Soft Matter[JOURNAL]
Sun
200 papers
Volume and surface methods for microparticle traction force microscopy: a computational and experimental comparison.
Brauburger S, Kraus BK, Walther T … +4 more , Mense C, Abele T, Göpfrich K, Schwarz US
Soft Matter · 2026 Jun · PMID 42333875 · Full text
It is an essential element of mechanobiology to measure the forces of biological cells. In microparticle traction force microscopy, they are inferred from the deformation of elastic microparticles. Two complementary vari...
It is an essential element of mechanobiology to measure the forces of biological cells. In microparticle traction force microscopy, they are inferred from the deformation of elastic microparticles. Two complementary variants have been introduced before: the volume method, which reconstructs surface stresses from the displacements of fiducial markers embedded inside the particles, and the surface method, which infers stresses directly from the deformation of the particle surface. However, a systematic comparison of the two methods has been lacking. Here, we quantitatively compare both approaches using simulated traction fields representing biologically relevant loading scenarios. We find that the surface method consistently reconstructs traction profiles with substantially lower errors than the volume method, which suffers from displacement tracking and stress calculation at the surface. At high noise levels, however, the performance gap becomes smaller. To compare the performance of the two methods in a realistic experimental setting, we developed DNA-based hydrogel microparticles equipped with both fluorescent surface labels and embedded fluorescent nanoparticles, enabling the direct comparison of the two methods within the same system. Compression experiments produced traction profiles consistent with Hertzian contact mechanics and confirmed the trends observed in the simulations. We also show that despite large experimental deformations and strains (both up to 20 percent), linear elasticity theory should still be valid. While our computational workflow establishes a framework to apply both methods, our experimental workflow establishes DNA microparticles as versatile and biocompatible probes for measuring cellular forces.
Inertial forces and elastohydrodynamic interaction of spherical particles in wall-bounded sedimentation experiments at low .
Noichl I, Schönecker C
Eur Phys J E Soft Matter · 2026 Jun · PMID 42332213 · Full text
Unsteady, wall-bounded sedimentation of spheres at low particle Reynolds numbers, Re , under the influence of small elastic deformation was investigated experimentally. The complete kinematics of elastic and rigid spher...
Unsteady, wall-bounded sedimentation of spheres at low particle Reynolds numbers, Re , under the influence of small elastic deformation was investigated experimentally. The complete kinematics of elastic and rigid spheres sedimenting from rest at various initial distances from a rigid plane wall in a rectangular duct were measured. Several previously unrecognized phenomena arising from fluid inertia and superimposed elastohydrodynamic effects were identified and analyzed. Among these is an inertial wall attraction, whereby particles migrate toward the wall during the initial acceleration phase. After this initial phase, rigid spheres sedimenting at Re followed behavior consistent with classic wall-lift models, including approximately linear migration away from the wall. In contrast, at smaller Reynolds numbers, Re , both rigid and elastic spheres exhibited persistently unsteady sedimentation, characterized by deceleration despite increasing wall distance. These results enable the formulation of a conceptual framework that classifies near-wall sedimentation regimes according to particle Reynolds number and the position of boundaries relative to the Stokes length scale. For increasing deformability, the unsteady behavior was further modulated by nonlinearities. The observations suggest the presence of an elastohydrodynamic memory effect arising from the coupling of fluid inertial forces with particle deformability. The experimental findings are supported by computational fluid dynamics simulations that provide qualitative insight into the evolving flow field. Overall, the results demonstrate that classic assumptions commonly applied to particle sedimentation in creeping flows break down in the presence of nearby boundaries and reveal a counterintuitive trend: as the particle Reynolds number decreases, fluid inertia can play an increasingly important role in governing particle motion near walls. The proposed conceptual framework may therefore aid the interpretation of the near-wall dynamics of deformable microplastic particles, for which comparable material properties and flow regimes are encountered in environmental and wastewater flows.
Decoupling particle size and charge transport in PEDOT:PSS morphological inheritance of monomer emulsification.
Yin Y, Zhang K, Wei L … +5 more , Zhang X, Hong J, Liu Y, He M, Yu J
Soft Matter · 2026 Jun · PMID 42328823 · Publisher ↗
The intrinsic trade-off between colloidal processability and macroscopic electrical conductivity has long hindered the advancement of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) in precision flexi...
The intrinsic trade-off between colloidal processability and macroscopic electrical conductivity has long hindered the advancement of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) in precision flexible electronics. While pursuing nanoscale colloidal dispersions typically leads to a proliferation of grain boundaries that drastically degrade the material's electrical properties, we demonstrate that this trade-off can be decoupled at the level of polymerization kinetics. Herein, we propose a nanoreactor strategy leveraging the "morphological inheritance" of emulsified monomers. By modulating the pre-emulsification energy from mechanical stirring to high-pressure homogenization (HPH), we achieved a controlled, cross-scale reduction in colloidal particle size from 2911 nm down to 76 nm. Notably, despite the abundance of physical grain boundaries introduced by this miniaturization, the resulting HPH films maintain an exceptional electrical conductivity of 373 S cm, comparable to the 409 S cm observed in micrometer-scale systems, while achieving mirror-like surface flatness ( = 1.06 nm). Grazing-incidence wide-angle X-ray scattering (GIWAXS) reveals the underlying crystallization mechanism: nanoconfined templates generated by extreme cavitational shear force the PEDOT chains to overcome conformational disorder, adopting a highly extended and ordered arrangement. This confinement effect unexpectedly extends the crystal coherence length (CCL) to 12.35 Å. By enhancing charge delocalization within the crystalline domains, this microscopic ordering fundamentally compensates for the transport resistance induced by grain boundary accumulation. Furthermore, the HPH nanocolloids exhibit excellent fluid processing stability (viscosity of 12 mPa s), and their ultrahigh specific surface area endows the films with outstanding interfacial electrochemical capacitance. Ultimately, this work establishes a paradigm in which "microscopic ordering compensates for macroscopic defects," providing crucial physicochemical criteria for the rational design of high-performance conducting polymers.
Convective flow in coalesced droplets under a temperature difference for uniform distribution of microspheres in vertical contact-separation.
Bono S, Okai S, Weiss MW … +2 more , Stoeber B, Konishi S
Soft Matter · 2026 Jun · PMID 42324942 · Publisher ↗
We brought a water droplet and a droplet containing microspheres (MSs) into vertical contact and then investigated the transport of the MSs in the coalesced droplets under a temperature difference. We used optical cohere...
We brought a water droplet and a droplet containing microspheres (MSs) into vertical contact and then investigated the transport of the MSs in the coalesced droplets under a temperature difference. We used optical coherence tomography to obtain the trajectories of the MSs in the coalesced droplets. We also observed a convective flow in the coalesced droplets after increasing the temperature of the lower substrate. Using wetting pattern substrates, we can separate the coalesced droplet under this temperature difference into two droplets and assessed the distribution of the MSs in the top and bottom droplets. The downward flow at the center of coalesced droplets and the upward flow at the liquid-air interface under a temperature difference suggest that the convective flow is driven by the Marangoni effect. The Marangoni convective flow in the coalesced droplet resulted in equally distributed MSs in the two droplets after separation.
Semi-analytical modeling and simulation of human red blood cell deformation under non-linear strain.
Bhabhor GD, Bhatt R, Anand A … +1 more , Lad KN
Eur Phys J E Soft Matter · 2026 Jun · PMID 42323474 · Publisher ↗
The study of red blood cell (RBC) deformability remains an active area of research due to its linkage to health and normal physiological functions of RBCs in the circulatory system. RBC deformability is commonly analyzed...
The study of red blood cell (RBC) deformability remains an active area of research due to its linkage to health and normal physiological functions of RBCs in the circulatory system. RBC deformability is commonly analyzed using force-based experimental and theoretical approaches. Complementary to these methods, geometric descriptions of RBC shape provide insight into curvature redistribution and bending energetics independent of explicit constitutive modeling. In this work, we present a semi-analytical, surface-based framework to study RBC deformation under axial stretching by imposing an affine geometric strain on a triangulated biconcave membrane, with volume conservation enforced throughout. Linear strain and a non-linear Hencky-type strain are compared. While linear strain reproduces experimental trends only for small deformations, nonlinear strain yields global shape variations-axial and transverse diameters and elongation index-that are consistent with reported optical tweezers data over a wide deformation range. The surface formulation enables detailed mapping of Gaussian and mean curvature redistribution during elongation. Evaluation of the Helfrich bending energy, including spontaneous curvature treated as an effective geometric parameter, yields energetically consistent values when non-linear strain is employed. Analysis of the curvature-bending energy of the RBC subjected to axial stretching suggests that nonlinear strain and spontaneous curvature should be the primary considerations to ensure that the membrane bending energy remains within the range of 10-100 eV during RBC biomechanical deformation. The framework does not resolve force balance or membrane constitutive behavior, but provides a computationally efficient geometric surrogate linking imposed deformation to curvature and bending energetics.
Avalanches in the random organization model with long-range interactions.
Jocteur T, Martens K, Mari R … +1 more , Bertin E
Eur Phys J E Soft Matter · 2026 Jun · PMID 42322493 · Publisher ↗
Oscillatory sheared suspensions, when observed stroboscopically, exhibit a reversible-irreversible transition as a function of the strain amplitude, which is an absorbing phase transition, separating diffusive states on...
Oscillatory sheared suspensions, when observed stroboscopically, exhibit a reversible-irreversible transition as a function of the strain amplitude, which is an absorbing phase transition, separating diffusive states on the irreversible side from absorbing states on the reversible side. So far studies of this transition focused on global quantities, e.g., quantifying the irreversibility on the one side of the transition or the time to reach a reversible state on the other side. Here, inspired by depinning-type transitions, we focus on intermittent dynamics close to the transition. We perform simulations of a modified Random Organization Model (ROM), a minimal particle model which we recently adapted to take into account the generic presence of long-range interactions mediated by the fluid, taking the power-law decay exponent as an additional control parameter of the model. We show that at the absorbing phase transition, this model displays power-law distributed avalanches. We characterize the avalanche statistics in terms of avalanche size, duration and number of particles involved, and we determine the associated exponents. By varying the exponent , the fractal dimension of avalanches crosses space dimension d, inducing a qualitative change of the spatial structure of avalanches, from compact avalanches when interactions have a short range, to sparse avalanches when interactions are long-ranged. Finally, we characterize the clusters within the avalanches, which we also find to be power-law distributed.
Mean first passage time of chiral active Brownian particles.
Iyaniwura SA, Qiu M, Peng Z
Soft Matter · 2026 Jun · PMID 42318759 · Publisher ↗
Chiral active Brownian particles (CABPs) are self-propelled agents with intrinsic rotational dynamics, giving rise to circular trajectories commonly observed in biological and synthetic microswimmers. Understanding how C...
Chiral active Brownian particles (CABPs) are self-propelled agents with intrinsic rotational dynamics, giving rise to circular trajectories commonly observed in biological and synthetic microswimmers. Understanding how CABPs explore confined environments and locate targets is crucial for characterizing transport, search efficiency, and reaction processes in physical and biological systems. We study the escape dynamics of CABPs from one- and two-dimensional confined domains. In one dimension, we consider intervals with either two absorbing boundaries or a reflecting boundary on one side and an absorbing boundary on the other, and derive closed-form asymptotic solutions in the high-chirality regime, revealing the quantitative scaling of the mean first passage time (MFPT) as a function of particle rotation speed (chirality). In two dimensions, we analyze escape from a disk containing one absorbing arc or two symmetric absorbing arcs. By numerically solving the governing partial differential equations, we compute the MFPT for CABPs to escape the domains as a function of the particle's initial orientation, self-propulsion speed, angular velocity, and domain geometry. Our results show that, depending on the parameters and geometry, the MFPT can exhibit non-monotonic behavior as a function of chirality. A minimal escape time exists at an intermediate value of chirality, where the rotational time scale balances the active swimming time scale, redirecting a particle towards the exit which would otherwise be blocked due to unfavorable initial orientation. Our work offers a comprehensive characterization of CABP escape dynamics in canonical confinements and identifies chirality as a key control parameter for transport and search in confined physical and biological systems.
Pathways for fast and slow fusion of nanovesicles without membrane rupture.
Różycki B, Ghosh R, Lipowsky R
Soft Matter · 2026 Jun · PMID 42318752 · Publisher ↗
Eukaryotic cells continuously remodel their membrane architecture by fusion processes, which are initiated by the adhesion of two membranes and eventually lead to a single membrane with a membrane neck or fusion pore. Th...
Eukaryotic cells continuously remodel their membrane architecture by fusion processes, which are initiated by the adhesion of two membranes and eventually lead to a single membrane with a membrane neck or fusion pore. The fusion of cellular membranes involves membrane proteins but the fusion of biomimetic membranes such as lipid bilayers can be induced by bilayer tension even in the absence of proteins. Tension-induced fusion competes however with membrane rupture, which tends to impair the fusion process. Here, we show by molecular dynamics simulations that nanovesicles enclosed by tensionless and asymmetric bilayers can undergo fusion without rupture and that these fusion processes follow two distinct pathways, a slow and a fast one. Fast fusion starts immediately after an initial point contact between the two vesicles has been established whereas slow fusion occurs only after the vesicles have formed a spatially extended contact area. The two pathways are controlled by the stress asymmetry between the two bilayer leaflets or, equivalently, by the resulting transbilayer torque. Our simulation results have important consequences for the free energy landscapes corresponding to fast and slow fusion of nanovesicles, for experimental studies elucidating these fusion pathways, and for protein-mediated fusion of cellular membranes.
Multiscale structural-rheological mapping of cancer spheroids during maturation.
Gnanachandran K, Berardi M, Pyka-Fościak G … +3 more , Pabijan J, Akca BI, Lekka M
Soft Matter · 2026 Jun · PMID 42318645 · Publisher ↗
Recent studies highlight the central role of mechanical properties in understanding solid tumor biology, progression and therapeutic response. However, the mechanical characterization of 3D tumor models such as cancer s...
Recent studies highlight the central role of mechanical properties in understanding solid tumor biology, progression and therapeutic response. However, the mechanical characterization of 3D tumor models such as cancer spheroids remains incomplete. Current experimental and modeling frameworks often overlook their spatially varying and multiscale features, limiting a unified understanding of how spheroid structure governs mechanical response. Here, we combine atomic force microscopy and hydraulic force spectroscopy to perform multiscale microrheology of cancer spheroids, probing their mechanical evolution at both single-cell and multicellular levels over time. We identify a characteristic power-law behavior whose parameters capture contributions from intra- and inter-cellular mechanics, and we relate these parameters to structural organization and its temporal progression. This structure-rheology framework provides a mechanistic view of spheroid maturation and establishes a platform for future studies on tumor mechanobiology, therapy response, and engineered microenvironments.
Computational study of multicharged cyclodextrin derivatives with deep cavities for high-affinity host-guest recognition.
Cheng B, Yao Q, Ren F … +1 more , Shen D
Soft Matter · 2026 Jun · PMID 42317166 · Publisher ↗
Cyclodextrin (CD) derivatives bearing multicharged side chains exhibit enhanced host-guest binding, with higher selectivity and affinity compared with natural CDs, due to their deep cavities, polar binding sites and elec...
Cyclodextrin (CD) derivatives bearing multicharged side chains exhibit enhanced host-guest binding, with higher selectivity and affinity compared with natural CDs, due to their deep cavities, polar binding sites and electrostatic interactions. To further understand the relationship between their structures and molecular recognition, molecular dynamics simulations were performed on a series of multicharged CD hosts with per-6-substituted side chains and their oppositely charged guests. In the case of rocuronium bromide (ROC) as the guest, umbrella sampling identified glutamic acid-substituted γ-CD as the host, exhibiting the strongest host-guest binding, with a free energy of -103.1 kJ mol, followed in descending order by aspartic acid-substituted γ-CD, glycine-substituted γ-CD, succinic acid-substituted γ-CD, sugammadex, and adamgammadex. Meanwhile, molecular mechanics Poisson-Boltzmann surface area (MM-PBSA) analysis showed similar rankings, suggesting that electrostatic interactions play a dominant role in binding, while hydrophobic interactions, van der Waals forces, hydrogen bonding, and host-guest geometric complementarity act synergistically to stabilize the complexes. In addition, edrophonium@succinic acid-substituted β-CD and simvastatin@ammonium-substituted β-CD complexes were also evaluated, exhibiting binding free energies of -98.42 and -59.77 kJ mol, respectively. These findings provide mechanistic insights into CD derivative recognition and offer theoretical guidance for the rational design and experimental screening of high-affinity hosts.
Phase dependence of effective surface diffusivity in surfactant monolayers dilatated far from equilibrium.
Mucci TJ, Adam JA, Hirsa AH
Soft Matter · 2026 Jun · PMID 42317110 · Publisher ↗
Modeling the flow of insoluble surfactant monolayers undergoing rapid expansion and compression remains a long-standing challenge in hydrodynamics. In a recent letter, compressible flow of a DPPC monolayer in the coexist...
Modeling the flow of insoluble surfactant monolayers undergoing rapid expansion and compression remains a long-standing challenge in hydrodynamics. In a recent letter, compressible flow of a DPPC monolayer in the coexisting liquid-expanded/liquid-condensed phase was accurately described with Newtonian and Fickian modeling by using large effective surface diffusivity, many orders of magnitude larger than the monolayer's equilibrium diffusivity, along with finite surface dilatational viscosity. The large effective diffusivity was attributed to monolayer phase coexistence. Here, the applicability of large effective diffusivity is investigated through flow measurements of DPPC and vitamin K1 monolayers over a wide range of concentrations, from gas phase to collapse. Effective surface diffusivity and surface viscosity were determined by fitting numerical simulations, Navier-Stokes bulk flow coupled to a Boussinesq-Scriven interface with monolayer advection-diffusion, to spatio-temporal surface velocity measurements. Results reveal that large effective surface diffusivity is not limited to coexisting phases, producing good fits for all monolayers outside gaseous phases. The failure of this theoretical framework when applied to gaseous monolayers is likely due to their extreme compressibility. The extreme diffusivity in non-gaseous phases motivates future exploration of non-Newtonian and non-Fickian interfacial models.
Effects of surface roughness on droplet impact dynamics.
Ghossein J, Kendurkar C, Boreyko JB … +1 more , Coutier-Delgosha O
Soft Matter · 2026 Jul · PMID 42314022 · Publisher ↗
Past investigations into droplet impact dynamics have mostly used either relatively smooth substrates or air-trapping superhydrophobic textures. For this reason, existing models for predicting the maximum spreading ratio...
Past investigations into droplet impact dynamics have mostly used either relatively smooth substrates or air-trapping superhydrophobic textures. For this reason, existing models for predicting the maximum spreading ratio of impacting droplets ( = /) are unable to capture the influence of surface roughness. In this study, we investigate the influence of roughness and substrate wettability on the dynamics of water impacting at Weber numbers where splashing is minimal, with a specific focus on the maximal spreading diameter of Wenzel droplets. The surface mean roughness amplitude, , was varied widely by laser etching substrates comprised of either glass ( = 0.012-22.49 µm), PETG ( = 1.18-55.04 µm), or aluminum ( = 2.21-58.31 µm). The surface wettability ranged from strongly hydrophilic to weakly hydrophobic and depended on the choice of substrate material, the extent of surface roughness, and the roughness-dependent modification of the intrinsic wettability due to the laser or hydrocarbon adsorption. We develop a new energy model for predicting for both elastic (We < 30) and inelastic (We ≥ 30) droplet impact regimes, where surface energy and viscous dissipation terms are modified to incorporate surface roughness effects. We show that the universality of existing (roughness-independent) models for becomes incomplete for roughness ratios of ≳ 2, whereas our roughness-dependent model has excellent agreement across all values. By explicitly incorporating surface roughness into the energy balance, we extend the predictive capability of droplet spreading models to achieve an extended predictive framework for water-droplet spreading on rough substrates.
Vector nematodynamics with symmetry-driven energy exchange.
Pismen LM
Eur Phys J E Soft Matter · 2026 Jun · PMID 42307657 · Full text
We review inadequacy of existing nematodynamic theories based on Onsager's near-equilibrium relations and suggest a novel way of establishing relations between nematic orientation and flow, based on the local symmetry be...
We review inadequacy of existing nematodynamic theories based on Onsager's near-equilibrium relations and suggest a novel way of establishing relations between nematic orientation and flow, based on the local symmetry between simultaneous rotation of nematic alignment and flow, which establishes energy and momentum exchange between the two without reducing the problem to near-equilibrium conditions. This approach, applied in the framework of the vector-based theory with a variable modulus, involves antisymmetric interactions between nematic alignment and flow. It avoids spurious instabilities in the absence of active inputs and elucidates their cause.
Transport properties of active particles moving on adjustable networks.
Oropesa WGC, de Castro P, Löwen H … +1 more , Liarte DB
Soft Matter · 2026 Jun · PMID 42307584 · Publisher ↗
Active adaptive matter has attracted considerable interest due to its rich, largely unexplained dynamics and its relevance to a wide range of synthetic and biological materials. An important subclass of such systems cons...
Active adaptive matter has attracted considerable interest due to its rich, largely unexplained dynamics and its relevance to a wide range of synthetic and biological materials. An important subclass of such systems consists of active particles that can remodel the network in which they move. Here, we introduce a minimal yet versatile model of active particles moving on an adjustable network. In this model, particles undergo discrete run-and-tumble motion along the links of a triangular lattice and leave behind a trail of temporarily blocked links. These closed links cannot be traversed by other particles and reopen only after a characteristic healing time. The resulting trail-mediated blocking mechanism is fundamentally distinct from more familiar interactions such as excluded-volume effects. In the high-persistence limit, we find a qualitative contrast between the two mechanisms: while steric blocking leads to reduced diffusivity with increasing persistence, trail-induced blocking causes diffusivity to increase monotonically. We characterize this fundamental difference and the unexpected transport properties that arise when both blocking mechanisms are present, and discuss potential applications.
Membrane tubulation by spherical nanoparticles: effect of lateral tension.
Weikl TR
Soft Matter · 2026 Jul · PMID 42307120 · Publisher ↗
Adhesion of spherical nanoparticles or virus-like particles to membranes can lead to membrane tubules in which linear chains of adhering particles are cooperatively wrapped by the membrane. This cooperative wrapping of s...
Adhesion of spherical nanoparticles or virus-like particles to membranes can lead to membrane tubules in which linear chains of adhering particles are cooperatively wrapped by the membrane. This cooperative wrapping of spherical particles in tubules is energetically favourable compared to the individual wrapping of the particles because of a favourable interplay of membrane bending and particle adhesion energies in the membrane necks that connect the particles to the neighbouring particles in the tubule. In this article, we investigate how the energy gain for the cooperative wrapping of spherical nanoparticles in tubules is affected by lateral membrane tension as well as by the membrane thickness, which limits the radius of the membrane necks between the particles. We find that membrane tension tends to stabilize weakly undulated tubule shapes at intermediate particle adhesion energies, but only moderately affects the energy gain of cooperative wrapping at larger adhesion energies. For tight membrane necks limited by the membrane thickness, however, the energy gain of cooperative wrapping can vanish if the range of the particle adhesion potential is too small to still lead to a favourable interplay of bending and adhesion energies in these necks.
Role of hydration effects in driving ion binding to polyelectrolyte brushes and chains: a perspective.
Ishraaq R, Das S
Soft Matter · 2026 Jul · PMID 42301117 · Publisher ↗
Polyelectrolyte (PE) chains and PE brushes are often characterized by the nature of the counterions that bind to them, as such binding regulates different properties of the chains and brushes. However, despite extensive...
Polyelectrolyte (PE) chains and PE brushes are often characterized by the nature of the counterions that bind to them, as such binding regulates different properties of the chains and brushes. However, despite extensive research probing the properties of PE chains and brushes in the presence of a wide variety of counterions, the understanding of what would be the relative strength of binding of a specific type of counterion to a specific type of PE chain/brush remains elusive. In this perspective article, driven by our recent all-atom molecular dynamics (MD) simulations, we propose the following hypothesis that aims to fill this void: more chaotropic (kosmotropic) ions-those that disrupt (preserve) the surrounding water structure-tend to bind more strongly to polyelectrolyte (PE) chains and PE brushes bearing hydrophobic (hydrophilic) functional groups due to solvent mediated interactions. Therefore, our hypothesis accounts for the effect of hydration on ion binding to the PE brushes and chains: ions bind more favorably to PE chains/brushes having functional groups that impart a similar effect towards water. Subsequently, we discuss experimental and simulation results on counterion binding to PE chains and brushes from a large number of studies and establish the validity of our hypothesis by testing it against the findings of these studies. Finally, we identify the possible applications of our proposed hypothesis (in terms of designing systems that involve PE brushes and chains) and machine learning and density functional theory calculations that can further strengthen our understanding of the PE-counterion binding events.
Superlubricity in granular shear flows under external vibrations.
Berzi D, Gianetti MM, Vescovi D
Soft Matter · 2026 Jun · PMID 42301116 · Publisher ↗
We investigate the use of external vibrations to reduce macroscopic friction in pressure-imposed granular flows sheared between bumpy planes, in the absence of gravity, using the discrete element method. We observe that...
We investigate the use of external vibrations to reduce macroscopic friction in pressure-imposed granular flows sheared between bumpy planes, in the absence of gravity, using the discrete element method. We observe that the system becomes superlubric, , the macroscopic friction is less than 0.01, if one of the bumpy planes oscillates with a sufficiently large velocity amplitude. We quantify the reduction in the energy dissipated by the system through the work of the shear stress induced by the reduction in macroscopic friction and the external energy required to make the bumpy plane oscillate for different combinations of amplitude and frequency, and imposed pressure. We propose a phase diagram and criteria in terms of imposed pressure and velocity amplitude of oscillations to predict the resistance to shear.
measurements of fascia lata effective mechanics combined to a memory fiber-recruitment-viscoelastic modeling approach.
Germain F, Gibaud T
Soft Matter · 2026 Jun · PMID 42301115 · Publisher ↗
The fascia lata plays a central role in force transmission and body mechanics, yet its mechanical behavior remains poorly characterized. Existing approaches-shear wave elastography and direct force measurements alike-sh...
The fascia lata plays a central role in force transmission and body mechanics, yet its mechanical behavior remains poorly characterized. Existing approaches-shear wave elastography and direct force measurements alike-share a fundamental limitation: none simultaneously captures both the elastic and viscous components of fascial mechanics within a single experiment. The primary aim of this study is therefore to develop an experimental and modeling framework that enables the reproducible measurement of the effective viscoelastic properties of the fascia lata . To this end, we combine controlled ramp-relaxation experiments on the human fascia lata with a constitutive model that integrates fiber recruitment and dual-timescale viscoelastic relaxation. We emphasize that this is an effective model: rather than describing intrinsic local material properties, it characterizes the mechanical response of the fascia lata complex including its coupling to the hip-thigh musculoskeletal system under controlled loading conditions. The model captures both the nonlinear stiffening during elongation and the dual decay of force during relaxation, using a minimal set of physically interpretable parameters. Repeated trials demonstrate good reproducibility, with parameter variability within 10%. Our results support the view that fascia lata behaves as a hierarchical, hydrated composite whose macroscopic mechanical response emerges from the coupled effects of collagen alignment, matrix viscoelasticity, and fluid flow. This work provides a quantitative foundation for future investigations into how training, rehabilitation, or aging influence the evolution of fascial mechanical properties.
How tip geometry controls fracture in ductile polymer glasses and brittle elastomers.
Siavoshani AY, Fan Z, Wang SQ
Soft Matter · 2026 Jun · PMID 42301099 · Publisher ↗
Based on spatially-temporally resolved polarized optical microscopy (str-POM) measurements, we studied the fracture behavior of ductile and brittle glassy polymers as well as highly crosslinked rubbers to draw the follow...
Based on spatially-temporally resolved polarized optical microscopy (str-POM) measurements, we studied the fracture behavior of ductile and brittle glassy polymers as well as highly crosslinked rubbers to draw the following conclusions: (1) there is no tip plasticity below a threshold load in ductile plastics such as polyethylene terephthalate. (2) In ductile polymer glasses, before tip yielding at a common tip stress, the remote load scales with notch length as , in agreement with the Inglis solution. (3) A finite stress saturation zone is observed in elastomers at loading levels even well below fatigue threshold due to significant crack tip blunting. (4) When the thickness is small enough for the plane stress condition to prevail at crack tip, in double-edge notch tension (DENT) for both ductile glassy polymers and rubbers that is characterized by ligament length , nominal strain in the ligament is defined by = /, where is tensile displacement; tensile force increases linearly with independent of ; tip stress increases linearly with the far-field (∼). By demonstrating stress concentration at the crack tip in DENT in elastic materials and characterizing crack propagation in ductile polymers, the present study fills the missing gap in our understanding of fracture behavior in a wider range of polymeric materials. The acquired knowledge may be useful to guide specific design for packaging materials.
Viscous solvent embrittles long-chain polymer networks.
Kim H, Costa D, Kim J
Soft Matter · 2026 Jul · PMID 42300960 · Publisher ↗
The toughness of polymer networks is commonly attributed to energy dissipation arising from viscoelastic deformation, leading to a design principle: higher viscosity increases toughness. Here, we show that this relations...
The toughness of polymer networks is commonly attributed to energy dissipation arising from viscoelastic deformation, leading to a design principle: higher viscosity increases toughness. Here, we show that this relationship can be reversed when polymer chains are sufficiently long. To demonstrate, we prepare polyacrylamide hydrogels with identical network structures, fully dry them, and reswell them in glycerol-water mixtures to the same polymer content, thereby varying the solvent viscosity by three orders of magnitude while preserving the network structure. Although the mechanical response under homogeneous deformation does not change significantly, toughness measured by pure shear and trouser tests markedly decreases with solvent viscosity. In particular, toughness collapses onto a master curve when plotted as a function of the product of viscosity and velocity, with a scaling relation consistent with the shear-lag model. Stick-slip occurs under conditions for which the slope of the master curve is negative, corroborating the presence of a master curve. We attribute this embrittlement to limited transmission of tension along polymer chains at the crack tip due to solvent viscosity, which reduces the fraction of load-bearing chain segments at rupture. In contrast, in short-chain networks, the tension can readily be transmitted to the entire polymer chains, resulting in a non-negative slope. At sufficiently high viscosity and velocity, energy dissipation by viscosity dominates the tension transmission, resulting in a positive slope regardless of the chain length. These results advance the understanding of toughness dynamics through tension transmission and viscous dissipation.
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