Now researchers at MIT, Harvard
University and Seoul National
University have
engineered a soft autonomous robot that moves via peristalsis, crawling across
surfaces by contracting segments of its body, much like an earthworm. The
robot, made almost entirely of soft materials, is remarkably resilient: Even
when stepped upon or bludgeoned with a hammer, the robot is able to inch away,
unscathed. Researchers say such a soft robot may be useful for navigating rough
terrain or squeezing through tight spaces. The robot is named ‘Meshworm’ for
the flexible, meshlike tube that makes up its body. They created artificial
muscle from wire made of nickel and titanium -- a shape-memory alloy that
stretches and contracts with heat. They wound the wire around the tube, creating
segments along its length, much like the segments of an earthworm. They then
applied a small current to the segments of wire, squeezing the mesh tube and
propelling the robot forward.
The team set out to design a similar soft,
peristalsis-driven system. The researchers first made a long, tubular body by
rolling up and heat-sealing a sheet of polymer mesh. The mesh, made from
interlacing polymer fibers, allows the tube to stretch and contract, similar to
a spring. They then looked for ways to create artificial muscle, ultimately
settling on a nickel-titanium alloy. Depending on the ratio of nickel to
titanium, the alloy changes phase with heat. Above a certain temperature, the
alloy remains in a phase called austenite -- a regularly aligned structure that
springs back to its original shape, even after significant bending, much like
flexible eyeglass frames. Below a certain temperature, the alloy shifts to a
martensite phase. The researchers fabricated a tightly coiled nickel-titanium
wire and wound it around the mesh tube, mimicking the circular muscle fibers of
the earthworm. They then fitted a small battery and circuit board within the
tube, generating a current to heat the wire at certain segments along the body:
As a segment reaches a certain temperature, the wire contracts around the body,
squeezing the tube and propelling the robot forward.
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