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69Functional surfaceAdvances in ultra-precision machining make it possible to create microand nano-structured surfaces, which can alter the surface properties of a material and even imbue it with new functions. For example, ultra-precision machining can polish a scalpel blade to such a smooth and precise finish that it minimises surgically-induced tissue trauma, swelling, and scarring, thereby speeding up wound closure and healing. Similarly, artificial joints must be machined within the tightest tolerances to ensure a perfect fit. With nanometric surface roughness, friction between components in artificial joints is minimised, extending their longevity. Micro- and nano-structures also exist in nature, providing a myriad of useful functionalities that aid the survival of various flora and fauna. Imitating these biological surfaces, Prof. Cheung%u2019s team has developed various functional surfaces. For example, inspired by the water-repelling property of lotus leaves, the team has created micro-patterns on glass surfaces to prevent water and dirt from sticking. This makes them ideal for external mirrors and other hard-to-reach surfaces that benefit from self-cleaning properties. Additionally, butterfly wings appear colourful because nanostructures on them cause light waves to diffract and interfere. Similarly, Prof. Cheung%u2019s team has achieved colourful finishes on metals by mimicking such nanostructures.SMALL IS POWERFUL