Zeang Zhao and colleagues at Georgia Tech have published a new technique for creating self-folding origami of a sheet of polymer.  Real deal 4D printing, the little structure starts as a flat sheet and folds up into the desired shape, a la Origami.
Note to self: these days, all engineering students should do a unit in Origami, no?
What is even cooler is how it works.
The folds are created by “photopolymerization’. The polymer shrinks when exposed to light, and differential exposure creates tension due tu the different shrinkage. When released, the polymer crinkles and bends. This crinkling is undesirable for many cases, but this team has turned it into a virtue: controlled folding.
The folding is controlled by projecting carefully designed patterns and stripes of light and dark. Ta dal.
The demo uses an ordinary LED projector and a powerpoint slide with the requisite pattern. Cheap and simple! And the process is fine tuned by changing the pattern as the polymer cures—the folding structure encoded in a slide show.
“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 light from an ordinary LED projector, causing a solid film to form. A light-absorbing dye in the polymer serves as a regulator for the light. Due to the complicated interaction between the evolution of the polymer network and volume shrinkage during photo curing, areas of the polymer that receive less light exhibit more apparent bending behavior.”
The paper gives details of the specific method, along with illustrations of complicated Origami structures created entirely by this method . Many of the details depend on the specific polymer, but the technique should work for other materials.
Nice work, all.
- John Toon, PowerPoint & LED Projector Enable New Technique for Self-Folding Origami, in Research News. 2017. http://www.news.gatech.edu/2017/04/28/powerpoint-led-projector-enable-new-technique-self-folding-origami
- Zeang Zhao, Jiangtao Wu, Xiaoming Mu, Haosen Chen, H. Jerry Qi, and Daining Fang, Origami by frontal photopolymerization. Science Advances, 3 (4) 2017. http://advances.sciencemag.org/content/3/4/e1602326.abstract