Materials

Building Self-Assembling Robots With Origami, PowerPoint, and an LED Projector

A new photopolymer technique creates self-folding origami structures from PowerPoint slides, which might be used as tiny, medical bots inside the body.

Origami, the art of paper folding, has been around for a long time. Historians are pretty sure that origami as we know it today — think paper cranes and frogs — has its origins in 17th-century Japan. But it's likely that the roots of the practice date back to 1st-century China.

In any case, origami is enjoying an odd resurgence in recent years, as engineers get hip to its usefulness in packaging, robotics, and 3D printing. In fact, origami principles are at the heart of so-called 4D printing, in which two-dimensional patterns unfold into three-dimensional objects by passing through that mysterious fourth dimension — time.

Now comes word that scientists have developed a new technique by which self-folding origami structures can be created using standard LED projector bulbs, inexpensive liquid polymers, and the venerable presentation program PowerPoint.

Yeah, we didn't see it coming, either. 

Researchers at the Georgia Institute of Technology and Peking University recently published details on the new technique, which involves projecting grayscale patterns onto a thin layer of liquid polymer placed in a plate or between two glass slides.

When light from a standard LED projector hits the liquid polymer, particular areas of the slide receive more or less light, depending on the grayscale patterns, which can be easily designed within PowerPoint. After a few seconds, a solid film forms. When this thin sheet is removed and set upon a surface, it folds itself into an origami-style object.
 

The secret to the process is a phenomenon called differential shrinkage — which would also make an excellent band name. Photosensitive materials mixed into the polymer react differently depending on how much light they're exposed to in liquid state. During the solidification phase, those differences result in contrasting stress levels in the solid film. That's differential shrinkage, and it causes the material to fold up on its own in just a few seconds.

While the phenomenon isn't new, other methods of creating self-folding materials rely on extreme temperatures, specialized materials, and dedicated industrial design software. The PowerPoint method simplifies things nicely by using common polymers, standard LED projectors, and software that Bill Gates began hawking in 1990.

Lead researcher Jerry Qi, professor in the Woodruff School of Mechanical Engineering at Georgia Tech, said the origami objects created so far include tiny flowers, tables, capsules, and birds — all about a half an inch in size. Aside from being empirically cool, the process has several potentially useful applications.

“As our method can be generally applied to most photopolymers, many of which are biocompatible, they can used for drug delivery or soft robots for biomedical devices,” Qi said. In other words, the process could be used to create tiny bots that move around inside the body, bringing medicine to precisely where it's needed, then dissolving like a heroic little gummy bear.

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Other researchers are working toward similar goals. For instance, a team at MIT is developing medical origami bots that can be steered through the body using internal magnets and external electromagnetic fields.

Qi said his team's design model could allow for even more complex designs using sophisticated computer-assisted design programs, or by exposing the film to light from both the bottom and the top. For instance, the technique could be used as a platform for 3D electronics.

“One can print the film first, place electronics devices on the film, then let the film fold into 3D shape,” Qi said. “Placing devices is much easier on a 2D sheet then in 3D structure.”

It seems that the ancient art of paper folding has successfully transitioned into the 21st century. Nice work, origami. Welcome back to the fold.

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