Structurally colored films hold promise as cheap platforms for use in visual detection. However, achieving accurate stimuli-responsive functions that can be distinguished by the naked eye in a single thin, robust, and practically useful material remains a challenge. Herein, we demonstrate flexible and self-standing structurally colored films fabricated by filtrating sustainable hydrophilic nanofibrillated cellulose through a porous hydrophobic membrane, followed by natural drying. 480–644 nm thick and composed of densely packed, high-aspect-ratio nanofibers entangled in web-like structures, the films are transparent, tailorable into a variety of shapes, and easily foldable. They exhibit iridescence owing to thin-film interference and reversibly change color in seconds when exposed to various moist gases and liquids. We validate the visual gas-detection capabilities of the films by measuring the ethanol concentration in the breath of an inebriated participant and envisage that these materials will find use in automated and broad-spectrum gas-detection devices.

结构彩色薄膜有望成为用于视觉检测的廉价平台。然而，在单一的薄、坚固且实用的材料中实现可以通过肉眼区分的准确刺激响应功能仍然是一个挑战。在这里，我们展示了通过多孔疏水膜过滤可持续的亲水纳米原纤化纤维素，然后自然干燥制成的柔性和自立结构彩色薄膜。480-644 nm 厚，由密集排列的高纵横比纳米纤维缠绕成网状结构组成，薄膜是透明的，可剪裁成各种形状，并且易于折叠。由于薄膜干涉，它们呈现出虹彩，当暴露于各种潮湿气体和液体时，它们会在几秒钟内可逆地改变颜色。