OLETs rely on three layers of material, with the bottom layers carrying a charge, the middle layer (the meat in this high-tech sandwich) emitting photons when excited by the bottom, and the top layer selectively letting those photos through.
Nobody made buffalo-hide shoes, and there was a ready supply of raw material: Ranchers slaughtered about 14, 000 bison each year to meet the growing demand for low-cholesterol meat.