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We have fabricated a novel microfluidic chip based on fiber sensor with casting PDMS method. The optical fiber is used
to transmit excitation light, so the diameter of the excitation beam is decreased to 93μm. In order to improve the coupling
efficiency of the excitation light in the fiber, the optical fiber collimation device is used to couple beam. The microfluidic
chip consists of multimode optical fiber, PDMS cover slab and PDMS base slab. The mould of cover slab is made
through twice exposal, however the base slab is achieved using once exposal only. The depths of microfluidic channel
and optical fiber channel in the PDMS cover slab are 50μm and 90μm, respectively, and the optical fiber channel in the
PDMS base slab is only 40μm. This design can make the centers of the microfluidic channel and the fiber channel in the
same point, so the microfluidic channel and the optical fiber can be aimed at easily. In addition, the size of microfluidic
channel depth is near the size of light spot of optical fiber, so the detection sensitivity is improved without using the
optical focusing system. The detection system of the microfluidic chip is manufactured and it composed of high voltage
modules, darkroom, LED light source, photomultiplier and data acquisition circuit, moreover, the software of the
detection system is developed. The high voltage modules with four 2kV are used to control the sample amount in the
separation channel, so the sensitivity is improved. The microfluidic chip is placed in the darkroom to avoid the
interference of external light. The high brightness blue light emitting diode (LED) is used as excitation light sources for
inducing fluorescence detection through coupling the LED light into the optical fiber. The photomultiplier is used to
amplify the fluorescence signals and the function of data acquisition circuit is data collection and data processing. Under
the control of software, the experiment process can be implemented easily. As an application, the microfluidic chip is
tested on the detection system for the separation experiment of FITC fluorescein and FITC-labeled amino acid. The
experiments justify the feasibility of the chip.
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