  With the continuous advancement of nanotechnology, nanodevices have become
crucial components in computing, sensing and energy conversion applications.
However, the structures of nanodevices typically possess sub-wavelength
dimensions and separations, which pose significant challenges for understanding
energy transport phenomena in nanodevices. Here, based on a judiciously
designed thermal nanodevice, we report the first measurement of near-field
energy transport between two coplanar sub-wavelength structures over
temperature bias up to ~190 K. Our experimental results demonstrate a
remarkable 20-fold enhancement in heat transfer beyond blackbody radiation. In
contrast with the well-established near-field interactions between two
semi-infinite bodies, the sub-wavelength confinements in nanodevices lead to
the increased polariton scattering and the reduction of supporting modes and
therefore a lower heat flow at a given separation. Our work unveils exciting
opportunities for the rational design of nanodevices, particularly for on-chip
near-field energy transport, with important implications for the development of
efficient nanodevices for energy harvesting and thermal management.
