Current examples of passively actuated structures and surfaces show enormous potential in conferring buildings and products with the ability to assume multiple spatial configurations without added electrical power. This research focuses on leveraging the water‐responsive material properties of cotton‐fiber‐reinforced chitosan films to enable fast‐actuating (<5 minutes), large scale (∼1 m; 3.3 ft.), passive structural changes of a 4m2 (43 ft.2) rain‐responsive canopy prototype consisting of multiple cantilevering truss members connected by a textile membrane. This paper describes the materials engineering development, integrated design‐simulation methodology, and tectonics of the proof‐of‐concept canopy system. Results from empirical testing for dynamic, water‐actuated systems are reported along with the practical and conceptual implications of deploying 4D biomaterial‐based structures.
