Various groups have attempted this using compressed air and various kinds of liquid pumps but none have been particularly successful. One problem is that liquid jets can be just as painful as needles and even more damaging to the skin and tissue below.  But the most serious problem is splashing. In all of the techniques tried so far, some of the liquid splashes off the skin or doesn’t penetrate deeply enough and this makes it impossible to know what dose the patient has received. That’s a serious problem for any condition that requires a precise volume of drug  – and that’s pretty much all of them. This looks set to change. Today, Yoshiyuki Tagawa at the University of Twente in The Netherlands and a few pals say they’ve solved this problem thanks to a new technique for focusing a stream of liquid into a microjet travelling at up to 2000 miles per hour (850 m/s). Yep–that’s 2000 mph about the same speed as a supersonic Blackbird SR-71.

Needle-Free Injections Perfected Using Supersonic Liquid Microjets | MIT Technology Review Saturday, February 15, 2014 @ 4:04pm