  In this second part of our survey on experimental research in Synthetic
Molecular Communication (SMC), we review works on long-range SMC systems, i.e.,
systems with communication ranges of more than a few millimeters. Despite the
importance of experimental research for the evolution of SMC towards a mature
communication paradigm that will eventually support revolutionary applications
beyond the reach of today's prevalent communication paradigms, the existing
body of literature is still comparatively sparse. Long-range SMC systems have
been proposed in the literature for information transmission in two types of
fluid media, liquid and air. While both types of SMC systems, liquid-based and
air-based systems, rely on encoding and transmitting information using
molecules, they differ substantially in terms of the physical system designs
and in the type of applications they are intended for. In this paper, we
present a systematic characterization of experimental works on long-range SMC
that reveals the major drivers of these works in terms of the respective target
applications. Furthermore, the physical designs for long-range SMC proposed in
the literature are comprehensively reviewed. In this way, our survey will
contribute to making experimental research in this field more accessible and
identifying novel directions for future research.
