Woven elastic interlayer for 3D‑printed hygroscopic tiles

Abstract Conventional 4D printed actuators often embed programmability in a single hygroscopic layer. As a result they bend mainly in one direction and recover slowly. In this paper we explore the integration of a myocardium inspired thermoplastic polyurethane (TPU) matrix between a rigid PLA base and a hygroscopic cellulose PLA active layer, forming a three material layered system that delivers rapid multi axis deformation without external power. Tile geometry and material assignment are generated in Rhino and Grasshopper and exported as G code, yielding lightweight modules suitable for large scale fabrication. Humidity cycling demonstrates three programmable motion modes (doming, slit opening, and hinge like rotation) obtained solely by adjusting the geometry of the TPU matrix. Tiles that incorporate the TPU matrix return more quickly to their initial flat shape and maintain a stable deformation amplitude within a given specimen over repeated cycles, because the matrix limits over curvature and prevents reverse bending in over dry conditions. By adding this strategically placed TPU matrix, the system converts simple bending elements into durable, zero energy actuators capable of complex and reversible transformations, offering a potential route toward self shaping facade elements for sustainable kinetic architecture.