Clever Spray Turns Inanimate Objects Into Biocompatible Millirobots, Activated by a Magnetic Field

Everything from cotton thread to plastic pipe can become a robot when treated with M-spray — and the coating is biocompatible.

Researchers from the City University of Hong Kong, Chinese Academy of Sciences, and the Shenzhen Institute of Artificial Intelligence and Robotics for Society have unveiled a spray that turns otherwise-inanimate objects into magnetically-driven "millirobots" suitable for medical use.

"Our idea is that by putting on this 'magnetic coat,' we can turn any objects into a robot and control their locomotion," project lead Dr. Shen Yajing explains. "The M-spray we developed can stick on the targeted object and 'activate' the object when driven by a magnetic field. All the raw materials of M-spray, namely PVA, gluten, and iron particles, are biocompatible. The disintegrated coating could be absorbed or excreted by the human body."

The M-spray works by coating any object in a 0.1-0.25mm thick layer, retaining the size, form, and structure of the original object but allowing it to be magnetized then heat-treated to solidify. Once magnetized, the object can be controlled by moving a magnetic field — allowing the tiny robots to crawl, flip, walk, and roll across numerous different surfaces.

The M-spray-treated "millirobots" are controlled, or deactivated, using a magnetic field. (📹: City University of Hong Kong)

To prove the concept, the team set about creating a soft "reptile" robot, a multi-footed robot, a walking robot, and a rolling robot, made from cotton thread, origami, polydimethylsiloxane (PDMS) film, and plastic pipe respectively — all treated with M-spray. The treated millirobots could also be modified post-creation by fully wetting the solidified M-spray and changing the distribution and alignment of its magnetic particles.

As part of the study, M-spray was tested in vivo with rabbits: A treated capsule was introduced then tracked via radiological imaging, and when it reached the target area the coating was disintegrated by application of an oscillating magnetic field. "The controllable disintegration property of M-spray enables the drug to be released in a targeted location," Shen says, "rather than scattering in the organ."

The team's work has been published in the journal Science Robotics under closed-access terms.

Gareth Halfacree
Freelance journalist, technical author, hacker, tinkerer, erstwhile sysadmin. For hire:
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