How pollution-munching nanobots could solve a major societal issue

After a long, hot day there’s nothing quite as refreshing as an ice-cold glass of water. Crystal clear out of the tap or filtering pitcher, it’s hard to imagine that the water passing your parched lips could be anything but pure. That, however, couldn’t be further from the truth.

Even after filtering, the water flowing through millions of people’s pipes around the world can still contain imperceptible toxins and pollutants, including arsenic and atrazine, that can make their way into our glasses or into the irrigation systems used to grow our food. In the body, these pollutants can lead to the development of cancers, including breast cancer.

Removing small pollutants like these has been an ongoing challenge for chemical engineers, but a new paper published Tuesday in the journal Nature Communications offers a new approach in the form of reusable magnetic nanobots.

In their paper, the team reported that the nanobots were able to collect a large percentage of pollutants in their samples, including over 70 percent of the pollutants in a matter of hours. The team also found that their bots continued to be effective over 10 cycles of pollution collection. Based on this performance, the authors believe these bots could play an important role in reversing environmental damage from pollutants.

Here’s the background — In the past couple of decades, nanobots have emerged as an essential solution to exploring small or inaccessible spaces — from waterways to inside the human body. Designs have used light or metal catalysts to drive the propulsion of these tiny robots. However, the current designs remain limited, both in their lifespans and their range of ability.

Martin Pumera, a senior author on the paper and professor of chemistry at the University of Chemistry and Technology, Prague, tells Inverse that the team’s new nanobot design fixes many of these limitations: It can be both propelled and recalled using a magnetic field, making the approach efficient and fuel-free.

“As propulsion is not catalytic or light-driven, we are free to operate in fuel-free environments… or in dark environments,” Pumera says.

In addition to the nanobots' magnetism, Pumera says they are also thermoresponsive. This makes it possible for the pick-up and release of pollutants to be controlled by just the temperature of the bot’s environment.

Why it matters — Improving the lifespan and mobility of nanobots will help improve not only their ability to munch on pollutants but could also help improve the design of medical nanobots. As these bots continue to improve and scale, they could keep future generations healthy in some very important ways, including potentially producing cleaner drinking water and delivering targeted therapies in the body.

What they did — Despite the big task at hand for these nanobots, their design is actually fairly straightforward. The bots have two major components:

1. A temperature-sensitive polymer that can either “grab” pollutants or release them based on a change in temperature between 5 degrees Celsius (41 degrees Fahrenheit) and 25 degrees Celsius (77 degrees Fahrenheit)
2. Magnetic iron oxide nanoparticles allow the bots to be manipulated and collected using magnets. Both components are biodegradable, the researchers write, which makes their design more eco-friendly than some that use other fuel types.

In their experiments, when exposed to the warm temperature and an applied field, the nanobots spun and jittered like tops to collect arsenic and atrazine in the sample medium. When the temperature was lowered, the bots released the pollutants and then returned to their starting configurations via an external magnetic field.

What’s next — Despite the success of these trials, these nanobots are not ready to be unleashed on our water systems just yet. Next on the agenda for the team is to work on scaling up the production of these bots, Pumera says, so that it’s possible to create a large number of these tiny robots as affordably as possible.

In the future, it will also be important to test these bots on a number of other pollutants lurking in our waters as well.

Abstract — Nano/micromotor technology is evolving as an effective method for water treatment applications in comparison to existing static mechanisms. The dynamic nature of the nano/micromotor particles enable faster mass transport and a uniform mixing ensuring an improved pollutant degradation and removal. Here we develop thermosensitive magnetic nanorobots (TM nanorobots) consisting of a pluronic tri-block copolymer (PTBC) that functions as hands for pollutant removal. These TM nanorobots are incorporated with iron oxide (Fe₃O₄) nanoparticles as an active material to enable magnetic propulsion. The pickup and disposal of toxic pollutants are monitored by intermicellar agglomeration and separation of PTBC at different temperatures. The as-prepared TM nanorobots show excellent arsenic and atrazine removal efficiency. Furthermore, the adsorbed toxic contaminants on the TM nanorobots can be disposed by a simple cooling process and exhibit good recovery retention after multiple reuse cycles. This combination of temperature sensitive aggregation/separation coupled with magnetic propulsion opens a plethora of opportunities in the applicability of nanorobots in water treatment and targeted pollutant removal approaches.