Chemical Technology March 2015

Chemical Technology • March 2015

NANOTECHNOLOGY

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

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

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.