GIANT最新文献

Soft adhesive systems (SASs), which consist of a soft adhesive layer and/or soft adherends, have been extensively applied in advanced fields such as biomedicine, flexible electronics, and soft robotics. Understanding the fatigue failure of SASs is crucial for ensuring their structural safety and functional stability, as they are often subjected to fatigue loading. This paper systematically reviews the fatigue failure of SASs, aiming to provide a comprehensive understanding and contribute to the study of fatigue failure mechanisms and lifetime prediction of SASs. The review starts by introducing classical research methods for fatigue failure of adhesive systems, with a focus on total fatigue lifetime and fatigue crack growth (FCG). After summarizing the complexity of fatigue failure in SASs, it provides an overview of fatigue research for the three types of SASs: “soft interface”, “soft adherend”, and “soft-soft” adhesive systems. Then, the relations between the fatigue failure and energy dissipation of various SASs are specifically discussed noting that significant energy dissipation accompanying the cyclic deformation of SASs during fatigue loading can substantially affect the final fatigue failure of SASs. Finally, the current unresolved issues and challenges in this field are presented.

The low-temperature environment caused by solvent evaporation leads to the condensation of water vapor into water droplets that remain on the surface of the film to form breath figure patterns. The conventional approach to regulate the pore morphology in the breath figure process is to optimize the ambient temperature, humidity, and solution concentration. However, realizing a wide adjustable window of pore size and uniform distribution of the pore are still challenges. Here, inspired by the rainfall phenomenon, we proposed a simple and efficient method called the “raining boxing method” (RBM) for preparing porous films based on exogenously given water droplets as templates. The RBM broadened the adjustable window of pore size (0.6–225 µm in this work) and solved the inherent problem of radial reduction of pore size from the film center to the edge caused by the significant difference in low-temperature duration at different locations accompanying the solvent evaporation process. Furthermore, this method could realize multi-types porous films, including surface porous films, spongy porous films, and honeycomb porous films, and could be universally applied in the casting process of various polymer solutions.

The twist-bend nematic (N_TB) phase of achiral liquid crystals (LCs) manifests a unique self-assembled heliconical structure with nanometer-scale pitch length, mirroring the chiral symmetry-breaking phenomena in nature, thus sparking widespread research interest. However, the ingenious N_TB phase is only stable at high temperatures within a very limited temperature interval, often undergoing inevitable crystallization at low temperatures. Herein, room temperature supercooled N_TB material systems composed of meticulously designed LC dimer mixtures with varying molecular curvatures and central flexibility were developed, resulting in complete resistance to crystallization even after 1 year of storage. Furthermore, the proposed N_TB material systems demonstrated exceptional compatibility with common nematic LCs, facilitating the tailoring of overall physical parameters, particularly to achieve a sufficiently low bend elastic constant with excellent stability. This work represents a paradigmatic advancement forward in realizing stable N_TB phase materials with a broad temperature range and resistance to crystallization, thereby tackling the enduring and seemingly insurmountable challenge while providing impetus for further exploration of their applications in soft matter, crystallography, and advanced photonics.

With the development of intelligent protective wearable equipment, flexible materials with impact resistance have become a focus of attention. Shear stiffening gel (SSG) is a flexible smart material that can perceive external force loads and generate mechanical responses, boasting exceptional properties like fast response, adaptability, and self-healing. Since the SSG can absorb a large amount of energy during dynamic impact, it shows remarkable advantages for safety protection applications. During the past decade, there has been strong interests in the research community on the SSG composites and their various applications in cutting-edge fields. In this review, we summarize the recent research achievements of SSG composite, by focusing on the improved properties, enhanced functions, and manifold structures. Meanwhile, we also discuss the practical applications of SSG composite in battery protection, vibration control, intelligent sensing, wearable safety protection, and triboelectric nanogenerator (TENG). Finally, we propose the prospects and challenges for the further development and application of SSG composite in the future.

The features of the degradation of the "green" plastic poly(3-hydroxybutyrate) [P(3HB)] in the soil of various geographical regions were studied: in red ferralitic soil under tropical conditions (Kerala, India) and in chernozem soil under conditions of a sharply continental climate (Eastern Siberia, Russia). Significant differences in the chemical composition, temperature, and humidity of the studied soils were revealed. The number of bacteria and mycelial fungi in the Siberian chernozem was higher than in the red soil of India, from 2-3 to 10 or more times. The degradation of P(3HB) films in the chernozem occurred faster than in the red soil, which was drier, with a low content of humus and minerals, and fewer microorganisms than the chernozem. The half-life of polymer samples in Siberia and India was 64.8 and 126.4 days, respectively. During degradation, a decrease in the molecular weight and an increase in the degree of crystallinity of polymer samples were revealed, which indicates a more active biodegradation of the amorphous phase of the polymer by soil microorganisms. The primary degraders of the polymer have been isolated and identified, and it has been shown that the complexes of degrading bacteria and fungi in different types of soils did not have common species. Despite the presence of species with pronounced depolymerase activity, the rate of film degradation in red ferralitic soils was slowed down by unfavorable environmental conditions. The obtained results confirm the importance of studying the process of PHA degradation in natural conditions.

Polymer network is a crucial component of hydrogels, and network imperfection is a prominent feature of polymer networks, significantly influencing the performance of hydrogels. Two essential features of network imperfection are unequal chain lengths and dangling chains, both of which have a significant impact on the mechanical properties of single-network (SN) hydrogels. However, a theoretical framework considering network imperfection in SN hydrogels is still lacking. Here, we propose a theoretical model for SN hydrogels with network imperfection to study the damage behavior during deformation, in which we adopt different chain length distributions to accurately depict the real physical characteristics of the polymer network and incorporate the normalized critical chain force for a more precise measurement of network damage. To verify our theory, we discuss the effects of model parameters on the stress-stretch responses of SN hydrogels and predict the results of uniaxial loading-unloading tests of SN hydrogels, which agree well with experimentally measured stress-stretch behaviors. Finally, we implement the constitutive model into ABAQUS as a user subroutine to study the inhomogeneous deformation of hydrogels.

Nowadays, microneedles as novel transdermal delivery systems are interested in scientists for biomedical applications. This work aims to present a Cascade Microneedle Molding Technique (CMMT) for the reusable fabrication of polydimethylsiloxane (PDMS) molds to produce microneedle devices. To produce a positive master mold from epoxy resin, a negative PDMS mold was first fabricated. PDMS can be molded, and microneedles can be fabricated using this epoxy mold in a scalable and cost-effective manner. These molds were used to manufacture solid, coated, and dissolving microneedles, which were characterized comprehensively. Microneedle morphology and geometry were evaluated using Scanning Electron Microscopy (SEM). The mechanical integrity and ability to insert the microneedle device into the skin were assessed using compression strength analysis and force-displacement measurements. Drug penetration through animal skin was evaluated for Rhodamine B (RhB) loaded microneedles. The depth of needle insertion was also visualized using histological analysis while the spatial distribution of released cargo was determined by using confocal microscopy. Taken together, CMMT offers a simple, rapid, cost-effective, and scalable method for mass-producing microneedles with remarkable properties compared to direct 3D printing or laser ablation.

Biobased furan resins (furfuryl alcohol based) are functionalized by taking advantage of a side-reaction occurring during its polymerization. The furan ring-opening reactions yields carbonyls which can be functionalized by reaction with primary amines. Light is shed on unexplored parameters impacting the properties of PFA/Amine systems. First, PFA/Amines were prepared using PFA resins at conversion degree between 0.3 and 0.95. Overall, high conversion degrees (0.9 and above) are best suited to produce rigid materials. In addition, a precipitation process may be used to reach high T_g biobased materials (145 °C). Finally, the impact of the amines’ basicity on the properties of PFA/Amines was investigated. The results highlighted that PFAs at conversion degrees above 0.9 are little affected by the basicity. However, the properties of PFA functionalized at lower conversion degrees are strongly affected by the bases, i.e. high brittleness. This can be circumvented by limiting the functionalization degree to 0.25 and below.

High-efficiency organic solar cells (OSCs) are typically produced through spin-coating, restricting their application to small areas. Blade-coating, however, emerging as a promising method for large-scale production, yet faces challenges in film morphology optimization, which often leads to reduced power conversion efficiency (PCE). This study delves into the influence of both liquid and solid additives on the morphology of active layer in blade-coated OSCs, comparing them with spin-coated counterparts, using the high-efficiency PM6:D18:BTP-eC9 active layer. For the first time, we discovered the distinct impacts of solid versus liquid additives on the film uniformity, phase separation and crystalline regulation in blade-coating technique. Our findings reveal that liquid additives in blade-coating trigger outward Marangoni flow, causing undesirable material aggregation and phase separation, thereby impairing device performances. Conversely, switching to solid additives, like 1,4-Diiodobenzene (DIB), prevents these detrimental changes in fluid mechanics and preserves the desired additive effects. We demonstrate that solid additives can significantly change these inferior behaviors introduced by liquid additives in blade-coating, regulate phase separation, enhance π-π accumulation and delay crystallization, and ultimately boost OSC efficiency. Using DIB solid additive, we achieved a PCE of 18.81 % in blade-coated devices. Scaling up by 252 times, the PCE of large-area OSC module (15.64 cm²) sustained at 16.70 % (certified 16.66 %), ranking among the highest efficiency for OSC modules reported so far. These modules also exhibited exceptional storage stability, retaining 98 % efficiency after 5880 h in a nitrogen atmosphere. This research also provides a comprehensive understanding from various film characterizations and the perspective of fluid mechanics normally lack in the research. This research not only establishes a new framework for high-performance and large-area OSC modules but also extends its findings to other OSC systems with different additives, demonstrating a roll-to-roll compatible technique.

To enhance the degradation rate of poly (butylene adipate-co-terephthalate) (PBAT) in the natural environment and to investigate the effect of modified monomers on the molding and structure of copolyester fibers, a series of isosorbide modified PBAT (PBIAT) tetrapolyesters were synthesized and monofilaments were prepared by solid-state drawing in this work. The experimental results revealed that the introduction of isosorbide formed a partial block structure in the molecular chain, and that a significant improvement in the properties of heat resistance and degradability of the copolyester was observed with the introduction of isosorbide. In the research of fiber forming and structure-property relationship by isosorbide, it was found that although the monofilament orientation process was affected by the V-shape structure of isosorbide, the change of the crystal structure under stress was similar to that of polybutylene terephthalate (PBT). The PBIAT monofilaments showed a decrease in the strength at break affected by the introduction of isosorbide but they still met the requirements for textile applications.