Ion transport and current rectification in a charged conical nanopore filled with viscoelastic fluids

Abstract

The ionic current rectification (ICR) is a non-linear current-voltage response upon switching the polarity of the potential across nanopore which is similar to the I–V response in the semiconductor diode. The ICR phenomenon finds several potential applications in micro/nano-fluidics (e.g., Bio-sensors and Lab-on-Chip applications). From a biological application viewpoint, most biological fluids (e.g., blood, saliva, mucus, etc.) exhibit non-Newtonian visco-elastic behavior; their rheological properties differ from Newtonian fluids. Therefore, the resultant flow-field should show an additional dependence on the rheological material properties of viscoelastic fluids such as fluid relaxation time $$(\lambda )$$ ( λ ) and fluid extensibility $$(\varepsilon )$$ ( ε ) . Despite numerous potential applications, the comprehensive investigation of the viscoelastic behavior of the fluid on ionic concentration profile and ICR phenomena has not been attempted. ICR phenomena occur when the length scale and Debye layer thickness approaches to the same order. Therefore, this work extensively investigates the effect of visco-elasticity on the flow and ionic mass transfer along with the ICR phenomena in a single conical nanopore. The Poisson–Nernst–Planck (P–N–P) model coupled with momentum equations have been solved for a wide range of conditions such as, Deborah number, $$1\le De \le 100$$ 1 ≤ D e ≤ 100 , Debye length parameter, $$1\le \kappa R_t \le 50$$ 1 ≤ κ R t ≤ 50 , fluid extensibility parameter, $$0.05\le \varepsilon \le 0.25$$ 0.05 ≤ ε ≤ 0.25 , applied electric potential, $$-40\le V \le 40$$ - 40 ≤ V ≤ 40 , and surface charge density $$\sigma = -10$$ σ = - 10 and $$-50$$ - 50 . Limited results for Newtonian fluid ($$De = 0$$ D e = 0 , and $$\varepsilon = 0$$ ε = 0 ) have also been shown in order to demonstrate the effectiveness of non-Newtonian fluid behaviour over the Newtonian fluid behaviour. Four distinct novel characteristics of electro-osmotic flow (EOF) in a conical nanopore have been investigated here, namely (1) detailed structure of flow field and velocity distribution in viscoelastic fluids (2) influence of Deborah number and fluid extensibility parameter on ionic current rectification (ICR) (3) volumetric flow rate calculation as a function of Deborah number and fluid extensibility parameter (4) effect of viscoelastic parameters on concentration distribution of ions in the nanopore. At high applied voltage, both the extensibility parameter and Deborah number facilitate the ICR phenomena. In addition, the ICR phenomena are observed to be more pronounced at low values of $$\kappa R_t$$ κ R t than the high values of $$\kappa R_t$$ κ R t . This effect is due to the overlapping of the electric double layer at low values of $$\kappa R_t$$ κ R t .

In‐situ PLL‐g‐PEG Functionalized Nanopore for Enhancing Protein Characterization

“…Conversely, by increasing the λ D , resistive forces arise at the nanopore‘s tip, dampening the ionic current [65,66] . Compared to long nanopores, short nanopores have considerable advantages, including a higher ionic permeation coefficients and increased biosensor sensitivity [67] .…”

“…Conversely, by increasing the λ D , resistive forces arise at the nanopore's tip, dampening the ionic current. [65,66] Compared to long nanopores, short nanopores have considerable advantages, including a higher ionic permeation coefficients and increased biosensor sensitivity. [67] In order to improve energy conversion, desalination, and biosensor sensitivity, it is essential to achieve significant ICR in nanopores.…”

Ion current rectification properties of non-Newtonian fluids in conical nanochannels

“…Non-Newtonian fluids also have a significant impact on the ICR phenomenon in nanochannels. Trivedi et al 50 used the simplified PTT (sPTT) model to study the effect of non-Newtonian fluids on flow and ion transport in individual conical nanopores. The results showed that the ICR phenomenon was promoted by both the ductility parameter and the Deborah number at high bias voltages and was more pronounced at low kR t values.…”

Modulating selective ionic enrichment and depletion zones in straight nanochannels via the interplay of surface charge modulation and electric field mediated fluid‐thickening

“…Berzina and Anand [34] described an electrokinetic means of producing dialysate from the excess fluid extant in the peripheral blood of patients undergoing therapy by using ICP. Trivedi and Nirmalkar [35] investigated ICP in charged cylindrical nanopore using viscoelastic fluids. Liu et al [36] investigated the interplay between ICP and process performance in the pervaporation operation for volatile organic component removal in a membrane channel with rectangular cross section.…”