posted on 2021-03-30, 16:36authored byHyekyung Lee, Seoyun Sohn, Shima Alizadeh, Soonhyun Kwon, Tae Jin Kim, Seung-min Park, Hyongsok Tom Soh, Ali Mani, Sung Jae Kim
Overlimiting
current (OLC) through electrolytes interfaced with
perm-selective membranes has been extensively researched for understanding
fundamental nano-electrokinetics and developing efficient engineering
applications. This work studies how a network of microchannels in
a nonuniform array, which mimics a natural pore configuration, can
contribute to OLC. Here, micro/nanofluidic devices are fabricated
with arrays of parallel microchannels with nonuniform size distributions,
which are faced with a perm-selective membrane. All cases maintain
the same surface and bulk conduction to allow probing of the sensitivity
only by the nonuniformity. Rigorous experimental and theoretical investigation
demonstrates that overlimiting conductance has a maximum value depending
on the nonuniformity. Furthermore, in operando visualization
reveals that the nonuniform arrays induce flow loops across the microchannel
network enhancing advective transport. This recirculating flow eliminates
local salt accumulations so that it can effectively suppress undesirable
salt crystallization. Therefore, these results can significantly advance
not only the fundamental understanding of the driving mechanism of
the OLC but also the design rule of electrochemical membrane applications.