Tunable fluorescence emission from an electrowetting droplet display

Abstract

We report a tunable color display based on the electrowetting actuation of a water droplet doped with 1 mM of rhodamine 6G. The display consists of a Pt wire electrode and a bottom Cu electrode with an insulating silicone layer. Droplet contact angle drops from 90° to 75° over an applied DC voltage range of 0 to 24 V. Variable fluorescence emission induced by applied voltage is demonstrated with the droplet under UV illumination. From an initial value of 574.15 nm (yellow) at 0 V, the fluorescence peak shifts to 555.62 nm (green) at 24 V. Redistribution of the dye molecules in response to an external electric field is a proposed mechanism for the change in fluorescence output.