University of Houston • University of Houston-Clear Lake • ISSO Annual Report Y2006 • 71
Miniature Optical Sensors for Detection of Water and Air Contaminations
ABSTRACT—During the past years, several complex, bulky, and expensive spectroscopic instruments have been replaced by portable systems based on solid-state components. This project developed multi-band LED chips and solid-state photodetectors integrated into a miniature portable system capable of detection and quantification of a large variety of effluents in a gas, liquid, or solid form.
Fluorescence intensity measurements are now utilized in hand-held compact sensors for detection of important compounds in various applications. However, the detection and quantification capabilities of these devices are still much lower than those of laboratory-based measurement systems. Any effluent that interacts with light in the range from near ultraviolet to near infrared in the form of at least one of the following phenomena — optical absorption, reflection, scattering, luminescence, or fluorescence — can be potentially identified and characterized by the system. System operation and signal acquisition rely upon the latest state-of-the-art developments in signal coding and electronic circuit design and allow measurements with an accuracy of few ppm.
Identification and characterization of various compounds is based on the employment of artificial neural network architecture, built upon the principles of a human brain. The inherent spectral selectivity results in unique spectroscopic signal patterns from each tested effluent. These patterns are used to train the neural network first, in order to provide for their future identification by the system.
Goal
The goal of this current project is to further improve the performance of the portable system, based on light intensity, by the introduction of fluorescence lifetime (temporal) measurements, which are extremely sensitive to the specific compound signatures.
Results
Preliminary results have shown higher than 70% accuracy achieved in detecting E. coli bacteria without any knowledge of the tested environment. Under similar conditions, accuracies from important organic effluents exceeded 90%, and soared to 98-100% when data on the environment were fed into the neural network. The rapid development of semiconductor technology has enabled the solid-state components to satisfy critical requirements for lifetime measurements. Our first-of-a-kind portable lifetime measurement system utilizes LEDs as excitation sources and fast photodiode or reverse-biased LEDs as photodetectors.
This system can be tailored for specific applications as well as for universal use. The III nitride based components used in the sensor design allow for its operation in normal and super-ambient environments related to the following applications: detection and characterization of crude oil, oil in seawater, environmental pollution, bio-chemical hazards in military and industrial process control and monitoring, health monitoring in the biomedical field, identification and characterization of the variables in space applications, and the quality assurance of drugs in the pharmaceutical industry.
A new high-sensitivity intelligent lifetime based prototype is currently under development in collaboration with the Bio-Processing Laboratory at the University of Quebec at Montreal (UQAM). This project is supported by current US Air Force Phase II SBIR contract on the development of advanced fire/flame detectors.
Publications
Starikov, D., C. Boney, R. Pillai, and A. Bensaoula. "Solar-Blind Dual-Band UV/IR Photodetectors Integrated on a Single Chip," Proc. of the 2006 NSTI Nanotechnology Conference and Trade Show, Nanotech 2006 3.1 (2006): 74-77.
Presentations
Boney, C., P. Misra, and A. Bensaoula. "Dependence of Impurity Incorporation on the Growth Temperature During GaN MBE Growth," North American MBE Conference, Durham, North Carolina, Oct. 8-11, 2006.
Joseph, C., M. Boukadoum, J. Charlson, D. Starikov, and A. Bensaoula. "High-Speed Front End for LED-Photodiode Based Fluorescence Lifetime Measurement System," 2007 IEEE Intl. Symposium on Circuits and Systems, New Orleans, LA, May 27-30, 2007. (Accepted.)
Starikov, D., C. Boney, R. Pillai, and A. Bensaoula. "Solar-Blind Dual-Band UV/IR Photodetectors Integrated on a Single Chip," Proc. of the 2006 Nanotechnology Conference and Trade Show, Nanotech 2006 3.1 (2006): 74-77.
Starikov, D., C. Boney, R. Pillai, and A. Bensaoula. "Visible-Blind UV/IR Photodetectors Integrated on Si Substrates," Proc. of the 2006 MRS Spring Meeting, San Francisco, CA, April 17-21, 2006. (Accepted.)
Tabari, K., M. Boukadoum, A. Bensaoula, and D. Starikov. "Neural Network Processor for a FPGA-based Multiband Fluorometer Device," The International Workshop on Computer Architecture for Machine Perception and Sensing, Sept. 2006.
Funding and Proposals
Starikov, D. "Integrated Broad-Band Optical Calibration Sources for Star Simulation," NSF Phase II SBIR project (IMS/CAM), $60,000 (Submitted.)
Starikov, D. "Solid-State High Temperature Jet Engine Fire Detector," Air Force Phase II SBIR project (IMS/CAM), 2005-2007, $250,000.
Institute for Space Systems Operations - Y2006 Annual Report
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