Heat travels through materials via collective atomic vibrations called phonons. Scientists largely understand how phonons travel through a single material, but this understanding becomes a bit fuzzy when phonons reach an interface between two materials. As depicted in the above cartoon, scientists believe they know what phonons are “thinking” about when they reach an interface between two materials—vibrational frequency, acoustic velocity, interfacial bond stiffness, etc.—but it is still unclear as to which of these considerations is most important in determining whether or not a phonon will “hop the gap” between two materials. Scientifically understanding which of these factors is most important to the rate of interfacial heat transfer remains a critical challenge to the thermal sciences community—one that must be solved if we hope to build material systems with rationally designed thermal properties.

Mark discusses this challenge on NC State’s Science Blog here.

A Nature Materials News and Views article about Interfacial Thermal Sciences co-written by Mark and David Cahill is available here.