Thin-film polymer light emitting diodes as integrated excitation sources for microscale capillary electrophoresis.

We report the use of a thin-film polymer light emitting diode as an integrated excitation source for microfabricated capillary electrophoresis. The polyfluorene-based diode has a peak emission wavelength of 488 nm, an active area of 40 microm x 1000 microm and a thickness of similar 2 mm. The simple layer-by-layer deposition procedures used to fabricate the polymer component allow facile integration with planar chip-based systems. To demonstrate the efficacy of the approach, the polyfluorene diode is used as an excitation source for the detection of fluorescent dyes separated on-chip by electrophoresis. Using a conventional confocal detection system the integrated pLED is successfully used to detect fluorescein and 5-carboxyfluorescein at concentrations as low as 10(-6) M with a mass detection limit of 50 femtomoles. The drive voltages required to generate sufficient emission from the polymer diode device are as low as 3.7 V.