Chemical Technology March 2015

NANOTECHNOLOGY

environment. Laser-etched surfaces don’t. The opportunities are endless and governments around the world are sponsoring research at an ever-increasing rate. P2i is a spin-out of research funded by the UK government. As usual, the early work will be slow and expensive, but the op- portunities for better solar panels, more fuel efficient vehicles, and self-cleaning clothes are endless. That isn’t to say that therewon’t be silliness too. ‘Ultra-Ever Dry’ is a xylene and acetone-based coating which is painted onto surfaces (do so in a well-ventilated room, it’s toxic). Numerous internetmemes exist wherepeopledemonstrate the effect of coating toilets, keyboards, or ice-trays in the paint. Nissan recently coated one of their economy cars in the stuff and took it for a spin to demonstrate a car that may never need cleaning (subject to periodic recoatings). The material isn’t transparent so don’t expect to use it on the windscreen. I like the idea of easy-cleaning cookware, cutlery and crockery. Or shirts that never need cleaning. But there are other, more serious, considerations. As the global temperature rises and the oceans acidify, the expectation is that algae and bacteria will thrive. That will cause worse biofouling for pipelines and shipping. What’s interesting is that scientists don’t fully understand the process by which superhydrophobic surfaces act. But that doesn’t really matter to us. As long as it works, and as long as we can prove that they work safely, we will all benefit. z

alumina (or hard-anodized aluminium) cookware is widely used. These, though, use much higher pore sizes but dem- onstrate the much greater resilience to abrasion and regular use of this material. Try and imagine the impact of suchmaterials in healthcare, where –while single-use surgical tools can be discarded – life- support equipment is repeatedly sterilised but still contains nooks and crannies where bacteria hide. Not all surfaces can be treated with the chemical immer- sion required for anodisation. Professor Chunlei Guo and his team at the University of Rochester have been working with femtosecond laser bursts to etch hierarchical structures onto surfaces. Guo, andhis colleagueAnatoliy Vorobyev, arebuilding on earlier work that used laser-patterning to turnmetals black. They are creating surfaces that areboth superhydrophobic and optically highly-absorbant. Guo says that “the structures created by our laser on the metals are intrinsically part of thematerial surface.” Theywon’t rub off and they are resistant to abrasion. This is not yet suitable for industrial use as it takes an hour to pattern a 25,4 mm 2 metal sample, however, the idea that femtosecond lasers can be used to etch such patternsmeans they can be easily applied to surfaces after fabrication. They could even be used on non-metallic materials. These non-coating approaches are important for another reason: they don’t require toxic chemical coatings. By their nature, as they wear off, coatings leach toxins into the

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Chemical Technology • March 2015