Date of Award

12-2017

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

Keywords

Printed Electronics (PE), flexible Sensing Systems, Surface Enhanced Raman Spectroscopy (SERS), touch sensors, vibration energy harvesters

Abstract

Printed electronics (PE) has been gaining a significant level of interest and is being used for developing a wide range of electronic systems for various applications, specifically in the sensor fields. This dissertation focuses on the development of flexible sensors and energy harvesters for application in sensing systems by employing additive manufacturing processes.

Initially, an efficient surface enhanced Raman spectroscopy (SERS) substrate was fabricated by gravure printing a thin film of silver nanoparticle ink on a flexible polyethylene terephthalate (PET) sheet. The feasibility of the printed substrate to be used as a SERS substrate for the detection of explosive materials, such as DNT in the vapor phase, was demonstrated. An enhancement factor of three and four for the peaks at 1350.13 cm-1 was obtained for the SERS-based response of the printed SERS substrate toward DNT solution and vapor, respectively, when compared to target molecules adsorbed on bare PET. The effect of temperature on the intensity of Raman spectrum was also examined. The effect of bending on the SERS response was also investigated. The fabricated SERS substrate has the promising potential to be used as a cost-effective substitution in commercialized SERS detection applications.

Then, piezoelectric-based touch sensors were successfully fabricated on flexible PET and paper substrates by using the screen printing technique. The capacitive devices were fabricated using silver and polyvinylidene uoride (PVDF) inks as the metallization and piezoelectric layers, respectively. Characterization of the substrates and various printed layers of the touch sensor were performed. Piezoelectric-voltage analysis demonstrated that the printed sensor can be used as both touch and force sensors. The advantage of fabricating touch sensors on flexible substrates is the ability to fold and place the sensor on nearly any platform or to conform to any irregular surface, whereas the additive properties of printing processes allow for a faster fabrication process, while simultaneously producing less material waste in comparison to the traditional subtractive processes.

Finally, three generations of novel piezoelectric-based vibration energy harvester (PVEH) were fabricated and tested. For the first generation, the screen printing technique was used to deposit all piezoelectric and conductive layers of the device. In this device, a PVDF layer was sandwiched between two printed silver electrodes, all fabricated on a PET substrate. PVEHs in different dimensions were fabricated and tested. Test results showed that this fabrication process along with the polarization setup used in this project was not able to provide large enough piezoelectric coefficient so that the vibrated PVEH generates large enough voltage output to pass the rectifying circuit and power the resistive load. For the second generation, PVDF ink was screen printed onto a glass substrate and was peeled-off from the glass substrate after being cured. Then, conductive Metglas was tapped on both sides of the peeled-off PVDF film. The fabricated device was then characterized and tested. However, there were some opportunity to improve the performance of the second generation PVEH. Therefore, the third generation of PVEHs was fabricated by direct printing of silver ink onto PVDF film. In this approach, an aluminum mold was used to form a PVDF film. Then, screen printing technique was used to deposit silver ink onto both sides of the PVDF film as the bottom and top electrodes. The obtained results demonstrated the potential of using additive print manufacturing processes for the fabrication of cost-efficient, lightweight and flexible vibration energy harvesters.

Access Setting

Dissertation-Open Access

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