Torque-driven, 3D-printed microfluidic point-of-care diagnostic devices

Abstract

Current microfluidics-based point-of-care diagnostic platforms require complex and costly fabrication protocols, and bulky auxiliary fluidic instrumentation, limiting their impact in resource-poor environments. 3D-printing has recently emerged as an enabling technology in the manufacturing of microfluidic chips with integrated features iteratively and inexpensively. Herein, I present a versatile, zero-equipment technique which utilizes built-in, torque-driven piston pump-like components for enabling advanced microfluidic operations in 3D-printed devices. By screwing along either thread direction, positive and negative volumetric displacement pressures can be generated, triggering microactuation of fluidics along microchannels, tubings, and capillaries. This mechanism can be exploited to operate complex bioassays via multiple modalities, including chaotic mixing, reagent storage, and sequential delivery, without any reliance on ancillary pumps, valves, or pressure sources. In developing our torque-driven 3D-printed microfluidic chips, I first explored the design and fabrication of threaded movable components, as well as characterization of the finger-powered pumping method. Also, I investigated several methods for improving inertness of the 3D-printed surface against biochemical fouling. A torque-driven, dual 3D-grooved serpentine micromixer chip for rapid blood testing was presented as proof-of-concept demonstration of device utility. Moving forward, I showed that our torque-based pumps can also be utilized in a plug-and-play format in combination with conventional PDMS chips. Furthermore, the pump can be modularly coupled with plug-loaded tubing cartridges to enable sequential dispensing and oscillation of liquid plugs. By combining the torque pump component with capture molecule-functionalized surfaces and reagent-loaded cartridges, complex multi-step, multi-reagent heterogeneous bioassays can be easily performed within stand-alone, disposable devices. I validated the performance of our platform by conducting a slot blot immunofluorescence assay (IFA) for quantifying human IgG levels using nitrocellulose-embedded 3D-printed chips. Additionally, I further developed a hybrid 3D-printed plastic–glass capillary immunodiagnostic device. To demonstrate real-world applicability, using our device I performed capillary-based enzyme-linked immunosorbent assays (ELISA) and indirect IFA for diagnosing chronic Chagas disease in clinical samples. To summarize, in this thesis I have presented an arsenal of 3D-printed microfluidics-based point-of-care diagnostic devices powered by user-friendly torque-driven micropumps. These micropumps were monolithically incorporated as finger-powered microfluidic control elements within various point-of-care platforms. Advantages of our design include: low-cost, portability, disposability, usability, and control of on-chip fluid actuation; thus, negating the need for large external pumps or pressure sources. Therefore, torque-driven microfluidics represent a critical development in zero-equipment disease diagnostics by enabling the finger-powered operation of bioassays on miniaturized, integrated 3D-printed devices.

Date of Award	2018
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology