A simple approach for the fabrication of 3D microelectrodes for impedimetric sensing

Date
2015
Authors
Guler, M. T.
Bilican, I.
Agan, S.
Elbuken, C.
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Instructor
Source Title
Journal of Micromechanics and Microengineering
Print ISSN
0960-1317
Electronic ISSN
Publisher
Institute of Physics Publishing
Volume
25
Issue
9
Pages
95019 - 095019-11
Language
English
Type
Article
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Abstract

In this paper, we present a very simple method to fabricate three-dimensional (3D) microelectrodes integrated with microfluidic devices. We form the electrodes by etching a microwire placed across a microchannel. For precise control of the electrode spacing, we employ a hydrodynamic focusing microfluidic device and control the width of the etching solution stream. The focused widths of the etchant solution and the etching time determine the gap formed between the electrodes. Using the same microfluidic device, we can fabricate integrated 3D electrodes with different electrode gaps. We have demonstrated the functionality of these electrodes using an impedimetric particle counting setup. Using 3D microelectrodes with a diameter of 25 μm, we have detected 6 μm-diameter polystyrene beads in a buffer solution as well as erythrocytes in a PBS solution. We study the effect of electrode spacing on the signal-to-noise ratio of the impedance signal and we demonstrate that the smaller the electrode spacing the higher the signal obtained from a single microparticle. The sample stream is introduced to the system using the same hydrodynamic focusing device, which ensures the alignment of the sample in between the electrodes. Utilising a 3D hydrodynamic focusing approach, we force all the particles to go through the sensing region of the electrodes. This fabrication scheme not only provides a very low-cost and easy method for rapid prototyping, but which can also be used for applications requiring 3D electric field focused through a narrow section of the microchannel.

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Keywords
3D microelectrodes, Flow-focusing, Microfabrication, Microfluidic electrical sensing, Particle counting, Electric fields, Etching, Fluid dynamics, Fluidic devices, Focusing, Hydrodynamics, Microchannels, Microelectrodes, Microfabrication, Microfluidics, Radiation counters, Signal to noise ratio, Electrical sensing, Electrode spacing, Etching solutions, Flow focusing, Hydrodynamic focusing, Micro-fluidic devices, Particle counting, Threedimensional (3-d), Electrodes
Citation
Published Version (Please cite this version)