Transforming metamaterial alters size, volume, and shape on command
Harvard researchers have created a 3D programmable mechanical metamaterial that can be programmed to change shape, volume and size on command, making it ideal for building a range of different assemblies and structures that can be automatically altered to suit their purpose or environment. Claimed to be able to take the weight of an elephant when laid flat, the new material could be used to make everything from tiny self-deploying nanostructures for use in medical procedures, all the way up to large buildings that are able to metamorphose for different purposes on command.
"This research demonstrates a new class of foldable materials that is also completely scalable," said Johannes T. B. Overvelde, graduate student in the John A. Paulson School of Engineering and Applied Sciences at Harvard. "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."
Inspired by a type of modular, unit-based origami called snapology, in which strips of paper are joined together to create complex, multi-faceted shapes, the metamaterial structure is made from extruded cubes with 24 faces and 36 edges. Like traditional origami creations, the Harvard device is also able to fold along its edges to change shape. Unlike normal origami, however, this metamaterial version folds and unfolds using remotely-controlled embedded pneumatic actuators.
"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," said Overvelde.
As the team notes, origami patterns have proven to be promising in the design of solar panels for space deployment, flexible surgical stents, and flexible electronic components, but with the employment of snapology techniques and remote actuators, they also believe that their creation takes folding structures to the next logical level.
"This structural system has fascinating implications for dynamic architecture including portable shelters, adaptive building facades and retractable roofs," said engineer Chuck Hoberman, of the Wyss Institute for Biologically Inspired Engineering, also at Harvard. "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."
Using thin polymer sheets, the team created 64 individual cells to make a 4 x 4 x 4 cube capable of growing, shrinking, changing its entire shape, altering the orientation of its microstructure, and folding to become totally flat. Along with the structure's ability to deform on command, it also changes its stiffness, which the team believes could make for bespoke structures that can be made both pliable or stiff using the same design.
Able to be embedded with many kinds of actuators, including heat-activated, dielectric, pneumatic, or even water-based, the Harvard team is confident that its new creation will, with the aid of inbuilt control electronics, lead to a whole new range of deformable, self-actuating devices across a wide area of applications.
"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 Doctor James Weaver, also from the Wyss Institute at Harvard.
The results of this research were recently published in the journal Nature Communications.
The short video below shows the material in action.