Adebola Oyefusi holding a small piece of foldable plastic

When origami meets chemistry

Inspired by origami, the Japanese art of paper-folding, UWM chemist Jian Chen integrated the concept into his research.

Chen developed a technique in which a common plastic material is treated with chemicals in a certain pattern. This allows the material to fold itself into complex 3-D shapes and, later, revert to its original form.

Chen and graduate student Adebola Oyefusi use the technique on sheets of Nafion foil – a commercial polymer. With the discovery, the Nafion film can fold, be “erased,” and then be reprogrammed to fold into a completely different shape. It can even achieve configurations as complicated as the iconic origami swan.

Shape-memory materials are not new, but this technique adds another dimension of practicality to them. “The shapes of traditional shape-memory polymers had to be made using external mechanical force, such as a physical mold or template,” says Chen, an associate professor of organic chemistry. “Prior to our work, no one had ever applied the chemical patterning to shape-memory polymers.”

Watch plastic fold itself into the shape of a bird.

It could provide a method for making reprogrammable master molds that would save time and money compared to an alternative like 3-D printing. The two scientists also wanted to provide ways to repurpose mass-produced polymers, such as Nafion or laminate, which are difficult to recycle.

The process involves applying a pattern onto base-treated Nafion foil sheets using hydrochloric acid. When heated to a specific temperature, the sheet shrinks along the pattern’s lines, forming creases where the fold occurs. Parts not treated with the chemicals stay flat. To revert the sheets to a flattened state, the entire form is treated with hydrochloric acid and again heated to a specific temperature.

The process may provide insight into chemically modifying other properties of polymers, such as waterproofing, which could then be tuned or reversed.