University of Twente Student Theses


Bead Separation using impedance spectroscopy and dielectrophoresis

Dekker, Stefan (2014) Bead Separation using impedance spectroscopy and dielectrophoresis.

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Abstract:The goal of this master project was to create and characterize a microfluidic system that is able to sort polystyrene beads based on their size. These beads had a size of 3 or 4 um. The microfluidic system is split up in four parts: differentiation, transport, separation and control. The differentiation of the beads was done with impedance measurements. An equivalent circuit model was developed predicting changes in impedance for a passing bead. Forces produced by dielectrophoresis (DEP) were used to separate the beads. To make the characterization of the different parts easier, several tools were developed. A Labview program on a pc connected to all equipment in the setup made synchronized data acquisition possible. Position data of the beads obtained out of the video could be linked to the impedance data with Matlab scripts. Characterization of the separate parts showed that the peak height of a peak in the impedance signal can be used to distinguish between 3 and 4 um beads. Focusing with DEP prior to impedance measurements improved the variance in the peak heights corresponding to a single bead size. Furthermore, the width of the peak was used to determine the speed of the bead. Experiments with DEP showed that the trajectory of the bead could be altered. Allowing effective focusing and sorting of beads in the microfluidic channel. Finally, the control part of the system links all separate function together in a Labview program. Experiments with this system showed that it is able to distinguish between the 3 and 4 um beads using impedance spectroscopy and sort accordingly using dielectrophoresis.
Item Type:Essay (Master)
Faculty:EEMCS: Electrical Engineering, Mathematics and Computer Science
Subject:53 electrotechnology
Programme:Electrical Engineering MSc (60353)
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