While most research has focused on patterns on the outer surfaces of materials, scientists at MIT have begun to explore the effects of patterned surfaces deep within materials. The MIT Department of Materials Science and Engineering (DMSE) team’s results show that control of internal patterns can lead to significant improvements in the performance of the resulting materials.

Michael Demkowicz, associate professor in the DMSE, explains that research has already aimed to create layered composites with desired strength and flexibility or resistance to vibrations, temperature changes or radiation. However, actually controlling the surfaces where two materials meet within a composite is a tricky process. “People don’t think of them as surfaces,” says Demkowicz. “If they do, they think of it as a uniform surface, but as it turns out, most interfaces are not uniform.”

Understanding and directing these non-uniform interfaces is essential to control the properties of these materials, Demkowicz notes. He and his team have taken classical equations used to describe average properties of surfaces and adapted them to instead describe variations in these surfaces “location by location.”

The ability to simulate and control how defects or variations are distributed at these interfaces could be useful for a range of applications. The patterning can cause helium bubbles in materials used on the interior walls of fusion power reactors to form channels instead of weakening the material. The same principle can apply to controlling how phonons move through a crystalline structure, which could be important for the production of thermoelectric devices and could help improve the efficiency of lithium-ion batteries and fuel cells.

“The mechanical properties of materials also depend on the internal structure, so you can make them strong or weak by [controlling these interfaces],” Demkowicz says.