Engineers at the University of California-San Diego are developing a small-sized solution to the big problem of carbon dioxide build-up in the world’s oceans. They propose sending out micrometer-length tubes that spin around in the water, converting the CO2 into a harmless byproduct. The clever part: The same process that propels the micro-tubes in the marine environment also helps scrub the ocean clean.
The machines, which are no wider than a human hair, are coated with an enzyme that helps convert CO2 into calcium carbonate, a solid material found in various animal shells. In experiments, the devices converted up to 90% of the available CO2—for now, only in controlled lab conditions.
“This system is a promising approach to rapid and enhanced CO2 sequestration platforms for addressing growing concerns over the buildup of greenhouse gas,” says a paper discussing the results.
About one-third of carbon dioxide pollution ends up in oceans, rivers, and lakes, either because it is taken in by plants or absorbed into the water itself. Some of this becomes carbonic acid, which causes ocean acidification, a process that threatens coral, mollusks, plankton, and other important creatures.
The work is led by Joseph Wang, a pioneer in the field of autonomous nano-motors. In other research, Wang has showed how tiny machines could be used for drug delivery and other medical purposes inside the body.
The latest machines aren’t quite self-powered yet. Wang’s team added hydrogen peroxide to the water, inducing the release of oxygen bubbles that spin the motors and push them along. But the long-term plan is for the devices to be “fuel-free” and act independently.
“The main challenge to scaling this work up is the development of ‘fuel-free’ micromotors which are capable of using the natural environment to drive their propulsion,” says Kevin Kaufmann, an undergraduate researcher in Wang’s lab, in an email.
“Just recently we fabricated a magnesium-based micro-motor capable of moving in salt water without the addition of external fuels. A micro-motor such as these would be very useful for the removal of carbon dioxide from ocean water.”