These 4D-printed folding mechanisms shape themselves according to the relative humidity of their surroundings. Designed with varying curved hinge geometries and additively manufactured with a wood-polymer filament, each element in this field computes its own folded shape by equalizing its moisture content to environmental conditions.
Material: 3D-printing filaments of wood-filled polymers, PLA, and 100% recycled TPU
The process of 3D-printing hygroscopic materials inherently creates directional strands within each material layer along the extruded path. When exposed to drying or wetting, a single material layer will undergo corresponding shrinking or drying perpendicular to the 3D-printed strands; combined with a non-reactive material layer printed in the perpendicular direction, the material layer shrinks or swells on one side, leading to an overall bending of the resulting bilayer structure.
By connecting opposing bilayers with a flexible curved hinge, both bilayers will bend in opposite orientations – causing a fold to emerge along the curved hinge. These principles allow the 4D-printed structures to be initially fabricated in a flat state and then dynamically self-shaped based on the interplay between their curved hinge geometry, bilayer material structure, and the surrounding humidity.
Institute for Computational Design and Construction (University of Stuttgart)
Prof. Achim Menges
Ekin Sila Sahin