Toward High Capacity Molecular Communications Using Sequential Vortex Rings

Molecular signal coherence in fluid dynamic channels is severely hindered by mass, momentum, and turbulent diffusive forces. The combination of such forces causes long molecular tails, which results in severe inter-symbol-interference (ISI) and limits the achievable symbol rate. Here, we propose to modulate information symbols into stable vortex ring structures to minimize ISI. Each vortex ring can propagate approximately 100× the diameter of the transmission nozzle without losing its compact shape. First, we show that the ISI from sequential transmissions is minimal and reduces rapidly with distance after transmission. This is the opposite effect to conventional molecular puffs undergoing advection-diffusion, whereby ISI increases with distance. Second, we show that by maintaining a coherent signal structure, the signal-to-inference ratio is 211× higher over conventional puffs. Also, we demonstrate the vortex ring using a proof-of-concept prototype. The results point toward a promising pathway for higher capacity channels.