We report a high-sensitivity, disposable lab-on-a-chip with a thin-film organic light-emitting diode (OLED) excitation source and an organic photodiode (OPD) detector for on-chip fluorescence analysis. A NPB/Alq3 thin-film green OLED with an active area of 0.1 cm(2) was used as the excitation source, while a CuPC/C(60) thin-film OPD with 0.6 cm(2) active area was used as a photodetector. A novel cost-effective, cross-polarization scheme was used to filter out excitation light from a fluorescent dye emission spectrum. The excitation light from the OLED was linearly polarized and used to illuminate a microfluidic device containing a 1 microL volume of dye dissolved in ethanol. The detector was shielded by a second polarizer, oriented orthogonally to the excitation light, thus reducing the photocurrent due to excitation light leakage on the detector by approximately 25 dB. The fluorescence emission light, which is randomly polarized, is only attenuated by approximately 3 dB. Fluorescence signals from Rhodamine 6G (peak emission wavelength of 570 nm) and fluorescein (peak emission wavelength of 494 nm) dyes were measured in a dilution series in the microfluidic device with emission signals detected by the OPD. A limit-of-detection of 100 nM was demonstrated for Rhodamine 6G, and 10 microM for fluorescein. This suggests that an integrated microfluidic device, with an organic photodiode and LED excitation source and integrated polarizers, can be fabricated to realize a compact and economical lab-on-a-chip for point-of-care fluorescence assays.

In this work, we present a simple method for establishing re-usable quick-release compression-based fluidic connections for characterization of microfluidic systems. Our interconnect scheme uses O-rings to form a compression seal against the upper surface of the microfluidic device and around the inlet/outlet tubing, thus establishing connections to the macroworld and preventing any leaks at the ports. With this approach, fabrication is inexpensive and easy, not requiring time-consuming or specialized fabrication procedures. The connections to the real world can be established and removed numerous times without damaging the microfluidic device, and since the approach is adhesive-free there is no danger of microchannel blockage. The demonstrated interconnect is also flexible enough to permit tube bending parallel to the device and makes it possible to place input ports close together to minimize dimensions of complex microfluidic systems. In leakage tests, the interconnect was measured to withstand pressures up to 1.7 MPa, which is enough for most microfluidic applications, and probably nanofluidic applications. This interconnect makes connecting inlets and outlets faster and easier, saving hours of processing time. It can be quickly and easily reconfigured to match device port positions, and is compatible with microfluidic systems fabricated in polymer, plastic, glass or silicon. Further, the flexible nature of the developed compression-based interconnect, both with regard to tubing flexibility and the ability to re-use numerous times, makes it ideal for rapid prototyping of research systems and potentially for quality control in large-scale production.

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