Silvia Franco, Leonardo Severini, Elena Buratti, Letizia Tavagnacco, Simona Sennato, Mauro Missori, Barbara Ruzicka, Claudia Mazzuca, Emanuela Zaccarelli, Roberta Angelini
Gellan gum has gained significant attention due to its versatility in multiple applications in the form of hydrogels and microgels. A thorough understanding of the rheological behaviour of these systems is crucial both for fundamental research and to optimize the manufacturing needs. To this aim, here we extensively characterize the rheological behaviour of gellan based hydrogels and microgels recently used for efficient paper cleaning for restoration interventions. In particular, we study their viscoelastic properties, also during hydrogel and microgel formation, assessing the role of temperature, gellan concentration, and, importantly, the presence of different cations, which plays a crucial role in the gelation process. We find the interesting result that, in the conditions where they are efficient for cleaning, gellan hydrogels exhibit a double yielding behavior. In addition, we provide a detailed description of gellan microgels preparation, ensuring high control and reproducibility of the samples. Altogether our study sheds light on the mechanical stability, network structure, and overall functionality of the gellan-based gels, providing valuable insights into optimizing conditions for desired applications in paper cleaning.
{"title":"Gellan-Based Hydrogels and Microgels for culturage heritage: a rheological perspective","authors":"Silvia Franco, Leonardo Severini, Elena Buratti, Letizia Tavagnacco, Simona Sennato, Mauro Missori, Barbara Ruzicka, Claudia Mazzuca, Emanuela Zaccarelli, Roberta Angelini","doi":"arxiv-2408.17247","DOIUrl":"https://doi.org/arxiv-2408.17247","url":null,"abstract":"Gellan gum has gained significant attention due to its versatility in\u0000multiple applications in the form of hydrogels and microgels. A thorough\u0000understanding of the rheological behaviour of these systems is crucial both for\u0000fundamental research and to optimize the manufacturing needs. To this aim, here\u0000we extensively characterize the rheological behaviour of gellan based hydrogels\u0000and microgels recently used for efficient paper cleaning for restoration\u0000interventions. In particular, we study their viscoelastic properties, also\u0000during hydrogel and microgel formation, assessing the role of temperature,\u0000gellan concentration, and, importantly, the presence of different cations,\u0000which plays a crucial role in the gelation process. We find the interesting\u0000result that, in the conditions where they are efficient for cleaning, gellan\u0000hydrogels exhibit a double yielding behavior. In addition, we provide a\u0000detailed description of gellan microgels preparation, ensuring high control and\u0000reproducibility of the samples. Altogether our study sheds light on the\u0000mechanical stability, network structure, and overall functionality of the\u0000gellan-based gels, providing valuable insights into optimizing conditions for\u0000desired applications in paper cleaning.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"57 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220672","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Nan Xue, Lawrence A. Wilen, Robert W. Style, Eric R. Dufresne
The surface tension of partially wetting droplets deforms soft substrates. These deformations are usually localized to a narrow region near the contact line, forming a so-called `elastocapillary ridge.' When a droplet slides along a substrate, the movement of the elastocapillary ridge dissipates energy in the substrate and slows the droplet down. Previous studies have analyzed isotropically spreading droplets and found that the advancing contact line `surfs' the elastocapillary ridge, with a velocity determined by a local balance of capillary forces and bulk rheology. Here, we experimentally explore the dynamics of a droplet sliding across soft substrates. At low velocities, the contact line is nearly circular, and dissipation increases logarithmically with speed. At higher droplet velocities, the contact line adopts a bullet-like shape, and the dissipation levels off. At the same time, droplets shed a pair of `elastocapillary rails' that fade away slowly behind it. These results suggest that droplets favor sliding along a stationary ridge over surfing atop a translating one.
{"title":"Droplets sliding on soft solids shed elastocapillary rails","authors":"Nan Xue, Lawrence A. Wilen, Robert W. Style, Eric R. Dufresne","doi":"arxiv-2409.00280","DOIUrl":"https://doi.org/arxiv-2409.00280","url":null,"abstract":"The surface tension of partially wetting droplets deforms soft substrates.\u0000These deformations are usually localized to a narrow region near the contact\u0000line, forming a so-called `elastocapillary ridge.' When a droplet slides along\u0000a substrate, the movement of the elastocapillary ridge dissipates energy in the\u0000substrate and slows the droplet down. Previous studies have analyzed\u0000isotropically spreading droplets and found that the advancing contact line\u0000`surfs' the elastocapillary ridge, with a velocity determined by a local\u0000balance of capillary forces and bulk rheology. Here, we experimentally explore\u0000the dynamics of a droplet sliding across soft substrates. At low velocities,\u0000the contact line is nearly circular, and dissipation increases logarithmically\u0000with speed. At higher droplet velocities, the contact line adopts a bullet-like\u0000shape, and the dissipation levels off. At the same time, droplets shed a pair\u0000of `elastocapillary rails' that fade away slowly behind it. These results\u0000suggest that droplets favor sliding along a stationary ridge over surfing atop\u0000a translating one.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"60 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220669","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In biological system like cell the macromolecules which are anisotropic particles diffuse in a crowded medium. In the present work we have studied the diffusion of spheroidal particles diffusing between cylindrical obstacles by varying the density of the obstacles as well as the spheroidal particles. Analytical calculation of the free energy showed that the orientational vector of a single oblate particle will be aligned perpendicular and a prolate particle will be aligned parallel to the symmetry axis of the cylindrical obstacles in equilibrium. The nematic transition of the system with and without obstacle remained the same, but in the case of obstacles the nematic vector of the spheroid system always remained parallel to the cylindrical axis. The component of the translational diffusion coefficient of the spheroidal particle perpendicular to the axis of the cylinder is calculated for isotropic system which agrees with analytical calculation. When the cylinders overlap such that the spheroidal particles can only diffuse along the direction parallel to the axis of the cylinder we could observe dimensional confinement. This was observed by the discontinuous fall of the diffusion coefficient, when plotted against the chemical potential both for single particle as well as for finite volume fraction. The rotational diffusion coefficient quickly reached the bulk value as the distance between the obstacle increased in the isotropic phase. In the nematic phase the rotational motion of the spheroid should be arrested. We observed that even though the entire system remained in the nematic phase the oblate particle close to the cylinder underwent flipping motion. The consequence is that when the rotational mean squared displacement was calculated it showed a super-diffusive behavior even though the orientational self correlation function never relaxed to zero.
{"title":"Dimensional confinement and superdiffusive rotational motion of uniaxial colloids in the presence of cylindrical obstacles","authors":"Vikki Anand Varma, Sujin B Babu","doi":"arxiv-2408.17345","DOIUrl":"https://doi.org/arxiv-2408.17345","url":null,"abstract":"In biological system like cell the macromolecules which are anisotropic\u0000particles diffuse in a crowded medium. In the present work we have studied the\u0000diffusion of spheroidal particles diffusing between cylindrical obstacles by\u0000varying the density of the obstacles as well as the spheroidal particles.\u0000Analytical calculation of the free energy showed that the orientational vector\u0000of a single oblate particle will be aligned perpendicular and a prolate\u0000particle will be aligned parallel to the symmetry axis of the cylindrical\u0000obstacles in equilibrium. The nematic transition of the system with and without\u0000obstacle remained the same, but in the case of obstacles the nematic vector of\u0000the spheroid system always remained parallel to the cylindrical axis. The\u0000component of the translational diffusion coefficient of the spheroidal particle\u0000perpendicular to the axis of the cylinder is calculated for isotropic system\u0000which agrees with analytical calculation. When the cylinders overlap such that\u0000the spheroidal particles can only diffuse along the direction parallel to the\u0000axis of the cylinder we could observe dimensional confinement. This was\u0000observed by the discontinuous fall of the diffusion coefficient, when plotted\u0000against the chemical potential both for single particle as well as for finite\u0000volume fraction. The rotational diffusion coefficient quickly reached the bulk\u0000value as the distance between the obstacle increased in the isotropic phase. In\u0000the nematic phase the rotational motion of the spheroid should be arrested. We\u0000observed that even though the entire system remained in the nematic phase the\u0000oblate particle close to the cylinder underwent flipping motion. The\u0000consequence is that when the rotational mean squared displacement was\u0000calculated it showed a super-diffusive behavior even though the orientational\u0000self correlation function never relaxed to zero.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"8 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220670","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Granular heaps are critical in both industrial applications and natural processes, exhibiting complex behaviors that have sparked significant research interest. The stress dip phenomenon observed beneath granular heaps continues to be a topic of significant debate. Current models based on force transmission often assume that the packing is near the isostatic point, overlooking the critical influence of internal structure and formation history on the mechanical properties of granular heaps. Consequently, these models fail to fully account for diverse observations. In this study, we experimentally explore the structural evolution of three dimensional (3D) granular heaps composed of monodisperse spherical particles prepared using the raining method. Our results reveal the presence of two distinct regions within the heaps, characterized by significant differences in structural properties such as packing fraction, contact number, and contact anisotropy. We attribute these structural variations to the differing formation mechanisms during heap growth. Our findings emphasize the substantial influence of the preparation protocols on the internal structure of granular heaps and provide valuable insights into stress distribution within granular materials. This research may contribute to the development of more accurate constitutive relations for granular materials by informing and refining future modeling approaches
{"title":"Microscopic Structural Study on the Growth History of Granular Heaps Prepared by the Raining Method","authors":"Hanyu Li, Houfei Yuan, Zhikun Zeng, Shuyang Zhang, Chijin Zhou, Xinyu Ai, Yujie Wang","doi":"arxiv-2408.17147","DOIUrl":"https://doi.org/arxiv-2408.17147","url":null,"abstract":"Granular heaps are critical in both industrial applications and natural\u0000processes, exhibiting complex behaviors that have sparked significant research\u0000interest. The stress dip phenomenon observed beneath granular heaps continues\u0000to be a topic of significant debate. Current models based on force transmission\u0000often assume that the packing is near the isostatic point, overlooking the\u0000critical influence of internal structure and formation history on the\u0000mechanical properties of granular heaps. Consequently, these models fail to\u0000fully account for diverse observations. In this study, we experimentally\u0000explore the structural evolution of three dimensional (3D) granular heaps\u0000composed of monodisperse spherical particles prepared using the raining method.\u0000Our results reveal the presence of two distinct regions within the heaps,\u0000characterized by significant differences in structural properties such as\u0000packing fraction, contact number, and contact anisotropy. We attribute these\u0000structural variations to the differing formation mechanisms during heap growth.\u0000Our findings emphasize the substantial influence of the preparation protocols\u0000on the internal structure of granular heaps and provide valuable insights into\u0000stress distribution within granular materials. This research may contribute to\u0000the development of more accurate constitutive relations for granular materials\u0000by informing and refining future modeling approaches","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220674","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Through the decomposition of the pressure into the kinetic and the intermolecular contributions, we show that the pressure anisotropy in the fluid interface, which is the source of the interfacial tension, comes solely from the latter contribution. The pressure anisotropy due to the intermolecular force between the fluid particles in the same or the different fluid components is approximately proportional to the multiplication of the corresponding fluid density gradients, and from the molecular dynamics simulation of the liquid-vapor and liquid-liquid interfaces, we demonstrate that the density gradient theory (DGT) by van der Waals gives the leading order approximation of the free energy density in inhomogeneous systems, neglecting the Tolman length.
{"title":"Molecular anatomy of the pressure anisotropy in the interface of one and two component fluids: local thermodynamic description of the interfacial tension","authors":"Takeshi Omori, Yasutaka Yamaguchi","doi":"arxiv-2408.17038","DOIUrl":"https://doi.org/arxiv-2408.17038","url":null,"abstract":"Through the decomposition of the pressure into the kinetic and the\u0000intermolecular contributions, we show that the pressure anisotropy in the fluid\u0000interface, which is the source of the interfacial tension, comes solely from\u0000the latter contribution. The pressure anisotropy due to the intermolecular\u0000force between the fluid particles in the same or the different fluid components\u0000is approximately proportional to the multiplication of the corresponding fluid\u0000density gradients, and from the molecular dynamics simulation of the\u0000liquid-vapor and liquid-liquid interfaces, we demonstrate that the density\u0000gradient theory (DGT) by van der Waals gives the leading order approximation of\u0000the free energy density in inhomogeneous systems, neglecting the Tolman length.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-30","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220675","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Polyampholytes (PA) are charged polymers composed of positively and negatively charged monomers along their backbone. The sequence of the charged monomers and the bending of the chain significantly influence the conformation and dynamical behavior of the PA. Using coarse-grained molecular dynamics simulations, we comprehensively study the structural and dynamical properties of flexible and semi-flexible polyampholytes'. The simulation results demonstrate a flexible polyampholyte (PA) chain, displaying a transition from a coil to a globule in the parameter space of the charge sequence. Additionally, the behavior of the mean-square displacement (MSD), denoted as $<(Delta r(t))^2>$, reveals distinct dynamics, specifically for the alternating and charge-segregated sequences. The MSD follows a power-law behavior, where $<(Delta r(t))^2> sim t^beta$, with $beta approx 3/5$ and $beta approx 1/2$ for the alternating sequence and charge-segregated sequence in the absence of hydrodynamic interactions, respectively. However, when hydrodynamic interactions are incorporated, the exponent $beta$ shifts to approximately 3/5 for the charge-segregated sequence and 2/3 for the well-mixed alternating sequence. For a semi-flexible PA chain, varying the bending rigidity and electrostatic interaction strength ($Gamma_e$) leads to distinct, fascinating conformational states, including globule, bundle, and torus-like conformations. We show that PA acquires circular and hairpin-like conformations in the intermediate bending regime. The transition between various conformations is identified in terms of the shape factor estimated from the ratios of eigenvalues of the gyration tensor.
聚酰胺（PA）是由带正电和带负电的单体沿主干组成的带电聚合物。带电单体的序列和链的弯曲对 PA 的构象和动力学行为有重大影响。利用粗粒度分子动力学模拟，我们全面研究了柔性和半柔性聚酰胺的结构和动力学特性。模拟结果表明，柔性聚酰胺（PA）链在电荷序列的参数空间中显示出从 "oil "到 "globule "的过渡。此外，均方位移（MSD）（用$$表示）的行为也显示了不同的动态，特别是交替序列和电荷分离序列。MSD 遵循幂律行为，其中$ sim t^beta$，在没有流体动力学相互作用的情况下，交替序列和电荷隔离序列的MSD分别为$ beta about 3/5$和$ beta approx1/2$。然而，当加入流体动力学相互作用时，电荷分离序列的指数$beta$约为3/5，而混合良好的交替序列的指数$beta$约为2/3。对于半柔性 PA 链，改变弯曲刚度和静电相互作用强度（$Gamma_e$）会导致不同的、迷人的构象状态，包括球状、束状和环状构象。我们发现 PA 在中间弯曲机制中获得了环状和发夹状构象。各种构象之间的转换是通过从回旋张量特征值的比率估算出的形状因子来识别的。
{"title":"Structural transitions of a Semi-Flexible Polyampholyte","authors":"Rakesh Palariya, Sunil P. Singh","doi":"arxiv-2408.15921","DOIUrl":"https://doi.org/arxiv-2408.15921","url":null,"abstract":"Polyampholytes (PA) are charged polymers composed of positively and\u0000negatively charged monomers along their backbone. The sequence of the charged\u0000monomers and the bending of the chain significantly influence the conformation\u0000and dynamical behavior of the PA. Using coarse-grained molecular dynamics\u0000simulations, we comprehensively study the structural and dynamical properties\u0000of flexible and semi-flexible polyampholytes'. The simulation results\u0000demonstrate a flexible polyampholyte (PA) chain, displaying a transition from a\u0000coil to a globule in the parameter space of the charge sequence. Additionally,\u0000the behavior of the mean-square displacement (MSD), denoted as $<(Delta\u0000r(t))^2>$, reveals distinct dynamics, specifically for the alternating and\u0000charge-segregated sequences. The MSD follows a power-law behavior, where\u0000$<(Delta r(t))^2> sim t^beta$, with $beta approx 3/5$ and $beta approx\u00001/2$ for the alternating sequence and charge-segregated sequence in the absence\u0000of hydrodynamic interactions, respectively. However, when hydrodynamic\u0000interactions are incorporated, the exponent $beta$ shifts to approximately 3/5\u0000for the charge-segregated sequence and 2/3 for the well-mixed alternating\u0000sequence. For a semi-flexible PA chain, varying the bending rigidity and\u0000electrostatic interaction strength ($Gamma_e$) leads to distinct, fascinating\u0000conformational states, including globule, bundle, and torus-like conformations.\u0000We show that PA acquires circular and hairpin-like conformations in the\u0000intermediate bending regime. The transition between various conformations is\u0000identified in terms of the shape factor estimated from the ratios of\u0000eigenvalues of the gyration tensor.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"5 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220676","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We present a study combining experimental measurements, theoretical analysis, and simulations to investigate core-shell microcapsules interacting with a solid boundary, with a particular focus on understanding the short-range potential energy well arising from the tethered force. The microcapsules, fabricated using a Pickering emulsion template with a cinnamon oil core and calcium alginate shell, were characterized for size (5-6 microns in diameter) and surface charge (-20 mV). We employed total internal reflection microscopy and particle tracking to measure the microcapsule-boundary interactions and diffusion, from which potential energy and diffusivity profiles were derived. The potential energy profile was analyzed and simulated by considering electrostatic, gravitational, and tethered forces, while the diffusivity was compared to that of a solid particle-boundary interaction, inclusive of hydrodynamic forces. The diffusivity was represented as a normalized diffusion coefficient to eliminate the impact of fluid viscosity. The normalized diffusion coefficient of polymer-shell microcapsules (0.02) was found to be an order of magnitude smaller than that of solid polystyrene particles (0.2). The microcapsule sampled a potential well consisting of two distinct minima, as observed experimentally and supported by analytical expressions and Brownian dynamics simulations. A critical tethered height (49.8 nm) and the alginate radius of (35.2 nm) were obtained from fitting our model to experimental data. This work concludes that these benign core shell microcapsules interact with a nearby boundary via a transient tethering interaction, overall producing a mild sticky interaction that would likely be beneficial for applications in consumer products.
{"title":"Direct measurement of surface interactions experienced by sticky microcapsules made from environmentally benign materials","authors":"Hairou Yu, Christopher L. Wirth","doi":"arxiv-2408.15945","DOIUrl":"https://doi.org/arxiv-2408.15945","url":null,"abstract":"We present a study combining experimental measurements, theoretical analysis,\u0000and simulations to investigate core-shell microcapsules interacting with a\u0000solid boundary, with a particular focus on understanding the short-range\u0000potential energy well arising from the tethered force. The microcapsules,\u0000fabricated using a Pickering emulsion template with a cinnamon oil core and\u0000calcium alginate shell, were characterized for size (5-6 microns in diameter)\u0000and surface charge (-20 mV). We employed total internal reflection microscopy\u0000and particle tracking to measure the microcapsule-boundary interactions and\u0000diffusion, from which potential energy and diffusivity profiles were derived.\u0000The potential energy profile was analyzed and simulated by considering\u0000electrostatic, gravitational, and tethered forces, while the diffusivity was\u0000compared to that of a solid particle-boundary interaction, inclusive of\u0000hydrodynamic forces. The diffusivity was represented as a normalized diffusion\u0000coefficient to eliminate the impact of fluid viscosity. The normalized\u0000diffusion coefficient of polymer-shell microcapsules (0.02) was found to be an\u0000order of magnitude smaller than that of solid polystyrene particles (0.2). The\u0000microcapsule sampled a potential well consisting of two distinct minima, as\u0000observed experimentally and supported by analytical expressions and Brownian\u0000dynamics simulations. A critical tethered height (49.8 nm) and the alginate\u0000radius of (35.2 nm) were obtained from fitting our model to experimental data.\u0000This work concludes that these benign core shell microcapsules interact with a\u0000nearby boundary via a transient tethering interaction, overall producing a mild\u0000sticky interaction that would likely be beneficial for applications in consumer\u0000products.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"15 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220819","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Sophie Baker, Gareth R. Elliott, Erica J. Wanless, Grant B. Webber, Vincent S. J. Craig, Alister J. Page
Over the last decade, experimental measurements of electrostatic screening lengths in concentrated electrolytes have exceeded theoretical predictions by orders of magnitude. This disagreement has led to a paradigm in which such screening lengths are referred to as 'anomalous underscreening', while others - predominantly those predicted by theory and molecular simulation - are referred to as 'normal underscreening'. Herein we use discrete Fourier analysis of the radial charge density obtained from molecular dynamics simulations to reveal the origin of anomalous underscreening in concentrated electrolytes. Normal underscreening above the Kirkwood point arises from low-frequency decay modes of the electrostatic potential, while anomalous underscreening arises from high-frequency decay modes that are observed only at high concentrations. The screening length associated with a particular decay mode is in turn determined by the degree of short-range interference between ion-ion correlation functions. The long-range decay associated with anomalous underscreening is thus ultimately determined by short range structure in the bulk electrolyte. These results reconcile the disagreement between experimental measurements and theoretical predictions of screening lengths in concentrated electrolytes.
{"title":"There is Nothing Anomalous about 'Anomalous' Underscreening in Concentrated Electrolytes","authors":"Sophie Baker, Gareth R. Elliott, Erica J. Wanless, Grant B. Webber, Vincent S. J. Craig, Alister J. Page","doi":"arxiv-2408.15685","DOIUrl":"https://doi.org/arxiv-2408.15685","url":null,"abstract":"Over the last decade, experimental measurements of electrostatic screening\u0000lengths in concentrated electrolytes have exceeded theoretical predictions by\u0000orders of magnitude. This disagreement has led to a paradigm in which such\u0000screening lengths are referred to as 'anomalous underscreening', while others -\u0000predominantly those predicted by theory and molecular simulation - are referred\u0000to as 'normal underscreening'. Herein we use discrete Fourier analysis of the\u0000radial charge density obtained from molecular dynamics simulations to reveal\u0000the origin of anomalous underscreening in concentrated electrolytes. Normal\u0000underscreening above the Kirkwood point arises from low-frequency decay modes\u0000of the electrostatic potential, while anomalous underscreening arises from\u0000high-frequency decay modes that are observed only at high concentrations. The\u0000screening length associated with a particular decay mode is in turn determined\u0000by the degree of short-range interference between ion-ion correlation\u0000functions. The long-range decay associated with anomalous underscreening is\u0000thus ultimately determined by short range structure in the bulk electrolyte.\u0000These results reconcile the disagreement between experimental measurements and\u0000theoretical predictions of screening lengths in concentrated electrolytes.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"39 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142220679","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
In floppy mechanical lattices, robust edge states and bulk Weyl modes are manifestations of underlying topological invariants. To explore the universality of these phenomena independent of microscopic detail, we formulate topological mechanics in the continuum. By augmenting standard linear elasticity with additional fields of soft modes, we define a continuum version of Maxwell counting, which balances degrees of freedom and mechanical constraints. With one additional field, these augmented elasticity theories can break spatial inversion symmetry and harbor topological edge states. We also show that two additional fields are necessary to harbor Weyl points in two dimensions, and define continuum invariants to classify these states. In addition to constructing the general form of topological elasticity based on symmetries, we derive the coefficients based on the systematic homogenization of microscopic lattices. By solving the resulting partial differential equations, we efficiently predict coarse-grained deformations due to topological floppy modes without the need for a detailed lattice-based simulation. Our discovery formulates novel design principles and efficient computational tools for topological states of matter, and points to their experimental implementation in mechanical metamaterials.
{"title":"Classifying topological floppy modes in the continuum","authors":"Ian Tan, Anton Souslov","doi":"arxiv-2408.15850","DOIUrl":"https://doi.org/arxiv-2408.15850","url":null,"abstract":"In floppy mechanical lattices, robust edge states and bulk Weyl modes are\u0000manifestations of underlying topological invariants. To explore the\u0000universality of these phenomena independent of microscopic detail, we formulate\u0000topological mechanics in the continuum. By augmenting standard linear\u0000elasticity with additional fields of soft modes, we define a continuum version\u0000of Maxwell counting, which balances degrees of freedom and mechanical\u0000constraints. With one additional field, these augmented elasticity theories can\u0000break spatial inversion symmetry and harbor topological edge states. We also\u0000show that two additional fields are necessary to harbor Weyl points in two\u0000dimensions, and define continuum invariants to classify these states. In\u0000addition to constructing the general form of topological elasticity based on\u0000symmetries, we derive the coefficients based on the systematic homogenization\u0000of microscopic lattices. By solving the resulting partial differential\u0000equations, we efficiently predict coarse-grained deformations due to\u0000topological floppy modes without the need for a detailed lattice-based\u0000simulation. Our discovery formulates novel design principles and efficient\u0000computational tools for topological states of matter, and points to their\u0000experimental implementation in mechanical metamaterials.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"2 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227386","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Jordan Hobbs, Calum J. Gibb, Damian Pociecha, Jadwiga Szydłowska, Ewa Górecka, Richard. J. Mandle
The discovery of fluid states of matter with spontaneous bulk polar order is appreciated as a major discovery in the fields of soft matter and liquid crystals. Typically, this manifests as polar order superimposed atop conventional phase structures and is thus far limited to orthogonal phase types. Here we report a family of materials which exhibit a previously unseen state of matter which we conclude is a polar smectic C phase, and so we term it SmC${_textrm{P}}$. The spontaneous polarisation of the SmC${_textrm{P}}$ phase is over two orders of magnitude larger than that found in conventional ferroelectric SmC phase of chiral materials used in some LCD devices. Fully atomistic molecular dynamics simulations faithfully and spontaneously reproduce the proposed structure and associated bulk properties; comparison of experimental and simulated X-ray scattering patterns shows excellent agreement. The materials disclosed here have significantly smaller dipole moments than typical polar liquid crystals such as RM734 which suggests the role of molecular electrical polarity in generating polar order is perhaps overstated, a view supported by consideration of other molecular systems.
具有自发体极性阶的流态物质的发现是软物质和液晶领域的重大发现。通常情况下，这表现为叠加在传统相结构之上的极性有序，迄今为止仅限于正交相型。在这里，我们报告了一系列材料，它们展示了一种以前从未见过的物质状态，我们断定这是一种极性共晶 C 相，因此我们称之为 SmC${_textrm{P}}$。SmC${_textrm{P}}$相的自发极化比某些液晶显示设备中使用的手性材料的传统铁电SmC相的自发极化大两个数量级以上。完全原子分子动力学模拟忠实地、自发地再现了所提出的结构和相关的体质特性；实验和模拟 X 射线散射模式的比较显示出极好的一致性。本文所揭示的材料的偶极矩明显小于典型的极性液晶（如 RM734），这表明分子电极性在产生极性秩序中的作用可能被夸大了，而对其他分子系统的研究也支持这一观点。
{"title":"Polar order in a fluid like ferroelectric with a tilted lamellar structure -- observation of a polar smectic C (SmC${_textrm{P}}$) phase","authors":"Jordan Hobbs, Calum J. Gibb, Damian Pociecha, Jadwiga Szydłowska, Ewa Górecka, Richard. J. Mandle","doi":"arxiv-2408.15859","DOIUrl":"https://doi.org/arxiv-2408.15859","url":null,"abstract":"The discovery of fluid states of matter with spontaneous bulk polar order is\u0000appreciated as a major discovery in the fields of soft matter and liquid\u0000crystals. Typically, this manifests as polar order superimposed atop\u0000conventional phase structures and is thus far limited to orthogonal phase\u0000types. Here we report a family of materials which exhibit a previously unseen\u0000state of matter which we conclude is a polar smectic C phase, and so we term it\u0000SmC${_textrm{P}}$. The spontaneous polarisation of the SmC${_textrm{P}}$\u0000phase is over two orders of magnitude larger than that found in conventional\u0000ferroelectric SmC phase of chiral materials used in some LCD devices. Fully\u0000atomistic molecular dynamics simulations faithfully and spontaneously reproduce\u0000the proposed structure and associated bulk properties; comparison of\u0000experimental and simulated X-ray scattering patterns shows excellent agreement.\u0000The materials disclosed here have significantly smaller dipole moments than\u0000typical polar liquid crystals such as RM734 which suggests the role of\u0000molecular electrical polarity in generating polar order is perhaps overstated,\u0000a view supported by consideration of other molecular systems.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"101 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-28","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"142227871","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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