Heterogeneous Integration of a LASER Induced Fluorescence Detection Device for Point-of-Care Microfluidic Biochemical Analysis

ABSTRACTFluorescence detection is more advantageous than electrochemical detection in terms of high sensitivity, multiplexed detection capability and isolation from analyte. Integration of fluorescence detection, however, is much more difficult. First, it would require heterogeneous integration of various optical components including an excitation source, an optical filter, a lens, a mirror and a detector. Second, most of integrated fluorescence detectors, even though not fully integrated, suffer from high limit of detection (LOD) compared to conventional optical system that consists of discrete optical components. We have reduced laser light scattering in an integrated hydrogenated amorphous Si (a-Si:H) fluorescence detector, significantly improving a limit-of-detection (LOD). The detection platform comprises a microlens and the annular fluorescence detector where a thick SiO2/Ta2O5 multilayer optical interference filter is monolithically integrated on an a-Si:H pin photodiode. With a microfluidic capillary electrophoresis (CE) device mounted on the platform, the integrated system is demonstrated to separate DNA restriction fragment digests with high speed, high sensitivity and high separation efficiency, implying single molecular DNA detection when combined with polymerase chain reaction (PCR). We are now working towards integration of an excitation source to fabricate heterogeneously integrated laser-induced fluorescence detection (LIF) device that would be comprised of an InGaN laser diode, microlenses and the integrated a-Si:H fluorescence detector.