Materials that can be pre-programmed to change shape over time are described in a study published in Nature Communications this week. This research could influence how future self-controlled materials are built, from medical devices to drug release systems.

Previous generations of shapeshifting materials required an external stimulus to change form - light, heat, or pH, for example. However, the new material designed by Sergei Sheiko and colleagues does not need such a trigger. Instead, the researchers can encode a sequence of shape transformations into their material, with each change occurring at a pre-determined time - anywhere from seconds to hours. They program the shapeshifting by introducing two types of bonds to the material, which act as counteracting forces: permanent bonds store the material’s final shape, while temporary bonds control how quickly it can reach this shape. As a proof of concept, the researchers create an artificial blooming flower with petals that gradually open one by one.

These programmed materials may eventually be useful as biomedical implants. They can conceivably be folded up, inserted through minimally invasive surgery, and expand into the desired form once they’ve reached their destination, or evolve with the body over time.