Dissertation Title: Folded Digital Materials

Abstract:

Across length scales, structure governs behavior, and architected materials exploit this by tailoring bulk properties through cell geometry and constituent material. Plate-based architectures achieve higher stiffness and strength than beam-based lattices at equal relative density, but remain difficult to fabricate, especially with enclosed cells. Digital materials address scalability for beam-based materials through discrete assembly of mass-produced parts, but comparable approaches for plate-based architectures are underdeveloped.

This thesis introduces Folded Digital Materials, a design and manufacturing framework that integrates parametrically defined folded cells with discrete assembly. The mechanical properties of these lattices, folded from ordinary sheet stock, compete with those of architected materials that require specialized additive processes. This thesis extends digital materials by being digital in topology but parametric in geometry: cells connect through a discrete set of assembly rules, while the dimensions and fold angles of each cell can vary continuously. Each cell is fabricated by cutting and folding commercially available sheet stock, making geometry both the description and the method for its realization. This geometric flexibility enables cells to conform to prescribed boundaries, forming cellular solids, shaped cores, and custom shells with finer geometric control than a fixed lattice of identical parts. Mechanical properties can be tuned through fold angles, plate cuts, sheet thickness, and cell arrangement. Discrete assembly connects these cells into structures larger than the tools used to fabricate them. Together, folding and assembly provide a scalable approach spanning centimeter-scale lattices to meter-scale shells, with fabrication constraints incorporated directly into the design of shape and mechanical behavior.

I develop this framework at three scales, from centimeter-scale lattices to meter-scale shells. At the material scale, I characterize the stiffness, strength, collapse, and impact response of stainless-steel plate lattices, showing that progressive folding can reach regions of the Ashby chart otherwise occupied by architected materials requiring more specialized fabrication. At the component scale, I develop shaped cores and morphing structures through structural anisotropy and encoded degrees of freedom, extending cellular design to systems with prescribed shape and motion. Finally, at the structural scale, I apply the same framework to the design and fabrication of freeform surfaces, where the lattice no longer fills a volume but forms load-bearing shells.

Neil Gershenfeld
Director, Center for Bits and Atoms
Center for Bits and Atoms

Tomohiro Tachi
Professor, Graduate School of Arts and Sciences and Department of Architecture, The University of Tokyo
The University of Tokyo

Erik Demaine
Professor, Computer Science and Artificial Intelligence Laboratory (CSAIL), Massachusetts Institute of Technology
MIT

Kaitlyn Becker
Assistant Professor, Department of Mechanical Engineering, Massachusetts Institute of Technology
MIT