In today’s smart textile world, materials that change color in response to external factors are creating exciting possibilities. Chromic materials may be defined as dyes and pigments that exhibit a distinct color change when exposed to an external stimulus, especially when the change is reversible and controllable. These substances react to different stimuli like heat, light, pressure, pH, chemicals, or electricity by changing their color or appearance. Chromic materials transform textiles from passive materials to active partners—reacting, communicating, and protecting us.
There are smart dyes on the market that change their color according to external environmental conditions. This property earned them the name chameleon fiber systems. Chromic material is the general term that refers to a material that radiates color, erases color or changes color in response to the induction caused by external stimuli. Chromic is a suffix that means color. Chromic materials are used to create interactive, functional, and fashionable textiles. Chromic materials making them crucial for both fashion innovation and technical textile applications.
Let’s explore the different types of chromic materials and how they are used in the textile industry.
Types of Chromic Materials in Textile Industry
Chromic materials are classified based on the type of stimulus that causes them to change color. The classification of stimuli for chromic materials in textile industry is as follows:
- Photochromic: external stimuli energy is sunlight.
- Thermochromic: external stimuli energy is heat.
- Electrochromic: external stimuli energy is electricity.
- Piezorochromic: external stimuli energy is pressure.
- Solvatochromic: external stimuli energy is liquid.
- Carsolchromic: external stimuli energy is electron beams.
Generally, the color changes that take place are as follows:
- Black, blue, red, burnt orange and dark green become colorless.
- Light green and orange become yellow.
- Purple becomes pink.
1. Photochromism
Photochromic colors are plastisol-based, off-white PVC particles suspended in a liquid that can be applied to fabrics by painting them on, spraying them on or screen-printing directly onto the garment and then cured at 150ºc for thirty to ninety seconds. The change of color is activated by sunlight or UV radiation, which causes a change to the molecular structure and causes the photochromic dye to release high-density colors, including various shades of blue, green, orange, red, yellow and black. Other ordinary colors can be added to the photochromic dye to provide a variety of shades during the color change.
Photochromic pigments can be placed as solution in microcapsules that are embedded in fibers during extrusion. They can also be mixed with a binder, such as an acrylic base, to form the print solution that is placed on the fabric. This process can create pictures that change color.
There are fibers that emit fluorescent color – for example: red, green and blue become fluorescent under ultraviolet radiation in dark places, but each one maintains its original color when exposed to natural light. The inorganic fluorescent paints used for this purpose are mixed at an approximate rate of 10% paint and 90% liquid during the spinning operation. It is important to note that the color can be controlled freely by mixing various inorganic paints together or by adding paints to the natural colors of fibers.
Photochromic dyes are used in the fashion, furnishing and packaging industries. They are important for optical switching data transference and imaging systems. They are used in glasses, photochromic or Reactolite lenses, to protect one’s eyes from bright sunlight.
2. Thermochromic:
Thermochromic materials are those whose color changes as a result of encountering heat, especially through the application of thermochromic dyes whose colors change at particular temperatures. Two types of thermochromic systems that have been used successfully in textiles are liquid crystal and molecular rearrangement. In both cases, the dyes are contained in microcapsules and applied to garments or fabric like a pigment in a resin binder.
The most important types of liquid crystal for thermochromic systems are the so-called cholesteric types. Adjacent molecules are arranged so that they form helices. Thermochromism results from the selective reflection of light by the liquid crystal. The wavelength of the light reflected is governed by the refractive index of the liquid crystal and the pitch of the helical arrangement of its molecules. As the length of the pitch varies with temperature, the wavelength of the reflected light is also altered, and color change results.
An alternative means of inducing thermochromism is by rearranging the molecular structure of a dye by changing the temperature. The most common types of dye, which exhibit thermochromism through molecular rearrangement, are spirolactones although there are other types used. A colorless dye precursor and a color developer are both dissolved in an organic solvent. The solution is then microencapsulated; it is solid at lower temperatures. Upon heating, the system becomes colored or loses color when it reaches the melting point of the mixture. The reverse change occurs at that temperature if the mixture is cooled. These dyes were originally used for fun applications, and they were very prevalent in children’s clothing during the 1980s and 1990s but also appreciated by adults for their technical properties.
In order to establish these dyes in everyday life, it has been necessary to improve their endurance to light and their accuracy. One application of the thermochromic dyes are used as warning indicators in Babygrows; a pub owner designed the addition of the thermochromic dye to these garments so the color change indicates if a baby has a fever or a high temperature. It took six years to develop the ink pigment with heat-sensitive molecules embedded in a cotton fabric. The Babygrow garments come in blue, pink and pastel green, and they turn white when the baby’s temperature rises above 37ºc. As the temperature drops, the fabric reverts to its original color so new or experienced parents can visually see whether medicine or treatment of a cool flannel is working. Such garments are especially important for babies at risk for cot death.
3. Piezorochromic:
Piezorochromic materials are smart substances that change color when mechanical pressure, stretching, or compression is applied. In the textile industry, these materials are used in smart sportswear, medical textiles, and protective clothing to visually indicate stress or pressure. They help monitor muscle activity, detect excessive pressure in medical wraps, and warn of material strain in industrial wear. Fashion designers also explore them for interactive, touch-sensitive garments. Though still in early development, piezochromic textiles promise innovative applications in healthcare, sports, military, and wearable technology as research into durable and flexible smart fabrics progresses.
4. Solvatochromic:
Solvatochromic materials change color when they come in contact with a liquid or gas. They are often used for designer swimsuits. However, they are also being developed to monitor health – for example, they can evaluate changes in one’s perspiration in terms of pH, ionic and strength, for instance, which can lead to more effective treatments.
5. Electrochromic:
Electrochromic materials change color via an electrical current. Electrochromic materials were developed by Gregory Sotzing and Michael Invernale who coated yarns with varying charges of an electrochromic polymer, such as inorganic oxides of cobalt oxide or nickel oxide, and wove it into the fabric. They then added flexible, electrical, conductive fibers and attached them to a small battery held in the product. The differing voltages change the color of the product due to oxidation and reduction in the electrochromic material. It can be used to create flexible information display boards, reusable price tags and camouflage materials for the military. There are plans to develop the product for use in everyday apparel, which would change the color of a suit, dress or shirt from day time to evening use without going home!
Some materials have paints applied to them that store light. They are used in working clothes for those who do road constructions or repairs in poorly lit areas. They can also be used to create glowing arrows on carpets that guide people to exits during power failures. Beyond those important uses, chromic materials can be used for fashion; designers can be very creative producing other-worldly garments that change color depending on the volume of incident light.
6. Carsolchromic:
Carsolchromic materials are color-changing substances that respond to the presence of specific chemicals or solvents. In the textile industry, these materials are used to develop smart fabrics that change color when exposed to certain liquids, vapors, or chemicals. Applications include protective clothing for chemical industries, where fabrics visually signal contact with hazardous substances, and medical textiles to detect body fluids or contamination. Carsolchromic textiles also find use in environmental sensing fabrics and interactive fashion. Though still under research, they offer exciting potential for creating responsive, safety-enhancing, and visually dynamic textile products for specialized fields.
Conclusion
Chromic materials have opened up exciting opportunities in the textile industry by merging fashion, functionality, and technology. The integration of chromic materials into textiles is transforming the industry, enabling fabrics that are not only visually striking but also highly functional and responsive. As research advances, the range of chromic effects and their applications in both fashion and technical textiles will continue to expand, driving innovation at the intersection of science, technology, and design
