Two-dimensional acoustic particle focusing enables sheathless chip Coulter counter with planar electrode configuration

Abstract

The field of cytometry has grown in scope and importance ever since the early 20th century with leaps in technology introducing the Coulter counter and the flow cytometer. Cytometry methods have brought about a revolution for the medical and biotechnology industry by providing fast and accurate analysis of cell and particle suspensions. Recent developments in the field aim at improving current cytometers and to provide miniaturized low-cost cytometry systems for point-of-care clinical diagnostics or research. In an attempt to address the need for particle positioning which is important for both impedance and optically based cytometers we present a microfluidic system which precisely positions cells and particles, using acoustic forces and subsequently performs measurements using an integrated and simple planar electrode Coulter-type impedance cytometer without the need for sheath flows. Data is presented to show how the acoustic method improves the accuracy of the impedance cytometer when prefocusing is employed to particles and cells (diluted whole blood). Confocal imaging and simulations support the findings and provide the basis for further improvements. The acoustophoretic prefocusing technique opens a path towards small, low cost cytometers while also providing an easy way to improve current systems.

High accuracy particle analysis using sheathless microfluidic impedance cytometry

“…Externally applied forces can also be used to focus particles within the fluid. For example dielectrophoresis 6,23 (DEP) and acoustophoresis 24 have been used to focus particles without the use of a secondary flow. Other novel approaches include combining DEP and inertial microfluidics 25 .…”

A new method for determining the aspect ratio of kaolinite by image-resistance combination

“…Resistance method is the only threedimensional test method for particle size and has high accuracy and repeatability. For these reasons, this method is widely applied in various industries, especially the medical industry [10,11].…”

Fabrication and Operation of Acoustofluidic Devices Supporting Bulk Acoustic Standing Waves for Sheathless Focusing of Particles

“…29 An additional advantage is that acoustic devices can focus particles across a wide range of applied flow rates and independent of the flow direction, which is not possible in devices that rely on inertial forces for focusing, 28 providing the means to efficiently transport particles or cells for enhanced particle inspection for applications such as flow cytometry and particle sizing. 30,31 The ease of device fabrication and operation can directly allow for the implementation of similar devices for focusing, concentrating, fractionating and sorting objects suspended in fluids. 32 We have shown that the primary radiation forces, which are the strongest forces produced by acoustic standing waves, 1 can focus microparticles flowing through a microfluidic channel at flow rates exceeding 10 ml/hr for a single orifice design.…”