Pressure responsive gating in nanochannels coated by semiflexible polymer brushes

Abstract

Nanochannels coated with semiflexible polymer brushes behave as pressure-responsive gates.

Liquid and Droplet Transport in Brush-Coated Cylindrical Nanochannels: Brush-Assisted Droplet Formation

“…This regime corresponds to an “open channel”. A similar behavior has also been observed for rather rigid semiflexible brushes in planar slit pores . In this “open-channel” regime, the flow rate increases stronger than linearly with the external driving force, in contrast to the macroscopic Hagen–Poiseuille law.…”

“…A similar behavior has also been observed for rather rigid semiflexible brushes in planar slit pores. 45 In this "openchannel" regime, the flow rate increases stronger than linearly with the external driving force, in contrast to the macroscopic Hagen−Poiseuille law. We attribute this superlinear dependence to an increase of the effective hydrodynamic channel radius due to the emptying of liquid pockets (see Figures 2c,d and 3b).…”

Voltage-Triggered Structural Switching of Polyelectrolyte-Modified Nanochannels

“…The organization of a polyelectrolyte brush within a nanochannel is a complex function of its radius, the length of the polymeric chains, the quality of the solvent, and the pH and salt concentration of the solution. ,− ,,, In order to find the optimal conditions for the nanomechanical gate proposed in Figure , we will first explore the effects of channel radius and chain length in the absence of an applied potential (equilibrium state). This analysis will provide the conditions to form the collapsed-to-the-center state.…”

“…In order to evaluate the effectivity of the proposed nanomechanical gate to control the transport of particles of different sizes, we calculate the average concentration of the particles within the channel, which we denote ⟨ρ k ⟩ where k = center or walls when the polyelectrolyte layer is in the collapsed-to-the-center or in collapsed-to-the-wall state, respectively (we also dropped the subscript i for clarity). The integral in eq runs over the area of the channel, which is equal to A .…”

“…End-grafted layers of polymers or polyelectrolytes with hydrophobic backbones can aggregate in micro-/nanostructures of different morphologies in order to avoid contact with the solvent. , Changes in the effective segment–segment attractive strength, by changing either the quality of the solvent or the average charge per monomer, result in steep transitions between self-assembled nanostructures with different morphologies. When the polymer layer is confined within a nanochannel, there is a particularly interesting morphological transition between structures that are collapsed on the channel’s inner walls (collapsed-to-the-wall states) and structures in which the polymer chains collapse to the axis of the channel, forming a central plug (collapsed-to-the-center state). − The conductance behavior of channels modified by pNIPAM brushes has been associated with the existence of these two collapse configurations. , In another example, Speyer and Pastorino studied the transition between the two collapse states induced by an applied pressure using molecular dynamics simulations . Based on these previous works, the transition between the collapsed-to-the-center and collapsed-to-the-wall states emerges as an interesting strategy to create nanochannels with sharp stimuli-induced structural transitions.…”