A new technique for producing self-folding three-dimensional origami structures from photo-curable liquid polymer materials created these tiny samples, held in a hand for size comparison. Photo: Rob Felt.
By John Toon
Researchers have found a new use for the ubiquitous PowerPoint slide: producing self-folding three-dimensional origami structures.
The technique involves projecting a grayscale pattern of light and dark shapes onto a thin layer of liquid acrylate polymer placed in a plate or between two glass slides. A photoinitiator material mixed into the polymer initiates a crosslinking reaction when struck by the patterned light produced by an ordinary LED projector, causing a solid film to form. The complicated interaction between the evolution of the polymer network and volume shrinkage during photo curing causes areas of the polymer that receive less light to exhibit more apparent bending behavior.
When the newly created polymer film is removed from the liquid polymer, the stress created in the film by the differential shrinkage causes folding to begin. To make the most complex origami structures, the researchers shine light onto both sides of the structures. The patterning comes from simple PowerPoint slides.
Origami structures produced so far include tiny tables, capsules, flowers, birds, and the traditional miura-ori fold — all about a half-inch in size. The origami structures could have applications in soft robots, microelectronics, soft actuators, mechanical metamaterials, and biomedical devices.
“The basic idea of our method is to utilize the volume shrinkage phenomenon during photo-polymerization,” said Jerry Qi, a professor in Georgia Tech’s Woodruff School of Mechanical Engineering. “During a specific type of photopolymerization, frontal photopolymerization, the liquid resin is cured continuously from the side under light irradiation toward the inner side. This creates a nonuniform stress field that drives the film to bend along the direction of light path.”
Details of the work were published in the journal Science Advances. The research was supported by the National Science Foundation, the Air Force Office of Scientific Research, and the Chinese Scholarship Council. Researchers from Peking University also contributed to the project.