Individual Microparticle Manipulation Using Combined Electroosmosis and Dielectrophoresis through a Si3N4 Film with a Single Micropore.

Chenang Lyu,Xing Li,Leo Lou,Gideon Ukpai,Boris Rubinsky,Matthew J Powell-Palm

doi:10.3390/mi12121578

Abstract

Porous dielectric membranes that perform insulator-based dielectrophoresis or electroosmotic pumping are commonly used in microchip technologies. However, there are few fundamental studies on the electrokinetic flow patterns of single microparticles around a single micropore in a thin dielectric film. Such a study would provide fundamental insights into the electrokinetic phenomena around a micropore, with practical applications regarding the manipulation of single cells and microparticles by focused electric fields. We have fabricated a device around a silicon nitride film with a single micropore (2–4 µm in diameter) which has the ability to locally focus electric fields on the micropore. Single microscale polystyrene beads were used to study the electrokinetic flow patterns. A mathematical model was developed to support the experimental study and evaluate the electric field distribution, fluid motion, and bead trajectories. Good agreement was found between the mathematic model and the experimental data. We show that the combination of electroosmotic flow and dielectrophoretic force induced by direct current through a single micropore can be used to trap, agglomerate, and repel microparticles around a single micropore without an external pump. The scale of our system is practically relevant for the manipulation of single mammalian cells, and we anticipate that our single-micropore approach will be directly employable in applications ranging from fundamental single cell analyses to high-precision single cell electroporation or cell fusion.

Highlights

The ability to precisely manipulate single microparticles and cells is important in many micro- and nano- scale fluidic devices [1,2,3]
Our experiments demonstrate that the combination of electroosmotic flow and DEP forces induced by direct current has significant potential as a means to trap, agglomerate, repel, and rotate the beads without an external pump
The scale of our system is practically relevant for the manipulation of single mammalian cells, and we anticipate that our single-micropore approach will be directly employable in applications ranging from fundamental single-cell analyses, to high-precision single cell electroporation, or cell fusion

Summary

Introduction

The ability to precisely manipulate single microparticles and cells is important in many micro- and nano- scale fluidic devices [1,2,3]. EO is induced by ionic cloud migration in response to electric fields that are applied tangentially to an electrode surface [7]. Electroosmotic micropumps (EOP) can create constant pulse-free flows in low Reynolds number flow (in which a traditional external pump system may work inefficiently) without the requirement of moving parts [4]. The flow rates and pumping pressure of EOPs have a quick and precise response to electric input, making the suitable for use with microanalysis systems [6]. DEP occurs when a polarizable particle is suspended in a spatially nonuniform electric field [8]. If the particle moves in the direction of an increasing electric field, the behavior

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