Biomimetic coating for electric transmission

Materials World magazine
1 Dec 2006

Researchers at Georgia Institute of Technology (GIT), USA, are developing a biomimetic coating, based on the lotus leaf, that may help conserve energy in a problem that has plagued electric transmission systems for decades.

Funded by the National Electric Energy Testing Research and Application Center at GIT and the National Science Foundation, USA, the project is led by Professor Ching Wong.

‘Energy is one of the most important issues in the new century,’ says Wong. ‘To conserve energy in high voltage transmission lines, such as by preventing leaking currents, dry band arcing and flashover, caused by contamination of the insulator surface, a self-cleaning surface is proposed.’

This is where the lotus leaf has provided inspiration. Despite growing in the muddy waterways of Asia, the leaves and flowers of the lotus plant remain clean. Its water repelling characteristics result from its microscale surface structures and nanoscale waxy protrusions.

‘When rain hits the leaves of the lotus plant, it simply beads up,’ explains Wong. ‘Because of the combination of nanoscale and microscale structures, water droplets can only make contact with about three per cent of the surface.’

Such properties have already prompted the development of ‘self-cleaning’ coatings on glass, hard disks drives and magnetic tape.

‘However, to mimic the lotus coating effect for outdoor applications, degradation over time - especially UV irradiation degradation – poses the most severe problem,’ Wong adds.

The team at GIT have addressed this issue by using UV stable materials – such as a combination of silicone, fluorocarbons and inorganics such as titanium dioxide and silicon dioxide.

The prototype has demonstrated impressive weathering resistance and the surface has higher contact angle measurements and a lower hysteresis loss than the natural analogue. This indicates that the novel coatings are hydrophobic and could have a better self-recovery mechanism than the lotus leaf. However, additional research is needed to understand the effect of surface structure on superhydrophobicity.

While previous work on self-cleaning surfaces for transmission lines has been theoretical with a focus on the preparation methods, Wong claims that his approach has more potential.

‘We showed ways to bring this coating from lab to real applications.’

In addition to its self-cleaning nature, the biomimetic surface has other benefits such as anti-corrosivity, biocompatibility, antistiction and transparency. These properties could be exploited in a number of applications, such as implantable medical devices, micro-electromechanical systems (MEM) and space suits.

'The lotus plant is yet another example of how researchers can learn surprising lessons from what nature has provided,' says Wong.