Electrohydrodynamic Scaling Laws Analysis in a Microfluidic Isodep Device

Electrohydrodynamic scaling laws analysis in a microfluidic IsoDEP device

M.Z. Rashed¹, K.C. Grome¹, S.P. Hendricks², S.J. Williams¹

1. University of Louisville, Louisville, Kentucky USA

2. Murray State University, Murray, Kentucky USA

Dielectrophoresis (DEP) is the phenomenon in which a particle, such as a living cell, is moved by the interaction between a non-uniform electric field and its induced polarization. Isomotive dielectrophoresis (isoDEP) is a cell analysis and characterization technique that uniquely utilizes a constant gradient field-squared (∇Erms2)  resulting in a uniform DEP force. The resultant constant (isomotive) particle translational velocity that can be tracked using particle tracking velocimetry (PIV) software to extract the cell/particle dielectric properties. Inspired by initial analysis by Herbert Pohl, we have developed modified electrode geometry for isoDEP. Fabrication of extruded electrodes is straightforward via microfabrication methods (DRIE of conductive wafers) or sub-millimeter machining. A sample is injected and flow is halted before field activation. Digital images will extract particle size and, due a constant ∇Erms2 , the only unknown for each particle is Re[f_CM] The field is applied and Re[f_CM] is extracted through particle tracking. The particle’s velocity will change as the AC frequency is swept over a specified range to obtain a comprehensive Re[f_CM]  spectrum. Through simultaneous particle tracking such spectra are obtained for every particle in the imaging area, enabling parallel analysis of cells. IsoDEP can extract the dielectric properties of each cell (ex: membrane capacitance) – these properties directly correlate to the cell physiology. Any unwanted flow will disrupt the trajectory of the particles and compromise their analysis. To that end, we have conducted an electrohydrodynamic study and scaling law analysis to reduce electrothermal hydrodynamics in an isoDEP device. Numerical simulations (COMSOL Multiphysics) are in good agreement with experimental measurements via micro-PIV. In addition to experimental results, current and future IsoDEP platform designs will be shared.

References

[1] H.A. Pohl, Dielectrophoresis: The Behavior of Neutral Matter in Nonuniform Electric Fields, Cambridge; New York: Cambridge University Press (1978).

[2] Allen, D. J., Accolla, R. P. and Williams, S. J. (2017), Isomotive dielectrophoresis for parallel analysis of individual particles. ELECTROPHORESIS. doi:10.1002/elps.201600517.