Chinese chemists have developed a simple method to create colourful and water-repellent surfaces. The technology could be used in a wide variety of decorative applications, they claim. 

Hong-Bo Sun and colleagues at Jilin University, China, used the interference pattern from several lasers to create an array of needles on a surface - similar to that found in a lotus leaf. The needles minimise the contact between the surface and water droplets, and when modified with fluoroalkylsilane, they create a surface with very high water repellence (superhydrophobicity). Su Chen an expert in materials chemistry at Nanjing University of Technology, China, says that 'there are many practical applications of this approach, for instance, soft imprint lithography and pattern transfer.'  

The pattern from several lasers is used to created an array of needles on the surface

The useful properties of this surface aren't limited to its superhydrophobicity as the material is also iridescent - the colour of the surface changes when viewed from different angles. The regular array of needles is crucial to both these properties as 'its colour depends mainly on the periods,' explains Sun. The superhydrophobic nature of the surface also makes it self-cleaning, as dirt particles are picked up and removed by water droplets rolling off the surface. 

Sun claims that this combination of a self-cleaning, iridescent, superhydrophobic surface could be used to make decorative layers on surfaces that normally become dirty over time, such as buildings, cars and even clothes. Timothy Thatt Yang Tan an expert in nanomaterials from Nanyang Technological University, Singapore, agrees 'the simplistic approach outlined in this work brings us a step closer to the realization of biomimetic self-cleaning and structural colour material for both functional and aesthetic applications.' 

Russell Johnson 

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