Acoustophoretic Control of Microparticle Transport Using Dual-Wavelength Surface Acoustic Wave Devices

Abstract

We present a numerical and experimental study of acoustophoretic manipulation in a microfluidic channel using dual-wavelength standing surface acoustic waves (SSAWs) to transport microparticles into different outlets. The SSAW fields were excited by interdigital transducers (IDTs) composed of two different pitches connected in parallel and series on a lithium niobate substrate such that it yielded spatially superimposed and separated dual-wavelength SSAWs, respectively. SSAWs of a singltablee target wavelength can be efficiently excited by giving an RF voltage of frequency determined by the ratio of the velocity of the SAW to the target IDT pitch (i.e., f = cSAW/p). However, the two-pitch IDTs with similar pitches excite, less efficiently, non-target SSAWs with the wavelength associated with the non-target pitch in addition to target SSAWs by giving the target single-frequency RF voltage. As a result, dual-wavelength SSAWs can be formed. Simulated results revealed variations of acoustic pressure fields induced by the dual-wavelength SSAWs and corresponding influences on the particle motion. The acoustic radiation force in the acoustic pressure field was calculated to pinpoint zero-force positions and simulate particle motion trajectories. Then, dual-wavelength SSAW acoustofluidic devices were fabricated in accordance with the simulation results to experimentally demonstrate switching of SSAW fields as a means of transporting particles. The effects of non-target SSAWs on pre-actuating particles were predicted and observed. The study provides the design considerations needed for the fabrication of acoustofluidic devices with IDT-excited multi-wavelength SSAWs for acoustophoresis of microparticles.

Nano‐Scale Particle Separation with Tilted Standing Surface Acoustic Wave: Experimental and Numerical Approaches

“…The commercial software COMSOL Multiphysics (https://www.comsol.com, Version 5.4) was used to perform the numerical simulation working based on the Finite Element Analysis (FEA). Most of the previously reported studies [ 28,31 ] considered 2D cross‐sections of the acoustofluidic device in their numerical analysis due to the uniformity of the LSSAW field in the longitudinal direction of the microchannel. However, this assumption is not valid for the tSSAW configuration as the microchannel is tilted with respect to the traveling SAWs propagation.…”

“…In fact, simulations have been used for micro-scaled acoustic modeling, including SAW, [26][27][28][29] and more recently, an analytical model developed for tSSAW devices. [25,30] Most of the previously reported numerical modeling [28,31] considered 2D cross-sections of the acoustofluidic chip in their analysis due to the uniformity of the SSAW field in the longitudinal direction of the microchannel. However, this assumption is not valid for tSSAW devices as the microchannel is tilted with respect to the propagation direction of the traveling SAWs.…”

Surface Acoustic Wave (SAW) Sensors: Physics, Materials, and Applications

“…The relevant interaction takes place in the presence of the surface acoustic waves generated by the piezoelectric substrate and analysis are made. Figure 23 [ 185 ] shows the schematic of a generic microfluidic-based sensing platform.…”

Continuous Particle Aggregation and Separation in Acoustofluidic Microchannels Driven by Standing Lamb Waves

“…The Lamb-wave device was fabricated by a standard photolithographic technology, which is conventionally applied to the fabrication of SAW devices [34]. The used piezoelectric plate is a 128 • Y-X LiNbO 3 wafer with a thickness of 300 µm.…”