  In this paper, the impulse response for a 3-D microfluidic channel in the
presence of Poiseuille flow is obtained by solving the diffusion equation in
radial coordinates. Using the radial distribution, the axial distribution is
then approximated accordingly. Since Poiseuille flow velocity changes with
radial position, molecules have different axial properties for different radial
distributions. We, therefore, present a piecewise function for the axial
distribution of the molecules in the channel considering this radial
distribution. Finally, we lay evidence for our theoretical derivations for
impulse response of the microfluidic channel and radial distribution of
molecules through comparing them using various Monte Carlo simulations.
