Scientists at the University of California, San Diego, have developed tiny robots that could one day remove carbon dioxide from the oceans, helping to mitigate the effects of climate change. Their proof of concept study was published in the journal Angewandte Chemie.

The researchers developed “micromotors” that can rapidly decarbonate water. They do this using an outer polymer surface that holds an enzyme called carbonic anhydrase. This speeds up the reaction between carbon dioxide and water to form bicarbonate, which can then be converted to solid calcium carbonate using calcium chloride in the water. Calcium carbonate is much safer, being found in things like seashells.

Each tiny tube-shaped robot, measuring six micrometers long, is entirely autonomous, so they can be deployed into the water and left to their own devices. "We're excited about the possibility of using these micromotors to combat ocean acidification and global warming," said co-first author of the study Virendra V. Singh in a statement. How they would be deployed on a large scale isn't clear at the moment, though.

In tests, the micromotors removed 90% of carbon dioxide from a solution of deionized water, and 88% from a sea water solution, in just five minutes. "In the future, we could potentially use these micromotors as part of a water treatment system, like a water decarbonation plant," said co-author on the study Kevin Kaufmann.

One issue, though, is that very small amounts of hydrogen peroxide must be added to the water to supply the "fuel" the micromotors need to move. In water solutions containing 2 to 4% hydrogen peroxide, they can reach speeds of more than 100 micrometers per second using the reaction between the hydrogen peroxide and their inner platinum surface, which generates a stream of oxygen gas bubbles.

However, the researchers hope that in the future they might be able to use the water itself as a power source. "If the micromotors can use the environment as fuel, they will be more scalable, environmentally friendly and less expensive," said Kaufmann.

And with ocean acidification becoming a rapidly growing problem, this could be part of a solution to maintaining biomes in the face of increasing man-made climate change.

^{Image in text: An illustration of the micromotors in action. UC San Diego.}