Development of a Point-Of-Care Lensless Birefringent Molecule Detection System

This thesis is a proof-of-concept exploration of an optical birefringent Point-Of-Care (POC) detection device. Birefringent detection can be useful for monitoring glucose and cholesterol, as well as diagnoses of diseases such as malaria, Ebola, bacterial infection and AIDS. Many diseases cause optical birefringent materials to precipitate in blood. These precipitates can be used as a biomarker to diagnose the disease. In this thesis, we will focus on the development of a device for detection of a birefringent phantom, called Tetrabutylammonium (TA), suspend in deionized water. We will show a method for, a low cost, Point-Of-Care, and easy to use birefringent detection platform. This thesis builds on the concepts of flow cytometry for detection of depolarized light and uses these concepts for the development of a miniaturized optical birefringent detection setup, utilizing a lensless design, for a sample flowing through a microchannel. A microfluidic channel with a serpentine shape was developed in order to increase the volume of sample present within the detection area, while also decreasing the total volume used per measurement by reducing the cross sectional area of the channel. To demonstrate the concept of birefringent detection, a bulk optic setup was developed which used two detection channels. The two detection channels were a 2 dimensional (2D) Charged Coupled Device (CCD) and a 1 dimensional (1D) Avalanche Photodiode (APD). Using the bulk optic setup, we compared 2D imaging with 1D sensing and compared the ability of the two detectors to identify detection events. We identify detection events at a concentration of 1 µg/mL of TA using both 1D sensing and 2D imaging in the bulk optic setup, before using a 1D APD detector for the miniaturized optical setup. In the miniaturized optical setup, we detected events at the same concentration limit.