Date of Award

6-2015

Degree Name

Doctor of Philosophy

Department

Electrical and Computer Engineering

First Advisor

Dr. Massood Z. Atashbar

Second Advisor

Dr. Margaret Joyce

Third Advisor

Dr. Paul D Fleming

Fourth Advisor

Dr. Bradley J Bazuin

Keywords

Printed sensors, Flexible sensors, Electrochemical, LC sensors, Printed OTFT, Humidity sensors

Abstract

Printed electronics has gained a remarkable interest over the past decade for the fabrication of cost efficient electronic devices, with a major focus on the development of flexible sensors. This dissertation focuses on the fabrication of flexible sensors using traditional printing processes such as screen, inkjet and gravure printing.

A flexible organic thin film transistor (OTFT) was successfully fabricated on a polyethylene terephthalate (PET) substrate and employed as a humidity sensor. Aluminum gate electrode was thermally evaporated on PET and UV clear dielectric layer was spin coated. Source and drain silver interdigitated electrodes were screen printed. 6,13-bis(triisopropylsilylethynyl) pentacene, a humidity sensitive material, was inkjet printed. The output characteristics of the printed OTFT were recorded for varying humidity levels, ranging from 15% RH to 85% RH. The humidity response of the fabricated sensor demonstrated the feasibility of using traditional printing processes for the fabrication of OTFT based sensors.

A flexible electrochemical sensor was screen printed on PET. Carbon and silver based inks were used for metallization of the working, counter and reference electrodes. 1,10-phenanthroline and its derivative naphtho[2,3-a]dipyrido[3,2-h:2',3'-f]phenazine-5,18-dione (QDPPZ) was synthesized as sensitive layers for Hg2+ and Pb2+, respectively. Cyclic voltammetry response of the sensor resulted in reduction peaks at 0.2 eV and -0.6 eV for selective detection of Hg2+ and Pb2+, respectively. The response of the electrochemical sensor demonstrated the use of traditional printing processes and synthesized chemicals for the selective detection of heavy metals.

An inductor capacitor (LC) wireless passive sensor for the detection of toxic heavy metals was screen printed on PET using a silver ink. Palladium nanoparticles were synthesized and drop casted onto the LC sensor as a sensitive layer. The change in resonant frequency of the LC sensor towards varying concentrations of heavy metal ions was remotely monitored using a screen printed detection coil. The LC sensor was able to detect mercury ions (Hg2+), as low as 1 μM, with a resonant frequency shift of 0.2 MHz. The feasibility of the sensor to vary its resonant frequency with different concentrations of heavy metal ions such as Hg2+ and lead ions (Pb2+) was demonstrated.

Access Setting

Dissertation-Open Access

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