New foldable material can change size, volume, shape

Imagine a house that could fit in a backpack or a wall that could become a window with the flick of a switch. Harvard researchers say it may be possible!
Scientists at the top US university have designed a new type of foldable material that is versatile, tunable and self actuated.
The material can change size, volume and shape and can fold flat to withstand the weight of an elephant without breaking, and pop right back up to prepare for the next task, scientists said.
"We have 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," said Johannes T B Overvelde from Harvard University.

The structure is inspired by an origami technique called snapology, and is made from extruded cubes with 24 faces and 36 edges. Like origami, the cube can be folded along its edges to change shape.
Researchers demonstrated, both theoretically and experimentally, that the cube can be deformed into many different shapes by folding certain edges, which act like hinges. They embedded pneumatic actuators into the structure, which can be programmed to deform specific hinges, changing the cube's shape and size, and removing the need for external input.

Researchers connected 64 of these individual cells to create a 4x4x4 cube that can grow, and shrink, change its shape globally, change the orientation of its microstructure and fold completely flat.

As the structure changes shape, it also changes stiffness - meaning one could make a material that is very pliable or very stiff using the same design. These actuated changes in material properties adds a fourth dimension to the material.
"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," said Katia Bertoldi from Harvard University.
The material can be embedded with any kind of actuator, including thermal, dielectric or even water, researchers said.
"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 James Weaver from Harvard University.

"This structural system has fascinating implications for dynamic architecture including portable shelters, adaptive building facades and retractable roofs," added Chuck Hoberman from Harvard University.
The findings were published in the journal Nature Communications.