Surface water, including lakes, canals, rivers, and streams, is a key resource for agriculture, industries, and domestic households. It’s quite literally essential to human activity. However, it’s also very susceptible to pollution, and cleaning it up is rarely easy. But we may have a new ally in this fight: nanobots.

According to the UN, 90% of sewage in developing countries is dumped untreated into water bodies. Industries are also to blame, as they dispose of between 300 and 400 megatons of polluted water in water bodies every year. Nitrate, used extensively by agriculture, is the most common pollutant currently found in groundwater aquifers.

Once these pollutants enter into surface water, it’s very difficult and costly to remove them through conventional methods, and hence, they tend to remain in the water for a long time. Heavy metals have been detected in fish from rivers, which hold risks to human health. Water pollution can also progress to massive disease outbreaks.

The use of nanotechnology in water treatment has recently gained wide attention and is being actively investigated. In water treatment, nanotechnology has three main applications: remediating and purifying polluted water, detecting pollution, and preventing it. This has led to a big demand lately for nanorobots with high sensitivity

However, there’s a technical challenge. Most nanorobots use catalytic motors, which cause problems during their use. These catalytic motors are easily oxidized, which can restrict the lifespan and efficiency of nanorobots. This is where the new study comes in.

A new type of nanorobot

Martin Pumera, a researcher at the University of Chemistry and Technology in the Czech Republic, and his group of colleagues developed a new type of nanorobots, using a temperature-sensitive polymer material and iron oxide. The polymer acts like small hands that pick up and dispose of the pollutants, while the oxide makes the nanorobots magnetic.

The robots created by Pumera and his team are 200 nanometers wide (300 times thinner than human hair) and are powered by magnetic fields, allowing the researchers to control their movement. Unlike other nanorobots out there, they don’t need any fuel to function and can be used more than one time. This makes them sustainable and cost-effective.

In the study, the researchers showed that the uptake and release of pollutants in the surface water are regulated by temperature. At a low temperature of 5ºC, the robots scattered in the water. But when the temperature was raised to 25ºC they aggregated and trapped any pollutants between them. They can then be removed with the use of a magnet.

The nanorobots could eliminate about 65% of the arsenic in 100 minutes, based on the 10 tests done by the researchers for the study. Pundera told ZME Science that the technology is scalable, which is why with his team he is currently in conversations with wastewater treatment companies, hoping to move the system from bench to proof-of-concept solutions.

The study was published in the journal Nature.