  Conical channels filled with an aqueous electrolyte have been proposed as
promising candidates for iontronic neuromorphic circuits. This is facilitated
by a novel analytical model for the internal channel dynamics [Kamsma et al.,
arXiv:2301.06158, 2023], the relative ease of fabrication of conical channels,
and the wide range of achievable memory retention times by varying the channel
lengths. In this work, we demonstrate that the analytical model for conical
channels can be generalized to channels with an inhomogeneous surface charge
distribution, which we predict to exhibit significantly stronger current
rectification and more pronounced memristive properties in the case of bipolar
channels, i.e. channels where the tip and base carry a surface charge of
opposite sign. Additionally, we show that the use of bipolar conical channels
in a previously proposed iontronic circuit features hallmarks of neuronal
communication, such as all-or-none action potentials and spike train
generation. Bipolar channels allow, however, for circuit parameters in the
range of their biological analogues, and exhibit membrane potentials that match
well with biological mammalian action potentials, further supporting its
potential for bio-compatibility.
