Issue 5, 2004
From the journal:

Lab on a Chip

Capacitive sensing of droplets for microfluidic devices based on thermocapillary actuation

Jian Z. Chen,a   Anton A. Darhuber,b   Sandra M. Troian*b  and  Sigurd Wagnera  

* Corresponding authors

a Department of Electrical Engineering, Department of Chemical Engineering, Princeton University, Princeton, NJ 08544, USA

b Microfluidic Research & Engineering Laboratory, Department of Chemical Engineering, Princeton University, Princeton, NJ 08544, USA
E-mail: stroian@princeton.edu

Abstract

The design and performance of a miniaturized coplanar capacitive sensor is presented whose electrode arrays can also function as resistive microheaters for thermocapillary actuation of liquid films and droplets. Optimal compromise between large capacitive signal and high spatial resolution is obtained for electrode widths comparable to the liquid film thickness measured, in agreement with supporting numerical simulations which include mutual capacitance effects. An interdigitated, variable width design, allowing for wider central electrodes, increases the capacitive signal for liquid structures with non-uniform height profiles. The capacitive resolution and time response of the current design is approximately 0.03 pF and 10 ms, respectively, which makes possible a number of sensing functions for nanoliter droplets. These include detection of droplet position, size, composition or percentage water uptake for hygroscopic liquids. Its rapid response time allows measurements of the rate of mass loss in evaporating droplets.

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Article information

DOI
https://doi.org/10.1039/B315815B
Article type
Paper
Submitted
05 Dec 2003
Accepted
04 May 2004
First published
25 Jun 2004

Lab Chip, 2004,4, 473-480

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Capacitive sensing of droplets for microfluidic devices based on thermocapillary actuation

J. Z. Chen, A. A. Darhuber, S. M. Troian and S. Wagner, Lab Chip, 2004, 4, 473 DOI: 10.1039/B315815B

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