  Molecular Communications (MC) is a bio-inspired paradigm for transmitting
information using chemical signals, which can enable novel applications at the
junction of biotechnology, nanotechnology, and information and communication
technologies. However, designing efficient and reliable MC systems poses
significant challenges due to the complex nature of the physical channel and
the limitations of the micro/nanoscale transmitter and receiver devices. In
this paper, we propose a practical microfluidic transmitter architecture for MC
based on hydrodynamic gating, a widely utilized technique for generating
chemical waveforms in microfluidic channels with high spatiotemporal
resolution. We develop an approximate analytical model that can capture the
fundamental characteristics of the generated molecular pulses, such as pulse
width, pulse amplitude, and pulse delay, as functions of main system
parameters, such as flow velocity and gating duration. We validate the accuracy
of our model by comparing it with finite element simulations using COMSOL
Multiphysics under various system settings. Our analytical model can enable the
optimization of microfluidic transmitters for MC applications in terms of
minimizing intersymbol interference and maximizing data transmission rate.
