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Conductance Interplay in Ion Concentration Polarization across 1D Nanochannels: Microchannel Surface Shunt and Nanochannel Conductance
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posted on 2019-12-13, 22:13 authored by Zisun Ahmed, Yang Bu, Levent YobasIon concentration polarization has received much interest
in the
past decade for lab-on-a-chip applications, primarily preconcentration
of biomolecules and water desalination. Studying the basic phenomenon
in microfluidics has also generated new knowledge, which could be
pivotal in the design of novel devices. Many studies, however, have
focused on designs featuring nanoslits/slots or surface-patterned
ion-selective membranes whereas the characteristics of 1D nanochannels
are still lacking. Here, we report on ion concentration polarization
across highly ordered 1D nanochannels in isolation as well as in array
formation. Intriguingly, the nanochannels in isolation exhibit a linear
current–voltage characteristic at low salt concentrations despite
the confirmed presence of ion-depletion zone, which is associated
with the diffusion-limited transport and the consequent nonlinearity
in the classical sense. The characteristic in array formation breaks
away from the linearity with a peculiar dip in current for a critical
salt concentration in the dilute limit. We describe these findings
based on the interplay between the nanochannel conductance and the
conductance of the neighboring microchannel walls (the so-called surface
shunt). Also, the nanochannel transport is identified with the mobility
of protons more closely than that of salt cations. We attribute fast
transport to phosphorus-doped silicate glass, the nanochannel material
known to have very fine pores likely to be populated with protons
as a result of moisture and carbon dioxide adsorption from the air.
The nanochannels possess a tubular profile 70 nm in nominal diameter
and fabricated through thermal reflow of doped glass on silicon without
using advanced lithography.
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isolation exhibitConductance Interplay1 D Nanochannelsnovel devicesarray formation breaksdiffusion-limited transportarray formationlab-on-a-chip applications1 D nanochannelsIon Concentration Polarizationsurface-patterned ion-selective membranesprofile 70 nmMicrochannel Surface Shuntsurface shuntphosphorus-doped silicate glassNanochannel Conductance Ion concentration polarizationsalt concentrationnanochannel transportwater desalinationnanochannel conductanceMany studiessalt concentrationscarbon dioxide adsorptionnanochannel materialion concentration polarizationsalt cationsion-depletion zone
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