Microparticle collection and concentration via a miniature surface acoustic wave device

Abstract

The ability to detect microbes, pollens and other microparticles is a critically important ability given the increasing risk of bioterrorism and emergence of antibiotic-resistant bacteria. The efficient collection of microparticles via a liquid water droplet moved by a surface acoustic wave (SAW) device is demonstrated in this study. A fluidic track patterned on the SAW device directs the water droplet's motion, and fluid streaming induced inside the droplet as it moves along is a key advantage over other particle collection approaches, because it enhances microparticle collection and concentration. Test particles consisted of 2, 10, 12 and 45 microm diameter monodisperse polystyrene and melamine microparticles; pollen from the Populus deltoides, Kochia scoparia, Secale cerale, and Broussonetia papyrifera (Paper Mulberry) species; and Escherichia coli bacteria. The collection efficiency for the synthetic particles ranged from 16 to 55%, depending on the particle size and surface tension of the collection fluid. The method was more effective in collecting pollen and the bacteria with an efficiency of 45-68% and 61.0-69.8%, respectively. Pollen collection was strongly influenced by its diameter, size, and surface geometry in a manner contrary to initial expectations. Reasons for the consistent yet unexpected collection results include leaky SAW pressure boundary segregation and shear-induced concentration of larger particles, and the subtle effects of wetting interactions. These results demonstrate a new method for collecting microparticles requiring only about one second per run, and illustrate the inadequacy of using synthetic microparticles as a substitute for their biological counterparts in experiments studying particle collection and behavior.

Microscale Capillary Wave Turbulence Excited by High Frequency Vibration

“…Wave energy may be absorbed into a fluid in contact with the substrate through the phenomenon of "leaky SAW". 48 The principal features of SAW excitation are its high frequency, the fact the substrate undergoes a rapid phase change in its displacement over the propagation path of the SAW, and the presence of inplane and transverse components of vibration that are onequarter of a wavelength in time out of phase with each other.…”

Efficient manipulation of microparticles in bubble streaming flows

“…Many applications require control over position and concentration of the objects in order to induce mixing, 3 chemical reactions, 4 biomolecular tagging, 5 or a host of other processes. The necessary manipulations of the objects often rely on actively applying various external force fields, including hydrodynamic (inertial), [6][7][8] electrokinetic, 9-12 dielectrophoretic, [13][14][15][16] magnetic, 17,18 optical 19,20 or acoustic [21][22][23] (ultrasound standing waves, surface acoustic waves) forces. Such forces will usually act differently on particles depending on their size, geometry, and mechanical or electromagnetic properties; as a result, particle separation and sorting become possible.…”

Continuous sheathless microparticle and cell patterning using CL-SSAWs (conductive liquid-based standing surface acoustic waves)

“…By the constructive and destructive interference of SAWs, a SSAW with either pressure nodes (minimum pressure amplitude) or pressure anti-nodes (maximum pressure amplitude) is formed in the microchannel. [41][42][43] The microparticles or cells can be captured at either nodes or anti-nodes depending on the relative density and compressibility of the particles and the suspending medium. 26,44,45 In this experiment, the CL-SSAW device was designed to have either a single pressure node or a single anti-pressure node at the center of the microchannel.…”