Developed with the Princeton University’s Form Finding Lab, this work presents the tools for the design of a variable stiffness adaptive building skin, inspired by cell walls of plants. Cell walls have the particularity of adapting their geometric and mechanical properties according to internal or external stresses as well as growth expansion. This makes cell walls rigid and, at the same time, compliant to allow cell wall expansion during ontogeny stages. A closer study shows that cell walls have a variable stiffness allowing them to cope with the two contradictory states. Most of the time, building skins are static because moving facades require a lot of energy and budget to create an adaptive façade. In other cases, the use of hinges makes the adaptive structures energy consuming and requires a lot of maintenance. Cell walls analysis is relevant for biomimetic materials and adaptive structures because it introduces the idea of a passive maintenance-free façade. Furthermore, the technology advances and more specifically, the robotic fabrication enables us to introduce nature’s knowledge in the construction world.
The proposed building skin is composed of bimetallic sheets, which curve with a change of temperature, inserted in a compliant continuous section-variable lattice. Using variable sections and continuous pouring of the lattice helps create a smart informed material that has different values of stiffness to be more or less pliant with the bimetallic sheets deformation. A complete geometry-to-structure-analysis parametric model has been developed. The lattice geometry determination showed it had a great role in allowing deformation of the lattice.