Mechanical and High-Frequency Electrical Study of Printed, Flexible Antenna Under Deformation

Abstract

The meaningful discussions we shared on research work and life have indeed made my experience in graduate school more than enjoyable. In addition, I would like to thank other professionals and students who are involved in my research including Dr. Jim Huang from Hewlett Packard Enterprise as well as Sridhar Sivapurapu and Nahid Aslani Amoli from Dr. Swaminathan's group. Many thanks are due to my parents who always stood behind every critical decision I made. I would not have accomplished this milestone without their love, support, and trust. I would like to acknowledge that this material is based, in part, on research sponsored by Air Force Research Laboratory under agreement number FA8650-15-2-5401, as conducted through the flexible hybrid electronics manufacturing innovation institute, NextFlex. ivTABLE OF CONTENTS ACKNOWLEDGEMENTS iii LIST OF TABLES vi LIST OF FIGURES vii LIST OF SYMBOLS AND ABBREVIATIONS xiv SUMMARY xvi CHAPTER 1. INTRODUCTION CHAPTER 2. BACKGROUND AND LINTERATURE REVIEW 2.1 History of Conformal Antenna and Flexible Printed Antenna 2.2 Mechanical Testing of Flexible Printed Electronics 2.3 Antenna Performance Under Strain CHAPTER 3. OBJECTIVES AND SCOPE CHAPTER 4. ANTENNA DESIGN AND FABRICATION RESULTS 4.1 Fabrication Process 4.2 Antenna Design in HFSS 4.2.1 Layer Thickness 4.2.2 Material Electrical Properties 4.2.3 HFSS Simulation Setup and Results 4.3 Fabrication Results and Comparison to Simulation CHAPTER 5. MANDREL BENDING TEST AND RESULTS 5.1 Mandrel Bending Test Over Different Sizes of Mandrel 5.1.1 Experimental Setup and Procedure 5.1.2 Experimental Test Results 5.2 Cyclic Mandrel Bending Test over Mandrel Size of 0.625 in. Radius 5.2.1 Experimental Procedure and Results of Sample P1 5.2.2 Experimental Procedure and Results of Sample P2 CHAPTER 6. MECHANICAL FINITE-ELEMENT ANALYSIS OF MANDREL BENDING TEST 6.1 Geometry Modeling 6.2 Material Modeling 6.2.1 Characterization of Printed Silver Ink's Property 6.2.2 Other Materials' Properties 6.3 Loading and Boundary Conditions v 6.4 Initial Meshing Details 6.5 Mesh Convergence and Simulation Results CHAPTER 7. BIAXIAL BENDING TEST AND RESULTS 7.1 Experimental Fixture Design and Setup 7.2 Experimental High-Frequency Measurement Results 7.3 SEM Images Results CHAPTER 8. MECHANICAL FINITE-ELEMENT ANALYSIS OF THE BIAXIAL BENDING TEST 8.1 Loading and Boundary Conditions 8.2 Mesh Convergence and Simulation Results CHAPTER 9. Conductivity Change Impact on Patch Antenna's High-Frequency Electrical Behavior 9.1 Updated HFSS Model 9.2 Conductivity Impact on the S11 Response CHAPTER 10. Conclusion, Contributions, and Future Work 10.1 Conclusion 10.2 Contributions 10.3 Future Work REFERENCES CHAPTER 1.

Fully Flexible, Polymer based Microwave Devices Part I: Materials, Fabrication Technique, and Application to Transmission Lines

“…The antenna's performance and bending effects will be discussed in part II of this work [38]. Many materials that are used in the "flexible" electronics can be considered flexible only with extremely small thicknesses (around 100um), e.g., polyimide (Kapton) [39], polyethylene [40], PTFE [41], and others [42], [7], [43]. To show the fair flexibility our polymer-based microwave devices, the substrate thickness is 3mm in all cases.…”

“…The flexible microwave electrons can be roughly divided into three groups by types of conducting and dielectric materials: 1) semi-ridged [3], [4], [5], which are based on very thin Roger, Duroid, or LCP (liquid crystal polymer) substrates with copper cladding; 2) thin-flexible [6], [7], [8], which are based on PEN (polyethylene naphthalate), PET (polyethylene terephthalate) and Kapton (polyimide) and similar rigid polymers with copper cladding or 3D printed Ag-inks; 3) polymer-based [9], [10], which are produced fully or partially from elastomers and can have substrate thickness more than 1 mm without significant impacts on the flexibility.…”

Fully Flexible, Polymer based Microwave Devices Part II: Flexible Antennas and Performance Evaluation

“…The substrate thickness is 3mm in all cases, which illustrates the flexibility with relatively high substrate thicknesses. Many materials that are used in the "flexible" electronics can be considered flexible only with minimal thicknesses (around 100um), e.g., polyimide (Kapton) [20], polyethylene [21], PTFE [22], and others [23], [7], [24].…”

“…Generally, the flexible microwave electrons can be divided into three groups by types of materials: 1) semi-ridged [3], [4], [5], which are based on very thin Roger, Duroid, or LCP (liquid crystal polymer) substrates with copper cladding; 2) thin-flexible [6], [7], [8], which are based on PEN (polyethylene naphthalate), PET (polyethylene terephthalate) and Kapton (polyimide) and similar rigid polymers with copper cladding or 3D printed Ag-inks; 3) polymer-based [9], [10], which are produced fully or partially from elastomers and can have substrate thickness more than 1 mm without significant impacts on the flexibility. Most importantly, it allows having unique properties such as self-healing capabilities [11], [12], electro-mechanical actuation [13], [14], etc., which opens new ways for reconfigurability and integration.…”

Fully Flexible, Polymer based Microwave Devices Part I: Materials, Fabrication Technique, and Application to Transmission Lines

“…Many materials that are used in the "flexible" electronics can be considered flexible only with extremely small thicknesses (around 100um), e.g., polyimide (Kapton) [39], polyethylene [40], PTFE [41], and others [42], [7], [43]. To show the fair flexibility our polymer-based microwave devices, the substrate thickness is 3mm in all cases.…”