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New research and applications are proving that color-changing smart textiles continue to offer viable technology and products in the smart fabrics marketplace. Most recently, researchers from the School of Information, University of California, Berkeley, have developed a new color-changing “smart thread,” Ebb, that turns fabric into a computerized display. According to information provided by the school, the smart fabric could be used to create clothes or other textile products with dynamically changing colors or patterns.
The research process has sparked a number of application ideas:
- A shirt links to a Tinder profile that changes color when someone who is “swiped right” is nearby.
- A striped scarf offers real-time bus information; the stripes fade one by one, indicating the number of minutes before the bus arrives.
- A shirt with a slogan updates automatically to match the wearer’s Facebook status.
- With one shirt, the wearer customizes colors or patterns for many days.
- A watch is woven directly into the cuff of the garment.
For the initial research project, the team used the smart thread to create seven different crocheted and woven fabric swatches. The core technology of Ebb consists of conductive threads individually coated with thermochromic paint. When electricity is supplied to the threads, they heat up and gradually change color.
The research team was led by Ph.D. student Laura Devendorf, an artist, designer and computer scientist with degrees in both computer science and visual art. Her research explores the challenge of designing machines to support human creativity. She was assisted by Ph.D. student Noura Howell, who is experimenting with biosensing and human-computer interaction, and supported by Kimiko Ryoka, associate professor at the School of Information and Center for New Media, who teaches courses on interface aesthetics and theory, and the practice of tangible user interfaces.
The Berkeley team worked with researchers from Google’s Advanced Technology and Projects (ATAP) group, an in-house technology incubator. ATAP’s Project Jacquard is a platform for embedding sensors and feedback devices in fabrics and clothing in ways that seem natural and comfortable. The platform encompasses techniques for creating fashion fabrics with conductive fibers woven into them, plus small, flexible, computing components and feedback devices (such as haptics or LEDs), along with software application program interfaces that can be used to exchange data with the garment.
Although Project Jacquard is exploring a variety of approaches to wearable computing, the current technology isn’t suitable for wide-scale use. Research on Ebb was useful for sparking ideas and uncovering how wearers may feel about computerized clothes.
Thermochromatic versatility
Chameleon International commercialized its thermochromatic product a decade ago. President Debra Aperfine says that in 2001, Chameleon partnered with companies, such as custom film manufacturer Wiman Corp., that were also determined to develop thermochromatic materials with color that can change by the touch of a hand.
Quite simply, these materials function by changing color when a designated temperature is reached and reverting back to the original color when the temperature returns to “normal.” Today, the Oakridge, N.C.-based company offers advanced engineered color-changing material solutions through its patented products. Since the first successful production in 2006, the technology has evolved quickly, and the company now offers a range of customized film, sheet, laminated and coated textiles using its technology.
Aperfine emphasizes that the company uses the highest quality raw materials to ensure a safe and accurate color transition. “Our team is dedicated to delivering new and innovative color-changing materials specific to our partners’ applications, and to extend the marketability of current products,” she says.
A versatile approach
The company is the exclusive manufacturer of the patented product Chameleon ChroMyx™, a line of temperature-sensitive, color-changing sheet film material that’s flexible, scuff- and scratch-resistant and waterproof, and can be formed into many products.
The company’s technology has “the ability to integrate color-changing properties into the polymers to produce membranes, flexible films, sheet and laminated textiles in very low-gauge or in heavier-gauge materials utilizing diverse manufacturing capabilities and various polymers,” Aperfine says.
Chameleon offers products in thermoplastic polyurethane, non-phthalate polyvinyl chloride, polyethylene, polypropylene, thermoplastic olefin (TPO) and thermoplastic elastomers (TPEs), to name a few. The color-changing properties are durable and cannot be washed out or scratched off. Chameleon produces products that can be cut, sewn, high-frequency welded and printed.
Although the company produces interactive, touch-activated products, it also develops functional materials to be used as warning signs, safety indicators and medical alerts. It conducts ongoing research in medical concepts for visual indicators that occur when temperature changes are indicative of a change in a patient’s medical condition.
Material solutions for heat and cold therapy as indicators for specific therapy temperatures have also been developed, and the company has collaborated on the development of a patch to indicate overheating. As such, Chameleon’s products are used in pediatric hospitals and exam rooms to help create a more relaxing atmosphere for children. Chameleon’s products are also used to help special-needs children focus or to encourage them to exercise their hands. The technology is also used in manufactured end applications for sensory therapy for both children and adults.
In 2014, Chameleon launched a line of products incorporating the company’s patented technology in the craft and hobby market. Chameleon Skinz™ is a color-changing, temperature-sensitive, touch-activated tape offering an interactive medium for adults and children to use in creating and designing crafts. In 2015 a multi-color, multi-temperature heat transfer film was introduced.
Beyond plastic
Sommers Plastic Products Co. Inc., Clifton, N.J., has also been using thermochromatic liquid crystal technology in polyurethane fabrics since 1998. In fact, company president Fred Schecter points out that thermochromatic materials were used long before applications in fashion; one early use was mammography for detecting breast tumors. Typically a tumor will appear as a “hot spot,” indicated by a color change on the material.
“Liquid crystal technology incorporates a fascinating molecule that remains in liquid state and twists when heated, thereby creating a prismatic effect on light reflecting through the crystals,” Schecter says. “Derived from lanolin, or sheep’s wool grease, this substance has many useful applications.”
The challenge, Schecter says, was learning how to combine two of the main ingredients considered unmixable (like oil and water) and overcoming external factors that weaken the color-changing molecules, including UV rays and oil from skin, which can degrade the “springines” of the molecule, dulling the color-change effect.
Living rubber
Schecter says Sommers Plastics was the first company to coat 54-inch-wide polyurethane fabric with thermochromatic liquid crystals. “Living Rubber,” trademarked in 1997, was introduced via two manufacturers: fashion designer Norma Kamali in New York City and Lip Service Jeans in Los Angeles. Although it was an instant success, there was a major setback in the beginning.
“I received a phone call from Lip Service that many of the expensive ‘mood jeans’ were being returned due to delaminating,” he says. “The clear polyurethane top coat was peeling in the areas of stretch and stress.
“Liquid crystals are organic in nature, and any coating on our polyurethane surface needed to be sealed in with a top layer of clear polyurethane, like putting Saran™ Wrap on butter. However, applying this layer was more like putting Scotch™ tape on Vaseline®. It seemed to work fine at first, but after a short while the bond broke.
“We came up with a method of microencapsulating the crystals and blending this in with the master batch of PU (polyurethane),” says Schecter. “Problem fixed.”
The company uses two types of thermochromatic liquid crystals in creating its products. “Liquid crystals change a dark color when warmed through a spectrum; black goes to brown, then green and blue,” he says. The other type, leuco dyes, creates the product called “Popper,” a polyurethane-coated textile with more dramatic color changes.
“The surface color, opaque at room temperature, becomes transparent when warmed, exposing the underlying color or ‘peek-a-boo’ print below,” he says. “A brown, leather-like attaché, let’s say, turns bright green when warmed. Popper can have three layers of colors, each tweaked to change at different temperatures.”
That workable solution resulted in additional volume business with brands such as Puma and Calvin Klein.
Sommers’ thermochromatic materials are used primarily as novelty items, but these materials can have practical end uses and have been used or considered in a range of applications and markets, including for temperature indication for household and medical uses; battery testers; medical thermography; radiation detection; non-destructive testing and thermal mapping; aerospace and engineering research.
Maura Keller is a freelance writer and editor based in Plymouth, Minn. Janet Preus is senior editor of Advanced Textiles Source.