Souhaila Nider, Femke De Ceulaer, Berfu Göksel, Annabel Braem, Erin Koos
The increasing demand for bone grafts due to the aging population has openednew opportunities for the manufacture of porous ceramics to assist in bonereconstruction. In our study, we investigate a new, promising method tomanufacture hierarchically porous structures in a straightforward, and tuneableway. It consists of combining the novel technology of capillary suspensions,formed by mixing solid particles and two immiscible liquids, one less than 5vol%, with freeze casting. We have successfully achieved alumina and$beta$-TCP materials with both <2 $mu$m and 20-50 $mu$m as the smallest andlargest pore size, respectively. The microstructure exhibits fully open poresand high levels of porosity (> 60%). The capillary suspensions' rheologicalbehaviour indicates that silica nano-suspensions as a secondary fluid creates astronger internal particle network than sucrose for the alumina system.Conversely, the opposite was observed with the $beta$-TCP system. Thesedifferences were attributed to the change in affinity between the secondaryfluids and the solid loading. In our study, both systems have served to deepenthe knowledge about the new area of capillary suspensions and prove their usein hierarchical porous scaffolds for bone tissue engineering.
{"title":"Hierarchical materials with interconnected pores from capillary suspensions for bone tissue engineering","authors":"Souhaila Nider, Femke De Ceulaer, Berfu Göksel, Annabel Braem, Erin Koos","doi":"arxiv-2408.04337","DOIUrl":"https://doi.org/arxiv-2408.04337","url":null,"abstract":"The increasing demand for bone grafts due to the aging population has opened\u0000new opportunities for the manufacture of porous ceramics to assist in bone\u0000reconstruction. In our study, we investigate a new, promising method to\u0000manufacture hierarchically porous structures in a straightforward, and tuneable\u0000way. It consists of combining the novel technology of capillary suspensions,\u0000formed by mixing solid particles and two immiscible liquids, one less than 5\u0000vol%, with freeze casting. We have successfully achieved alumina and\u0000$beta$-TCP materials with both <2 $mu$m and 20-50 $mu$m as the smallest and\u0000largest pore size, respectively. The microstructure exhibits fully open pores\u0000and high levels of porosity (> 60%). The capillary suspensions' rheological\u0000behaviour indicates that silica nano-suspensions as a secondary fluid creates a\u0000stronger internal particle network than sucrose for the alumina system.\u0000Conversely, the opposite was observed with the $beta$-TCP system. These\u0000differences were attributed to the change in affinity between the secondary\u0000fluids and the solid loading. In our study, both systems have served to deepen\u0000the knowledge about the new area of capillary suspensions and prove their use\u0000in hierarchical porous scaffolds for bone tissue engineering.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"57 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937292","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}
Cody D. Schimming, C. J. O. Reichhardt, C. Reichhardt
We develop an approximate, analytical model for the velocity of defects inactive nematics by combining recent results for the velocity of topologicaldefects in nematic liquid crystals with the flow field generated fromindividual defects in active nematics. Importantly, our model takes intoaccount the long-range interactions between defects that result from the flowsthey produce as well as the orientational coupling between defects inherent innematics. We show that the model can analytically predict bound states betweentwo $+1/2$ winding number defects, effective attraction between two $-1/2$defects, and the scaling of a critical unbinding length between $pm 1/2$defects with activity. The model also gives predictions for the trajectories ofdefects, such as the scattering of $+1/2$ defects by $-1/2$ defects at acritical impact parameter that depends on activity. In the presence of circularconfinement, the model predicts a braiding motion for three $+1/2$ defects thatwas recently seen in experiments.
{"title":"Analytical model for the motion and interaction of two-dimensional active nematic defects","authors":"Cody D. Schimming, C. J. O. Reichhardt, C. Reichhardt","doi":"arxiv-2408.04706","DOIUrl":"https://doi.org/arxiv-2408.04706","url":null,"abstract":"We develop an approximate, analytical model for the velocity of defects in\u0000active nematics by combining recent results for the velocity of topological\u0000defects in nematic liquid crystals with the flow field generated from\u0000individual defects in active nematics. Importantly, our model takes into\u0000account the long-range interactions between defects that result from the flows\u0000they produce as well as the orientational coupling between defects inherent in\u0000nematics. We show that the model can analytically predict bound states between\u0000two $+1/2$ winding number defects, effective attraction between two $-1/2$\u0000defects, and the scaling of a critical unbinding length between $pm 1/2$\u0000defects with activity. The model also gives predictions for the trajectories of\u0000defects, such as the scattering of $+1/2$ defects by $-1/2$ defects at a\u0000critical impact parameter that depends on activity. In the presence of circular\u0000confinement, the model predicts a braiding motion for three $+1/2$ defects that\u0000was recently seen in experiments.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"307 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937369","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}
DNA is now firmly established as a versatile and robust platform forachieving synthetic nanostructures. While the folding of single molecules intocomplex structures is routinely achieved through engineering basepairsequences, much less is known about the emergence of structure on larger scalesin DNA fluids. The fact that polymeric DNA fluids can undergo phase separationinto dense fluid and dilute gas opens avenues to design hierachical andmultifarious assemblies. Here we investigate to which extent the phase behaviorof single-stranded DNA fluids is captured by a minimal model of semiflexiblecharged homopolymers while neglecting specific hybridization interactions. Wefirst characterize the single-polymer behavior and then perform directcoexistence simulations to test the model against experimental data. Weconclude that counterions not only determine the effective range of directelectrostatic interactions but also the effective attractions.
DNA 现已成为实现合成纳米结构的通用而强大的平台。单分子折叠成复杂结构通常是通过碱基配对序列工程实现的,但人们对 DNA 流体中更大规模结构的出现却知之甚少。事实上,聚合 DNA 流体可以在稠密流体和稀薄气体之间发生相分离,这为设计层次丰富的组装体开辟了道路。在这里,我们研究了单链 DNA 流体的相行为在多大程度上可以被忽略特定杂交相互作用的半柔性带电均聚物的最小模型所捕获。我们首先描述了单聚合物的行为特征,然后进行了直接共存模拟,根据实验数据对模型进行了检验。我们得出结论:反离子不仅决定了直接静电相互作用的有效范围,还决定了有效吸引力。
{"title":"Coarse-grained models for phase separation in DNA-based fluids","authors":"Soumen De Karmakar, Thomas Speck","doi":"arxiv-2408.04435","DOIUrl":"https://doi.org/arxiv-2408.04435","url":null,"abstract":"DNA is now firmly established as a versatile and robust platform for\u0000achieving synthetic nanostructures. While the folding of single molecules into\u0000complex structures is routinely achieved through engineering basepair\u0000sequences, much less is known about the emergence of structure on larger scales\u0000in DNA fluids. The fact that polymeric DNA fluids can undergo phase separation\u0000into dense fluid and dilute gas opens avenues to design hierachical and\u0000multifarious assemblies. Here we investigate to which extent the phase behavior\u0000of single-stranded DNA fluids is captured by a minimal model of semiflexible\u0000charged homopolymers while neglecting specific hybridization interactions. We\u0000first characterize the single-polymer behavior and then perform direct\u0000coexistence simulations to test the model against experimental data. We\u0000conclude that counterions not only determine the effective range of direct\u0000electrostatic interactions but also the effective attractions.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"11 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-08","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937371","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}
Fast-Fourier Transform (FFT) methods have been widely used in solid mechanicsto address complex homogenization problems. However, current FFT-based methodsface challenges that limit their applicability to intricate material models orcomplex mechanical problems. These challenges include the manual implementationof constitutive laws and the use of computationally expensive and complexalgorithms to couple microscale mechanisms to macroscale material behavior.Here, we incorporate automatic differentiation (AD) within the FFT framework tomitigate these challenges. We demonstrate that AD-enhanced FFT-based methodscan derive stress and tangent stiffness directly from energy densityfunctionals, facilitating the extension of FFT-based methods to more intricatematerial models. Additionally, AD simplifies the calculation of homogenizedtangent stiffness for microstructures with complex architectures andconstitutive properties. This enhancement renders current FFT-based methodsmore modular, enabling them to tackle homogenization in complex multiscalesystems, especially those involving multiphysics processes. Our work willsimplify the numerical implementation of FFT-based methods for complex solidmechanics problems.
{"title":"Simplifying FFT-based methods for mechanics with automatic differentiation","authors":"Mohit Pundir, David S. Kammer","doi":"arxiv-2408.03804","DOIUrl":"https://doi.org/arxiv-2408.03804","url":null,"abstract":"Fast-Fourier Transform (FFT) methods have been widely used in solid mechanics\u0000to address complex homogenization problems. However, current FFT-based methods\u0000face challenges that limit their applicability to intricate material models or\u0000complex mechanical problems. These challenges include the manual implementation\u0000of constitutive laws and the use of computationally expensive and complex\u0000algorithms to couple microscale mechanisms to macroscale material behavior.\u0000Here, we incorporate automatic differentiation (AD) within the FFT framework to\u0000mitigate these challenges. We demonstrate that AD-enhanced FFT-based methods\u0000can derive stress and tangent stiffness directly from energy density\u0000functionals, facilitating the extension of FFT-based methods to more intricate\u0000material models. Additionally, AD simplifies the calculation of homogenized\u0000tangent stiffness for microstructures with complex architectures and\u0000constitutive properties. This enhancement renders current FFT-based methods\u0000more modular, enabling them to tackle homogenization in complex multiscale\u0000systems, especially those involving multiphysics processes. Our work will\u0000simplify the numerical implementation of FFT-based methods for complex solid\u0000mechanics problems.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"1 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141968981","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 this work, we determine the dissociation line of the nitrogen (N$_{2}$)hydrate by computer simulation using the TIP4P/Ice model for water and theTraPPE force field for N$_{2}$. This work is the natural extension of ourprevious paper in which the dissociation temperature of the N$_2$ hydrate hasbeen obtained at $500$, $1000$, and $1500,text{bar}$ [emph{J. Chem. Phys.}textbf{159}, 224707 (2023)] using the solubility method and assuming singleoccupancy. We extend our previous study and determine the dissociationtemperature of the N$_2$ hydrate at different pressures, from $500$ to$4500,text{bar}$, taking into account single and double occupancy of theN$_{2}$ molecules in the hydrate structure. We calculate the solubility ofN$_2$ in the aqueous solution, as a function of temperature, when it is incontact with a N$_{2}$-rich liquid phase and when in contact with the hydratephase with single and double occupancy via planar interfaces. Both curvesintersect at a certain temperature that determines the dissociation temperatureat a given pressure. We observe a negligible effect of the occupancy on thedissociation temperature. Our findings are in very good agreement with theexperimental data taken from the literature. We have also obtained the drivingforce for nucleation of the hydrate as a function of the temperature andoccupancy at several pressures. As in the case of the dissociation line, theeffect of the occupancy on the driving force for nucleation is negligible. Tothe best of our knowledge, this is the first time that the effect of theoccupancy on the driving force for nucleation of a hydrate that exhibits sIIcrystallographic structure is studied from computer simulation.
{"title":"Dissociation line and driving force for nucleation of the nitrogen hydrate from computer simulation. II. Effect of multiple occupancy","authors":"Miguel J. Torrejón, Jesús Algaba, Felipe J. Blas","doi":"arxiv-2408.03257","DOIUrl":"https://doi.org/arxiv-2408.03257","url":null,"abstract":"In this work, we determine the dissociation line of the nitrogen (N$_{2}$)\u0000hydrate by computer simulation using the TIP4P/Ice model for water and the\u0000TraPPE force field for N$_{2}$. This work is the natural extension of our\u0000previous paper in which the dissociation temperature of the N$_2$ hydrate has\u0000been obtained at $500$, $1000$, and $1500,text{bar}$ [emph{J. Chem. Phys.}\u0000textbf{159}, 224707 (2023)] using the solubility method and assuming single\u0000occupancy. We extend our previous study and determine the dissociation\u0000temperature of the N$_2$ hydrate at different pressures, from $500$ to\u0000$4500,text{bar}$, taking into account single and double occupancy of the\u0000N$_{2}$ molecules in the hydrate structure. We calculate the solubility of\u0000N$_2$ in the aqueous solution, as a function of temperature, when it is in\u0000contact with a N$_{2}$-rich liquid phase and when in contact with the hydrate\u0000phase with single and double occupancy via planar interfaces. Both curves\u0000intersect at a certain temperature that determines the dissociation temperature\u0000at a given pressure. We observe a negligible effect of the occupancy on the\u0000dissociation temperature. Our findings are in very good agreement with the\u0000experimental data taken from the literature. We have also obtained the driving\u0000force for nucleation of the hydrate as a function of the temperature and\u0000occupancy at several pressures. As in the case of the dissociation line, the\u0000effect of the occupancy on the driving force for nucleation is negligible. To\u0000the best of our knowledge, this is the first time that the effect of the\u0000occupancy on the driving force for nucleation of a hydrate that exhibits sII\u0000crystallographic structure is studied from computer simulation.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"90 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-06","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937289","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}
The elasticity of rubbery polymer networks has been considered to beentropy-driven. On the other hand, studies on single polymer chain mechanicshave revealed that the elasticity of ultimately stretched polymer chains isdominated by the energetic contribution mainly originating from chemical bonddeformation. Here, we experimentally found that the elasticity of thedouble-network gel transits from the entropy-dominated one to the internalenergy-driven one with its uniaxial deformation through the thermodynamicanalysis. Based on this finding, we developed a simple mechanical model thattakes into account the energetic contribution and found that this modelapproximately reproduces the temperature dependence of the stress-strain curveof the double-network gel. This study demonstrates the importance of thechemical perspective in the mechanical analysis of highly deformed rubberypolymer networks.
{"title":"Ultimately deformed double-network gels possess positive energetic elasticity","authors":"Chika Imaoka, Tatsunari Masumi, Jian Ping Gong, Tsutomu Indei, Tasuku Nakajima","doi":"arxiv-2408.02523","DOIUrl":"https://doi.org/arxiv-2408.02523","url":null,"abstract":"The elasticity of rubbery polymer networks has been considered to be\u0000entropy-driven. On the other hand, studies on single polymer chain mechanics\u0000have revealed that the elasticity of ultimately stretched polymer chains is\u0000dominated by the energetic contribution mainly originating from chemical bond\u0000deformation. Here, we experimentally found that the elasticity of the\u0000double-network gel transits from the entropy-dominated one to the internal\u0000energy-driven one with its uniaxial deformation through the thermodynamic\u0000analysis. Based on this finding, we developed a simple mechanical model that\u0000takes into account the energetic contribution and found that this model\u0000approximately reproduces the temperature dependence of the stress-strain curve\u0000of the double-network gel. This study demonstrates the importance of the\u0000chemical perspective in the mechanical analysis of highly deformed rubbery\u0000polymer networks.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"36 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937285","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}
Poly(N-isopropylacrylamide) (pNIPAM) microgels are renowned for theirthermoresponsive behavior, exhibiting a distinct volume phase transition (VPT)upon temperature changes. This study investigates the influence of microgelsoftness, controlled by varying the crosslinking density during synthesis viafree radical polymerization (FRP), on the difference between the volume phasetransition temperature (VPTT) and the electrokinetic transition temperature(ETT). These transition temperatures mark the points at which the microgel sizeand surface charge, respectively, undergo significant alterations in responseto temperature. Here, we investigate this phenomenon, employing dynamic lightscattering (DLS) and electrophoretic light scattering (ELS) measurements tocharacterize the size and electrophoretic mobility response of pNIPAM microgelswith different crosslinking densities as a function of temperature. Byanalyzing the observed trends in the difference between the transitiontemperatures, we aim to develop a hypothesis that provides a deeper physicalunderstanding of the microgel structure and its relationship to transitiontemperatures. This investigation thus sheds light on the intricate interplaybetween microgel structure and its thermoresponsive behavior, offering insightsfor the design and optimization of pNIPAM microgels for future applications.
{"title":"Role of softness on transition temperatures for pNIPAM microgels","authors":"Syamjith KS, Shubhasmita Rout, Alan R Jacob","doi":"arxiv-2408.02490","DOIUrl":"https://doi.org/arxiv-2408.02490","url":null,"abstract":"Poly(N-isopropylacrylamide) (pNIPAM) microgels are renowned for their\u0000thermoresponsive behavior, exhibiting a distinct volume phase transition (VPT)\u0000upon temperature changes. This study investigates the influence of microgel\u0000softness, controlled by varying the crosslinking density during synthesis via\u0000free radical polymerization (FRP), on the difference between the volume phase\u0000transition temperature (VPTT) and the electrokinetic transition temperature\u0000(ETT). These transition temperatures mark the points at which the microgel size\u0000and surface charge, respectively, undergo significant alterations in response\u0000to temperature. Here, we investigate this phenomenon, employing dynamic light\u0000scattering (DLS) and electrophoretic light scattering (ELS) measurements to\u0000characterize the size and electrophoretic mobility response of pNIPAM microgels\u0000with different crosslinking densities as a function of temperature. By\u0000analyzing the observed trends in the difference between the transition\u0000temperatures, we aim to develop a hypothesis that provides a deeper physical\u0000understanding of the microgel structure and its relationship to transition\u0000temperatures. This investigation thus sheds light on the intricate interplay\u0000between microgel structure and its thermoresponsive behavior, offering insights\u0000for the design and optimization of pNIPAM microgels for future applications.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"63 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937302","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}
Micro-organisms propel themselves in viscous environments by the periodic,nonreciprocal beating of slender appendages known as flagella. Active materialshave been widely exploited to mimic this form of locomotion. However, therealization of such coordinated beating in biomimetic flagella requires complexactuation modulated in space and time. We prove through experiments onpolyelectrolyte hydrogel samples that directed undulatory locomotion of a softrobotic swimmer can be achieved by untethered actuation from a uniform andstatic electric field. A minimal mathematical model is sufficient to reproduce,and thus explain, the observed behavior. The periodic beating of the swimminghydrogel robot emerges from flutter instability thanks to the interplay betweenits active and passive reconfigurations in the viscous environment.Interestingly, the flutter-driven soft robot exhibits a form of electrotaxiswhereby its swimming trajectory can be controlled by simply reorienting theelectric field. Our findings trace the route for the embodiment of mechanicalintelligence in soft robotic systems by the exploitation of flutter instabilityto achieve complex functional responses to simple stimuli. While theexperimental study is conducted on millimeter-scale hydrogel swimmers, thedesign principle we introduce requires simple geometry and is hence amenablefor miniaturization via micro-fabrication techniques. We believe it may also betransferred to a wider class of soft active materials.
{"title":"Minimal actuation and control of a soft hydrogel swimmer from flutter instability","authors":"Ariel Surya Boiardi, Giovanni Noselli","doi":"arxiv-2408.02560","DOIUrl":"https://doi.org/arxiv-2408.02560","url":null,"abstract":"Micro-organisms propel themselves in viscous environments by the periodic,\u0000nonreciprocal beating of slender appendages known as flagella. Active materials\u0000have been widely exploited to mimic this form of locomotion. However, the\u0000realization of such coordinated beating in biomimetic flagella requires complex\u0000actuation modulated in space and time. We prove through experiments on\u0000polyelectrolyte hydrogel samples that directed undulatory locomotion of a soft\u0000robotic swimmer can be achieved by untethered actuation from a uniform and\u0000static electric field. A minimal mathematical model is sufficient to reproduce,\u0000and thus explain, the observed behavior. The periodic beating of the swimming\u0000hydrogel robot emerges from flutter instability thanks to the interplay between\u0000its active and passive reconfigurations in the viscous environment.\u0000Interestingly, the flutter-driven soft robot exhibits a form of electrotaxis\u0000whereby its swimming trajectory can be controlled by simply reorienting the\u0000electric field. Our findings trace the route for the embodiment of mechanical\u0000intelligence in soft robotic systems by the exploitation of flutter instability\u0000to achieve complex functional responses to simple stimuli. While the\u0000experimental study is conducted on millimeter-scale hydrogel swimmers, the\u0000design principle we introduce requires simple geometry and is hence amenable\u0000for miniaturization via micro-fabrication techniques. We believe it may also be\u0000transferred to a wider class of soft active materials.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"10 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937374","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 simulations, particles are traditionally treated as rigid platforms withvariable sizes, shapes and interaction parameters. While this representation isapplicable for rigid core platforms, particles consisting of soft platforms(e.g. micelles, polymers, elastomers, lipids) inevitably deform uponapplication of external stress. We introduce a generic model for flexibleparticles which we call MetaParticles (MP). These particles have tunableproperties, can respond to applied tension and can deform. A metaparticle isrepresented as a collection of Lennard-Jones beads interconnected byspring-like potentials. We model a series of metaparticles of variable sizesand symmetries, which we subject to external stress followed by relaxation uponstress release. The positions and the orientations of the individual beads arepropagated by Brownian dynamics. The simulations show that the mechanicalproperties of the metaparticles vary with size, bead arrangement and area ofapplied stress, and share an elastomer-like response to applied stress.Furthermore, metaparticles deform following different mechanisms, i.e., smallMPs change shape in one step, while larger ones follow a multi-step deformationpathway, with internal rearrangements of the beads. This model is the firststep towards the development and understanding of particles with adaptableproperties with biomedical applications and in the design of bioinspiredmetamaterials.
{"title":"MetaParticles: Computationally engineered nanomaterials with tunable and responsive properties","authors":"Massimiliano Paesani, Ioana M. Ilie","doi":"arxiv-2408.02564","DOIUrl":"https://doi.org/arxiv-2408.02564","url":null,"abstract":"In simulations, particles are traditionally treated as rigid platforms with\u0000variable sizes, shapes and interaction parameters. While this representation is\u0000applicable for rigid core platforms, particles consisting of soft platforms\u0000(e.g. micelles, polymers, elastomers, lipids) inevitably deform upon\u0000application of external stress. We introduce a generic model for flexible\u0000particles which we call MetaParticles (MP). These particles have tunable\u0000properties, can respond to applied tension and can deform. A metaparticle is\u0000represented as a collection of Lennard-Jones beads interconnected by\u0000spring-like potentials. We model a series of metaparticles of variable sizes\u0000and symmetries, which we subject to external stress followed by relaxation upon\u0000stress release. The positions and the orientations of the individual beads are\u0000propagated by Brownian dynamics. The simulations show that the mechanical\u0000properties of the metaparticles vary with size, bead arrangement and area of\u0000applied stress, and share an elastomer-like response to applied stress.\u0000Furthermore, metaparticles deform following different mechanisms, i.e., small\u0000MPs change shape in one step, while larger ones follow a multi-step deformation\u0000pathway, with internal rearrangements of the beads. This model is the first\u0000step towards the development and understanding of particles with adaptable\u0000properties with biomedical applications and in the design of bioinspired\u0000metamaterials.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"57 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937373","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}
S. Blazquez, J. Algaba, J. M. Míguez, C. Vega, F. J. Blas, M. M. Conde
Clathrate hydrates are vital in energy research and environmentalapplications. Understanding their stability is crucial for harnessing theirpotential. In this work, we employ direct coexistence simulations to studyfinite-size effects in the determination of the three-phase equilibriumtemperature ($T_3$) for methane hydrates. Two popular water models, TIP4P/Iceand TIP4P/2005, are employed, exploring various system sizes by varying thenumber of molecules in the hydrate, liquid, and gas phases. The results revealthat finite-size effects play a crucial role in determining $T_3$. The studyincludes nine configurations with varying system sizes, demonstrating thatsmaller systems, particularly those leading to stoichiometric conditions andbubble formation, may yield inaccurate $T_3$ values. The emergence of methanebubbles within the liquid phase, observed in smaller configurations,significantly influences the behavior of the system and can lead to erroneoustemperature estimations. Our findings reveal finite size effects on thecalculation of the $T_3$ by direct coexistence simulations and clarify thesystem size convergence for both models, shedding light on discrepancies foundin the literature. The results contribute to a deeper understanding of thephase equilibrium of gas hydrates and offer valuable information for futureresearch in this field.
{"title":"Three-phase equilibria of hydrates from computer simulation. I. Finite-size effects in the methane hydrate","authors":"S. Blazquez, J. Algaba, J. M. Míguez, C. Vega, F. J. Blas, M. M. Conde","doi":"arxiv-2408.02098","DOIUrl":"https://doi.org/arxiv-2408.02098","url":null,"abstract":"Clathrate hydrates are vital in energy research and environmental\u0000applications. Understanding their stability is crucial for harnessing their\u0000potential. In this work, we employ direct coexistence simulations to study\u0000finite-size effects in the determination of the three-phase equilibrium\u0000temperature ($T_3$) for methane hydrates. Two popular water models, TIP4P/Ice\u0000and TIP4P/2005, are employed, exploring various system sizes by varying the\u0000number of molecules in the hydrate, liquid, and gas phases. The results reveal\u0000that finite-size effects play a crucial role in determining $T_3$. The study\u0000includes nine configurations with varying system sizes, demonstrating that\u0000smaller systems, particularly those leading to stoichiometric conditions and\u0000bubble formation, may yield inaccurate $T_3$ values. The emergence of methane\u0000bubbles within the liquid phase, observed in smaller configurations,\u0000significantly influences the behavior of the system and can lead to erroneous\u0000temperature estimations. Our findings reveal finite size effects on the\u0000calculation of the $T_3$ by direct coexistence simulations and clarify the\u0000system size convergence for both models, shedding light on discrepancies found\u0000in the literature. The results contribute to a deeper understanding of the\u0000phase equilibrium of gas hydrates and offer valuable information for future\u0000research in this field.","PeriodicalId":501146,"journal":{"name":"arXiv - PHYS - Soft Condensed Matter","volume":"26 1","pages":""},"PeriodicalIF":0.0,"publicationDate":"2024-08-04","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"141937375","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}