Improving the Performance of Human Body
with Far Infra-Red Rays Reflecting Textiles
Wool Research Association - Center of Excellence for Sportech, India
Submission: September 07, 2018; Published: October 16, 2018
*Corresponding author: Mayur Basuk, Assistant Director, Wool Research Association - Center of Excellence for Sportech, Maharashtra, India, Thane- 400607, Tel:+91-9699821340/+91-22-2586-8109; Fax: +91-22-2531-8365; Email: email@example.comfirstname.lastname@example.org
How to cite this article: Mayur Basuk. Improving the Performance of Human Body with Far Infra-Red Rays Reflecting Textiles. Curr Trends Fashion Technol Textile Eng. 2018; 4(3): 555640. DOI: 10.19080/CTFTTE.2018.04.555640
All living organisms are subjected to the natural electromagnetic radiation reaching the earth from the sun. Living organisms experience the beneficial as well as adverse effects of it at all levels, starting from sub-cellular organelles and ending with the whole body. Nowadays, specialty FIR emitting heat lamps and garments made up of filaments (fibers) impregnated with FIR emitting nanoparticles are becoming used to deliver these thermal radiation effects. The Present paper explores the use of FIR in textiles, test method, Present status for far infrared reflecting textiles and global market along with future innovations in the field.
Keywords: Far infrared radiation; Blackbody radiation; FIR test methods; Global market; FIR Emitting ceramics; Fibers
Protection against extreme weather, especially cold, has been primary purpose of clothing and heating/warming fabrics serve just the purpose. In spite of several challenges in smart fabrics and commercialization of new technologies, there is sense of optimism, thanks to the advent of technologies aiming to perfect the heating and /or heat retention technologies. Manufacturers and innovators have been tirelessly working on to improve the capacity of fabrics or garments to provide maximum comfort in winter. Evolution of various technologies and strategical combination of technologies has made it possible to have different solutions for different conditions.
Far infrared (FIR) radiation (λ=3-100μm) is a subdivision of the electromagnetic. Thermal radiation (or infrared) is a band of
energy in the complete electromagnetic spectrum and it has been used effectively for millennia to treat/ease certain maladies and discomforts. With the development of better technology to deliver
pure far infrared radiation (FIR), the benefits from its effects have widened. Technological advances have provided new techniques for delivering FIR radiation to the human body. Specialty lamps and saunas, delivering pure FIR radiation (eliminating completely the near and mid infrared bands), have become safe, effective, and widely used sources to generate therapeutic effects. Fibers impregnated with FIR emitting ceramic nanoparticles and woven into fabrics, are being used as garments and wraps to generate FIR radiation and attain health benefits from its effects .
With respect to the complete electromagnetic radiation spectrum, the infrared radiation (IR) band covers the wavelength
range of 750nm-100μm, frequency range of 400 THz-3 THz,
and photon energy range of 12.4meV- 1.7eV. It lies between the long wavelength red edge of the visible and the short edge of the terahertz (starting at 3THz) spectral bands (Figure 1).
The classification of the International Commission on Illumination (CIE) has three sub-divisions for the IR radiation as given in Table 1. An alternative classification provided in ISO 20473
standard for the sub-division of the IR ranges is given in Table 2.
In the IR radiation bands, only FIR transfers energy purely in the
form of heat which can be perceived by the thermoreceptors in
human skin as radiant heat . Not only is FIR absorbed by the
human body, but it is also emitted by the body in the form of black
body radiation (3-50μm with an output peak at 9.4μm).
It is difficult to perceive a world without innovation. The
essential benefit of development is a better world and a safer
life. There are instant solutions to all problems and the solutions
are far simpler today. Industrial sector constantly develops ideas
and products that serve the society at large. In the textile sector
too, innovation has brought forward dramatic changes and this
transformation is still running its course. With mercury steeply
going down in the Northern hemisphere, the market for winter
clothing is warming up. The advancement in textile has ensured
that there are many high performances winter clothing to combat
the dropping temperature. The Far Infrared (FIR) fibers in textile
are among many innovations that use heating elements in cold
weather clothing. FIR is also an integral part of therapeutic
segment of clothing.
These fabric technologies utilize IR rays (wavelengths ranging
between 700nm to 1mm) for Sunlight’s electromagnetic radiation
or body heat for thermoregulation when the temperature around
body is low (Figure 2). IR has three broad categories, Near
Infrared, Mid-Infrared and Far Infrared. While IR radiation is more
often defined by the heating function, Far Infrared has specialized
function (discussed in the next section). Many fabrics have
been developed enable with IR radiation capabilities. The main
additives imparting IR capability are ceramics, trace elements,
metal oxides, etc. These materials have common characteristics
of being able to absorb and store heat (i.e. high heat capacity) and
release it when the surrounding temperature is low. Both yarn
inherent and print versions are available in market for imparting
IR emitting property to the fabrics. A different approach has also
been taken to reflect IR radiation (generated by our body), thus
preventing heat loss when in cold conditions.
Although not typically heating technology, but FIR (higher
wavelength section of IR spectrum) is often used in fitness and
recovery applications owing to its ‘internal heating’ capability.
The user does not necessarily experience heat by FIR radiation.
Far infrared (FIR) radiation (λ=3-100μm) is a subdivision of the
electromagnetic spectrum that has been widely studied for its
biological effects (Figure 3). With the evolution of technologies
to be able to filter specific wavelength range e.g. far infrared
radiation (FIR), it has been made possible to achieve benefits of
the radiations selectively. Nowadays, specialty FIR emitting heat
lamps and garments made up of filaments (fibers) impregnated
with FIR emitting nanoparticles are being used to deliver the
thermal radiation effects. At the cellular level, the electromagnetic
radiation interacts with living cells by altering cell membrane
potentials and mitochondrial metabolism. FIR energy (photons
with quantum energy levels of 12.4meV-1.7eV) is absorbed by
vibrational levels of bonds in molecules. The energy levels so
reached lead to expansion of blood vessels, thinner body fluid and
increased hydration capacity of water molecules.
Hygroscopic heating refers to generation of heat by absorbing
moisture. Many polymers have the tendency to absorb moisture
and the process of moisture absorption leads to heat generation
(an exothermic process). The heat generated is termed ‘heat
of absorption’ or ‘absorption heat’ and is an outcome of bond
formation between water molecules and the yarns’ polymer
chain. Different yarns have different water absorption capabilities
and the amount of heat generated can be different for different
polymers owing to different chemistries. Some manufacturers
have made efforts have to increase the absorption by chemically
modifying the polymer and increasing the binding sites for water.
In general, cotton, wool, rayon, etc. Fall in this category and
have been used extensively for harnessing moisture to generate
warmth to the wearer.
While different methods have been discussed above to
actively utilize different heat sources (e.g. body heat or external
IR sources) as well as indirect heating (e.g. hygroscopic), the basic
idea of conserving body heat by just creating a barrier for heat
exchange with exterior still holds its value. Maintaining a still air
microenvironment next to skin is one effective way to contain the
warmth around body, as the air serves as an insulating layer. High
gauge construction methods and hairy fibers (e.g. wool) serve the
purpose in this aspect.
Some other strategic constructions have also been tried with
varying success, as discussed further in the article.
Clothing insulation is an important aspect of fabric
performance as far as warm conditions are concerned. The
capacity of the fabric to retain heat depends on several factors and
its quantification has been a challenging exercise. CLO, or Clothing
Insulation, is the measure of fabric’s (or garment’s) capacity to
retain wearer’s body heat and make her/him comfortable. While
a CLO value of 0 represents naked person, CLO value of 1 is the
amount of insulation that allows a person at rest to maintain
thermal equilibrium in an environment at 21 °C (~70 °F) in a
normally ventilated room (0.1m/s air movement). Above this
temperature the person so dressed will sweat, whereas below this
temperature the person will feel cold. CLO values can be assigned
to fabrics, garments as well as ensembles of garments. The below
Table 3 is general (neither standard nor extensive) representation
of different garments’ CLO values.
Apart from the material and fabric construction, important
factors determining insulation include posture and activity of the
wearer. As mentioned earlier, CLO is represented as with respect
to a person at rest in a controlled environment, so a walking or
running person will experience different insulation by the same
fabric/garment than being immobile. In general, body motion
decreases the insulation of a clothing ensemble by increasing
air movement through spaces between yarns in the fabric and/
or causing air motion within the garment. This effect varies
considerably depending on the nature of the motion and of the
fabric. This is why, an accurate estimates of clothing insulation for
an active person is very challenging. In a nutshell, the specifications
and requirements for each garment will depend on the season as
well as end use of the garment (Figure 4).
There are different ways to retain body heat next to the skin,
by creating a micro-environment. Most of the strategies are
focused around interfering in the exchange of heat or air (which is
supposed to transfer heat by convection) between the two sides of
the garment. Some of the methods have been listed below.
Retained air inside the hollow yarn as “temperature cushion”
Going down to the yarn/fiber level, the trapped air helps in
maintaining a microenvironment with still air that serves as
an insulating barrier for heat exchange between its two sides.
Apart from assisting in heat retention, hollow yarns also help in
maintaining the lofty and heavy look without contributing a lot to
the fabric weight (Figure 5).
Spacers are two or more layers of fabrics connected by
filament yarns traversing between the layers as bridges.
Spacers have been tried out for various applications, mostly
to replace foam and heavy fabrics for insulation. The capability to
hold air in space between its two (or more) layers imparts spacers
the ability to insulate heat across its thickness. The disadvantages
of using spacers have been the drape and thickness of the
fabric. Most of the times, the garment ends up with space suit
like appearance, due to the stiff nature of connecting filaments,
a prerequisite in maintaining the spacer structure. Softer
connecting filaments have been tried but that compromises the
spacer structure, leading to instability of the air-pockets and so
reduction in heat retention (Figure 6).
As mentioned earlier in this article, yarns with hairy surface
contribute to heat retention by disturbing the passage air flow.
This property, along with hygroscopic heat generation, has made
wool the material of choice for winter wear. Other yarns, including
polyester, have also been modified to achieve some level of heat
retention by hindering the air passage, e.g. spun yarns, ATY, yarns
with varied shrinkage, etc.
In line with blocking or disturbing the air passage, various
attempts have been made to develop warming fabrics structures
by quilting. Garments with down and other fills have been very
successful as they are able to not only block the cold waves from
outside but also aid in heat retention by keeping the warmth inside
the garment, again by creating the still air micro-environment.
It has been widely understood that layered fabrics are able to
retain more heat than single layer of thickness equal to all the layer,
added together. This advantage is achieved by the still air retained
between the layers in the arrangement. Additionally, different
layers perform different functions based on their position. Usually
at least three layers are identified as follows:
1) Inner Layer (also called base layer or first layer): Usually
with the soft hand feel, this layer is designed to provide
comfort by keeping the skin dry.
2) Mid Layer (or insulating layer): this is where warming/
heating function is imparted. The fabrics with inherent
heating properties (dry heat or hygroscopic heat generation)
are usually slotted in the mid layer. A heated layer not only
helps to create a warm microenvironment but also helps in
insulation by disturbing the energy (heat) gradient across its
3) Outer Layer: Also called Shell layer, it works as protection
over the other two layers. For heavy winter applications,
waterproofing/repellency has been recommended to ward
off snow or water coming in contact with the garments’ outer
surface. Another layer of insulation is provided by this layer as
air is held between mid- and outer layer.
In recent past, interdisciplinary research has made it possible
to generate heat by external sources, e.g. powered systems, to
heat up the garments or parts of a garment (Figure 7). Different
components have been made to heat up and make the wearer
feel comfortably warmed up in extreme cold conditions. Jackets,
gloves, balaclavas, and various other products are available
in the market which can heat up, using a power source, to a
desired level to provide comfort from cold exterior conditions.
The heating is achieved by many methods, dominated by use of
conductive yarns. Conductive yarns are many based on core-shell
structure with polyester (and other polymers) core providing the
mechanical properties while the metal shell (usually copper) is
meant to conduct heat across its length. The yarns are integrated
into the fabric either by weaving or by embroidery, special
arrangements need to be made to knit the yarns into the fabrics.
The challenges include yarn breakage, bending limitations for
metal yarns, need of insulation, etc. Insulation is often addressed
by adding another membrane of coating on the conductive parts
of the fabric. Some new advancements have been to reverse the
core-shell arrangement, having metal in the core and polymer
in the shell (something like regular wires, but at a small scale
of yarn thickness). Other methods include use of carbon fibers,
conductive prints and membranes, using graphene, although they
are in early stages of their application.
PCMs, or phase change materials, draw special attention when
it comes to thermo regulation. Phase change materials are able to
regulate their surrounding temperature by changing their phase
at specific temperature. The most common example is ‘water’. At
its freezing point, i.e. 0 °C (or 32 °F) water transitions between
liquid and solid phases, converting to liquid (water) above and to
solid (ice) below this temperature. For practical applications in
textiles, the temperature needs to be around body temperature.
The phase change that is suitable for textile application is ‘solidliquid’
phase change which takes place at its melting point.
The energy exchanged in this process is called ‘heat of fusion’
Commercially, most common materials used are paraffin or short
chain lipids, which have wide range of melting points depending
on chain length. Manufacturers are able to tailor the melting
points by controlling the chain lengths (Figure 8).
Other materials used as PCMs are some carbohydrates,
salt hydrates, etc. There are also solid-solid phase transitions
(between crystal lattice structures) found in some materials,
leading to significant amount of heat. Textile industry however
has been limited to using liquid-solid transition of materials for
practical reasons. PCMs are loaded into fabrics in three different
ways: at yarn level (for synthetic yarns), as fabric coating, and as
fabric treatment (usually involving PCM loaded nanoparticles)
wherein the material reaches and binds to individual fibers/
filaments in the yarn. PCM usage has met with many challenges,
specially related to loading efficiency and saturation (once the
phase transition has taken place and no heat exchange can take
place). Saturation can be delayed by increasing the loading
which is limited by loading capacity of the micro/nanoparticles
or mechanical strength of the yarn (in case of yarn loading).
Attempts have been made to increase PCM loading in particles by
reducing the wall thickness, thus increasing the core volume. This
requires shell to have additional strength which was achieved
by crosslinking, mostly by formaldehyde. Concerned by health
concerns, many manufacturers have successfully attempted to
increase the particle stability by alternative cross-lining agents.
A combination of polypropylene and special lead-free bioceramics
is used to create these fibres. The ceramic is responsible
for emitting the far infrared rays. The basic structure of this fibre
is based on the fact that energy emission is part of human body.
The bio-ceramic converts thermo energy of human body into far
infrared rays that generate deep but gentle heating. The health
benefits of FIR textile range from keeping wearer’s body warm,
restoring physical function by getting rid of fatigue, relieving
muscle pain, using to ease pain of arthritis and bronchitis. Such
type of textile fabric also boasts of anti-bacterial and deodorantlike
properties. All these features make far infrared fabrics
suitable for health care products. The markets are already selling
FIR trousers, undergarments, knee pads, nursing neck and
stomach, socks, cushion, bedspread, bedding and shoulder pad.
FIR clothing also proves to be a boon to regular joggers, athletes
and defense personnel during cold weather .
The infrared concept has long been rooted in the cultures
related to the Asian domains. Asian therapies often emphasise
importance of blood circulation for well-being. Chinese Qi Gong
is known to advocate this theory. Though, other products like
infrared heat lamps etc. were easily available in market, FIR
clothing is a comparatively new development. FIR fibre was
developed by a Californian company in 2003. Since then, many
brands have been launched in the global market. The fabric has
already proved its mettle in field of extreme sports. International
sports brands are also taking keen interest in developing special
range of sports gear that can give promising performance during
colder temperatures. Medical fraternity too has shown support to
this fabric for use in diabetic foot care, bedding and mattresses.
Brands are also promoting shapewear and sliming lingerie
designed on far infrared mechanisms. The first company to launch
FIR textile Hologenix has recently announced its collaboration
with Puma on a line of men’s athletic apparel inspired by Olympian
Usain Bolt. Hologenix’s FIR fabrics have found a place in markets
of United States, Taiwan, South Korea, etc. One of the commercial
versions of FIR-emitting textiles for apparel was marketed by
the French company HT Concepts. The move has expanded the
reach of infrared technology into several sectors, such as fashion
apparel, bedding, and technical accessories that include helmets
and automotive seating. Among the latest innovation in FIR, Swiss
company Schoeller’s version of FIR reflecting technology has
been applauded worldwide. The company’s fabric uses titaniummineral
matrix that can be integrated into membranes and
The energear textile technology was developed in 2010
for Schoeller textiles and is now available for diverse markets.
energear can be integrated into textiles in different ways such
as through membranes and coatings. According to Schoeller,
to harness the benefits of this technology for a textile print, a
minimum of 30% of a shirt or other garment can be finished with
the laundry-permanent energear print. Schoeller Technologies
has also developed some design suggestions for the purpose
and depending on the blend, the printing paste with energear
results in a grey to silver-metallic look. Schoeller says the process
is generating enormous interest in various areas and is officially
launching at Outdoor. First consumer products in Schoeller
fabrics will be available beginning this summer from, among
other brands, Alberto (golf pants) and Bugatti (lifestyle jacket).
Schoellers FIR expertise was applauded by Lee Davis, race car
driver and founder of Luna C Clothing for auto racing. In one of
his interviews, Davis vouched for FIR fabric’s high-performance
stating that the technology captures the far infrared rays and puts
them back into the body, which results in higher concentration
and focus, a lower pulse rate and lowers the time body takes to
recover. Schoeller has launched a variety of technical fabrics
based on FIR technology. The outerwear range includes denim,
water-repellent viscose or polyester blends for outerwear and
wool blends .
The far infrared textile processing includes mixing of raw
materials, coating, lamination and submerging. As products made
of mixing of raw materials deliver the same durability of the fiber,
the wash-resistance test would not necessary. For products come
of coating, lamination and submerging processes will have to have
the 10 times wash-resistance test based on AATCC 135 (1) (III)
(A) iii prior to conducting the performance test. The performance
test is conducted in ambient temperature and the criteria are
given as below:
This test determines the fabrics capability to generate heat
merely by absorbing moisture (heat of absorption). The test
involves measurement of fabric temperature, kept on the plate,
while relative humidity is increased from 10% to 90% in a
chamber with controlled temperature of 20 °C. The test has been
developed by GAP and for a fabric to be categorized as hygroscopic
heat generating fabric, the rise in temperature must be 2 °C more
than the control (similar regular fabric or blank).
While there is no standard test for measuring dry heat (not
hygroscopic) generation, most innovator study the performance
by using a heat source (e.g. 500W halogen bulb) set at a fixed
distance (equidistant) from the control as well as experimental
fabric and measuring the temperature of the fabrics at set time
points, using temperature sensors. For consistency of the study,
the experiment must be performed in the controlled environment
(temperature, relative humidity, etc.). The test is often extended
to cooling phase as well, i.e. measuring the temperature when the
heat source is turned off. This gives an idea of fabrics property
to retain heat . Test methods used for the evaluation of the
performance of Far Infrared textile are illustrated as Table 4.
Aging population, record breaking temperature in winter and
increase in purchase by urban population, are some of the reasons
that back FIR fabric. The growing need of this fabric has led to
market expansion of functional fabrics in China and Taiwan. In
recently concluded Autumn-2014 edition of Intertextile Shanghai
Apparel Fabrics held in China, FIR was among the most soughtafter
functional fabrics. China has entered third grade research on
high stimulation differentiated fibres including far infrared. The
United States, Europe, Australia, etc. import far infrared textile
from Taiwan, China and other countries to meet the rising demand
of the fabric Table 5.
The emphasis of textile companies is now on increasing
performance and enhancing function of far infrared textile.
Technical textile manufacturers are generally in good shape, the
fact which indicates easy flow of funds into further research and
development of far infrared products. The fabric has already
entered the world of fashion and the acceptance is humbling so
far. Continuous innovation has made this textile a rage across the
world and leading companies along with international brands
are diversifying FIR textile further, which is expected to lead to
growing awareness and acceptance among prospective consumer
Far-infrared is one band of the solar electromagnetic lightwave
ranging in wavelength from 3μm to 1000μm. Far-infrared
textiles are made with blends of polymer and Nano- or microceramic
powder spun together with synthetic cotton, natural
cotton and other fibers to make yarns and fabrics. Far-infrared
materials can also be added during after treatment of an ordinary
fabric. Far-infrared textiles absorb sunlight, or heat from human
body, and pass the far-infrared – wavelength 4 to 14μm – back to
the human body. This specific range of far-infrared is reputed to
be most useful to the human body and is called “the rays of life”
or “biogenetic rays.” When far-infrared rays strike the human
body, their frequency is consistent with that of the body’s cellular
movement. Far-infrared materials are particularly effective during
activities in High Mountain and snowy areas. If it can be proved
that non-heating FIR has real and significant biological effects,
then the possible future applications are wide ranging. Not only
could bandages and dressings made out of NIR emitting fabrics
be applied for many medical conditions and injuries that require
healing, but there is a large potential market in lifestyle enhancing
applications. Garments may be manufactured for performance
enhancing apparel in both leisure activities and competitive
sports areas. Cold weather apparel would perform better by
incorporating FIR emitting capability and sleeping environments
could be improved by mattresses and bedding emitting FIR.
The review study is the part of the R & D project sponsored
by Ministry of textiles, Govt. of India. The author of this paper
is thankful to the Director and Management of Wool Research Association, Thane for giving their unremitting support and