Three prototype artificial
cephalopod chromatophores are shown in unactuated states. The
chromatophores are made from dielectric elastomer using tape coated with
black carbon grease electrodes.
Credit: University of Bristol
The research team, from the University's Department of Engineering
Mathematics, have designed a smart materials system, inspired by
biological chromatophores, which creates patterns that change and morph
over time and mimic biological patterning.
The paper, published in the Journal of the Royal Society
Interface, describes the design, mathematical modelling, simulation and analysis of a dynamic biomimetic pattern generation system.
The researchers have shown the artificial skin, made from
electroactive dielectric elastomer, a soft, compliant smart material,
can effectively copy the action of biological chromatophores.
Chromatophores are small pigmented cells embedded on cephalopods skin
which can expand and contract and that work together to change skin
colour and texture.
The system achieves the dynamic pattern generation by using simple
local rules in the artificial chromatophore cells, so that they can
sense their surroundings and manipulate their change. By modelling sets
of artificial chromatophores in linear arrays of cells, the researchers
explored whether the system was capable of producing a variety of
patterns.
The researchers found that it is possible to mimic complex dynamic
patterning seen in real cephalopods such as the Passing Cloud display,
which is when bands of colour spread as waves across the skin. This
visual effect acts to distract and divert predators.
Aaron Fishman, Visiting Fellow in Engineering Mathematics, said: "Our
ultimate goal is to create artificial skin that can mimic fast acting
active camouflage and be used for smart clothing such as cloaking suits
and dynamic illuminated clothing.
"The cloaking suit could be used to blend into a variety of
environments, such as in the wild. It could also be used for signalling
purposes, for example search and rescue operations when people who are
in danger need to stand out."
The researchers investigated making bio-inspired artificial skin
embedded with artificial chromatophores using thin sheets (five to ten
millimetre) of dielectric elastomer -- a soft, rubbery material that can
be electrically controlled to be compliant.
In the future the team will consider changing the system to improve
propagation control and to generate new patterns using other local
rules. They will also carry out a more extensive analysis of the
different pattern types that can be achieved under alternative system
parameters, as well as developing the model to simulate patterns in
two-dimensional array systems. The researchers expect this could produce
more patterns, which could resemble those in the natural world.
A video showing the camouflaging in action is available on YouTube, see
https://www.youtube.com/watch?v=dSKqySApDk0.
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