Modeling of electrically controlled molecular diffusion in a nanofluidic channel

Abstract

The objective of this work is to understand and quantitatively model the diffusive transport in electrically gated nanofluidic channels suitable for applications in drug delivery. Specifically, this work analyzed gated molecular diffusion through simulation in nanochannels between two chambers with asymmetric concentrations under a number of different control variables including surface charge, channel structure, drug molecule charge number, and background ionic concentration. When the dimension of the fluidic channel is comparable to the thickness of electrical double layer, the potential generated by gating inside of the channel becomes significant, which allows control of charged molecular diffusion inside of the nanochannel through electrostatic repulsion and attraction. In this work, the diffusion of molecules through a nanochannel is simulated in planar and cylindrical nanochannels when applying a gate voltage in two different surface charging scenarios. The gated nanochannel structures were modeled in the finite element software (COMSOL Multiphysics). The simulation results indicate that a small applied voltage can alter the diffusion rate by many orders of magnitude under certain conditions. The cylindrical nanochannel showed the best control of diffusion of charged molecules due to the exclusion-enrichment effect inside the nanochannel.