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Hygroscopic Assembly
The aim of Hygroscopic Assembly is to combine material science research with current digital design and fabrication technologies to increase the size and load capacities of passively actuated "4D" structures. In this project, a series of cantilevering trusses that can autonomously transform in response to water are designed, produced, and tested. These trusses are a proof-of-concept application used to create load-bearing components for walkway canopies in monsoon cities that protect from wind-driven rain and allow better ventilation in their dry state. Through iterative testing and prototyping, alongside digital design tools to explore the morphospace of this structural class, experiments have been conducted on cantilevers ranging from 12 centimeters to over 2 meters in length. In addition to compilation of the fabrication methodologies and shape change data, this work will culminate in the construction of a 16-square-meter canopy that consists of several cantilevers and an integrated textile membrane that is to be tested outdoors in real-time conditions. The resulting structure is a bespoke, modular kit-of-parts that offers strength, minimal weight, and response time on the order of minutes, lowering the implementation barrier for passively actuated, next-generation architectural structures.
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The enabling aspects of this work are coupled discoveries of custom processing methods for intriguing natural materials and high-performance additive manufacturing techniques. Through a tailored fabrication process of the chitosan films, different capacities for shape change of the cantilever can be tuned. This is complemented by manufacturing components of the 4D cantilever using 3D printing technologies. The geometric freedom of this process allows the programming of the overall shape change of the trusses through changes in depth and by prescribing specific rotational range within the joints. This allows contingent, material-based shape changes of the cantilever to be mediated through geometric means, leading to a predictable range of movement.
Bespoke rotational joint design that enables truss motion
Custom fabrication process for fiber-reinforced chitosan films
The components of the truss are rationalized as a kit-of-parts with assembly logic included in the design of each part. Multiple trusses can be aggregated together and combined with textile covers to form responsive canopies.
Truss kit-of-parts
Small-scale prototype of responsive canopy
The variable geometries of the joints are generated using a parametric modeling workflow that is linked to a truss drawing tool using the Kangaroo Physics plugin. The drawing tool outputs the possible truss curvatures based on an input expansion of the chitosan films and the depth variation of the truss. The necessary rotation at each node at the truss to provide the desired curvature is fed into the parametric design tool to generate each joint geometry.
Joint family
Full truss geometry
The culmination of this research will be a 16m pavilion composed of six trusses and a textile membrane that will be installed on the Singapore University of Technology & Design campus in winter 2020.
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Illustration of the forthcoming Hygroscopic Assembly Pavilion