Donal Bradley

Abstract:

We report efficient polymer photodiodes fabricated on flexible polyethyleneterephthalate (PET) substrates. The PET substrates were coated with a layer of poly(3,4-ethylene-dioxythiophene): polystyrenesulfonate (PEDOT:PSS) that was lithographically patterned to define the anode structure. A blend of poly(3-hexylthiophene) (P3HT) and 1-(3-methoxycarbonyl)-propyl-1-phenyl-(6,6)C61 (PCBM) was then spin-coated from a 1 : 1 mixture by weight of the two components in dichlorobenzene, and the device was completed by vacuum deposition of an aluminium electrode in vacuum. The resulting photodiodes had short-circuit quantum efficiencies of 45% and peak power efficiencies of 3%, which compare favourably with values for similar devices fabricated on rigid indium tin oxide (ITO) coated glass substrates.

Abstract:

We report the fabrication of high quality monolithically integrated optical long-pass filters, for use in disposable diagnostic microchips. The filters were prepared by incorporating dye molecules directly into the microfluidic chip substrate, thereby providing a fully integrated solution that removes the usual need for discrete optical filters. In brief, lysochrome dyes were added to a poly(dimethylsiloxane) (PDMS) monomer prior to moulding of the microchip from a structured SU-8 master. Optimum results were obtained using 1 mm layers of PDMS doped with 1200 microg mL(-1) Sudan II, which resulted in less than 0.01% transmittance below 500 nm (OD 4), >80% above 570 nm, and negligible autofluorescence. These spectral characteristics compare favourably with commercially available Schott-glass long-pass filters, indicating that high quality optical filters can be straightforwardly integrated into the form of PDMS microfluidic chips. The filters were found to be robust in use, showing only slight degradation after extended illumination and negligible dye leaching after prolonged exposure to aqueous solutions. The provision of low cost high quality integrated filters represents a key step towards the development of high-sensitivity disposable microfluidic devices for point-of-care diagnostics.