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眀眀眀⸀椀猀挀愀爀⸀挀漀⸀渀稀 㠀 㠀 㠀 㐀㜀㜀
REN357
www.engineeringnews.co.nz 27
manufactured in batches up to
hundreds of metres long. Tests have
shown that a single fibre is capable
of lifting loads of up to 650 times its
own weight. For these experiments
on individual fibres, Örgüç and
Kanik have developed dedicated,
miniaturised testing setups.
The degree of tightening that
occurs when the fibre is heated can
be “programmed” by determining
how much of an initial stretch to give
the fibre. This allows the material
to be tuned to exactly the amount
of force needed and the amount
of temperature change needed to
trigger that force.
The fibres are made using a fibredrawing
system, which makes
it possible to incorporate other
components into the fibre itself.
Fibre drawing is done by creating
an oversized version of the material,
called a preform, which is then
heated to a specific temperature
at which the material becomes
viscous. It can then be pulled, much
like pulling taffy, to create a fibre that
retains its internal structure but is
a small fraction of the width of the
preform.
For testing purposes, the
researchers coated the fibres with
meshes of conductive nanowires.
These meshes can be used as
sensors to reveal the exact tension
experienced or exerted by the fibre.
In the future, these fibres could
also include heating elements such
as optical fibres or electrodes,
providing a way of heating it
internally without having to rely on
any outside heat source to activate
the contraction of the “muscle.”
Such fibres could find uses as
actuators in robotic arms, legs, or
grippers, and in prosthetic limbs,
where their slight weight and fast
response times could provide a
significant advantage.
Some prosthetic limbs today can
weigh as much as 30 pounds,
with much of the weight coming
from actuators, which are often
pneumatic or hydraulic; lighterweight
actuators could thus make
life much easier for those who use
prosthetics. Such fibres might
also find uses in tiny biomedical
devices, such as a medical robot
that works by going into an artery
and then being activated,” Anikeeva
suggests. “We have activation times
on the order of tens of milliseconds
to seconds,” depending on the
dimensions, she says.
To provide greater strength for lifting
heavier loads, the fibres can be
bundled together, much as muscle
fibres are bundled in the body. The
team successfully tested bundles
of 100 fibres. Through the fibre
drawing process, sensors could
also be incorporated in the fibres to
provide feedback on conditions they
encounter, such as in a prosthetic
limb. Örgüç says bundled muscle
fibres with a closed-loop feedback
mechanism could find applications
in robotic systems where automated
and precise control are required.
Kanik says that the possibilities for
materials of this type are virtually
limitless, because almost any
combination of two materials with
different thermal expansion rates
could work, leaving a vast realm of
possible combinations to explore.
He adds that this new finding was
like opening a new window, only
to see “a bunch of other windows”
waiting to be opened.
/www.engineeringnews.co.nz