  Lubricant-infused surfaces (LIS) are highly efficient in repelling water and
constitute a very promising family of materials for condensation processes
occurring in a broad range of energy applications. However, the performance of
LIS in such processes is limited by the inherent thermal resistance imposed by
the thickness of the lubricant and supporting surface structure, as well as by
the gradual depletion of the lubricant over time. Here we present a remarkable,
ultra-thin (~70 nm) and conductive LIS architecture, obtained by infusing
lubricant into a vertically grown graphene nanoscaffold on copper. The
ultra-thin nature of the scaffold, combined with the high in-plane thermal
conductivity of graphene, drastically minimize earlier limitations, effectively
doubling the heat transfer performance compared to a state-of-the-art CuO LIS
surface. We show that the effect of the thermal resistance to the heat transfer
performance of a LIS surface, although often overlooked, can be so detrimental
that a simple nanostructured CuO surface can outperform a CuO LIS surface,
despite film condensation on the former. The present vertical graphene LIS is
also found to be resistant to lubricant depletion, maintaining stable dropwise
condensation for at least ~7 hours with no significant change of advancing
contact angle and contact angle hysteresis. The lubricant consumed by the
vertical graphene LIS is 52.6% less than the existing state-of-the-art CuO LIS,
making also the fabrication process more economical.
