Physicists have discovered a new way to coat soft robots with materials that allow them to move and function more purposefully.
Physicists have discovered a new way to coat soft robots with materials that allow them to move and function more purposefully. The research, led by the University of Bath, is detailed in a paper published in March 11, 2022 scientific advances.
The study’s authors believe their groundbreaking modeling on “active matter” could mark a turning point in robot design. As the concept evolves, it may be possible to dictate the shape, motion, and behavior of a soft solid not through its natural elasticity, but through human-controlled activity on its surface.
By wrapping a flexible ball (orange) in a layer of tiny robots (blue), researchers can program its shape and behavior. Credit: Jack Binysh
The surface of an ordinary soft material always shrinks into a sphere. Think of the way water rolls off into droplets: Beading occurs because the surface of liquids and other soft materials naturally contract into the smallest area possible – ie a sphere. But active matter can be designed to counteract this tendency. An example of this would be a rubber ball wrapped in a layer of nanorobots, with the robots programmed to work in unison to distort the ball into a new, predetermined shape (e.g. a star).
Active matter should lead to a new generation of machines whose function comes from below. Rather than being controlled by a central controller (like today’s robotic arms are controlled in factories), these new machines would consist of many individual active units that work together to determine the machine’s movement and function. This is similar to how our own biological tissues, such as B. the fibers in the heart muscle.
With this idea, scientists could design soft machines with arms made of flexible materials, powered by robots embedded in their surface. They could also tailor the size and shape of drug delivery capsules by coating the surface of nanoparticles with a reactive, active material. This, in turn, could have dramatic effects on how a drug interacts with cells in the body.
The work on active matter challenges the assumption that the energetic cost of the surface of a liquid or soft solid must always be positive, since a certain amount of energy is always required to create a surface.
dr Jack Binysh, first author of the study, said: “Active matter allows us to look at the familiar rules of nature – rules like the fact that surface tension must be positive – in a new light. Seeing what happens when we break these rules and how we can use the results is an exciting place to do research.”
Corresponding author Dr. Anton Souslov added: “This study is an important proof of concept and has many useful implications. For example, future technologies could result in soft robots that are much softer and better at picking up and manipulating delicate materials.”
For the study, researchers developed a theory and simulations that described a 3D soft solid whose surface is subject to active stresses. They found that these active stresses stretch the material’s surface, dragging the underlying solid with it, and causing a global shape change. The researchers found that the precise shape the solid takes on can then be tailored by altering the elastic properties of the material.
In the next phase of this work – which has already started – researchers will apply this general principle to design specific robots, such as B. soft arms or self-floating materials. You’ll also look at collective behavior – for example, what happens when you have a lot of active solids all packed together.
Reference: “Active Elastocapillarity in Soft Solids with Negative Surface Tension” by Jack Binysh, Thomas R. Wilks and Anton Souslov, March 11, 2022, scientific advances.
DOI: 10.1126/sciadv.abk3079
This work was a collaboration between the Universities of Bath and Birmingham. It was recognized by the Engineering and Physical Sciences Research Council (EPSRC) through New Investigator Award No. EP/T000961/1.
