Enriching Nanoparticles via Acoustofluidics

Abstract

Focusing and enriching submicrometer and nanometer scale objects is of great importance for many applications in biology, chemistry, engineering, and medicine. Here, we present an acoustofluidic chip that can generate single vortex acoustic streaming inside a glass capillary through using low-power acoustic waves (only 5 V is required). The single vortex acoustic streaming that is generated, in conjunction with the acoustic radiation force, is able to enrich submicrometer- and nanometersized particles in a small volume. Numerical simulations were used to elucidate the mechanism of the single vortex formation and were verified experimentally, demonstrating the focusing of silica and polystyrene particles ranging in diameter from 80 to 500 nm. Moreover, the acoustofluidic chip was used to conduct an immunoassay in which nanoparticles that captured fluorescently labeled biomarkers were concentrated to enhance the emitted signal. With its advantages in simplicity, functionality, and power consumption, the acoustofluidic chip we present here is promising for many point-of-care applications.

Surface acoustic wave devices for chemical sensing and microfluidics: a review and perspective

“…, streptavidin) made for an integrated concentration/detection strategy. 179 Along those lines, Westerhausen used a microchannel mixing strategy to synthesize mono-nucleic acid/lipid particles (mNALPs) by mixing separate liquid streams of lipids and nucleic acids in what amounted to a solvent exchange process. 180 …”

On‐Chip Generation of Vortical Flows for Microfluidic Centrifugation

“…If the microchannel dimension is smaller than λ f , there is insufficient length over which the sound wave in the liquid propagates and hence attenuates, and unidirectional flow—useful for micropumping applications—ensues, albeit with the possibility for the generation of localized vortices confined within the boundary layer due to Schlichting and Rayleigh streaming . On the other hand, microchannel dimensions greater than λ f allows Eckart streaming vortices to be sustained, both longitudinally ( Figure ), as well as transverse to the main flow direction in the channel …”

“…In addition to demonstrating the microvortical flow arising from these devices for various applications, including hydrodynamic particle trapping, biomolecular concentration and the shearing of polyelectrolyte films for drug release, the piezoelectric films can be overlaid onto regular substrates so as to circumvent the need for the piezoelectric substrate as well as to facilitate microfluidic operations on flexible substrates . To however separate the actuator from the microfluidic components, so as to enable reuse of the actuator (i.e., the piezoelectric chip) while facilitating a disposable option for the microfluidic chip, it is necessary to transmit the SAW vibration through a liquid couplant into a superstrate (e.g., a low‐cost and hence disposable chip on which the microfluidic operations are to be carried out as opposed to the reusable higher‐cost piezoelectric substrate to drive the microfluidic actuation), as first shown by Hodgson et al, or even a capillary tube . In place of the superstrate, a phononic crystal can also be used, wherein it was shown that introducing a defect allows the creation of a bandgap that permits symmetry breaking of the vibration in the phononic crystal so as to drive the azimuthal microfluidic centrifugation flow on the crystal superstrate in a similar way to the strategies shown in Figure b for generating asymmetric SAWs .…”

“…• Sessile droplet: azimuthal flow via symmetry breaking [118][119][120][121][122][123][124][125][126] • Microchannel -Standing waves: local recirculation [127] -Travelling waves; longitudinal [128] -Travelling waves; transverse [128] -Vortex beam [129][130][131] • Indirect coupling -Superstrate [132,133] -Phononic crystal [134,135] -Capillary tube [136] -Lab-on-a-disc [137,138] Hybrid bulk and vibration (coupling into microarray titer plate) [139,140] Relatively rapid and intense centrifugation flows can be generated Acoustic field intensity can be tuned to control vortex characteristics and strength [141,142] • Substrate energy gradients [141,142] Surface shear…”

Progress in Microfluidics‐Based Exosome Separation and Detection Technologies for Diagnostic Applications

“…As a technology, microfluidics offers many advantages, such as very small consumption of samples and reagents, high resolution and sensitivity, low cost, and significant reduction in assay time . Because of these advantages, microfluidics has been successfully applied in the biomedical field, for example, in particle separation, cell separation, DNA/RNA manipulation, polymerase chain reaction (PCR), detection of circulating tumor cells (CTCs) and droplet generation . In recent years, increasing attention has been paid to the development of new exosome separation and detection techniques based on microfluidics .…”