SHARP-EDGE-BASED ACOUSTOFLUIDICS

Open Access
- Author:
- Huang, Po-Hsun
- Graduate Program:
- Engineering Science and Mechanics
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 02, 2016
- Committee Members:
- TONY JUN HUANG, Dissertation Advisor/Co-Advisor
Jun Huang, Committee Chair/Co-Chair
Bernhard R Tittmann, Committee Member
Francesco Costanzo, Committee Member
Siyang Zheng, Outside Member
Corina Stefania Drapaca, Committee Member - Keywords:
- Microfluidics
Acoustofluidics
Acoustic streaming
Micropump
Micromixer
Chemical gradient
Sputum liquefaction - Abstract:
- Over the past few decades, microfluidics has emerged as a powerful tool for a wide variety of applications, from chemical applications, such as monitoring of chemical reactions and material synthesis, to biological applications, such as cell differentiation and single-cell analysis. We have also witnessed the rapid advancement of related technologies. Despite the advancement, the adoption of microfluidic devices in daily human life for diagnostic and therapeutic purposes is still very limited, the reason being that to date, only a few powerful fluid manipulation devices have been proposed. This thesis has centered on understanding, designing, and prototyping a new class of acoustofluidic (i.e., the fusion of acoustics and microfluidics) devices to pave the foundation for applications, ranging from biomedical/chemical research to clinical applications. Implementing the acoustic streaming effect induced by oscillating sharp-edge structures in microfluidics, we have developed a series of sharp-edge-based acoustofluidic technologies that are able to control and manipulate fluids and micro-objects. First of all, an acoustofluidic micromixer is developed where rapid and homogeneous mixing of fluid was achieved via the acoustic streaming induced by oscillating sharp-edge structures. The acoustic streaming induced by the oscillation of sharp-edge structures allows two fluids to interchange and thus enhances the mass transport across the channel, greatly improving the mixing efficiency. Our sharp-edge-based acoustofluidic micromixer possesses desirable characteristics, including excellent mixing performance, simplicity, convenient and stable operation, fast mixing speed, and ability to be toggled on-and-off, which makes it a promising candidate for a wide variety of lab-on-a-chip applications. Built directly on the sharp-edge-based acoustofluidic micromixer, a modified sharp-edge-based acoustofluidic micromixer is developed for the mixing of highly-viscous fluid samples. The capability of our sharp-edge-based acoustofluidic micromixer for the mixing of highly-viscous samples is demonstrated by liquefying human sputum samples on-chip, which, to the best of our knowledge, is the first microfluidic sputum liquefaction device, also known as acoustofluidic sputum liquefier. Our sharp-edge-based acoustofluidic sputum liquefier is a promising candidate for incorporation with other on-chip components that will enable the development of a fully integrated, self-contained sputum processing and analysis platform. In addition, our device can possibly be employed for applications that require the processing of highly viscous fluids. By engineering the acoustic streaming patterns generated inside the microfluidic channel, a sharp-edge-based acoustofluidic chemical gradient generator is presented. The generation of concentration gradients of chemical is due to the serial mixing of different solutions. Through the modulation of the driving signals of piezoelectric transducer, our sharp-edge-based acoustofluidic gradient generator can generate spatiotemporally controllable concentration gradients. The biocompatibility of our sharp-edge-based acoustofluidic gradient generator is validated by carrying out experiments of cell migration, as well as by preserving the cell viability after long-term exposure to an acoustic field. Our device features advantages such as simple fabrication and operation, compact and biocompatible device, and generation of spatiotemporally tunable gradients. Finally, to expand the potential of the acoustic streaming induced by oscillating sharp-edge structure, a highly reliable, programmable acoustofluidic micropump is developed. By engineering the geometry of sharp-edge structure, specifically, tilting the sharp-edge structure, the acoustic streaming pattern generated inside the channel is altered. This altered streaming pattern then produces a net force pointing toward the direction where the sharp-edge structure is tilted; as a result of the net force, fluid pumping motion occurs along the parallel direction where the sharp-edge structure was tilted. Our sharp-edge-based acoustofluidic micropump offers advantages over other microfluidic pumps in terms of not only simplicity, stability, reliability and cost-effectiveness, but also controllability and flexibility, which, when combined, make it valuable for many lab-on-a-chip applications. To sum up, a series of acoustofluidic devices are developed and presented to control and manipulate fluids via the acoustic streaming effect induced by oscillating sharp-edge structures. Due to the advantages of high biocompatibility, ease of manipulation, high flexibility and controllability, and low power consumption, the acoustofluidic technologies that we have developed are invaluable for many microfluidic applications. The work presented in this dissertation serves as an important example and the foundation for the future development of sharp-edge-based acoustofluidic devices.