An international research group based in China has developed a microscopic material that behaves like a miniature predator: it moves itself in an aqueous environment, "sniffs" and captures uranium ions. The discovery has the potential to change the approach to the extraction of nuclear fuel from seawater and to the purification of radioactively contaminated water bodies.
"Micromotor" that hunts uranium
The new material is a micromotor based on a metal-organic framework (MOF), powered by light. It was developed at the Qinghai Institute of Salt Lakes of the Chinese Academy of Sciences and was accepted for publication on March 24 in the peer-reviewed journal "Nano Research". The particles have a spongy structure and a diameter of only about 2 micrometers – many times thinner than a human hair – and are designed to work stably in water for extended periods.
By adding a small amount of hydrogen peroxide, these microparticles generate thrust and move in the water at a speed of approximately 7 micrometers per second. Under the influence of light, their speed almost doubles, which gives the micromotors an additional "solar" boost. In laboratory conditions, they have absorbed up to 406 milligrams of uranium per gram of material, after which they have converted it into a stable mineralized form, convenient for extraction and safe storage.
"When working with light, this material can move itself, which makes the approach significantly more energy efficient and environmentally friendly compared to traditional static sorbents," explains lead researcher Yunquan Zhou in an interview with the "South China Morning Post".
"Predator-prey" dynamics at the microscale
In a series of controlled experiments, scientists observed emergent behavior resembling the biological dynamics between predator and prey. When they combine active micromotors with passive colloidal particles, the system begins to exhibit patterns similar to pursuit, avoidance, and coordinated swarming, and these patterns change depending on the concentration of "fuel". A significant part of the experimental work was done by Ikram Muhammad, a member of the team.
According to Zhou, the concept is not limited to uranium. In the future, similar micromotors could also be used to capture other strategically important elements in an aqueous environment, such as rubidium and cesium, which are key to high-tech applications and energy.
Strategic context and remaining challenges
The research comes at a time when China is rapidly expanding its nuclear energy program, but remains largely dependent on imported uranium. Estimates suggest that about 4.5 billion tons of uranium are dissolved in the world's oceans, but its extremely low concentration – on the order of 0.003 parts per million – has long made its extraction technically difficult and economically unprofitable.
At the beginning of the year, state-related Chinese nuclear structures announced that they had succeeded in extracting uranium from seawater on a scale of several kilograms through an offshore platform in the South China Sea – another step in the country's ambitious course towards extracting nuclear fuel directly from the ocean. Such developments highlight the strategic importance of any technology that can accelerate or reduce the cost of this process.
Despite the promising results, Zhou emphasizes that the micromotor technology is still in its initial stage. Environments with a high salt content – such as the salt lakes where the institute traditionally works – currently reduce the efficiency of the system. In order to find a place in real applications, additional engineering solutions will be needed to improve stability and efficiency in different conditions.
The team continues to work on optimizing the material and scaling up the process. If the challenges are overcome, "predatory" MOF micromotors could become an important tool both for extracting uranium from dilute water sources and for cleaning radioactive wastewater – with potentially great importance for the future of nuclear energy and the environment.