Micro-robots for cleaning radioactive waste

Researchers have succeeded in developing tiny robots that move by themselves and are able to remove radioactive uranium from sewage

[Translation by Dr. Moshe Nachmani]

According to a number of experts, in nuclear energy lies the ability to meet the growing energy demands of humanity, without producing greenhouse gases. However, scientists need to find a way to remove radioactive isotopes, both from the waste produced by nuclear power plants and from the environment in the event of a spill. Now, researchers have succeeded in developing tiny self-moving robots capable of removing radioactive uranium from sewage. The accidental release of radioactive waste, as happened, for example, in the nuclear power plant disasters in Chernobyl and Fukushima, presents a great threat to the environment, to man and to wildlife. Scientists have succeeded in developing materials designed to capture, separate, remove and wash radioactive uranium from water, but these materials are limited in their activity.

One of the most promising recent approaches in this field is the use of metal-organic frameworks (MOFs) - compounds that are able to capture specific substances, including radioactive uranium, within their porous structures. A team of researchers wanted to add a micromotor to this type of material called a zeolite imidazole framework (ZIF-8) consisting of zinc ions and organic ligands in order to test whether the new material could quickly clean up radioactive waste. In order to make the microrobots move independently, the researchers designed rod-shaped zeolitic imidazole skeletons whose diameter is 15 times smaller than the thickness of a human hair.

The researchers added iron atoms and iron oxide nanoparticles in order to stabilize the structures and add a magnetic character to them, respectively. Catalytic platinum nanoparticles attached to one of the ends of each of the rods were designed to convert hydrogen peroxide type fuel in the water into oxygen bubbles, bubbles that propelled the microrobots at a speed 60 times their length per second. In a simulated system of radioactive waste, the micro-robots managed to remove 96% of the amount of uranium in just one hour. The researchers collected the rods full of uranium with the help of a magnet and then separated the uranium itself from them, thus making it possible to recycle the activity of the tiny robots. The researchers say that the results of this experiment indicate that one day, not far in the future, autonomously moving micro-robots will be able to help contain and clean up radioactive waste.

The scientific article