Osmotically Driven Nonmonotonic Dynamics of Nuclear-to-Cellular Volume Ratio

A biophysical issue how the nuclear size dynamically scales with the cellular size remains mysterious. We develop a theoretical framework in which the interactions between polydisperse biomolecules and the mechanical elasticity of the cell are precisely integrated to investigate dynamics of the nuclear-to-cellular volume ratio (N/C ratio). We surprisingly find that the N/C ratio varies nonmonotonically with time, instead of maintaining a constant as normally known, during a period of osmotic shocks. Combining simulations and analytical argument, we identify that this nontrivial dynamics can be phenomenally predicted by the formed segregation configurations in the concentrations of the biomolecules, and essentially, all these observed phenomena can be further rationalized by the resultant of the excluded volume interactions between the polydisperse biomolecules and the spatial constraint from the nuclear envelope upon the macromolecule diffusions. Our results agree well with the published experiments for the cellular and nuclear size controls of the protoplasts.Comment: Submitted to Journa

A Novel Equivalent Agglomeration Model for Heat Conduction Enhancement in Nanofluids

We propose a multilevel equivalent agglomeration (MEA) model in which all particles in an irregular cluster are treated as a new particle with equivalent volume, the liquid molecules wrapping the cluster and in the gaps are considered to assemble on the surface of new particle as mixing nanolayer (MNL), the thermal conductivity in MNL is assumed to satisfy exponential distribution. Theoretical predictions for thermal conductivity enhancement are highly in agreement with the classical experimental data. Also, we first try to employ TEM information quantitatively to offer probable reference agglomeration ratio (not necessary a very precise value) to just test rational estimations range by present model. The comparison results indicate the satisfactory priori agglomeration ratio estimations range from renovated model

Fractal aggregation kinetics contributions to thermal conductivity of nano-suspensions in unsteady thermal convection

Nano-suspensions (NS) exhibit unusual thermophysical behaviors once interparticle aggregations and the shear flows are imposed, which occur ubiquitously in applications but remain poorly understood, because existing theories have not paid these attentions but focused mainly on stationary NS. Here we report the critical role of time-dependent fractal aggregation in the unsteady thermal convection of NS systematically. Interestingly, a time ratio λ = t(p)/t(m) (t(p) is the aggregate characteristic time, t(m) the mean convection time) is introduced to characterize the slow and fast aggregations, which affect distinctly the thermal convection process over time. The increase of fractal dimension reduces both momentum and thermal boundary layers, meanwhile extends the time duration for the full development of thermal convection. We find a nonlinear growth relation of the momentum layer, but a linear one of the thermal layer, with the increase of primary volume fraction of nanoparticles for different fractal dimensions. We present two global fractal scaling formulas to describe these two distinct relations properly, respectively. Our theories and methods in this study provide new evidence for understanding shear-flow and anomalous heat transfer of NS associated non-equilibrium aggregation processes by fractal laws, moreover, applications in modern micro-flow technology in nanodevices

Self-growing nano-liquid-crystal film from dynamic swollen hydrogel substrates

A hydrogel which spontaneously swells in an aqueous polymer solution was observed to produce a new hydrogel film coated on its swollen surface. Here, inspired by this phenomenon, we theoretically formulate the dynamics of isotropic-to-nematic (I-N) phase transition caused by swelling a hydrogel substrate (HS) in a dilute nanoplatelet suspension, and quantitatively characterize a self-growing nano-liquid-crystal (NLC) film coated on the swollen HS surface. We show that as the HS gets softer, the resulting NLC film can form earlier and achieve greater thickness (up to hundreds of micrometers). Our results and the existing experiments confirm that the growth dynamics of the NLC film or hydrogel film is exclusively regulated by the swelling behaviors of the HS instead of suspension configurations, e.g., I-N phase transition or sol-gel transition, suggesting a universal signature for the solutes ranging from molecules to colloids. However, both the maximum thickness of the NLC film and the corresponding characteristic time rely highly on the inherent elasticity of the HS and nanoplatelet aspect ratio. We demonstrate that the swelling quasiequilibrium state rather than the equilibrium state of the HS is more qualified to formulate a condition which is practically significant in preestimating the moment when the maximum thickness of the NLC film appears. Our theoretical framework serves as a robust paradigm to extensively rationalize (bio)film coatings which self-integrate with diverse nanostructural configurations via swelling-induced phase transition

Dynamic behaviors of sedimenting colloidal gel materials: hydrodynamic interactions

It is a highly nonlinear poromechanics phenomenon that colloidal gel materials that are exposed to a gravitational stress greater than their yield stress undergo elastic compression.</p

Osmotic release of drugs via deswelling dynamics of microgels: modeling of collaborative flow and diffusions

Hydrogel colloids, i.e., micro- or nano-gels, are increasingly engineered as promising vehicles for polymer-based drug delivery systems. We report a continuum theory of deswelling dynamics of nanocomposite microgels driven by external osmotic shocks and further develop a universal framework, by introducing a buffer release domain, to quantitatively characterize a continuous drug release from deswollen microgels towards surroundings. The drug release is shown to proceed accompanied by an active outward solvent flow created by the elastically shrunken gel network. We further find that a declining trend in the cumulative release plateau with the drug size is followed by an apparent increase again as the drug size increases above a threshold. These findings highlight a nontrivial behavior that the resulting hydrodynamic interactions coexist collaboratively with the passive diffusions to facilitate a desired drug release. We show that deswelling of a stiffer microgel (the mesh size reduces slowly) or loading the larger drugs could bring a control-like release type, otherwise a burst-like release type emerges. Compared with a uniform microgel, the fuzzy-corona-like microgel enables a more productive drug release before reaching deswelling equilibrium. Our model not only predicts well the existing experiments, but also serves as a versatile paradigm to help understand the reciprocal roles of the solvent flow, the gel dynamics, and the diffusions in the polymer-based drug delivery systems

Osmotic release of drugs via deswelling dynamics of microgels: modeling of collaborative flow and diffusions

Hydrogel colloids, i.e., micro- or nano-gels, are increasingly engineered as promising vehicles for polymer-based drug delivery systems. We report a continuum theory of deswelling dynamics of nanocomposite microgels driven by external osmotic shocks and further develop a universal framework, by introducing a buffer release domain, to quantitatively characterize a continuous drug release from deswollen microgels towards surroundings. The drug release is shown to proceed accompanied by an active outward solvent flow created by the elastically shrunken gel network. We further find that a declining trend in the cumulative release plateau with the drug size is followed by an apparent increase again as the drug size increases above a threshold. These findings highlight a nontrivial behavior that the resulting hydrodynamic interactions coexist collaboratively with the passive diffusions to facilitate a desired drug release. We show that deswelling of a stiffer microgel (the mesh size reduces slowly) or loading the larger drugs could bring a control-like release type, otherwise a burst-like release type emerges. Compared with a uniform microgel, the fuzzy-corona-like microgel enables a more productive drug release before reaching deswelling equilibrium. Our model not only predicts well the existing experiments, but also serves as a versatile paradigm to help understand the reciprocal roles of the solvent flow, the gel dynamics, and the diffusions in the polymer-based drug delivery systems

Stratification in the dynamics of sedimenting colloidal platelet–sphere mixtures

The dynamics of sedimentation in a binary mixture of colloidal platelets–spheres is studied theoretically using the minimal energy model.</p

Growth dynamics of nanoplatelet liquid crystals by directionally drying colloidal suspensions in a confined channel

Unidirectional solvent evaporation has been increasingly concerned as a versatile microfluidic agent in manipulating the self-assembly dynamics of shape anisotropic colloids by precisely governing a confined nanofluid flow in a microcell. Here we develop a theoretical framework upon unidirectional drying-induced growth of nematic liquid crystals (LC) in nanoplatelet suspension confined to a Hele-Shaw (H-S) channel. The nematic order-dependent permeability assembled in modified Darcy's law and the interactions between nanoplatelets for nematic LC are both explicitly incorporated in a confined nanofluid flow. The growth dynamics of nematic LC that is highly correlated with drying rate (drying Peclet number), nanoplatelet aspect ratio, and geometric confinement have been rationalized by our numerical measurements. Unlike the spherical colloids, the nematic LC grows nonlinearly over time indicating a time-dependent instantaneous growth velocity. The final length of LC, when subjected to an enhanced drying rate, is seen to be compressed toward the drying end, but its time-averaged growth velocity increases significantly. Besides, the LC formed by the thicker nanoplatelets gets the shorter final length, while whether its average growth velocity is affected by nanoplatelet types depends on the drying rate. Importantly, we confirm a noticeable promotion in the growth of LC as the enhanced geometric confinement is imposed. A state diagram we produce suggests a universal signature of enhancement in solvent drying flux with enhanced confinement. However, our results highlight the favorable water retention in nanoplatelet nematic LC with compacted layered architecture prevailing over the spherical colloids deposits with the porous percolation architecture