High Performance Flexible Fabric Electronics
for Megahertz Frequency Communications
Rob Seager(Loughborough University)
Tilak Dias(Nottingham Trent University)
ADVANCED THERAPEUTIC MATERIALS LTD
The Partners• Loughborough University – antenna specialists• Nottingham Trent University – textile material
properties, performance and design expertise• Cash’s – Major international player in textiles and
anti counterfeiting for clothing• Defence Marine Systems – understanding of
potential applications in defence and aerospace• Advanced Therapeutic Materials Ltd – innovation in
manufacturing of textiles• Antrum Ltd – expertise in the commercialisation of
antenna technologies• IEMRC – invaluable investment and support
Current Achievements• Full Fabric Patch and Dipole Antennas• Meshed Antennas• Copper Wire Antennas• Stitch Direction Study• Washing and Abrasion Study• On-body Measurements• Bending Measurements• Frequency Selective Surfaces
Full Fabric Patch and Dipoleso Performance makes these
antennas commercially viable
o Some variability that still needs to be addressed
o Amberstrand patcheso Copper wire and
Amberstrand dipoles
Match for eight nominally identicalembroidered patch antennas
AmberstrandDipole
Copper WireDipole
Amberstrand and Solid Copper Patch Antenna Results
Fine Copper Wire Dipole On Body Antenna Results
1 2 3 4 5 6Frequency (GHz)
Embroidered Copper Wire Dipoles
-35
-30
-25
-20
-15
-10
-5
0
Mea
sure
d S
11 (d
B)
1.775 GHz-32.59 dB
1.725 GHz-21.85 dB Without Teflon
Ref CuWD_06With TeflonRef CuWDT_06
Sample Frequency (GHz) S11 (dB) Gain (dBi) Efficiency (%)Fine Copper Wire on denim + cotton
1.955 ‐38.09 4.43 78
Fine Copper Wire on Teflon + denim + cotton
1.940 ‐19.45 4.09 73
The primary objective of the research is to find the most effective way to produce a fabric antenna by using digital embroidery technology.
Aims and Objectives
Research Activities
1. Study of electro-conductive yarns for the embroidery process
2. Creation of fabric antennas
3. Investigation of fabric based interconnection systems
1. Analysis of electro‐conductive yarns for the embroidery process
Activities:
• Survey of electro-conductive yarns, manufacturers and suppliers
• Tensile testing of electro-conductive yarns to determine their stress-strain behaviour
• Testing of electro-mechanical properties of electro-conductive yarns
• Evaluation of electro-conductive yarns for embroidering
Electro‐conductive fibres and yarns
Metal yarns fine metal wire (mono‐filament and multi‐filament)
Blended yarnsPA or PE fibres with either carbon or metal fibres
Metal deposition yarnsPA with Ag or Zylon with Ag or Ni
Carbon fibres and yarns
Conducting polymeric yarns
Stainless steel yarn
PA yarn plated with Ag micro‐layer
• Stainless steel yarn from Bekintex NV
• X-Static yarn from Noble Biomaterials Inc
• Shieldex yarn from Statex GmbH
• Amberstrand yarn from Syscom Advanced Materials Inc
Yarn DC Resistance in Ohms/m
X‐Static 3078.22 (34dtex/10 filaments)
Shieldex 499.67 (150dtex/34 filaments)
Stainless steel 33.14
Amberstrand 6.56 (200dtex/66 filaments)
Gold (18 carat) 4.19
Electro‐conductive fibres and yarns
-1
0
1
2
3
4
5
0 50 100 150 200 250
Number of Cycles
LOG
(Res
ista
nce
per u
nit l
engt
h)- L
OG
(Ohm
s/m
)
X-static
Statex
Steel yarn
AmberStrand
X‐Static yarn (34dtex/10f)
Shieldex yarn (150dtex/34f)
Stainless steel yarn
Amberstrand (200dtex/66f)
X‐Static yarn (34dtex/10f)
Shieldex yarn (150dtex/34f)
Stainless steel yarn
Amberstrand (200dtex/66f)
Cyclic loading of conductive yarns Change of electrical resistance
Embroidery Technology
2. Creation of fabric antennas
BarudanBEVT‐Z1501CB
BarudanBEVT‐Z1501CB
Formation of Lockstitches
Embroidery yarn
Looper yarn
Observations – Embroidery Technology
• Difficulties encounters with X-Static yarns (also too high electrical resistance)
• Difficulties also observed with rigid (stiff) yarns and/or metal wire (tension dials and looper yarn package)
• Higher stitch densities would result in yarn breakages
• Higher frictional properties of electro-conductive yarns (the main issue)
2. Creation of fabric antennas
BarudanBEVT‐Z1501CB
BarudanBEVT‐Z1501CB
Yarn Friction
• Change of yarn tensioning devices (cymbal tensioners)
Figure 1: conventional tension dials Figure 2: cymbal tension device
• Improve yarn contact surfaces
• Reduce yarn frictional properties; yarn lubrication
Stitch Direction
3 separate shapes
Embroidery speed, 500 rpm
Variation of stitch Direction - Continuous shape
One continuous shape acting like a sheet of metalEmbroidery speed, 500 rpm
2. Creation of fabric antennas
Durability of fabric antennas
• Abrasion testing
• Wash testing
Abrasion testing
• Martindale abrasion machine in accordance with BSI
• Tested against itself and the BSI standard abradant fabric
• 9kg loading weight
Initial measurement - DC 0.133ΩAfter 10000 rubs - DC 0.246ΩAfter 20000 rubs - DC 0.307Ω
Initial measurement - DC 0.248ΩAfter 10000 rubs - DC 1.102ΩAfter 20000 rubs - DC 2.701Ω
BSI standard abradant fabric; 0.8 SD Military fabric; 0.6 SD
Testing of 10cm x 3 mm transmission line against military and abrasion fabric at 0.6 and 0.8 stitch densities
Conclusions
• Stitch density makes a difference to the durability of the embroidered antennas
• Properties of Amberstarnd yarn are retained even after abrasion testing; more analysis necessary understand how this affects the antenna performance
• No test standards for testing embroidered antennas
2. Creation of fabric antennas
Durability of fabric antennas
• Abrasion testing
• Wash testing
Wash Testing
• Determine the change of dimensions of the antennas due to washing
• Access the change in electrical properties (DC resistance) of the antennas due to washing
• Use of domestic washing machineWash cycle: 30°C; 47 minutes; 800 rpm spin; domestic washing powder
Conclusions: no significant differences have been observed
Meshed Patch Antennas• Need to control cost• Need to minimise
stiffness of antenna system
• Need to maintain performance
• More modes availableo Multiband antennas
Meshed Patch Antennas• Need to control cost• Need to minimise stiffness
of antenna system• Need to maintain
performance• More modes available
o Multiband antennas• Meshed ground plane also
an option being considered
Publications• 5 conference papers published
• 2 conference papers accepted
• 1 journal paper published in IET Microwaves, Antennas and Propagation. (August 2013)
• 2 journal papers submittedo Velcro connections o FSS – spin out project with School of Arts at Loughborough
• 3 journal papers plannedo Copper wire and Amberstrand dipoles – close to completiono Effect of washing and abrasion - close to completiono Effect of meshing patch antennas
Thanks to the Loughborough and Nottingham
Trent University Research Team
• Yiannis Vardaxoglou (LU)• Tilak Diaz (NTU)• Rob Seager (LU)• Tess Acti (NTU)• Will Whittow(LU)• Alford Chauraya(LU)• Shiyu Zhang(LU)
Conclusions• A huge amount has been achieved in this project.• Collaboration has resulted in two small internal
projects being funded• Funding for continuation work is being sought• The collaboration has been hugely beneficial• Industrial input has been timely and valuable to the
academics