Many of the processes we need for modern life create pollution. Making batteries and electronic devices or mining the earth, for example, produce hazardous heavy metals such as lead, arsenic, mercury, cadmium, and chromium, all of which can get into soil and water.
But some tube-shaped microbots made of graphene are getting ready to save the day. Made by a team of researchers lead by Diana Vilela of the Max-Planck Institute for Intelligent Systems in Stuttgart, Germany, the microbots have already demonstrated that they can remove 95 percent of the lead from polluted water in one hour.
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The bots - each one smaller than the width of a human hair - can be reused many times, reducing the cost of remediation.
"This work is a step toward the development of smart remediation system where we can target and remove traces of pollutant without producing an additional contamination," coauthor Samuel Sánchez told Phys.org.
The tiny robots work because they're made in layers. The outer layer is graphene, which grabs onto any lead ions it comes into contact with.
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The middle layer is made of nickel, a ferromagnetic material that allows a person to remotely control where the microbot swims by using an external magnetic field. The core layer is made of platinum, which helps propel the device.
The propulsion occurs when hydrogen peroxide is added to the water, which causes the platinum to decompose and produce microbubbles. Those bubbles shoot out the back of the microbot and push it forward. The video demonstrating the propulsion shows the microbots zooming around the water like little rocket ships.
You can watch the video here.
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Once the microbots have collected the lead, they can release those tiny bits, which can be collected and reused.
"The use of self-powered nanomachines that can capture heavy metals from contaminated solutions, transport them to desired places and even release them for 'closing the loop' - that is a proof-of-concept towards industrial applications," said Sánchez.
At the moment, the microbots only work for lead but the team plans to extend the use of microbots to other contaminants and work on a way to mass-produce the robots at a low cost.