A domestic research team has developed a soft robot that can pass through obstacles like flowing water and perform its functions. When applied in medicine, it is expected to wrap around and eliminate cancer cells and deliver drugs within patients' bodies.
A joint research team from Seoul National University and Gachon University announced on the 22nd that they have developed a robot that can change its shape freely like water and move stably. The research results were published that day in the international journal Science Advances.
The research team named the robot they developed PB, which stands for 'Particle-armored liquid roBot.' PB is a form that is inside a liquid and is surrounded by hydrophobic particles on its surface. Hydrophobic particles have the property of repelling water very strongly, similar to how rain on a lotus leaf does not seep in but instead forms droplets that roll away because the leaf's surface is covered with hydrophobic material. Hydrophobic particles do not mix with liquids but stick to the surface, acting as a protective armor.
Similar concepts had been studied previously in the form of 'liquid marble.' Liquid marble refers to a structure designed to roll by surrounding droplets of liquid with superhydrophobic particles, effectively 'dressing' the droplet so it does not get wet and can be rolled around. However, existing liquid marbles had the drawback of being difficult to deform due to the small amount of particles, and their structures were easily broken.
This liquid robot uses significantly more hydrophobic particles, making its protective layer much sturdier. As a result, the liquid droplet can change into various shapes without bursting. The research team explained that the liquid robot can pass between small pillars like water seeping through or swallow glass beads and seamlessly merge with other PBs, reacting flexibly like a living organism. It can even move swiftly across the water surface to reach dry ground.
The research team successfully rolled the liquid robot to deliver specific substances. Just as white blood cells engulf bacteria, the liquid robot encapsulated substances to deliver antidotes or safely collect them. This indicates potential future development of technology that can wrap around and eliminate only cancer cells or accurately deliver drugs to specific areas within the body.
The research team noted, 'This time we used water as the liquid inside the robot, but next we could replace it with a liquid that adheres better to hydrophobic particles.' They could also consider a form that seeks out desired targets, such as attaching magnetic particles to the surface for movement via an external magnet, or using substances that only adhere to cancer cells, similar to guided missiles.
Professor Kim Ho-young from the Department of Mechanical Engineering at Seoul National University stated, 'This robot has the advantage of being entirely liquid except for the edge particles, allowing it to decompose after transporting specific substances.' He noted that in this study, harmful Teflon powder was used as hydrophobic particles to implement the robot, but they are currently developing a liquid robot that can be applied to the human body using plant-derived components like pollen.
References
Science Advances (2025), DOI: https://doi.org/10.1126/sciadv.adt5888