Materials Horizons最新文献

Three-dimensional (3D) printing, also known as additive manufacturing, is capable of transforming computer-aided designs into intricate structures directly and on demand. This technology has garnered significant attention in recent years. Among the various approaches, digital light processing (DLP) 3D printing, which utilizes polymers or prepolymers as the ink, has emerged as the leading new technology, driven by high demand across diverse fields such as customized production, healthcare, education, and art design. DLP 3D printing technology employs cured slices as molding units and is recognized for its potential to achieve both high printing speed and resolution. Recent insights into the DLP printing process highlight its inherent interface transformations between liquid and solid states. This review summarizes key aspects of the printing process, speed, precision, and material diversity optimization, from the view of interfacial interactions between solid and liquid phases which are influenced by resin formation, curing surfaces and light source properties. These interactions include those at the liquid resin-UV pattern interface, the cured structure-curing surface interface, the liquid resin-curing surface interface, and the liquid resin-cured structure interface, each contributing to the unique characteristics of the printed results. Finally, this review addresses the current challenges and limitations of DLP 3D printing, providing valuable insights for future improvements and guiding potential innovations in the field.

Polymer dielectrics are the key materials in next-generation electrical power systems. However, they usually suffer from dramatic deterioration of capacitive performance at high temperatures. In this work, we demonstrate that polymethylsesquioxane (PMSQ) microspheres with a unique organic-inorganic hybrid structure can remarkably enhance the energy storage performance of a typical high-temperature dielectric polymer polyetherimide (PEI). Compared with traditional ceramic fillers, there exists -CH₃ on the surface of PMSQ microspheres, which results in good compatibility between PMSQ and PEI. In addition, the PMSQ microspheres with excellent insulating properties can effectively block the charge transport, yielding significantly enhanced breakdown and energy storage performance. Consequently, the PEI based composite film with 5 wt% PMSQ microspheres exhibits ultrahigh energy storage densities of 12.83 J cm^-3 and 9.40 J cm^-3 with an efficiency (η) above 90% at 150 °C and 200 °C, respectively, which are 10.5 and 50.5 times those of the pure PEI film. This work demonstrates that microspheres with an organic-inorganic hybrid structure are excellent candidates for enhancing the high-temperature performance of polymer dielectrics, and these PMSQ/PEI composite films have huge potential for application in high-temperature film capacitors.

Endowing soft and long-range stretchable elastomers with exceptional strength, resilience, and ion-conductivity is crucial for high-performance flexible sensors. However, achieving this entails significant challenges due to intrinsic yet mutually exclusive structural factors. In this work, a series of self-reinforcing ion-conductive elastomers (SRICEs) is thus designed to meet the advanced but challenging requirements. The SRICEs behave like a soft/hard dual-phase separated micro-structure, which is optimized through a straightforward preferential assembly strategy (PAS) to ensure that the subsequently introduced ions are locked in the soft phase. Meanwhile, the interaction between ions and soft segments is meticulously tailored to achieve self-reinforcement through strain-induced crystallization. Consequently, an outstanding ultimate strength of approximately ∼51.0 MPa and an exceptional instant resilient efficiency of ∼92.9% are attained. To the best knowledge of the authors, these are the record-high values achieved simultaneously in one ion-conductive elastomer. Furthermore, the resultant toughness of ∼202.4 MJ m^-3 is significantly higher, while the modulus of ∼5.0 MPa is lower than that of most reported robust ion-conductive elastomers. This unique combination of properties makes it suitable for advanced flexible applications, e.g. grid-free position recognition sensors. This work provides guidance for designing soft yet robust ion-conductive elastomers and optimizing their mechanical properties.

Neuromorphic computation has emerged as a potential alternative to subvert the von Neumann bottleneck issue in conventional computing. In this context, the development of resistive switching-based memristor devices mimicking various synaptic functionalities has engendered paramount attention. Here, we report a triradical-containing trinuclear Pd(II) cluster with a cyclohexane-like framework constituted by the Pd-Se coordination motif displaying facile memristor property with neuromorphic functionality as a thin-film device. The metal-ligand complex (complex 1) possessed an S_t = 1/2 ground state by experiencing a spin-frustrated-type magnetic coupling phenomenon amongst the three ligand-based organic radicals (S_R = 1/2), coordinated to the Pd(II) ions. Three reversible one-electron reduction waves countered with a one-electron and one two-electron reversible oxidation waves were noticed in the cyclic voltammogram of the complex, confirming electrons accepting and releasing capacity of the complex at low potentials, i.e., within +0.2 V to -1.1 V. Employing the radical-containing complex 1 as the active thin-film sandwiched between two orthogonal electrodes, resistive switching based memristor property with biological synaptic actions were successfully emulated. Intriguingly, the artificial neural network (ANN) simulated efficient pattern recognition demonstrated using the recorded potentiation and depression curves from the device, which is a step ahead for the hardware realization of neuromorphic computing. The performance of the ANN on MNIST data with reduced image resolution has further been evaluated. Density functional theory (DFT)-based theoretical calculation predicted that the spin-polarized electronic transmission substantiated the memristive property in the neutral complex 1.

Auxetic materials with multifunctional properties are highly sought after for application in modern nano-devices. However, the majority of reported inorganic auxetic materials exhibit low negative Poisson's ratios (NPR), poor flexibility, and limited functionality. In this study, we employ density-functional-theory (DFT) first-principles simulations to design a series of two-dimensional (2D) metal-organic frameworks (MOFs) M₂C₄X₄ (M = Cu, Ag, Au; X = O, S, NCN) that display intriguing auxetic behavior, superior flexibility and appropriate photocatalytic water-splitting properties. These M₂C₄X₄ MOFs are assembled from carbon tetragon motifs and exist in both cis- and trans-isomer forms, with the NPR ranging from -0.17 to -0.90. Notably, trans-Cu₂C₄(NCN)₄ exhibits a high NPR of -0.90, while cis-Cu₂C₄(NCN)₄ achieves an NPR of -0.67. Both isomers demonstrate excellent flexibility, characterized by ultra-low Young's modulus and high fracture strengths. Furthermore, their direct band gaps, strong light-harvesting capabilities, and long excited-state lifetimes make them promising candidates for the photocatalytic oxygen evolution reaction in water. These results provide a viable strategy for the design and synthesis of novel optoelectronic multifunctional materials.

Organic luminogens (OLs) exhibiting piezochromic (PC) properties have drawn much attention owing to their great application potentials. Both mechanical grinding (MG) and hydrostatic pressures (HP) can induce PC behaviors of OLs, and it is highly desirable to combine the two strategies to study the PC properties of OLs for comprehensively exploring their application scopes and deeply understanding the intrinsic PC mechanisms. In this work, four coumarin derivatives with different substituents at 3- or 4-positions are designed and synthesized to investigate their PC properties by MG and under HP. By MG, two materials show PL shifts, and the PL of the other two molecules barely change. In contrast, under HP, these molecules all exhibit PL shifts, but with different pressure coefficients. In addition, they show different reversibility of PL change after releasing HP. The different molecular conformation and packing structure changing manners of the materials, indicated by single-crystal and powder X-ray diffraction patterns, and in situ PL lifetime analysis, are anticipated to induce distinct PC behaviors upon disparate force stimulus. Our study indicates that fine-tuning the functionalization position of coumarin derivatives is a powerful strategy to engineer their molecular conformation and packing structures, thus developing versatile pressure-responsive OLs.

Wound healing in diabetes is a complex physiological process with risks of ulceration and amputation. Real-time monitoring and treatment of diabetic wounds is an effective prevention of further deterioration. Herein, a multifunctional dressing is developed by encapsulating europium-containing bioactive glass (EuBG) and MoO_3-x in a biocompatible sodium alginate (SA) dressing (MoO_3-x-EuBG-SA), aiming to simultaneously monitor the wound pH value and hydrogen peroxide (H₂O₂) concentration, establish an anti-inflammatory microenvironment, and promote wound healing. The pH-responsive fluorescence quenching effect of EuBG contributes to visible monitoring of pH values, and MoO_3-x enables high responsiveness and accurate colorimetric indication of H₂O₂ variability to understand the dynamic wound status. Then, these fluorescent and colorimetric changes can be captured using a smartphone and transformed into signals for wound pH values and H₂O₂ concentrations, enabling rapid and convenient real-time assessment of wound dynamics. Furthermore, the MoO_3-x-EuBG-SA dressing can reduce inflammation and promote the proliferation, differentiation, and migration of fibroblasts and endothelial cells in vitro with the help of the released bioactive Si, Ca, and Mo ions. Notably, the MoO_3-x-EuBG-SA dressing exhibits excellent abilities to monitor a wound microenvironment and immune regulation and promote diabetic wound healing in vivo. Overall, the multifunctional dressing has great potential for managing diabetic wounds and promoting wound healing.

External field driven fluid manipulation, in particular electric field, offers the advantages of real-time control and exceptional flexibility, rendering it highly promising for applications in microfluidic devices, liquid separation and energy catalysis. However, it is still challenging for controlled liquid transport and fine control of droplet splitting. Herein, we demonstrate a strategy to achieve direction-controlled liquid transport and fine droplet splitting on an anisotropic groove-microstructured electrode surface via an electrically switched asymmetric interface. The balance of asymmetric capillary force generated by microstructures and electro-capillary force is critical in determining directional liquid transport and fine droplet splitting. Asymmetric bubbles generated by liquid electrolysis form an asymmetric liquid-gas-solid interface and result in gradient liquid wetting behavior on the two neighboring electrode surfaces. The electric field further enhances the asymmetric wetting of a liquid droplet on the electrode surface, exhibiting electric field direction-dependent motion. Moreover, the groove-microstructured electrode surface can strengthen the liquid droplet anisotropic wetting and correspondingly refine the volume range of the splitting sub-droplet. Even unidirectional/bidirectional liquid droplet transport can be controlled in collaboration with the asymmetric groove-microstructure and electric field. Thus, this work provides a new route for liquid transport and droplet splitting, showing great potential in controllable separation, microreaction and microfluidic devices.

The development of polymer dielectrics with both high energy density and low energy loss is a formidable challenge in the area of high-temperature dielectric energy storage. To address this challenge, a class of polymers (Parylene F) are designed by alternating fluorinated aromatic rings and vinyl groups in the polymer chain to confine the conjugating sequence and broaden the bandgap with the fluorine effect. The target films with desired thickness, ultra-high purity, and a wide bandgap are facilely fabricated by a one-step chemical vapor deposition (CVD) technique from monomers. The symmetric and bulky aromatic structures exhibit high crystalline performance and excellent stability at high temperature. The presence of strongly electronegative fluorine atoms effectively enhances bandgap and electron trapping capability, which effectively reduces the conduction loss as well as the possibility of breakdown at high temperatures. CVD technology avoids the post-processing film-forming process, ensuring the fabrication of thin films with high quality. These benefits allow Parylene F films to effectively store electrical energy at temperature up to 150 °C, exhibiting a record discharged energy density of 2.92 J cm^-3 at charge-discharge efficiency exceeding 90%. This work provides a new idea for the design and synthesis of all-organic polymer dielectric films for high temperature applications.

Flexible and stretchable strain sensors have garnered significant interest due to their potential applications in various fields including human health monitoring and human-machine interfaces. Previous studies have shown that strain sensors based on microcracks can exhibit both high sensitivity and a wide sensing range by manipulating the opening and closing of randomly generated cracks within conductive thin films. However, the uncontrolled nature of microcrack formation can cause a drift in the sensor's performance over time, affecting its accuracy and reliability. In this study, by pre-defining the cracks, we introduce a novel resistive strain sensor with high sensitivity, excellent linearity, an ultra-low detection limit, and robustness against off-axis deformation. The sensor operates on a simple mechanism involving the modulation of ohmic contact within intricately designed conductive serpentine curves, which are encapsulated by pre-stretched thin films. This design facilitates a high gauge factor of 495, exceptional linearity (R² > 0.98), and an ultra-low detection threshold of 0.01% strain. Moreover, it maintains performance integrity during off-axis deformations such as bending and twisting, features that are indispensable for accurately monitoring human motion. To explore practical applications, a driving scenario was simulated where a sensor array was positioned on the driver's neck. The sensor output was analyzed using machine learning algorithms to successfully determine the presence of driver fatigue. This demonstration underlines the potential of our sensor technology in applications ranging from healthcare monitoring to wearable biomechanical systems and human-machine interfaces.