Sequentially Self-Folding Structures Activated by Light

An improved technique for self-folding gives researchers more control over automated assembly.

(Image courtesy of North Carolina State University.)

(Image courtesy of North Carolina State University.)

A recent advancement in the study of self-folding materials offers researchers a new level of control over the order in which joints are folded.

“A longstanding challenge in the field has been finding a way to control the sequence in which a 2-D sheet will fold itself into a 3-D object,” said Michael Dickey, a professor of chemical and biomolecular engineering at North Carolina State University “As anyone who has done origami – or folded their laundry – can tell you, the order in which you make the folds can be extremely important.”

Using a simple process first developed by Dickey and his colleague Jan Genzer in 2011, the researchers ran pre-stressed flat plastic sheets through an inkjet printer. Once fed into the printer, the pre-stressed seams of the plastic sheet were covered with a bold line of black ink. After drying, the sheets were then exposed to light. As the black ink began to absorb energy from the light, the sheet’s seams began to bend, forming a 3D structure from the once flat sheet.

In their latest research, Dickey and his colleagues have added a series of different colored inks to their experiment, making it possible to control the order of folds on a sheet based on the amount of energy a color absorbs from a light source. Their results are published in Science Advances.

“This is a proof-of-concept paper, but it opens the door to a range of potential applications using a simple and inexpensive process,” said Dickey. “Ultimately, people are interested in self-assembling structures for multiple reasons, from shipping things in a flat package and having them assemble on site to having devices self-assemble in ‘clean’ environments for medical or electronic applications.”

Whether or not color-coded hinges will become a popular method for manufacturing packaging, folding solar cells or other products that need to be transformed by bending, there’s something undeniably charming about the idea of a factory filled with flashing lights where boxes, pyramids and other shapes come to life in a seemingly ethereal manner.

For more folding news, find out how a Japanese Paper Folding Technique Inspires Shape-Shifting Metamaterials.