Multiple functionalities of highly conductive and flexible photo- and thermal-responsive colorimetric cellulose films

IMPACT STATEMENT We demonstrate highly conductive, flexible, transparent, and reversibly color-switchable films based on a spiropyran-incorporated cellulose acetate biopolymer. The films can realize high performance photoelectronics that include reversibly tunable color switching. Photochromic materials have attracted considerable interest because of their ability to undergo reversible color switching. We report highly conductive and flexible spiropyran-embedded cellulose films with multiple optical and electrical functionalities, showing negative photo- and thermochromism. Combining silver nanowires and conductive polymer with cellulose/spiropyran films achieves a very low sheet resistance of 6.7 ohm/sq. The optimized films show outstanding mechanical stability with negligible electrical loss (resistance change < 2%) after 1000 bending cycles. The photo- and thermal-responsive conductive cellulose/spiropyran films can be used to directly visualize information and as flexible heating devices, pressure-responsive sensors, and colorimetric thermometers with high device performance.

Automated summary

In this study, highly conductive, flexible, transparent, and reversibly color-switchable films based on a spiropyran-incorporated cellulose acetate biopolymer were demonstrated. These films can achieve high performance photoelectronics, including reversibly tunable color switching. The optimized films showed outstanding mechanical stability and dimensional stability, with minimal resistance change after multiple bending cycles. This film has various potential applications, including visualizing information, flexible heating devices, and sensors.