Spiropyran-functionalized photochromic nylon webbings for long-term ultraviolet light sensing

• Published in: Journal of applied physics Vol. 132; no. 6
• Main Authors: Zhang, Peng, Ohanian, Osgar John, Porfiri, Maurizio
• Format: Journal Article
• Language: English
• Published: Melville American Institute of Physics 14.08.2022
• Subjects: Color; Differential equations; Light irradiation; Load bearing components; Load bearing elements; Mathematical analysis; Mathematical models; Nylon; Ordinary differential equations; Photochemistry; Photochromism; Spiropyrans; Structural health monitoring; Ultraviolet radiation; Webbing
• ISSN: 0021-8979; 1089-7550
• DOI: 10.1063/5.0093641

Webbing structures are extensively employed in engineering systems as load-bearing components. In a field setting, webbings are frequently subject 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. To fill this gap, we propose a photochromic nylon webbing that demonstrates color variation in response to extended UV exposure. The webbing offers a rich, yet controlled, color variation over multiple time scales that is conducive to UV sensing. A mathematical model grounded in photochemistry is developed to interpret experimental observations, unveiling the photochromic phenomenon as a multi-step, multi-timescale photochemical process involving several chemical species. The model captures the evolution of the coexisting species through a system of nonlinear, coupled ordinary differential equations, offering the basis for the inference of the webbing’s color. 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.