Vapor‐Sensitive Materials from Polysaccharide Fibers with Self‐Assembling Twisted Microstructures

Abstract Polysaccharides play a variety of roles in nature, including molecular recognition and water retention. The microscale structures of polysaccharides are seldom utilized in vitro because of the difficulties in regulating self‐assembled structures. Herein, it is demonstrated that a cyanobacterial polysaccharide, sacran, can hierarchically self‐assemble as twisted fibers from nanoscale to microscale with diameters of ≈1 µm and lengths >800 µm that are remarkably larger than polysaccharides previously reported. Unlike other rigid fibrillar polysaccharides, the sacran fiber is capable of flexibly transforming into two‐dimensional (2D) snaking and three‐dimensional (3D) twisted structures at an evaporative air–water interface. Furthermore, a vapor‐sensitive film with a millisecond‐scale response time is developed from the crosslinked polymer due to the spring‐like behavior of twisted structures. This study increases understanding of the functions of fibers in nature and establishes a novel approach to the design of environmentally adaptive materials for soft sensors and actuators.