Harvard Researchers Develop Self-Actuated 3D Material with Controllable Shape and Size

Researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) have developed a versatile 3D material that bends, folds, and shrinks on its own. The foldable, tunable, and self actuated material is capable of changing shape, size, and volume. When folded flat it is strong enough to withstand an elephant’s weight without breaking, and bounces back to prepare for the subsequent task.

Harvard researchers have designed a new type of foldable material that is versatile, tunable and self actuated. Here a single cell folds according to its actuation. (credit: Johannes Overvelde/SEAS)

Imagine a home that can be accommodated in a backpack, or a wall that could well serve as a window, all at the turn of a switch.

The study was headed by James Weaver, a Senior Research Scientist at the Wyss Institute for Biologically Inspired Engineering at Harvard University; Katia Bertoldi, the John L. Loeb Associate Professor of the Natural Sciences at the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS); and Chuck Hoberman from the Graduate School of Design. The results of the study have been published in the journal, Nature Communications.

We’ve designed a three-dimensional, thin-walled structure that can be used to make foldable and reprogrammable objects of arbitrary architecture, whose shape, volume and stiffness can be dramatically altered and continuously tuned and controlled.

Johannes T. B. Overvelde, Graduate Student, Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS)

A 3-D Material that Folds, Bends and Shrinks on its Own

Inspired by an origami method known as snapology, the new structure was designed from extruded cubes featuring 36 edges and 24 faces. Similar to origami, its shape can be changed by folding it along its edges. At both theoretical and experimental levels, the researchers demonstrated that by folding certain edges of the cube it is possible to deform the cube into a wide range of shapes, as the edges serve as hinges. The structure was also integrated with pneumatic actuators, which can be programmed to distort certain hinges, modifying the size and shape of the cube and eliminating the necessity for an external input.

The researchers joined 64 separate cells to produce a 4 x 4 x 4 cube that is capable of growing, reducing its size, changing its shape universally, folding flatly, and changing the direction of its microstructure.

As and when the structure changes its shape, it also modifies its stiffness. This means that an extremely stiff or flexible material can be developed by employing the same design. With the actuated modifications in material characteristics, the material gains a fourth dimension.

We not only understand how the material deforms, but also have an actuation approach that harnesses this understanding. We know exactly what we need to actuate in order to get the shape we want.

Katia Bertoldi, Associate Professor, Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS)

The material can be embedded with any kind of actuator, including thermal, dielectric or even water.

“The opportunities to move all of the control systems onboard combined with new actuation systems already being developed for similar origami-like structures really opens up the design space for these easily deployable transformable structures," said Weaver.

This structural system has fascinating implications for dynamic architecture including portable shelters, adaptive building facades and retractable roofs. Whereas current approaches to these applications rely on standard mechanics, this technology offers unique advantages such as how it integrates surface and structure, its inherent simplicity of manufacture, and its ability to fold flat.

Chuck Hoberman, Graduate School of Design

“This research demonstrates a new class of foldable materials that is also completely scalable,” Overvelde said, “It works from the nanoscale to the meter-scale and could be used to make anything from surgical stents to portable pop-up domes for disaster relief.”

Twan A. de Jong, Sergio A. Becerra, Yanina Shevchenko, and George Whitesides co-authored the paper. The National Science Foundation, the Materials Research Science and Engineering Center, and the Wyss institute through the Seed Grant Program funded the study.

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