Streaming potential and electroviscous effects in soft nanochannels: towards designing more efficient nanofluidic electrochemomechanical energy converters

Abstract

In this paper we provide analytical solutions for the streaming potential and electroviscous effects in soft nanochannels. The analysis is based on the solution of the linearized Poisson-Boltzmann equation, valid for small electrostatic potentials. We identify the important dimensionless parameters that dictate these two effects. Results are provided for a large range of electric double layer (EDL) thickness values, spanning from the case of very thin to very large overlapped EDL thicknesses. We compare the results with those of a rigid nanochannel, having zeta potential equal to the electrostatic potential at the solid-polyelectrolyte interface of the soft nanochannels. For the soft nanochannel, the streaming potential varies very weakly with the EDL thickness and can be substantially larger than that corresponding to the rigid nanochannel. The electroviscous effects for the soft nanochannel, unlike the rigid nanochannel, virtually always exhibit a monotonic decrease with the EDL thickness, and for certain parameter ranges can be several times larger than that for a rigid nanochannel. Most importantly, for the soft nanochannels the electrochemomechanical energy conversion, associated with the generation of streaming potential, is found to be highly efficient, with the efficiency being several times higher than that of a rigid nanochannel.

Ion transport and selectivity in biomimetic nanopores with pH-tunable zwitterionic polyelectrolyte brushes

“…5a, b (σ m = 0.1 chains per nm 2 ) and 5c,d (σ m = 0.5 chains per nm 2 ) reveals that the larger the grafting density of PE chains on the membrane wall, the more significant the ICP phenomenon. These results clearly indicate that the assumption of homogeneously fixed charge density of PE layer [28][29][30]32,33,[51][52][53] is inappropriate and might result in an incorrect estimation for the ion transport in such soft nanofluidics with a surface modification of PE brushes. In Fig.…”

Electrostatic potential distribution of a soft spherical particle with a charged core and pH-dependent charge density

“…Here is the EDL thickness, PEL is an equivalent double layer thickness within the PEL (see [32] for a discussion on the significance of PEL and K ) and 2en ∞ is the bulk electrolyte charge density. Eq.…”

“…The first is the charge characteristic of the rigid core. Quite surprisingly, in most of the analyses on electrostatics and electrokinetics of soft charged particles, this rigid core has been considered as uncharged and without a finite dielectric constant, represented by a zero potential gradient boundary condition at the interface between the PEL and the rigid core [2,4,7,31,32]. Such a condition is appropriate if the rigid core is a perfectly conducting material such as a metal.…”

Effect of core charge density on the electrophoresis of a soft particle coated with polyelectrolyte layer

“…The charge density of the polyelectrolyte is taken to be constant [11,12,26]. The polyelectrolyte layer can have a constant charge density in several situations, e.g., when pK b pOH ∞ , i.e., the base-like dissociation produce positively charged polyelectrolyte and release OH − ion as counterion or pK a pH ∞ , i.e., the acid-like dissociation produce negatively charged polyelectrolyte and release H + ion as counterion [27], here K a and K b are ionization constants and pOH ∞ , pH ∞ are the bulk pOH and pH values, respectively.…”