Smart fabrics/clothing or interactive/electronic textiles typically have conductive fibers or sensors attached to or woven into the clothing material. Like other wearables, smart clothing sends data to a secondary device where the user can evaluate the information.
Advances over the last few years in electronics have led to the development of electronic (E-textiles) or smart textiles. Smart textiles and garments have the ability to sense environmental stimuli and react or adapt in a predetermined way. This involves either embedding or integrating sensors/actuators and electronic components into textiles for use in applications such as medical diagnostics and health monitoring, consumer electronics, industrial monitoring, safety instruments and automotive textiles.1
Table 1: Types of smart textiles.
|
Generation
|
Characteristics |
| First: “Passive smart textiles” | Can only sense the environmental conditions. |
| Second: “Active smart textiles” |
Incorporate actuators and sensors. Types include: • Shape memory • Water-resistant • Chameleonic • Vapor permeable heat storage • Thermo regulated • Vapor absorbing • Heat evolving fabric. |
| Third: “Ultra Smart Textile” | Can sense, react and adopt according to external stimuli and environmental conditions. |
Source: Future Markets.
The number and variety of smart textiles and wearable electronic devices has increased significantly in the past few years, as they offer significant enhancements to human comfort, health and well-being. Wearable low-power silicon electronics, light-emitting diodes (LEDs) fabricated on fabrics, textiles with integrated Lithium-ion batteries (LIB) and electronic devices such as smart glasses, watches and lenses have been widely investigated and commercialized (e.g. Google glass, Apple Watch).
There is increasing demand for wearable electronics from industries such as:
- Medical and healthcare monitoring and diagnostics.
- Sportswear and fitness monitoring (bands).
- Consumer electronics such as smart watches, smart glasses and headsets.
- Military GPS trackers, equipment (helmets) and wearable robots.
- Smart apparel and footwear in fashion and sport.
- Workplace safety and manufacturing.
Advances in smart electronics enable wearable sensor devices and there are a number of devices that are near or already on the market. Textile manufacturers have brought sensor based smart textiles products to the market, mainly for the collection of bio-data (e.g. heart-rate, body temperature etc.) and in workplace safety. The use of textiles as the smart devices themselves also presents significant advantages over watches and wristbands in terms of long-term use.
Table 2: Smart textile products.
| Generation | Products |
| First generation |
• Under Armour Healthbox Wearables • Adidas MiCoach • Sensoria fitness garments |
| Second generation |
• Jiobit wearable kid tracker • Ralph Lauren PoloTech • Jabil Circuit Textile Heart Monitoring • Hexoskin Performance Management • Asensei Personal Trainer • OmSignal Smart Clothing • Stretch Sense Sensors (wearable motion capture) • C3fit IN-pulse • NuMetrex Heart Rate Monitors, Workout Clothes and Fitness Gear |
| 3rd Generation |
• AdvanPro Pressure Sensing Shoes • Tamicare 3D printed Wearables with Integrated Sensors • AiQ Smart Clothing Stainless Steel Yarns • Bebop Sensors Washable E-Ink Sensors • CLIM8 GEAR Heated Textiles • NTT Data and Toray hitoe smart shirt |
Source: Future Markets.
However, improvements in sensors, flexible & printable electronics and energy devices are necessary for wider implementation and nanomaterials and/or their hybrids are enabling the next phase convergence of textiles, electronics and informatics. They are opening the way for the integration of electronic components and sensors (e.g. heat and humidity) in high strength, flexible and electrically conductive textiles with energy storage and harvesting capabilities, biological functions, antimicrobial properties, and many other new functionalities.
The industry is now moving towards the development of electronic devices with flexible, thin, and large-area form factors. Electronic devices that are fabricated on flexible substrates for application in flexible displays, electronic paper, smart packages, skin-like sensors, wearable electronics, implantable medical implements etc. is a fast growing market. Their future development depends greatly on the exploitation of advanced materials. Recent advances in stimuli-responsive surfaces and interfaces, sensors and actuators, flexible electronics, nanocoatings and conductive nanomaterials will result in the development of a new generation of smart and adaptive electronic fibers, yarns and fabrics, healthcare devices, smart surfaces, smart packaging and wearables such as smart watches and e-textiles.2 3
Nanomaterials such as carbon nanotubes (CNT), silver nanowires graphene and other 2D materials are viewed as key materials for the future development of wearable electronics for implementation in healthcare and fitness monitoring, electronic devices incorporated into clothing and ‘smart skin’ applications (printed graphene-based sensors integrated with other 2D materials for physiological monitoring).4 5
These materials are naturally more suitable for integration with flexible, soft or glass substrates and can potentially offer the electronic performance needed for low-power GHz systems. CNTs, graphene, silver nanowires, other nanoparticles and 2D material thin films with exceptional electrical properties and mechanical robustness are under development for application in:
- Flexible e-paper.
- Wearable devices for physiological monitoring.
- Wearable and flexible medical devices.
- Flexible digital x-ray technology.
- Smart plastics.
- Electronic components on flexible substrates for distributed media.
- Sensors on flexible substrates.
Figure 1: Graphene LEDs incorporated into a dress. The dress changes colour in sync with the wearer’s breathing.
Image credit: University of Manchester.
Conductive inks
Nanomaterial based conductive inks have been applied to thin thermoplastic polyurethane (TPU) films that are then laminated onto fabrics to produce smart active wear, health monitoring clothing and other smart textiles. The films provide excellent durability and stability (washable for up to 100 cycles, stable through repeated elongation).
Figure 2: Mimo baby monitor.
Image credit: Rest Devices, Inc.
Industrial monitoring
The market for wireless devices in industrial applications has grown significantly over the last few years. Applications include:
- Hand-worn terminals in logistics and warehousing.
- Heads-up displays (HUDs) in production lines.
- Smart clothing to track user location and physiological monitoring.
- Sensory smart fabrics to detect industrial gases.
In partnership with Eeonyx, BeBop Sensors, Inc. has developed the Smart Helmet Sensor System, the first helmet system employing a Force Location Sensor System which uses flexible fabric sensors for high resolution, location-specific impact information. The Smart Helmet System provides state-of-the-art analysis tools that track the exact impact location and velocity thresholds. The system can also be programmed to trigger safety response commands, such as an emergency call or other response.
Figure 3: BeBop Sensors Smart Helmet Sensor System.
Image credit: BeBop Sensors.
Military
The US military is a significant consumer of wearable electronics and monitoring clothing, with HUDs and smart clothing for physiological monitoring and biological and chemical detection already in use. The US military is conducting several programs including U.S. Future Force Warrior (FFW) and TALOS uniforms, to develop new vest designs and provide improved protection.
University of Dartmouth technology startup C2Sense is developing a conductive smart fabric capable of detecting and protecting users from toxic gases. The fabric consists of a cotton support modified with Cu-BTC MOF/oxidized graphitic carbon nitride composites. The latter were developed in the lab previously and tested as nerve agent detoxification media and colorimetric detectors. Combining Cu-BTC and g-C3N4-ox resulted in a nanocomposite (MOFgCNox) of heterogeneous porosity and chemistry. Upon the deposition of MOFgCNox onto cotton textiles, a stable fabric with supreme photocatalytic detoxification ability towards the nerve gas surrogate, dimethyl chlorophosphate, was obtained.
The detoxification process was accompanied by a visible and gradual color change that can be used for the selective detection of chemical warfare agents and for monitoring their penetration inside a protective layer.
Figure 4: C2Sense flexible sensor.
Image credit: C2Sense.
The Army’s Natick Solder Research, Development and Engineering Center (NSRDEC) has developed the Torso and Extremities Protection (TEP) system which will be available to soldiers in 2019.
Figure 5: Torso and Extremities Protection (TEP) system.
Source: Natick.
Bluewater Defense, Inc. and Vorbeck Materials Corp. have developed next generation, high performance wearable antennas for military, tactical and commercial use in apparel and equipment featuring multiple communication bands including LTE capabilities.
Bluewater and Vorbeck partnered to offer robust, high-gain, low-cost, and discrete conformal printed graphene antennas embedded in military apparel and backpacks. Benefits include:
- Increase existing cell phone coverage by up to 200%
- Significant improvements of upload and download speeds
- Omni-directional coverage through the deployment of an array of antennas
- Supports wide frequency range from 800-3000 Mhz
- Durable, flexible, washable and non-corrosive — environmentally friendly
- Increased battery life by reducing operating power
Energy harvesting textiles
Energy storage devices, especially batteries, require new, novel form factors to meet the needs of growing markets for wearable electronic devices. For example, the reported peak current consumption of Bluetooth Low Energy wireless communication in a wearable sensor module was 18mA, and a smart watch (e.g. Samsung Gear 2) consumes up to 48 mA during calls. 6 7 Producers are seeking two solutions: thin and flexible batteries; energy harvesting wearable devices and smart textiles.
Harvesting and storage of energy in electronic textiles is a crucial step in the development of autonomous wearables. Power sources for flexible and wearable electronic systems should themselves be flexible and require minimal or no wired charging.
Utilizing nanomaterials for energy harvesting will potentially allow for self-sustaining wearables, offering a combination of high-capacity battery storage, energy harvesting using photovoltaics, and power electronics to regulate voltage. This generally entails the use of flexible thin-film batteries and photovoltaic modules in power systems for wearable sensors.
Figure 6: Solar energy harvesting textile.
Image credit: Georgia Tech.
Existing solutions for solar energy harvesting textiles use conventional silicon or plastic solar cells that are sewn or laminated onto the fabric. These approaches make the fabric relatively inflexible and alters the feel of the textile dramatically. However, a new generation of flexible organic cells offers can be fully integrated onto the fabric that acts as the substrate, maximizing the feel of the textile and flexibility compared to the conventional solar panel attached to the textiles.
Recently, the demand for lightweight, flexible and wearable dye-sensitized solar cells (DSSCs) incorporating TiO2 nanoparticles has been increased rapidly.8 9 Printed, organic photovoltaics (OPV) are also a key area of next-generation thin-film solar technologies, and researchers and companies are developing polymer-based flexible OPV for applications in wearables. The integration of solar cells and photovoltaic devices in wearables also requires flexible electrical supplies.
ThermalTech is developing a patented solar powered smart fabric . Made from stainless steel yarn, the ThermalTech fabric is lightweight and gathers energy from the sun or artificial light to keep the body warm even after the sun has set. Providing warmth without the bulk found in traditional outerwear apparel, the ThermalTech fabric allows for a lighter and more fashionable look, even when in the cold outdoors.
Figure 7: ThermalTech’s ‘Solar Powered’ Smart Jacket.
Image credit: ThermalTech.
REFERENCES
1. http://www.mdpi.com/1424-8220/14/7/11957
2 . Jia, W. et al. Wearable textile biofuel cells for powering electronics. J. Mater. Chem. A 2, 18184–18189 (2014).
3. Song, Z. et al. Kirigami-based stretchable lithium-ion batteries. Sci. Rep. 5, 10988 (2015).
4. http://pubs.acs.org/doi/abs/10.1021/nl903949m
5. http://pubs.acs.org/doi/abs/10.1021/nl2013828
6. Song, Z. et al. Kirigami-based stretchable lithium-ion batteries. Sci. Rep. 5, 10988 (2015).
7. MacKenzie, J. D. & Ho, C. Perspectives on energy storage for flexible electronic systems. Proc. IEEE 103, 535–553 (2015).
8. Z. Zhang, et al., Adv Mater, 2014, 26,466-70.
