The high Debye temperature and ultralong phonon mean free paths (MFPs) of graphene phononic crystals (GPnCs) enable wavelike phonon transport to manifest over extended length scales, making them an ideal platform for studying phonon localization. We employ machine-learning molecular dynamics to investigate thermal transport in periodic and aperiodic GPnCs. By combining homogeneous non-equilibrium molecular dynamics and non-equilibrium molecular dynamics, we directly extract the spectrally decomposed phonon MFP applicable to aperiodic structures. Spectral analysis establishes characteristic frequency ( omega(c)approximate to 10 THz) and length ( L-c approximate to 100 nm) scales for localization effects, and the nonlinear deviation in the 1/kappa- 1/L relationship ( kappa: thermal conductivity) indicates the presence of localized phonons. Lattice dynamics reveals that the increased fraction of low-participation-ratio modes and the absence of high-group-velocity modes in aperiodic graphene phononic crystals (ap-GPnC) uncover the microscopic origin of disorder-induced phonon localization. Elastic wave simulations further provide direct wave-field evidence of pronounced spatial localization of low-frequency phonons in ap-GPnC with increasing propagation distance.

Controlling multiphase flow in disordered media is central to diverse practical contexts. Although nanoparticles have been widely utilised to modify surface wettability, factors governing their effects on dynamic displacement patterns remain unclear. Here, we identify the criterion for nanoparticle-induced wettability alteration during displacement by combining interfacial-scale wetting models, pore-scale microfluidic experiments and simulations. Motivated by striking contrasts in static wettability, we find that nanoparticle adsorption on solid surfaces affects displacement interfaces only when spreading of wetting films is pre-established, corresponding to corner-flow conditions. Displacement experiments under varying intrinsic wettability show that wetting-film development and non-aqueous droplet detachment are strengthened exclusively on moderately water-wet surfaces satisfying the corner-flow criterion. Investigations across designed porous structures with varying degrees of structural hierarchy validate the generality of the wettability criterion, while improvement in displacement efficiency diminishes with reduced hierarchy. The structural effect arises from variations in flow heterogeneity, with stronger heterogeneity simultaneously promoting film flow and ganglion mobilisation. The coupled impacts of wettability and structural conditions are summarised in an illustrative phase diagram delineating nanoparticle-tuned multiphase displacement. Our findings offer mechanistic insights into complex fluid flow in porous media and suggest optimised strategies for displacement control via nanoparticle suspensions.

Bi2Te3 and Sb2Te3, as typical layered chalcogenide semiconductors, exhibit excellent thermoelectric performance near room temperature. Engineering phonon transport through nanostructures has become an important strategy for optimizing thermoelectric material performance. This study employs neuroevolution potential combined with molecular dynamics simulations to systematically investigate the interfacial scattering and coherent (wavelike) transport mechanisms of phonons in Bi2Te3/Sb2Te3 superlattices. Based on density functional theory calculations, we constructed a dataset and trained a machine learning potential for Bi2Te3/Sb2Te3 heterostructures. The lattice thermal conductivity of superlattices was calculated using the homogeneous non-equilibrium molecular dynamics method, and the wavelike transport characteristics of phonons were analyzed from a wave mechanics perspective by combining phonon wave equations and transfer matrix methods. The study reveals that Bi2Te3/Sb2Te3 superlattices exhibit minimum lattice thermal conductivity at a period thickness of approximately 5 nm, with thermal conductivity showing non-monotonic variation with period thickness. Spectral thermal conductivity analysis demonstrates that this non-monotonic behavior represents a fundamental transition of phonons from coherent wavelike to incoherent particlelike transport. Phonon wave equation calculations further show that Bragg scattering conditions form phonon bandgaps at specific frequency-angle combinations, leading to selective phonon blockade. With systematic variation of period thickness, the position, number, and width of bandgaps exhibit clear evolutionary patterns. In short-period superlattices with fixed period thickness, increasing the number of interfaces can effectively enhance interference effects, making phonon forbidden bands more distinct and frequency selectivity stronger. This study provides theoretical insights into the microscopic mechanisms of phonon wavelike effects in superlattices and offers guidance for interface engineering and performance optimization of nanostructured thermoelectric materials.

While confinement-induced structural disjoining pressure has been extensively studied, the role of surface charge and ionic strength in regulating nanoparticle self-organization and fluid flow in wedged confinements remains incomplete understood. Here, we employ dissipative particle dynamics to investigate the mesoscale behavior of charged nanoparticles suspended in an aqueous phase confined between wedge-shaped walls. By varying wall and particle surface charges and salt concentration, we examine how electrostatic interactions influence nanoparticle layering and fluid flow behavior. Our results demonstrate that electrostatic repulsion between like-charged walls and nanoparticles governs lateral particle migration and ordering, with stronger repulsion driving nanoparticles toward the wedge tip while suppressing their accumulation near charged boundaries. Increasing salt concentration or decreasing surface charge screens electrostatic interactions and hinders step-like nanoparticle layering. In addition to disjoining pressure gradients from spatially varying particle structure, pressure gradients also arise in particle-free regions, contributing to observed circulatory flow within the wedged confinement. SYNOPSIS Electrostatic interactions and ionic screening govern nanoparticle layering in wedge-shaped confinements, thereby modulating structural-pressure-driven water spreading

Droplet electrophoresis is one of the most commonly used methods for measuring the charge at two-liquid interfaces. However, there is still a lack of analytical solutions that consider the ion concentration polarization mechanism with asymmetric ion distribution under high surface charge. Based on the thin electric double layer assumption, we construct the asymptotic form of the macroscopic model of dielectric droplet electrophoresis and establish the coarse-grained effective interface condition across the diffuse layer regions through the heuristic treatment extending the method of matched asymptotic expansion, revealing the coupling mechanism between ion concentration polarization and permittivity-induced inhomogeneous charging. An analytical solution under the weak-external-field limit is provided, demonstrating a nonmonotonic dependence of electrophoretic mobility on the ζ potential under weak external electric fields. By integrating previous experimental results on droplet electrophoresis, a concise and physically meaningful quantitative model of the charging mechanism for general nonpolar oil is established.

More than half of global primary energy is dissipated as low-grade waste heat, yet thermoelectric conversion remains constrained by the intrinsic coupling between phonon and charge transport. Here, we introduce graded interfacial size distribution as a thermodynamic design variable that breaks translational symmetry in multilayers, enabling anisotropic regulation of phonon-carrier transport. Using bismuth telluride (Bi2Te3)/metal [gold, silver, and platinum (Pt)] multilayers as a model system, we demonstrate that multiscale interface distributions induce broadband phonon suppression through the coexistence of interfacial scattering, coherent interference, and localization. This yields an ultralow cross-plane thermal conductivity of 0.22 watts per meter per kelvin and a high room-temperature ZT of 1.51 in Bi2Te3/Pt films. Concurrently, asymmetric metal-semiconductor interfaces create quasi-two-dimensional accumulation channels that enhance in-plane carrier mobility while preserving energy filtering, delivering a power factor of 176.2 microwatts per centimeter per square kelvin at 300 kelvin. The graded architecture enables high performance in both vertical and flexible planar devices, illustrating a general strategy in which interface distribution, not merely composition, governs anisotropic heat-charge transport. Our findings establish statistical interface engineering as a platform for thermoelectric energy harvesting and solid-state cooling.

Accurately modeling immiscible fluid flow in disordered media remains a significant challenge due to the interference of spurious currents. Using the multiple-relaxation-time (MRT) multicomponent pseudopotential lattice Boltzmann method as an exemplar, we perform a Helmholtz decomposition on the anisotropic residual of discrete interaction forces to elucidate its coupling to viscosity pathways. The solenoidal component dissipates through shear viscosity ( mu), while the irrotational component engages bulk viscosity ( zeta), establishing distinct routes for suppressing spurious currents. Numerical experiments show that employing a 10(th)-order interaction force markedly reduces the solenoidal share of the residual-by three to four orders of magnitude compared to fourth-order schemes-thereby activating bulk-viscosity control via the energy-mode relaxation parameter ( s(e), s(& varepsilon;)). This approach attains spurious capillary numbers as low as 10(-5 )and maintains stability at high viscosity ratios, representing up to two orders of magnitude improvement over MRT color-gradient models. The methodology is validated through Laplace pressure tests, two-component Poiseuille flow, Taylor-Bretherton bubble dynamics, and applications in digitized porous media under challenging wettability conditions and high viscosity ratios. From analysis to implementation, the present framework advances high-fidelity multiphase simulations in complex geometries at high viscosity ratios.

The superlinear scaling relationship between the hydrodynamic dispersion coefficient and the P & eacute;clet number in porous media has been widely acknowledged. Nevertheless, the mechanisms driving this behaviour remain inadequately understood. In this work, we investigate the mechanism responsible for this superlinear scaling using a Lagrangian framework that combines a statistical model, which links the global probability density function of tracer transition time to flow variability in porous media, with a continuous time random walk framework. Our analysis reveals that the intra-pore and inter-pore flow variabilities are the primary sources responsible for the superlinear scaling, with their relative significance characterised by a structure-specific parameter, $\chi$ . Specifically, the inter-pore flow variability dominates when $\chi \gt 1$ , while the intra-pore variability prevails for $0\lt \chi \lt 1$ . The parameter $\chi$ is derived exclusively from the statistical distributions of pore-throat radius, length and orientation angle, which can be readily obtained from structural characterisation techniques such as X-ray computed tomography imaging. These theoretical predictions are validated through extensive numerical simulations on tube networks with substantial structural variation. This study resolves discrepancies in previous studies regarding the mechanisms of superlinear scaling in hydrodynamic dispersion and offers valuable insights into modulate dispersion and mixing in porous media.

Diamond/Cu composites have attracted considerable attention for thermal management applications due to their outstanding thermal conductivity. Recent studies have demonstrated that interconnected diamond network structures can significantly enhance the heat conduction of diamond/Cu composites, while the underlying microscopic heat transfer mechanisms remain to be fully elucidated. This study employed machine learning molecular dynamics simulations to validate and elucidate the heat conduction enhancement mechanisms of interconnected network structures. We developed a machine learning potential for diamond/Cu heterostructures based on the neuroevolution potential model and calculated the lattice thermal conductivity (LTC) of two series of network structures: diamond network/Cu (DN/Cu) and Cu network/diamond (CuN/D). The results demonstrate that DN/Cu exhibits monotonically increasing LTC with diamond content due to continuous heat transfer channels, while CuN/D shows non-monotonic behavior with a minimum LTC at intermediate diamond fractions, originating from the competitive mechanism between contributions from low-frequency Cu phonons (0-8 THz) and high-frequency diamond phonons (10-40 THz) to thermal transport. Through spectral LTC decomposition and wavelike phonon transmission analysis, we elucidated the suppressive effects of multiple heat transfer mechanisms on LTC, including phonon interfacial scattering, coherent interference effects, and total internal reflection in nano-network structures. This work establishes quantitative design thresholds for lattice thermal transport in DN/Cu, revealing a critical diamond volume fraction of similar to 30% above which DN/Cu consistently outperforms CuN/D, and an unexpected LTC minimum at similar to 50% diamond in CuN/D structures driven by phonon frequency competition. These findings explain why diamond network structures, despite demonstrating significant heat conduction enhancement compared to dispersed particles, still exhibit LTC values substantially lower than pure diamond, thus revealing substantial room for design optimization of network architectures.

Traditional categorization of gas flow regimes in porous media relies phenomenally on Darcy's law, yielding phenomenologically a "pre-Darcy" flow regime and a "post-Darcy" flow regime before and after the linear region, respectively. This study redefines the classification of gas flow regimes by integrating the underlying flow mechanisms, proposing four distinct regimes: the slip regime, the Darcy regime, the inertia regime, and the turbulence regime. Through a scaling analysis of the Forchheimer equation, a dimensionless number, Rd, is introduced as a criterion for the onset of the inertia regime. The classification is validated using an independently established gas seepage experimental platform, which confirms the presence of gas slip effects in the "pre-Darcy" regime. Experimental data from the inertia regime show a linear increase of critical Rd with a rising permeability (Rdcritical proportional to k). The deduced critical Reynolds number, Re, further substantiates that at low permeability, gas slip effects delay the transition to the inertia regime, while at high permeability, increased pore size or decreased tortuosity may hinder the generation of inertial backflow. Furthermore, the Forchheimer equation provides a more accurate description of both the Darcy and inertia regimes compared to the cubic law, with its inertial coefficient determined through appropriate fitting correlations. This study offers valuable insights into gas flow regimes within porous media, and it provides experimental results for further reference.

Microwave plasma chemical vapor deposition (MPCVD) is one of the most promising methods for producing single-crystal diamond (SCD), which is acclaimed as the 'ultimate semiconductor' material. However, high-quality large-size SCD is still lacking. Previous research asserts the dominance of the electric field and ignores the influence of the flow. In the present work, an analysis of the orders of magnitude is conducted on the fluid description of the plasma to obtain simplified governing equations based on the typical working parameters of the MPCVD. Our theoretical derivation concludes that the spatial distribution of the neutral radical is determined not only by the density gradient but also by the viscous interaction with the neutral gas flow. For verification, the set of governing equations, encompassing Maxwell's equations, electron and neutral radical number density equations, and laminar Navier-Stokes equations, is numerically solved. The simulation results reveal that the non-uniformity of the spatial distribution of the neutral radical increases with the difference of the inlet velocity, corroborating our theoretical analyses. This finding provides a novel regulatory approach for producing high-quality large-size SCD and can possibly be extended to other CVD processes for controlling product quality.

The purification and treatment of water have assumed greater significance in the context of sustainable development. Nevertheless, the conventional theory of concentration polarization inherently imposes constraints on the effective regulation and precise manipulation of ionic transport for electrochemical-based technology. In this work, we propose an extraordinary concentration enrichment mediated by a line charge down to tens of micrometers, allowing continuous extraction in shear flow. The spatiotemporal evolution of the solute concentration is experimentally observed under various applied voltages and flow rates in a microfluidic-based electrochemical device. Through numerical simulations and scaling analysis, we elucidate the trade-offs between key physical parameters to optimize enrichment performance. Furthermore, we demonstrate the cation separation in multicomponent electrolytes and the effective removal of plastic particles and cells in solutions. This portable water purification concept may extend options for drinking water access in disaster response or infrastructure-constrained environments.

Electrokinetic transports in porous media play a crucial role in diverse applications such as geophysical exploration, nuclear waste disposal, water desalination, soil and groundwater remediation, low-salinity waterflooding, and ionic battery operation. This review systematically examines electrokinetic mechanisms in single-phase and multiphase flows in porous media, with a special focus on multiscale and multiphysico-chemical coupling effects. After briefly introducing fundamental theories on microscale electrokinetic transports, we highlight the impact of nanoscale confinement and geometric regulation at first on single-phase electrokinetic flows and ion transport. Next, we discuss the influences of non-uniform ionic concentration and temperature fields on electrokinetic transports, encompassing the impact of surface chemical reactions via charge regulation and reactive transports, and thermodiffusion effects. Furthermore, we provide a concise overview of the current understanding of electrokinetics in multiphase flows, including interfacial charging, wettability alteration, and electrokinetic multiphase dynamics. Finally, we try to outline future research directions, addressing statistics-based theories, multiscale simulations, and advanced experimental designs for electrokinetic transports in porous media.

Microwave Plasma Chemical Vapor Deposition (MPCVD) has emerged as a prominent technique for advanced material synthesis, particularly diamond growth, characterized by inherently complex multiphysical phenomena. At moderate gas pressures (on the magnitude of 0.1 atmospheric pressure), flow effects play a substantial role in MPCVD reactors. However, most previous studies choose to neglect these flow characteristics due to huge computational challenges in multiphysical modeling. Empirical evidence has demonstrated that strategic modifications to fluid inlet configurations may enhance diamond deposition rates by an order of magnitude, yet the underlying mechanisms remain inadequately understood. This study implements a comprehensive multiphysical modeling framework incorporating coupled electromagnetic field, plasma field, flow field, and temperature field. Special attention is given to plasma characterization as a multi-component system requiring rigorous treatment through Maxwell-Stefan diffusion theory. However, previous theoretical analysis reveals a critical limitation in conventional Maxwell-Stefan implementations, which is the inherent assumption of inviscid flow. This contradicts the viscous nature of MPCVD operational environments, as evidenced by our simulation results, demonstrating the necessity of viscous diffusion integration in heavy species transport to achieve experimental consistency. The inclusion of viscous diffusion mechanisms reveals enhanced hydrogen atom concentration near substrate apertures through inlet-induced flow modifications. This concentration enhancement directly correlates with improved deposition rates as per the Goodwin-Harris model. Our findings establish that viscous diffusion constitutes a previously overlooked yet critical transport mechanism in MPCVD reactors, complementing conventional mass diffusion and convective transport. This revelation provides new fundamental insights into diamond deposition mechanisms and proposes a novel process optimization paradigm through transport manipulation.

The electrification effects and electrokinetic flow phenomena at immiscible liquid-liquid interfaces have been a subject of scientific inquiry for over a century. Unlike solid-liquid interfaces, liquid-liquid interfaces exhibit not only multiphysical and cross-scale characteristics but also diffuse soft properties, including finite thickness, fluidity, ion adsorbability, and permeability, which introduces diverse interfacial charging mechanisms and conductive dielectric properties, imparting unique characteristics to electrokinetic multiphase flow systems. Electrokinetic multiphase hydrodynamics (EKmHD), grounded in electrochemistry and colloid and interface science, has experienced renewed interest in recent years. This is particularly evident in systems such as the interface between two immiscible electrolyte solutions (ITIES) in electrochemistry, self-propelling droplets in physicochemical hydrodynamics, and digital microfluidics in electromechanics. The multiphase diffuse soft nature of charged liquid-liquid interfaces introduces novel physical scales and theoretical dimensions, positioning EKmHD as a potential foundation for a new interdisciplinary field rather than merely a cross-disciplinary area. This review highlights the need for an integrated research approach that combines interfacial charging mechanisms with electrokinetic flows, alongside a cross-scale modeling framework for interfacial multiphysical transport. It systematically organizes the characteristics of liquid-liquid interfaces from the perspectives of charging mechanisms and electrokinetic behaviors, with particular emphasis on spontaneous partition- and adsorption-induced charging at the interface, and the strong coupling between multiphase diffuse soft interface flow and ion transport. Furthermore, the paper comprehensively summarizes the transport mechanisms of electrokinetic multiphase flows concerning interfacial ion transport and fluid flow, while refining the corresponding dominant dimensionless parameters. Additionally, it systematically consolidates current understanding of typical electrokinetic multiphase flow scenarios, with special focus on potential future research directions. These include the electrokinetic double-sided coupling effects in ITIES systems, solidification and nonlinear effects in droplet/bubble electrophoresis, the validity of the leaky dielectric model, electrokinetic instabilities of jets and ion-selective soft interfaces, and the active and passive control of two-phase electrokinetic wetting dynamics and displacement.

The electrokinetic and unstable behaviour near strongly polarised surfaces cannot be well captured by the canonical asymptotic theory for induced-charge electro-osmosis, and the intrinsic mechanism remains unclear. Using direct numerical simulations and scaling analysis, this paper reveals that, near the strongly polarised surfaces, the strong electric double layer charging induces a strong local electric field, which drives the cations in the electrical double layer to extend to a finite region and form an extended space-charge (ESC) layer. The ESC triggers flow instability near strongly polarised surfaces, causing a transition of the velocity scaling exponent in the electric field dependence from a 2 to a 4/3 power law. The findings and mechanisms pave the way for designs of energy and biomedical systems.

This work presents a lattice Boltzmann (LB) model for immiscible multiphase flow with phase change. By integrating the pseudopotential model with the color-gradient model, the current model is capable of capturing phase change spontaneously during the immiscible multiphase flows for the first time, with corrected interaction forces at interfaces. The proposed model is comprehensively verified via multiple benchmark cases and applied to investigate the phase change effects on immiscible multiphase flow and displacement in porous media. Our simulation results reveal mechanisms from the gas blockage effects at different capillary numbers and the compressibility effect during immiscible multiphase displacement with phase change in porous media. The pronounced disparity between models that incorporate phase change or not underscores the critical importance of considering phase transitions in immiscible multiphase flow systems.

The pressure oscillation method is a technique for measuring the permeability of evolving porous media. This study presents the analytical solution of the pressure oscillation process considering the slip boundary based on the capillary model and perturbation expansion. The correspondence between the Klinkenberg relation and the Knudsen number is clarified, which provides a theoretical basis for applying the Klinkenberg correction to the pressure oscillation method. The data treatment method using the transient term is proposed, along with its applicable range. Experiments of the pressure oscillation method and pulse decay method are carried out to validate the method. The results show that the transient solution is consistent with the periodic solution, and the unification of the quasi-steady-state and unsteady-state methods under pressure oscillation conditions is achieved. In terms of measurement duration, the pressure oscillation method reduces the measurement time by at least four times compared to the classical pulse decay method. Based on the solution of permeability and porosity, the parameter effects on the experimental data are analyzed, and the dimensionless phase diagram of the amplitude ratio is given to provide a reference for practical engineering applications.

Plasma, with temperature peaking around 3000 degrees C, plays a significant role in Microwave Plasma Chemical Vapor Deposition (MPCVD) for diamond production, while the radiative heat transfer process has not been extensively studied. In this work, we apply the Spherical Harmonics method, specifically the P1 approximation, to solve the Radiative Transfer Equation within the MPCVD simulation framework. This approach is integrated with the Maxwell's equations, the electron number density equation, the plasma temperature equation, and the solid temperature equation to obtain the temperature distribution of both plasma and diamond in a 3D cylindrical chamber. Our results show that the diamond temperature reaches a maximum at the center and decreases towards the edge, which aligns quantitatively with measurements from an infrared pyrometer. This accurate prediction of plasma and diamond temperature provides a powerful tool for optimizing MPCVD equipment and enhancing the production of large-size, high-quality diamonds or other products.