Scientists have developed a new robotic 'muscle',
thousand times more powerful than a human muscle, which can catapult objects 50
times heavier than itself - faster than the blink of an eye.
Researchers with the Lawrence Berkeley National
Laboratory in US demonstrated a micro-sized robotic torsional muscle/motor made
from vanadium dioxide that is able to catapult very heavy objects over a
distance five times its length within 60 milliseconds.
"We've created a micro-bimorph dual coil that
functions as a powerful torsional muscle, driven thermally or electro-thermally
by the phase transition of vanadium dioxide," said study leader, Junqiao
Wu.
"Using a simple design and inorganic materials,
we achieve superior performance in power density and speed over the motors and
actuators now used in integrated micro-systems," Wu said.
What makes vanadium dioxide highly coveted by the
electronics industry is that it is one of the few known materials that is an
insulator at low temperatures but abruptly becomes a conductor at 67 degrees
Celsius.
This temperature-driven phase transition from
insulator-to-metal is expected to one day yield faster, more energy efficient
electronic and optical devices.
However, vanadium dioxide crystals also undergo a
temperature-driven structural phase transition whereby when warmed they rapidly
contract along one dimension while expanding along the other two.
This makes vanadium dioxide an ideal candidate
material for creating miniaturized, multi-functional motors and artificial
muscles.
Wu and his colleagues fabricated their micro-muscle
on a silicon substrate from a long "V-shaped" bimorph ribbon
comprised of chromium and vanadium dioxide.
When the V-shaped ribbon is released from the
substrate it forms a helix consisting of a dual coil that is connected at
either end to chromium electrode pads.
Heating the dual coil actuates it, turning it into
either a micro-catapult, in which an object held in the coil is hurled when the
coil is actuated, or a proximity sensor, in which the remote sensing of an
object causes a "micro-explosion," a rapid change in the
micro-muscle's resistance and shape that pushes the object away.
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