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Issue 15, 2017
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Modeling electrical double-layer effects for microfluidic impedance spectroscopy from 100 kHz to 110 GHz

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Abstract

Broadband microfluidic-based impedance spectroscopy can be used to characterize complex fluids, with applications in medical diagnostics and in chemical and pharmacological manufacturing. Many relevant fluids are ionic; during impedance measurements ions migrate to the electrodes, forming an electrical double-layer. Effects from the electrical double-layer dominate over, and reduce sensitivity to, the intrinsic impedance of the fluid below a characteristic frequency. Here we use calibrated measurements of saline solution in microfluidic coplanar waveguide devices at frequencies between 100 kHz and 110 GHz to directly measure the double-layer admittance for solutions of varying ionic conductivity. We successfully model the double-layer admittance using a combination of a Cole–Cole response with a constant phase element contribution. Our analysis yields a double-layer relaxation time that decreases linearly with solution conductivity, and allows for double-layer effects to be separated from the intrinsic fluid response and quantified for a wide range of conducting fluids.

Graphical abstract: Modeling electrical double-layer effects for microfluidic impedance spectroscopy from 100 kHz to 110 GHz

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Article information


Submitted
30 Mar 2017
Accepted
30 Jun 2017
First published
04 Jul 2017

Lab Chip, 2017,17, 2674-2681
Article type
Paper

Modeling electrical double-layer effects for microfluidic impedance spectroscopy from 100 kHz to 110 GHz

C. A. E. Little, N. D. Orloff, I. E. Hanemann, C. J. Long, V. M. Bright and J. C. Booth, Lab Chip, 2017, 17, 2674
DOI: 10.1039/C7LC00347A

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