Soft Matter最新文献

Understanding interfacial molecular structures at the polymer/adjacent materials interface is essential for optimizing the performance of energy-related devices. However, it remains insufficiently explored due to limited interface-specific techniques. Here, we employed sum frequency generation (SFG) vibrational spectroscopy to investigate the substrate-dependent interfacial structures of spin-coated ultrathin poly(methyl methacrylate) (PMMA) films (∼10 nm) on silica and CaF₂ before and after thermal annealing. PMMA on silica exhibits similar OCH₃-dominated SFG spectra before and after annealing. In contrast, PMMA on CaF₂ shows a significant decrease in OCH₃ signals and enhancements of CH₂ and CH₃ signals upon annealing, revealing substantial molecular reorganization at the buried PMMA/CaF₂ interface. Quantitative analysis indicates that the OCH₃ groups adopt a tilt angle of ∼77° (assuming a δ-distribution) after annealing, suggesting a more lying-down or disordered orientation. These substrate-dependent differences arise from weaker interfacial interactions and the hydrophobic nature of the CaF₂ surface, which permits greater chain relaxation compared with the hydrogen-bond-constrained PMMA/silica interface. This study provides molecular-level and in situ insights into substrate-dependent structural evolution in polymer thin films and offers guidance for the interface engineering in photoelectric, photovoltaic, and energy-storage devices.

We use machine learning to analyze atomic force microscopy-force spectroscopy (AFM-FS) measurements of the mechanical properties of soft nanoparticles on a hard substrate. We compare two approaches based on the manual selection of features that describe various aspects of the mechanical properties measured using AFM-FS - one that uses an extreme gradient boosting algorithm (supervised learning), and the other based on k-means clustering (unsupervised learning) to classify the force-distance curves according to the features. We used these approaches to generate two machine learning (ML) classifiers - one to differentiate between the soft nanoparticles and the hard substrate, and the other to identify structure within individual nanoparticles based on nanoscale variations in their mechanical properties. After training the classifiers on data from just two AFM images, we found that both approaches were successful in correctly identifying individual soft nanoparticles within the AFM-FS scans, whereas the supervised approach was more successful in correctly identifying and quantifying stiffer inner regions within the nanoparticles. The results of our study show that ML strategies can be used to accurately and efficiently characterize nanoscale variations in the mechanical properties of soft, biological materials.

Cholesterol is an essential component of eukaryotic cell membranes, influencing membrane packing, fluidity, and domain formation. Replicating these properties in model membranes is critical for reconstitution studies, but common emulsion-based methods for producing giant unilamellar vesicles (GUVs) fail to incorporate cholesterol efficiently. Here, we use methyl-β-cyclodextrin-cholesterol (MβCD-CL) complexes to deliver cholesterol into GUVs produced by the emulsion droplet interface crossing encapsulation (eDICE) method and demonstrate a convenient way to quantify the degree of cholesterol incorporation using fluorescent membrane biosensors. Spectral imaging of NR12A as well as fluorescence lifetime imaging of Flipper-TR revealed dose-dependent increases in cholesterol content for DOPC GUVs upon MβCD-CL addition, consistent with increased membrane order. By calibrating these effects against GUVs with defined cholesterol contents prepared via gel-assisted swelling, we found that the cholesterol content of eDICE vesicles can be increased to at least 40 mol%. Binary mixtures of DOPC with saturated lipids (DMPC and PC (18 : 0-14 : 0)) showed a similar trend as pure DOPC GUVs. Interestingly, we could trigger liquid-ordered domain formation by adding cholesterol to DOPC : DMPC vesicles. Our findings provide a quantitative and non-disruptive method to modulate and assess cholesterol content in emulsion-based GUVs, advancing their use in bottom-up synthetic biology and membrane biophysics.

A flexible concentric coupled re-entrant-star (CCRS) composite structure is proposed to address the premature instability of a re-entrant honeycomb (RH) structure and the limited load-bearing capacity of a flexible star-shaped honeycomb (SH) structure. To elucidate deformation mechanisms, mechanical performance, and Poisson's ratio response, systematic comparative studies between the CCRS and conventional RH and SH were conducted, including uniaxial tension and cyclic loading. CCRS simultaneously exhibits a pronounced negative Poisson's ratio of -0.7 and markedly enhanced mechanical performance, outperforming RH by approximately 1.5 times and SH by about 3 times, while maintaining high deformability with fracture elongation exceeding 1060% and a stable cyclic recovery of about 96% even at a strain of 180%. These performance enhancements arise from an inner star-shaped unit that drives lateral expansion at low strain and an outer re-entrant hexagonal unit that provides load-bearing constraint at high strain, thereby producing more uniform stress distribution and suppressing local buckling. Consequently, CCRS offers an effective design strategy for architected soft matter systems requiring large deformation and enhanced load-bearing capacity.

Chiral liquid crystalline molecules can self-assemble and generate ferroelectricity (FE) or antiferroelectricity (AF) in tilted lamellar smectic C phases. In previous studies, lactic acid has been repeatedly employed as an effective source of chirality. In this study, we synthesized several mesogens with the aim to establish the role of chiral chains and reveal their influence on the mesogenic and polar properties. For the first studied mesogen, we utilized a methylbutyl group in the chiral chain. The second mesogen differed from the first one in incorporated (S)-lactate group added to prolong the chain terminated with a methylbutyl. In the third homologue, two (S)-lactates and one methylbutyl group form the chiral chain. To establish their optical purity by high-performance liquid chromatography (HPLC), additional derivatives were prepared with a racemic methylbutyl chain. We compared all the homologues with respect to the effect of the chiral chain modification. Among them, the third derivative with two lactates in its chiral chain exhibited an AF smectic phase, which was stable and enantiotropic in a broad temperature range, including the room temperature, which could be attractive for various applications.

Surface bubbles are an abundant source of aerosols, with important implications for climate processes. In this context, we investigate the stability and thinning dynamics of soap films under effective gravity fields. Experiments are performed using a centrifugal thin-film balance capable of generating accelerations from 0.2 up to 100 times standard gravity, combined with thin-film interferometry to obtain time-resolved thickness maps. Across all experimental conditions, the drainage dynamics are shown to be governed by capillary suction and marginal regeneration-a mechanism in which thick regions of the film are continuously replaced by thin film elements (TFEs) formed at the meniscus. We consistently recover a thickness ratio of 0.8-0.9 between the TFEs and the adjacent film, in agreement with previous observations under standard gravity. The measured thinning rates also follow the predicted scaling laws. We identified that effective gravity has three distinct effects: (i) it induces a strong stretching of the initial film, extending well beyond the linear-elastic regime; (ii) it controls the meniscus size and thereby the amplitude of the capillary suction and the drainage rate; and (iii) it reveals an inertia-to-viscous transition in the motion of TFEs within the film. These results are supported by theoretical modeling and highlight the robustness of marginal regeneration and capillary-driven drainage under extreme gravity conditions.

This study investigates the rheological behavior of shear-thickening suspensions made with different types of small particles upon the addition of much larger particles referred to as granules. The size ratio ranges from 20 to 120. We examine the effects of granule size, volume fraction, and surface properties on shear-thickening characteristics. Starting from a fumed silica suspension exhibiting discontinuous shear thickening (DST), the addition of granules at different volume fractions shifts the onset of thickening to lower shear rates. Concomitantly, the strength of the thickening, quantified by the thickening index, decreases, transitioning from DST to continuous shear thickening (CST). Comparison with suspensions of silica spheres reveals a similar trend, suggesting generality across different systems. These results contrast with the results of prior work on cornstarch-based and nanosilica sphere suspensions, where granule addition was found to enhance thickening. We discuss possible origins of these differences and propose a mechanism for the observed softening: when granules are much larger than the surrounding particles, they induce local variations in shear rate and disrupt the formation of an extended network of force chains. These findings highlight the critical role of particle size ratio in determining the rheology of complex suspensions, paving the way for tailoring material properties for industrial and scientific applications.

Material extrusion additive manufacturing (AM), which is utilized across a wide range of industries, necessitates the study of the extrusion and swelling of materials with complex rheological properties in the nozzle. This work aims to investigate the effects of physical parameters on the rheological properties of materials during extrusion. The rheology of thixotropic elastoviscoplastic (TEVP) fluids is predicted using the multi-lambda isotropic kinematic hardening (ML-IKH) model. Four different rheological models are initially examined to explore the distinctions between thixotropic behavior and other non-time-dependent rheological models. Results demonstrate that the interactions between the breakdown state and buildup state lead to stronger oscillations during the time evolution of the strands. Furthermore, the physical properties of the ink and structure of the nozzle are investigated to determine the rheology of the thixotropic fluid. Numerical results indicate that the rates of pressure and height change vary linearly with slopes of 49.3 and −12.8, respectively, for different elasticities and exhibit different patterns at varying yield stresses. Vortex analysis reveals that the maximum vortex area increases twice the minimum vortex area with increased elasticity. These findings demonstrate that the flow stability of thixotropic fluids is critically governed by structural parameters, with optimized configurations significantly suppressing flow instabilities and vortex formation. This research provides both qualitative and quantitative assessments of how structural and physical parameters influence the extrusion stability of thixotropic fluids. These findings offer crucial insights for optimizing nozzle design and printing parameters.

Correction for ‘Synthesis of anisotropic colloids with concave and convex structures’ by Longfei Luo et al., Soft Matter, 2021, 17, 10696–10702, https://doi.org/10.1039/D1SM01463C.

Customizable 2.5D microfluidic chips, tailored for rock-on-a-chip studies, are developed using direct laser writing (DLW) and soft lithography. Chip microchannels feature varied cross-sectional shape and height, convergences as small as 1-2 µm, and controlled nanoscale surface roughness. The impact of these 2.5D features on pore-scale transport phenomena is demonstrated with trapped bubble dissolution experiments.