Abstract
This paper describes the modeling and experimental verification of a castellated microelectrode array intended to handle biocells, based on common dielectrophoresis. The proposed microsystem was developed employing platinum electrodes deposited by lift-off, silicon micromachining, and photoresin patterning techniques. Having fabricated the microdevice it was tested employing Escherichia coli as bioparticle model. Positive dielectrophoresis could be verified with the selected cells for frequencies above 100 kHz, and electrohydrodynamic effects were observed as the dominant phenomena when working at lower frequencies. As a result, negative dielectrophoresis could not be observed because its occurrence overlaps with electrohydrodynamic effects; i.e. the viscous drag force acting on the particles is greater than the dielectrophoretic force at frequencies where negative dielectrophoresis should occur. The experiments illustrate the convenience of this kind of microdevices to micro handling biological objects, opening the possibility for using these microarrays with other bioparticles. Additionally, liquid motion as a result of electrohydrodynamic effects must be taken into account when designing bioparticle micromanipulators, and could be used as mechanism to clean the electrode surfaces, that is one of the most important problems related to this kind of devices.
Highlights
Handling of biological objects constitutes an important operation in many biotechnological processes such as biochemical assays, biocell detection and separation, cell fusion and gene manipulation (Hoettges et al 2003, Figeys and Pinto 2000, Lee and Tai 1999)
This paper describes the modeling and experimental verification of a castellated microelectrode array intended to handle biocells, based on common dielectrophoresis
Dielectrophoresis, DEP, is defined as the lateral motion imparted on uncharged particles as a result of polarization induced by non-uniform electric fields
Summary
Handling of biological objects constitutes an important operation in many biotechnological processes such as biochemical assays, biocell detection and separation, cell fusion and gene manipulation (Hoettges et al 2003, Figeys and Pinto 2000, Lee and Tai 1999). Diverse non-contact techniques have been proposed using electric, magnetic, ultrasonic and optical forces as the actuation mechanism to handle and characterize biological cells (Choi et al 1999, Fuhr et al 1998a, Porras et al 2004). Among these alternatives, electrostatic fields are the most suitable for miniaturization because they do not have mechanical moving parts, and only a few electrodes have to be fabricated (Fuhr and Shirley 1998).
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