(March 11, 2016) HARVARD
RESEARCHERS DESIGN 3D MATERIAL WITH CONTROLLABLE SHAPE AND SIZE
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 have designed a new type of foldable
material that is versatile, tunable and self actuated. It can change size,
volume and shape; it can fold flat to withstand the weight of an elephant
without breaking, and pop right back up to prepare for the next task.
The research was lead by 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), James Weaver, Senior
Research Scientist at the Wyss Institute for Biologically Inspired Engineering
at Harvard University and Chuck Hoberman, of the Graduate School of Design. It
is described in 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,” said Johannes T. B. Overvelde, graduate
student in Bertoldi’s lab and first author of the paper.
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. The team
demonstrated, both theoretically and experimentally, that the cube can be
deformed into many different shapes by folding certain edges, which act like
hinges. The team embedded pneumatic actuators into the structure, which can be
programmed to deform specific hinges, changing the cube’s shapes and size, and
removing the need for external input.
The team 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’s 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,” said Bertoldi.
“We know exactly what we need to actuate in order to get the shape we want.”
The material can be embedded with any kind of actuator,
including thermal, dielectric or even water.