Discipline: Technology and Engineering
Subcategory: Biomedical Engineering
Lesley Martinez - University of Washington
Co-Author(s): Wendy Thomas and Uyen Tran, University of Washington, Seattle
Bacterial endocarditis is a grave illness caused by the adhesion of bacteria in injured or malformed areas of the heart in addition to the endocardium or the endothelium. There is currently a lack of understanding of the mechanical aspects of bacterial adhesion to the heart. Past studies done to understand bacterial adhesion have failed to provide a reliable model as they have assumed laminar flow of blood, which is not representative of the human heart. In an attempt to comprehend bacterial adhesion in the heart, the Wendy Thomas Laboratory has developed an apparatus that more closely simulates the flow of blood within the heart. The device uses a microvalve that directs suspended bacteria through a flow chamber. When the bacteria pass through the flow chamber, they can be tracked using a microscope and adhesion rates can be measured in different parts of the chamber. The use of the microvalve is especially valuable as it is able to provide pulsatile flow with a quick response time. The hypothesis of this research is whether the current design can be improved, specifically to develop a simulation that can predict how the flow in the chamber varies when the individual components are modified. We proposed that this model can be created by calculating the damping (resistance) of each of the components of the flow chamber. While the resistance of the tubes can be calculated theoretically, it may be more effective to directly measure the rate of flow through the different tubes and use that information to calculate the actual resistance of the tubes used in the apparatus. The methodology used to calculate the damping of a 40 cm long 1.5875 mm inner diameter tube was designed so that the control variables were the length and inner diameter of the tube. Based on this, the rate of flow of de-ionized water induced by a constant pressure could be measured and the damping calculated. A filtering glass flask was filled with 250 mL of de-ionized water with a two-hole stopper secured on the opening. A stockcock, used to control pressure, was placed in one hole and the 40 cm long tube was placed in the other hole. The opposite end of the tube was placed inside a graduated cylinder. Pressure was inserted into the filtering flask using an air compressor set to 0.4 psi. When the water reached 10 mL and 20 mL in the graduated cylinder, the time and height differences were recorded. The water was returned to its original volume in the flask and the procedure was repeated for 0.2 psi. The average of the 0.2 psi and 0.4 psi resistances was 2.3e9 kg/sm^4, which when compared to the theoretical resistance (2.6e9 kg/sm^4) had a 12.8% error. While this error is negligible when the larger scope of the project is considered, it is imperative the methodology is verified by using different parameters. Furthermore, the resistance of the microvalve and the flow chamber itself must also be calculated in order to complete the simulation.
Funder Acknowledgement(s): Anne Dinning, Michal Wolf, University of Washington Genom Project Grant (NIH 5R25HG007153-4).
Faculty Advisor: Wendy Thomas, firstname.lastname@example.org
Role: My contribution was in devleloping the methodology that would allow us to accurately measure the rate of flow, taking pressure changes due to changes in height of water into account. Then I took the measurements of rate of flow, calculated the experimental damping and theoretical damping, and finally compared them to each other.