Researchers created chain-like metamaterials with motorised hinges that can learn new shapes, forget old ones, and toggle between multiple forms without any central control.
(Nanowerk News) Normal materials have fixed, predetermined responses when a force is applied to them, whereas robots have pre-programmed behaviours. In stark contrast, living materials such as cells and brainless organisms can adapt extremely well to changing conditions. Inspired by nature, the research team created synthetic materials – metamaterials – that learn and adapt without a central “brain”.
The worm-like metamaterials progressively learn how to change shape by being trained on examples. They can forget old shapes and learn new ones, or learn and remember multiple shapes at once and toggle between these shapes. This allows them to perform advanced tasks such as grabbing an object or moving around (locomotion).
Summary of the research. A robotic metamaterial that, with training, learns to change shape. The material can learn complex shapes, one after the other or simultaneously, and even perform ‘lifelike’ actions. (Video: Yao Du)
“The most exciting observation of our research was that learning gives our metamaterials the ability to evolve – once the system starts to learn, the possibilities of where it ends up feel almost limitless,” says Yao Du, PhD candidate in the Machine Materials Lab at the UvA and first author of the paper (Nature Physics, “Metamaterials that learn to change shape”).
The metamaterials are chains of identical motorised hinges linked together by an elastic skeleton. Each hinge has a microcontroller that measures how far it is rotated, remembers its past movements and exchanges information with the hinge’s neighbours. In response to this information, each hinge can exert a torque (a force of rotation), which changes the stiffness and preferred position of each hinge, so that the material learns to adopt a new shape.
The new metamaterials can learn to take on any shape – here, they have learned the letters that spell ‘learn’, or in Dutch: ‘leren’.
Moving forward with materials that learn
The current research builds on previous research (Nature, “Adaptive locomotion of active solids”) from the Machine Materials Lab in ‘brainless’ locomotion, where ‘odd’ objects designed by the team were shown to autonomously roll, crawl and wiggle over unpredictable terrain. However, these metamaterials could not learn or memorise new behaviour.
Du adds: “In future work, we aim to achieve learning time-dependent behaviour instead of changes into a static shape. For example, enabling metamaterials to learn different locomotion gaits, such as crawling or rolling, depending on environmental stimuli. We also plan to investigate so-called stochastic scenarios, where learning happens with noise and uncertainty. In such cases, the system would adapt probabilistically rather than deterministically, improving robustness and flexibility in complex environments.”
