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Bacteria Counter Wade May Co-Advisors: Dr. Todd Giorgio, Ph.D Dr. Bob Galloway, Ph.D Dept. of Biomedical Engineering Copyright © 1999 Vanderbilt University Problem/Market • Chemical plants, treatment facilities, etc... have large volumes of fluid traveling through piping systems. – This fluid is always susceptible to bacterial contamination. • There is not a quick, cheap, and accurate way to measure bacterial concentrations in these fluids. – Current methods used take 24 hours to give an estimate of bacterial concentrations. – At large plants, 24 hours of unusable products can represent a loss in excess of $100,000. Dept. of Biomedical Engineering Copyright © 1999 Vanderbilt University Goals/Objectives • Develop a simple, effective device that will measure bacterial concentrations in an aqueous medium. • The device should be relatively cheap (expensive methods already exist). • Measurements should be available in a short period of time (less than 10 minutes). • The device should perform its task with minimal or no safety hazards. Dept. of Biomedical Engineering Copyright © 1999 Vanderbilt University Current and New Methods Current bacteria counters Standard culture in petri dish Sani-Check accelerated culture Flow cytometer Coulter counter Aber capacitance measurement Magnetic separation Birefringence detection Dept. of Biomedical Engineering Time Accuracy Expense 2-3 days accurate min 24 hours rough estimate min < 10 min near exact max < 10 min near exact high < 10 min ? ? < 10 min ? low < 10 min near exact moderate Copyright © 1999 Vanderbilt University Proposed Solutions • Magnetic Separation – Separate bacteria in a strong magnetic field and measure the induced voltage due to their charge. – This could be added online in a facility such as a chemical plant. – This device would be fairly inexpensive, safe, and could provide real-time measurements. • Detection of Birefringence – Observe small sample of fluid under cross polarizers and look for the birefringence of the cell membrane. – Amount of light transmitted proportional to concentration of bacteria in known volume. – Quick optical method with no safety hazards. Dept. of Biomedical Engineering Copyright © 1999 Vanderbilt University Work Completed • Literature search. • Faculty meetings and discussions. • Magnetic Separation system design and prototype construction. • Preliminary testing with prototype. • Birefringence Detection initial system design. • Observation of bacteria under cross polarizers. • Started image processing program. Dept. of Biomedical Engineering Copyright © 1999 Vanderbilt University Birefringence Data Original Image Dept. of Biomedical Engineering Processed Image Copyright © 1999 Vanderbilt University Magnetic Separation Data • Successfully induced voltage due to separation of ions in saline. – Signal is very unstable and difficult to work with. – Equipment is crude at best. • Will attempt to detect red blood cells in the next couple of days. – Have increased gain from 120 to 1200. – Will document with pictures. Dept. of Biomedical Engineering Copyright © 1999 Vanderbilt University Future Work • Magnetic Separation – Test system with PBS. – Test system with PBS and blood. – Analyze data and design. • Birefringence Detection – Finish program to determine bacterial concentration. – Consider details of the overall system design. – Determine next steps to be taken. • Construct Poster Presentation • Write Final Paper Dept. of Biomedical Engineering Copyright © 1999 Vanderbilt University