Nanotechnology in smart textiles and wearable applications

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The need to produce new sensors, flexible & printable electronics and wearable energy harvesting devices is driving the development of nanotechnology in the smart textiles and wearables market.

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.

However, improvements in sensors, flexible & printable electronics and energy harvesting devices are necessary for wider implementation. 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.

Figure 1: Polyera Wove Band.Figure 1: Polyera Wove Band. Image credit: Polyera.

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.1 2 3

Nanomaterials such as carbon nanotubes (CNT), silver nanowires, graphene and other two-dimension (2D) nanomaterials such as silicene are viewed as key materials for the future development of wearable electronics in healthcare and fitness monitoring, electronic devices incorporated into clothing and ‘smart skin’ applications (e.g. 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.

Market growth

Until around five years ago, the healthcare sector was the main consumer of a relatively small market for smart textiles and wearable electronics & sensors. The  smart textiles and wearable technology market has since grown considerably, with applications in personal health and fitness monitoring, immersive gaming and wireless communications. This has been enabled by the reduction in the costs of sensors, and wireless connectivity with smart devices.

Besides bringing low-cost monitoring and MEMS sensor fusion to devices such as smart watches, the growth in the consumer wearables market has resulted in increased investment in new types of smart textiles and wearables, and their associated manufacturing technologies. There is now increasing demand from consumer electronics, sports and gaming industries for innovative and ever smaller and more flexible new products.

Printed electronics and energy harvesting technologies are evolving to meet the demands of new, wearable formats. Next-generation wearables will rely on active fabrics made by weaving conductor, insulator and semiconductor fibers sparsely into textile yarn. Fabrics woven from such yarns will enable electronic functions that seamlessly integrate into every day, comfortable, lightweight clothing. Sensor tattoos and wearable motion charging devices are now in the early stages of commercialization.

Nanotechnology 

For successful widespread implementation across all markets, next generation wearables must be lightweight, small size, flexible and stretchable, have low power consumption, and reliable sensing performance. The future development of electronics will rely significantly on advances in materials science. Nanomaterials, including one-dimensional carbon nanotubes and nanowires, two-dimensional (2D) materials and quantum dots offer significantly better performance than traditional electronics materials such as organic semiconductors and are easier to process than a-Si or polysilicon.

The use of nanotechnology enables a greater ease of integration of flexible and conductive electronic components into smart textiles and wearable devices. There have been a number of recent research developments in nano-enabled wearable sensors, memory devices, energy storage devices and LEDs that show great promise for commercial application in the next decade. The development of flexible energy harvesting and storage devices is especially important for wearable smart textiles and nanotechnology is key to future development. Textile materials with integrated electrical conductivity are key enablers for smart textiles in sports and work wear, healthcare, and technical applications. At present, conductive coatings or finishes for textiles are used in applications such as conductive mattress covers for surgical tables or electromagnetic radiation shielding fabrics for military applications or work wear. Carbon black is typically used to provide sufficient electrical conductivity, but suffers from drawbacks such as loss of the properties of the textiles. The deficiencies of these and other other materials has led to the development of carbon nanomaterials for next-generation functional fabrics and electronic textiles.

From rigid to flexible and stretchable

Despite considerable R&D investment, most current wearables do not use flexible or printed components; instead they rely on conventional components from mobile devices. Most currently available wearable technology in based on rigid components. Metals and inorganic semiconducting materials such as Indium Tin Oxide (ITO) are intrinsically planar, rigid, and brittle. This greatly hinders the range of wearable applications and as such there is a significant market demand for components that are curved, flexible and stretchable. Integrated circuit (IC)-based wearable devices are unable to maintain intimate and prolonged contact with the curved, soft, and dynamic human body. The development of components that can match the body’s shape and movement is essential for producing new wearable devices with improved functionalities and monitoring of physiological signals.Wearable sensor systems based on flexible and stretchable nanomaterials have the potential to better interface to the human skin, whereas silicon-based electronics are extremely efficient in sensor data processing and transmission.

Therefore, flexible and stretchable sensors combined with low-power silicon-based electronics are a viable and efficient approach for medical monitoring. Nanomaterials allow for a combination of these qualities and are leading to the development of flexible medical devices designed for monitoring human vital signs, such as body temperature, heart rate, respiratory rate, blood pressure, pulse oxygenation, and blood glucose. They have applications in both fitness and sports performance monitoring and medical diagnostics (continuous diagnosis, wound care, drug delivery, and at-home diagnostics).

The development of highly conductive textiles is of crucial importance for minimizing energy loss in wearable devices. Graphene, carbon nanotubes and AgNP/Ag nanowires are the main candidates for fabrication of high-conductivity textiles. Stretchable and flexible transparent electrodes are required to form wearable displays and touch screen panels with comfort designs. Among representative 2-D materials, graphene stands out in the flexible electronics field due to its combination of high electron mobility, high thermal conductivity, high specific surface area, high optical transparency, excellent mechanical flexibility, and environmental stability. CNTs also demonstrate excellent potential. Panasonic has developed a CNT-based flexible stretchable resin films for application in wearable electronics. The stretchable polymer film is composed primarily of epoxy resin and utilizes CNT for an electrically conductive layer.

Figure 2: Panasonic stretchable film.Image credit: Panasonic.

Smart textiles

Wearable technology that measures body parameters (e.g., heart rate, heart rate variability, body temperature, activity levels, etc.) has become increasingly popular. However, the use of smart watches and wristbands to perform these function has several drawbacks for use in medical applications, such as the limited types of bio-signal modality and their accuracy. With the current technology, good signal quality with a dry electrode is only possible when the shirt is very tight to the skin. This is the reason they are in the compression shirts form factor and only being used in sports applications. It is therefore necessary to develop new smart garments that can deliver medical grade data through looser fit, every day clothes. Smart footwear is also a growing area in the medical monitoring market. Spatial and temporal plantar pressure distributions are important and useful measures in footwear evaluation, athletic training, clinical gait analysis, and pathology foot diagnosis. However, present plantar pressure measurement and analysis systems are more or less uncomfortable to wear and expensive. A number of companies are developing in-shoe pressure measurement and analysis systems based on a textile fabric sensor arrays, that are soft, light, and have a high-pressure sensitivity and a long service life.Sensory clothing that is on the market today is mainly focused on athletes and fitness applications. Most of these compression shirts measure the heart rate and acceleration of the body, and sends the data to the wearer’s smart phone. Some garments also measure the electrocardiogram and/or respiration.

Figure 3: <hitoe> nanofiber conductive shirt. Image credit: NTT.

Toray and NTT have developed a wearable sensing device, <hitoe>, incorporating nanofibers. Goldwin, Inc. launched a sportsbra based on the technology in September 2015. The <hitoe> sensor comprised of an electrode made up from combining nano-fibers and conductive PEDOT:PSS that has high electrical conductivity and durability. The garment provides accurate measurement of biodata and also has a high affinity with water and sear, allowing for garment comfort.

Product developers

BonBouton, USA

The company is developing graphene films for sensors in wearable technology. http://bonbouton.co 

Graphwear Technologies, USA

The company has received $50,000 from the DHA, as well as $50,000 from Dreamit Health, in exchange for 8% equity to develop a graphene patch which measures dehydration, glucose, and lactic acid levels, from sweat. SweatSmartTM measures dehydration, glucose, and lactic acid levels, from sweat for application in wearable health monitoring. www.graphwear.co

Nano Engineered Applications, Inc, USA

The company’s platform, “NuumaTM”, is a gas sensor in the form of a chip, based on nanomaterials and capable of detecting airborne gases at the parts-per-billion (ppb) level. The sensors can be incorporated into wearable devices. www.neapplications.com

Imagine Intelligent Materials, Australia

The company has a licensing agreement with Geofabrics Australasia Pty Limited to incorporate graphene coating technology for applications in geotextiles. imgne® X3 is a graphene-based coating that enables enhanced conductivity in textiles. http://imgne.com

Nimbus Materials, Inc.  USA

Start-up developing a Flexible, Ultrathin, Low-cost Composite Thermoelectric Module for Powering Wearables, incorporating carbon nanomaterials. The company’s flexible module could be integrated in to wrist bands for harvesting body heat to augment the battery life or replace the battery. www.nimbusmaterials.com 

References

1. Jia, W. et al. Wearable textile biofuel cells for powering electronics. J. Mater. Chem. A 2, 18184–18189 (2014).

2. Song, Z. et al. Kirigami-based stretchable lithium-ion batteries. Sci. Rep. 5, 10988 (2015).

3. http://pubs.acs.org/doi/abs/10.1021/nl903949m

4. http://pubs.acs.org/doi/abs/10.1021/nl2013828

5. Stretchable Carbon Nanotube Charge-Trap Floating-Gate Memory and Logic Devices for Wearable Electronics, http://pubs.acs.org/doi/abs/10.1021/acsnano.5b01848

6. Superhydrophobic properties of cotton woven fabrics with conducting 3D networks of multiwall carbon nanotubes, MWCNTs, http://link.springer.com/article/10.1007%2Fs10570-014-0422-

Further information
Nanotechnology in Smart Textiles and Wearables

Published by Future Markets, December 2016,  http://www.futuremarketsinc.com/nanotechnology-in-smart-textiles-and-wearables-global-opportunity-markets-applications-technologies-and-companies/

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