Fully Microfabricated Surface Acoustic Wave Tweezer for Collection of Submicron Particles and Human Blood Cells

Abstract

Precise manipulation of (sub)micron particles is key for the preparation, enrichment, and quality control in many biomedical applications. Surface acoustic waves (SAW) hold tremendous promise for manipulation of (bio)particles at the micron to nanoscale ranges. In commonly used SAW tweezers, particle manipulation relies on the direct acoustic radiation effect whose superior performance fades rapidly when progressing from micron to nanoscale particles due to the increasing dominance of a second order mechanism, termed acoustic streaming. Through reproducible and high-precision realization of stiff microchannels to reliably actuate the microchannel cross-section, here we introduce an approach that allows the otherwise competing acoustic streaming to complement the acoustic radiation effect. The synergetic effect of both mechanisms markedly enhances the manipulation of nanoparticles, down to 200 nm particles, even at relatively large wavelength (300 μm). Besides spherical particles ranging from 0.1 to 3 μm, we show collections of cells mixed with different sizes and shapes inherently existing in blood including erythrocytes, leukocytes, and thrombocytes.

Nano/Micromotors for Cancer Diagnosis and Therapy: Innovative Designs to Improve Biocompatibility

“…Both surface acoustic waves (SAWs) and ultrasonic standing waves (USWs) can be used for nano/micromotor manipulation. SAWs usually use piezoelectric ceramics (such as lithium niobate, LiNbO3) as the substrate with interdigital transducers (IDTs) on the surface (Figure 3A,B) [70,71], and for USWs, researchers tend to carry out nano/micromotor propulsion in a tailor-made chamber (made from Kapton tape or PDMS) for ultrasound wave reflection and piezoelectric ceramics stuck to the chamber for ultrasound wave generation (Figure 3C,D) [72,73]. Wang et al synthesized nanomotors using gold nanowires (AuNWs) modified with ovalbumin (OVA), which act as model protein antigen.…”

“…These ultrasound-powered nanomotors help in the process of antigen cross presentation and cellular immunity (with upregulation of MHC I and MHC II-related molecule expression), which are critical components of the immunological effect of therapeutic vaccines for tumors or viral diseases [74]. Cao et al synthesized mesoporous manganese oxide (MnOx) using a water/oil emulsion reaction at room temperature, followed by the loading of indocyanine green derivatives (IDs) [70] with permission, copyright American Chemical Society, Washington, DC, USA, 2023. (B) Schematic illustration showing surface acoustic wave tweezer to remove molecules unbound to micromotors, thus lowering detection limit of cancer-related biomarker miRNA-21.…”

“…( A ) Schematic illustration showing surface acoustic wave tweezer for collection of submicron particles and human blood cells. Adapted from [ 70 ] with permission, copyright American Chemical Society, Washington, DC, USA, 2023. ( B ) Schematic illustration showing surface acoustic wave tweezer to remove molecules unbound to micromotors, thus lowering detection limit of cancer-related biomarker miRNA-21.…”

Surface Acoustic Wave-Based Microfluidic Device for Microparticles Manipulation: Effects of Microchannel Elasticity on the Device Performance

“…A 2D numerical model of the cross-section of the complete device is considered. 2D models of SSAW devices have been widely reported to study the acoustophoretic phenomenon [ 37 ], to investigate the microchannel behavior [ 45 ], and to compare the performance of hard wall channels with respect to soft wall ones [ 46 ]. Here, a study on the sensitivity of the standing pressure field to variations in the thickness and width of a soft PDMS microchannel cavity is performed as a preliminary step before the fabrication of the device.…”

“…Ni et al [ 45 ] already reported different approaches for PDMS modeling in acoustofluidic devices; their analysis highlighted that the modeling of PDMS as an elastic (solid) continuum, supporting the propagation of shear waves, causes specific acoustic streaming effects at the fluid/PDMS interface boundary layer, so that the acoustofluidic problem can be approached more accurately. Considering particles below a certain dimension (typically submicron sized [ 46 ]), the acoustic streaming force has a greater effect on particle manipulation with respect to ARF. In our analyses, due to the considered micrometric size of polystyrene (PS) spherical microbeads, results in terms of their focusing towards the pressure nodes by the acoustic radiation are reported, while the effect of the acoustic streaming is neglected.…”