Scientific American - 04.2020

April 2020, ScientificAmerican.com 19

AGUSTIN INIGUEZ-RABAGO AND JOHANNES T. B. OVERVELDE

AMOLF

MATERIALS SCIENCE

Morphing

Materials

Foldable building blocks could help

with nanoscale manufacturing

The sculpture-like objects in Bas Over­

velde’s laboratory at the Netherlands’

Atomic and Molecular Physics (AMOLF)

Institute are not as simple as they appear.

Made of multiple prism­shaped building

blocks, each face connected by flexible

hinges, they can easily flip from shapes such

as 3 ­D stars into cylinders, balls, and more.

Think of a classic slap bracelet, Over­

velde says: a structure that has two stable

positions, one straight and one curled up.

But his lab’s objects can fold along their

many hinges to pop into dozens of predict­

able positions when pressure is applied.

Beyond building a collection of these physical

objects, Overvelde and his fellow research­

ers used computer simulations to explore

even more complex assemblies of the build­

ing blocks, finding ever y potential shape

many combinations can form. Some large

virtual constructions reached more than 100

stable configurations. The study was detailed

last December in Nature Communications.

By designing and simulating objects that

fold into predictable shapes when pushed

on, the researchers hope to make it easier to

manufacture very tiny robots and materials

with changeable structures. If such items

can easily morph into specific, stable forms,

fewer tools are needed to bend or assem­

ble them. Plus, certain shapes and internal

structures can add strength and make

objects resilient: for instance, “bone has a

microstructure that makes it lighter, but it

stays stiff,” Over velde says. “ We tr y to do

the same kinds of things with our materials.”

This study explores the “centimeter

scale” (roughly the size range of traditional

paper origami made with hu man hands),

but Overvelde notes such objects would

work the same way if much larger or much

smaller. For now the group is focusing on

the basics: “We’re not people who do ...

manufacturing at small scale,” he says.

“We try to come up with new concepts.”

These concepts have impressed some

of Overvelde’s peers in materials science.

Itai Cohen, who leads similar research

at Cornell University and was not involved

in this study, says the new work is “a real

tour de force” in its research and implica­

tions. “These are all devices that are done

with [the equivalent of] cardboard and dou­

ble ­sided sticky tape—but the real question

is, Could you start to make robotic sys­

tems?” Cohen adds. “In robotic systems,

the number of configurations that you can

go through dictates how much the robot

is able to do, how many [light-diffracting]

gratings you can make or chemical surfaces

you can expose.” — Caroline Delbert

This object flexes into numerous shapes.

Scientific American is a registered trademark of Springer Nature America, Inc. Google Play and the Google Play logo are trademarks of Google LLC. Apple, the Apple logo, iPhone, and iPad

are trademarks of Apple Inc., registered in the U.S. and other countries and regions. App Store is a service mark of Apple Inc.

halfHorizTemplate.indd 2 1/23/20 11:15 AM

© 2020 Scientific American