Computer program reveals optimum microstructure

A Princeton chemist has developed a general mathematical system for designing materials that perform two functions at once, even when the desired properties sometimes conflict with each other.

Salvatore Torquato and colleagues used computers to calculate the optimum structure for any material that is a composite of two substances with differing properties. The achievement is the first simple example of a mathematically rigorous method for optimising the design of multifunctional composites, which are an increasingly common kind of material.

The approach could help bring to man-made materials the efficiency of design that characterizes so many biological materials. "Biological materials are inherently multifunctional," said Torquato. "They have evolved over millions of years to cope with a wide range of situations, so they perform a variety of functions well."

A tree, for example, has to support its weight and resist winds while transporting liquids up and down its length, said Torquato, who is a professor in the Princeton Materials Institute as well as the Department of Chemistry. "Until our work, however, there has been no clear and simple example that rigorously demonstrates the effect of competing property demands on composite microstructures."

In addition to its possible applications in materials science, the method may help biologists study natural materials, such as the walls of a cell, to understand why they are built as they are. "Using rigorous optimisation techniques, we are now in a position to test some of the basic tenets of biology," Torquato said. "Are there elements of biology -- perhaps subsystems within an organism or cell -- that are optimised in any sense?"