A team of three engineering students from Rice University, Houston, United States, created the device to ease the pain of an injection. A new drug injector called "Comfortably Numb" is a cooling device. It numbs the skin prior to getting a shot. It works like an ice pack, which produces a rapid chemical reaction that cools and numbs patients' skin in seconds. The device consists of a small 3D-printed cylinder with a metal plate at one end. It contain ammonium nitrate and water in separate compartments.

