Intense switchable fluorescence in light wave coupled electrowetting devices

Switchable fluorescence has been obtained from light wave coupled (LWC) electrowetting (EW) devices fabricated on an optical waveguide substrate. The LWC device structure contains a polar water component and a nonpolar oil component that compete for placement on a hydrophobic surface under the influence of an applied electric field. The oil film contains organic lumophores that fluoresce intense red (608nm), green (503nm), and blue (433nm) light with ∼90% quantum efficiency when excited by violet light. Violet InGaN light-emitting diodes (LEDs) couple ∼405nm excitation light into the waveguide substrate. EW of the water layer displaces the fluorescent oil film such that it is either optically coupled to, or decoupled from, the underlying waveguide. The output luminance can be modulated from >100cd∕m2to<5cd∕m2 as a dc voltage ranging from 0to−24V is applied to the water layer. Maximum luminance of 15×30 arrays of the devices may exceed ∼500cd∕m2 by simply increasing the output of the InGaN LEDs.