  The purpose of this work is to create a model of a nanofluidic transistor
which is able to mimic the effects of pH on nanopore conductance. The pH of the
electrolyte is an experimentally controllable parameter through which the
charge pattern can be tuned: pH affects the ratio of the
protonated/deprotonated forms of the functional groups anchored to the surface
of the nanopore (for example, amino and carboxyl groups). Thus, the behavior of
the bipolar transistor changes as it becomes ion selective in acidic/basic
environments. We relate the surface charge to pH and perform particle
simulations (Local Equilibrium Monte Carlo) with different nanopore geometries
(cylindrical and double conical). The simulations form a self consistent system
with the Nernst-Planck equation with which we compute ionic flux. We discuss
the mechanism behind pH-control of ionic current: formation of depletion zones.
