Programming shape-change : integrative computational design of materials, mesostructures, and motion mechanisms for 4D-printing

Abstract

Shape-changing material systems are advantageous as passively actuated mechanisms for generating movement, with architectural applications ranging from adaptive building skins to the self-shaping manufacturing of building components. 4D printing, a technique that combines stimuli-responsive materials with additive manufacturing, is a promising method for the fabrication and programming of shape-changing structures. However, limitations in material responsiveness, programmability of shape-change, and the robustness of structures have constrained their functionality and real-world applicability. This dissertation introduces an integrative computational fabrication approach for the development of 4D printed hygroscopic material systems based on co-designing materials, mesostructures, and motion mechanisms. By tuning the material properties and structuring at hierarchical length scales, highly functional and precisely programmable 4D printed material systems have been developed. This material programming approach has been demonstrated through three studies, each focusing on one of the aforementioned aspects: by co-designing biobased cellulose-filled materials for 4D printing, the responsiveness of structures to target ranges of ambient relative humidity levels has been tuned; by precisely designing the mesoscale material structuring inside the 4D printed elements, their spatial and temporal shape change has been programmed; and through the development and utilization of computational fabrication workflows for 4D printing, novel motion mechanisms with enhanced functionality, such as motion amplification, have been created. The proposed material programming methodology and the developed material system have been implemented in the design and fabrication of SolarGate, a 4D printed, weather-responsive façade system installed on the LivMatS Biomimetic Shell. Consisting of 424 4D printed shading elements, the SolarGate regulates the solar heat gain of the building by providing adaptive shading in response to daily and seasonal weather cycles without consuming any operational energy. These results showcase the potential for creating an architecture that is highly functional, ecological, and in tune with the environment, being powered by and at the same time empowering the earth.