Date of Award

11-2010

Degree Type

Thesis

Degree Name

Master of Applied Science (MASc)

Department

Mechanical Engineering

Supervisor

P. R. Selvaganapathy

Co-Supervisor

M. J. Deen

Language

English

Abstract

Biosensors, used in medical diagnostics, increasingly use genomic information (DNA) to rapidly and accurately determine the species present in the sample. Since, the DNA inherently has a negative charge, electrical methods provide a direct technique to sense it. This transduction has been achieved by using a biological Field-Effect-Transistor (BioFET) structure, where hybridization of a single stranded DNA (indicative of the biological species) with a complementary strand from the sample solution causes a change in the transistor characteristics that could be read out electrically. The accuracy of sensing using the BioFET is critically dependent on imposition of a highly stable potential which is performed using a reference electrode.

Design and fabrication of a miniaturized silver/silver chloride (Ag/AgCI) reference electrode is introduced in this thesis for use in BioFET. The electrode consists of Ag/AgCl wire which is embedded into a PDMS microchannel enclosed by a microcontact printed nanoporous polycarbonate membrane. The microchannel is filled with KCI solution as the internal solution.

By modifying the electrodeposition method, nanosheet AgCI structure was grown rather than the conventional globular morphology. The bare Ag/AgCl potential drift with the former morphology was found to be

In conclusion, a modified electrodeposition method and free-diffusion liquid junction micro fluidic reference electrode is proposed to improve the stability and extend the lifetime of a reference electrode with very low potential drift.

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