Development of integrated whole-teflon microfluidic film chips

Abstract

Microfluidic technology has emerged as a powerful tool in various scientific and industrial fields, such as micro-and nanofabrication, chemical synthesis, single-cell analysis, pharmaceutics, wearable electronics, and point-of-care diagnostics. The rapid growth in these disciplines is driven by the increasing synergy between device materials and microfluidic capabilities. Traditional materials in microfluidics often present limitations that impede the performance and application scope of microdevices. Recently, perfluorinated polymers (Teflon) have gained attention as an alternative material for microfluidics due to their exceptional chemical resistance and surface inertness. Despite their potential, challenges remain in developing efficient fabrication methods for integrated Teflon microfluidic devices for practical applications, such as flow chemistry. This thesis presents a series of studies on microfluidic technology, focusing on innovative microfabrication methods using Teflon materials and the applications of Teflon devices. Key issues addressed include the development of microfabrication strategies for thin Teflon films, the integration of microfluidic components, and the application of Teflon microfluidic devices in flow chemistry. Specifically, this thesis introduces fabrication methods, distinct from conventional approaches, for the production of microfluidic chips with thin Teflon films. Additionally, this thesis explores the development and integration of robust, high-performance microfluidic components—such as interconnectors, micromixers, microvalves, and microelectrodes—into the developed microfluidic platforms. The integrated Teflon microfluidic film chips demonstrate their utility in flow chemistry applications, such as photochemical synthesis. The first section introduces Teflon-based microfluidic devices fabricated using a cost-effective approach. These Teflon microfluidic film chips leverage the advantages of Teflon materials and thin film structures, offering exceptional chemical resistance, high transparency, flexibility, and efficient heat transfer. A robust chip-to-world interface is established through the development of adhesive-free, solvent-resistant interconnectors; and the easy integration and functionalization of microvalves for fluid manipulation was demonstrated. As a proof of concept, the versatility and enhanced performance of Teflon microfluidic film chips in flow chemistry are validated through an on-chip photochemical reaction. The second section presents a simplified and scalable fabrication method for whole-Teflon microfluidic film devices. This method provides a scalable, cost-effective solution for producing film-based Teflon microfluidic devices with enhanced production efficiency and commercialization potential. The resulting devices are significantly thinner and more flexible, capable of covering large areas with extended microchannels. Various chip configurations, including 3D microfluidic networks and multiple inlets, are achievable. Microelectrodes are easily integrated into the Teflon film chips for electrochemical applications. The favorable properties of these film chips for flow chemistry applications, such as efficient heat transfer, waterproofing, and air impermeability, are demonstrated. The third section reports a 3D micromixer based on the splitting–stretching–recombination (SSR) of streams to facilitate molecular diffusion, effectively mixing solutions with low Reynolds numbers (0.01–10). The micromixer fabrication involves two-photon polymerization (2PP) 3D printing and soft lithography, offering high resolution and reproducibility. The micromixer features a highly compact design and can be easily integrated into microfluidic platforms. It achieves high mixing efficiency for low-Re solutions (flow rates ≤60 μL/min) with a mixing volume smaller than 20 nL, and the complete mixing time is in the range of milliseconds. The device maintains high performance with highly viscous solutions and solutions containing macromolecules and nano-sized colloids.

Date of Award	2024
Original language	English
Awarding Institution	The Hong Kong University of Science and Technology
Supervisor	Hongkai WU (Supervisor)