With Airbus"s giant A380 airliner about to take to the skies, you might think planes could not get much bigger and you would be right. For a given design, it turns (1)_____, there comes a point where the wings become too heavy to generate (2)_____ lift to carry their own weight. (3)_____ a new way of designing and making materials could (4)_____ that problem. Two engineers (5)_____ University College London have devised an innovative way to customise and control the (6)_____ of a material throughout its three dimension al structure. In the (7)_____ of a wing, this would make possible a material that is dense, strong and load-bearing at one end, close to the fuselage, (8)_____ the extremities could be made less dense, lighter and more (9)_____. It is like making bespoke materials, (10)_____ you can customise the physical properties of every cubic millimetre of a structure. The new technique combines existing technologies in a(n) (11)_____ way. It starts by using finite-element-analysis software, of the type commonly used by engineers, (12)_____ a virtual prototype of the object. The software models the stresses and strains that the object will need to (13)_____ throughout its structure. Using this information it is then (14)_____ to calculate the precise forces acting on millions of smaller subsections of the structure. (15)_____ of these subsections is (16)_____ treated as a separate object with its own set of forces acting on it—and each subsection (17)_____ for a different microstructure to absorb those local forces. Designing so many microstructures manually (18)_____ be a huge task, so the researchers apply an optimisation program, called a genetic algorithm, (19)_____. This uses a process of randomisation and trial-and-error to search the vast number of possible microstructures to find the most (20)_____ design for each subsection.