Repeated Microphase Separation and Heating-free Distillation-like Behavior of Miscible Binary Liquid Mixtures Using Nanoconfined Grafted Polymer Layers.

Nanoconfinement is known to drive phase separation (often denoted as microphase separation) of two highly miscible liquids by subjecting the two liquids to disparate influences. Here, we propose a paradigm shift to this problem: we introduce the idea of "repeatability" in nanoconfinement-driven microphase separation. A drop consisting of two highly miscible liquids (A and B) is made to pass through a nanochannel grafted with a collapsed layer of polymer that is philic to A but phobic to B.

Direct visualization of nanoparticle morphology in thermally sintered nanoparticle ink traces and the relationship among nanoparticle morphology, incomplete polymer removal, and trace conductivity.

A key challenge encountered by printed electronics is that the conductivity of sintered metal nanoparticle (NP) traces is always several times smaller than the bulk metal conductivity. Identifying the relative roles of the voids and the residual polymers on NP surfaces in sintered NP traces, in determining such reduced conductivity, is essential. In this paper, we employ a combination of electron microscopy imaging and detailed simulations to quantify the relative roles of such voids and residual polymers in the conductivity of sintered traces of a commercial (Novacentrix) silver nanoparticle-based ink.

Extensive Stable Physical Contacts between a Nanoparticle and a Highly Repulsive Polymeric Layer.

Interaction between nanoparticles (NPs) and a layer of grafted and solvated polymer molecules has been widely explored for a variety of applications ranging from fabrication of nanocomposites and sensors to developing nanocoating for virus deactivation. In all of these applications, the solvated polymer molecules are necessarily philic to the NPs, and consequently, driven by the favorable NP-polymer interactions, there is the formation of numerous stable direct (i.e.

Coalescence of Microscopic Polymeric Drops: Effect of Drop Impact Velocities.

In this paper, we employ the direct numerical simulation (DNS) method for probing three-dimensional, axisymmetric coalescence of microscale, power-law-obeying, and shear-thinning polymeric liquid drops of identical sizes impacting a solid, solvophilic substrate with a finite velocity. Unlike the cases of drop coalescence of Newtonian liquid drops, coalescence of non-Newtonian polymeric drops has received very little attention. Our study bridges this gap by providing (1) the time-dependent, three-dimensional (3D) velocity field and 3D velocity vectors inside two coalescing polymeric drops in the presence of a solid substrate and (2) the effect of the drop impact velocity (on the solid substrate), quantified by the Weber number (), on the coalescence dynamics.

Theoretical study on the massively augmented electro-osmotic water transport in polyelectrolyte brush functionalized nanoslits.

We demonstrate that functionalizing nanoslits with pH-responsive polyelectrolyte brushes can lead to extremely fast electro-osmotic (EOS) water transport, where the maximum centreline velocity and the volume flow rate can be an order of magnitude larger than these quantities in identically charged brush-free nanochannels for a wide range of system parameters. Such an enhancement is most remarkable given that the brushes have been known to retard the transport by imparting additional drag on the fluid flow. We argue that this enhancement stems from the localization of the charge density of the brush-induced electric double layer (and, hence, the EOS body force) away from the nanochannel wall (or the location of the wall-induced drag force).

Strong stretching theory for pH-responsive polyelectrolyte brushes in large salt concentrations.

In this paper, we develop a theory for describing the thermodynamics, configuration, and electrostatics of strongly-stretched, pH-responsive polyelectrolyte (PE) brushes in the presence of large salt concentrations. The aim of the paper, therefore, is to study the properties of a PE brush in a salt concentration regime (namely, large concentrations of several molars) that has been hitherto unexplored theoretically in the context of PE brushes but can be routinely encountered in molecular scale simulations of the problem. The brushes are modelled using our recently developed augmented Strong Stretching Theory (SST), while the effect of the presence of the large salt concentration is accounted for by including the contributions of three different types of non-Poisson-Boltzmann (non-PB) effects to the free energy description of the PE brush induced electric double layer (EDL).

Coating for preventing nonspecific adhesion mediated biofouling in salty systems: Effect of the electrostatic and van der waals interactions.

Development of anti-biofouling coating has attracted immense attention for reducing the massively detrimental effects of biofouling in systems ranging from ship hulls and surgical instruments to catheters, implants, and stents. In this paper, we propose a model to quantify the role of electrostatic and van der Waals (vdW) forces in dictating the efficacy of dielectric coating for preventing the nonspecific adhesion mediated biofouling in salty systems. The model considers a generic charged lipid-bilayer encapsulated vesicle-like structure representing the bio-organism.

Ionic current in nanochannels grafted with pH-responsive polyelectrolyte brushes modeled using augmented strong stretching theory.

In this paper, we provide a theory to quantify the ionic current ( ) in nanochannels grafted with pH-responsive polyelectrolyte (PE) brushes. We consider the PE brushes to be modeled by our recently proposed augmented strong stretching theory (SST) model that improves the existing SST models by incorporating the effects of excluded volume interactions and an extended mass action law. Use of such augmented SST for this problem implies that this is the first study on computing in PE brush-grafted nanochannels accounting for the appropriate coupled configuration-electrostatic description of the PE brushes.

Clusterlike instabilities in bubble-plume-driven flows.

Continuous release of gas bubbles in large numbers from a localized source in a liquid column, popularly known as "bubble plumes", is very relevant in nature and industries. The bubble plumes morphologically consist of a long continuous stem supporting a dispersed head. Through our direct numerical simulations using two-way coupled Euler-Lagrangian framework, we show that a bubble plume rising in a quiescent liquid column develops clusterlike instabilities for the Grashof numbers, Gr>145.