NSF U.S.-N. Korea Forum, Sept 11, 2017 “Conductive for Wearable Electronic Applications”

John L. Volakis

Dept. of Electrical and Computer Engineering Florida International University E-mail: [email protected]

Collaborator: • Prof. Asimina Kiourti, The Ohio State Univ. 1 Ensuing Concept

• Create -based electronics for integration into clothing or fabrics. Goal is to enable communications, IoT and sensing without using handhelds or discrete accessories. – Current Wearables are lumped accessories • Can we create electronic surfaces that include circuits and IC components and which are part of our clothing. • Can we power these electronics using remote power harvesting.

2 Multi-Sensor and Transceiver Board on Textile surfaces

• Decompose chip into smaller components (0.5 to 1 mm) and insert them across the textile grid. • Employ our electronic textile grids to create circuits and connections around the chips. • Create matching circuits and connections to multitude of sensors, including wireless sensors • Distributed flexible batteries • Eventually, power harvesting surfaces

UHF RFID reprogrammable tag circuit board Board Features • Multiple sensors Entire chip • Data Processing & • Data Logging Board is • Reprogrammable on board printed on • UHF RFID EPC Class 1 Gen 2 textile compatibility surface • Interface to externally designed Antenna 3 Future Electronics will be Wearable

Wearables:  37% annual growth  300 million devices to ship • Morgan Stanley projects a $1.1T market for IoT and wearables. Flexible Electronics are at their Infancy

(similar to transistors before microprocessor chips)

Inductors & Capacitors Transmission Line

RF transistor Antenna

Slide from Prof. Jack Ma (Wisconsin) Expanding Frontiers in Biosensing

• Wireless sensors embedded into clothing for continuous monitoring of human physiology unprecedented spatial density will provide new modes of diagnostics for healthcare delivery and research.

Current state of art- Medtronic ECVUE, all electronics are external, limiting use to clinic 6 Bringing Electronics into Weaved Textiles

Will be Challenging

Courtesy of UC-San Diego

7 Traditional Sensors and Electronics

Existing sensors and electronics are rigid, breakable, bulky, and obtrusive.

8 Our Embroidery Technology

HFSS model

Export to specific Digitization computer program

Embroidered antenna

E-threads

Polyester fabric E-thread

9 Threads Used for Antenna Embroidery

Assistant : Regular non- conductive thread.

E-threads: Metal-coated polymer threads, bundled into groups of 7s to 600s to form threads.

Picture from Syscom

Assistant

Metal coating for Needle conductivity Back side fabric Polymer core E-threads Antenna side for strength Bobbin

10 E-Textile Electronics in Our Group Rigid prototypes

Flexible E-textile prototypes

bendable strechable 11 Automated Embroidery of Textile E-threads

HFSS model • Export antenna design pattern.

• Digitize thread route for automated embroidery.

• Embroider on fabrics using braided or twisted E- Export to specific (embroidery process uses assistant non- computer program conductive yarns to “couch” down E-fibers). Digitization • E-fibers: Metal-coated polymer fibers, bundled into groups of 7s to 600s to form threads. Each thread may be down to ~0.12mm in diameter.

Embroidery principle Embroidered Assistant yarns antenna Needle Back side Polyester fabric E-fibers Antenna side

E- Bobbin

John L. Volakis 12 0.1 mm – Precision Achieved in Embroidery

Former Technology (2013) Latest Technology (2016)

Provider SYSCOM, USA ELEKTRISOLA, Switzerland # of filaments 664 7 Diameter 0.5mm ~0.1mm 0.5mm ~0.1mm

Embroidery accuracy

Archimedean Logarithmic Sinusoidal Embroidery 2 threads/mm 7 threads/mm density 13 Fabric Electronics for Adaptable Smart Technologies:E- TextilesIoTs, Communications can & be “Printed” on any Fabric Sensing (FEAST)

14 E-Textiles vs. Wearables E-Textiles Wearables Apple Watch: heart rate sensor, GPS and accelerometer used to measure “the many ways you move” > $350

https://www.apple.com/watch/

Jawbone Activity Tracker: tracks activity, sleep stages, calories, and heart rate. > $30 https://jawbone.com/

Sensoria Smart Socks: detects parameters important to the running form, including cadence and foot landing technique $200 http://www.sensoriafitness.com/ 15 E-Textile Properties

16 Attenuation Comparison of E-textile and Copper TL

E-fiber textiles are efficient conductive media for RF applications

0.6 0.5 E-fiber TL 0.4 Cu TL 0.28dB/cm 0.3 0.18dB/cm 0.2 0.15dB/cm

(dB/cm) 0.11dB/cm

 0.1 0.10dB/cm 0 0.07dB/cm 0.04dB/cm 0.05dB/cm -0.1 0 1 2 3 4 5 6 Frequency (GHz) • Overall attenuations of E-fibers are small, making it an efficient conductive media for RF designs. • Increased attenuation losses at higher frequencies are due to surface roughness and imperfect metallization of the E-fibers.

17 Textile Circuit Assembly on PDMS Substrate

Textile laminate

PDMS laminate

laminate Flip PDMS

• PDMS: polydimethylesiloxane. • Elastomeric substrate, mechanically compatible with embroidered textile circuits.

• Tunable dielectric constant of (εr~3-13) with ceramic loading. • Uniform PDMS substrate by casting. • Partially cured PDMS as lamination adhesive. E-fiber Polymer substrate

18 E-Textile Antennas Improve the Communication Range vs. Traditional Copper-Based Antennas

Wi-Fi hotspot

E-textile antenna Communication[m] range

Traditional copper Wi-Fi Antenna

Higher gain E-textile antennas increase max. communication distance (sensitivity). . Example: for 3 dB increase in antenna gain, max. communication range increases by ~ 40% (~200 m), assuming a transmitted RF power of 10 dBm. 19 Extreme Mechanical and Thermal Tolerance

Mechanical Testing Thermal Testing

• 2-hour hot storage test at 90oC, carried out at the OSU Materials 50 mm/min Science Dept. • 2-hour cold storage test at -85oC, carried out at OSU Biomed. Eng. Dept.

10 10

0 0

-10 -10

-20 -20

-30 -30 before storage test before flexing -40 -40 after storage test at 90°C after 300 cycles of flexing Boresight Realized Gain [dBi] Gain Realized Boresight after storage test at -85°C

Boresight Realized Gain [dBi] Gain Realized Boresight

-50 -50 500 1000 1500 2000 2500 3000 500 1000 1500 2000 2500 3000 Frequency [MHz] Frequency [MHz]

J. Zhong, A. Kiourti, T. Sebastian, Y. Bayram, and J.L. Volakis, “Conformal Load-Bearing Spiral Antenna on Conductive Textile Threads,” IEEE Antennas and Wireless Propagation Letters, 2016. 20 APPLICATIONS

21 E-Textile Applications

[1] Medical Imaging Sensors [2] Wireless Brain Implants [3] Wearable Antennas for Wireless Communications

[4] RFID Tag Antennas [5] Conformal Antennas

John L. Volakis 22 [1] Body Conformal Textile Imaging Sensors

– Maximize sensitivity (ability to differentiate between small changes in material εr) – Maximize SNR (signal being the power received at the last element) – Minimize effect of outer (skin) layers

Reference Structure Active Port (1) Passive Ports Torso

Metal Electrodes (PEC) Port # Low internal ε εr increase r εr increase

Sensitivity to mass

in question Port readoutPort

sample graph High internal εr

Operating frequencies: 10 MHz, (ISM+ electrical properties diversity)

23 [1] Body-Worn Textile Imaging Sensor

A surgery-free on-body monitoring device to evaluate the dielectric properties of internal body organs (lung, liver, heart) and effectively determine irregularities in real-time ---several weeks before there is serious medical concern.

Active Port (1) • Operates at 40 MHz (HBC ) Passive • Deep detection: >10 cm Ports Torso • Suppresses interference from outer layers (skin, fat, muscle, bone)

Metal Electrodes (PEC)

• 17 electrodes + 16 ports • One excited port, the rest are passive for readouts • Non-uniform to improve impedance matching

L. Zhang, Z. Wang, and J.L. Volakis, “Textile Antennas and Sensors for Body-Worn Applications,” IEEE AWPL, 2012 24 [2] Wireless Brain Implants

8.7 mm • Fully-passive and wireless neurosensors to acquire brain signals inconspicuously. • Integration of extremely simple electronics in a tiny footprint to minimize trauma. • Acquisition of extremely low signals, down to 20μV . This Front Back 10mm pp implies reading of most signals generated by the human brain.

C. Lee, A. Kiourti, J. Chae, J.L. Volakis, “A High-Sensitivity Passive Neurosensing System for Wireless Brain Signal Monitoring,” IEEE 25 T-MTT, 2015. Time-Domain Measurement Results: Neuropotentials

down to 20μVpp can be detected New set-up reduces Minimum Detectable Signal (MDS), allowing reading of

neuropotentials down to 20μVpp. Therefore, most human physiological neuropotentials can be recorded wirelessly.

]

p Historical data for minimum p 600

V simulation

 detectable signal. Our new measurement 500 *former status implant and interrogator 400 demonstrates a 32dB improvement. 300 At f = 140Hz Current time-domain measurement, weneuro can detect:

• MDSneuro = 40 μVpp (-84 dBm3) 2dBat 100 Hz improvement < fneuro < 1 kHz 200 current status • MDSneuro = 30 μVpp (-86 dBm) at 1 kHz < fneuro < 5 kHz

100

MDSneuro = 40 μVpp (-84 dBm) At 100 Hz 0 Min. Detect. Neural [ Signal 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 Neural Signal Frequency (f ) [kHz] New set-up allows reading of neuro neuropotentials down to

20μVpp based on MDSneuro = 30 μVpp (-86 dBm) At 1 kHz MDS = -120dBm across fneuro

MDSneuro = 30 μVpp (-86 dBm) A. Kiourti, C. Lee, J. Chae, and J.L. Volakis, “A Wireless Fully-Passive At 5 kHz Neural Recording Device for Unobtrusive Neuropotential Monitroing,” IEEE Transactions on Biomedical Engineering, 2015. 26 Comparison of Proposed vs. Previously Reported Wireless Brain Implants

Power Operation Min. detectable Ref. Type Footprint Transmission technology consumption distance signal 17 mA from a 1.2 Yin, 2014 Exterior 52 x 44 mm2 Ah battery to run 3.1 - 5 GHz OOK < 5 m N/A for 48 hours

Szuts, 2011 Exterior N/A 645 mW 2.38 GHz FM < 60 m 10.2 μVpp (rat) Rizk, 2007 Exterior 50 x 40 mm2 100 mW 916.5 MHz ASK 2 m N/A Miranda, 14.2 μV (non- Exterior 38 x 38 mm2 142 mW 3.9 GHz FSK < 20 m pp 2010 human primate)

Yin, 2010 Exterior N/A 5.6 mW 898/926 MHz FSK 1 m 13.9 μVpp (rat) Sodagar, Exterior 14 x 16 mm2 14.4 mW 70/200 MHz OOK 1 cm 25.2 μV (guinea) 2009 pp Borton, 24.3 μV (non- Implanted 56 x 42 mm2 90.6 mW 3.2/3.8 GHz FSK 1-3 m pp 2013 human primate) 2 Rizk, 2009 Implanted 50 x 40 mm 2000 mW 916.5 MHz ASK < 2.2 m 20 μVpp (sheep) Sodagar, Implanted 14 x 15.5 mm2 14.4 mW 70-200 MHz FSK N/A 23 μV (guinea) 2007 pp Moradi, Implanted N/A N/A, yet >0 mW N/A 2 cm N/A 2014 Schwerdt, Fully-passive 6000 μV (in-vitro) Implanted 12 x 4 mm2 0 mW < 1.5 cm pp 2012 backscattering 500 μVpp (frog) Fully-passive Lee, 2015 Implanted 39 x 15 mm2 0 mW 8 mm 50 μV (in-vitro) backscattering pp ~ 1.5 cm (on- Kiourti/Volakis Fully-passive body portable Implanted 10 x 8.7 mm2 0 mW 20 μV (in-vitro) , 2015 backscattering receiver pp envisioned)

A. Kiourti, C. Lee, J. Chae, and J.L. Volakis, “A Wireless Fully-Passive Neural Recording Device for Unobtrusive Neuropotential Monitroing,” IEEE Transactions on Biomedical our work Engineering, 2015. 27 Preliminary In-Vivo Validation: Wireless Acquisition of Human ECG

Wired Configuration 1 + ref 0.8 0.6 oscilloscope 0.4 0.2

0

- Voltage (mV) -0.2 -0.4

-0.6

-0.8 wired configuration (original) Wiredwireless configuration Wireless (retreived through neurosensor)

-1 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 Time (sec)

3-lead wearable ECG Wireless Configuration

wireless exterior Post- oscilloscope neurosensor antenna processing to acquire 2-lead output ECG

28 [3] Antennas for Body-Worn Communication

Multiband Dipole for GSM/PCS/WLAN Bands

• 2dB realized gain at all three bands • Omnidirectional patterns in all bands

Textile antenna is as good as the ordinary cell antenna with the best location •Textile antenna is low-profile, unobtrusive, and comfortable to wear. Note: “1-bar”: -100 to -95dBm, “4- bar”: -85 to -80dBm, “6-bar”: -75 to -70dBm, “7-bar”: >-70dBm

Z. Wang, L. Lee, D. Psychoudakis, and J.L. Volakis, “Embroidered multiband body-worn antenna for 29 GSM/PCS/WLAN communications,” IEEE Trans. Antennas Propag., 2014. Colorful Textile Antennas

The colorful textile antenna prototype achieves excellent performance as compared to its copper counterpart. Concurrently, it is flexible, lightweight, and mechanically robust. A. Kiourti and J.L. Volakis, “Colorful Textile Antennas Integrated into Embroidered 30 Logos,” MDPI Journal of Sensor and Actuator Networks, 2015. [4] RFID Tag Antennas

On-Tire Reader ELML E-fiber RFID tag antenna embedded in polymer Threshold Power Testing: RFID tag 5 ft On Tire Threshold Power Test 5 ft  Textile: 22 dBm Simple Folded-Dipole Tag  Copper foil: 20 dBm On-Tire Threshold Power Test • Stretchable (up to 10-15%)  Textile: 24 dBm • Flexible  Wire: 24 dBm • Polymer preserves integrity of E-fiber ELML Dipole Tag with Circular Loops antenna and protects it against corrosion / Easy integration within tire sidewall (bonding during tire curing) • Comparable performance to its copper On Tire Threshold Power Test wire counterpart  Textile: 20 dBm  Copper foil: 21 dBm S. Shao, A. Kiourti, R. Burkholder and J.L. Volakis, “Broadband, Textile-Based Passive UHF RFID Tag Antenna for 31 Elastic Material,” AWPL 2015 [5] Conformal Antennas for Airborne and Wearable Applications

Mechanical Testing Thermal Testing 10 10

0 0

-10 -10

-20 -20

-30 -30 before storage test after storage test at 90°C -40 before flexing -40 after storage test at -85°C after 300 cycles of flexing [dBi] Gain Realized Boresight

Boresight Realized Gain [dBi] Gain Realized Boresight

-50 -50 500 1000 1500 2000 2500 3000 500 1000 1500 2000 2500 3000 Frequency [MHz] Frequency [MHz]

J. Zhong, A. Kiourti, and J.L. Volakis, “Conformal, Lightweight Textile Spiral Antenna on Fabrics,” AP-S 2015. 32 [6] Body Wearable Antennas Must Operate at Low Frequencies

Antenna on-Body

PRC-148 30-512MHz

PRC-154 225-450MHz

PRC-152 30-520MHz PRC-152 PRC-154 PRC-154 762-870MHz 1250-1390MHz 1750-1850MHz RT-1523 30-88MHz

30MHz Antenna On Tissue

Tissue

Continuous 30MHz to 2000MHz (67:1 bandwidth) [7] Body-Area Network for Sensing (MS-BAN)

Features Wireless body-area network for • Body-worn multifunctional apertures on RF functionalized medical sensing (MS-BAN) garment: - Textile based RF sensors for in-situ medical sensing. - Multiband textile antenna for high-speed communication. Multiband Multiband • Continuous data transfer through BAN for in-situ monitoring antenna antenna on mobile APP.

Sensor 1 Sensor 3

Sensor 2 Data Sensor 4

Energy harvester

Body-area sensor In-situ data display on Date storage on Remote access network mobile APP Cloud Server by Physicians

Salman, Wang, Colebeck, Kiourti, Topsakal, Volakis, “Pulmonary edema monitoring sensor with integrated body-area network for remote medical sensing,” IEEE TAP, 62(5):2787-2794, 2014 34 [7] RF Energy Harvesting

Create an RF power harvesting system that wirelessly powers medical devices (e.g., wearable or implantable sensors).

Ambient WiFi energy harvesting system.

high-efficiency (>80%), better than commercially available harvesters

Olgun, Chen, Volakis, Design of an efficient ambient WiFi energy harvesting system, IET Microw. Ant. & Propag., 6(11): 1200-1206, 2012. 35 E-Textile Challenges Technology Challenges Process Challenges Precision achieved in embroidery Applications?

Powering Commercialization Security

Mass Production Protection against corrosion

Textile-electronics integration (sensors, feeding, etc.) 36 Thank you!

Questions: [email protected]

Miami, Florida

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