University of Houston • University of Houston-Clear Lake • ISSO Annual Report Y2002—pp. 110-111

III Nitrides-on-Silicon Chips for Detection of Live Bacteria in Enclosed Space Environments

Abdelhak Bensaoula (UH), David Starikov (UH), Chris Boney (UH), Nasr-Eddine Medelci-Djezzer (UH), Fatima Benkabou (UH), Maia Larios Sanz (UH), and George E. Fox (UH)

RESEARCH ON "III-NITRIDES-ON-SILICON CHIPS FOR DETECTION of Live Bacteria in Enclosed Space Environments" resulted in the development, fabrication, and testing of a new sensor prototype with enhanced capabilities toward advanced space applications. This was a continuation of work begun under an ISSO mini-grant.

The ISSO mini-grant project, completed in spring 2002, resulted in the development of a III-nitride and Si-based compact sensor prototype for measurement of E. coli bacteria populations expressing various fluorescent proteins. The next steps performed in this research were development, fabrication, and testing of a new multi-spectral sensor prototype assembled from optoelectronic components (Fig. 1) sensitive in eight spectral bands covering the near UV and the visible spectrum. Such design has advantages over the previous prototype:

1. simpler design, which does not employ optical filters for wavelength selectivity,
2. capability to measure a larger number of chemical and biological compounds, and
3. besides concentration measurements of a known analyte, identification of unknown analytes.

The filterless design is provided by employment of optoelectronic components performing both optical emission and optical detection functions in a selective range of wavelengths. The comparison with the previous prototype reveals that, for example, the new prototype’s detection limit of fluorescein is at least three orders of magnitude lower (2´10^-9 M vs. 3´10^-6 M) and the dynamic range at least 48 times larger. Unknown analyte detection capabilities were determined using a neural network, indicating an average correct classification rate of 81 percent. Current efforts in this area are being directed toward further miniaturization of the device from a few inches to a few millimeters in size (Fig. 2).

Two UH undergraduate students, N. Withers and V. Ledford, and one graduate student, A. Carreno, participated in this project.

Publications
Stariko v, D., F. Benkabou, N. Medelci, and A. Bensaoula. "Compact Fluorescence Sensors Based on III Nitrides," Proceedings, Annual International Conference of the IEEE Engineering in Medicine and Biology Society and the 2002 Fall Meeting of the Biomedical Engineering Society, Houston, TX, Oct. 23-26, 2002. 284.
Stariko v, D., F. Benkabou, N. Medelci, and A. Bensaoula. "Integrated Multi-Wavelength Fluorescence Sensors," Proceedings, Sicon/02, The Sensors for Industry Conference. ISA/ IEEE, Houston, TX , Nov. 18-20, 2002. 15-18.
Starikov, D., C. Boney, N. Medelci, J-W. Um, A. Bensaoula, M. Larios-Sanz, and G. E. Fox. "Experimental Simulation of Integrated Optoelectronic Sensors Based on III Nitrides," J. Vac. Sci. Tech. B 20.5 (2002): 1815-20.

Funding and proposals
Bensaoula, A. "A Compact Fluorescence/Scattering System." Department of Defense, NAV Y (IMS), $70,000 ($19,000 TcSAM subcontract), Oct. 1, 2002-Mar. 31, 2003.
Medelci-Djezzar, N. "Integrated Multifunctional Fluorescence Sensors for Real Time Environment Effluents and Water Analysis." Texas ATP, $194,000 plus a supplemental grant, $8,100 (support for P. Schuller), Jun. 3, 2002-Aug. 2, 2002.

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Institute for Space Systems Operations - Y2002 Annual Report
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