The core of the unit works essentially like an ice pack, containing ammonium nitrate and water in separate compartments. When the Device is activated, the two ingredients mix and an endothermic reaction Cools down the flat metal tip of the Comfortably Numb. When pressed against the skin, the ice cold tip Cools the injection site and makes it much less susceptible to pain.
As of yet, the Device doesn’t have the actual syringe built in, and that’s the next step for the students. When that’s complete, the needle will be much less visible and should cause less fear in patients than a traditional syringe.
Here is the student team showing off and describing the Comfortably Numb: