MIT engineers have developed a thread-like robot
that can actively glide through narrow, winding pathways,
such as the vasculature of the brain.
This magnetically-controlled device
is a hydrogel-coated robotic thread or guide
wire that could be used to deliver clot-reducing therapies
and other treatments in response to certain brain blockages,
such as stroke or aneurysms.
To clear blood clots in the brain,
doctors often perform a minimally invasive surgery
in which a surgeon inserts a thin wire through a patient's
main artery typically in the leg or groin,
then manually manipulate the wire up
to the damaged brain vessel.
These medical guide wires used in such procedures
are passive and require surgeons specifically
trained in the task.
They are also made of a core of metallic alloys coated
in polymer, a material that the researchers say
could potentially generate friction and damage vessel
linings if the wire were to get stuck
in a particularly tight space.
To help improve such endovascular procedures,
the MIT engineers combined their work
in hydrogels and magnetic actuation
to produce a magnetically steerable
hydrogel-coated robotic thread, which
they were able to make thin enough
to guide through a life-sized silicone replica of the brain's
blood vessels.
The core of the robotic thread is
made from nickel titanium alloy, a material that
is both bendy and springy.
The team then coated the wire's core in a rubbery paste or ink,
which they embedded throughout with magnetic particles.
Finally, they used a chemical process
they previously developed to coat and bond
the magnetic covering with hydrogel, a material that
does not affect the responsiveness
of the underlying magnetic particles
and, yet, provides the wire with a smooth, friction-free
biocompatible surface.
They demonstrated the robotic thread's precision
and activation by using a large magnet
to steer the thread through an obstacle
course of small rings reminiscent of a thread working
its way through the eye of a needle.
The researchers also tested the thread
in a life-sized silicone replica of the brain's major blood
vessels, including clots and aneurysms
modeled after the CT scans of an actual patient's brain.
The team filled the silicone vessels
with a liquid simulating the viscosity of blood, then
manually manipulated a large magnet around the model
to steer the robot through the vessel's winding narrow paths.
The researchers say the robotic thread can be functionalized,
meaning that features can be added, for example, to deliver
clot-reducing drugs or to break up blockages with laser light.
Their hope is to soon leverage existing technologies to test
the robotic thread in vivo.
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