A swarm of tiny, self-propelling robots can clean heavy metals from contaminated water, a new study has revealed.
Industries such as mining and technology manufacturing can pollute water with metals such as lead, arsenic and mercury. This can have consequences for the ecosystem, including flora and fauna, as well as wider public health ramifications.
Now, researchers in Germany, Spain and Singapore have developed microbots to begin undoing this process – with each bot thinner than a human hair.
The machines are multi-functional: they propel themselves through water, extracting particles of lead as they go. According to the paper, published in Nano Letters, the bots effectively remove 95% of lead from contaminated water in one hour using their multi-tiered approach.
The outer layer of their tube-like structure is made of graphene oxide, which absorbs lead from water. The middle layer, made of nickel, means each robot can be controlled by a magnetic field.
The inner layer is platinum which, when combined with hydrogen peroxide, creates microbubbles and propels the robot forward.
This system has resulted in a series of self-propelling, itty-bitty robots which extract and capture particles of lead, before being sucked out of the water by a magnetic field.
The robots can be treated with acid to remove the lead, and there is an added sustainability bonus: the removed lead can then be recycled, and the robots themselves can be used multiple times once they've been cleared of their cargo.
Although this study focuses on lead, the research, led by Diana Vilela at the Max Planck Institute for Intelligent Systems in Stuttgart, Germany, may have wider applications.
"The use of active systems and graphene nanomaterials can pave the way for new functionalities of self-propelled micronanomotors, from drug delivery, sensing, and energy to new environmental applications," the researchers write.