Microparticle Acoustophoresis in Aluminum-Based Acoustofluidic Devices with PDMS Covers

Abstract

We present a numerical model for the recently introduced simple and inexpensive micromachined aluminum devices with a polydimethylsiloxane (PDMS) cover for microparticle acoustophoresis. We validate the model experimentally for a basic design, where a microchannel is milled into the surface of an aluminum substrate, sealed with a PDMS cover, and driven at MHz frequencies by a piezoelectric lead-zirconate-titanate (PZT) transducer. Both experimentally and numerically we find that the soft PDMS cover suppresses the Rayleigh streaming rolls in the bulk. However, due to the low transverse speed of sound in PDMS, such devices are prone to exhibit acoustic streaming vortices in the corners with a relatively large velocity. We predict numerically that in devices, where the microchannel is milled all the way through the aluminum substrate and sealed with a PDMS cover on both the top and bottom, the Rayleigh streaming is suppressed in the bulk thus enabling focusing of sub-micrometer-sized particles.

Numerical study of acoustic cell trapping above elastic membrane disks driven in higher-harmonic modes by thin-film transducers with patterned electrodes

“…The basic theory and modeling for such a thin-film PZE-transducer-driven acoustofluidic system, was developed in a perturbation scheme involving the acoustic first-order fields and the steady time-averaged secondorder fields in our previous work [3], founded on the theory for bulk PZE-transducer-driven systems [22] taking the acoustic boundary layers into account analytically through effective boundary conditions [23]. Numerical simulations based on this theory have been validated experimentally for several different microscale acoustofluidic systems [2,9,10,22]. In the following we briefly summarize this basic theory and its numerical implementation and adapt the previous cartesian-coordinate formulation into the cylindrical coordinates of the present axisymmetric system.…”

“…However, when dealing with bulk acoustic waves (BAW), the topic of this work, electrode shaping is rarely used, and not at all for the above-mentioned membrane devices. A simple split-electrode configuration with an applied anti-symmetric driving voltage, has been used on experiments on bulk piezoelectric (PZE) transducers [9,10] and on thin-film transducers [1] to obtain a strong excitation of anti-symmetric modes for optimal particle focusing. Such systems has also been studied in numerical simulations [3,[11][12][13].…”

Acoustophoresis in polymer-based microfluidic devices: modeling and experimental validation

“…To ensure an optimal anti-symmetric motion in the yz plane, the top electrode of the transducer is split in two halves by cutting a small groove using a dicing saw along the x-direction and driven by respective AC-voltages with a 180°phase difference similar to the work reported in the literature. 9,17,18 III. THEORY…”

Acoustofluidic separation enables early diagnosis of traumatic brain injury based on circulating exosomes

“…The underlying mechanism of acoustofluidics uses acoustic waves to generate acoustic radiation forces on particles in the fluid; the strength of the acoustic radiation force depends on the size and density of the particle 12,[29][30][31][32][33] . The high biocompatibility of acoustofluidic devices also benefits downstream analysis by providing samples with complete structures and components [34][35][36][37][38] . Previously, we used acoustofluidics to separate bioparticles, including cells, bacteria, and platelets, in a highly biocompatible manner [39][40][41] .…”