Effect of hydrophobic core on the electrophoresis of a diffuse soft particle

Electrophoresis of a diffuse soft particle with a charged hydrophobic core is considered under the weak field and low charge density assumptions. The hydrophobic surface of the core is coated with a diffuse polyelectrolyte layer (PEL) in which a gradual transition of the polymer segment distribution from the impenetrable core to the surrounding electrolyte medium is considered. A mathematical model is adopted to analyse the impact of the core hydrophobicity on the diffuse soft particle electrophoresis. The mobility based on the present model for the limiting cases such as bare colloids with hydrophobic core and soft particles with no-slip rigid cores are in good agreement with the existing results. The presence of PEL charges produces the impact of the core hydrophobicity on the soft particle mobility different from the corresponding bare colloid with hydrophobic surface in an electrolyte medium. The impact of the core hydrophobicity is subtle when the hydrodynamic screening length of the PEL is low. Reversal in mobility can be achieved by tuning the core hydrophobicity for an oppositely charged core and PEL.

Capillary osmosis in a charged nanopore connecting two large reservoirs

Experimental evidence revealed that the performance of nanopore-based biosensing devices can be improved by applying a salt concentration gradient. To provide a theoretical explanation for this observation and explore the mechanisms involved, we model the capillary osmosis (or diffusioosmosis) in a charged solid-state nanopore connecting two large reservoirs. The effects of nanopore geometry and the reservoir salt concentrations are examined. We show that the capillary osmotic flow is from the high salt concentration reservoir to the low salt concentration one, and its magnitude has a maximum as the reservoir salt concentrations vary. In general, the shorter the nanopore and/or the smaller its radius, the faster the osmotic flow. This flow enhances the current recognition, and the ion concentration polarization across nanopore openings raises the entity capture rate, thereby being capable of improving the performance of electrophoresis-based biosensors. The results gathered provide necessary information for designing nanopore-based biosensor devices.