Totimorphic assemblies from neutrally-stable units

TL;DR

This paper introduces totimorphic assemblies made from neutrally-stable units that can morph into various shapes, combining theoretical, simulation, and experimental approaches to create adaptable, load-bearing structures with controllable geometry and deformation.

Contribution

It presents a novel neutrally stable unit cell and demonstrates how to design and realize morphable, load-bearing assemblies with independent control over shape and deformation response.

Findings

Neutrally stable units exhibit a family of energetically equivalent morphing motions.

Assemblies can be designed to morph between specific shapes.

Experimental prototypes confirm theoretical predictions.

Abstract

Inspired by the quest for shape-shifting structures in a range of applications, we show how to create morphable structural materials using a neutrally stable unit cell as a building block. This unit cell is a self-stressed hinged structure with a one-parameter family of morphing motions that are all energetically equivalent; however, unlike kinematic mechanisms, it is not infinitely floppy and instead exhibits a tunable mechanical response akin to that of an ideal rigid-plastic material. Theory and simulations allow us to explore the properties of planar and spatial assemblies of neutrally-stable elements and also pose and solve the inverse problem of designing assemblies that can morph from one given shape into another. Simple experimental prototypes of these assemblies corroborate our theoretical results and show that the addition of switchable hinges allows us to create load-bearing structures. All together, totimorphs pave the way for structural materials whose geometry and deformation response can be controlled independently and at multiple scales.