Microswitches: Closing the gap between the two reflective surfaces, using micro-electromechanical systems (MEMS) devices, causes constructive interference of reflected light only in the ultraviolet band of wavelengths. As a result, no visible light is reflected, so the cells in this “off” state appear black. When a voltage is briefly applied, the MEMS device collapses again, opening the gap and causing blue wavelengths to be amplified when reflected, and causing this particular cell to appear blue.