Soft Matter[JOURNAL]
Sun
200 papers
Quantitative prediction of oil-water interfacial tension in surfactant systems using dissipative particle dynamics.
Hendrikse RL, Amador C, Davies M … +1 more , Wilson MR
Soft Matter · 2026 May · PMID 42011122 · Publisher ↗
We present a dissipative particle dynamics (DPD) model for surfactants at oil-water interfaces, parametrised directly against experimental data. The model is applied to pure and mixed systems of ionic and nonionic surfac...
We present a dissipative particle dynamics (DPD) model for surfactants at oil-water interfaces, parametrised directly against experimental data. The model is applied to pure and mixed systems of ionic and nonionic surfactants, including sodium dodecyl sulfate (SDS), dodecyldimethylamine oxide (DDAO), and polyoxyethylene alkyl ethers (CE). Our simulations reveal that exceeding the maximum interfacial packing density can lead to the spontaneous production of micelles from the interfacial surfactant layer into the bulk. This behaviour, together with our parametrisation scheme, enables quantitative prediction of interfacial tension as a function of surface concentration in excellent agreement with experiment. In addition, the model provides access to other interfacial properties such as maximum surface coverage and interfacial monolayer thickness. Moreover, we show that the model can be used to investigate synergistic effects in mixed surfactant systems, where combinations of surfactants yield lower interfacial tensions than either component alone. In particular, simulations of DDAO and SDS systems demonstrate a lower interfacial tension than the corresponding pure surfactants. Utilising these results, we propose that these synergistic effects result from a balance between the intrinsic ability of a surfactant molecule to lower the IFT and its achievable maximum packing at the interface.
Morphological transitions in the crystallization-driven self-assembly of narrowly distributed π-conjugated triblock copolymers.
Bin Huang, Tian D, Liu Z … +3 more , Deng Y, Wang G, Hu A
Soft Matter · 2026 May · PMID 42011107 · Publisher ↗
Crystallization-driven self-assembly (CDSA) of π-conjugated block copolymers enables precise control over micellar morphology. However, generalizable strategies for preparing π-conjugated polymers with narrow dispersity...
Crystallization-driven self-assembly (CDSA) of π-conjugated block copolymers enables precise control over micellar morphology. However, generalizable strategies for preparing π-conjugated polymers with narrow dispersity ( < 1.3) to ensure reproducible self-assembly remain scarce. Herein, we report ABA triblock copolymers consisting of a crystalline poly(-phenylene) core flanked by two pH-responsive poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA) coronae, synthesized controlled step-growth polymerization and atom-transfer radical polymerization. In tetrahydrofuran-water mixtures, these copolymers undergo CDSA to form micelles exhibiting a progressive morphological evolution, from ribbons to fibers and ultimately to spherical aggregates, as the corona length increases, in accordance with a monotonic rise in interfacial curvature. Notably, the PDMAEMA coronae confer pronounced pH responsiveness. Under acidic conditions, CDSA is suppressed and curvature enhanced transitions toward spherical geometries are driven by electrostatic repulsion among protonated coronal segments. In contrast, alkaline media promote hydrophobic clustering of deprotonated chains, inducing ribbon stacking and longitudinal elongation of the fibrous assemblies.
Thermal dehydration of swollen heterogeneous soft materials.
Curatolo M, Tomassetti G, van der Sman R … +1 more , Teresi L
Soft Matter · 2026 May · PMID 42008291 · Publisher ↗
The dehydration of bi-layer soft materials under temperature variations is a key process in applications such as biomedical devices and responsive hydrogels. This study develops a multiphysics model to investigate the co...
The dehydration of bi-layer soft materials under temperature variations is a key process in applications such as biomedical devices and responsive hydrogels. This study develops a multiphysics model to investigate the coupled thermo-hydro-mechanical behavior of bi-domain materials. We present the governing equations capturing heat transfer, moisture diffusion, and mechanical deformation across two distinct material domains. Numerical simulations reveal that temperature gradients induce differential dehydration rates, leading to localized stresses and domain-specific shrinkage. Key findings include critical temperature thresholds, wet-bulb effect and the role of domain interface properties in material stability. These results provide insights into controlling the shape morphing of thermally responsive soft materials tailored dehydration conditions.
Diffusion of rod-like particles in complex fluids.
Sokołowski W, Jamil H, Makuch K
Soft Matter · 2026 Jun · PMID 41996302 · Publisher ↗
Diffusion of particles in complex fluids and gels is difficult to describe and often lies beyond the scope of the classical Stokes-Einstein relation. One of the main lines of research over the past few decades has sought...
Diffusion of particles in complex fluids and gels is difficult to describe and often lies beyond the scope of the classical Stokes-Einstein relation. One of the main lines of research over the past few decades has sought to relate diffusivity to a fundamental dissipative property of the fluid: the wave-vector-dependent shear viscosity function. Here, we use linear response theory to extend this viscosity function framework to rod-like particles. Using a dimer (two-bead particle) as a minimal rod-like probe, we derive explicit expressions for its diffusion coefficients parallel and perpendicular to its axis in terms of the viscosity function. We show that this description captures the full range of behaviors, from nearly isotropic diffusion of the rod-like probe to highly anisotropic, reptation-like motion. The method is based on a microscopic statistical-mechanical treatment of the Smoluchowski dynamics, yet leads to simple final formulas, providing a practical tool for interpreting diffusion experiments on rod-like tracers in complex fluids. We also clarify the limitations of this approach, emphasizing that the present formulation is primarily suited to complex liquids like polymer solutions, and only indirectly applicable to gels.
Thermal and solutal capillary effects in tear film dynamics.
Kumawat TC, Shah K
Eur Phys J E Soft Matter · 2026 Apr · PMID 41995778 · Publisher ↗
An analytical and numerical study is carried out for the stability of a thin tear film considering a single-layered model. The mass, momentum, and energy equations are simplified under the lubrication approximation to ob...
An analytical and numerical study is carried out for the stability of a thin tear film considering a single-layered model. The mass, momentum, and energy equations are simplified under the lubrication approximation to obtain nonlinear partial differential spatiotemporal evolution equations for the film height and surfactant concentration. These evolution equations involve various physical mechanisms such as thermo- and solutocapillary stresses, van der Waals forces, surface tension forces, and slip at the corneal surface. Linear stability analysis reveals that solutocapillary stresses enhance the stability of the tear film by driving fluid from thicker to thinner regions. The thermocapillary stresses are found to enhance the instability, where the fluid is driven from a thinner (low surface tension) region to a thicker (high surface tension) region. Convective cooling due to cold wind flow also affects the growth rate of perturbations, with higher convection leading to a higher growth rate. The solutocapillary stresses dominate over the thermocapillary stresses beyond a certain critical value of the solutal Marangoni number. This critical threshold decreases with increasing Péclet number, indicating that the influence of solutocapillary effects becomes more pronounced under stronger advective transport. Numerical computations are carried out and show that the nonlinear stability results are in good agreement with those obtained from linear stability analysis. Furthermore, the computations reveal that the rupture time decreases with increasing thermal Marangoni number and slip coefficient, whereas it increases with the solutal Marangoni number.
Effective interfacial tension of a film solidified during the collision of a molten wax droplet with a water surface.
Kitsunezaki S, Nakashioya R, Uemura C … +1 more , Nakahara A
Soft Matter · 2026 May · PMID 41995226 · Publisher ↗
We investigated collision processes of droplets of paraffin wax melt with a water surface. We found that when the water temperature is significantly lower than the melting temperature of the wax, a liquid droplet solidif...
We investigated collision processes of droplets of paraffin wax melt with a water surface. We found that when the water temperature is significantly lower than the melting temperature of the wax, a liquid droplet solidifies in the vicinity of the interface between the wax and water, and the solidified wax left on the water surface after collision exhibits diverse morphologies, including irregularly breaking films and petal-like films. Experimental results and rheological measurements indicate that at large falling distances and relatively high water temperatures, the wax deforms as a plastic fluid and expands in the form of a hemispherical sheet along with the water surface, forming a cavity. Under such conditions, a thin solidified film created at the interface gives an effective interfacial tension to the interface and suppresses its expansion. We derived the time evolution equations of the size and the thickness of a solidified film. These equations indicate that the effective interfacial tension is approximately determined by the film thickness and the yield stress of the wax.
Electro-magneto-kinetic thermo-fluid-structure interactions of viscoelastic electrolytes through soft micro-confinements.
Roy A, Dhar P
Soft Matter · 2026 Apr · PMID 41995144 · Publisher ↗
A coupled electro-magneto-hydrodynamic (EMHD) framework for a viscoelastic electrolyte (of Phan-Thien-Tanner (PTT) fluid rheology) flowing through a compliant micro-confinement with linearly elastic walls is developed. T...
A coupled electro-magneto-hydrodynamic (EMHD) framework for a viscoelastic electrolyte (of Phan-Thien-Tanner (PTT) fluid rheology) flowing through a compliant micro-confinement with linearly elastic walls is developed. The flow is driven by a combination of an imposed pressure gradient and externally applied electric and magnetic fields. Closed-form perturbation solutions are obtained for the velocity, pressure, wall deformation, and temperature. Fluid-structure interactions (FSI) are examined against four parameters: Debye-Huckel parameter (), Weissenberg number (Wi), Hartmann number (Ha), and electrical Reynolds number (). We show that favourable pressure gradients drive wall contractions towards a converging channel, while adverse gradients cause wall expansion to a diverging geometry. Observations also show that reduces the pressure requirement through electroosmotic pumping; Wi induces shear-thinning that flattens velocity profiles; Ha has a dual effect - assistive at low Ha and resistive at higher Ha due to Lorentz drag; and is consistently assistive, lowering the required pressure drop and enhancing near-wall transport. Thermal behaviour is characterized using three parameters-the Biot number (Bi), the Peclet number (Pe), and the wall-to-fluid conductivity ratio (): higher Bi improves cooling wall-environment exchange, larger Pe increases axial thermal advection and raises fluid temperature, and higher facilitates heat removal and limits thermal buildup. Collectively, the insights provide a systematic approach for regulating hydrodynamic resistance and thermal loading in deformable EMHD microsystems, with potential applications in bio-lab-on-chip technologies and microscale thermal management platforms.
Adhesive tape loops.
Suryanarayanan K, Croll AB, Singh H
Soft Matter · 2026 Apr · PMID 41989840 · Publisher ↗
We present an experimental and theoretical study of the mechanics of an adhesive tape loop, formed by bending a straight rectangular strip with adhesive properties, prescribing an overlap between the two ends. For a give...
We present an experimental and theoretical study of the mechanics of an adhesive tape loop, formed by bending a straight rectangular strip with adhesive properties, prescribing an overlap between the two ends. For a given combination of the adhesive strength and the extent of the overlap, the loop may unravel, it may stay in equilibrium, or open up quasi-statically to settle into an equilibrium with a smaller overlap. We define the state space of an adhesive tape loop with two parameters: a non-dimensional adhesion strength and the extent of overlap normalized by the total length of the loop. We conduct experiments with adhesive tape loops fabricated out of sheets of polydimethylsiloxane (PDMS) and record their states. We rationalize the experimental observations using a simple scaling argument, followed by a detailed theoretical model based on Kirchhoff rod theory. The predictions made by the theoretical model, namely the shape of the loops and the states corresponding to equilibrium, show good agreement with the experimental data. Our model may potentially be used to deduce the strength of self-adhesion in sticky soft materials by simply measuring the smallest overlap needed to maintain a tape loop in equilibrium.
Microscopic measurement of the local deformation field establishes the mechanistic origin of the fatigue threshold for soft brittle materials.
Altuntas U, Li C, Kolinski JM
Soft Matter · 2026 May · PMID 41989124 · Full text
Fatigue fracture, whereby a material fails only under repeated loading cycles, depends strongly on load magnitude. In most materials, the applied load must exceed a threshold value - the fatigue threshold - for the crack...
Fatigue fracture, whereby a material fails only under repeated loading cycles, depends strongly on load magnitude. In most materials, the applied load must exceed a threshold value - the fatigue threshold - for the crack to advance each cycle. While recent studies clarify the regimes of soft polymer response to cyclic loading, the interplay between crack tip strain fields, irreversible deformation, and energy dissipation remains unclear. Here, we subject polyacrylamide hydrogels and polydimethylsiloxane (PDMS) elastomers to controlled cyclic loading, while directly resolving crack tip strain fields with particle tracking microscopy. An irreversible deformation zone emerges at the crack tip with a load-amplitude dependent structure. Below the fatigue threshold, the zone is compressive, and progressively accumulates without crack advance; this demonstrates that sub-threshold deformation is not fully reversible. Above threshold, a tensile plastic zone grows and co-propagates with the crack tip. Crack tip opening displacement (CTOD) measurements of the energy release rate show that the applied strain energy evolves with cycle count under constant stretch amplitude loading. Below threshold, remains nearly constant; above threshold, expansion of the tensile plastic zone modifies the CTOD geometry, producing a measurable decrease in . Consistent across both material systems in the brittle limit, these results suggest that irreversible deformation-shielding the crack below threshold and governing growth rate above it-may be a general hallmark of soft brittle material fatigue. These findings open pathways toward rational design of fatigue-resistant hydrogels and elastomers for soft robotics, biomedical devices, and stretchable electronics.
Hierarchical Bayesian constitutive model selection for high-strain-rate soft material characterization.
Sanchez V, Remillard S, Abeid BA … +5 more , Bu L, Bryngelson SH, Yang J, Estrada JB, Rodriguez M
Soft Matter · 2026 May · PMID 41982135 · Publisher ↗
The high-fidelity characterization of soft, tissue-like materials under ultra-high-strain-rate conditions is critical in engineering and medicine. Still, it remains challenging due to limited optical access, sensitivity...
The high-fidelity characterization of soft, tissue-like materials under ultra-high-strain-rate conditions is critical in engineering and medicine. Still, it remains challenging due to limited optical access, sensitivity to initial conditions, and experimental variability. Microcavitation techniques (, laser-induced microcavitation) have emerged as a viable method for determining the mechanical properties of soft materials in the ultra-high-strain-rate regime (higher than 10 s); however, they are limited by measurement noise and uncertainty in parameter estimation. A hierarchical Bayesian model selection method is employed using the Inertial Microcavitation Rheometry (IMR) technique to address these limitations. With this method, the parameter space of different constitutive models is explored to determine the most credible constitutive model that describes laser-induced microcavitation bubble oscillations in soft, viscoelastic, transparent hydrogels. The target data/evidence is computed using a weighted Gaussian likelihood with a hierarchical noise scale , which enables the quantification of uncertainty in model plausibility. Physically informed priors, including range-invariant, stress-based parameter priors, a model-redundancy prior, and a Bayesian information criterion motivated model prior, penalize complex models to enforce Occam's razor. Using a precomputed grid of simulations, the probabilistic model selection process enables an initial guess for the maximum (MAP) material parameter values. Synthetic tests recover the ground-truth models and expected parameters. Using experimental data for gelatin, fibrin, polyacrylamide, and agarose, MAP simulations of credible models reproduce the data. Moreover, a cross-institutional comparison of 10% gelatin indicates consistent constitutive model selection.
Wrinkles, rucks, and folds formed in a heavy sheet on a frictional surface.
Yoshida K, Wada H
Soft Matter · 2026 May · PMID 41978987 · Publisher ↗
Soft elastic sheets resting on rigid surfaces develop wrinkles, rucks, and folds due to the combined influence of elasticity, gravity, and contact interactions. Despite their ubiquity, the principles governing their morp...
Soft elastic sheets resting on rigid surfaces develop wrinkles, rucks, and folds due to the combined influence of elasticity, gravity, and contact interactions. Despite their ubiquity, the principles governing their morphology and transitions remain unclear. We introduce a minimal experiment in which the center of a gravity-loaded sheet is gradually lifted from the supporting plane. This operation generates a clear sequence of shapes: an axisymmetric uplift, a finite number of wrinkles, system-spanning rucks produced by global buckling, and folded states that can arise from ruck collapse upon unloading at larger lifts. Combining experiments, finite-element simulations, and Föppl-von Kármán theory, we establish a unified physical picture of this morphology sequence. In the frictionless case, elasticity and gravity alone govern the response, leading to a universal wrinkling threshold: the wrinkle number is fixed and the onset displacement scales linearly with the sheet thickness. With interfacial friction, the wrinkled state is described by introducing an additional nondimensional parameter that compares frictional and elastic-gravitational forces. These results suggest a simple route to programmable sheet morphogenesis friction and gravity.
Shape elasticity in colloidal bent-core liquid crystals.
Hackney NW, Clemmer JT, Grest GS
Soft Matter · 2026 Apr · PMID 41978532 · Publisher ↗
Curved particles have been shown to stabilize a range of states with unique order in dense suspensions of colloidal bent core liquid crystals. The shape of the colloidal rods encourages the formation of curved director f...
Curved particles have been shown to stabilize a range of states with unique order in dense suspensions of colloidal bent core liquid crystals. The shape of the colloidal rods encourages the formation of curved director fields. However, states of constant bend cannot uniformly fill either two or three dimensional Euclidean space and are therefore geometrically frustrated. As a result, curved rods are forced to couple their preference for bend with additional twist and splay deformations, giving rise to twist-bend and splay-bend states of nematic and smectic order. In this article, we study the effect of rod curvature on these diverse states of liquid crystalline order using molecular dynamics simulations of a bonded particle model of curved rods with tunable shape elasticity. Focusing on the case of intermediately curved rods, we find that curved rods go through a sequence of isotropic, nematic twist-bend and smectic splay-bend ordering as the density is increased from the dilute limit, in agreement with previous studies of rigid rods. As the rods become more elastic, the critical concentration separating these phases is shifted to higher density. Lastly, we find that flexibility weakens the first-order phase transition separating the isotropic and nematic twist-bend phases.
Dependence of ATP content in the formation of protrusions in DMPC GUVs under an AC electric field.
Ángeles-Robles G, Ruiz-Garcia J, Méndez JA … +1 more , Ortiz-Dosal LC
Eur Phys J E Soft Matter · 2026 Apr · PMID 41973276 · Publisher ↗
The cytoskeleton is an essential cell component. Many cellular processes that require changes in the cell structure depend on it. One of these processes is cell migration, which occurs through the formation of structures...
The cytoskeleton is an essential cell component. Many cellular processes that require changes in the cell structure depend on it. One of these processes is cell migration, which occurs through the formation of structures called protrusions that interact with other cytoskeletal components, enabling the cell to move slowly. These structures are formed by the polymerization of actin monomers, a process that requires the presence of ATP, as well as the exchange of divalent cations. In this work, we present a study on the formation of actin protrusions within DMPC giant unilamellar vesicles by varying the concentration of ATP, both in the absence and presence of MgCl. It was found that when the concentration of ATP in the overall protein buffer increases, these structures form and extend inside the vesicle without breaking it, even in the absence of MgCl. These protrusions are randomly oriented; however, when an alternating current electric field is applied, the protrusions align in the direction of the field in response to the polar nature of both lipids and actin filaments.
Rounded hard squares confined in a circle.
Yuan Z, Li Y
Soft Matter · 2026 Apr · PMID 41973000 · Publisher ↗
Packing under confinement could generate rich ordered structures through entropic effects, which is a fundamental problem in condensed matter, biophysics and material science. The influence of confinement on the anisotro...
Packing under confinement could generate rich ordered structures through entropic effects, which is a fundamental problem in condensed matter, biophysics and material science. The influence of confinement on the anisotropic hard particles-particularly regarding the emergence of topological defect structures-remains poorly understood. Recent studies have shown that granular rods confined within circular boundaries can cluster into square-like super-particles, forming four disclinations. In this study, we employ Monte Carlo simulations in the NPT ensemble to investigate how circular confinement influences the ordered structures of rounded-corner hard-squares with varying roundness. At low roundness, the system forms an integrated cross-shaped domain with tetratic order and four +1/4 disclinations in the corners, along with some column shifts. As roundness increases, we found a new partition structure, where particles self-assemble into six domains separated by six +1/4 disclinations and a central -1/2 disclination. Our findings reveal that the interplay between confinement geometry and colloid shape can drive entropy-governed structural transitions, offering new insights for the design of topological metamaterials.
Strengthening biofilms with selective metal ions.
Croland KJ, Bay RK
Soft Matter · 2026 Apr · PMID 41972322 · Publisher ↗
Biofilms are structured microbial communities consisting of bacteria embedded in a self-produced extracellular polymeric substance (EPS) that enables survival in diverse environments. The EPS can integrate materials from...
Biofilms are structured microbial communities consisting of bacteria embedded in a self-produced extracellular polymeric substance (EPS) that enables survival in diverse environments. The EPS can integrate materials from the surrounding environment, such as metal ions, which can provide additional mechanical protection to the embedded bacteria from environmental stressors. While previous studies demonstrated that metal ions impact the erosion behavior of biofilms, key quantitative properties, such as failure strain, remain largely undocumented due to difficulties in handling these viscoelastic and soft biomaterials. In this work, we introduce a technique to characterize the impact of metal ions on the uniaxial stress-strain response of bulk bacterial biofilms. Through applying this method to pellicles, we demonstrate that exposure to selective metal ions increases both the low strain elastic modulus and maximum stress, while decreasing failure strain. These effects are consistent with ion-mediated EPS crosslinking and are reversible through the introduction of a strong chelating agent, while variations in pH alone have a negligible impact on measured mechanical properties. We compare our results to previous biofilm erosion studies and provide insights into how metal ion interactions can alter the mechanical behavior of biofilms, which will aid in future biofilm mitigation strategies for biofouling or healthcare applications.
Structure-rheology-thermal property correlation in graphene oxide reinforced gum acacia--poly(acrylic acid) nanocomposite hydrogels.
Dave PN, Bamaniya S, Singh P
Soft Matter · 2026 Apr · PMID 41968854 · Publisher ↗
The rational design of sustainable hydrogel systems with tailored mechanical stability and tunable viscoelastic properties remains a central challenge in soft materials science. This study addresses this challenge throug...
The rational design of sustainable hydrogel systems with tailored mechanical stability and tunable viscoelastic properties remains a central challenge in soft materials science. This study addresses this challenge through systematic investigation of the rheological behaviour and microstructural characteristics of graphene oxide (GO)-reinforced gum acacia--poly(acrylic acid) (GA--PAA) nanocomposite hydrogels. The GA--PAA/GO hydrogels were synthesized free-radical graft copolymerization using ammonium persulfate as the initiator and ,'-methylenebisacrylamide as the crosslinker, yielding a covalently crosslinked three-dimensional network. Field-emission scanning electron microscopy reveals a pronounced morphological transition from a loosely packed, heterogeneous structure in the pristine polymer network to a dense, interconnected porous architecture upon GO incorporation, confirming uniform nanofiller dispersion and its role as a structural modulator. Rheological characterization demonstrates pronounced non-Newtonian shear-thinning behaviour across all compositions, with apparent viscosity decreasing from approximately 10-10 Pa s under low shear rates to less than 10 Pa s at 100 s. Oscillatory strain and frequency sweep analyses establish elastic-dominant viscoelastic behaviour, as evidenced by storage modulus (') values consistently exceeding loss modulus (″) across the measured frequency range. Notably, at an optimal GO loading (GO-3), ' exhibits a more than two-fold enhancement, increasing from ∼59 Pa for the pristine hydrogel to ∼131 Pa, indicating a substantial reinforcement of network stiffness. Thermogravimetric analysis further confirms improved thermal stability, reflected in elevated degradation temperatures and increased char yields reaching approximately 26% in GO-reinforced formulations. These property enhancements are attributed to the multifunctional role of GO nanosheets, which act as effective physical crosslinkers, establish strong interfacial interactions with the polymer matrix, restrict segmental mobility, and facilitate efficient stress transfer within the hydrogel network. Collectively, these findings establish controlled GO incorporation as a decisive parameter for engineering the structural integrity, viscoelastic response, and thermal endurance of gum acacia-based hydrogels. The resulting GA--PAA/GO nanocomposite hydrogels present a promising platform for advanced applications, including adsorption technologies, injectable and self-healing biomaterials, soft actuators, and stimuli-responsive smart hydrogel systems.
Mechanistic mapping of temperature-dependent ssDNA elasticity with oxDNA2 coarse-grained model.
Igwe IE, Abdulfatah S
Eur Phys J E Soft Matter · 2026 Apr · PMID 41966679 · Publisher ↗
The mechanical behavior of single-stranded DNA (ssDNA) controls its biological function and underpins the design of DNA-based nanodevices, yet the microscopic origin of temperature-dependent elasticity remains incomplete...
The mechanical behavior of single-stranded DNA (ssDNA) controls its biological function and underpins the design of DNA-based nanodevices, yet the microscopic origin of temperature-dependent elasticity remains incompletely quantified. Here, we use the salt-aware, sequence-dependent oxDNA2 coarse-grained model to map how intra-strand stacking and temperature jointly determine ssDNA mechanics for two prototypical homopolymers, poly(dA) and poly(dT), across 27-100 °C at 1.0 M monovalent salt. Large ensembles of independent simulations were used to extract equilibrium observables such as persistence length , radius of gyration , end-to-end distance , and equilibrium force-extension relations. We find that poly(dA) is substantially stiffer than poly(dT) at low temperature: = 44.8 ± 2.0 nm at 27 °C decreases to 10.0 ± 0.7 nm at 100 °C, while poly(dT) remains comparatively flexible, varying only from 1.40 ± 0.08 nm to 1.05 ± 0.04 nm. These macroscopic changes closely track the loss of intra-strand stacking. For poly(dA), the stacking fraction decreases from 0.70 ± 0.02 to 0.20 ± 0.01, whereas poly(dT) remains weakly stacked across the full range (< 0.10). Force-extension analysis shows that the wormlike chain (WLC) model captures low-force entropic elasticity but fails at intermediate extensions in strongly stacked poly(dA), where cooperative unstacking produces excess forces of ~ 8 to 10 pN near . The normalized root-mean-square residual at 27 °C is 0.22 for poly(dA), compared to 0.03 for poly(dT). When is normalized by its 27 °C value, both sequences collapse onto a single master curve as a function of stacking fraction (collapse slope ≈ 3.5 ± 0.3), indicating that fractional stacking loss serves as a unifying control parameter for thermal softening. These results quantitatively link microscopic stacking statistics to macroscopic elasticity, clarify the temperature-dependent limits of continuum polymer models, and provide a mechanistic framework for interpreting single-molecule stretching and ensemble measurements of ssDNA mechanics.
Symmetry-breaking motility of an active hinge in a crowded channel.
Rigon LG, Baek Y
Soft Matter · 2026 Apr · PMID 41966134 · Publisher ↗
A recent experiment [K. Son, Y. Choe, E. Kwon, L. G. Rigon, Y. Baek and H.-Y. Kim, , 2024, , 2777-2788] showed that self-propelled particles confined within a circular boundary filled with granular medium spontaneously f...
A recent experiment [K. Son, Y. Choe, E. Kwon, L. G. Rigon, Y. Baek and H.-Y. Kim, , 2024, , 2777-2788] showed that self-propelled particles confined within a circular boundary filled with granular medium spontaneously form a motile cluster that stays on the boundary. This cluster exhibits persistent (counter)clockwise motion driven by symmetry breaking, which arises from a positive feedback between the asymmetry of the cluster and those of the surrounding granular medium. To investigate this symmetry-breaking mechanism in broader contexts, we propose and analyze the dynamics of an active hinge moving through a crowded two-dimensional channel. Through extensive numerical simulations, we find that the lifetime of the hinge's motile state varies nonmonotonically with the packing fraction of the granular medium. Furthermore, we observe an abrupt transition in the configuration of passive particles that sustain hinge motility as the hinge's maximum angle relative to the channel wall increases. These findings point to the possibility of designing superstructures composed of passive granular media doped with a small number of active elements, whose dynamic modes can be switched by tuning the properties of their components.
Electromechanical responses in water-rich self-assembled amphiphile gels and hydrated ionogels: reassessing piezoelectric attributions.
Pensini E, Marangoni AG
Soft Matter · 2026 Apr · PMID 41960604 · Publisher ↗
Water-rich, self-assembled amphiphile gels have recently been reported to exhibit electrical responses under mechanical deformation and hysteretic cyclic voltammetry behavior, leading to their interpretation as piezoelec...
Water-rich, self-assembled amphiphile gels have recently been reported to exhibit electrical responses under mechanical deformation and hysteretic cyclic voltammetry behavior, leading to their interpretation as piezoelectric or ferroelectric soft materials. Such claims are particularly compelling given the relevance of hydrated, compliant electromechanical materials to biological, biomedical, and soft-sensing applications. However, in ion-containing soft matter, the electrical signatures commonly used to infer piezoelectricity are not uniquely diagnostic and may arise from multiple coupled mechanisms. Here, we re-examine the electromechanical behavior of fatty acid-amine, fatty acid-amino acid, and surfactant-fatty alcohol hydrogels previously described as piezoelectric. We show that capacitive cyclic voltammetry responses and mechanically induced voltage or current transients can be rationalized within a broader framework of electromechanical coupling in hydrated ionic gels, encompassing electrokinetic charge redistribution, electrode double-layer and interfacial effects, and strain-dependent dielectric responses, in addition to intrinsic polarization. As an instructive non-amphiphile comparator, ionotropically crosslinked carboxymethyl cellulose gels exhibit closely analogous electrical signatures only in the presence of multivalent ionic crosslinkers, reinforcing the non-uniqueness of piezoelectric interpretations in hydrated ionic systems. To clarify these distinctions, we introduce a minimal coupled electromechanical model that explicitly separates instantaneous elastic polarization from rate-dependent ionic contributions and identifies their distinct experimental signatures. We further propose discriminating experiments required to unambiguously distinguish intrinsic piezoelectricity from electrokinetic and interfacial effects. This reassessment does not diminish the functional relevance of these materials; rather, it provides a rigorous mechanistic foundation for their continued development as soft electromechanical transducers for sensing, biointerfacing, and biomedical applications.
The remarkable electrorheological behavior of amino-modified metal-organic frameworks with enhanced interfacial polarization.
Li S, Wang L, Zhang C … +5 more , Shan Z, Pang H, Ma L, Wang B, Hao C
Soft Matter · 2026 Apr · PMID 41954398 · Publisher ↗
Herein, amino-modified metal-organic frameworks (MIL-125) were prepared by mixing two different ligands before and after the modification of polar groups (amino) under solvothermal reaction conditions. Through the design...
Herein, amino-modified metal-organic frameworks (MIL-125) were prepared by mixing two different ligands before and after the modification of polar groups (amino) under solvothermal reaction conditions. Through the design of the substitution ratio of the polar group (NH), amino-modification not only enhances the polarization ability of MIL-125 but also induces rich porosity and irregular shape due to the asymmetry of the structure. The obtained amino-modified MIL-125 was then characterized in terms of its morphology, composition and structure, using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (TEM), Fourier transform infrared spectroscopy (FT-IR), Brunauer-Emmett-Teller (BET) and dielectric analysis. The amino-modified MIL-125 retained the large specific surface area and low bulk density of the metal-organic frameworks, and achieved charge redistribution and obtained additional polarization ability through the introduction of polar groups. Ultimately, the amino-modified MIL-125 exhibits a higher level of polarization, which results in a pronounced electrorheological (ER) behavior of the ER fluids when used as the dispersed phase.
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