Light responsive textiles provide a response to a light stimulus, light is defined by its wave length and frequency as part of the Electromagnetic Spectrum.
Textiles which encounter and react to stimuli are termed SMART Textiles. They are categorised based on the reaction;
- Photochromic- light induced colour changing
- Photoconduction- light affects electrical conductivity
- Photovoltaic- light produces an electrical current
With the term photoreactive meaning reacting to light.
This ability to react to a light stimulus, which is usually in the UV light region, has gained a variety of applications across textiles and apparel. Photochromic effects have gained popularity in novel applications in apparel, such as in clothing that displays a different colour, or applied in a print/pattern which is only exposed in the sunlight. From this application the technology was more finely tuned to act as an indicator of when too much sun (or UV) exposure has occurred, and this applied to clothing and accessories as a safety indicator, gaining particular attention for children’s wear. This same technology has been applied as an anti counterfeiting measure.
Colour change materials are sometimes referred to as chameleon materials, which look at biomimicing the chameleon’s skins to provide reversible colour changes. (Click here for more information)
More information on Chameleonic Textiles is available in the Innovation tab.
In Interiors textiles used as window dressings have been engineered to react to UV exposure and turn opaque or translucent to prevent sun glare.
Harnessing the sun’s energy and converting it into electricity is already a reality through the use of solar panels. However if this same technology can be incorporated into textile it would revolutionise our interaction with current electrical technologies and open up the possibilities for smart or electronic textiles. If textile materials were the power cell for some of the technologies we use on a daily basis, such as our mobile phones or satellite navigation, reducing the weight and bulk of batteries and offering a green and sustainable energy source for the future. Not only in apparel applications but amongst a wide range of technical textile applications, such as roof felting, geotextiles, interior textiles such as window dressings, or in automotive. Even if textiles could only harness a small percentage of the suns energy, because of their large surface area, this small percentage may equate to a substantial amount. It is because of this huge potential to revolutionise that there has been a great deal of interest in the integration of photovoltaic materials into textiles.
A new area of light responsive textiles is emerging for wellbeing. This focuses on the impregnation of textiles, either at the yarn production or fabric finishing stage to embed mineral particles at the micro or nano level. The effect of these particles is that they harness the electromagnetic emissions from the human body and convert them to a level which has a positive affect on the human body by increasing circulation and thus oxygen flow. There has been an emergence of products which claim to possess these qualities; more information is in the Innovations tab.
Photochromic textiles have been used in the fashion industry for novel aesthetical applications such as colour changing garments, but this ability to indicate light exposure has been implemented as an indicator for sun exposure.
Chromism refers to a reversible colour change upon the experience of a stimulus. Photochromic materials display a reversible colour change upon encounter of electromagnetic radiation, the reactive range refers to the specific frequency of the radiation within which a reaction will occur. The scientific principle of how the molecules react to display a different colour is the same of that in thermochromic materials.
The photochromic materials are microencapsulated to allow for the application in textiles. The microcapsules can then be added to textile materials in a variety of ways depending upon the required outcome, screen printing is often a preferred method.
A reversible display of colour change is made possible through a chemical structural change, which in turn alters the perceived colour of the material, UV radiation disrupts the bonds in the atoms, enabling the change in structure. (Click here for more information)
More information on colour change can be found in the Thermochromic area of thermally responsive textiles
Photoconductive materials change their conductive properties based on electromagnetic exposure. This change is usually an increase in the ability to conduct electricity, as exposure to radiation, such as in the UV range, disrupts the molecular bonds, releasing electrons to allow electrical flow.
Bioengineered Textiles and Nonwovens - The Convergence of Bio-miniaturisation and Electro active Conductive Polymers for Assistive Healthcare, Portable Power and Design-led Wearable Technology
The possibility to harness electricity from the sun from textiles has wide ranging and valuable application across a wide range of technical textile market sectors. In technical apparel, PPE?, smart textiles and geotextiles it would offer a no batteries solution to the integration of electrical devices.
There are many different approaches to integrating this technology into textiles, including flexible and non-flexible (although non-flexible has limited application) as well as organic and non-organic. Both the integration of existing photovoltaic cells and the addition of photovoltaic yarns into textiles have been investigated with varying successes.
The Basic Principles are briefly outlined in the video below;
Textile Research Journal; A photovoltaic fibre design for smart textiles
Karma Chameleon: Bragg fibre Jacquard-Woven Photonic Textiles
Progress toward Dynamic Colour-responsive “Chameleon” Fibre Systems
Konarka Technologies are a US based company that produce technologies to harness solar power, in 2009 they released news on photovoltaic wires with potential to be incorporated into textiles.
CORDIS project; Development of Photovoltaic textiles based on novel fibres
Health and Well Being light responsive textiles
Textiles which harness the bodies’ electromagnetic radiation and reflect it back at a range which is believed to provide health benefits such as improved circulation, which in turn reportedly provides benefits such as improved skin tone and reduced cellulite appearance, are gaining increasing interest.
The concept is that the integration of mineral/ceramic materials into fibres and fabrics allows for the absorption of electromagnetic radiation, such as infra red light, and converts it to a range not naturally experienced by the human body for heat and circulation enhancement.
Studies have been undertaken and a large amount of patents have been filed.
Reduction in body measurements after use of a garment made with synthetic fibres embedded with ceramic nanoparticles
Holofibre is a light responsive fibre, launched by Wellman Inc in 2004, claims to absorb visible and infra red light, converting its wavelength to one more easily absorbed by the body to promote increased oxygen content and improve circulation.
Holofibre article 2005
Holofibre rebranded to become Celliant, there is a range of resources available on the website as well as clinical research and case studies.
Schoeller use similar technology in their Energear range.
Schoeller- Energear; The new energy recovery system for textiles