Tiny carbon-capturing motors to fight global warming

Researchers, including one of Indian-origin, have developed machines smaller than the width of a human hair that can rapidly remove carbon dioxide from water, an advance that could help combat ocean acidification and global warming.
Researchers have designed enzyme-functionalised micromotors that rapidly zoom around in water, remove carbon dioxide and convert it into a usable solid form.
"We're excited about the possibility of using these micromotors to combat ocean acidification and global warming," said co-first author Virendra V Singh, a postdoctoral scientist at the University of California, San Diego.
In their experiments, researchers demonstrated that the micromotors rapidly decarbonated water solutions that were saturated with carbon dioxide.

Within five minutes, the micromotors removed 90 per cent of the carbon dioxide from a solution of deionised water.
The micromotors were just as effective in a sea water solution and removed 88 per cent of the carbon dioxide in the same timeframe.

"In the future, we could potentially use these micromotors as part of a water treatment system, like a water decarbonation plant," said co-author Kevin Kaufmann, an undergraduate researcher in Wang's lab.
The micromotors are essentially six-micrometre-long tubes that help rapidly convert carbon dioxide into calcium carbonate, a solid mineral found in eggshells, the shells of various marine organisms, calcium supplements and cement.

The micromotors have an outer polymer surface that holds the enzyme carbonic anhydrase, which speeds up the reaction between carbon dioxide and water to form bicarbonate.
Calcium chloride, which is added to the water solutions, helps convert bicarbonate to calcium carbonate.
The fast and continuous motion of the micromotors in solution makes the micromotors extremely efficient at removing carbon dioxide from water, said researchers.
The team explained that the micromotors' autonomous movement induces efficient solution mixing, leading to faster carbon dioxide conversion.
To fuel the micromotors in water, researchers added hydrogen peroxide, which reacts with the inner platinum surface of the micromotors to generate a stream of oxygen gas bubbles that propel the micromotors around.

When released in water solutions containing as little as two to four per cent hydrogen peroxide, the micromotors reached speeds of more than 100 micrometres per second.
However, the use of hydrogen peroxide as the micromotor fuel is a drawback because it is an extra additive and requires the use of expensive platinum materials to build the micromotors.
Researchers are now planning to make carbon-capturing micromotors that can be propelled by water.
The study was published in the journal Angewandte Chemie.