Abstract
The manipulation of biological cells and micrometer-scale particles using dielectrophoresis (DEP) is an indispensable technique for lab-on-a-chip systems for many biological and colloidal science applications. However, existing models, including the dipole model and numerical simulations based on Maxwell stress tensor (MST), cannot achieve high accuracy and high computation efficiency at the same time. The dipole model is widely used and provides adequate predictions on the crossover frequency of submicron particles, but cannot predict the crossover frequency for larger particles accurately; on the other hand, the MST method offers high accuracy for a wide variety of particle sizes and shapes, but is time-consuming and may lack predictive understanding of the interplay between key parameters. Here we present a mathematical model, using dimensional analysis and the Buckingham pi theorem, that permits high accuracy and efficiency in predicting the crossover frequency of spherical particles. The curve fitting and calculation are performed using commercial packages OriginLab and MATLAB, respectively. In addition, through this model we also can predict the conditions in which no crossover frequency exists. Also, we propose a pair of dimensionless parameters, forming a functional relation, that provide physical insights into the dependency of the crossover frequency on five key parameters. The model is verified under several scenarios using comprehensive MST simulations by COMSOL Multiphysics software (COMSOL, Inc.) and some published experimental data.
Highlights
If we apply a spatially nonuniform electric field to an uncharged dielectric particle suspended in a medium of different electrical properties, the particle is subjected to a force by the electric field due to the difference in polarizability between the particle and the medium
When we only change the particle size and fix other parameters, the obtained equation predicts that the crossover frequency always exists regardless of the particle size. It predicts that the crossover frequency always exists regardless of the medium conductivity. Those predictions contradict the experimental observation and Maxwell stress tensor (MST) simulations, which show that the crossover frequency does not exist for very large particles, nor for high conductive media
We find that the solution does not exist if the particle size or medium conductivity is greater than a certain value
Summary
If we apply a spatially nonuniform electric field to an uncharged dielectric particle suspended in a medium of different electrical properties, the particle is subjected to a force by the electric field due to the difference in polarizability between the particle and the medium. Basurays et al.[14] reported explicit expressions, by a simple scaling analysis, to describe three different conductive mechanisms These expressions predict that a crossover frequency always exists regardless of the particle size and solution conductivity, which is not consistent with experimental observations.[9]. Dimensional analysis and in particular the Buckingham pi theorem have proven a powerful method for solving complex physical problems over the past century.[15] Buckingham pi theorem provides a systematical procedure for constructing physically meaningful dimensionless parameters from given variables, even if their functional relation is unknown, and has been widely used in different engineering fields. We verify the model by a broad range of numerical simulations using the MST method[10] as well as published experimental results from the literature.[7,8,9]
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
