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Dielectrophoresis for capillary flow microfluidic optoelectronics

Giliyana, Dunia 2021. Dielectrophoresis for capillary flow microfluidic optoelectronics. PhD Thesis, Cardiff University.
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Abstract

The development of a novel photonic integrated platform with three dimensional (3D) capillary flow and dielectrophoresis elements for chip based flow cytometers is discussed. Size-independent single stream particle focusing is the key for the efficient operation of a flow cytometer and many efforts have been made to reproduce it properly on a microchip scale. In this work, capillary and negative Dielectrophoresis (n-DEP) components were integrated onto a single chip of III-V semiconductor material for conducting scattering measurements of microparticles. The integration of all components on a single chip is intended to result in low cost, portable and disposable microfluidic devices for point-of-care diagnostics. The design, fabrication and investigation of a system combining n-DEP with the capillary driven flow to align and reposition microparticles with fluid flow in a single stream around the centreline of the microchannel is considered. This is followed by testing the potential of n-DEP for efficient on-chip light scatter measurements. Planar microelectrodes face-to-face below and above the surface of the 3D microchannel are employed to create a localized non-uniform electric field to focus polystyrene microparticles in flowing fluid via n-DEP. The functionality of the device is assessed by detecting and counting 6 - 15 µm polystyrene microparticles (suspended in Deionised (DI) water) as an example to assess how similarly sized biological cells, such as blood cells, would flow within the fabricated 3D microchannel. The results show that the polystyrene microparticles are focused successfully in a single stream around the centreline of the 3D microchannel when operating the microelectrodes with an AC potential of 10 MHz and no more than 30 V peak-to-peak. The n-DEP focused microparticles show narrower velocity distribution, compared to randomly flowing particles, as well as exhibiting higher speeds (at the centre of the channel). The latter result suggests that a capillary-like speed profile is only present at the fluid front, and that the fluid flow becomes faster at the centre, behind the advancing meniscus, due to the greater friction at the microchannel’s side walls. Consistent pulse shapes and peaks are observed in the laser data from the similarly sized polystyrene microparticles using a fully-integrated platform with lasers and photo-detectors. This suggests that the n-DEP focusing microelectrodes can significantly improve the operation efficiency of the device by regulating the flow of microparticles and passing them through a consistent scanning zone albeit with an increase in the precision of the fabrication required.

Item Type: Thesis (PhD)
Date Type: Completion
Status: Unpublished
Schools: Physics and Astronomy
Subjects: Q Science > QC Physics
Uncontrolled Keywords: 3D capillary microfluidics, pump free microfluidics, Dielectrophoresis, DEP, DEP focusing force, n-DEP, SU-8 microfluidics, semiconductor lasers, cell sensing, III-V flow cytometer, chip scale flow cytometer, photonic integrated platform
Funders: Overseas government
Date of First Compliant Deposit: 28 October 2021
Last Modified: 28 Oct 2021 14:07
URI: http://orca.cardiff.ac.uk/id/eprint/145119

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