Bio-based visual optical pressure-responsive sensor

A bio-based pressure-responsive sensor with adjustable structural color is prepared by combining aerogel skeleton of cellulose nanocrystals (CNCs)/poly(ethylene glycol) (PEG) obtained via the ice-templating method with flexible polyacrylamide (PAAM) elastomer. The white aerogel is composed of consecutive ribbons, demonstrating chiral nematic structure. These ribbons are rearranged to be vertical to the force direction, leading to immediate appearance of the structural color when the 3D aerogel transforms to a 2D plane. Helical pitches are regulated by the PEG content that the wavelength of structural color covers up to 178 nm. There is an excellent linear correlation between pressure and transmittance of reflectance peak, and the sensitivity to pressure can be regulated by changing solid content of PAAM. Furthermore, the pressure-responsive color is still vivid after 16 cycles of compression. This flexible material with pressure-responsive structural color is promising in sensing, intelligent display, information transmission, and etc.