Flexural Wave Based Acoustofluidic Devices

Abstract

Microfluidic technologies, and the subset of devices that integrate acoustics into their designs (known as acoustofluidic devices), present great potential for solving the challenges of the future. One specific subset of these technologies, termed sharp-edge based acoustofluidics, has shown promise in a variety applications; specifically, previous work has explored the use of this technology in applications such as fluid pumping and mixing, cell stimulation, and bio-sample preparation. However, even though there are a vast number of applications that sharp-edge based acoustofluidics have been applied to, there are several shortcomings that need to be addressed. First, and perhaps most critically, very little is known about the fundamental mechanism of this platform’s operation. The search for novel applications has left a gap in the knowledge base for understanding how these devices work on a fundamental level; gaining a better understanding of how the technology works may open the door to finding new and previously unimagined applications. Second, although not a problem that is specifically limited to sharp-edge based acoustofluidic devices, the technology suffers from serious limitations in real world applicability. That is, even though these devices have advantages over traditional techniques, including speed, cost, and ease of use, they are unable to be taken advantage of. For this reason, there is a critical need to demonstrate a viable pathway to real-world usage. In an attempt to tackle these shortcomings, we begin our research by investigating the vibrational profile generated within a sharp-edge mixer. Throughout this exploration we uncover that the mechanism behind the technology’s success is relatively low frequency flexural waves which have wavelengths commensurate with the overall dimensions of the technology. This is in contrast to the previous belief that waves with lengths many times larger than the device itself were dominating; as a result, we developed and explored a novel platform for particle manipulation based on wave interference (not unlike high frequency based acoustofluidic platforms). This technology offers a new technique for interacting with micro particles and cells in an open fluid chamber. In order to improve the technology’s adoptability, we also developed and characterized two unique and portable control platforms towards eventual point-of-care (POC) use. Altogether, this work serves to further the knowledge and relevance of sharp-edge based technology. It is our hope that this work can serve as a starting point for future explorations into novel platforms which make use of the small wavelength vibrations achievable with this low cost setup. Additionally, we hope that this work may motivate the broader field to transition their technology into equally accessible platforms, such that the microfluidics community as a whole can bring their useful technology to practical applications.