My research interests center on nanoscale transport and energy conversion phenomena, and their applications in energy storage and conversion, thermal management, and desalination. We have worked on understanding heat conduction in nanostructures such as ballistic and coherent heat conduction in superlattices via both modeling and experimental studies, extracting phonon mean free path distributions in solids by exploiting ballistic phonon transport processes, and first principles simulation of phonon and electron thermal and thermoelectric transport. Together with my collaborators, we exploited the unique nanoscale heat conduction physics to improve thermoelectric materials and explore their applications in solar thermal and waste heat recovery. We are also working on strategies to engineer nanostructures to achieve high thermal conductivities, and have demonstrated that polymers can be more thermally conductive than most metals. In addition to heat conduction, we also work on thermal radiation. We developed a method to measure radiation heat transfer between two surfaces down to 10s nanometer separations and experimental demonstration that radiative heat transfer at such small spacings can exceed the prediction of the Planck blackbody radiation law by three orders of magnitude. We work on photon trapping in solar photovoltaic cells, solar thermal and solar steam generation. We are interested in applying these new understandings to advance technologies such as energy storage, thermoelectric cooling and power generation, solar thermal and solar photovoltaics, desalination, and thermal interface materials. I have interests in entrepreneurship and have been involved in several startup companies.
I am also serving as the Head of the MIT Department of Mechanical Engineering, and the director of the MIT Pappalardo Micro/Nano Engineering Laboratory. I chaired the advisory board of the ASME Nanotechnology Institute from 2005-2008. I also direct “Solid-State Solar-Thermal Energy Conversion Center (S3TEC)”, an Energy Frontier Research Center funded by the US Department of Energy.