Plug-and-play acoustic tweezer enables droplet centrifugation on silicon superstrate with surface multi-layered microstructures

Acoustofluidic localization of sparse particles on a piezoelectric resonant sensor for nanogram-scale mass measurements

“…To realize sessile droplet microcentrifugation to localize scattered particles at the center of the droplet (where the MEMS resonator is located), a spatially asymmetric acoustic field is generated on the SAW transducer (substrate) and coupled into the MEMS chip (superstrate). Three methods for generating asymmetric fields have been reported, the use of f-IDTs in SAW transducer design 19 , the employment of a frequency selective phononic crystal etched into a superstrate 18 , and the use of nonfrequency selective periodic structures patterned in a superstrate 27 . For simplicity of implementation, f-IDTs are utilized in this work.…”

“…The backside cavity and surface multilayers on the MEMS resonator chip have little effect on the effectiveness of the acoustic localization of particles in a droplet (see S1 of the Supplementary information). The generated acoustic streaming force provides a rotational force component, while the acoustic radiation force provides a radial component that pushes the particles to the center of the droplet 19 .…”

“…While there are many reports on using acoustic waves to manipulate the particles in a sessile droplet on bare superstrates 19 or even superstrates with multilayered surface thin films 22 , the efficacy of acoustic microcentrifugation on a superstrate with a through-wafer back cavity has yet to be tested. As such, we investigate the particle localization performance in a water droplet on a MEMS chip with a TPoS resonant sensor using PS microbeads with different diameters.…”

“…Yannyk et al employed SAWs to realize rare-cell enrichment and separation in a fingerpick-sized drop of blood 18 . We have previously reported a plug-and-play acoustofluidic device for droplet microcentrifugation that enables particle focusing and isolation on a surface-micromachined silicon (SMS) chip 19 . Such a proposed dual-chip strategy facilitates the reusability of the SAW device while retaining the benefits of acoustofluidic methods and is applicable to various microparticles with diverse densities and sizes 20 .…”

A rapid and controllable acoustothermal microheater using thin film surface acoustic waves

“…Recently surface acoustic waves (SAWs) have also been explored for microfluidic heating due to their significantly acoustothermal heating effects [17][18][19][20]. In comparison with the above methods, SAW heating technologies have obvious advantages such as low cost, low power consumption, miniaturization and easy implementation [21,22].…”