Just as a journey of 1,000 miles begins with a single step, the deformations and fractures that cause catastrophic failure in materials begin with a few molecules torn out of place. This in turn leads to a cascade of damage at increasingly larger scales, culminating in total mechanical breakdown. That process is of urgent interest to researchers studying how to build high-strength composite materials for critical components ranging from airplane wings and wind-turbine blades to artificial knee joints.

Now scientists from the National Institute of Standards and Technology (NIST) and their colleagues have devised a way to observe the effects of strain at the single-molecule level by measuring how an applied force changes the three-dimensional alignment of molecules in the material.

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