Lab-on-a-chip devices offer faster, cheaper, and better ways of doing chemical and biological analyses. In this paper, we will show that both 3D micro-fluidic and 3D micro-optical structures can be directly formed in photosensitive glass using a femtosecond laser and an annealing and etching process. Particularly, we will demonstrate the fabrication and examine the function of lab-on-a-chip biosensors integrated with micro-optical loops for enhancing detection sensitivity. The fabricated lab-on-a-chip biosensors are composed of a micro-fluidic channel into which sample under test will be injected. Five micro-optical mirrors are distributed on both sides of the micro-channel to form a zigzag optical path, which forces a micro-optical beam to cross the micro-fluidic channel three times before entering into a photodetector. This design can effectively extend the absorption path length and result in enhanced detection sensitivity of photoabsorption spectroscopic analysis. To examine the function of the micro-device, we filled the microfluidic channel with a dye solution (Rhodamine 640 dissolved in methanol) and shone a green laser beam (532nm) from a laser pointer into the microstructure. The fluorescence emission from the dye solution indicated that the light beam passed through the microchannel; however, due to the strong absorption, the output beam was not obvious. Quantitative characterization is under way for evaluating the detection limit of the lab-on-a-chip micro-device.

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