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Fiction writers have long postulated the emergence of intelligent molecules a billionth of a metre in diameter that determine their own shape in order to best serve their structural purpose. Two engineers at University College London have evolved mass production of materials into customisation to make this reality.

Working at the millimetre - rather than the nanometre - scale, architect and research engineer Sean Hanna and roboticist and computer scientist Siavash Haroun Mahdavi have developed evolutionary algorithms that create self-supporting forms that adapt themselves to maximise strength while minimising weight.

They have combined this with cutting-edge rapid prototyping technology (stereolithography) to generate a 3D scale model from a digital image using a low-powered laser to 'cure' photosensitive polymers. They also use laser sintering, which melts thin layers of a polymer-and-sand powder with a CO 2 laser.

Structural optimisation is nothing new to architecture, which deals with structures containing hundreds or thousands of members. For example, the British Museum has about 5,000 elements to it.

'You consider each element linearly, calculating how it would behave given certain loading conditions and determine what the stresses will be, ' says Hanna. 'Using an analysis loop you can change it and gradually improve it. But if you want to make something that goes into a larger scale, with millions of members, as big as you want it to be, the computation time to optimise it goes up exponentially.'

Accordingly, Hanna and Mahdavi have built a simulation imbuing molecules with a modicum of intelligence. Explains Hanna: 'It lets each molecule look at the overall loading demands or stress at that particular point and then adjusts its form.' Their work closely approximates the way nature produces organic building blocks. 'Draw the analogy with bone, or wood, ' says Hanna. 'Wood is very strong because of the arrangement of fibres. The tree distributes the fibres in a way that's optimal to carry the forces it has to support. The ends of a bone are denser than its interior as that's the most efficient way of carrying a load.

'By evolution, cells have the 'intelligence' to reorient themselves or change their shape, size or structure depending on where they sit. Our model uses genetic algorithms to do the same.' Currently, though, it's only an algorithm and once the material is built using rapid prototyping, the molecule can't actually change.

The pair are no strangers to practical applications.

Mahdavi is using similar algorithms to build robots that adapt themselves if broken, while Hanna developed, with Foster and Partners, a light-controlled roof composed of louvres that twist into different orientations to follow the path of the sun.

Their modelling technique also has practical implications.

Most immediately they see their method being applied to small mass-customisable products, such as medical implants and high-end sports equipment, both moulded to an individual body. They have already used their model to produce customised orthotics (shaped arch supports for trainers) that cost about £20 to manufacture.

But until demand - not for rapid prototyping but for rapid manufacturing, increases, the high cost of rapid prototyping limits this sort of application for the present time. 'We've made some one- or two-centimetre blocks using stereolithography that cost £1 or £2 each, ' says Hanna. Algorithms are cheap, but the costs for the model add up.

But, says Hanna, by using their adaptive algorithm, which learns how to optimise itself, 'the calculation for millions of members becomes more feasible. You can use this sort of technique to give you an optimal solution very rapidly.' The pair hope eventually to deploy this technique to build structures where every unit is unique. 'You'd give each element limited intelligence so that it can go off and build itself;

it's autonomous, like a living cell, ' says Hanna. 'It could cover a metre or even a whole city, or you could then shrink it down and manipulate the behaviour and structural capacity of individual building elements.' Blue sky? This is real-life nanotech. 'Small units with a little technology that reconfigure themselves to create any shape you like, a lump of material that reshapes itself at the level of tree or bone cells, ' says Hanna. He also hopes to develop materials with controllable dynamic properties to create, for instance, one with a zero Poisson's ratio (so if compressed in one direction it does not expand in another). Watch this (compressed) space.

www. sean. hanna. net/microstructure. htm www. cs. ucl. ac. uk/staff/S.HarounMahdavi/ COMING SOON TO SCREENS NEAR YOU Philips Research has developed the Polymer Vision flexible screen;

a 'rollable display'. It may soon be used for screens for palmtops, GPS devices or portable screens, rolling down to almost nothing.

The screen consists of Thin Film Transistors (TFTs), using plastic as a substrate. Plastic must be processed at low temperatures in order not to melt, but making silicon-based TFTs requires very high temperatures. The TFT layers are 25 micrometres thick.

A fl exible display similar to Philips' electronic ink goes on top.

The possibilities seem limitless. Might we see entire media suites of wall-sized flexible displays? Might you carry interactive blueprints with you and unwrap them as you would a poster?

A4 sizes should be feasible soon, but bigger screens are some way off. Also coming soon are techniques to use the display as a sound baffle and giving the display a touchscreen capability.

Over the longer term, Philips Research's HomeLab has numerous 'Ambient Intelligence' projects that aim to integrate technology into our lives. One concept, Aurora, is an interactive light surface for the home that lets you draw and erase with light over an entire wall. Another, Photonic Textiles, turns fabrics into intelligent displays.

Polymer Vision: www. polymervision. com Photonic Textiles: www. research. philips. com/initiatives/photext/ Ambient Intelligence: www. research. philips. com/technologies/syst_softw HomeLab www. research. philips. com/technologies/misc/homelab/ Liz Bailey is a writer on technology

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