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Hate Needles? This 3-D Printed Device Makes Injections Pain-Free

Three college freshmen invent a disposable, 3-D printed device that numbs the skin around an injection site.

No one likes being jabbed with a needle. Some people can’t stand it at all. According to research in the Journal of Family Practice, at least 20% of Americans have needle phobia, and as a result, many skip critical preventive procedures like vaccines and flu shots. That’s a public-health problem.

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But painful injections might soon be a thing of the past. Along with fellow students Andy Zhang and Mike Hua, 19-year-old Rice University computer science undergrad Greg Allison has invented the Comfortably Numb, a new device that makes getting an injection practically painless.

About the diameter of a quarter and less than two inches long, the Comfortably Numb is a small 3-D printed canister that attaches to a hypodermic needle. A small amount of water and ammonium nitrate (the same ingredients found in commercial cold packs) are suspended inside the Comfortably Numb’s canister. Twist the Comfortably Numb, and the seal between these two ingredients breaks, which causes a metal plate at the bottom of the device to rapidly become cold. When attached to a syringe, the device numbs the skin by cooling it to 4.5 degrees Celsius (about 40 degrees Fahrenheit) right before the needle plunges into it.

It’s fast, efficient, and disposable. Even better? Because no chemicals ever touch the body, it’s like a bandaid from the perspective of the F.D.A. It doesn’t have to pass the same sort of regulatory hurdles a needle or other medical devices might face, Allison says.


The Comfortably Numb project came out of Rice’s freshman engineering design class, Engineering 120, the premise of which is to task students with solving the problems of real-world clients. In the case of the Comfortably Numb, the client was Dr. Mehdi Razadi, a cardiothoracic surgeon at the Texas Heart Institute whose day-to-day life involved applying a lot of injections to the face and groin, both of which can be extremely painful. Razadi asked the class to design a device that numbed the skin before injection.


Recognizing the long-term promises of such a device, the Comfortably Numb team figured out a solution after working with advisors and sketching out numerous designs, then used Stratasys and FormLabs 3-D printers to rapidly prototype their design. Since the students didn’t want to jab classmates with needles to test the Comfortably Numb, they instead used a pen pressed into the skin of about half a dozen volunteers to simulate the pain of getting a shot. These are hardly clinical trials, the Comfortably Numb designers say, but they’re confident that their device lowers needle pain at least two points on a 1 to 5 pain scale.


The Comfortably Numb won the Best Freshman Design Award at Rice’s Engineering & Design Showcase, and a provisional patent on the design has been filed. Next up, the team is looking to try to miniaturize the design even further, as well as see if it can be brought to market. “We’re really committed to this idea,” Allison tells me. “In the real world, we see this making injections more comfortable for everyone, especially those who fear them most.”

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One drawback: Cost. Allison and his team reckon that the Comfortably Numb canister could be brought to market for about $2–significantly more expensive than your average needle and syringe, which is, on average, around 35 cents. But for doctors who have to give a lot of injections, the Comfortably Numb team thinks that it’ll be worth the extra cost.

Another issue: It’s being punctured by needles, not the relatively small pinch, that’s the true source of most people’s needle fears, so whether or not the Comfortably Numb can actually cut down on needle phobia rather than just needle pain remains to be seen. Here’s hoping.

You can read more about the Comfortably Numb project here.

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