Prototype device could make getting needles a Comfortably Numb experience

Team Comfortably Numb's skin-numbing device in use (Photo: Rice University)

There are already beverage cans that contain chemically-activated chilling modules. Now, three students from Houston's Rice University are working at applying the same principle to hypodermic needles. Instead of keeping the medication in the syringe cool, however, the idea is that a special needle cap could be used to first chill and numb the patient's skin, making the subsequent injection relatively painless.

Taking its name from the classic Pink Floyd song, team Comfortably Numb consists of computer science major Greg Allison, bioengineering major Andy Zhang and mechanical engineering major Mike Hua.

Their 3D-printed prototype (which isn't yet in needle cap-form) incorporates two sealed compartments, one containing water and one containing ammonium nitrate. As long as the two substances are kept separated, nothing happens.

By twisting the device, however, openings in the compartments get aligned with one another, allowing the water to flow into the ammonium nitrate. The resulting endothermic reaction causes the mixture to cool rapidly, chilling a metal cap on the bottom of the device.

When pressed against the skin, that cap produces a numbing effect within one minute. According to the students, an existing topical patch designed for the same purpose takes approximately an hour to work.

It's estimated that a commercial version of the single-use device could be sold at a price of about US$2 a pop – the team claims that numbing lotions and sprays currently cost more per use. While not every patient would need the device, the students envision it being used on pain-sensitive people such as young children and the elderly, along with patients requiring injections in sensitive parts of the body.

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