Transparent and flexible structurally colored biological nanofiber films for visual gas detection

Abstract

•Construct structurally colored film using sustainable biological nanofibers •Multiple advantages are integrated into the one •Achieve ultrafast color response to environment stimuli of less than 1 s •Realize visual gas concentration detection simply upon blowing 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. 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.