Tiny self-propelled devices called micromotors can be designed to move through wastewater, targeting specific contaminants. They have the unique ability to carry functional materials or coatings that can adsorb or react with pollutants, helping to remove them from the water.

But what if they could be optimized to also produce energy?

Cleaning water and generating ammonia

Researchers at the Institute of Chemical Research of Catalonia (ICIQ) in Spain have created autonomous micromotors that move around efficiently cleaning wastewater as they go and producing ammonia that could be used as a renewable energy source.

The motors will now be tuned using an AI technique created at the University of Gothenburg to optimize their outcomes making them super-efficient cleaning and energy-generating machines.

The devices consist of a silicon and manganese dioxide tube with a bubble release mechanism at one end that functions due to chemical interactions. The tube moves in the water with the aid of these bubbles which operate as a motor.

The chemical component laccase, which coats the micromotors, expedites the transformation of urea, which is present in contaminated water, into ammonia upon immediate contact with the device. The ammonia can then be converted into hydrogen, a green and clean energy source.

“This is an interesting discovery. Today, water treatment plants have trouble breaking down all the urea, which results in eutrophication when the water is released. This is a serious problem in urban areas in particular,” said Rebeca Ferrer, a PhD student at Doctor Katherine Villa´s group at ICIQ.

Improving the design

In order for the tubes to effectively cleanse the water, the scientists must now improve their design. To do this, they need to observe how these components move and how long they function when submerged. This, however, is challenging to do under a microscope since the bubbles generated by the devices obstruct the view.

Luckily, it is now feasible to approximate the movements of the micromotors thanks to an artificial intelligence technique created by Gothenburg University researchers. Machine learning algorithms make it possible to monitor multiple motors swimming around in liquid at the same time.

“If we cannot monitor the micromotor, we cannot develop it. Our AI works well in a laboratory environment, which is where the development work is currently under way,” said Harshith Bachimanchi, a PhD student at the Department of Physics, University of Gothenburg.

Since micromotors can travel and carry out specified activities on a microscale independently, they have become a promising tool for environmental remediation. This latest development is bound to add to their attractiveness, however, the scientists do not know when they will be able to unleash their devices on a large scale. For the time being, they continue to work on this important innovation with hopes of making it universally viable in the coming years.

The study is published in the journal Nanoscale.