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Retroreflectors can potentially be used in the design of a minimally invasive glucose-monitoring device. The primary objective of this senior design project is to design, build, and test a system to show that retroreflectors can be detected through a semi-opaque medium similar to human tissue. The secondary objective is to determine if the system can detect the retroreflectors through blood with and without gold nanoparticles. The design constraints of the project are described as well as the design of the apparatus, the test setup and procedure protocols for the project, the results of these tests, and a conceptual design. Data from the test procedure is collected by using a HeNe laser that shines through one converging lenses, an iris, a beam splitter, a semi-opaque medium to emulate human tissue, and gold nanoparticles that mimic glucose molecules in blood. The light hits a retroreflector that sends the light back through the beam splitter to a photodiode that is hooked up to a digital multimeter to measure the detected signal. A full factorial two factor Design of Experiments (DOE) with three levels is used to test the apparatus. Nanoparticle concentration and angle of incidence on the retroreflector are the dependent variables. The DOE is run two times for the water medium, but the testing of semi-opaque media are unable to be performed due to scattering of the beam. In deionized water, minimal interaction effects between nanoparticle concentration and angle are observed, and light scattering appears to increase as nanoparticle concentration increases. In blood, significant interaction effects are observed, and light scattering appears to decrease as nanoparticle concentration increases. This unexpected trend is likely due to unforeseen interactions between the nanoparticles and the solutes in blood. It is concluded that the apparatus is sufficient to provide results for the water medium, and insufficient for more opaque media due to scattering. Altered nanoparticles are needed for testing in blood.
Adams, Rob; Araiza, Luis; Frerich, Colby; Johnson, Will; and Shah, Sarita, "Final Project Report: Glucose Monitoring Group" (2008). Engineering Senior Design Reports. 15.