Graduation Semester and Year

2022

Language

English

Document Type

Thesis

Degree Name

Master of Science in Industrial Engineering

Department

Industrial and Manufacturing Systems Engineering

First Advisor

Emma Yiran Yang

Abstract

Additive manufacturing provides a distinctive layer-wise production method, which is efficient and effective, especially when fabricating products with complex designs and/or multiple materials. One of the promising applications of additive manufacturing is 3D printing flexible piezo-resistive sensors, which measure the strain of human motions by characterizing the changes in resistance. In this research, fused deposition modeling is used to fabricate stretchable piezo-resistive sensors that use thermoplastic polyurethane (TPU) as the stretchable layer and the mixture of TPU and carbon nanotube (CNT) as the electrically conductive layer. Extensive experimental efforts are dedicated to investigating proper mixing technique, filament preparation method, and a range of process parameter settings. To evaluate the quality of 3D printed stretchable piezo resistive sensors, multiple measures are used including filament consistency, print quality, gauge factor, and electromechanical properties from static and dynamic testing. In this study, 7.5 wt.% CNT in the TPU-CNT mixture is chemically prepared (with solvent), its feasibility of being made into 3D printing filament, and 3D printability are investigated. During the static electromechanical testing, the printed sensors are stretched to 10%, 20%, 30%, and 40% strain. The obtained gauge factor which is computed as the ratio of change of resistance to strain is decent overall (over 2 in most cases) but it is relatively less for lesser strain in some cases. If the gauge factor can be increased for smaller strains as well, the sensor with its high sensitivity will have potential applications in wearable electronics and health monitoring systems. In addition, during 10 cycles of dynamic electromechanical testing for 20%, 30%, and 40% strain changes, the resistance change is found to be the most consistent for 30% strain change.

Keywords

Piezo-resistive, Fused deposition modeling, Thermoplastic polyurethane, Carbon nanotube, Gauge factor

Disciplines

Engineering | Operations Research, Systems Engineering and Industrial Engineering

Comments

Degree granted by The University of Texas at Arlington

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