Materials Today最新文献

Inspired by methods of wet fiber spinning, we introduce a process using a 3D printer to create dense carbon nanotube (CNT) fibers and extensible coils with metal-like DC specific conductivity. An extrusion-based printer with an immersed nozzle extrudes a homogeneous shear-thinning ink (with initially < 1 % CNT concentration in water) into a liquid bath of antisolvent, inducing immediate precipitation-driven solidification slightly beyond the nozzle tip. This process forms continuous fibers of CNTs with conductivity up to 3 × 10⁵ S/m, exceeding that of dense graphite and approaching that of CNTs spun from similar inks in a continuous fiber spinning process (6 × 10⁵ S/m). The specific conductivity is up to 1 × 10³ S m²/kg, comparable with gold (2.3 × 10³ S m²/kg). The printing regimes are analyzed, with consideration of the draw ratio imposed during printing. Particular focus is placed on adjusting the speed of counter-diffusion of the ink solvent and the bath liquid, which allows for tuning of fiber diameter, conductivity, and specific conductivity respectively over ranges of one, four, and five orders of magnitude. The conductivity of resulting fibers is maximized when the speed of solvent counter-diffusion is high and the radius reduction is largest. When extrusion speed is also high relative to speed of the nozzle motion, a fluid mechanical coiling instability emerges which creates filaments with periodic coils, allowing for intricate designs to be formed along a linear extrusion path. Once dried, these densely coiled structures initially maintain their shape and can subsequently undergo up to 50 % strain with under 1 % change in resistance and 170 % linear extension with 20 % increase in resistance as the coils unwind. The resulting complex coil structures have applications in lightweight circuitry and as flexible interconnects.

Antifouling coatings play a crucial role in preventing the adhesion of marine organisms, bacteria, and blood, making them a primary strategy for combating biofouling in the marine industry. However, conventional antifouling coatings suffer from drawbacks such as high toxicity, limited abrasion resistance, and unstable polymer degradation rates, which can have adverse effects on the environment, economy, and human health. Thus, there is an urgent need for the development of sustainable and nontoxic antifouling coatings. This review first presents four major antifouling strategies: traditional coatings based on wettability, traditional coatings with protective structures, nontoxic coatings based on main chain degradable polymers, and nontoxic coatings combining main chain degradation with branch chain hydrolysis polymers. Second, the review provides a comprehensive overview of antifouling coatings with diverse functionalities, including antibacterial, anti-protein, anti-blood, anti-incrusting, adhesive, self-healing, and corrosion-resistant properties. Then, the application of antifouling coatings in marine environments and the medical field is thoroughly explored. Additionally, the review addresses the current challenges encountered by antifouling coatings. Finally, a forward-looking perspective is presented, envisioning future advancements in this field. By addressing these aspects, this review aims to stimulate further development and innovation in the realm of antifouling coatings.

Noncovalent π-stacked organic frameworks (πOFs) are a subclass of porous materials that consist of crystalline networks formed by self-assembly of organic building blocks through π-π interactions. Weak intermolecular interactions including π-π interactions have been well studied in the field of supramolecular chemistry and further employed for constructing porous molecular materials. The flexible, reversible, and conductive nature of π-π interactions and π-delocalized supramolecular frameworks impart advantageous attributes to πOFs, including solution processability, self-healing capability, notable carrier mobility and excellent stability. These features make πOFs ideal candidates not only for conventional applications like gas separation, molecular structure determination, and electrocatalysis, but also for endeavors that traditional porous materials can hardly pursue. In this review, we describe the evolution of πOFs chronologically, starting from the development of the π-π interactions model, which has led to the creation of complicated supramolecular architectures and the introduction of the concept of πOFs. Through comparing πOFs with other prevailing porous materials, we highlight their unique aspects of fundamental chemistry and practical advantages. We also summarize the physical properties and applications of πOFs through elucidating the structure–function correlations. Finally, we discuss the design strategies of πOFs that allow for emerging functional applications beyond what traditional porous materials have achieved.

Infants are exceptionally fragile and physically vulnerable who need special healthcare. Continuous monitoring of vital information of infants is essential for understanding their health status. Whereas modern infant health monitoring is carried out with dedicated facilities in controlled hospital settings, they are associated with several issues such as potential iatrogenic injuries, barriers for skin-to-skin parental bonding, and even complications during basic clinical tasks. Recently, soft electronics have become an accessory and mobile infant monitoring platform with remarkable advantages over existing technologies. This review comprehensively summarizes the research advances on soft electronics for advanced infant monitoring. We first introduce the physiological characteristics from anatomy, diseases, and treatments of infants. In accordance with these characteristics, we discuss the progressive achievements of soft bioelectrical, biophysical, biochemical, and hybrid monitoring technologies for infants. In addition, we offer insights into the remaining challenges and future directions of a soft electronics based intelligent system for clinical-grade infant monitoring from sensor design, data processing, power supply, and digital interactions in the era of Internet of Things. Finally, we highlight the translational challenges to be considered in bringing soft electronics for infant monitoring from the benchtop to the bedside.

Metal nanoparticles (MNPs) with complex structure and uniform distribution demonstrate interesting physicochemical properties and thus are widely applied. The traditional wet chemistry methods are commonly applied to construct MNPs structure, yet they still exhibit limitations in the liquid-phase environment, particularly, for synthesis of supported MNPs in one-step process. Diverse synthesis strategies have been investigated to design complex MNPs in a more efficient manner, among which the thermal treatment atmosphere induced solid-phase ion diffusion (TASID) synthesis strategy serves as an attractive strategy. This review summaries recent progresses of complex MNPs construction via TASID synthesis strategy, which realize the structure design through thermally treating the precursors under various gas atmosphere, such as oxidative, reductive, carbonaceous, and inert gas. This TASID strategy can both achieve the MNPs structure design and uniform dispersion simultaneously, demonstrating its unique properties. MNPs with diverse composition and structure, such as hollow, core@shell, yolk@shell, Janus, and multi-chamber structure, are successfully synthesized. The TASID synthesis mechanisms of galvanic replacement, Kirkendall effect, Ostwald ripening, carburization, and exsolution are elaborated in detail. The synthesis-mechanism-structure correlation of TASID is identified and the applications of these constructed MNPs are presented. This strategy could be developed into a class of synthetic methods by applying various thermal gas.

Outdoor radiative cooling is a passive method of cooling a surface that faces the sky. During the past decade, numbers of successful demonstrations of daytime radiative coolers have been reported. Because a daytime radiative cooler can be radiatively cooled both during the day and at night, it is always cooled and a temperature difference against the surroundings is generated. This temperature difference can be used to generate thermoelectric power throughout the day by placing a daytime radiative cooler on a thermoelectric module. However, such a device cannot harvest solar heat because sunlight is reflected by the daytime radiative cooler. In this study, a thermoelectric device that simultaneously harvests both radiative cooling and solar heating is presented. The essential component is a vertically placed thermoelectric module made of transparent thermoelectric thin films which allows radiatively cooled and solar heated surfaces to be co-planar. The outdoor and indoor measurements confirm that the device can harvest both radiative cooling and solar heating simultaneously during the day without offsetting each other, and can harvest radiative cooling at night. The co-planar design is an efficient method for simultaneously harvesting solar heating and radiative cooling, which could facilitate efficient energy harvesting and can be applied to a standalone power supply for off-grid sensor modules.

Eutectic growth process is usually characterized by the simultaneous coupled growth of two different solids within one uniform liquid phase, while fluid dynamics normally predicts the equiaxed shrinkage for floating viscous droplets on freezing. Here a decoupling effect was induced by the microgravity and containerless states aboard space station, which led to the independent dendrite growth of two eutectic phases within extremely undercooled liquid Nb-Si refractory alloy. The confronting fluid flow pattern driven by polar heterogeneous nucleation was found to stimulate the elongated surface deformation of alloy droplet at a high dendrite growth velocity.

Convenient, small-sized, and self-powered sensor units are easier to integrate, making them the future development direction of photodetectors. GaN materials with wide band gap are powerful candidates for UV detection, but most GaN based self-powered UV photodetectors have poor detection ability for the weak UV light, which limits their applications. This study reports a self-powered UV photodetector based on BaTiO₃/GaN heterojunction, which can detect ultra-weak UV light at a minimum of 0.68 nW/cm² by coupling the ferroelectric polarization, anti-reflection effect, and pyro-phototronic effect. The polarized BaTiO₃ thin film on the surface of GaN has an enhanced residual polarization field and generated anti-reflection effect, which can regulate the heterojunction band structure, suppress the dark current and minimize surface reflection of GaN. Simultaneously enhanced pyro-phototronic effect can significantly improve the response speed and responsivity of the device. The response time and recovery time of the device are as low as 8.794 ms and 5.018 ms. The maximum responsivity and detectivity are 88.206 mA/W and 7.392 × 10¹³ Jones, respectively, increased by 359% and 6065% compared to the device before polarization. Thanks to excellent material stability, the device has a sensitive and uniform response to continuously incident UV light. In addition, by simulating flame generation, it has been proven that the device has brilliant performance in flame detection and can achieve remote monitoring and fire warning functions. These results can promote the potential application of self-powered UV photodetectors based on BaTiO₃/GaN heterojunction in environmental monitoring and space communication fields.