A miraculous soft robot has the power to split into smaller units and reassemble back to its original size

The future of drug delivery is bizarre and magnetic.
Rupendra Brahambhatt
Closeup shot of magnetised ferrofluid


Imagine a soft robot moving inside a person’s body that aims to deliver drugs to some cells in the small intestine. Since the different passages that run inside the human body are not of uniform size, there is always a chance of the robot getting stuck in a passage or space that is too narrow or crowded. In that case, the robot may fail to deliver the medicine or even release it where it isn’t supposed to be released, causing further complications.

But what if the soft robot has the power to split into smaller units to get through smaller spaces inside the human body and become whole again when the passage is wide enough? The robot will never get stuck, and surprisingly, a team of researchers has successfully created such a unique soft machine, New Scientist reported. It is called the scale-reconfigurable miniature ferrofluidic robot (SMFR), and the best part is – the researcher can control its motion using magnets.

Ferrofluids are giving superpowers to soft robots

Suggestive image of SMFR.

The team that developed SMFR involved researchers from Taiwan-based Soochow University, Harbin Institute of Technology in China, and Germany’s Max Planck Institute for Intelligent Systems. The reconfigurable soft robot is constructed using oil-based ferrofluid droplets, which mainly comprise iron oxide nanoparticles dipped in hydrocarbon oil. Just like a solid piece of iron, a ferrofluid is also responsive to magnets and magnetic fields.

Since ferrofluids are easy to control and offer great flexibility with fast motion, they are often preferred by scientists for producing shape-shifting soft robots. In 2015, a team of researchers in South Korea created ferrofluid soft robots capable of mimicking an amoeba's movements. Another group of researchers from Arizona State University developed a miniature shape-altering robot in 2021 using ferrofluids.

This year in March, scientists at the Chinese University of Hong Kong (CUHK) came up with a bizarre robot made entirely from a magnetic slime containing borax, detergent, and magnets. According to its creators, this ferrofluidic robot is great at navigating through small spaces, according to its creators.

The ferrofluid particles that make up a liquid robot like SFMR are loosely bound to each other. This loose connection allows the robot to move easily through narrow passages, adjust its shape, and even split under the influence of a magnetic field. During the study, the researchers demonstrated these abilities of SFMR by testing it inside a maze.

Movement of the soft robot through the maze.

The maze incorporated tight and complex passages, hard turns, and obstacles. However, the robot finally got through the maze by shape-shifting, shrinking, elongating, and re-assembling as per the different requirements of its path. Using multiple magnetic fields, the researchers were able to split SFMR into the desired number of units, reassemble them into one again when required, and easily control its all other functions.

The researchers believe that SFMR demonstrates a unique combination of abilities like easy deformation, effortless scale-reconfiguration, and fast locomotion. Such qualities could turn the robot into a great technology for fields related to biomedicine and micro-assembly.

The study authors wrote in the paper, "When in a relatively wide workspace, one can improve the SMFR’s task execution capabilities and efficiency by making them larger through the scale-up strategy; however, when encountering extremely narrow and restricted environments, one can scale them down into a swarm by the splitting strategy, making them very suitable for navigating tubular or slit-like lumen structures with sharply variable cross-sectional dimensions inside the human body.”

SFMR is probably our best bet for targeted drug delivery in the future

Drops of a black colored liquid.

A soft robot like SFMR can give rise to applications capable of delivering drugs to human body parts that would not be accessible otherwise. For instance, according to the researchers, when it comes to delivering medication to body parts like brain cells or skull bones, SFMRs can perform such tasks more precisely than traditional soft robots.

Moreover, SMFRs could also play an important role in developing advanced chip-based virus detection devices. The researchers also reveal that ferrofluids can create many SFMRs of different sizes. However, it is still a developing piece of technology, and a lot of work needs to be done to develop advanced magnet-based controlling systems that could further improve the performance and accuracy of SFMRs.

The authors note, "Achieving some application-oriented tasks, such as SMFR-based targeted cargo delivery, precise local magnetic hyperthermia, or selective occlusion of tumor blood vessels, would also be of great interest and thus another potential direction for future research."

The study is published in the journal Science Advances.


Magnetic miniature soft robots have shown great potential for facilitating biomedical applications by minimizing invasiveness and possible physical damage. However, researchers have mainly focused on fixed-size robots, with their active locomotion accessible only when the cross-sectional dimension of these confined spaces is comparable to that of the robot. Here, we realize the scale-reconfigurable miniature ferrofluidic robots (SMFRs) based on ferrofluid droplets and propose a series of control strategies for reconfiguring SMFR’s scale and deformation to achieve trans-scale motion control by designing a multiscale magnetic miniature robot actuation (M3RA) system. The results showed that SMFRs, varying from centimeters to a few micrometers, leveraged diverse capabilities, such as locomotion in structured environments, deformation to squeeze through gaps, and even reversible scale reconfiguration for navigating sharply variable spaces. A miniature robot system with these capabilities combined is promising to be applied in future wireless medical robots inside confined regions of the human body.