  The performance of communication systems is fundamentally limited by the loss
of energy through propagation and circuit inefficiencies. In this article, we
show that it is possible to achieve ultra low energy communications at the
nano-scale, if diffusive molecules are used for carrying data. Whilst the
energy of electromagnetic waves will inevitably decay as a function of
transmission distance and time, the energy in individual molecules does not.
Over time, the receiver has an opportunity to recover some, if not all of the
molecular energy transmitted. The article demonstrates the potential of
ultra-low energy simultaneous molecular information and energy transfer (SMIET)
through the design of two different nano-relay systems, and the discusses how
molecular communications can benefit more from crowd energy harvesting than
traditional wave-based systems.
