By turning to the paper-based art form of kirigami for inspiration, a team of Harvard researchers has developed a system for programmable balloons that can take on all kinds of “crazy” shapes when inflated. More than just a vehicle to produce impressive showpieces, the researchers hope the platform can be used to produce new kinds of medical devices or actuators for soft robots.
The work was carried out by researchers at the Harvard John A. Paulson School of Engineering and Applied Sciences, who set out to develop materials that can mold balloons into different shapes. Kirigami is a variation of origami in which the paper is not just folded but also cut in order to create the finished product, and this approach lent itself quite nicely to the team's objectives.
The kirigami sheets, which feature very strategically placed patterns of cuts that the team likens to pixels that form an image on a 2D surface, are embedded in the balloon. As the balloon is inflated, the cuts enable it to expand more in some places while being constricted in others, resulting in a highly controllable inflatable device that assumes some rather irregular shapes.
“By only varying two parameters of the pixels, we can program all different kinds of crazy shapes into the kirigami balloons, including bends, twists and expansions,” says Antonio Elia Forte, co-first author of the study. “Our strategy allows us to automatically design a morphable balloon starting from the shape that you need. It’s a bottom-up approach that for the first time harnesses the elasticity of the material, not only kinematic.”
The team also developed an inverse algorithm that could simply be programmed to create a desired shape, with the machine then determining the necessary pixel size and sheet design to produce it. As a way of demonstrating this, the team programmed the balloon to take on the shape of squashes, hooks, and vases.
“By controlling the expansion at every level of the kirigami balloon, we can reproduce a variety of target shapes,” Lishuai Jin, a graduate student at SEAS and co-first author of the paper.
While the researchers imagine this platform could be used to produce new medical devices for surgeons or even structures for space exploration, they will initially focus their attention on shape-changing actuators for soft robots.
The research was published in the journal Advanced Materials, while the video below offers a look at the system in action.
Source: Harvard University
