Materials Horizons最新文献

Light-driven micromotors with multiple motion modes offer significantly greater application potential than single-mode micromotors. However, achieving such versatility often requires complex structural designs and precise light focusing on specific micromotor regions, presenting challenges for dynamic operations and microscale precisions. This study introduces programmable assemblies of anisotropic micromotors driven by the photothermal Marangoni effect, produced in bulk via microfluidic technology. Under full-area near-infrared (NIR) irradiation, the micromotor exhibits multiple motion modes, including translation and revolution, while micromotor assemblies display additional rotational motion. Self-assembly of these micromotors is highly controllable and programmable, enabling easy customization of assembled structures to achieve desired motion modes. These features are expected to advance the development of various intelligent self-propelling systems, using multimodal individual micromotors as foundational building blocks.

Integrated stretchable devices, containing soft modules, rigid modules, and encapsulation modules, are of potential use in implantable bioelectronics and wearable devices. However, such systems often suffer from electrical deterioration due to debonding failure at the connection between rigid and soft modules induced by severe stress concentration, limiting their practical implementation. Here, we report a highly conductive and adhesive bilayer interface that can reliably connect soft-soft modules and soft-rigid modules together by simply pressing without conductive pastes. This interface configuration features a nanoscale styrene-ethylene-butylene-styrene (SEBS) elastomer layer and a SEBS-liquid metal (LM) composite layer. The top SEBS layer enables a strong adhesion with different modules. The connections between soft-soft and soft-rigid modules can be stretched to high strains of 400% and 250%, respectively. Coupling electron tunneling through an ultrathin SEBS layer with LM particle networks in a SEBS-LM composite layer renders continuous pathways for electrical conductivity. Such a bilayer interface exhibits a strain-insensitive high conductivity (3.7 × 10⁵ S m^-1) over a wide strain range from 0 to 680%, which can be facilely fabricated in a self-organized manner by sedimentation of LM particles. We present a proof-of-concept demonstration of this bilayer interface as an electrode, interconnect, and self-solder for monitoring physiological signals.

Intelligent soft robots that integrate both structural color and controllable actuation ability have attracted substantial attention for constructing biomimetic systems, biomedical devices, and soft robotics. However, simultaneously endowing single-layer cholesteric liquid crystal elastomer (CLCE) soft actuators with reversible 3D deformability and vivid structural color changes is still challenging. Herein, a multi-responsive (force, heat and light) single-layer 3D deformable soft actuator with vivid structural color-changing ability is realized through the reduced graphene oxide (RGO) deposition-induced Janus structure of the CLCE using a precisely-controlled evaporation method. This single-layer structural color soft actuator can directly transform from a flat shape to a 3D shape through the photothermal effect. The introduction of RGO not only improves the mechanical properties and color saturation of the CLCE, but also endows it with near-infrared (NIR) light responsiveness via the photothermal effect. Moreover, due to the structural gradient resulting from the spontaneous deposition of RGO during the deswelling process, CLCEs show a stacked structure of the helical CLC layer and RGO-dispersed amorphous layer, which are capable of undergoing multiple reversible 3D deformations. The reversible deformations of biomimetic devices such as petal-like films imitating blooming flowers, thin strips imitating plant tendrils, and a cobweb-inspired catching net are achieved to demonstrate applications of this single-layer RGO/CLCE composite film. This work provides a simple strategy for the construction of single-layer 3D deformable soft actuators.

Neuromorphic and fully analog in-memory computations are promising for handling vast amounts of data with minimal energy consumption. We have synthesized and studied a series of homo-bimetallic silver purine MOFs (1D and 2D) having direct metal-metal bonding. The N7-derivatized purine ligands are designed to form bi-metallic complexes under ambient conditions, extending to a 1D or 2D metal-organic framework. Owing to the unique structural properties, these complexes exhibit voltage-controlled tunable ionic conductivity, thereby allowing us to demonstrate two-terminal non-volatile memory characteristics with a retention time of more than 10⁴ seconds, an I_LRS/I_HRS ratio of 10⁷, and volatile memory functionality. The atomistic computations corroborate the dominant influence of the organic framework on controlling ionic diffusion through porous channels. Finally, this capability to tune the ionic conduction in these MOFs was utilized to emulate synaptic plasticity, such as long-term potentiation/depression (LTP/LTD) and complex multi-terminal heterosynaptic plasticity. Attributes of spiking neural networks (SNNs) such as spike time-dependent plasticity (STDP) featuring a unique symmetric anti-Hebbian learning with an impressive STDP ratio of 109, and a paired-pulse facilitation (PPF) index of 60 were recorded, which is among the best for MOF-based neuromorphic devices. Overall, our technique of designing novel metal-organic frameworks with facile porous channels for controlled ionic motion could pave the way for a novel class of materials, allowing seamless integration for bio-synaptic electronic devices.

Ionogels are a promising solution to improve the functionality of electrochromic devices (ECDs) by solving issues related to traditional liquid electrolytes, such as volatility, toxicity, and leakage. However, manufacturing ionogels is complicated as it often involves cross-linking polymerization or chemical sol-gel processes, requiring large amounts of inorganic or polymeric gelators. This results in low ionic conductivity and poor ECD performance. This study demonstrates the fabrication of highly conductive supramolecular ionogels by directly solidifying an ionic liquid (IL) using a low-molecular-weight gelator with a very low content (5 wt%). The resulting ionogel, DBS-G, exhibited self-healing properties, high optical transmittance (>86%), and high ionic conductivity (3.12 mS cm^-1) comparable to the pure IL. When combined with a conjugated thiophene-based electrochromic polymer or by incorporating electrochromic viologen derivatives and ferrocene into the ionogel, the constructed five-or three-layer ECDs demonstrate electrochromic performance comparable to IL electrolyte and surpassing polymer gelator-based ionogels. They exhibit high optical contrast, rapid response, high coloring efficiency, good cycle stability, and can operate effectively in a broad temperature range from -25 °C to 80 °C. Furthermore, the adhesive properties of DBS-G facilitate the fabrication of flexible ECDs, which exhibit commendable electrochromic performance and cycle stability under bending conditions.

The functions of graphene have garnered significant attention in recent research. A profound understanding of the principles of temperature-dependent electromagnetic responses is crucial for guiding the design of advanced functional materials and devices. From this perspective, the thermally tailored mechanisms of polarization genes and conduction genes are emphasized. The synergistic effect between thermally tailored polarization relaxation and charge transport behaviors is revealed. More importantly, microwave absorption, electromagnetic shielding, and temperature sensing at elevated temperatures are discussed by customizing the conduction and polarization genes. The tunable variable-temperature electromagnetic performance enables the possibilities of diversified electromagnetic energy conversion. Three electromagnetic energy conversion devices for consuming waste electromagnetic energy are predicted, which can support the next generation of energy management and smart devices and promote efficient utilization of resources and sustainable development.

Electrochromic smart windows can realize intelligent photothermal regulation by applying a low potential, which is of great significance for energy-saving buildings and achieving low carbon emission. However, the dense structure of conventional metal oxide electrochromic materials limits ion transport efficiency, resulting in poor electrochromic properties. Here, we propose a surface crystal reconstruction strategy for cubic NiO through phosphorylation (P-NiO) to build energetic reactive interfaces and enhance the electrochromic performance. Theoretical simulations and experiments reveal that the introduction of PO₄ tetrahedra tailored the crystal structure of cubic NiO, which endows it with a large number of contiguous intracrystal cavities and unsaturated P-O bonds on the surface. The energetic reactive interface optimizes the transport path of OH^- and gets rid of the dependence on K⁺ in the adsorption process, thus improving the reaction kinetics of NiO. The P-NiO film delivers a large optical modulation (90.3%, at 500 nm), a high coloration efficiency (81.1 cm² C^-1, at 500 nm), and a fast switching speed (6 s and 7.2 s for coloring and bleaching processes). Furthermore, a model of an electrochromic smart window was fabricated based on the P-NiO film, using which a potential energy saving of 60.81 MJ m^-2 and CO₂ emission reduction of 11.98 kg m^-2 can be achieved in hot climate zones according to energy simulations. The in-depth insights gained into the fundamental mechanism of this surface crystal reconstruction strategy will facilitate the rational design of high-performance electrochromic and electrochemical materials.

Semiconducting ternary nitrides are a promising class of materials that have received increasing attention in recent years, but often show high free electron concentrations due to the low defect formation energies of nitrogen vacancies and substitutional oxygen, leading to degenerate n-type doping. To achieve non-degenerate behavior, we now investigate a family of amorphous calcium-zinc nitride (Ca-Zn-N) thin films. By adjusting the metal cation ratios, we demonstrate band gap tunability between 1.4 and 2.0 eV and control over the charge carrier concentration across six orders of magnitude, all while maintaining high mobilities between 5 and 70 cm² V^-1 s^-1. The combination of favorable electronic properties, low synthesis temperatures, and earth-abundant elements makes amorphous Ca-Zn-N highly promising for future sustainable electronics. Moreover, the successful synthesis of such materials, as well as their broad optical and electrical tunability, paves the way for a new class of tailored functional materials: amorphous nitride semiconductors - ANSs.

The exploration of van der Waals (vdW) materials, renowned for their unique optical properties, is pivotal for advanced photonics. These materials exhibit exceptional optical anisotropy, both in-plane and out-of-plane, making them an ideal platform for novel photonic applications. However, the manual search for vdW materials with giant optical anisotropy is a labor-intensive process unsuitable for the fast screening of materials with unique properties. Here, we leverage geometrical and machine learning (ML) approaches to streamline this search, employing deep learning architectures, including the recently developed Atomistic Line Graph Neural Network. Within the geometrical approach, we clustered vdW materials based on in-plane and out-of-plane birefringence values and correlated optical anisotropy with crystallographic parameters. The more accurate ML model demonstrates high predictive capability, validated through density functional theory and ellipsometry measurements. Experimental verification with 2H-MoTe₂ and CdPS₃ confirms the theoretical predictions, underscoring the potential of ML in discovering and optimizing vdW materials with unprecedented optical performance.

Heterogeneous single-atom catalysts are attracting substantial attention for selectively generating singlet oxygen (¹O₂). However, precise manipulation of atom coordination structures remains challenging. Here, the fine coordination structure of iron single-atom carbon-nitride catalysts (Fe-CNs) was manipulated by precisely tuning the heating rate with 1 °C min^-1 difference. Multiple techniques in combination with density functional theory (DFT) calculations reveal that FeN₆ coordination sites with high Fe spin states promote the adsorption, electron transfer, and dissociation of peroxymonosulfate (PMS), resulting in nearly 100% selection of ¹O₂ generation. A lamellar single atom catalytic membrane is constructed, exhibiting high permeance, high degradation, high-salinity resistance and sustained operation stability. This work provides ideas for regulating spin states of the metal site to fabricate catalysts with selective ¹O₂ generation for membrane separation and environment catalysis applications.