Acoustothermal tweezer for droplet sorting in a disposable microfluidic chip

Abstract

Precise control over droplet position within a microchannel is fundamental to droplet microfluidic applications. This article proposes acoustothermal tweezer for the control of droplet position, which is based on thermocapillary droplet migration actuated by acoustothermal heating. The proposed system comprises an acoustothermal heater, which is composed of a slanted finger interdigital transducer patterned on a piezoelectric substrate and a thin PDMS membrane, and a PDMS microchannel. In the proposed system, droplets moving in a droplet microfluidic chip experience spatiotemporally varying thermal stimuli produced by acoustothermal heating and thus migrate laterally. In comparison to previous methods for droplet sorting, the acoustothermal tweezer offers significant advantages: first, the droplet position can be manipulated in two opposite directions, which enables bidirectional droplet sorting to one of three outlets downstream; second, precise control over the droplet position as well as improved droplet lateral displacement on the order of hundreds of micrometers can be achieved in a deterministic manner, thereby enabling multichannel droplet sorting; third, the PDMS microfluidic chip is disposable and thus can be easily replaced since it is attached to the substrate by reversible bonding, which allows the acoustothermal heater to be reused. Given these advantages, the proposed droplet sorting system is a promising droplet microfluidic lab-on-a-chip platform for tunable, on-demand droplet position control.

3D Manipulation and Imaging of Plant Cells using Acoustically Activated Microbubbles

“…The rotational velocity of the specimen can be manipulated by the voltage applied and the acoustic excitation frequency. Other factors that can contribute to the strength of the rotational manipulation include distance from the microchannel to the piezo‐transducer, size of the microbubbles, and attenuation of the acoustic waves in polydimethylsiloxane (PDMS)‐based microchannels.…”

Enhancement of plant leaf transpiration with effective use of surface acoustic waves: effect of wave frequency

“…27 Leaky SAWs generated heat energy through the oscillation of PDMS molecules, and the penetration depth (d) had a relationship with 0.7 power of the SAW frequency (d $ f À0.7 ). [27][28][29] The heating in the PDMS layer was rapid and fairly uniform in the excitation area. Acoustothermal heating was generated by viscoelastic damping aer acoustic waves were absorbed in viscoelastic materials like PDMS.…”

“…Depending on SAW frequency, the temperature distributions in the PDMS and the energy conversion efficiency in addition to the leaf transpiration are also varied. [27][28][29] The leaf transpiration rates were directly measured by weighting the transpiration-based water loss in the same plant leaves with varying SAW frequency. The relative intensity of the uptake dye solution in the plant leaf was also quantitatively analyzed.…”

Vertical Hydrodynamic Focusing and Continuous Acoustofluidic Separation of Particles via Upward Migration

“…Over the past few decades, microfluidic particle and cell separation techniques have played a vital role in cell biology, disease diagnostics, drug screening, drug discovery, and biochemical analysis 1, 2. To date, many researchers have explored various microfluidic methods for manipulating particles inside minute volumes of fluids, such as inertial microfluidics,3 hydrodynamic filtration,4 magnetophoresis,5 dielectrophoresis,6, 7 optofluidics,8, 9 and acoustophoresis 10, 11, 12, 13, 14, 15, 16. Acoustophoresis‐based microfluidic separation techniques are preferred due to the contactless handling of the biological samples, low power requirement, and biocompatible nature of the acoustic waves, all of which permit incorporation of acoustophoresis techniques into microscale total analysis systems.…”