Sandwich-Structured Quasi-Solid Polymer Electrolyte Enables High-Capacity, Long-Cycling, and Dendrite-Free Lithium Metal Battery at Room Temperature.

The insufficient ionic conductivity, limited lithium-ion transference number (tLi +), and high interfacial impedance severely hinder the practical application of quasi-solid polymer electrolytes (QSPEs). Here, a sandwich-structured polyacrylonitrile (PAN) based QSPE is constructedin which MXene-SiO2 nanosheets act as a functional filler to facilitate the rapid transfer of lithium-ion in the QSPE, and a polymer and plastic crystalline electrolyte (PPCE) interface modification layer is coated on the surface of the PAN-based QSPE of 3 wt.% MXene-SiO2 (SS-PPCE/PAN-3%) to reduce interfacial impedance. Consequently, the synthesized SS-PPCE/PAN-3% QSPE delivers a promising ionic conductivity of ≈1.7 mS cm-1 at 30 °C, a satisfactory tLi + of 0.51, and a low interfacial impedance. As expected, the assembled Li symmetric battery with SS-PPCE/PAN-3% QSPE can stably cycle more than 1550 h at 0.2 mA cm-2 . The Li||LiFePO4 quasi-solid-state lithium metal battery (QSSLMB) of this QSPE exhibits a high capacity retention of 81.5% after 300 cycles at 1.0 C and at RT. Even under the high-loading cathode (LiFePO4  ≈ 10.0 mg cm-2 ) and RT, the QSSLMB achieves a superior area capacity and good cycling performance. Besides, the assembled high voltage Li||NMC811(loading ≈ 7.1 mg cm-2 ) QSSLMB has potential applications in high-energy fields.

Vorticity-Aligned Droplet Bands in Sheared Immiscible Polymer Blends Induced by Solid Particles.

The spatiotemporal organization of complex fluids under flow can be strongly affected by incorporating solid particles. Here, we report that a monolayer of interfacially active microspheres preferentially wetted by the matrix phase can bridge droplets into vorticity-aligned bands in immiscible polymer blends at intermediate particle concentrations and low shear rates. Strong particle bridging ability and the formation of rigid anisotropic droplet bands with a negligible inertia effect in the Newtonian matrix are suggested to be responsible for the vorticity orientation of droplet bands during slow shear flow, which could be understood based on Jeffery orbit theory in the framework of fluid mechanics and strong confinement effect acted by shear walls and adjacent bands. However, increasing the aspect ratio of particles could restrain the formation of anisotropic bands because of reduced particle coverage and promoted droplet coalescence induced by sharp particle corners, increased and uneven distribution of particle aggregates in the matrix phase, and weakened particle bridging ability.

Controlling the Orientation of Droplets in Ellipsoid-Filled Polymeric Emulsions with Particle Parameters and Flow Conditions.

The effect of particle parameters [aspect ratio (AR) and concentration] and flow conditions (gap spacing and shear rate) on droplet orientation deformation behavior in polystyrene (PS) particle-filled binary polymeric emulsions is investigated by using a rheo-optical technique and confocal microscopy. Interesting vorticity orientation behavior is achieved by tailoring experimental conditions to yield rigid anisotropic droplets during slow confined shear flow. PS ellipsoids with a high AR are found to reside both at the fluid interface in a monolayer side-on state and inside droplets, leading to the formation of rigid anisotropic droplets because of the interfacial/bulk jamming effect at appropriate particle concentrations. In unconfined bulk samples, droplets with a vorticity orientation can also be observed under the wall migration effect and confinement effect arising from nearby droplets. However, the overly strong wall confinement effect remarkably facilitates the coalescence of vorticity-aligned droplets during slow shear, eventually leading to the formation of a long stringlike phase aligning along the flow direction. High shear rates generate refined droplets with lower particle coverage and weak rigidity, which restrain the formation of anisotropic droplets and thus suppress the droplet vorticity orientation.

Suppression of wetting-induced percolation-to-droplet transition in near-critical polymer blend films by nanoparticles.

A new kind of percolation-to-droplet transition (PDT) caused by selective wetting was identified in near-critical polymer blend films. Nanoscale particles proved to possess superior ability in suppressing this morphological transition.

Droplet coalescence and clustering behavior in microsphere-filled polymeric emulsions under shear flow: the key role of asymmetric interfacial affinities.

The flow-induced spatial organization of the droplet phase in ternary polymeric emulsions consisting of two Newtonian fluids, namely polyisobutylene (PIB) and polydimethylsiloxane (PDMS), in the presence of a small amount of solid polystyrene (PS) microspheres are explored by direct flow visualization. The results suggest that the asymmetric affinities of interfacially located PS microspheres to two fluid components lead to diverse flow-induced morphologies in PIB/PDMS blends with different compositions. In 10/90 blends where microspheres are preferentially wetted by the PIB droplets, significantly promoted coalescence of PIB droplets is observed. Increasing the loading of microspheres or changing the shear rate will alter the size and spatial distribution of PIB droplets. In contrast, in the inverse 90/10 blends where microspheres are wetted by the continuous PIB phase, bridging of PDMS droplets is found, leading to the generation of string-like or grape-like clusters. These results indicate that the flow-induced morphology of PIB/PDMS blends in the presence of PS microspheres is not only determined by the experimental conditions such as shear rate but also to a large extent by the asymmetric interfacial affinities of microspheres for fluid components.

A bead-spring model for running and tumbling of flagellated swimmers: detailed predictions compared to experimental data for E. coli.

To study the swimming of the multi-flagellated bacterium Escherichia coli, we deploy a bead-spring hydrodynamic model (Watari and Larson 2010), whose body and flagellar geometry, motor torques, and motor reversals are adjusted to match the experimental observations of the Berg group (Turner et al. 2000; Darnton et al. 2007) during both running and tumbling of the bacterium. In this model, hydrodynamic interactions, which drive swimming, flagellar bundling, and unbundling during swimming and tumbling, are imposed by treating the beads as Stokeslets, imposing torques and counter-torques on the body and flagellum at the flexible joint connecting them to represent the action of motor, and using the Rotne-Prager tensor to model their hydrodynamic interactions with other beads. We explore the behavior of coarse-grained (60-bead) and refined (120-bead) versions of the model, and show that predictions of running speed, helical and body rotation rates, body wobble rates and angles, average tumbling angles, range of tumbling angles, and flagellar re-bundling times are in good agreement with experimental observations by Berg and coworkers. We find that variation in tumbling angle arises from variation in flagellar number and location on the bacterial body, variations in polymorphic transitions of the filaments, and especially from variations in the duration of the tumbling time, which is roughly linearly correlated with tumbling time up to tumbling angles of around 40-50° and more weakly thereafter. The accuracy of the model suggests its usefulness for future studies of swimming of other flagellated swimmers, for predictions of collective phenomena, and for tuning parameters of coarser-grained swimmer models to achieve greater realism.

Integrated Fibrous Iontronic Pressure Sensors with High Sensitivity and Reliability for Human Plantar Pressure and Gait Analysis.

Flexible sensing systems (FSSs) designed to measure plantar pressure can deliver instantaneous feedback on human movement and posture. This feedback is crucial not only for preventing and controlling diseases associated with abnormal plantar pressures but also for optimizing athletes' postures to minimize injuries. The development of an optimal plantar pressure sensor hinges on key metrics such as a wide sensing range, high sensitivity, and long-term stability. However, the effectiveness of current flexible sensors is impeded by numerous challenges, including limitations in structural deformability, mechanical incompatibility between multifunctional layers, and instability under complex stress conditions. Addressing these limitations, we have engineered an integrated pressure sensing system with high sensitivity and reliability for human plantar pressure and gait analysis. It features a high-modulus, porous laminated ionic fiber structure with robust self-bonded interfaces, utilizing a unified polyimide material system. This system showcases a high sensitivity (156.6 kPa-1), an extensive sensing range (up to 4000 kPa), and augmented interfacial toughness and durability (over 150,000 cycles). Additionally, our FSS is capable of real-time monitoring of plantar pressure distribution across various sports activities. Leveraging deep learning, the flexible sensing system achieves a high-precision, intelligent recognition of different plantar types with a 99.8% accuracy rate. This approach provides a strategic advancement in the field of flexible pressure sensors, ensuring prolonged stability and accuracy even amidst complex pressure dynamics and providing a feasible solution for long-term gait monitoring and analysis.

Fully biodegradable polylactide foams with ultrahigh expansion ratio and heat resistance for green packaging.

Long chain branching (LCB) structures are efficiently introduced into polylactide (PLA) by employing sustainable soybean oil (SO) under the initiation of trace amount of cyclic peroxide, which displays robust foamability and heat resistance. It is discovered that with the introduction of 0.6 wt% SO, the expansion ratio and Vicat softening temperature of LCB PLA are sharply raised to 75.2-fold and 155.8 °C, respectively, which is about 17.9 and 2.6 times those of linear PLA. This is because that the amounts of LCB structures are significantly increased in LCB PLA by the addition of SO with low reactivity of internal CC bonds, which can avoid the oligomerization reaction, resulting in more dramatically improved melting strength and crystallization performance of LCB PLA. Moreover, the hydrolytic degradation of LCB PLA is largely expedited as compared to linear PLA, owing to the more rapid water permeation caused by the loose packing of LCB structures. Finally, the PLA foam tray with light weight and good heat resistance is successfully developed by using LCB PLA with 0.6 wt% SO through extrusion foaming with supercritical carbon oxide and thermoforming techniques. Hence, this research offers a green route to produce eco-friendly light-weight and high-heat-resistance LCB-PLA foam with full biodegradability, which is an ideal alternative to the non-degradable oil-based plastics in the field of disposable packaging products.

Synthesis of poly(ionic liquid) for trifunctional epoxy resin with simultaneously enhancing the toughness, thermal and dielectric performances.

Poly(ionic liquid) (PIL), integrating the characteristics of both polymers and ionic liquid, is synthesized and employed to modify diglycidyl-4,5-epoxy-cyclohexane-1,2-dicarboxylate (TDE-85). With the addition of PIL, the fracture toughness, and thermal and dielectric performances of TDE-85 were discovered to be simultaneously improved, meanwhile the tensile modulus and strength is increased. Upon an optimal loading of 3 wt% PIL, the critical stress intensity factor (K IC), tensile modulus and strength are raised by 92.9%, 13.3% and 10.7%, respectively. Multi-toughening mechanisms due to spherical domains of PIL formed in TDE-85 during curing are responsible for the improved toughness. Moreover, the dielectric and thermal properties of TDE-85 are also enhanced by adding PIL. With the optimal addition of 5 wt% PIL, the dielectric constant of the composites is enhanced by 62.5%, the glass transition temperature is increased by 16.58 °C and the residual weight of carbon is increased by 59%.

Morphology Mapping of Nanoparticle-Filled Immiscible Polymer Blends in Flow: The Existence of a Critical Ratio between Nanoparticle Concentration and Droplet Concentration.

The delicate flow-induced morphology of immiscible polypropylene/polystyrene blends in the presence of silica nanoparticles (NPs) is investigated in a multiparameter space. The morphology map constructed based on in situ morphology observation reveals that a critical ratio of NP concentration to droplet concentration, which strongly depends on the NP surface chemistries and the ratio of the NP concentration to the droplet concentration, exists. Below or above the critical ratio, the NPs display diverse effects on the morphology (promote or suppress droplet coalescence). These results can be interpreted by the competition between the bridging mechanism (acceleratory effect) and the enhanced viscoelasticity (inhibitory effect) exerted by the NPs.

Toward simultaneous toughening and reinforcing of trifunctional epoxies by low loading flexible reactive triblock copolymers.

Flexible reactive poly(glycidyl methacrylate)-b-poly(propylene glycol)-b-poly(glycidyl methacrylate) (GPG) and nonreactive poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) (EPE80) were utilized to toughen a trifunctional epoxy (diglycidyl 4, 5-epoxycyclohexane-1, 2-dicarboxylate, TDE-85). In comparison with the nonreactive EPE80 and reactive GPG92 with long reactive blocks (L reactive), the incorporation of reactive GPG83 with short L reactive improved the comprehensive mechanical properties of the epoxy. Upon an optimal GPG83 loading of 2.5 wt%, the tensile strength, elongation at break and critical strain energy release rate (G 1c) increased by ca. 31%, 45.9% and 130.8%, respectively, without sacrificing the modulus and thermal stability. Morphology characterization evidenced that micro-scale domains and nanosized vesical micelles coexisted in the nonreactive EPE80 toughened systems. However, homogeneous morphologies were formed in reactive GPG83 and GPG92 toughened systems. Fracture morphology analysis suggested that GPG can toughen epoxy thermosets by incorporating flexible PPG blocks into the epoxy network, thereby enabling an energy dissipation mechanism. The good balance between the mobility of flexible PPG and degree of cross-link density leads to the simultaneous toughening and reinforcing effect of GPG83 toward the trifunctional epoxy.

Vorticity Deformation in Polymeric Emulsions Induced by Anisotropic Ellipsoids.

We study the influence of particle shape on shear-induced droplet deformation in polymeric emulsions. During shearing, droplets become elongated and rotate periodically about their major axes while aligning along the vorticity direction in ellipsoid-filled emulsions, while similar behavior is not observed in the pristine, microsphere-filled or ellipsoid-filled inverse systems. Based on the Jeffery orbit theory, the formation of anisotropic droplets with extremely small Reynolds number due to arrested coalescence in Newtonian matrix and strong confinement effect are suggested to be responsible for the vorticity alignment of droplets during slow shearing.