Rapid Enrichment of Submicron Particles within a Spinning Droplet Driven by a Unidirectional Acoustic Transducer

Abstract

Efficient and rapid particle enrichment at the submicron scale is essential for research in biomedicine and biochemistry. Here, we demonstrate an acoustofluidic method for submicron particle enrichment within a spinning droplet driven by a unidirectional transducer. The unidirectional transducer generates intense sound energy with relatively low attenuation. Droplets placed offset in the wave propagation path on a polydimethylsiloxane film undergo strong pressure gradients, deforming into an ellipsoid shape and spinning at high speed. Benefitting from the drag force induced by the droplet spin and acoustic streaming and the radial force induced by the droplet compression and expansion, the submicron particles in the liquid droplet quickly enrich toward the central area following a spiral trajectory. Through numerical calculations and experimental processes, we have demonstrated the possible mechanism responsible for particle enrichment. The application of biological sample processing has also been exploited. This study anticipates that the strategy based on the spinning droplet and particle enrichment method will be highly desirable for many applications.

Controllable high-performance liquid marble micromixer

“…Previous studies showed that these forces produce observable spiral flow patterns around the spin axis which are expected. 57,[62][63][64] In this work, a spinning liquid marble is achieved by placing it at the centre of a spinning cup where the rotational speeds of both the liquid marble and cup are synchronous. When a liquid marble spins from rest, it flattens slightly due to centrifugal forces.…”

Concentration of Microparticles Using Flexural Acoustic Wave in Sessile Droplets

“…Particle concentration at the microscale is of great significance in various biomedical and biochemical applications, including micro/nano-assembly [ 1 , 2 ], tissue engineering [ 3 , 4 ], and biomedical detection [ 5 ]. The concentration process is usually a crucial sample preparation step in related biomedical applications such as biosensors [ 6 ], and 3D cell culture [ 7 ]. Microparticle concentration realized by efficient fluidic methods has become an important research area.…”

“…With acoustic wave actuation, precise and efficient particle manipulation from nanometer to micron scale can be achieved based on the induced acoustic radiation force and acoustic streaming [ 17 ]. Existing methods for acoustic concentration mainly include surface acoustic wave (SAW) [ 6 , 18 , 19 ], and flexural wave [ 12 , 20 , 21 ] vary with the used transducer. According to the analytical equation f = c / λ , SAW with the required resonant frequency f and specific type can be generated by fabricating interdigital electrodes (IDTs) with specific finger width on the substrate such as 128° YX Lithium Niobate [ 22 , 23 ].…”

“…For straight IDTs, four different regimes of particle concentration can be identified depending on the sessile droplet diameter [ 11 ]. Our group [ 6 ] has developed an acoustofluidic chip based on unidirectional surface acoustic wave centrifugation in droplets, which can quickly enrich the sub-micron particles.…”

Effect of viscosity on surface acoustic wave driven collective particle dynamics in sessile droplets: nebula, black holes and white dwarfs

“…Particles contactless manipulation such as concentration, aggregation and separation in microfluidics is previously considered to be the result of the combined action of the two forces: acoustic radiation force (F Gov kov ), acoustic streaming drag force (F D ) or tea leaf effect [1][2][3]. However, it is unlikely to be due to the radiation force because similar phenomena can be observed without acoustic field, which can reference the study of Yeo et al [4].…”