Researchers have created a material with a soft surface that can adapt to objects in nature by reshaping itself dynamically to mimic theirs, a property that can have broad application in soft robotics, augmented reality, biomimetic materials, and wearable technology, they said. A team of engineers at Duke University developed the soft surface, which plays on the material principle of being able to control on the fly a material’s properties or the mechanical behaviors of an engineered object, observed Xiaoyue Ni, assistant professor of mechanical engineering and materials science at Duke, who worked on the research.
“We are focusing on engineering the shape of matter that hasn’t been predetermined, which is a pretty tall task to achieve, especially for soft materials,” he said in an article posted to Duke’s website.
To do this, the material uses a combination of electromagnetic actuation, mechanical modeling, and machine learning to form new configurations, researchers said. The material even can learn to adapt to variations that occur, such as changing environments or broken elements, researchers said. Ultimately, the work paves the way for materials that can sense and perceive requirements or information from users and then adapt themselves to serve functions dynamically and interactively, they said.
Flipping the Script
While scientists have been able to morph matter previously, it was usually done after being programmed to respond to a certain external stimuli—such as light or heat—in a certain way. The team’s research is a twist on this in that it’s created material that is in and of itself programmable and controllable and able to change and reconfigure into any range of shapes as often as it likes, researchers said.
The material is composed of a grid of snake-like beams eight micrometers thick—about the thickness of a cotton fiber—made of a thin layer of gold encapsulated by a thin polymer layer. The beams are light, which is what allows them to be manipulated and deformed by magnetic forces, researchers said.
To generate these forces locally, researchers put the surface into a low-level static magnetic field, the voltage changes of which create a complex but easily predictable electrical current along the golden grid. This drives the out-of-plane displacement of the grid, allowing for the speed that enables the accurate mimicry of “a continuous shape-shifting process in nature,” Ni said in the article. “One key advance is the structural design that enables an unusual linear relationship between the electrical inputs and the resulting shape, which makes it easy to figure out how to apply voltages to achieve a wide variety of target shapes.”
Indeed, the surface boasts a wide array of morphing and mimicking skills, researchers demonstrated in their work. It can bulge along its surface and move like a cat trying to claw its way out from under a blanket, or have oscillating wave patterns, they said. It also can form a liquid drop dripping onto a solid surface.
What’s even more compelling is not that the material reproduces these shapes dynamically, but that it can do so at any speed or acceleration desired, Ni said. “It currently takes about two minutes to achieve a new shape, but we hope to eventually improve the feedback system and learning algorithm to the point that it’s nearly real-time,” he said in the article.
Materials with Dynamic Purpose
The surface also can learn to create shapes and patterns on its own, moving with trial and error using cameras that monitor its changing surface. As it applies voltages to move into different shapes, a learning algorithm monitors via 3D images to figure out what effects the different inputs have on the surface’s shape, researchers said.
“The control doesn’t have to know anything about the physics of the materials, it just takes small steps and watches to see if it’s getting closer to the target or not,” Ni said.
This approach also allows the material to adapt to damage, unexpected physical constraints, or environmental change, a property researchers demonstrated in the lab. In one experiment, for example, they showed the material learning to mimic a bulging mound despite one of its beams being cut; while in another, the surface formed a similar shape despite scientists’ attaching a weight to one of the grid’s nodes, researchers reported.
Researchers published a paper on their work in the journal Nature.
Scientists envision numerous applications for the material, including the creation of programmable and robotic materials. In fact, moving forward, Ni and his team aim to to create robotic metasurfaces with integrated shape-sensing functions to perform real-time shape mimicking of complex, dynamic surfaces in nature, such as the water ripples, fish fins, or even the human face, he said.
Researchers also may investigate integrating electronics into the current surface prototype, such as on-board power sources, sensors, computational resources, or wireless communication capabilities, to extend its functionality, they said.