Textile Insight

hermal comfort or "wear com- fort" has been identified as one of the most fundamental needs demanded by today's consumers. While a great deal of successful development has individually addressed cold-weather wear and warm-weather wear, the challenge now is to create a fabric that can effectively work in both warm, humid temperatures as well as in cold weather environments. A research team, headed by Yi Cui, Professor of Materials Science and Engineering at Stanford University, is well on its way to solving this problem. The idea for the project came out of Cui's interest in saving energy, and his expertise in manipulating nanoscale materials. Since 13 percent of all energy consumed in the U.S. is devoted to indoor temperature control, he believes that energy used for air conditioning and heating could be saved if people could be made comfortable in a variation of temperatures. Cui's team of Ph.D. students and postdocs began developing their smart thermal textiles to address the issue in 2014. The first part of the project involved infrared-reflective textiles for heating. In 2016, Part Two of the project demonstrated infrared- transparent textiles for cooling. "After these projects, it became very clear that radiation heat transfer control is very different and unique compared with the traditional design of conduction and convection. So, we began manipulating the radiation property to give new functions to textiles," says Cui. Dual-Mode Fabric Construction By stacking two layers of material with different abilities to release heat energy, sandwiched between layers of cooling polyethylene, the team realized that the controlled radiation could work both ways and address a range of temperature changes. "The dual-mode textile consists of a copper and carbon bi-layer thermal emitter (10 microns thick in total) embedded in infrared-transparent nano- porous polyethylene (nanoPE)," explains Cui. "The reason behind this choice of materials is to create the asymmetry for heat transfer and achieve the dual-mode. The textile is non-woven at this stage, but we are developing the woven version by fabricating nanoPE fibers/yarns." The copper coated side of the fabric traps the heat between the polyethylene layer and the skin, while the carbon coated side releases heat under another layer of polyethylene. When the copper layer faces out, the material traps the heat and warms the skin on when the outside temperature is cool. When the carbon layer is on the outside, it releases heat keeping the wearer cool. The team estimates that the Dual-Mode fabric can increase a wearer's comfort by 10 degrees F, but the fabric's actual potential may be as much as 25 degrees F. Dual-Mode Fabric Future The Stanford team has conduced extensive testing on its new reversible fabric, such as infrared and thermal property tests; several wearable tests including air permeability, wick- ing property, moisture transmission, mechanical property, and washability; and sweat tests. "This Dual-Mode textile can expand the users' adaptability to ambient temperature variations, which brings a new design principle for engineering textile insulation," notes Cui. Going forward, the team's ambitions are to create an everyday textile that could be used by populations throughout the world to save large amounts of energy. In addition, they believe this Dual-Mode textile provides new insights on how to enhance the functionality of smart textiles, and potentially combine wearable technology for clothing with medical devices and other healthcare applications. O EDUCATION | STANFORD UNIVERSITY Creating a Fabric for Warm & Cold Weather Advancing Reversible Dual-Mode Fabric for Thermal Comfort. By Kathlyn Swantko Kathlyn Swantko, president of the FabricLink Network, created TheTechnicalCenter.com for Industry networking and marketing of specialty textiles, and FabrickLink.com for consumer education involving everything fabric. Contact: kgswantko@fabriclink.com For more information on Stanford's "Dual Mode" fabric research, contact Dr. Yi Cui, Professor of Materials Science and Engineering, at: yicui@stanford.edu, 650-723-4613 FabricLink.com TheTechnicalCenter.com "We have been using the FabricLink Network for over 10 years and it has consistently been one the top digital drivers to our site, and a great source of information for trade and consumers alike." Lisa Hardy North America Marketing Manager Teflon™ textile finishes, Teflon™ fabric protector, The Chemours Company Why clients are excited about the benefits of The FabricLink Network Partnership Opportunities: Kristi Rummel kristi@rummelmedia.com 608.435.6220 Editorial Opportunities: Kathy Swantko kgswantko@fabricklink.com 818.345.7501 How will they find you, if you're not there? The FabricLink Network THE Networking / Education Search Engine for ALL Things Textile Related! March/April 2018 ~ Textile Insight • 33 textileinsight.com

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