Characterization of a Micro Capillary Zone Electrophoresis System With Integrated Amorphous Silicon Based Optical Detect
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1004-P03-20
Characterization of a Micro Capillary Zone Electrophoresis System With Integrated Amorphous Silicon Based Optical Detectors Lars Schˆler1, Konstantin Seibel1, Heiko Sch‰fer1, RenÈ Johannes P¸schl2, Bernd Wenclawiak2, and Markus Bˆhm1 1 Institute for Microsystem Technologies, University of Siegen, Hˆlderlinstr. 3, Siegen, Germany 2 Analytical Chemistry, University of Siegen, Adolf Reichwein Str. 2-4, Siegen, Germany
ABSTRACT Application specific Lab-on-Microchips (ALMs) making use of the combination of complex microfluidic networks with microelectronic circuits and micro optical components allow the realization of miniaturized application specific biological and chemical processing and analysis devices. Fluorescence sensing is one of the most widely used detection technologies, e.g. for DNA fluorescence labelling in Micro Capillary Electrophoresis (µCE) due to its superior sensitivity and specificity. Unfortunately, commercially available fluorescence sensing systems are physically very large, non portable, expensive and constrain the analysis in portable diagnostic and medical care. Integrated semiconductor optoelectronic devices can provide a portable, parallel and inexpensive solution for on chip fluorescence sensing. Most µCE applications working in the spectral range of visible light. For the integration of optical detection components a photon energy range of 1.6 eV ñ 3.1 eV is of interest. In that spectral range a-Si:H diodes have several advantages compared to crystalline silicon diodes e.g. higher absorption coefficient, higher sensitivity (at 580 nm), lower dark current and higher dark current doubling temperature. In this paper we combine a:Si-H photo sensors with a fluidic micro system to detect the fluorescence of a rhodamine analyte mixture. The analyte mixture was excited by light with a wavelength in the range of λEx = 450 - 490 nm. The a-Si:H detector reveals a low dark current density on the order of 10- 10 A/cm2 and a sufficient dynamic range of ~100 dB under illumination of ~1000 lx as a function of bias voltage. The measurement shows that the movement of the rhodamine plug in the microchannel causes a significant rise in the pin-diode photo current, which correlates to the evaluated signal of a microscope image detector. The photo current difference for excitation and additional fluorescence amounts to 2.4 µA. INTRODUCTION Miniaturized Total Analysis Systems (µTAS) [1] arising from the combination of complex microfluidic networks with microelectronic circuits and micro optical components, are able to realize miniaturized application specific biological and chemical processing and analysis devices, e.g. Wang et al. [2] describes a simple microfluidic system for efficient capillary electrophoretic separation by combining liquid-core waveguide and lock-in amplification techniques and Veledo et al. [3] developed a capillary electrophoresis with laser-induced fluorescence method for free amino acids in human plasma. Monolithic integration of optical sensors by deposition of hydrogenated
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