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