Given that scientists are already looking to sea sponges as an inspiration for body armor, perhaps we shouldn’t be surprised that foam is also being considered ... not just any foam, though. Unlike regular foam, specially-designed nanofoams could someday not only be used in body armor, but also to protect buildings from explosions.

Led by professor of structural engineering Yu Qiao, a team at the University of California, San Diego has been creating the foams by mixing pairs of substances together at a molecular level, then removing one of those materials via acid etching or combustion. As a result, the spaces formerly occupied by the targeted material end up as tiny empty pores within the remaining material.

The size of those pores is crucial, however. It was observed that when regular foams are subjected to a sudden, intense impact, the energy is absorbed in one localized area – this can lead to structural failure. When the foam’s pores are small enough (but not too small), that energy is harmlessly dispersed over a wider area.

Prof. Qiao's nanofoam-testing gas gun

The structure of the nanofoams is composed of 50 to 80 percent pores, which have ranged in size from 10 nanometers to 10 microns each. Those different grades of nanofoam are tested in a lab-based gas gun, that subjects them to increasingly strong impacts. They’re subsequently examined for damage, using a scanning electron microscope.

While the research is still ongoing, nanofoams with a pore size within the tens of nanometers have so far shown the best ability to absorb impacts and blasts.

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