Finger-Powered Thermoplastic Microfluidic Electrochemical Assay for Diagnostic Testing Using a Mobile Phone

摘要

Point-of-care (POC) testing has gained considerable attention in recent years due to its ability to provide diagnostic information without the need for centralized laboratory facilities or bulky equipment. This has been achieved, in part, by advances in micro-electro-mechanical system (MEMS) and analytical chemistry, which has resulted in the miniaturization and integration of sensitive biosensors and fluidic components. Recently, researchers have demonstrated the use of mobile phones for POC testing, which offers the advantages of portability and wireless data transmission. Many mobile phone-based POC tests are based on optical imaging or colorimetric assays, which are useful for some diagnostic applications, but lack the accuracy and sensitivity required for the diagnosis of many important diseases. Moreover, these devices employ microfluidic chips fabricated using glass, polydimethylsiloxane (PDMS) or paper, which require complex microfabrication or surface treatments, or offer limited fluidic control.;In this dissertation, we explored the development of plastic-based microfluidic chips for rapid electrochemical measurements of protein biomarkers using a mobile phone biosensing platform. We first investigated UV/ozone (UVO) surface treatment on plastics to better understand its usefulness for microfluidic POC applications. We found that UVO-treated poly(methyl methacrylate) (PMMA), cyclic olefin copolymer (COC) and polycarbonate (PC) experience hydrophobic recovery within 4 weeks and the rate at which it occurs is dependent on the UVO treatment duration. Furthermore, we discovered that the hydrophobic recovery of UVO-treated COC and PC can be inhibited by storing them in dehumidified or vacuum conditions. UVO-treated plastics were also used for protein adsorption measurements, which showed that UVO treatment minimized protein adsorption and this effect is correlated with the treatment duration. Lastly, we demonstrated capillary-driven flows in UVO-treated PMMA microchannels, which revealed that the flow rate can be tuned by adjusting the treatment duration.;We also explored the development of new fabrication methods for generating plastic microfluidic devices. In particular, we have demonstrated for the first time the use of 3D printed metal molds for fabricating plastic microchannels via hot embossing. Through the optimization of the powder composition and processing parameters, we generated stainless steel molds with superior material properties (density and surface finish) and replication accuracy compared with previously reported 3D printed metal parts. 3D printed molds were used to fabricate PMMA replicas, which exhibited good feature integrity and replication quality. Microchannels fabricated using these replicas exhibited leak-free operation and comparable flow performance as microchannels fabricated from CNC milled molds for both capillary and pressure-driven flows.;Toward the realization of a shelf stable, electricity-free microfluidic assay for POC testing, we developed a finger-powered microfluidic chip for electrochemical measurements of protein biomarkers. This device employs a valveless, piston-based pumping mechanism which utilizes a human finger for the actuation force. Liquids are driven inside microchannels by pressing on a mechanical piston, which generates a pressure-driven flow. Dried reagents are preloaded in microwells allowing for the entire testing process to be completed on-chip. Additionally, a nonenzymatic detection scheme is employed which circumvents the need for refrigeration. For proof-of-concept, this microfluidic assay was coupled with a mobile phone biosensing platform for quantitative measurements of Plasmodium falciparum histidine-rich protein-2 (PfHRP2) in human blood samples. Using this platform, PfHRP2 was detected from 1 to 20 microg/mL with high specificity and each measurement could be completed in ≤ 5 min. In addition, this assay can be stored at room temperature for up to one month with a negligible loss in performance. The results and knowledge presented in this dissertation will provide new insights into the development of plastic microfluidic devices for POC testing as well as other biomedical application.