Miniature Electrical Tomography for Micro­Fluidic Systems

Sung Quek1, Stephan Mohr2, Nick Goddard2, Peter Fielden2 and Trevor York1

1School of Electrical and Electronic Engineering, University of Manchester, UK

2School of Chemical Engineering and Analytical Science, University of Manchester, UK

ABSTRACT

The paper describes the design, implementation and testing of a miniature electrical capacitance tomograph for imaging flow in microfluidic channels. This has been motivated by the desire to inform improved design and operation of microfluidic systems which in turn promises improved quality, reliability and processing time. An electrical capacitance tomograph based on the Analog Devices AD7745 capacitance to digital converter and ADG1206 multiplexer is described. The design has been informed by modelling results of the electric field due to an array of 12 electrodes surrounding a rectangular channel of cross­section 1200μm x 1200μm. Using 12 electrodes, each measuring 1200μm x 300μm, capacitance changes of the order of femtofarads are obtained. These reveal sub femto­farad noise for rates up to 90 measurement conversions per second. Preliminary capacitance measurements in the micro­fluidic sensor are presented.

Keywords Miniature electrical capacitance tomography, micro­fluidics, finite integration technique