Unless it’s melted in the microwave or shredded by a recycling machine, plastic typically doesn’t change shape. That’s an advantage when it comes to holding soda or creating door panels for cars. But plastic that changes shape over time could be helpful for some things, such as creating medical devices.
That’s one reason professor of polymer chemistry Sergei Sheiko and a team of researchers at the University of North Carolina, Chapel Hill, developed a hydrogel polymer designed to change shape over minutes or hours, reports Ian Sample at The Guardian.
To demonstrate the properties of the material, one of Sheiko’s graduate students engineered a pink and red artificial flower out of the material just a few centimeters across. In a mesmerizing video, the artificial flower seems to awaken and bloom over time.
“I was so surprised when I first saw the flower. It looks so real,” Sheiko tells Sample. “It’s a dead piece of material. If you remove the paint, it’s just white polymer. It’s like we introduced life into the material.” Details of the material appear in the journal Nature Communications.
Other researchers have developed similar morphing materials, reports Sandrine Ceurstemont at New Scientist. But those require an outside stimuli like heat, light or pH changes to initiate the shape transformations. This new material, however, will initiate the change itself after a particular period of time. “In certain situations, like inside your body or in space, external triggers are not permissible or are ineffective,” Sheiko tells Ceurstemont. “You simply want an object to change shape at a given moment.”
The team used a soft polymer and modified its molecular structure to develop the shape-shifting plastic. According to Charles Q. Choi at Live Science, the material has two types of chemical bonds. One set of bonds is elastic, holding the energy that powers the shape-shifting. The other set of bonds controls how long the shape-shifting process takes place. By tweaking the percentage of these bonds, the researchers can determine whether the polymer will change shape in hours or mere seconds.
The most obvious use would be in medicine, where implants could be introduced through small, non-invasive incisions before unfolding into their final shape. “The general motivation behind this work was to endow synthetic materials with functions and properties of living tissues,” Sheiko tells Choi. He also says the technology is just at the beginning. He’d like to figure out to code a timed delay into the shape-shifting and investigate a way to produce a sequence of multiple shapes.