| Sumario: | The article discusses a technique for making customized "microstructured" materials. Two engineers at University College London, Sia Mahdavi and Sean Hanna, have devised an innovative way to customise and control the properties of a material throughout its three-dimensional structure. The new technique combines existing technologies in a novel way. It starts by using finite-element-analysis software, of the type commonly used by engineers, to create a virtual prototype of the object. The software models the stresses and strains that the object will need to withstand throughout its structure. Using this information it is then possible to calculate the precise forces acting on millions of smaller subsections of the structure. Each one of these subsections is then treated as a separate object with its own set of forces acting on it--and each subsection calls for a different microstructure to absorb those local forces. Designing so many microstructures manually would be a huge task, so the researchers apply an optimisation program, called a genetic algorithm, instead. Armed with these designs, the only way to build such an intricate and complex object is to use "rapid prototyping" technology, which enables three-dimensional objects to be "printed", one layer at a time, using anything from polymers to metals. The new technique makes it possible to provide strength only where it is needed, making the rest of the structure lighter. The result is a porous, honeycomb-like structure that is capable of withstanding the applied forces, but weighs very little due to its parsimonious use of materials. Such precise control over the material's structure makes possible materials with useful but unusual properties.
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