Particles that switch color under ultraviolet light, and remember.
Each particle holds a photochromic dye that flips between two stable forms. Ultraviolet light writes one state; visible light erases it. Nothing moves and nothing is consumed. The molecule simply reshapes and stays reshaped.
Implanted in the dermis by the million, they are what makes a tattoo able to sense.
Carson J. Bruns, Associate Professor, ATLAS Institute and the Paul M. Rady Department of Mechanical Engineering, University of Colorado Boulder.
Carson J. Bruns