Gel swelling dictates the functionality of gels in biomedical, sensing, and soft robotic systems. Gels can be readily shaped, making geometry a natural parameter for tuning swelling, yet how it regulates swelling dynamics remains poorly understood. Here we show that swelling in glassy polymer gels is inherently geometry-dependent, which introduces a geometric length Λ beyond the classical Fickian diffusion length L (volume-to-surface ratio) for controlling the diffusion process. Using a three-dimensional model applicable to arbitrary geometries, we find that disks swell fastest, spheres slowest, and cylinders in between, with this trend persisting in finite cylinder and tablet-shaped gels. Geometry regulates swelling not by altering solvent diffusion but by dictating mechanical confinement arising from the glassy-rubbery transition, where a glassy core constrains the surrounding rubbery network. These findings establish a physical rather than conventional chemical mechanism for diffusion regulation, offering a new design principle for gel-based systems.

We investigate the transport dynamics of elongated particles in cellular vortical flows that undergo spatial oscillations over time. Experimental flow visualizations reveal mixed flow fields with chaotic and elliptic regions coexisting. Surprisingly, the particle transport rate does not increase monotonically with particle length, even though longer particles are expected to explore neighboring vortices more easily. Numerical simulations in a much larger system produce similar transport anomalies, characterized by subdiffusion due to frequent longtime trapping in vortices at certain lengths but normal diffusion at others. At moderate oscillation frequencies, these longtime trapping events occur within the chaotic region; at high frequencies, they occur in the elliptic regions, but only for particles whose lengths match these regions. In the latter case, subdiffusion is robust against random noise. Our results reveal new mechanisms for controlling particle random walks and dispersal in fluid flows.

Yielding, plasticity, and necking are central to the mechanical performance of materials, yet a concise unified physical picture of how these nonlinear responses arise remains lacking. We develop a minimal theory for glassy polymers based on a classical volume-dependent relaxation time following the Doolittle equation, and derive the constitutive relation using the Onsager variational principle. Surprisingly, this simple theory explains yielding, plasticity, and neck initiation under constant strain rate loading via a shear unfreezing mechanism: as the sample is stretched, volume-increasing activated molecular mobility drives shear deformation from an initially frozen state to an unfrozen state. The theory yields an analytical expression for the yielding stress as a function of strain rate and temperature. It also predicts a phase diagram for necking initiation in the same parameter space, providing a mechanism beyond the classical Considère criterion. Our results establish a unified framework for nonlinear tensile behavior in glassy materials.

Surface creasing in swelling polymer gels is commonly attributed to compressive strain or interlayer mismatch, yet its general control remains unclear. Here we show that solvent polymerization degree N_ s provides an independent control parameter for crease onset in surface-bound polydimethylsiloxane gels swollen by silicone oils. Despite nearly identical swelling kinetics and through-thickness solvent concentration profiles, we observe a transition from creased to stable surfaces with increasing N_ s. A theory coupling swelling thermodynamics and mechanical stability reveals that polymeric solvents reduce the mixing entropy and thereby modify the osmotic pressure, allowing N_ s to tune separately the equilibrium swelling and the crease threshold. This framework captures the stability boundary across solvent polymerization degree and network elasticity. These results identify polymeric solvents as active thermodynamic-mechanical regulators of swelling-induced surface.

Bridging liquid metal (LM) droplets embedded in composite matrices, such as elastomer polymers, are crucial for maintaining high conductivity and mechanical stretchability in flexible electronics. However, the deformability of these LM bridges under strain remains poorly understood. Here, we combine in situ transmission electron microscopy experiments with theoretical modeling to investigate the effects of interface modulation on LM bridge deformability. We find that strong interfacial wettability between LM nanodroplets and the solid substrate enhances stretchability, while the surface oxide layer of LM nanodroplets plays a more complex role. A thin oxide layer promotes symmetric liquid bridge formation, whereas a slight increase in thickness induces super-stretched liquid bridges. However, excessive oxide growth suppresses deformability by reducing LM liquidity. Accordingly, a strategy for controlling the deformation was developed by modulating the thickness of oxides through the regulation of stretching duration. This study reveals the kinetics of interface-driven liquid bridge deformation, providing fundamental insights for the precise engineering of stretchable LM-based conductors in next-generation flexible electronics.

Highly aligned nanowire networks are essential for enabling anisotropic optical, electrical, and sensing functionalities in next-generation devices. However, achieving such alignment typically requires complex fabrication methods or high-energy processing. Here, a simple and scalable self-assembly strategy that uses a polymer additive to modulate fluid flows during solvent evaporation is presented. The addition of carboxymethylcellulose sodium (CMC-Na) reshapes the evaporation-driven flow field and generates a compressional flow region near the drying edge. Within this region, rotation-inducing velocity gradients progressively align silver nanowires (AgNWs) into highly ordered arrays. This unique mechanism yields uniform AgNW coatings with a high degree of nanowire alignment and tunable areal density across centimeter-scale areas. The resulting films exhibit strong broadband anisotropy, including polarization-dependent transmission in both visible and terahertz (THz) regimes and angle-dependent electrical conductivity. The approach also integrates naturally with dip-coating-based shear alignment, enabling programmable control over alignment direction and spatial patterning. This work establishes a robust, polymer-enabled mechanism for bottom-up nanowire alignment and offers a passive, energy-efficient route for fabricating anisotropic nanostructured coatings.

The evaporation of liquid droplets often results in a ring-like deposition pattern of particles, presenting challenges for applications requiring highly uniform patterns. Despite extensive efforts to suppress the coffee ring effect, achieving a uniform particle distribution remains a great challenge due to the complex and non-equilibrium nature of the evaporation process. In this work, a one-step drying method is introduced and demonstrated for binary droplets (water and 2-methoxyethanol) that produces uniform deposition of nano- and micro-particles. By adjusting the initial water volume fraction, we effectively control the interplay between capillary and Marangoni flows, resulting in deposition patterns that vary from coffee ring to uniform and to volcano-like. Through both theoretical and experimental analyses, we determine the conditions necessary for achieving such high uniformity. This approach requires no special substrate treatment, particle modification, or controlled environments, and works for various particles, including silica and polystyrene. This method provides a robust solution for fabricating uniform patterns that are crucial for many practical applications, ranging from printing to microelectronics to bio-pharmacy.

The translocation dynamics of cells and particles through geometric constrictions are critical in biological and biomedical processes from splenic filtration to tumor metastasis. While particle stiffness plays a key role, its role in highly nonequilibrium states remains poorly understood. Here, we present a multiscale model to investigate the impact of particle stiffness on the translocation dynamics in microfluidic channels. We find that semielastic particles exhibit superior translocation capabilities compared to both softer and more rigid particles, with a nonmonotonic stiffness dependence observed for highly deformable particles. Additionally, we identify crossover behaviors in translocation time driven by variations in the flow rate, particle size, and particle-plate interactions. Excessive particle deformation significantly regulates these dynamics, with stiffness-induced shape transitions from pancake-like to ellipsoidal forms, controlling frictional forces at the particle-channel interface and the sieve plate. The balance between these forces explains the observed nonmonotonic translocation dynamics. Our work provides insights into the relationship between particle deformability and flow dynamics, highlighting the importance of elasticity in translocation behavior. These findings have implications for designing microfluidic devices for efficient separation and analysis of cells with varying elasticities, advancing applications in human health diagnostics.

Ion exchange membranes (IEMs) are critical components in osmotic energy conversion. However, traditional IEMs suffer from disordered nanochannels due to the lack of precise control over the content and distribution of ionic groups, resulting in an inherent trade-off between ion selectivity and conductivity. One promising strategy is constructing high-density ion channels with minimal ionic groups. Herein, high-density ionic nanotube (INT) arrays are assembled from tiny carboxylic groups (≈0.22 meq·g-1), achieving efficient osmotic energy conversion. Using styrene-ethylene/butylene-styrene block copolymers, paired carboxyl groups and tetraphenylethylene (TPE) in the polyethylene/butylene block self-assemble into a transmembrane cylindrical phase. Driven by the cross-phase-miscibility effect of TPE, carboxyl groups aggregate at the cylinder interface, forming INT array membranes with an exceptional density of ≈10¹¹ cm⁻2. The unique structure is directly observed and further validated by self-consistent field theory. The INT array membranes exhibit 2 orders of magnitude higher current than the control membrane, and an ultrahigh power density of 39.5 W·m⁻2 under a 500-fold salinity gradient, significantly outperforming the traditional IEMs. This INT design strategy not only provides a promising approach for osmotic energy harvesting but also opens new avenues for advanced membrane-based separation processes.

Smart textiles capable of both energy harvesting and multifunctional sensing are highly desirable for next-generation portable electronics. However, there are still challenges that need to be conquered, such as the innovation of an energy-harvesting model and the optimization of interface bonding between fibers and active materials. Herein, inspired by the spiral structure of natural vines, a highly stretchable triboelectric helical yarn (TEHY) was manufactured by twisting the carbon nanotube/polyurethane nanofiber (CNT/PU NF) Janus membrane. The TEHY had a zebra-stripe-like design that was composed of black interval conductive CNTs and white insulative PU NFs. Due to the different electron affinity, the zebra-patterned TEHY realized a self-frictional triboelectric effect because the numerous microscopic CNT/PU triboelectric interfaces generated an alternating current in the external conductive circuit without extra external friction layers. The helical geometry combined with the elastic PU matrix endowed TEHY with superelastic stretchability and outstanding output stability after 1000 cycles of the stretch-release test. By virtue of the robust mechanical and electrical stability, the TEHY can not only be used as a high-entropy mechanical energy harvester but also serve as a self-powered sensor to monitor the stretching or deforming stimuli and human physiological activities in real time. These merits manifested the versatile applications of TEHY in smart fabrics, wearable power supplies, and human-machine interactions.

With the diversified development of human energy consumption, traditional fossil energy such as coal, oil and natural gas can no longer satisfy people's needs for industry and high quality life. Furthermore, the use of these energy sources often leads to severe environmental pollution. The emergence of clean energy sources like wind energy, water energy and solar energy not only effectively alleviates the issues of energy scarcity and environmental pollution but also promises a cleaner, healthier, and more sustainable future for global society. However, the efficient storage and utilization of these clean energy sources have become particularly crucial. The development of the new clean energy has continuously stimulated researchers to explore advanced devices for the electrochemical energy storage. Secondary battery has many advantages in electrochemical energy storage technology, such as portability and flexibility, high energy conversion efficiency and environmental friendliness, and is considered to be one of the most promising energy storage technologies at present. Therefore, the development of efficient new energy secondary batteries is the important way to achieve the goal of "carbon peak and carbon neutrality". As typical representatives of new-generation secondary batteries, lithium-ion and sodium-ion batteries play significant roles in our daily lives. Especially with the improvement of human living standards, there are higher demands for battery capacity, rate performance, and long-term cycling stability. In recent years, it has been discovered that the reasonable design of the structure and composition for anode/cathode materials is the key to achieve high performance secondary batteries. Structural design can significantly enhance the effective capacity and long-term cycling stability of existing materials. The design of electrode material composition can achieve synergistic effects between multiple components, enabling efficient redox reactions. Multi-structure hollow nanofiber materials have the advantages of controllable structure and adjustable composition, and are widely used as electrode materials for secondary batteries. In terms of structure, the multi-structure hollow nanostructure effectively alleviates the volume change of the electrode material in the electrochemical reaction process, prevents the electrode material pulverization and aggregation, increases the effective contact area between the electrolyte and the electrode material, and shorters the ion/electron transport path. In terms of composition, it is easy to achieve reasonable coupling of materials with different characteristics, so as to achieve specific adsorption of different materials, improve the conductivity of electrode materials, and accelerate the kinetics of redox reaction. In this review, representative methods for preparing multi-structure hollow nanofibers are summarized, including single-needle electrospinning, multi-fluid electrospinning and other synthesis methods (template method, hydrothermal method, and self-assembly method, etc.). Subsequently, we have summarized the application progresses of multi-structure hollow fibers with different structures and compositions in secondary batteries (including lithium-/sodium-/potassium-ion batteries, lithium/sodium-sulfur batteries, lithium-metal/air batteries, supercapacitors, etc.). Finally, we present the challenges and the application potential on the future research of multi-structure hollow nanofiber materials in the field of electrochemical energy storage.

Functional nanoparticles (NPs) have gained significant attention as a promising application in various fields, including sensor, smart coating, drug delivery, and more. Here, we propose a novel mechanism assisted by machine-learning workflow to accurately predict phase diagram of NPs, which elegantly achieves tunability of shapes and internal structures of NPs using self-assembly of block-copolymers (BCP). Unlike most of previous studies, we obtain onion-like and mesoporous NPs in neutral environment and hamburger-like NPs in selective environment. Such novel phenomenon is obtained only by tailoring the topology of a miktoarm star BCP chain architecture without the need for any further treatment. Moreover, we demonstrate that the BCP chain architecture can be used as a new strategy for tuning the lamellar asymmetry of NPs. We show that the asymmetry between A and B lamellae in striped ellipsoidal and onion-like particles increases as the volume fraction of the A-block increases, beyond the level reached by linear BCPs. In addition, we find an extended region of onion-like structure in the phase diagram of A-selective environment, as well as the emergence of an inverse onion-like structure in the B-selective one. Our findings provide a valuable insight into the design and fabrication of nanoscale materials with customized properties, opening up new possibilities for advanced applications in sensing, materials science, and beyond.

A sheet of glassy polymers placed in a solvent shows swelling behaviors quite different from that of soft polymers (rubbers and gels). (1) Non-Fickian diffusion (called case II diffusion): As solvent permeates into the sample, a sharp front is created between the swollen part and the glassy part, and it moves toward the center at constant speed. (2) Nonmonotonous swelling: The thickness of the sample first increases and then decreases toward the equilibrium value. Here we propose a theory to explain such anomalous behavior by extending the previous theory for swelling of soft gels. We regard the material as a continuum mixture of a glassy polymer network and solvent. We assume that the polymer network is a viscoelastic gel of glassy polymers, and its relaxation time depends strongly on solvent concentration. We show that this theory explains the above two characteristics of glassy polymers in a simple and unified framework. The theory predicts how the permeation speed of the solvent and the characteristic times of the swelling process depend on material parameters and experimental conditions, which can be checked experimentally.

Natural fibers with robust water repellency play an important role in adapting organisms to various environments, which has inspired the development of artificial superhydrophobic fibrous materials with applications in self-cleaning, antifogging, water harvesting, heat exchanging, catalytic reactions, and microrobots. However, these highly textured surfaces (micro/nanotextured) suffer from frequent liquid penetration in high humidity and abrasion-induced destruction of the local environment. Herein, bioinspired superhydrophobic fibrous materials are reviewed from the perspective of the dimension scale of fibers. First, the fibrous dimension characteristics of several representative natural superhydrophobic fibrous systems are summarized, along with the mechanisms involved. Then, artificial superhydrophobic fibers are summarized, along with their various applications. Nanometer-scale fibers enable superhydrophobicity by minimizing the liquid-solid contact area. Micrometer-scale fibers are advantageous for enhancing the mechanical stability of superhydrophobicity. Micrometer-scale conical fibrous structures endow a Laplace force with a particular magnitude for self-removing condensed tiny dewdrops in highly humid air and stably trapping large air pockets underwater. Furthermore, several representative surface modification strategies for constructing superhydrophobic fibers are presented. In addition, several conventional applications of superhydrophobic systems are presented. It is anticipated that the review will inspire the design and fabrication of superhydrophobic fibrous systems.

Three-dimensional (3D) cell culture models capable of emulating the biological functions of natural tissues are pivotal in tissue engineering and regenerative medicine. Despite progress, the fabrication of in vitro heterocellular models that mimic the intricate structures of natural tissues remains a significant challenge. In this study, we introduce a novel, scaffold-free approach leveraging the inertial focusing effect in rotating hanging droplets for the reliable production of heterocellular spheroids with controllable core-shell structures. Our method offers precise control over the core-shell spheroid's size and geometry by adjusting the cell suspension density and droplet morphology. We successfully applied this technique to create hair follicle organoids, integrating dermal papilla cells within the core and epidermal cells in the shell, thereby achieving markedly enhanced hair inducibility compared to mixed-structure models. Furthermore, we have developed melanoma tumor spheroids that accurately mimic the dynamic interactions between tumor and stromal cells, showing increased invasion capabilities and altered expressions of cellular adhesion molecules and proteolytic enzymes. These findings underscore the critical role of cellular spatial organization in replicating tissue functionality in vitro. Our method represents a significant advancement towards generating heterocellular spheroids with well-defined architectures, offering broad implications for biological research and applications in tissue engineering.

From a thermodynamic point of view, the swelling of a gel is determined by the competition between the elastic energy costed by the deformation of the polymer network and the attraction energy and entropy gained by the mixture of polymer and solvent. In this chapter, the history of the diffusio-mechanical coupling theory of gel swelling, including the general dynamical models for a spherical gel, a cylindrical gel and a disk shaped gel, has been summarized. We show detailed derivations of the evolution equations of displacement vector of gels undergoing small deformation and the corresponding analytical solutions, and present the basic results such as the time evolution of radius and the characteristic swelling time. We also discuss the possible extension that the diffusio-mechanical theory can be applied to the studies of large deformation, polymer network defects, and viscoelasticity for gel swelling.

Although past experimental and theoretical research has made substantial progress in understanding evaporation behaviors in various suspensions, the fundamental mechanism for polymer sessile droplets is still lacking. One critical effect is the molecular weight on the evaporation behaviors. Here, systematic experiments are carried out to investigate the evaporation behavior of polymer droplets under the effects of polymer concentration, evaporation rate, and especially molecular weight. We obtain polymer films with various morphologies with molecular weights ranging from 2 orders of magnitude to 4 orders of magnitude and polymer concentration across 4 orders of magnitude. We further develop a theoretical model based on the Onsager principle to explain the evaporation mechanism from a dynamic perspective. Analysis indicates that increasing molecular weight or polymer concentration enhances the contact angle hysteresis and slows down the evaporation, resulting in the transition from multiring to coffee ring and eventually to uniform films. The findings offer a guideline for achieving the desired deposition patterns via droplet processing techniques.

The kinetic paths of structural evolution and formation of block copolymer (BCP) particles are explored using dynamic self-consistent field theory (DSCFT). It is shown that the process-directed self-assembly of BCP immersed in a poor solvent leads to the formation of striped ellipsoids, onion-like particles and double-spiral lamellar particles. The theory predicts a reversible path of shape transition between onion-like particles and striped ellipsoidal ones by regulating the temperature (related to the Flory-Huggins parameter between the two components of BCP, χ_{AB}) and the selectivity of solvent toward one of the two BCP components. Furthermore, a kinetic path of shape transition from onion-like particles to double-spiral lamellar particles, and then back to onion-like particles is demonstrated. By investigating the inner-structural evolution of a BCP particle, it is identified that changing the intermediate bi-continuous structure into a layered one is crucial for the formation of striped ellipsoidal particles. Another interesting finding is that the formation of onion-like particles is characterized by a two-stage microphase separation. The first is induced by the solvent preference, and the second is controlled by the thermodynamics. The findings lead to an effective way of tailoring nanostructure of BCP particles for various industrial applications.

We investigate the effects of chain flexibility on the self-assembly behavior of symmetric diblock copolymers (BCPs) when they are confined as a thin film between two surfaces. Employing worm-like chain (WLC) self-consistent field theory, we study the relative stability of parallel (L_∥) and perpendicular (L_⊥) orientations of BCP lamellar phases, ranging in chain flexibility from flexible Gaussian chains to semi-flexible and rigid chains. For flat and neutral bounding surfaces (no surface preference for one of the two BCP components), the stability of the L_⊥ lamellae increases with chain rigidity. When the top surface is flat and the bottom substrate is corrugated, increasing the surface roughness enhances the stability of the L_⊥ lamellae for flexible Gaussian chains. However, an opposite behavior is observed for rigid chains, where the L_⊥ stability decreases as the substrate roughness increases. We further show that as the substrate roughness increases, the critical value of the substrate preference, u^*, corresponding to an L_⊥-to-L_∥ transition, decreases for rigid chains, while it increases for flexible Gaussian chains. Our results highlight the physical mechanism of tailoring the orientation of lamellar phases in thin-film setups. This is of importance, in particular, for short (semi-flexible or rigid) chains that are in high demand in emerging nanolithography and other industrial applications.

高分子薄膜在化工制造、绿色能源、材料、光电以及生命科学等领域有着重要的应用.溶剂蒸发作为高分子薄膜加工制备的重要手段,因其操作简单、成本较低和易于大规模制备的优点而被广泛应用和研究.本文综述了利用蒸发效应调控高分子溶液沉积图案、制备功能性高分子薄膜的研究进展,包括蒸发诱导高分子沉积图案的实际应用、基本原理和技术手段三个方面.本文旨在梳理该领域的各个研究方向及其相互联系,通过阐述溶剂蒸发对高分子沉积图案影响的机理为后续研究提供思路.此外,本综述简要总结了高分子溶液蒸发领域未解决的问题,并对未来发展方向进行了展望.