Tiny submarines that are 10 times smaller than the width of a human hair could be used to clean up oil spills, researchers have suggested.
The self-propelled microsubmarines are able to gather oil droplets and take them to collection facilities.
The team from the University of California San Diego's nano-engineering department said their tests showed "great promise".

Similar technology is able to deliver drugs through a person's bloodstream.
The research, which appeared in journal ACS Nano, suggested that the microsubmarines were capable of "a facile, rapid and highly efficient collection" of motor and olive oil droplets.
The tiny motors are propelled by bubbles created from internal oxidation of hydrogen peroxide.
This means they require small amounts of fuel and can move very quickly.
Self-propelled
Although currently just a lab-based proof of concept, it gives hope to improved methods of dealing with future spill disasters - a requirement made more pressing following painstaking attempts to deal with spills in the Gulf of Mexico.
"This is the first example of using nanomachines for environmental remediation," lead researcher Joseph Wang told the BBC.
"We had earlier developed self-propelled nanomachines.
"Here, we coated them with a superhydrophobic layer that offers strong 'on-the-fly' interaction with oil droplets."
Superhydrophobic materials are designed to be extremely hard to make wet, while also able to absorb oil effectively.
Last year, researchers at Penn State University demonstrated micromachines capable of bringing drugs to certain areas of the body via the bloodstream.
The research drew humorous parallels with 1960s science fiction film Fantastic Voyage in which a submarine and its crew are shrunk in order to get into the bloodstream of a key informant.

Techno Nigeria