design and fabrication of fabric near field antenna for wearable applications

148 Pages·2017·29.6 MB·English

DESIGN AND FABRICATION OF FABRIC NEAR
FIELD ANTENNA FOR WEARABLE
APPLICATIONS

A thesis submitted to The University of Manchester for the degree of
Master of Philosophy
in the Faculty of Science and Engineering

2017

YUXI SHI
SCHOOL OF MATERIALS
LIST OF CONTENTS
LIST OF CONTENTS ....................................................................................... 2
LIST OF TABLES ............................................................................................. 6
LIST OF FIGURES ........................................................................................... 7
ABSTRACT ....................................................................................................... 9
DECLARATION ............................................................................................. 10
COPYRIGHT STATEMENT .......................................................................... 11
ACKNOWLEDGEMENT ............................................................................... 13
THE AUTHOR ................................................................................................ 14
ABBREVIATIONS ......................................................................................... 15
CHAPTER 1 INTRODUCTION ..................................................................... 17
1.1 Research Scope ....................................................................................... 17
1.2 Research Gaps ........................................................................................ 19
1.3 Research Aims and Objectives ............................................................... 20
1.4 Research Methodology ........................................................................... 21
1.5 Research Value ....................................................................................... 22
1.6 Outline of the Thesis .............................................................................. 23
CHAPTER 2 LITERATURE REVIEW .......................................................... 25
2.1 Introduction ............................................................................................ 25
2.2 Definition and Development of E-Textiles ............................................ 25
2.2.1 Definition of E-Textiles ................................................................... 25
2.2.2 Current and Future E-Textiles ......................................................... 28
2.2.3 Summary .......................................................................................... 32
2.3 Conductive Materials ............................................................................. 32
2.3.1 Conductive Polymers ....................................................................... 33
2.3.2 Carbon-based Micro/Nano Materials ............................................... 34
2.3.3 Metallic Materials ............................................................................ 35
2.3.4 Summary .......................................................................................... 36

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2.4 Fabrication and Integration Technologies .............................................. 36
2.4.1 Fabrication Technologies ................................................................. 37
2.4.2 Integration Technologies ................................................................. 38
2.4.3 Summary .......................................................................................... 45
2.5 Devices and Applications ....................................................................... 46
2.5.1 Sensors ............................................................................................. 47
2.5.2 Wearable Antennae .......................................................................... 49
2.5.3 Output Devices ................................................................................. 52
2.5.4 Summary .......................................................................................... 52
2.6 Near Field Antennae ............................................................................... 53
2.6.1 Definition of Near Field Antennae .................................................. 53
2.6.2 Characterisation of Near Field Antennae ......................................... 54
2.6.3 Near Field Antennae Mode of Operation ......................................... 55
2.6.4 Summary .......................................................................................... 57
2.7 Conclusions ............................................................................................ 57
CHAPTER 3 MATERIAL PREPARATION AND ANTENNA DESIGN .... 59
3.1 Introduction ............................................................................................ 59
3.2 Material Preparation ............................................................................... 59
3.2.1 Experimental Design ........................................................................ 59
3.2.2 Instrument ........................................................................................ 60
3.2.3 Material ............................................................................................ 61
3.2.4 Experiment ....................................................................................... 62
3.2.5 Test Result ....................................................................................... 64
3.3 Antenna Design ...................................................................................... 66
3.3.1 Resonant Frequency ......................................................................... 66
3.3.2 Inductance and Capacitance ............................................................. 68
3.3.3 Magnetic Flux Density ..................................................................... 69
3.3.4 Quality Factor .................................................................................. 71
3.3.5 Reading Range ................................................................................. 72

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3.3.6 Geometric Dimensions ..................................................................... 75
3.4 Conclusions ............................................................................................ 76
CHAPTER 4 FABRIC NFA FABRICATION PROCESS DEVELOPMENT
.......................................................................................................................... 78
4.1 Introduction ............................................................................................ 78
4.2 Experiment ............................................................................................. 79
4.2.1 Experimental Design ........................................................................ 79
4.2.2 Material ............................................................................................ 80
4.2.3 Instrument ........................................................................................ 80
4.2.4 Experimental Method ....................................................................... 81
4.3 Statistical Analysis and Discussion ........................................................ 83
4.3.1 Factorial Design Experiment ........................................................... 83
4.3.2 Process Development ....................................................................... 86
4.3.3 Discussion ........................................................................................ 93
4.4 Conclusions ............................................................................................ 94
CHAPTER 5 FABRIC NFA FABRICATION PROCESS OPTIMISATION 96
5.1 Introduction ............................................................................................ 96
5.2 Experiment ............................................................................................. 97
5.2.1 Experimental Design ........................................................................ 97
5.2.2 Material ............................................................................................ 97
5.2.3 Instrument ........................................................................................ 97
5.2.4 Experimental Method ....................................................................... 98
5.3 Statistical Analysis and Discussion ........................................................ 99
5.3.1 Steepest Ascent ................................................................................ 99
5.3.2 Central Composite Design Experiment ......................................... 101
5.3.3 Process Optimisation ..................................................................... 105
5.3.4 Discussion ...................................................................................... 110
5.4 Conclusions .......................................................................................... 111
CHAPTER 6 FABRIC NFA PERFORMANCE EVALUATION ................ 113

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6.1 Introduction .......................................................................................... 113
6.2 Experiment ........................................................................................... 113
6.2.1 Experimental Design ...................................................................... 113
6.2.2 Instrument ...................................................................................... 114
6.2.3 Experimental Method ..................................................................... 115
6.3 Performance Evaluation ....................................................................... 117
6.3.1 Quality Factor and Reading Range Test ........................................ 117
6.3.2 Bending Test .................................................................................. 121
6.4 Conclusions .......................................................................................... 122
CHAPTER 7 CONCLUSIONS AND FUTURE WORK .............................. 123
7.1 Conclusions .......................................................................................... 123
7.2 Future work .......................................................................................... 124
Appendix І ..................................................................................................... 125
Appendix И .................................................................................................... 128
REFERENCES .............................................................................................. 131
The Final Word Count: 19,122

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LIST OF TABLES
Table 2-1 Patent search with the keywords of e-textiles (smart textiles,
intelligent textiles, wearable textiles, smart clothing) and antennae. 29
Table 2-2 Electrical properties of normal metallic conductive wires. ...... 36
Table 2-3 Comparison of different integration technologies. ................... 46
Table 3-1 Conductivity and resistivity of conductive yarns. .................... 65
Table 3-2 Conductivity of conductive yarns and metallic wires. ............. 65
Table 4-1 Design factors and levels. ......................................................... 83
Table 4-2 The factorial design experiment. .............................................. 85
Table 4-3 Descriptive analyses for process development. ........................ 86
Table 4-4 Factorial fit: resistance versus NLS, SD, ST. ........................... 87
Table 5-1 The central composite design for resistance. .......................... 104
Table 5-2 Descriptive analyses for process optimisation. ...................... 105
Table 5-3 Response of surface regression: resistance versus NLS, SD. . 106
Table 6-1 Group set for results measurement. ........................................ 117
Table 6-2 The test results for the quality factor and the reading range. . 118

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LIST OF FIGURES
Figure 1-1 Thesis structure and contents. ................................................. 23
Figure 2-1 The products of e-textiles. ....................................................... 25
Figure 2-2 Citation report from Web of Science for the keyword of
e-textiles (smart textiles, intelligent textiles, wearable textiles, smart
clothing). ........................................................................................... 28
Figure 2-3 Carbon-based micro/ nano materials. ...................................... 34
Figure 2-4 The process to produce metallic fibres. ................................... 37
Figure 2-5 The diagram of stitch geometry. ............................................. 42
Figure 2-6 Smart textile devices and applications. ................................... 46
Figure 2-7 NFA applications. ................................................................... 53
Figure 2-8 Citation report from Web of Science with the keyword of near
field antennae. ................................................................................... 54
Figure 2-9 NFA modes of operations. ...................................................... 55
Figure 3-1 The instruments and testing process. ...................................... 60
Figure 3-2 The instruments for testing the width of yarns. ....................... 60
Figure 3-3 The instruments for testing the resistivity. .............................. 61
Figure 3-4 Digital image of conductive yarns. ......................................... 62
Figure 3-5 Digital images of Statex conductive yarns. ............................. 65
Figure 3-6 Equivalent circuit of the NFA. ................................................ 66
Figure 3-7 Rectangular antenna coil. ........................................................ 68
Figure 3-8 Transformer principle of the NFA. ......................................... 72
Figure 3-9 Equivalent circuit of NFA reader antennae and tag antennae. 73
Figure 3-10 Simulation model of the NFA. .............................................. 75
Figure 3-11 The NFA reader. .................................................................... 75
Figure 3-12 Sewn NFA. ............................................................................ 76
Figure 4-1 The sewing machine. ............................................................... 80
Figure 4-2 The multimeter and the supply power ..................................... 81

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Figure 4-3 The fabrication process development experiment. .................. 82
Figure 4-4 The resistance measurement experiment. ............................... 84
Figure 4-5 Main factors plot for resistance. .............................................. 88
Figure 4-6 Interaction plot for resistance. ................................................. 89
Figure 4-7 Contour plot of resistance vs SD, NLS. .................................. 90
Figure 4-8 Surface plot of resistance vs SD, NLS. ................................... 90
Figure 4-9 Contour plot of resistance vs ST, NLS. ................................... 91
Figure 4-10 Surface plot of resistance vs ST, NLS. ................................. 91
Figure 4-11 Residual plots for resistance for process development. ........ 92
Figure 5-1 The fabrication process optimisation experiment. .................. 98
Figure 5-2 Steepest ascent experiment. .................................................. 101
Figure 5-3 Central composite design in the coded variables. ................. 102
Figure 5-4 Contour plot of resistance vs SD, NLS. ................................ 107
Figure 5-5 Surface plot of resistance vs SD, NLS. ................................. 107
Figure 5-6 Contour plot of resistance. .................................................... 108
Figure 5-7 Residual plots for resistance for process optimisation. ......... 109
Figure 6-1 The FieldFox vector network analyser. ................................. 114
Figure 6-2 The NFA reader. .................................................................... 114
Figure 6-3 The experimental method for testing the reading range. ....... 115
Figure 6-4 The experimental method for testing the quality factor. ....... 116
Figure 6-5 The experimental method for evaluating the performance of
the NFA under different bending conditions. ................................. 116
Figure 6-6 Contour plots for performance evaluation. ........................... 118
Figure 6-7 Line chart of resistance vs the reading range and the quality
factor. .............................................................................................. 119
Figure 6-8 The centre frequency under different bending conditions. ... 120

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ABSTRACT
E-textiles, also known as smart clothing or electronic textiles, are textiles or
garments in which electronic devices and other wearable electronics, such as
wiring and sensors, are embedded. E-textiles have received a lot of research
attention in the past fifteen years for their use in wearable applications and
usually refer to any electronic components that can be fixed on textile
substrates.
However, as e-textiles, very little research has been conducted to develop
fabric near field antennae in literature. To achieve fabric near field antennae
for wearable application requirements today in terms of comfort, function,
sensing and ergonomics, this work introduces and realises a complex design
and engineering methodology of fabric near field antennae using sewing
technology. This research is completed by the appropriate conductive material
preparation, the antenna design and fabrication, the process development and
the optimisation, and the performance evaluation.
In the stage of the design and fabrication processes, the near field antenna is
designed and fabricated using sewing technology. The formulae for the
parameters for a near field antenna are derived. Specifically, the relationships
between the resistance and the quality factor (Q value) as well as the reading
range are proved.
In the stage of the development and optimisation processes, the main factors
and the cross effects for the electrical performance of the conductive yarns are
examined by the full factorial design experiment. Then the regression equation
is established to simulate the performance of the near field antenna and the
optimum resistance is calculated by the central composite design experiment.
The results show that the quality factor (Q value) and the reading range
increase accordingly with the decrease of resistance of the conductive yarns.
The simulation results through process development and process optimisation
are in correspondence with the experimental results qualitatively. Moreover,
the near field antenna can work under different bending conditions. Thus, an
optimum fabric near filed antenna for wearable applications has been designed
and fabricated.

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DECLARATION
No portion of the work referred to in the thesis has been submitted in support
of an application for another degree or qualification of this or any other
university or other institute of learning.

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