Science -- March 20, 2022: Soft robots can now be coated in materials that allow them to move and function
more purposefully, according to physicists. The study, performed by the University of Bath in the United Kingdom,
was published today in Science Advances.
The study's authors feel that their breakthrough modeling on 'active matter' could be a watershed moment in robot design. With further refinement of the concept, it may be feasible to decide the shape, movement, and behavior of a soft solid based on human-controlled activity on its surface rather than its natural elasticity.
An ordinary soft material's surface always shrinks into a sphere. Consider how water condenses into droplets: the surface of liquids and other soft materials spontaneously compresses into the smallest surface area possible, resulting in a sphere. Active matter, on the other hand, can be tailored to counteract this propensity. A rubber ball encased in a layer of nano-robots, where the robots are programmed to work in unison to distort the ball into a new, pre-determined shape, is an example of this in action (say, a star).
It is hoped that active matter will lead to a new generation of machines with bottom-up functionality. Rather than being directed by a single controller (like today's factory robotic arms are), these new machines would be made up of several independent active units that work together to define the machine's movement and function. This is similar to how our actual biological tissues, such as heart muscle fibers, work.
Scientists could use this concept to create soft machines with flexible arms that are powered by robots embedded in their surface. By coating the surface of nanoparticles in a responsive, active substance, they might also modify the size and shape of drug delivery capsules. This, in turn, could have a significant impact on how a medicine interacts with bodily cells.
The idea that the energetic cost of a liquid or soft solid's surface must always be positive because a certain amount of energy is required to produce a surface is challenged by active matter research.
The study's first author, Dr. Jack Binysh, said: "The familiar rules of nature, such as the requirement for positive surface tension, are viewed in a new light by active matter. It's a fun area to perform study to see what happens when we break these restrictions and how we can use the results."
Dr. Anton Souslov, a correspondent author, added: "This research is a critical proof of concept with numerous applications. Soft robots, for example, could be far squishier and better at picking up and manipulating delicate things in the future."
The researchers created theory and simulations to characterize a 3D soft solid with active stresses on its surface for the study. They discovered that active strains cause the material's surface to expand, pushing the solid beneath it along with it and generating a global shape shift. The researchers discovered that by adjusting the material's elastic characteristics, the specific shape adopted by the solid could be adjusted.
The researchers will use this fundamental idea to design specific robots, such as soft limbs or self-swimming materials, in the next phase of this effort, which has already begun. They'll also study at collective behavior, such as what occurs when a large number of active solids are crammed into a small space.
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University of Bath. "The next generation of robots will be shape-shifters." ScienceDaily. www.sciencedaily.com/releases/2022/03/220311141417.htm>
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Materials provided by University of Bath. Note: Content may be edited for style and length.
Journal Reference:
Jack Binysh, Thomas R. Wilks, Anton Souslov. Active elastocapillarity in soft solids with negative surface tension. Science Advances, 2022; 8 (10) DOI: 10.1126/sciadv.abk3079