Shape-Shifting Kirigami Balloon From Harvard Might Reshape Soft Robotics

The kirigami balloon from Harvard may also enhance space exploration and surgical devices.
Chris Young

When we think of balloons, we think of red ones rising into blue skies, or clowns folding long balloons into animals for kids. But these may be joined by a new shape-shifting balloon device inspired by the Japanese paper-cutting art of kirigami, according to a new study recently published in the journal Advanced Materials.

This is significant because shape-shifting balloons go beyond party tricks — and might bring advancements in medical tools, soft robotics, and other fields.


Kirigami art inspires scientific progress

In recent years, scientists have increasingly drawn inspiration from kirigami — similar in form to origami. In the latter, people cut and fold paper — a process scientists have studied to develop new applications in various fields, like soft robotics machines and slip-proof shoes.

A team of researchers from the Harvard John A. Paulson School of Engineering and Applied Sciences (SEAS) designed the balloon device that morphs into pre-programmed shapes.

They based their system on kirigami sheets embedded into the inflatable device, and when it expands, the cuts within the kirigami guide its growth, expanding some areas and constricting others.

Harvard's 'inverse' design strategy

To make shapeshifting balloons more user-friendly, the Harvard SEAS team developed an inverse design strategy: they made a new algorithm that pinpoints the optimal design for the kirigami inflatable device so that it easily assumes the desired shape once inflated.

Kirigami balloon
The balloon morphs into a hook. Source: Bertoldi Lab / Harvard SEAS

"This work provides a new platform for shape-morphing devices that could support the design of innovative medical tools, actuators and reconfigurable structures," said Katia Bertoldi, the William and Ami Kuan Danoff Professor of Applied Mechanics at SEAS and senior author of the study, in a Harvard press release.

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Kirigami balloon
Aggregate local changes combine to inflate the balloon. Source: Bertoldi Lab / Harvard SEAS

Global applications for precise balloon morphing

The researchers can mold shapes globally for large-scale shapes or locally for small features; they were able to make kirigami balloons in the shapes of calabash gourds, hooks, and vases, demonstrating that the approach can be used mimic a large range of forms.

"By controlling the expansion at every level of the kirigami balloon, we can reproduce a variety of target shapes," said Lishuai Jin, co-first author of the paper and a graduate student at SEAS.

In the near future, the researchers aim to use their kirigami balloons as shape-changing actuators for soft robots. As self-shaping balloon developments continue, the researchers' devices could have a wide range of applications — from space-exploring soft robots to minimally-invasive surgical devices.