Abstract
Medical tattoos provide medical information, guide radiotherapy, and improve cosmetic outcomes of medical interventions. These tattoos are administered by repeated needle injection that causes pain, bleeding, and risk of infection, which limit more widespread use. Here, we developed single-use microneedle (MN) patches to deposit tattoos in the skin in a simple, rapid, painless, and bloodless way without biohazardous sharps waste. MN patch tattoos were designed with numbers, letters, symbols, environmentally responsive inks, and QR codes. Colored tattoos, and tattoos only visible with ultraviolet illumination for increased privacy, were developed and retained in the skin for at least one year. These MN patch tattoos recorded medical conditions such as diabetic medical alerts and vaccination status, responded to biophysical cues for possible physiological monitoring, and encoded complex personal health information. MN patches may increase safety and access to medical tattoos for improved fiducial marking, medical information storage, physiological monitoring, and cosmetic outcomes.