The new silicone patch with star-shaped microneedles, called the ExoPatch, distinguished melanoma from healthy skin in mice.

The patch and test move toward rapid at-home melanoma testing, helping patients catch the most aggressive form of skin cancer early without a biopsy or blood draw.

“The star-shaped needles make puncture easier and less painful, but they are so small that they only go through the top-most layer of the skin, the epidermis, and do not draw blood,” said Sunitha Nagrath, the Dwight F. Benton Professor of Chemical Engineering at U-M and co-corresponding author of the study published in Biosensors and Bioelectronics.

The ExoPatch microneedles, at just 0.6 mm long with a width of less than 100 nanometers (0.0001 mm) at the tip, are coated with a gel that picks up exosomes—tiny packages released by cells—from the interstitial fluid that fills the spaces between cells in the epidermis.