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

Multifaceted impacts of nanoparticles on plant nutrient absorption and soil microbial communities

With the growth of the global population and the increasing scarcity of resources, the sustainability and efficiency improvement of agricultural production have become urgent needs. The rapid development of nanotechnology provides new solutions to this challenge, especially the application of nanoparticles in agriculture, which is gradually demonstrating its unique advantages and broad prospects. Nonetheless, various nanoparticles can influence plant growth in diverse manners, often through distinct mechanisms of action. Beyond their direct effects on the plant itself, they frequently alter the physicochemical properties of the soil and modulate the structure of microbial communities in the rhizosphere. This review focuses intently on the diverse methods through which nanoparticles can modulate plant growth, delving deeply into the interactions between nanoparticles and plants, as well as nanoparticles with soil and microbial communities. The aim is to offer a comprehensive reference for the utilization of functionalized nanoparticles in the agricultural sector.

Dispersion strategies of nanomaterials in polymeric inks for efficient 3D printing of soft and smart 3D structures: A systematic review

Nanoscience-often summarized as "the future is tiny"-highlights the work of researchers advancing nanotechnology through incremental innovations. The design and innovation of new nanomaterials are vital for the development of next-generation three-dimensional (3D) printed structures characterized by low cost, high speed, and versatile capabilities, delivering exceptional performance in advanced applications. The integration of nanofillers into polymeric-based inks for 3D printing heralds a new era in additive manufacturing, allowing for the creation of custom-designed 3D objects with enhanced multifunctionality. To optimize the use of nanomaterials in 3D printing, effective disaggregation techniques and strong interfacial adhesion between nanofillers and polymer matrices are essential. This review provides an overview of the application of various types of nanomaterials used in 3D printing, focusing on their functionalization principles, dispersion strategies, and colloidal stability, as well as the methodologies for aligning nanofillers within the 3D printing framework. It discusses dispersive methods, synergistic dispersion, and in-situ growth, which have yielded smart 3D-printed structures with unique functionality for specific applications. This review also focuses on nanomaterial alignment in 3D printing, detailing methods that enhance selective deposition and orientation of nanofillers within established and customized printing techniques. By emphasizing alignment strategies, we explore their impact on the performance of 3D-printed composites and highlight potential applications that benefit from ordered nanoparticles. Through these continuing efforts, this review shows that the design and development of the new class of nanomaterials are crucial to developing the next generation of smart 3D printed architectures with versatile abilities for advanced structures with exceptional performance.

Optical properties of monolithic zirconia fabricated with nanoparticle jetting

STATEMENT OF PROBLEM

Excellent optical properties are essential for esthetic dental materials. However, the translucency and color masking ability of zirconia fabricated with nanoparticle jetting (NPJ), a type of printed zirconia, are unknown.

PURPOSE

The purpose of this in vitro study was to evaluate the translucency and color masking ability of zirconia fabricated using NPJ.

MATERIAL AND METHODS

A total of 90 specimens with thicknesses of 1.5, 1.0, and 0.5 mm were fabricated using high translucent milled zirconia (HT), low translucent milled zirconia (LT), and NPJ. CIELab values (L*, a*, and b*) of the specimens over 7 backgrounds, black, white, VitaB1, VitaA2, VitaA4, gold alloy (Au), and titanium (Ti), were obtained using a spectral radiometer. The relative translucency parameter (RTP) and color difference (∆E) of specimens over VitaB1, VitaA4, Au, and Ti were determined using VitaA2 as the control with the CIEDE2000 color difference equation. The normality of the data distribution was determined using the Shapiro-Wilk test. Differences among groups were analyzed using 2-way analysis of variance and the Student-Newman-Keuls (SNK) post hoc test (α=.05). The ∆E of specimens was analyzed according to perceptibility (∆E=0.8) and acceptability (∆E=1.8) thresholds using the 1 sample t test. The correlation between RTP and ∆E and RTP/∆E and thickness was examined using the Pearson correlation analysis.

RESULTS

Statistically significant differences were observed in translucency and color masking ability among HT, LT, and NPJ (P<.05). The RTP value was the lowest for zirconia fabricated with NPJ (P<.001) and highest for HT (P<.001). Monolithic zirconia fabricated with NPJ had lower ∆E values than those of HT and LT for the same thickness and background (P<.05). A positive correlation was found in RTP and ∆E (P<.001). A negative correlation was observed in RTP and thickness (P<.001) and ∆E and thickness across a constant background (P<.001).

CONCLUSIONS

Zirconia fabricated with NPJ was less translucent and had a greater color masking ability for discolored backgrounds than HT and LT.

Ink-Based Additive Manufacturing of a Polymer/Coal Composite: A Non-Traditional Reinforcement

Coal, a crucial natural resource traditionally employed for generating carbon-rich materials and powering global industries, has faced escalating scrutiny due to its adverse environmental impacts outweighing its utility in the contemporary world. In response to the worldwide shift toward sustainability, the United States alone has witnessed an approximate 50% reduction in coal consumption. Nevertheless, the ample availability of coal has spurred interest in identifying alternative sustainable applications. This research delves into the feasibility of utilizing coal as a nonconventional carbon-rich reinforcement in direct ink writing (DIW)-based 3D printing techniques. Our investigation here involves a thermosetting resin serving as a matrix, incorporating pulverized coal (250 μm in size) and carbon black as the reinforcement and a viscosity modifier, respectively. The ink formulation is meticulously designed to exhibit shear-thinning behavior essential for DIW 3D printing, ensuring uniform and continuous printing. Mechanical properties are assessed through the 3D printing of ASTM standard specimens to validate the reinforcing impact. Remarkably, the study reveals that a 2 wt % coal concentration in the ink leads to a substantial improvement in both tensile and flexural properties, resulting in enhancements of 35 and 12.5%, respectively. Additionally, the research demonstrates the printability of various geometries with coal as reinforcement, opening up new possibilities for coal utilization while pursuing more sustainable manufacturing and applications.

Biomimetic Mineralized 3D-Printed Polycaprolactone Scaffold Induced by Self-Adaptive Nanotopology to Accelerate Bone Regeneration

Three-dimensional (3D)-printed biodegradable polymer scaffolds are at the forefront of personalized constructs for bone tissue engineering. However, it remains challenging to create a biological microenvironment for bone growth. Herein, we developed a novel yet feasible approach to facilitate biomimetic mineralization via self-adaptive nanotopography, which overcomes difficulties in the surface biofunctionalization of 3D-printed polycaprolactone (PCL) scaffolds. The building blocks of self-adaptive nanotopography were PCL lamellae that formed on the 3D-printed PCL scaffold via surface-directed epitaxial crystallization and acted as a linker to nucleate and generate hydroxyapatite crystals. Accordingly, a uniform and robust mineralized layer was immobilized throughout the scaffolds, which strongly bound to the strands and had no effect on the mechanical properties of the scaffolds. In vitro cell culture experiments revealed that the resulting scaffold was biocompatible and enhanced the proliferation and osteogenic differentiation of mouse embryolous osteoblast cells. Furthermore, we demonstrated that the resulting scaffold showed a strong capability to accelerate in vivo bone regeneration using a rabbit bone defect model. This study provides valuable opportunities to enhance the application of 3D-printed scaffolds in bone repair, paving the way for translation to other orthopedic implants.

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.

Innovations in hydrogel-based manufacturing: A comprehensive review of direct ink writing technique for biomedical applications

Direct ink writing (DIW) stands as a pioneering additive manufacturing technique that holds transformative potential in the field of hydrogel fabrication. This innovative approach allows for the precise deposition of hydrogel inks layer by layer, creating complex three-dimensional structures with tailored shapes, sizes, and functionalities. By harnessing the versatility of hydrogels, DIW opens up possibilities for applications spanning from tissue engineering to soft robotics and wearable devices. This comprehensive review investigates DIW as applied to hydrogels and its multifaceted applications. The paper introduces a diverse range of printing techniques while providing a thorough exploration of DIW for hydrogel-based printing. The investigation aims to explain the progress made, challenges faced, and potential trajectories that lie ahead for DIW in hydrogel-based manufacturing. The fundamental principles underlying DIW are carefully examined, specifically focusing on rheological attributes and printing parameters, prompting a comprehensive survey of the wide variety of hydrogel materials. These encompass both natural and synthetic variations, all of which can be effectively harnessed for this purpose. Furthermore, the review explores the latest applications of DIW for hydrogels in biomedical areas, with a primary focus on tissue engineering, wound dressing, and drug delivery systems. The document not only consolidates the existing state of DIW within the context of hydrogel-based manufacturing but also charts potential avenues for further research and innovative breakthroughs.

Assembled one-dimensional nanowires for flexible electronic devices via printing and coating: Techniques, applications, and perspectives

The rapid progress in flexible electronic devices has necessitated continual research into nanomaterials, structural design, and fabrication processes. One-dimensional nanowires, characterized by their distinct structures and exceptional properties, are considered essential components for various flexible electronic devices. Considerable attention has been directed toward the assembly of nanowires, which presents significant advantages. Printing and coating techniques can be used to assemble nanowires in a relatively simple, efficient, and cost-competitive manner and exhibit potential for scale-up production in the foreseeable future. This review aims to provide an overview of nanowire assembly using printing and coating techniques, such as bar coating, spray coating, dip coating, blade coating, 3D printing, and so forth. The application of assembled nanowires in flexible electronic devices is subsequently discussed. Finally, further discussion is presented on the potential and challenges of flexible electronic devices based on assembled nanowires via printing and coating.

A systematic review of the role of 4D printing in sustainable civil engineering solutions

This systematic review, not financially supported by any funding body, aims to synthesize the current knowledge on the applications, potential benefits, and challenges of 4D printing in civil engineering, with a focus on its role in sustainable solutions. Comprehensive searches were conducted in Scopus, Web of Science, and Google Scholar using related keywords. Articles that discussed 4D printing within civil engineering and construction contexts, encompassing both conceptual and empirical studies, were included. The findings suggest that 4D printing, with its time-responsive transformation feature, can enhance design freedom, improve structural performance, and increase environmental efficiency in construction. However, challenges persist in material performance, scalability, and cost. Despite these, ongoing advancements signal potential future developments that could widen the opportunities for large-scale applications of 4D printing in civil engineering. The potential use of renewable, bio-based materials could also lead to more sustainable construction practices. This review highlights the transformative potential of 4D printing, underlining the need for further research to fully leverage its capabilities and address current limitations. 4D printing emerges as a promising avenue for sustainable civil engineering solutions, offering a transformative approach that calls for continued exploration and development.

Additive Manufacturing in Atomic Layer Processing Mode

Additive manufacturing (3D printing) has not been applicable to micro- and nanoscale engineering due to the limited resolution. Atomic layer deposition (ALD) is a technique for coating large areas with atomic thickness resolution based on tailored surface chemical reactions. Thus, combining the principles of additive manufacturing with ALD could open up a completely new field of manufacturing. Indeed, it is shown that a spatially localized delivery of ALD precursors can generate materials patterns. In this "atomic-layer additive manufacturing" (ALAM), the vertical resolution of the solid structure deposited is about 0.1 nm, whereas the lateral resolution is defined by the microfluidic gas delivery. The ALAM principle is demonstrated by generating lines and patterns of pure, crystalline TiO₂ and Pt on planar substrates and conformal coatings of 3D nanostructures. The functional quality of ALAM patterns is exemplified with temperature sensors, which achieve a performance similar to the industry standard. This general method of multimaterial direct patterning is much simpler than standard multistep lithographic microfabrication. It offers process flexibility, saves processing time, investment, materials, waste, and energy. It is envisioned that together with etching, doping, and cleaning performed in a similar local manner, ALAM will create the "atomic-layer advanced manufacturing" family of techniques.