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Proceedings Paper

Biochemical microsystems with integrated photodiode arrays of improved sensitivity and functionality
Author(s): Otto Leistiko; Peter Friis
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Paper Abstract

In order to determine the maximum efficiency obtainable for the Mesa photodiodes used in our integrated bio/chemical microsystems, devices of different geometry have been integrated with optical waveguides and a simple microfluidic system in a test chip. Also, in order to study the effect of increasing the interaction length between the chemicals in the microchannel and the measuring light beam, a second integrated system was designed and fabricated. Two different geometries were studied, one in which the light is transmitted through the liquid in a direction perpendicular to the axis of a microchannel 50 micrometer wide and another in which the light is transmitted along the axis of a microchannel 5 mm long. The latter geometry was used in order to increase the interaction length between the light and the liquid by a factor of 100, thus, increasing the detection sensitivity by approximately 20 dB. The systems were fabricated employing two substrates which were bonded together, a silicon wafer containing the optical circuitry, plus one half of the microchannel circuitry, and a Pyrex wafer containing the other half of the microchannel circuitry. The planar multimode waveguides which formed the optical circuits were low loss ((alpha) less than or equal to 0.5 dB/cm) germanosilicate glass structures while the photodetectors were special, 'end-fire,' coupled Mesa structures having a good sensitivity (maximum R approximately equals 0.5 A/W) and broad spectral response ((lambda) approximately equals 350 - 1000 nm). In order to make more realistic studies of the detection sensitivity, simple chemical analyses such as phosphate determinations were performed using the chips made.

Paper Details

Date Published: 3 June 1999
PDF: 10 pages
Proc. SPIE 3606, Micro- and Nanofabricated Structures and Devices for Biomedical Environmental Applications II, (3 June 1999); doi: 10.1117/12.350055
Show Author Affiliations
Otto Leistiko, Technical Univ. of Denmark (Denmark)
Peter Friis, Technical Univ. of Denmark (Denmark)

Published in SPIE Proceedings Vol. 3606:
Micro- and Nanofabricated Structures and Devices for Biomedical Environmental Applications II
Mauro Ferrari, Editor(s)

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