Researchers "color code" webbing material for exposure to damaging UV rays

BROOKLYN, New York, Tuesday, August 16,  2022 —Webbing structures — from chin straps and parachute material, to space habitats — are extensively employed in engineering systems as load-bearing components. They are frequently subjected to extended ultraviolet (UV) light irradiation, which can affect their integrity and reduce their mechanical strength. Despite technological advancements in structural health monitoring, long-term UV sensing techniques for webbings remain under-developed. 

A new study, led by Maurizio Porfiri, Institute Professor of Mechanical and Aerospace Engineering, Biomedical Engineering, Civil and Urban Engineering, and incoming Director of the NYU Center for Urban Science and Progress (CUSP) at the NYU Tandon School of Engineering, sheds light on an enticing solution: a photochromic nylon webbing that, because it comprises spiropyran (SP) functionalized polymers, demonstrates color variation in response to extended UV exposure with controlled, color variation over multiple time scales that is conducive to UV sensing. 

The team, including Peng Zhang, former researcher in Porfiri’s group and now faculty member at Tennessee Tech, and John Ohanian, research scientist at Luna Innovations, developed a mathematical model grounded in photochemistry to interpret experimental observations, unveiling the photochromic phenomenon as a multi-step, multi-timescale photochemical process involving several chemical species offering the basis for the inference of the webbing’s color. The paper, "Spiropyran-functionalized photochromic nylon webbings for long-term ultraviolet light sensing," is featured on the cover of Journal of Applied Physics. 

In their research, the investigators found that the decay rate of the webbings’ color demonstrated a dependence on the initial concentration of the SP dye. Webbings with the lowest dye concentration maintained sensitivity for four weeks, whereas at the highest dye concentration, they exhibited sensing capability after eight weeks. Thus dye concentration could be customized to meet the lifetime of the targeted applications.

The proposed photochromic webbing and the photochemistry-based mathematical model could inform future designs of UV-sensitive structures that maintain sensitivity under weeks of continuous sunlight UV exposure.

The work was supported by the U.S. Navy.

The paper, Spiropyran-functionalized photochromic nylon webbings for long-term ultraviolet light sensing, is available at: https://aip.scitation.org/doi/10.1063/5.0093641

About the New York University Tandon School of Engineering

The NYU Tandon School of Engineering dates to 1854, the founding date for both the New York University School of Civil Engineering and Architecture and the Brooklyn Collegiate and Polytechnic Institute. A January 2014 merger created a comprehensive school of education and research in engineering and applied sciences as part of a global university, with close connections to engineering programs at NYU Abu Dhabi and NYU Shanghai. NYU Tandon is rooted in a vibrant tradition of entrepreneurship, intellectual curiosity, and innovative solutions to humanity’s most pressing global challenges. Research at Tandon focuses on vital intersections between communications/IT, cybersecurity, and data science/AI/robotics systems and tools and critical areas of society that they influence, including emerging media, health, sustainability, and urban living. We believe diversity is integral to excellence, and are creating a vibrant, inclusive, and equitable environment for all of our students, faculty and staff. For more information, visit engineering.nyu.edu.

###