Acoustically Driven Micro Electro-Mechanical Mixers for Biomedical Applications

Open Access
Orbay, Sinem
Graduate Program:
Master of Science
Document Type:
Master Thesis
Date of Defense:
June 09, 2016
Committee Members:
  • Jun Huang, Thesis Advisor
  • Jian Yang, Committee Member
  • Siyang Zheng, Committee Member
  • Micromixing
  • high-viscosity fluid
  • acoustofluidics
  • polyethylene glycol (PEG)
  • High viscosity fluids
  • Acoustofluidics
  • Artificial cilia
Microelectromechanical systems (MEMS) have become enabling technologies on many research areas. In this dissertation, we present the use of acoustofluidic MEMS for bioengineering applications. Firstly, we demonstrate an acoustofluidic micromixer, which can perform rapid and homogeneous mixing of highly viscous fluids in the presence of an acoustic field. In this device, two high-viscosity polyethylene glycol (PEG) solutions were co-injected into a three-inlet PDMS microchannel with the center inlet containing a constant stream of nitrogen flow, which forms bubbles in the device. When these bubbles were excited by an acoustic field generated via a piezoelectric transducer, the two solutions mixed homogenously due to the combination of acoustic streaming, droplet ejection, and bubble eruption effects. The mixing efficiency of this acoustofluidic device was evaluated using PEG-700 solutions, which are ~106 times more viscous than deionized (DI) water. Our results indicate homogenous mixing of the PEG-700 solutions with a ~0.93 mixing index. The acoustofluidic micromixer is compact, inexpensive, easy to operate, and has the capacity to mix highly viscous fluids within 50 milliseconds. Secondly, we present acoustically actuated artificial cilia, which can also perform mixing into the PDMS microchannel as the natural cilia do. For the fabrication of artificial cilia structure into the channel, in situ fabrication method is used for the first time. In order to demonstrate the mixing performance of the artificial cilia device, we injected DI water and DI water + fluorescein powder solution via inlets and calculated the mixing index as ~0.9.