Zhang Ze-Lian, Dong Xiu, Fan Yi-Ning, Yang Lu-Ming, He Lu, Song Fei, Wang Xiu-Li, Wang Yu-Zhong
The Collaborative Innovation Center for Eco-Friendly and Fire-Safety Polymeric Materials, National Engineering Laboratory of Eco-Friendly Polymeric Materials (Sichuan), State Key Laboratory of Polymer Materials Engineering, College of Chemistry, Sichuan University, Chengdu 610064, China.
ACS Appl Mater Interfaces. 2020 Oct 14;12(41):46710-46718. doi: 10.1021/acsami.0c13551. Epub 2020 Oct 5.
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.
由于纤维素纳米晶体（CNCs）能自发组织成手性向列结构，可在可见光区域选择性反射圆偏振光，因此制备对拉伸变形有响应的CNC材料备受关注，但仍是一个巨大挑战，尽管这种功能在现有生物如变色龙中广泛存在，不过由于其固有的脆性。在此，在CNC中引入了柔性网络结构，对刚性纳米材料起到桥梁作用。所制备的薄膜显示出高柔韧性，断裂应变高达39%。值得注意的是，首次实现了CNC材料肉眼可见的拉伸诱导结构颜色变化。此外，这些软材料在表观结构颜色变化方面表现出对湿度和压缩的响应特性。通过控制环境湿度，可显示或隐藏无墨书写留下的彩色标记。这种生物基光子薄膜作为一种新型“智能皮肤”，具有潜在的用于显色传感、加密和防伪等多功能应用。
