Physicists have discovered a new way to coat soft robots in materials that allow them to move and function in a more purposeful way.
From: The
University of Bath
March 11, 2022 -- Physicists have discovered a new way to
coat soft robots in materials that allow them to move and function in a more
purposeful way. The research, led by the University of Bath, is described today
in Science Advances.
Authors
of the study believe their breakthrough modelling on ‘active matter’ could mark
a turning point in the design of robots. With further development of the
concept, it may be possible to determine the shape, movement and behaviour of a
soft solid not by its natural elasticity but by human-controlled activity on
its surface.
The
surface of an ordinary soft material always shrinks into a sphere. Think of the
way water beads into droplets: the beading occurs because the surface of
liquids and other soft material naturally contracts into the smallest surface
area possible – i.e. a sphere. But active matter can be designed to work
against this tendency. An example of this in action would be a rubber ball
that’s wrapped 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 (say, a
star).
It is
hoped that active matter will lead to a new generation of machines whose
function will come from the bottom up. So, instead of being governed by a
central controller (the way today’s robotic arms are controlled in factories),
these new machines would be made from many individual active units that
cooperate to determine the machine’s movement and function. This is akin to the
workings of our own biological tissues, such as the fibres in heart muscle.
Using
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 in a responsive, active material.. This in turn
could have a dramatic effect on how a drug interacts with cells in the body.
Work on
active matter challenges the assumption that the energetic cost of the surface
of a liquid or soft solid must always be positive, because a certain amount of
energy is always necessary to create a surface.
Dr Jack Binysh,
study first author, said: “Active matter makes us look at the familiar rules of
nature – rules like the fact that surface tension has to be positive – in a new
light. Seeing what happens if we break these rules, and how we can harness the
results, is an exciting place to be doing research.”
Corresponding
author Dr Anton Souslov added:
“This study is an important proof of concept and has many useful implications.
For instance, future technology could produce soft robots that are far
squishier and better at picking up and manipulating delicate materials.”
For the
study, the researchers developed theory and simulations that described a 3D soft
solid whose surface experiences active stresses. They found that these active
stresses expand the surface of the material, pulling the solid underneath along
with it, and causing a global shape change. The researchers found that the
precise shape adopted by the solid could then be tailored by altering the
elastic properties of the material.
In the
next phase of this work – which has already begun – the researchers will apply
this general principle to design specific robots, such as soft arms or self-swimming
materials. They will also look at collective behaviour – for example, what
happens when you have many active solids, all packed together.
This work was a collaboration between the Universities of
Bath and Birmingham. It was funded by the Engineering and Physical Sciences
Research Council (EPSRC) through New Investigator Award no. EP/T000961/1.
https://www.bath.ac.uk/announcements/the-next-generation-of-robots-will-be-shape-shifters/
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