Acoustic Tweezing and Patterning of Concentration Fields in Microfluidics

@article{Karlsen2017AcousticTA,
  title={Acoustic Tweezing and Patterning of Concentration Fields in Microfluidics},
  author={Jonas Karlsen and Henrik Bruus},
  journal={Physical review applied},
  year={2017},
  volume={7},
  pages={034017}
}
We demonstrate theoretically that acoustic forces acting on inhomogeneous fluids can be used to pattern and manipulate solute concentration fields into spatio-temporally controllable configurations stabilized against gravity. A theoretical framework describing the dynamics of concentration fields that weakly perturb the fluid density and speed of sound is presented and applied to study manipulation of concentration fields in rectangular-channel acoustic eigenmodes and in Bessel-function… 

Figures from this paper

Two-Dimensional Mapping Separating the Acoustic Radiation Force and Streaming in Microfluidics
In microscale fluids, fields of physical force and streaming play central roles in manipulating and tweezing objects, but it is difficult to disentangle and obtain accurate pictures of them. We
Acoustic tweezing of microparticles in microchannels with sinusoidal cross sections
TLDR
Simulation results in this paper show that efficient particle trapping occurs at the intermediate sinusoidal boundary amplitudes, and indicated that in a square-sinusoidal geometry there are two strong vortices, instead of one vortex, which means sub-micrometer particles tend to be trapped dramatically faster in such a geometry than in the rectangular-Sinusoidal ones.
Experimental Characterization of Acoustic Streaming in Gradients of Density and Compressibility
Suppression of boundary-driven Rayleigh streaming has recently been demonstrated for fluids of spatial inhomogeneity in density and compressibility owing to the competition between the
Numerical study of the effect of channel aspect ratio on particle focusing in acoustophoretic devices
TLDR
This study numerically study the well-known rectangular cross section of a microfluidic channel and performs a parametric study of the aspect ratio for several particle sizes to investigate and understand which geometrical parameters could be changed to limit the acoustic streaming effect.
Numerical study of acoustic cell trapping above elastic membrane disks driven in higher-harmonic modes by thin-film transducers with patterned electrodes
Excitations of MHz acoustic modes are studied numerically in 10-μm-thick silicon disk membranes with a radius of 100 and 500 μm actuated by an attached 1-μm-thick (AlSc)N thin-film transducer. It is
Rapid mixing in microchannel using standing bulk acoustic waves
We present a technique for mixing the fluids in a microchannel using ultrasonic waves. Acoustic mixing is driven by the acoustic body force, which depends on the density gradient and speed of the
Acoustic Streaming and Its Suppression in Inhomogeneous Fluids.
TLDR
It is shown that in an inhomogeneous fluid, an additional nondissipative force density acts on the fluid to stabilize particular inhomogeneity configurations, which markedly alters and even suppresses the streaming flows.
Theory of pressure acoustics with thermoviscous boundary layers and streaming in elastic cavities.
TLDR
The effective model allows for numerical simulation of both thermoviscous acoustic and time-averaged fields in three-dimensional models of acoustofluidic systems and shows how the acoustic streaming depends strongly on steady and oscillating thermal fields through the temperature dependency of the material parameters.
Theory of nonlinear acoustic forces acting on inhomogeneous fluids
Abstract Recently, the phenomena of streaming suppression and relocation of inhomogeneous miscible fluids under acoustic fields were explained using the hypothesis on mean Eulerian pressure. In this
Theoretical aspects of microscale acoustofluidics
TLDR
Henrik Bruus summarizes some of the recent results within theory and simulation of microscale acoustofluidic systems that he has obtained in collaboration with his students and international colleagues, focusing on three dynamical effects induced by external ultrasound fields acting on aqueous solutions and particle suspensions.
...
...

References

SHOWING 1-10 OF 74 REFERENCES
Fast acoustic tweezers for the two-dimensional manipulation of individual particles in microfluidic channels
This paper presents a microfluidic device that implements standing surface acoustic waves in order to handle single cells, droplets, and generally particles. The particles are moved in a very
Observation of a Single-Beam Gradient Force Acoustical Trap for Elastic Particles: Acoustical Tweezers.
TLDR
The trapping of elastic particles by the large gradient force of a single acoustical beam in three dimensions is demonstrated, demonstrating the large spectrum of frequencies covered by coherent ultrasonic sources and could open the way to important applications in biology and biophysics at the cellular scale and for the design of acoustic machines in microfluidic environments.
Imaging the position-dependent 3D force on microbeads subjected to acoustic radiation forces and streaming.
TLDR
This method to image acoustically generated forces in 3D can be used to either minimize perpendicular forces or to employ them for specific applications in novel acoustofluidic designs.
Acoustic Force Density Acting on Inhomogeneous Fluids in Acoustic Fields.
TLDR
The theory predicts a relocation of the inhomogeneities into stable field-dependent configurations, which are qualitatively different from the horizontally layered configurations due to gravity for microfluidic systems.
Independent trapping and manipulation of microparticles using dexterous acoustic tweezers
An electronically controlled acoustic tweezer was used to demonstrate two acoustic manipulation phenomena: superposition of Bessel functions to allow independent manipulation of multiple particles
Dexterous manipulation of microparticles using Bessel-function acoustic pressure fields
We show that Bessel-function acoustic pressure fields can be used to trap and controllably position microparticles. A circular, 16-element ultrasound array generates and manipulates an acoustic field
Acoustic radiation forces at liquid interfaces impact the performance of acoustophoresis.
TLDR
It is reported that flow laminated liquids can be relocated in a microchannel when exposed to a resonant acoustic field and it is demonstrated that acoustic relocation of liquids occurs for impedance differences as low as 0.1%.
Anisotropic Swirling Surface Acoustic Waves from Inverse Filtering for On-Chip Generation of Acoustic Vortices
Acoustic tweezers allow for contactless manipulation of tiny objects, such as cells or droplets. The cornerstone of current technology is a corkscrewlike acoustic vortex, typically generated using
Numerical study of thermoviscous effects in ultrasound-induced acoustic streaming in microchannels.
  • P. Muller, H. Bruus
  • Physics
    Physical review. E, Statistical, nonlinear, and soft matter physics
  • 2014
TLDR
A numerical study of thermoviscous effects on the acoustic streaming flow generated by an ultrasound standing-wave resonance in a long straight microfluidic channel containing a Newtonian fluid finds that even for thin acoustic boundary layers, the channel height affects the magnitude of the streaming flow.
Ultrasound-induced acoustophoretic motion of microparticles in three dimensions.
TLDR
Analytical expressions for the three-dimensional (3D) acoustophoretic motion of spherical microparticles in rectangular microchannels are derived, allowing for quantitative comparison between theoretical predictions and measurements of the streaming-induced motion of small 0.5-μm-diameter particles.
...
...