Date of Award

8-2015

Degree Name

Doctor of Philosophy

Department

Electrical and Computer Engineering

First Advisor

Dr. Massood Z. Atashbar

Second Advisor

Dr. Bradley Bazuin

Third Advisor

Dr. Paul D. “Dan” Fleming

Fourth Advisor

Dr. Margaret Joyce

Keywords

Printed electronics, flexible electronics, wearablesensors, stretchable sensors, printed sensors, wavysensors

Abstract

Conformal and stretchable wearable sensors provide vital real time information about individual’s health conditions. In this work, Traditional printing methods are used for fabrication of stretchable and wearable sensors which can be mounted on the human skin for the purpose of health tracking. In addition, screen printing technology was utilized to develop printed and flexible electronic circuit board which can be used as a readout circuit along with fabricated wearable sensors. The dissertation is organized and pursued in three projects.

In the first project, screen printing was used to fabricate multi-layer PCBs using printed deposited materials on three distinct substrates. The different characteristics of PET, paper and glass as a substrate for PCBs were analyzed. A method for populating electronic components onto the printed PCB pads was established and demonstrated. Different analysis such as effect of the roughness of the substrates on the electrical performance of the printed lines and effect of the bending on the resistivity of the printed lines were performed. The capability of the printed hybrid PCB circuit to correctly operate and drive an LCD was shown.

In the second project, a new method for fabrication of wavy lines and structures was devised for formation of stretchable and flexible wearable sensors. Thermoplastic polyurethane (TPU) was used as a substrate in this project. Different wavy structure designs were printed and analyzed to determine the best design rules. Silver (Ag) and Carbon Nano Tubes (CNTs) were used for fabrication of wavy lines. The printability, bendability and stretchability of all printed lines were tested and analyzed. Different design rules and parameters such as the ratio of the width of the lines to their radius (W/r) and the length of the extended line to the diameter of the arc (L/D) were tested and analyzed. Printed wavy structures using CNTs showed below 35 % change in the resistance when it was stretched and 50 % strain was applied on the structure. 40 % change in the resistance of the lines printed using silver was obtained when 10 % strain was applied. The results obtained demonstrated that CNTs showed a promising potential to be used for fabrication of strain wearable sensors.

In the third project, a novel wearable sensing platform for the detection of disorder in body movement, temperature and ECG was fabricated. Both wavy structure and non-wavy structure were implemented in these devices. Silver and CNTs inks were used for the fabrication of different sensing parts on the PDMS and tattoo paper as substrates. The strain sensor fabricated on tattoo paper and PDMS were tested towards bending of finger to angles of 10, 20, 30 and 40 degree. 3.66 %, 4.7 % and 4.18 % change was observed in the resistance for each step for sensor 1, sensor 2 and sensor 3, respectively, on tattoo paper. The printed sensor on the PDMS demonstrated average change of 2.7%, 2.2 % and 2.8 % for sensor 1, sensor 2 and sensor 3, respectively, for each step of bending of finger. The printed sensor on the PDMS was successfully implemented as temperature sensors for tracking of the skin temperature. Mixture of silver and silicone was used for fabrication of flexible electrocardiogram sensor on PDMS. The devices’ response demonstrates the feasibility of printed multi-functional wearable sensors for health monitoring applications.

Access Setting

Dissertation-Open Access

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