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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