A nicotine patch? Got that. A birth control patch? Got that, too. But an insulin patch? Such an invention may soon be on its way, thanks to biomaterials design experts at the University of North Carolina and North Carolina State University. Scientists there have engineered a penny-sized patch that delivers insulin in response to changes in blood sugar levels. This “smart” patch, covered in nearly 100 needles the size of human eyelashes, could one day serve as a blood glucose monitor and at the same time replace insulin injections for diabetics—a painful ritual that some patients have to go through several times a day. The patch, which feels like a mosquito bite when applied, has already proved effective in mouse models with type 1 diabetes for up to 9 hours, scientists report online before print in the Proceedings of the National Academy of Sciences. More work will need to take place before the patch is ready for human use. But trials are in the works, and researchers expect to have an insulin patch on the market within 2 to 3 years.