Liquid robot can split into tiny droplets and reform into a blob

A robot made from magnetic fluid can be made smaller, thinner, or directed to break up with special magnets, which could be useful for delivering drugs into the body

Physics 16 September 2022

A soft robot made from droplets of a magnetic fluid can break itself up and reconstitute itself later when it encounters obstacles or narrow passages. Researchers say it could be used for targeted drug delivery in the future.

Xinjian Fan at Soochow University in Taiwan and his colleagues used droplets of a ferrofluid, in this case magnetic iron oxide nanoparticles suspended in oil, to make a soft robot about a centimetre in size. A set of controllable magnets can direct the robot to move or change shape, as needed, by acting on the nanoparticles.

To make it move through a narrow channel, the researchers used their magnets to squeeze the robot into a thin, elongated shape. They also used magnetic fields to make a centimetre or millimetre-sized robot split into a group of smaller, millimetre or micrometre-sized robots. Another adjustment of the magnetic field directed the parts to merge back into one.

Pietro Valdastri at the University of Leeds in the UK says that this capability may be a “game changer”, as a patient could swallow a drug-carrying robot that could then split inside of them, perhaps in their gastrointestinal tract, so that each tiny robotic droplet could deliver medicine to a specific place. Bradley Nelson at the Swiss Federal Institute of Technology in Zurich says another use may be in removing blood clots in the brain that cause strokes, but adds that creating a strong enough magnetic field to precisely move the robot inside the brain would be challenging.

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Using the new robot in medicine is plausible but very likely far off in the future, says Hamidreza Marvi at Arizona State University. He says it could find more immediate use in lab-on-a-chip devices where chemical processes such as testing for viruses are carried out in a very small space. In these situations, the ferrofluid robots could deliver chemicals necessary for reactions.

Journal reference: Science Advances, DOI: 10.1126/sciadv.abq1677

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