Controllable Deformation: A 4D-Printing Simulation Framework for Porosity-Driven Hygromorphic Bilayer Structure

This research proposes a 4D-printing simulation framework that uses porosity as a design parameter to program deformation in hydromorphic bilayer structures. Grounded in Timoshenko’s sandwich beam theory, the framework integrates physical experimentation, parametric modeling, and dynamic simulation (via Grasshopper), enabling inverse design of porosity distributions for target bending. Bilayers of wood-based filaments (active) and PLA (passive) demonstrate consistent humidity-driven shape changes. The study proceeds in three phases: (a) physical experiments assessing porosity–deformation relationships, (b) dynamic simulation to collect curvature data, and (c) mathematical modeling to refine design guidelines. A prototype façade panel validates the framework, with predicted bending closely matching experimental results. This confirms the method’s feasibility for scalable, adaptive architectural applications.