This approach predicted the design of alloys with roughly half the stiffness of current implants — promising to reduce pain for the millions of patients who receive hip transplants each year. It also opens opportunities for theory-guided design of future biomedical products.

OPENING UP SOFT MATERIALS

Soft materials form organized systems at scales beyond those of molecules, within products ranging from plastics in yoghurt cups, to foods such as mayonnaise and to biological molecules including DNA. They differ from ‘hard matter’ (such as steel or gold) by lower energy density: the bonds are 100–1,000 times weaker than those in metallic crystals^5,6.

Thermal effects influence the organization of soft materials. Hence, models cannot use quantum calculations alone; thermodynamic calculations must also be included.

Modelling soft materials starts with an atomic description, and then derives a broader model for simulations over a longer period. This approach can rapidly switch between levels of resolution, and can be run in reverse to study melting behaviour. Various soft-material problems, such as polymer stability or liquid-crystal switching, can be solved this way.

FUTURE AND PERSPECTIVES

Imagine moving from a study of individual alloy atoms to simulating the material in an automotive test crash or using the results of biomolecular simulations to describe the workings of blood vessels. Multi-scale modelling could make such visions reality, but challenges remain. Unified theories of matter, which can bridge computational scales in a physically consistent manner, must be developed. Experimental observations are needed to verify model predictions at all levels. Successful multi-scale modelling must be capable of handling the complexity of real-life situations to avoid generating incorrect predictions.

A multiscale model, based on coupled ab initio and continuum simulations, has helped to unravel the molecular and mesoscopic structure and properties of chitin-based natural polymers. These materials form the exoskeleton of arthropods, including insects, spiders and decapods. The model can be used to design advanced synthetic polymers. The project was realized cooperatively by the Max Planck Society, the Bulgarian Academy of Sciences and the Massachusetts Institute of Technology (Nikolov. S. et al. Adv. Mater.22, 519–526, 2010 ).