3D printing of inorganic nanomaterials by photochemically bonding colloidal nanocrystals

3D Conformal Curvy Electronics: Design, Fabrication, and Application

Owing to their excellent conformability and functional advantages derived from spatially induced structures, 3D conformal curvy electronics have garnered attention for their emerging applications in biomedical healthcare, soft machines, curvy imagers, etc. In this perspective, the historical evolution of 3D conformal curvy electronics is summarized, with representative examples highlighted and developmental trends outlined. The design strategies of 3D conformal curvy electronics are discussed across materials, structures, interfaces, and conformability assessment. Subsequently, diverse fabrication technologies are reviewed, including direct fabrication, conformal transfer printing, and conformal shape reconfiguration. Afterward, the typical applications of 3D conformal curvy electronics are presented, classified by integration with biological tissues, machines, and function-engineered curvy surfaces. Finally, the existing challenges and potential research directions are provided for further exploration.

Pushing the Frontiers: Artificial Intelligence (AI)-Guided Programmable Concepts in Binary Self-Assembly of Colloidal Nanoparticles

Colloidal nanoparticle self-assembly is a key area in nanomaterials science, renowned for its ability to design metamaterials with tailored functionalities through a bottom-up approach. Over the past three decades, advancements in nanoparticle synthesis and assembly control methods have propelled the transition from single-component to binary assemblies. While binary assembly has been recognized as a significant concept in materials design, its potential for intelligent and customized assembly has often been overlooked. It is argued that the future trend in the assembly of binary nanocrystalline superlattices (BNLSs) can be analogous to the '0s' and '1s' in computer programming, and customizing their assembly through precise control of these basic units could significantly expand their application scope. This review briefly recaps the developmental trajectory of nanoparticle assembly, tracing its evolution from simple single-component assemblies to complex binary co-assemblies and the unique property changes they induce. Of particular significance, this review explores the future prospects of binary co-assembly, viewed through the lens of 'AI-guided programmable assembly'. Such an approach has the potential to shift the paradigm from passive assembly to active, intelligent design, leading to the creation of new materials with disruptive properties and functionalities and driving profound changes across multiple high-tech fields.

3D Patterning of Perovskite Quantum Dots via Direct In Situ Femtosecond Laser Writing

Perovskite quantum dots (PQDs) exhibit remarkable optical properties, making them highly promising for next-generation display technologies. However, achieving precise PQDs patterning is hindered by significant challenges, including the inability to achieve true three-dimensional (3D) structuring and the risk of damaging the delicate perovskite crystal lattice. Existing methods struggle to achieve true 3D structuring while preserving the optical integrity. This study introduces an in situ patterning technique using direct laser writing (DLW). By leveraging the nonlinear absorption properties of femtosecond lasers, thiol-Ene photopolymerization is triggered, transforming perovskite precursors into complex fluorescent structures. Unlike conventional methods, this precursor-based approach minimizes laser power requirements and prevents quantum dot degradation caused by high-energy exposure. It enables precise, scalable fabrication while maintaining the structural and optical stabilities of PQDs. This innovation provides a robust platform for developing advanced display technologies, optoelectronic devices, and miniaturized on-chip systems, paving the way for future high-performance applications.

Patterning on Living Tardigrades

Micro/nanofabrication techniques have revolutionized modern photonics and electronics. However, conventional methods remain incompatible with living organisms due to inherent constraints including nonconformal coating, radiation damage, and toxic solvent requirements. Here, we present ice lithography for direct fabrication of micro/nanoscale patterns on the surfaces of tardigrades in their cryptobiotic state. Remarkably, upon rehydration the tardigrades revive, retaining the patterns on their surfaces. By precisely controlling parameters such as ice thickness, beam energy, and substrate properties, this method minimizes sample damage while achieving patterns as small as 72 nm. These patterns remain stable even after stretching, solvent immersion, rinsing, and drying. This approach provides new insights into tardigrades' resilience and has potential applications in cryopreservation, biomedicine, and astrobiology. Furthermore, integrating micro/nanofabrication techniques with living organisms could catalyze advancements in biosensing, biomimetics, and living microrobotics.

Magnetically Switchable Adhesive Millirobots for Universal Manipulation in both Air and Water

Magnetic soft robots with multimodal locomotion have demonstrated significant potential for target manipulation tasks in hard-to-reach spaces in recent years. Achieving universal manipulation between robots and their targets requires a nondestructive and easily switchable interaction with broad applicability across diverse targets. However, establishing versatile and dynamic interactions between diverse targets and robotic systems remains a significant challenge. Herein, a series of magnetic millirobots capable of universal target manipulation with magnetically switchable adhesion is reported. Through two-photon lithography-assisted molding, magnetic soft double-reentrant micropillar arrays with liquid repellency are fabricated on the robots. These micropillar arrays can serve as switchable adhesion units for the millirobots to effectively manipulate targets of various geometries (0D, 1D, 2D, and 3D) in both air and water. As proof-of-concept demonstrations, these adhesive robots can perform various complex tasks, including circuit repair, mini-turbine assembly, and high-speed underwater rotation of the turbine machine. This work may offer a versatile approach to magnetic manipulation of non-magnetic objects through amphibious adhesion, emerging as a new paradigm in robotic manipulation.

Construction of a Biomimetic Tubular Scaffold Inspired by Sea Sponge Structure: Sponge-Like Framework and Cell Guidance

Engineering hollow fibers with precise surface microstructures is challenging; yet, essential for guiding cells alignment and ensuring proper vascular tissue function. Inspired by Euplectella sponges, a novel strategy to engineer biomimetic hollow fibers with spiral surface microstructures is developed. Using oxidized bacterial cellulose, bacterial cellulose, and polydopamine, a "brick-and-mortar" scaffold is created through precise shear control during microfluidic coaxial spinning. The scaffold mimics natural extracellular matrices, providing mechanical stability and supporting cell growth. In vitro studies show successful co-culture of endothelial cells (ECs) and smooth muscle cells (SMCs), with SMCs aligning along spiral surface microstructures and ECs forming a confluent inner layer. In vivo implantation confirms biocompatibility, biodegradability, and low immunogenicity. This Euplectella-inspired scaffold presents a promising approach for vascular tissue engineering and regenerative medicine.

Connecting the dots for cooling

Semiconductor particles are fused to make a thermoelectric cooler.

Multi-Physical Lattice Metamaterials Enabled by Additive Manufacturing: Design Principles, Interaction Mechanisms, and Multifunctional Applications

Lattice metamaterials emerge as advanced architected materials with superior physical properties and significant potential for lightweight applications. Recent developments in additive manufacturing (AM) techniques facilitate the manufacturing of lattice metamaterials with intricate microarchitectures and promote their applications in multi-physical scenarios. Previous reviews on lattice metamaterials have largely focused on a specific/single physical field, with limited discussion on their multi-physical properties, interaction mechanisms, and multifunctional applications. Accordingly, this article critically reviews the design principles, structure-mechanism-property relationships, interaction mechanisms, and multifunctional applications of multi-physical lattice metamaterials enabled by AM techniques. First, lattice metamaterials are categorized into homogeneous lattices, inhomogeneous lattices, and other forms, whose design principles and AM processes are critically discussed, including the benefits and drawbacks of different AM techniques for fabricating different types of lattices. Subsequently, the structure-mechanism-property relationships and interaction mechanisms of lattice metamaterials in a range of physical fields, including mechanical, acoustic, electromagnetic/optical, and thermal disciplines, are summarized to reveal critical design principles. Moreover, the multifunctional applications of lattice metamaterials, such as sound absorbers, insulators, and manipulators, sensors, actuators, and soft robots, thermal management, invisible cloaks, and biomedical implants, are enumerated. These design principles and structure-mechanism-property relationships provide effective design guidelines for lattice metamaterials in multifunctional applications.

Tailorable Fluorescent Perovskite Quantum Dots for Multiform Manufacturing via Two-Step Thiol-Ene Click Chemistry

In practical applications, fluorescent perovskite quantum dots (PQDs) must exhibit high efficiency, stability, and processibility. So far, it remains a challenge to synthesize PQDs with stable dispersibility in tailorable monomers both before and after photocuring. In this work, a novel strategy of UV-induced two-step thiol-ene "click chemistry" is proposed to prepare PQDs with these attributes. The first step aims to epitaxially grow a shell around the PQD core to ensure stable dispersibility in a thiol-ene monomer solution. The second step is to achieve stable dispersibility in the photocured thiol-ene matrixes for multiform manufacturing processes. The tailorable PQDs (T-PQDs) not only have the highest photoluminescence quantum yield (PLQY) to ≈100% for green emission and over 96% for red emission, but also exhibit remarkable stability under severe conditions, including "double 85" aging, water exposure, and mechanical stress. Moreover, their exceptional processability allows for various processing techniques, including slot-die coating, inkjet printing, direct-laser writing, UV-light 3D printing, nanoimprinting, and spin coating. The high efficiency and stability of T-PQDs facilitate their multiform manufacturing for a wide range of applications.

Bio-Informed Porous Mineral-Based Composites

Certain biominerals, such as sea sponges and echinoderm skeletons, display a fascinating combination of mechanical properties and adaptability due to the well-defined structures spanning various length scales. These materials often possess high density normalized mechanical properties because they contain well-defined pores. The density-normalized mechanical properties of synthetic minerals are often inferior because the pores are stochastically distributed, resulting in an inhomogeneous stress distribution. The mechanical properties of synthetic materials are limited by the degree of structural and compositional control currently available fabrication methods offer. In the first part of this review, examples of structural elements nature uses to impart exceptional density normalized Young's moduli to its porous biominerals are showcased. The second part highlights recent advancements in the fabrication of bio-informed mineral-based composites possessing pores with diameters that span a wide range of length scales. The influence of the processing of mineral-based composites on their structures and mechanical properties is summarized. Thereby, it is aimed at encouraging further research directed to the sustainable, energy-efficient fabrication of synthetic lightweight yet stiff mineral-based composites.

3D-Printed High-Entropy Alloy Nanoarchitectures

System miniaturization is a key driver in developing nanoelectromechanical systems, sensors, and microchips. To enhance reliability and extend operational lifetimes, high-entropy alloys (HEAs) have emerged as promising materials due to their exceptional mechanical robustness and thermal stability. These advantageous properties are predominantly demonstrated in bulk HEA forms; however, research on small-dimensional HEAs is largely confined to nanoparticles, nanopillars, and thin films, limiting their broader applications in nanodevice systems. This study introduces nanoarchitectured HEAs that exhibit remarkable mechanical and thermal properties. Using a custom-designed 3D nanoprinter, HEA nanoparticles are printed in situ into complex nanoarchitectures, enabling flexible elemental combinations and freeform 3D geometries. Structural dimensions and grain size are precisely controlled as design parameters to synergistically leverage the benefits of alloying, size scaling, and architectural design. The resulting 3D-printed HEA nanoarchitectures demonstrate ultrahigh strength (≈4 GPa), outstanding toughness, and exceptional thermal stability. These properties position nano-architectured HEAs as a novel class of materials suitable for high-stress, high-toughness applications in small-dimensional devices. By combining the versatility of 3D nanoprinting with the expansive alloy design space of HEAs, this approach paves the way for their potential integration into future nanodevices.

Transforming achiral semiconductors into chiral domains with exceptional circular dichroism

Highly concentrated solutions of asymmetric semiconductor magic-sized clusters (MSCs) of cadmium sulfide, cadmium selenide, and cadmium telluride were directed through a controlled drying meniscus front, resulting in the formation of chiral MSC assemblies. This process aligned their transition dipole moments and produced chiroptic films with exceptionally strong circular dichroism. G-factors reached magnitudes as high as 1.30 for drop-cast films and 1.06 for patterned films, approaching theoretical limits. By controlling the evaporation geometry, various domain shapes and sizes were achieved, with homochiral domains exceeding 6 square millimeters that transition smoothly between left- and right-handed chirality. Our results uncovered fundamental relationships between meniscus deposition processes, the alignment of supramolecular filaments and their MSC constituents, and their connection to emergent chiral properties.

Frontiers in fluorescence imaging: tools for the in situ sensing of disease biomarkers

Fluorescence imaging has been recognized as a powerful tool for the real-time detection and specific imaging of biomarkers within living systems, which is crucial for early diagnosis and treatment evaluation of major diseases. Over the years, significant advancements in this field have been achieved, particularly with the development of novel fluorescent probes and advanced imaging technologies such as NIR-II imaging, super-resolution imaging, and 3D imaging. These technologies have enabled deeper tissue penetration, higher image contrast, and more accurate detection of disease-related biomarkers. Despite these advancements, challenges such as improving probe specificity, enhancing imaging depth and resolution, and optimizing signal-to-noise ratios still remain. The emergence of artificial intelligence (AI) has injected new vitality into the designs and performances of fluorescent probes, offering new tools for more precise disease diagnosis. This review will not only discuss chemical modifications of classic fluorophores and in situ visualization of various biomarkers including metal ions, reactive species, and enzymes, but also share some breakthroughs in AI-driven fluorescence imaging, aiming to provide a comprehensive understanding of these advancements. Future prospects of fluorescence imaging for biomarkers including the potential impact of AI in this rapidly evolving field are also highlighted.

Multiphoton and Harmonic Imaging of Microarchitected Materials

Microadditive manufacturing has revolutionized the production of complex, nano- to microscale components across various fields. This work investigates two-photon (2P) and three-photon (3P) fluorescence imaging, as well as third-harmonic generation (THG) microscopy, to examine periodic microarchitected lattice structures fabricated using multiphoton lithography (MPL). By immersing the structures in refractive index matching fluids, we demonstrate high-fidelity 3D reconstructions of both fluorescent structures using 2P and 3P microscopy as well as low-fluorescence structures using THG microscopy. These results show that multiphoton fluorescence (MPF) imaging offers reduced signal decay with respect to depth compared to single-photon techniques in the examined structures. We further demonstrate the ability to nondestructively identify intentional internal modifications of the structure that are not immediately visible with scanning electron microscope (SEM) images and compression-induced fractures, highlighting the potential of these techniques for quality control and defect detection in microadditively manufactured components.

Photothermal Laser Printing of Sub-Micrometer Crystalline ZnO Structures

During light-driven 3D additive manufacturing, an object represented in digital form is initially translated into a spatial distribution of light intensity (sequentially or in parallel), which then results in a spatial material distribution. To date, this process typically proceeds by photoexcitation of small functional molecules, leading to photochemically induced crosslinking of soft materials. Alternatively, thermal triggers can be employed, yet thermal processes are often slow and provide only low spatial localization. Nevertheless, sub-micrometer ZnO structures for functional microelectronic devices have recently been laser-printed. Herein, the photothermal laser-printing of ZnO is advanced by i) introducing single-crystalline rather than amorphous sub-micrometer ZnO shapes that crystallize in the hexagonal ZnO wurtzite structure, ii) employing dimethyl sulfoxide (DMSO) instead of water, enabling higher local process temperatures without micro-bubble formation, and iii) using substrates tailored for light absorption and heat management, resolving the challenge of light to heat conversion. Finally, the herein-demonstrated ZnO printing requires no post-processing and is a cleanroom-free technique for the fabrication of crystalline semiconductors.

3D Nanofabrication via Directed Material Assembly: Mechanism, Method, and Future

Fabrication of complex three-dimensional (3D) structures at nanoscale is the core of nanotechnology, as it enables the creation of various micro-/nano-devices such as micro-robots, metamaterials, sensors, photonic devices, etc. Among most 3D nanofabrication strategies, the guided material assembly, an efficient bottom-up approach capable of directly constructing designed structures from precise integration of material building blocks, possesses compelling advantages in diverse material compatibility, sufficient driving forces, facile processing steps, and nanoscale resolution. In this review, we focus on assembly-based fabrication methods capable of creating complex 3D nanostructures (instead of periodic or 2.5D-only structures). Recent advances are classified based on the different assembly mechanisms, i.e., assembly driven by chemical reactions, physical interactions, and the synergy of multiple microscopic interactions. The design principles of representative fabrication strategies with an emphasis on their respective advantages, e.g., structural design flexibility, material compatibility, resolution, or applications are analyzed. In the summary and outlook, existing challenges, as well as possible paths to solutions for future development are reviewed. We believe that with recent advances in assembly-based nanofabrication strategies, 3D nanofabrication has achieved tremendous progress in resolution, material generality, and manufacturing cost, for it to make a greater impact in the near future.

Scalable Macroscopic Engineering from Polymer-Based Nanoscale Building Blocks: Existing Challenges and Emerging Opportunities

Natural materials exhibit exceptional properties due to their hierarchical structures spanning from the nano- to the macroscale. Replicating these intricate spatial arrangements in synthetic materials presents a significant challenge as it requires precise control of nanometric features within large-scale structures. Addressing this challenge depends on developing methods that integrate assembly techniques across multiple length scales to construct multiscale-structured synthetic materials in practical, bulk forms. Polymers and polymer-hybrid nanoparticles, with their tunable composition and structural versatility, are promising candidates for creating hierarchically organized materials. This review highlights advances in scalable techniques for nanoscale organization of polymer-based building blocks within macroscopic structures, including block copolymer self-assembly with additive manufacturing, polymer brush nanoparticles capable of self-assembling into larger, ordered structures, and direct-write colloidal assembly. These techniques offer promising pathways toward the scalable fabrication of materials with emergent properties suited for advanced applications such as bioelectronic interfaces, artificial muscles, and other biomaterials.

Direct Photopatterning of Colloidal Quantum Dots with Electronically Optimized Diazirine Cross-Linkers

Colloidal quantum dots (QDs) with a wide color gamut and high luminescent efficiency are promising for next-generation electronic and photonic devices. However, precise and scalable patterning of QDs without degrading their properties and their integration into commercially relevant devices, such as digitally addressable QD light-emitting diode (QLED) displays, remain challenging. Here, we develop electronically optimized diazirine-based cross-linkers for nondestructive, direct photopatterning of QDs and, ultimately, building the active-matrix QLED displays. The key to the cross-linker design is the introduction of electron-donating substituents that permit the formation of ground-state singlet carbenes for air-stable and benign QD photopatterning. Under ambient conditions, these cross-linkers enable the patterning of heavy metal-free QDs at a resolution of over 13,000 pixels per inch using commercial i-line photolithography. The patterned QD layers fully preserved their optical and optoelectronic properties. Pixelated electroluminescent devices with patterned InP/ZnSe/ZnS QD layers show a peak external quantum efficiency of 15.3% and a maximum luminance of about 40,000 cd m-2, outperforming those made by existing QD patterning approaches. We further show the seamless integration of patterned QLEDs with thin-film transistor circuits and the fabrication of dual-color active-matrix displays. These results underscore the importance of designing photochemistry for QD patterning, and promise the implementation of direct photopatterning methods in manufacturing commercial QLED displays and other integrated QD device platforms.

Operando Colorations from Real-Time Growth of 3D-Printed Nanoarchitectures

While artificial 3D nanostructures can generate precise and flexible coloration, their real-time color changes during 3D nanoprinting remain unexplored owing to the inherent challenges of in situ transient measurements and observations. In this study, a 3D-printing system which supports the operando observation/measurement of the color dynamics of subwavelength metallic nanoarchitectures fabricated in real time is developed and evaluated. During 3D printing, the dimensions and geometries of the 3D nanostructures grow over time, producing a large library of optical spectra associated with real-time color changes. Only a timer is needed to define the expected colors from a single 3D print run. Fin-like nanostructures are used to toggle colors based on the polarization effect and produce color gradients. Based on structural coloration, nanoarchitectures are designed and printed to animate desired color patterns. Moreover, the resulting color dynamics can also serve as an operando identifier for real-time structural information during 3D nanoprinting. A single print run enables the efficient creation of a comprehensive library of desired colorations owing to the flexibility in time-dependent controllability and 3D geometries at the subwavelength scale. 3D nanoprinted plasmonic structures exhibiting time-varying colorations (4D printing of colors) uniquely redefines the coloring stategy, offering considerable potential for numerous applications.

Editorial for the Topic on Advanced Laser Fabrication Technologies for Cross-Field Applications

The field of laser fabrication technologies has seen remarkable advancements in recent years [...].

Controlling the thermally-driven crystallization of DNA-coated nanoparticles with formamide

DNA-coated nanoparticles, also known as programmable atom equivalents (PAEs), facilitate the construction of materials with nanoscopic precision. Thermal annealing plays a pivotal role by controlling DNA hybridization kinetics and thermodynamics, which ensures the formation of intended structures. While various design handles such as particle size, DNA design, and salt concentration influence the stability of the DNA duplexes linking PAEs in a lattice, their influence on the system's melting temperature (Tm) often follows complicated trends that make rational tuning of self-assembly challenging. In this work, the denaturant formamide is used to precisely tune the thermal response of PAEs. Our results reveal a clear and predictable trend in the PAEs' response to formamide, enabling rational control over the Tm of a diverse set of PAE systems. Unlike adjustments made through alterations to PAE design or solution parameters such as ionic strength, formamide achieves its temperature shift without impacting the kinetics of assembly. As a result, PAEs can be rapidly crystallized at ambient temperatures, producing superlattices with similar quality to PAE crystals assembled through standard protocols that use higher temperatures. This study therefore positions formamide as a useful tool for enhancing the synthesis of complex nanostructures under mild conditions.

Beyond hype: unveiling the Real challenges in clinical translation of 3D printed bone scaffolds and the fresh prospects of bioprinted organoids

Bone defects pose significant challenges in healthcare, with over 2 million bone repair surgeries performed globally each year. As a burgeoning force in the field of bone tissue engineering, 3D printing offers novel solutions to traditional bone transplantation procedures. However, current 3D-printed bone scaffolds still face three critical challenges in material selection, printing methods, cellular self-organization and co-culture, significantly impeding their clinical application. In this comprehensive review, we delve into the performance criteria that ideal bone scaffolds should possess, with a particular focus on the three core challenges faced by 3D printing technology during clinical translation. We summarize the latest advancements in non-traditional materials and advanced printing techniques, emphasizing the importance of integrating organ-like technologies with bioprinting. This combined approach enables more precise simulation of natural tissue structure and function. Our aim in writing this review is to propose effective strategies to address these challenges and promote the clinical translation of 3D-printed scaffolds for bone defect treatment.

Ultrafast Laser 3D Nanolithography of Fiber-Integrated Silica Microdevices

Fiber-integrated micro/nanostructures play a crucial role in modern industry, mainly owing to their compact size, high sensitivity, and resistance to electromagnetic interference. However, the three-dimensional manufacturing of fiber-tip functional structures beyond organic polymers remains challenging. It is essential to construct fiber-integrated inorganic silica with designed functional nanostructures for microsystem applications. Here, we develop a strategy for the 3D nanolithography of fiber-integrated silica from hybrid organic-inorganic materials by ultrafast laser-induced multiphoton absorption. Without silica nanoparticles and polymer additives, the acrylate-functionalized precursors can be locally cross-linked through a nonlinear effect. Followed by annealing at low temperature, the as-printed micro/nanostructures are transformed to high-quality silica with sub-100 nm resolution. Silica microcantilever probes and microtoroid resonators are directly integrated onto the optical fiber, showing strong thermal stability and quality factors. This work provides a promising strategy for fabricating desired fiber-tip silica micro/nanostructures, which is helpful for the development of integrated functional device applications.

Capillary trapping of various nanomaterials on additively manufactured scaffolds for 3D micro-/nanofabrication

High-precision additive manufacturing technologies, such as two-photon polymerization, are mainly limited to photo-curable polymers and currently lacks the possibility to produce multimaterial components. Herein, we report a physically bottom-up assembly strategy that leverages capillary force to trap various nanomaterials and assemble them onto three-dimensional (3D) microscaffolds. This capillary-trapping strategy enables precise and uniform assembly of nanomaterials into versatile 3D microstructures with high uniformity and mass loading. Our approach applies to diverse materials irrespective of their physiochemical properties, including polymers, metals, metal oxides, and others. It can integrate at least four different material types into a single 3D microstructure in a sequential, layer-by-layer manner, opening immense possibilities for tailored functionalities on demand. Furthermore, the 3D microscaffolds are removable, facilitating the creation of pure material-based 3D microstructures. This universal 3D micro-/nanofabrication technique with various nanomaterials enables the creation of advanced miniature devices with potential applications in multifunctional microrobots and smart micromachines.

Diatomite-incorporated hierarchical scaffolds for osteochondral regeneration

Osteochondral regeneration involves the highly challenging and complex reconstruction of cartilage and subchondral bone. Silicon (Si) ions play a crucial role in bone development. Current research on Si ions mainly focuses on bone repair, by using silicate bioceramics with complex ion compositions. However, it is unclear whether the Si ions have important effect on cartilage regeneration. Developing a scaffold that solely releases Si ions to simultaneously promote subchondral bone repair and stimulate cartilage regeneration is critically important. Diatomite (DE) is a natural diatomaceous sediment that can stably release Si ions, known for its abundant availability, low cost, and environmental friendliness. Herein, a hierarchical osteochondral repair scaffold is uniquely designed by incorporating gradient DE into GelMA hydrogel. The adding DE microparticles provides a specific Si source for controlled Si ions release, which not only promotes osteogenic differentiation of rBMSCs (rabbit bone marrow mesenchymal stem cells) but also enhances proliferation and maturation of chondrocytes. Moreover, DE-incorporated hierarchical scaffolds significantly promoted the regeneration of cartilage and subchondral bone. The study suggests the significant role of Si ions in promoting cartilage regeneration and solidifies their foundational role in enhancing bone repair. Furthermore, it offers an economic and eco-friendly strategy for developing high value-added osteochondral regenerative bioscaffolds from low-value ocean natural materials.

Photoreaction Drives Efficient, Precise, and Sustainable Additive Manufacturing

Additive manufacturing, normally referred to as three-dimensional (3D) printing, has been maturing rapidly in recent years and widely utilized in various industrial fields, because it can create predesigned functional products with sophisticated structures that are basically difficult to achieve using traditional methods. Among all 3D printing technologies, vat photopolymerization has attracted much attention because of its outstanding advantages such as fast printing speed, high precision, and ease of formulating. In recent years, many breakthroughs in photopolymerization based 3D printing have been achieved by photoreaction design regarding photopolymerizable monomers, photoinitiating systems, inhibition functions, light sourcs, etc., but challenges remain. This Perspective attempts to highlight these great advances regarding the promotion of printing efficiency, accuracy, and sustainability. At the end, several challenges, such as longer-wavelength printing, printing of functional materials, and multimaterial printing, are discussed, which must be carefully addressed to meet the increasing requirements of future high-performance additive manufacturing.

Nanocrystal Assemblies: Current Advances and Open Problems

We explore the potential of nanocrystals (a term used equivalently to nanoparticles) as building blocks for nanomaterials, and the current advances and open challenges for fundamental science developments and applications. Nanocrystal assemblies are inherently multiscale, and the generation of revolutionary material properties requires a precise understanding of the relationship between structure and function, the former being determined by classical effects and the latter often by quantum effects. With an emphasis on theory and computation, we discuss challenges that hamper current assembly strategies and to what extent nanocrystal assemblies represent thermodynamic equilibrium or kinetically trapped metastable states. We also examine dynamic effects and optimization of assembly protocols. Finally, we discuss promising material functions and examples of their realization with nanocrystal assemblies.

Ligand-Assisted Direct Lithography of Upconverting and Avalanching Nanoparticles for Nonlinear Photonics

Upconverting nanoparticles (UCNPs) exhibit unique nonlinear optical properties that can be harnessed in microscopy, sensing, and photonics. However, forming high-resolution nano- and micropatterns of UCNPs with large packing fractions is still challenging. Additionally, there is limited understanding of how nanoparticle patterning chemistries are affected by the particle size. Here, we explore direct patterning chemistries for 6-18 nm Tm3+-, Yb3+/Tm3+-, and Yb3+/Er3+-based UCNPs using ligands that form either new ionic linkages or covalent bonds between UCNPs under ultraviolet (UV), electron-beam (e-beam), and near-infrared (NIR) exposure. We study the effect of UCNP size on these patterning approaches and find that 6 nm UCNPs can be patterned with compact ionic-based ligands. In contrast, patterning larger UCNPs requires long-chain, cross-linkable ligands that provide sufficient interparticle spacing to prevent irreversible aggregation upon film casting. Compared to approaches that use a cross-linkable liquid monomer, our patterning method limits the cross-linking reaction to the ligands bound on UCNPs deposited as a thin film. This highly localized photo-/electron-initiated chemistry enables the fabrication of densely packed UCNP patterns with high resolutions (∼1 μm with UV and NIR exposure; <100 nm with e-beam). Our upconversion NIR lithography approach demonstrates the potential to use inexpensive continuous-wave lasers for high-resolution 2D and 3D lithography of colloidal materials. The deposited UCNP patterns retain their upconverting, avalanching, and photoswitching behaviors, which can be exploited in patterned optical devices for next-generation UCNP applications.

Widening the use of 3D printing

A light-triggered fabrication method extends the functionality of printable nanomaterials.