Nanoparticle Assembly: From Self-Organization to Controlled Micropatterning for Enhanced Functionalities.

Nanoparticles form long-range micropatterns via self-assembly or directed self-assembly with superior mechanical, electrical, optical, magnetic, chemical, and other functional properties for broad applications, such as structural supports, thermal exchangers, optoelectronics, microelectronics, and robotics. The precisely defined particle assembly at the nanoscale with simultaneously scalable patterning at the microscale is indispensable for enabling functionality and improving the performance of devices. This article provides a comprehensive review of nanoparticle assembly formed primarily via the balance of forces at the nanoscale (e.g., van der Waals, colloidal, capillary, convection, and chemical forces) and nanoparticle-template interactions (e.g., physical confinement, chemical functionalization, additive layer-upon-layer). The review commences with a general overview of nanoparticle self-assembly, with the state-of-the-art literature review and motivation. It subsequently reviews the recent progress in nanoparticle assembly without the presence of surface templates. Manufacturing techniques for surface template fabrication and their influence on nanoparticle assembly efficiency and effectiveness are then explored. The primary focus is the spatial organization and orientational preference of nanoparticles on non-templated and pre-templated surfaces in a controlled manner. Moreover, the article discusses broad applications of micropatterned surfaces, encompassing various fields. Finally, the review concludes with a summary of manufacturing methods, their limitations, and future trends in nanoparticle assembly.

3D Printing-Enabled Design and Manufacturing Strategies for Batteries: A Review.

Lithium-ion batteries (LIBs) have significantly impacted the daily lives, finding broad applications in various industries such as consumer electronics, electric vehicles, medical devices, aerospace, and power tools. However, they still face issues (i.e., safety due to dendrite propagation, manufacturing cost, random porosities, and basic & planar geometries) that hinder their widespread applications as the demand for LIBs rapidly increases in all sectors due to their high energy and power density values compared to other batteries. Additive manufacturing (AM) is a promising technique for creating precise and programmable structures in energy storage devices. This review first summarizes light, filament, powder, and jetting-based 3D printing methods with the status on current trends and limitations for each AM technology. The paper also delves into 3D printing-enabled electrodes (both anodes and cathodes) and solid-state electrolytes for LIBs, emphasizing the current state-of-the-art materials, manufacturing methods, and properties/performance. Additionally, the current challenges in the AM for electrochemical energy storage (EES) applications, including limited materials, low processing precision, codesign/comanufacturing concepts for complete battery printing, machine learning (ML)/artificial intelligence (AI) for processing optimization and data analysis, environmental risks, and the potential of 4D printing in advanced battery applications, are also presented.

Crosslinked Polyethylene (XLPE) Recycling via Foams.

Efficient recycling of crosslinked polyethylene has been challenging due to manufacturing difficulties caused by chemical crosslinking. This study focuses on simple processing via solid waste powder generation and particle fining for the subsequent crosslinked polyethylene inclusion and dispersion in rigid polyurethane foam. In addition, the concentration effects of crosslinked polyethylene in polyurethane were studied, showing a well-controlled foam microstructure with uniform pores, retained strength, better thermal degradation resistance, and, more importantly, increased thermal capabilities. Thus, the simple mechanical processing of crosslinked polyethylene and chemical urethane foaming showed the massive potential of recycling large amounts of crosslinked polyethylene in foams for broad applications in food packaging, house insulation, and sound reduction.

Intrinsic Field-Induced Nanoparticle Assembly in Three-Dimensional (3D) Printing Polymeric Composites.

Nanoparticles (NPs) are materials considered to be 1-100 nm in size and are available in different dimensional shapes, geometrical sizes, physical morphologies, mechanical robustness, and chemical compositions. Irrespective of the dimensions (i.e., zero-dimensional (0D), one-dimensional (1D), and two-dimensional (2D)), NPs have a tendency to become entangled together, forming aggregations due to high attraction, making it hard to realize their full potential from their ordered counterparts. Many challenges exist to attain high-quality stabilized dispersion and long-range ordered assembly of NPs. Three-dimensional printing (3DP), also known as additive manufacturing (AM), is a technique dependent on layer-by-layer material addition for building 3D structures and encompasses a few categories based on the feedstock material types and printing mechanisms. One benefit from the 3DP procedures is their capability to produce anisotropic microstructural/nanostructural characteristics for desired mechanical reinforcement, transport phenomena, energy management, and biomedical implants. This paper briefly overviews relevant 3DP methods with an embedded nature to assemble nanoparticles without interference with external fields (e.g., magnetic or electrical). Our focus is the shear-field-induced nanoparticle alignment, covering material jetting-, electrohydrodynamic-, filament melting-, and ink writing-based 3DP. A concise summary of photopolymerization and its "optical tweezer" effects on nanoparticle confinement also inspires creative approaches in generating ordered nanostructures. The nanoparticles and polymers involved in this review are diverse, consisting of metallic, ceramic, and carbon nanoparticles in matrices or on surfaces of varying macromolecules. A short statement of challenges (e.g., low resolution, slow printing speed, limited material options) for 3DP-enabled nanoparticle orders provides some perspectives toward the enormous potential of 3DP in directing NPs assembly and fabricating high-performance polymer/nanoparticle composites.

3D Printing-Enabled Nanoparticle Alignment: A Review of Mechanisms and Applications.

3D printing (additive manufacturing (AM)) has enormous potential for rapid tooling and mass production due to its design flexibility and significant reduction of the timeline from design to manufacturing. The current state-of-the-art in 3D printing focuses on material manufacturability and engineering applications. However, there still exists the bottleneck of low printing resolution and processing rates, especially when nanomaterials need tailorable orders at different scales. An interesting phenomenon is the preferential alignment of nanoparticles that enhance material properties. Therefore, this review emphasizes the landscape of nanoparticle alignment in the context of 3D printing. Herein, a brief overview of 3D printing is provided, followed by a comprehensive summary of the 3D printing-enabled nanoparticle alignment in well-established and in-house customized 3D printing mechanisms that can lead to selective deposition and preferential orientation of nanoparticles. Subsequently, it is listed that typical applications that utilized the properties of ordered nanoparticles (e.g., structural composites, heat conductors, chemo-resistive sensors, engineered surfaces, tissue scaffolds, and actuators based on structural and functional property improvement). This review's emphasis is on the particle alignment methodology and the performance of composites incorporating aligned nanoparticles. In the end, significant limitations of current 3D printing techniques are identified together with future perspectives.

Aligned Ti3C2Tx MXene for 3D Micropatterning via Additive Manufacturing.

Selective deposition and preferential alignment of two-dimensional (2D) nanoparticles on complex and flexible three-dimensional (3D) substrates can tune material properties and enrich structural versatility for broad applications in wearable health monitoring, soft robotics, and human-machine interfaces. However, achieving precise and scalable control of the morphology of layer-structured nanomaterials is challenging, especially constructing hierarchical architectures consistent from nanoscale alignment to microscale patterning to complex macroscale landscapes. This work demonstrated a scalable and straightforward hybrid 3D printing method for orientational alignment and positional patterning of 2D MXene nanoparticles. This process involved (i) surface topology design via microcontinuous liquid interface production (µCLIP) and (ii) directed assembly of MXene flakes via capillarity-driven direct ink writing (DIW). With well-managed surface patterning geometry and printing ink quality control, the surface microchannels constrained MXene suspensions and leveraged microforces to facilitate preferential alignment of MXene sheets via layer-by-layer additive depositions. The printed devices displayed multifunctional properties, i.e., anisotropic conductivity and piezoresistive sensing with a wide sensing range, high sensitivity, fast response time, and mechanical durability. Our fabrication technique shows enormous potential for rapid, digital, scalable, and low-cost manufacturing of hierarchical structures, especially for micropatterning and aligning 2D nanoparticles not easily accessible through conventional processing methods.

Scalable Alignment and Selective Deposition of Nanoparticles for Multifunctional Sensor Applications.

Here reported is the layer-by-layer-based advanced manufacturing that yields a simple, novel, and cost-effective technique for generating selective nanoparticle deposition and orientation in the form of well-controlled patterns. The surface roughness of the three-dimensionally printed patterns and the solid-liquid-air contact line, as well as the nanoparticle interactions in dipped suspensions, determine the carbon nanofiber (CNF) alignment, while the presence of triangular grooves supports the pinning of the meniscus, resulting in a configuration consisting of alternating CNF and polymer channels. The polymer/nanoparticle composites show 10 times lower resistance along with the particle alignment direction than the randomly distributed CNF networks and 6 orders of magnitude lower than that along the transverse direction. The unidirectional alignment of the CNF also demonstrates linear piezoresistivity behavior under small strain deformation along with high sensitivity and selectivity toward volatile organic compounds. The reported advanced manufacturing shows broad applications in microelectronics, energy transport, light composites, and multifunctional sensors.

Fabricating Fibers of a Porous-Polystyrene Shell and Particle-Loaded Core.

Polystyrene (PS) polymers have broad applications in protective packaging for food shipping, containers, lids, bottles, trays, tumblers, disposable cutlery and the making of models. Currently, most PS products, such as foams, are not accepted for recycling due to a low density in the porous structure. This poses a challenge for logistics as well as creating a lack of incentive to invest in high-value products. This study, however, demonstrated the use of a dry-jet wet-spinning technique to manufacture continuous PS fibers enabled by an in-house designed and developed spinning apparatus. The manufactured fibers showed porosity in the shell and the capability to load particles in their core, a structure with high potential use in environmentally relevant applications such as water treatment or CO2 collections. A two-phase liquid-state microstructure was first achieved via a co-axial spinneret. Following coagulation procedures and heat treatment, phase-separation-based selective dissolution successfully generated the porous-shell/particle-core fibers. The pore size and density were controlled by the porogen (i.e., PEG) concentrations and examined using scanning electron microscopy (SEM). Fiber formation dynamics were studied via rheology tests and gelation measurements. The shell components were characterized by tensile tests, thermogravimetric analysis, and differential scanning calorimetry for mechanical durability and thermal stability analyses.

In situ alignment of graphene nanoplatelets in poly(vinyl alcohol) nanocomposite fibers with controlled stepwise interfacial exfoliation.

Hierarchically microstructured tri-axial poly(vinyl alcohol)/graphene nanoplatelet (PVA/GNP) composite fibers were fabricated using a dry-jet wet spinning technique. The composites with distinct PVA/GNPs/PVA phases led to highly oriented and evenly distributed graphene nanoplatelets (GNPs) as a result of molecular chain-assisted interfacial exfoliation. With a concentration of 3.3 wt% continuously aligned GNPs, the composite achieved a ∼73.5% increase in Young's modulus (∼38 GPa), as compared to the pure PVA fiber, and an electrical conductivity of ∼0.38 S m-1, one of the best mechanical/electrical properties reported for polymer/GNP nanocomposite fibers. This study has broader impacts on textile engineering, wearable robotics, smart sensors, and optoelectronic devices.