is injected or how deep a dose is delivered.
Hunter's device shoots a jet of liquid into the skin.