Thermoplastic Acoustofluidic Platforms for Micromixing Applications and Nanoparticle Synthesis

Abstract

Microfluidics is an interdisciplinary field encompassing precise control and manipulation of fluids at microscale dimensions, which is of great interest in many fields, especially in biomedical applications, for example, biochemical analysis, disease diagnosis, and drug delivery. Inherent in conventional microfluidic channels is the laminar flow regime due to its microscale dimensions which facilitates separation and sorting applications. However, this feature impedes fluid mixing in microchannels for applications such as nanoparticle (NP) synthesis for drug delivery, where diffusion is the main contributor for mixing. To that end, different active mixing techniques are implemented to enhance the mixing performance in microchannels via the application of external physical fields. Acoustofluidics, a discipline within microfluidics, deals with the interaction of sound waves and fluid flow in microchannels, where the applied sound waves induces rotational vortices which enhances the mixing performance and overcomes the limitations imposed by diffusion.
Moreover, there is a growing interest within the microfluidics field in exploring alternative materials, replacing the traditionally utilized silicon and glass with materials that are low-cost, easy to process, and can transition to large scale production economically. In addition, novel materials should exhibit high chemical-solvent resistivity, surface modification and functionalization, and biocompatibility. Cyclic olefin copolymer (COC) is a promising candidate which exhibits all these characteristics in addition to being versatile in their fabrication methods. Where they have been incorporated in many microfluidic applications including passive micromixers, blood analysis, DNA analysis, and liposome synthesis. However, to date, acoustofluidic COC platforms have not been developed for acoustic mixing applications.
This dissertation presents the development of a microfabrication technique to build low-cost thermoplastic (COC) microfluidic devices for mixing applications. The developed technique combines microchannel fabrication and bonding processes in a single step, taking advantage of COCs’ swelling behavior in linear non-polar hydrocarbon solvents and their chemical compatibility with photolithography. The presented method was utilized to build acoustofluidic platforms, where the interaction of sound waves with the fluid flow induces an acoustic streaming force which enhances the mixing performance, where COC has a higher elastic modulus and acoustic impedance in comparison to the conventionally used polydimethylsiloxane (PDMS) in acoustic applications. Mixing was achieved through a sharp edge microfluidic design based on bulk acoustic wave (BAW) interaction with the fluid, where along with experimental investigation, numerical modeling was implemented and verified with experimental results. Moreover, a simple and irreversible bonding process between COC and PDMS was developed based on an organosilane coupling agent to build hybrid microchannels for COC pillar based acoustic streaming mixing applications. Finally, the developed COC fabrication technique was employed for the synthesis of nanoscale lipid-based drug delivery vesicles, liposomes, through the acoustic streaming mechanism mediated nanoprecipitation. We believe this dissertation is an essential work towards the integration of thermoplastics and acoustofluidics for further utilization in biomedical applications.

Date of Award	14 Dec 2023
Original language	American English
Supervisor	Anas Alazzam (Supervisor)