"Tattoo paper" refers to a special type of paper used to create temporary tattoos. It allows you to print or draw a design, apply it to your skin using water, and have a temporary tattoo that lasts for a few days. Full definition
The sensor, which acts as the anode for the biobattery, is imprinted onto temporary tattoo paper with the cathode, according to a paper in Angewandte Chemie. (sciencemag.org)
Print your photos on tattoo paper: I used photoshop and used the quick selection tool to abstract the face of my kiddos out of the photo. (littleinspiration.com)