Totimorphic structural materials can morph into any shape, as researchers at Harvard’s John A. Paulson School of Engineering and Applied Sciences (SEAS) have found. The team have developed shape-shifting materials that can hold any 2D and 3D form, which makes way for new types of multifunctional materials for use in a number of different fields.
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Published in the journal Proceedings of the National Academy of Sciences, the research details how the shapes “lay the foundation for the engineering of functionable shapes using a new type of morphable unit cell.” This backs up the claim that the material can hold any stable shape across a limitless amount of configurations.
Today’s shape-shifting materials and structures can only transition between a few stable configurations but we have shown how to create structural materials that have an arbitrary range of shape-morphing capabilities
L. Mahadevan, Professor of Applied Mathematics, of Organismic and Evolutionary Biology, and of Physics and senior author, SEAS
Endless, ‘Totimorphic’ Possibilities
Dubbed ‘totimorphic’, the material demonstrates the ability to take on any stable shape configuration. The researchers connected individual unit cells with neutrally stable joints to create a variety 2D and 3D structures using individual totimorphic cells.
A major challenge when designing shape-shifting or materials that possess the ability to morph, is striking the right balance between rigidity and conformability. If too rigid, the form lacks the ability to shift into new configurations. Whereas, if the form is excessively conformal then it will not be able to hold the desired shape for long.
Inspired by both the challenge and the need for shape-shifting structures in a range of applications, the team set out to create morphable structural materials using a neutrally stable unit cell with a two rigid components: a strut and a lever.
An example of a neutrally stable system would be a common desk lamp, similar to the lamp at the start of a Pixar movie. This system clearly shows how the lamp head remains stable in any fixed position due to the springs counteracting gravitational forces regardless of the lamp head’s position.
What’s unique about the advances made in the Harvard team’s research is that their arrangement of interlocking cells can take on ‘any’ number of configurations; this makes for endless possibilities as the totimorphic structure is freed from constraints associated other shape-shifting materials.
“These structures allow for independent control of the geometry and mechanics, laying the foundation for engineering functional shapes using a new type of morphable unit cell,” says Mahadevan.
Shape-Shifting Geometry
Using mathematical models and real-world scenarios, the team was able to demonstrate how a single sheet of totimorphic cells could contort into distinct and complex forms even twisting to form a helix and morphing into shapes that resembled facial features.
We show that we can assemble these elements into structures that can take on any shape with heterogeneous mechanical responses
S. Ganga Prasath, Postdoctoral Fellow and Co-Author, SEAS
Thus with unlimited possibilities comes limitless futures for totimorphic materials, bound only by the imagination researchers and those seeking novel ways to use the materials. Other applications could see these materials deployed across a multitude of industries facilitating very-real potential for this new kind of multifunctional, totimorphic materials beyond the laboratory.
“All together, these totimorphs pave the way for a new class of materials whose deformation response can be controlled at multiple scales,” said Mahadevan.
Due to the fact these materials are based on geometrical forms, they could even be minimized for use in robotics applications or act as sensors in biotechnology as well as being scaled up to facilitate larger architectural forms really backing up the headline, ‘A Totimorphic Structural Material Can Be Anything.’
An Emerging Field
Other initiatives are working on similar projects geared towards working with shapes-shifting materials. These include experiments with liquid crystals that manipulate its appearance through changes in topological environment.2 As well as an MIT-based project that uses a class of “4D materials” that deform and change shape in response to ambient conditions.3
Some of the next steps in further developing these shape-shifting materials include achieving precise control over the forms and getting the materials suited to their intended application.
Due to the number of potential applications for such materials, the research and development of shape-shifting materials is an emerging and fast-moving field.
Soon, some of these materials may be used to build artificial muscles that can articulate in a way that mirrors the contractions and rotations of natural muscle, as well as producing materials that respond to changes in ambient conditions for building self-inflating structures – such as tents for rapid deployment in disaster areas.
References and Further Reading:
Chaudhary, G., Ganga Prasath, S., Soucy, E., & Mahadevan, L. (2021). Totimorphic assemblies from neutrally stable units. Proceedings of the National Academy of Sciences, 118(42), e2107003118. doi.org/10.1073/pnas.2107003118
Andrew J. Ferris, Charles Rosenblatt, Timothy J. Atherton. (2021). Spontaneous Anchoring-Mediated Topography of an Orientable Fluid. 10.1103/physrevlett.126.057803. Physical Review Letters. https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.126.057803
MIT News. (2019). This flat structure morphs into shape of a human face when temperature changes. Massachusetts Institute of Technology. https://news.mit.edu/2019/mesh-structure-shape-temperature-changes-0930 https://news.mit.edu/2019/mesh-structure-shape-temperature-changes-0930
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