High-speed dual-wavelength optical polarimetry for glucose sensing

Abstract

To non-invasively measure glucose concentrations across the aqueous humor of the eye, a high-speed, dual-wavelength optical polarimetric approach is proposed that addresses a key limitation of prior set-ups -system response time -while compensating for time-varying motion artifact due to corneal birefringence.This research is made up of three goals. The first goal is to design and construct a high-frequency, ferrite core Faraday rotator that can both rotate and modulate linearly polarized light in a frequency range of 30 to 75 kHz. The second goal is to implement a single ferrite core Faraday rotator into the current polarimetric approach. The third goal is to replace three air-core Faraday rotators with two ferrite core Faraday rotators for both modulation and compensation, allowing for two different signals to be measured on a single photodetector.In vitro phantom studies are performed with and without motion artifact. The sensor is shown to stabilize in ~2 msec and provide standard errors for glucose concentration of less than 13 mg/dL in the presence of motion. The results indicate that higher frequency modulation can reduce the overall system stabilization time with minimal loss of accuracy in the presence of motion artifact. iii ACKNOWLEDGEMENTS I would like to thank my committee chair, Dr. Gerard L. Coté, for his guidance, advice, and support through the course of this research. His professionalism and focus on various projects at the same time as performing his duties as department head have shown me the key qualities I strive for now and during my career. I couldn't have completed this work without him. I would also like to thank my committee members, Dr. Mary P. McDougall and Dr. Prasad Enjeti, for their support and their time. Their guidance through theory and design pointed me in the right directions. Mr. Erwin Thomas III and Dr. Bilal Malik both guided me in new and interesting directions as well.Thanks also go to my friends, including but not limited to

Dual-modulation, dual-wavelength, optical polarimetry system for glucose monitoring

“…Optical polarimetry for glucose monitoring has been thoroughly discussed in the literature. [17][18][19][20][21][22][23][24][25][26][27][28][29][30][31][32] Briefly, polarimetry was first used in the food industry in 1956 23 and was first proposed as a possible method for noninvasive glucose monitoring across the aqueous humor of the eye in 1982. 17 The advantages that were shown over the years were that the aqueous humor glucose is correlated with blood glucose, it is a clear medium with negligible loss of polarization due to scattering effects, had the submillidegree sensitivity to measure the small rotations, and had the potential to overcome motion artifact.…”

“…A second system was developed using ferrite-based FM to decrease the stabilization time. 32 Although using the new ferrite FM provided improved system response speed, it still required the more complex two detectors for differentiating the two wavelength signals and suffered from electromagnetic interference and 1∕f noise.…”