Textile Insight

amaging chemicals come from the burning of fossil fuels, chemical solvents, and gas vapors discharged from motor vehicle exhausts, industrial facilities, utilities, and other sources. Emissions from gases like nitrogen oxides, sulfur dioxide, carbon monoxides, and Volatile Organic Compounds (VOCs) cause respiratory diseases in humans, such as asthma, COPD, and bronchitis, and contribute to other severe health issues. To help monitor hazardous pollutants in the air, engineers at Tufts University have developed a novel method for creating dyed threads that change color when exposed to hazardous gases. Woven into fabric for clothing, these smart, gas-detecting threads could be an affordable safety asset for first responders, medical and military personnel, and other workplace environments. While not match- ing the precision of monitoring devices commonly used to detect volatile gases, the dyed threads change color within milliseconds of exposure to harmful gases. Under the direction of Sameer Sonkusale, professor of electri- cal and computer engineering at Tufts University's School of Engineering and the Nano Lab at Tufts, the project was started in 2016 as a continuation of the Lab's previous research on low cost optical sensors. Rachel Owyeung, a Tufts graduate student and lead author of the study, was directly involved with the design, fabrication, and testing of the gas sensitive optical sensors on the threads. "We wanted to make textile based optical sensors so they could be integrated into the clothes you wear," explains Sonkusale. "Our goal was to provide a way to sense the pollution in the environment without expensive equipment. The platform has many practical applications for potential use. We envision these threads could be integrated into everyday clothing, personal protective equip- ment, like a lab coat, or even into wound dressings." The Dyeing Process The Tufts dyeing method uniquely traps different kinds of optical dyes onto cotton threads, without any modification of the dyeing technique. Sonkusale notes, "This is achieved through an acidic cleaning of the cotton threads, which removes the non-cellulosic coating from commercially purchased threads." Following the cleaning step, the threads are coated in a hydro- phobic, gas permeable polymer, polydimethylsiloxane (PDMS) to entrap the dyes. Sonkusale continues, "The ability to use dif- ferent optical dyes is essential to sensing selectivity. One optical dye is not selective to a particular gas, but rather the ensemble response of many different dyes gives the overall sensor selec- tivity. Therefore, these thread-based sensors can theoretically be used to sense a wide range of gases, including volatiles from petroleum and oil/gas industry, fumes and exhausts, industrial pollutants, etc." Therefore, the dye will change to a different color depend- ing on the type of gas present. In a three-step dyeing process, Sonkusale's team uses simple dyes that can detect hazardous gases of different chemistries. "Since we are using a dye method that effectively traps the dye to the thread, rather than relying on a binding chemistry," Sonkusale says, "we have more flexibility to use dyes with a wide range of functional chemistries to detect different types of gases." In the final dyeing step, a physical gas permeable seal is also created around the dyed thread, which allows the gas to reach the optical dyes, but at the same time repels water and prevents the dye from leaching during washing. Owyeung notes, "Since repeated washings and use under water does not dilute the dye, the treated fabric can be relied upon for consistent quantifiable detection." Although the researchers have been using cotton threads for their initial study, Sonkusale says the team's approach for entrap- ping dyes can also be extended into nylon, polyurethane, as well as other synthetic or natural threads. l EDUCATION | TUFTS UNIVERSITY Color Changing Alert New Dyeing Method to Detect a Variety of Gases in the Environment. By Kathlyn Swantko D For more information on Tufts University's research on "Dyed Threads Detecting Gases in the Environment", contact Sameer Sonkusale, professor of electrical and computer engineering at Tufts University's School of Engineering and the Nano Lab at Tufts at: Sameer. sonkusale@gmail.com, 617-672-5113, or Rachel Owyeung, lead author of the study, at: rachelowyeung@gmail.com 48 • Textile Insight ~ July/August 2019 textileinsight.com Threads dyed with bromothymol blue, methyl red, and MnTPP (from top to bottom, respectively) upon exposure to ammonia at 0 ppm (left), 50 ppm (middle), and 1000 ppm (right) Kathlyn Swantko, president of the FabricLink Network, created www. TheTechnicalCenter.com for Industry networking and marketing of specialty textiles, and www.fabricklink.com for consumer education involving everything fabric. Contact: kgswantko@fabriclink.com 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! FL-TTC-TI-2016_Layout 1 2/24/16 7:55 AM Page 1

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