Chameleon-Inspired Variable Coloration Enabled by a Highly Flexible Photonic Cellulose Film

• Published in: ACS applied materials & interfaces 2020-10, Vol.12 (41), p.46710-46718
• Main Authors: Zhang, Ze-Lian, Dong, Xiu, Fan, Yi-Ning, Yang, Lu-Ming, He, Lu, Song, Fei, Wang, Xiu-Li, Wang, Yu-Zhong
• Format: Article
• Language: English
• Subjects: Applications of Polymer, Composite, and Coating Materials
• ISSN: 1944-8244; 1944-8252
• DOI: 10.1021/acsami.0c13551

Due to spontaneous organization of cellulose nanocrystals (CNCs) into the chiral nematic structure that can selectively reflect circularly polarized light within a visible-light region, fabricating stretching deformation-responsive CNC materials is of great interest but is still a big challenge, despite such a function widely observed from existing creatures, like a chameleon, because of the inherent brittleness. Here, a flexible network structure is introduced in CNCs, exerting a bridge effect for the rigid nanomaterials. The as-prepared films display high flexibility with a fracture strain of up to 39%. Notably, stretching-induced structural color changes visible to the naked eye are realized, for the first time, for CNC materials. In addition, the soft materials show humidity- and compression-responsive properties in terms of changing apparent structural colors. Colored marks left by ink-free writing can be shown or hidden by controlling the environmental humidities. This biobased photonic film, acting as a new “smart skin”, is potentially used with multifunctions of chromogenic sensing, encryption, and anti-counterfeit.