Problem:
People with diabetes must monitor their blood sugar and inject themselves with insulin several times a day. Even those with insulin pumps risk complications from injecting too much or too little insulin.

Solution:
Zhen Gu, a researcher at the University of North Carolina and North Carolina State University whose grandmother died from diabetes complications, is developing insulin delivery mechanisms that could be better. The most recent one is a fingernail-size patch covered in more than 100 microneedles. When you put the patch on your skin, you feel momentary pinpricks as the needles poke into your blood vessels. The needles are full of tiny sacs containing insulin and an enzyme. The sac is just permeable enough to allow glucose inside, where the enzyme converts it to an acid that—when blood sugar is too high—makes the sac open and release the insulin. The sacs fall apart at different rates, so the insulin is released over hours rather than in one burst.

When Gu tested the patch on five mice, it controlled their blood sugar for nine hours, although it takes half an hour to work, and people without diabetes naturally regulate their blood sugar much faster than that. Now he has begun testing the patch on pigs, whose thin skin is more similar to humans’. Eventually, Gu hopes, people with diabetes could slap on a patch every two or three days to reliably and precisely control blood sugar without much pain or effort.

—Anna Nowogrodzki

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