In collaboration with [C&EN](http://cen.acs.org/index.html).

Chemist [Jas Pal Badyal](https://community.dur.ac.uk/jps.badyal/) is committed to solving big problems with very small tools: layers of functional molecules only a few nanometers thick. His ultrathin coatings have entered the marketplace on clothing, footwear, and electronics. They impart water-repellent, antibacterial abilities to around three-quarters of the world's hearing aids and more than 100 million cell phones.

After launching three successful high-tech start-ups, the Durham University professor is now tackling social problems in developing nations. For example, he wants to develop materials that can harvest and purify water, a need for countries in the developing world.

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How do you make your liquid-repellent nanocoatings? {#sec2}
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We essentially control chemical reactions that occur on solid surfaces using plasma discharges, which are clouds of ionized atoms. One way we do it is repeatedly to expose the surface to a very short pulse, usually microseconds, of plasma discharge followed by a longer off time lasting milliseconds. The substrate is in a plasma chamber surrounded by a gaseous precursor---say, a molecule with a double bond. Passing electrical current through the gas creates plasma. The plasma pulses generate free-radical sites on many types of surfaces. In the periods between the pulses, you get a conventional reaction of the surface radical with the precursor---for example, a polymerization because a monomer can attach to the surface sites and polymerize.

It's a very generic approach. Generally, we identify a particular application and think about which chemical group added to a surface would give the performance we are after.

So to repel liquid, typically we go for a fluoromonomer---a fluoroalkene is a good example---and use our method to make a continuous fluoropolymer coating that conforms to the surface.

What advantage do these coatings have over others? {#sec3}
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The main advantage is that they are ultrathin. We can, for example, coat each fiber in cotton fabric with 2--3 nm of coating so the fabric remains completely breathable. The method uses very little energy and does not use solvents. And the amount of material needed is minuscule because we're making nanolayers.

Your work has led to three start-ups. What do these companies do? {#sec4}
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Each of the three start-ups---[Surface Innovations](http://www.surface-innovations.com/), Dow Corning Plasma, and [P2i](https://www.p2i.com/)---uses a different approach to make functional nanocoatings, but they all rely on using plasma discharges. The difference is how they use those discharges. You can pulse the discharge to control the reaction as I described earlier. Another method is to spray droplets of the precursor into a continuous discharge, which increases the deposition rate. And you can also introduce solid precursors in the form of nanoparticles within the droplet, which allows you to use a wider variety of materials.

How are you applying this technology to solve humanitarian problems? {#sec5}
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We've been looking at water in particular. We've made coatings that are very hydrophilic, so we've been targeting water harvesting, which is collecting water from the air. We're looking at plants that survive in arid climates by collecting fog. By building three-dimensional structures that mimic the macro-, micro-, and nanolevel surface structures of these plants' leaves and applying our coating to those structures, we can replicate how they harvest moisture from the air.

We are also applying our nanocoatings---ones made, for example, with cyclodextrins---to cheap substrates like cotton to make fabrics that can purify water. We are now working in refugee camps at the Syria--Turkey border to test the fabrics.

What inspired you to tackle these problems with your technology? {#sec6}
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I thought we could look at challenges facing developing countries and adapt our technology to those. The more I read about it, the more I realized that our coating technology could have quite a large impact.

You just received the Chemical Research Society of India's International Medal at its conference in Raipur. What else takes you to India? {#sec7}
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I was born in the U.K., but my parents and grandparents are from India. I was invited to give a lecture in Delhi a few years back. Since then I've been collaborating with some of the younger faculty at the Indian Institute of Technology Ropar, publishing together and sharing best practices on how to set up protocols, standard operating procedures, a digital archive, and open access to raw data.

I'm also interested in helping with local problems there, like crop burning. In some parts of India, when farmers cut wheat or rice, they set fire to the stalks and the leftover plant material. The smoke blows over to cities like Delhi and causes smog. We're looking at how we can use chemistry to add value to the material that is left behind so it can be used instead of burned. One of the things we've been considering is converting it to charcoal and then adding surface functionalization to use it for water purification.

My students have gone to India, and some students from India have come over here. My students are much more aware now of the challenges facing developing countries, which motivates them to pursue science to help society.

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*Prachi Patel is a freelance contributor to*[*Chemical & Engineering News*](http://cen.acs.org/index.html)*, the weekly newsmagazine of the American Chemical Society. Center Stage interviews are edited for length and clarity.*
