Date of Award

6-2017

Degree Name

Doctor of Philosophy

Department

Electrical and Computer Engineering

First Advisor

Dr. Massood Z. Atashbar

Second Advisor

Dr. Bradley J. Bazuin

Third Advisor

Dr. Paul D. Fleming

Abstract

Printed electronics has been gaining a significant level of interest and is being used for developing a wide range of sensing systems for various applications in the chemical, biosensor and biomedical sensor fields. This dissertation focuses on the development of flexible sensors and flexible transducers for application in sensing systems by employing additive print manufacturing processes.

Initially, novel printed, flexible and wearable dry electrodes for monitoring electrocardiogram (ECG) signals, without any skin preparation and use of wet gel, were developed. The dry ECG electrodes were fabricated by screen printing silver (Ag) ink on flexible polyethylene terephthalate (PET) substrate, followed by bar coating of multi-walled carbon nanotube (MWCNT)/polydimethylsiloxane (PDMS) composite. The performance of the printed electrodes was investigated by testing the MWCNT/PDMS composite conductivity and measuring the electrode-skin impedance for electrode radii varying from 8 mm to 16 mm. It was observed that the dry ECG electrode with the largest area demonstrated better performance, in terms of conductivity, ECG signal intensity and correlation coefficient to a commercial wet silver/silver chloride (Ag/AgCl) ECG electrode (T716). In addition, the capability of the dry ECG electrodes for monitoring ECG signals in both the relaxed sitting position and while the subject is in motion, were also investigated and the results were compared 2 with a commercial wet electrode. The results obtained demonstrate the feasibility of employing conventional screen printing process for the development of flexible dry ECG electrodes for applications in the biomedical industry.

Then, a novel screen printed and flexible magneto-electric (ME) thin film sensor was developed for the detection of AC magnetic fields, at room temperature. The ME sensor was fabricated by screen printing piezoelectric based polyvinylidene fluoride (PVDF) ink on flexible and magnetic Metglas® substrate. Ag, as top electrode, was then deposited on the printed PVDF layer using a bar coating technique. The performance of the fabricated device was investigated by measuring the induced voltage response towards varying AC magnetic fields and frequencies. An electromechanical resonance of 50 kHz, with a maximum voltage of 21.1 mV, was obtained for the induced voltage-frequency dependence measurements performed. A linear relationship with a sensitivity of 50 mV/Oe and correlation coefficient of 0.9994 was also obtained towards varying AC magnetic fields.

Finally, a novel printed and flexible low frequency ME energy harvester was developed for application in microelectronic devices. The energy harvester was fabricated by screen printing PVDF ink, as a piezoelectric layer, on flexible and magnetic Metglas® substrate. Ag ink, as top electrode layer, was then deposited on the printed PVDF layer using the screen printing technique. The performance of the printed device was investigated by measuring the DC output voltage and maximum power delivered at varying load resistances for a frequency range of 20 Hz to 100 Hz, in steps of 20 Hz. The results demonstrated that the maximum power generated was 24.15 μW at a load resistance of 80 kΩ and frequency of 100 Hz. This relates to a maximum power density of 1837 μW/cm3 for the fabricated ME energy harvester.

Access Setting

Dissertation-Campus Only

Restricted to Campus until

6-2027

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