Date of Award
Doctor of Philosophy in Mechanical Engineering and Applied Mechanics
Mechanical, Industrial and Systems Engineering
This work was motivated by two needs: to develop low-cost, high-sensitivity, and accurate systems for detecting phosphate in seawater, and to create a platform technology by integrating Bi-Material Cantilever (B-MaC) valves for rapid and affordable biosensors that can be used at home or point-of-care settings to detect pathogens.
Detecting low levels of phosphate in the seawater using an inexpensive sensor is crucial for marine scientists to make informed decisions on where to measure next, compared to the current method of collecting samples and analyzing them ashore. To address these needs, we developed a portable infrared lightbox that can be wirelessly controlled by a smartphone. However, internet connectivity is often unavailable at sea. Therefore, we introduced a local internet system that enables the phone to control the sensor and read the measurement results. These results can then be viewed on the phone or downloaded onto a computer onboard the ship. The lightbox allows for easy and convenient use in various settings without the need for complicated equipment or extensive training. By remotely controlling the absorption peak of the molybdenum blue reaction in the infrared region, the lightbox significantly enhances the limit of detection and quantification of two commonly used commercial devices. Specifically, the limit of detection can decrease by up to six times when using the lightbox. A new dip strip paper-based device was also developed that uses a wet chemistry method to detect phosphate in water samples, including seawater. This new device overcomes the limitations of previous paper-based devices by having an increased shelf life, improved reproducibility of results, simpler design, and reduced testing time. The device's limits of detection and quantification are 0.134 ppm and 0.472 ppm for DI water and 0.438 ppm and 1.961 ppm for Sargasso Sea seawater, respectively.
The importance of rapid and accurate infection detection at home or in point-of-care settings has been highlighted by the need for early detection of the COVID-19 virus. Current microfluidic paper-based devices use gold nanoparticles as chroma generators, but they often have low sensitivity and may result in false negative readings. In contrast, the B-MaC valve-based system demonstrated higher sensitivity because it employs enzyme-linked immunoassay (ELISA), which has inherently higher sensitivity compared to gold nanoparticle-based biosensors. Therefore, a new platform for point-of-care diagnostics was developed that consists of two B-MaC valves housed in a specially designed container. The container includes a reagent storage and release system that reduces variability compared to previous storage methods. The platform can detect rabbit IgG in a buffer using ELISA. It is simple, inexpensive, and fully automated, with the user only needing to place the sample at the beginning of the test. The limit of detection and quantification for this platform is 2.27 ng/mL and 8.33 ng/mL, respectively, which represents a significant improvement of over 58% compared to previous portable microfluidic technology for detecting rabbit IgG in buffer using ELISA.
Heidaribafroui, Hojat, "MICROFLUIDIC PAPER-BASED DEVICES FOR THE DETECTION OF CHEMICAL AND BIOLOGICAL AGENTS" (2023). Open Access Dissertations. Paper 1511.