Three Rice University students have created a great way to relieve the anxiety many of us experience before receiving an injection. The first-year students designed a 3D printed cyclinder which once twisted, combines a water and ammonium nitrate mixture which cools a metal plate. The metal plate is then placed on the site about to receive an injection, numbing it within 60 seconds. More details found here: http://3dprint.com/58636/comfortably...umbing-device/

Below is a picture of the Comfortable Numb 3D printed device: