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Nanomaterials have gained enormous interest in improving the performance of energy harvest systems, biomedical devices, and high-strength composites. Many studies were performed fabricating more elaborate and heterogeneous nanostructures then the structures were characterized using TEM tomographic images, upgrading the fabrication technique. Despite the effort, intricate fabrication process, agglomeration characteristic, and non-uniform output were still limited to presenting the 3D panoramic views straightforwardly. Here we suggested in situ synthesis method to prepare complex and hierarchically-assembled nanostructures that consisted of ZnS nanowire core and nanoparticles under Ag2S catalyst. We demonstrated that the vaporized Zn and S were solidified in different shapes of nanostructures with the temperatures solely. To our knowledge, this is the first demonstration of synthesizing heterogeneous nanostructures, consisting of a nanowire from the vapor–liquid–solid and then nanoparticles from the vapor–solid grown mechanism by in situ temperature control. The obtained hierarchically-assembled ZnS nanostructures were characterized by various TEM technologies, verifying the crystal growth mechanism. Lastly, electron tomography and 3D printing enabled the nanoscale structures to visualize with centimeter scales. The 3D printing from randomly fabricated nanomaterials is rarely performed to date. The collaborating work could offer a better opportunity to fabricate advanced and sophisticated nanostructures. [ABSTRACT FROM AUTHOR]

Abstract: Colloidal PVP (poly(vinyl pyrrolidone))–stabilized gold nanoparticles (PVP–AuNPs) are synthesized in aqueous solution with PVP as a reducing and stabilizing agent using a short microwave (MW) heating duration of 1 min. The size and uniformity of the synthesized PVP–AuNPs can be varied by modifying the concentration of sodium citrate (Na3Ct), which acts predominantly as mediator of the stability of PVP–AuNP formation during the rapid synthesis. Due to the increase in the Na3Ct concentration, the number of citrate ions adsorbed on the growing surface of AuNPs increase, and less reactive gold solute complexes are formed, leading to slow stable reactions that produce small, uniform colloidal PVP–AuNPs. We therefore demonstrate that by adjusting the Na3Ct concentration used in the PVP reduction, the diameter of PVP–AuNPs was varied from 19.47 ± 3.97 nm to 7.94 ± 0.14 nm when using constant concentrations of chloroauric acid (HAuCl4) and PVP. [Copyright &y& Elsevier]

Abstract: We describe formation kinetics of gold nanoparticles (AuNPs) in microwave synthesis. Using high microwave power to increase the temperature ramping rate (R r) homogeneous nucleation is facilitated and the size of the resultant nanoparticles is reduced while the uniformity is much improved. Adjusting solution pH to higher than 6.2 could also have a positive effect on the quality of the nanosol. We therefore demonstrate that by adjusting these reaction parameters in microwave synthesis, we successfully produced uniform colloidal AuNPs with diameter of 12.04±1.35nm in a few minutes. [Copyright &y& Elsevier]

Abstract: Experiments performed using the novel technique of real-time microradiography with coherent X-rays provided clear experimental evidence of the “fibrilization” phenomenon of electrical conductive microspheres between a copper microelectrode (anode) and platinum plate (cathode) in electrorheological fluids under an applied voltage (about 2kV/mm). The surface-conductive polymeric microspheres were prepared by the adsorption of multi-walled carbon nanotubes (MWCNTs) on the surface of poly(methylmethacrylate) microspheres (6.5μm). We also observed the process of MWCNT adsorption on the polymeric microspheres in the MWCNT dispersion containing surfactants and the assembly of MWCNTs-coated microspheres during their sedimentation in real-time by microradiography. [Copyright &y& Elsevier]

A 3D integrated neuromorphic system with an embedded structure is fabricated by in-situ 3D printing with multiple materials. The 3D integrated electrochemical neuromorphic system is demonstrated for mimicking biological functions such as chemical sensing, self-activation, and signal transmission using 3D printed electronic components. The achieved memory and learning capability are demonstrated by the detection of low concentrations of soil nutrients for smart agricultural applications. • A 3D integrated neuromorphic system with high selectivity were fabricated by 3D printing. • 3D integrated neuromorphic system for the chemical sensing is reported here by mimicking biological functions. • The neuromorphic system demonstrates memory effect for the detection of solution with low concentration by training. Neuromorphic systems are essential for next-generation neuro-robotics and neuro-prosthetics with biological signal processing and memory functions. In this work, we propose a 3D integrated neuromorphic system for chemical sensing with 3D printed components, including a sensor, an electrical oscillator, and a synaptic transistor, which mimic sensory receptors, neurons, and synapses in biological systems, respectively. The 3D neuromorphic system was fabricated by 3D printing of multiple materials, resulting in significant improvements in the volumetric efficiency of the system. Through this system, different ion concentrations are detected, self-activated, and transmitted. Finally, the electrochemical neuromorphic sensing function is demonstrated by the integrated 3D neuromorphic system with artificial sensory receptors, artificial neurons, and artificial synapses for application in the detection of low concentrations of soil nutrients in smart farms. [ABSTRACT FROM AUTHOR]

Electrochemiluminescence (ECL) has attracted significant attention as a promising light‐emitting technology owing to its simple configuration and solution processability. ECL has wide applications in biological and chemical sensors, lighting, and displays. ECL lighting devices are fabricated as sandwiched structures with a transparent electrode on top, which limits their widespread adoption. Intricate structures with high precision and customizable designs can be directly fabricated using 3D printing. However, 3D printing of ECL devices is challenging because of poor printability and structural integrity of ECL luminophore inks. Here, all‐printed electrically driven lighting is demonstrated using the direct ink writing method. The ECL reactive layer and electrodes are directly printed using a side‐by‐side electrode configuration. A 3D printable ECL ink is developed by incorporating silica nanoparticles as rheological modifiers to realize well‐defined patterns with high structural integrity. Graphene is introduced on Ag multilayer electrodes to embrace both the electrical conductivity and electrochemical stability for efficient ECL operation. This all‐printing approach allows the fabrication of ECL devices with complex designs, such as combs and spirals. Moreover, it facilitates seamless printing on various substrate materials, making this technology an asset in the fields of biology, chemistry, and electronics. [ABSTRACT FROM AUTHOR]

Organic–inorganic perovskite quantum dot (PQD)–polymer composites are emerging optoelectronic materials with exceptional properties that are promising widespread application in next‐generation electronics. Advances in the utilization of these materials depend on the development of suitable fabrication techniques to create 3D architectures composed of PQD–polymer for sophisticated optoelectronics. This study introduces a straightforward and effective method for producing 3D architectures of PQD‐encapsulated high‐performance composites (PQD‐HPCs) through direct‐ink writing (DIW). This method employs an ink composed of prefabricated PQDs and hydroxypropyl cellulose (HPC) in dichloromethane (DCM). HPC, an appropriate organic‐soluble polymer, exhibits optical transparency in the highly volatile DCM and enables the formulation of a stable, room‐temperature extrudable ink. The architectures, which are printed by adjusting the halide ratios (Cl, Br, and I) for the compositions of CH3NH3PbBr1.5I1.5, CH3NH3PbBr3, and CH3NH3PbBr1.5Cl1.5, exhibit single peak photoluminescence emissions of red (639 nm), green (515 nm), and blue (467 nm). Optimizing the printing parameters of DIW enables the precise fabrication of programmed and complex PQD‐HPC 3D architectures for advanced anti‐counterfeiting and information encryption. This method has the potential to enhance the functionality of modern printed electronic devices significantly. [ABSTRACT FROM AUTHOR]

Using energy‐saving electrochromic (EC) displays in smart devices for augmented reality makes cost‐effective, easily producible, and efficiently operable devices for specific applications possible. Prussian blue (PB) is a metal‐organic coordinated compound with unique EC properties that limit EC display applications due to the difficulty in PB micro‐patterning. This work presents a novel micro‐printing strategy for PB patterns using localized crystallization of FeFe(CN)6 on a substrate confined by the acidic‐ferric‐ferricyanide ink meniscus, followed by thermal reduction at 120 °C, thereby forming PB. Uniform PB patterns can be obtained by manipulating printing parameters, such as the concentration of FeCl3·K3Fe(CN)6, printing speed, and pipette inner diameter. Using a 0.1 M KCl (pH 4) electrolyte, the printed PB pattern is consistently and reversibly converted to Prussian white (CV potential range: −0.2–0.5 V) with 200 CV cycles. The PB‐based EC display with a navigation function integrated into a smart contact lens is able to display directions to a destination to a user by receiving GPS coordinates in real time. This facile method for forming PB micro‐patterns could be used for advanced EC displays and various functional devices. [ABSTRACT FROM AUTHOR]

3D printed electronics employing direct‐ink‐writing methods are promising alternative manufacturing technologies for realizing structural electronics. The emerging demand for accessible, cost‐effective, and rapid writing calls for novel approaches to print functional components onto nonflat and 3D architectures. This study presents a novel air‐pressure‐assisted pen‐nib printing approach producing electrical and functional components with various material inks on flat and 3D surfaces. Based on the inks' rheological properties, the ejected ink's quantity through the nib is manipulated via air pressure; thus, the printed line width is controlled. This strategy also achieves the viscosity range extension of printable inks by enabling printing inks that cannot be used in general pen‐based printing. Three functional inks with different rheological properties—Ag catalyst ink for Cu electroless deposition, Ag‐PEDOT:PSS ink, and thermochromic pigment inks are designed. Several electrical and functional components, such as highly conductive Cu interconnects, Cu spiral coils for wireless power transfer receivers, flexible heaters, and matrix data codes based on temperature‐responsive color transitions are demonstrated. Furthermore, parallel printing with a multi‐nib print‐head is demonstrated for improving the printing speed and manufacturing scalability. The authors believe that this novel approach is promising as a manufacturing technique for realizing 3D printed electronics. [ABSTRACT FROM AUTHOR]

Electrochemical water splitting has been considered one of the most promising methods of hydrogen production, which does not cause environmental pollution or greenhouse gas emissions. Oxygen evolution reaction (OER) is a significant step for highly efficient water splitting because OER involves the four electron transfer, overcoming the associated energy barrier that demands a potential greater than that required by hydrogen evolution reaction. Therefore, an OER electrocatalyst with large surface area and high conductivity is needed to increase the OER activity. In this work, we demonstrated an effective strategy to produce a highly active three-dimensional (3D)-printed NiFe-layered double hydroxide (LDH) pyramid electrode for OER using a three-step method, which involves direct-ink-writing of a graphene pyramid array and electrodeposition of a copper conducive layer and NiFe-LDH electrocatalyst layer on printed pyramids. The 3D pyramid structures with NiFe-LDH electrocatalyst layers increased the surface area and the active sites of the electrode and improved the OER activity. The overpotential (η) and exchange current density (i0) of the NiFe-LDH pyramid electrode were further improved compared to that of the NiFe-LDH deposited Cu (NiFe-LDH/Cu) foil electrode with the same base area. The 3D-printed NiFe-LDH electrode also exhibited excellent durability without potential decay for 60 h. Our 3D printing strategy provides an effective approach for the fabrication of highly active, stable, and low-cost OER electrocatalyst electrodes. [ABSTRACT FROM AUTHOR]

Magnetic graphene composite comprising graphene sheets decorated with magnetite nanoparticles (NPs) is an important material with numerous successful and potential applications in electronics, chemistry, physics, and bio-medicine. The further use of this material relies on the development of an appropriate patterning method for the production of two-dimensional (2D) and three-dimensional (3D) magnetic graphene composite objects. This study presents a simple and effective strategy to fabricate 2D and 3D micropatterns of Fe 3 O 4 functionalized graphene-polymer (FGP) nanocomposite using extrusion-based 3D printing with a highly loaded FGP nanocomposite ink. The ink consisted of Fe 3 O 4 nanoparticles (NPs), graphene microflakes (GMFs), and hydroxypropyl cellulose (HPC), and was stable and suitable for 3D printing of FGP objects. Various FGP 3D microarchitectures, including a grid, honeycomb, pyramid, and square, were successfully printed using the layer-by-layer (LbL) printing approach. The printed objects exhibited a conductivity of ∼580 S m−1 and magnetic property of 15.8 emu g−1. Successful demonstrations of electronic devices such as a magnet-guided car, a magnetic switch, and a 3D grid for electromagnetic interference (EMI) shielding are also described herein. This 3D printing approach was effective for the 2D and 3D patterning of functional nanocomposites and shows promise for advanced printed electronic applications. Image 1 [ABSTRACT FROM AUTHOR]

Many emerging applications in microscale engineering rely on the fabrication of 3D architectures in inorganic materials. Small‐scale additive manufacturing (AM) aspires to provide flexible and facile access to these geometries. Yet, the synthesis of device‐grade inorganic materials is still a key challenge toward the implementation of AM in microfabrication. Here, a comprehensive overview of the microstructural and mechanical properties of metals fabricated by most state‐of‐the‐art AM methods that offer a spatial resolution ≤10 μm is presented. Standardized sets of samples are studied by cross‐sectional electron microscopy, nanoindentation, and microcompression. It is shown that current microscale AM techniques synthesize metals with a wide range of microstructures and elastic and plastic properties, including materials of dense and crystalline microstructure with excellent mechanical properties that compare well to those of thin‐film nanocrystalline materials. The large variation in materials' performance can be related to the individual microstructure, which in turn is coupled to the various physico‐chemical principles exploited by the different printing methods. The study provides practical guidelines for users of small‐scale additive methods and establishes a baseline for the future optimization of the properties of printed metallic objects—a significant step toward the potential establishment of AM techniques in microfabrication. [ABSTRACT FROM AUTHOR]

An effective approach is required to improve the spatial resolution and electrical conductivity of printed graphene patterns for advanced graphene-based printed electronics. Here, we describe a simple and effective strategy to fabricate few-micrometer-wide graphene patterns by meniscus-guided printing, using a highly concentrated graphene oxide (GO, 2 wt%) ink. Our approach exploits the rapid solidification of an ink meniscus formed by horizontal pulling of a micronozzle. To achieve uniform printing with continuous flow of the highly concentrated GO ink through the nozzle, polyvinylpyrrolidone (PVP), which acts as a gelation inhibitor and rheology modifier, was added to the aqueous GO solution. GO reduction and PVP removal from the printed patterns was achieved simultaneously, by thermal treatment. Electrical conductivities and widths of the reduced GO (rGO) patterns could be easily modulated by adjusting the nozzle-pulling rate and changing the nozzle-opening size, respectively. Toward applications in electronics, successful fabrication of a field-effect transistor based on a printed rGO channel is also described. This approach can be effective for high-resolution printing of graphene patterns for electronic applications. [ABSTRACT FROM AUTHOR]

B Meniscus-Guided Printing b Meniscus-guided micro-printing of Prussian Blue is realized by the localized crystallization of FeFe(CN) SB 6 sb on the substrate confined by the ink meniscus and thermal reduction of the crystallized FeFe(CN) SB 6 sb . This strategy is capable of being used as an electrochromic display to give real-time directions on an augmented reality (AR) smart contact lens device. Meniscus-Guided Micro-Printing of Prussian Blue for Smart Electrochromic Display (Adv. Sci. 3/2023). [Extracted from the article]

Abstract: We developed a novel approach to prepare Ni–Au composite nanoparticles using synchrotron radiation X-rays. Ni–Au particles dispersed in aqueous solutions were synthesized with two different irradiation strategies. The first is by exposing to X-rays a mixed electroless solution of Ni and Au at two different temperatures, trying to nucleate Ni nanoparticles homogeneously at room temperature and to deposit Au subsequently on them at the high temperature of 70°C. The second strategy is to change the pH value of the mixed solution, directly leading to the formation of Ni–Au nanoparticles. In both cases, the Ni–Au composite nanoparticles were successfully formed, as confirmed by the observed ferromagnetic behavior and by the evolution of the Au surface plasmon resonance band. [Copyright &y& Elsevier]

Abstract: It was demonstrated that pulsed microwave irradiation is a more effective method to accelerate the esterification of free fatty acid with a heterogeneous catalyst than continuous microwave irradiation. A square-pulsed microwave with a 400Hz repetition rate and a 10–20% duty cycle with the same energy as the continuous microwave were used in this study. The pulsed microwaves improved the esterification conversion from 39.9% to 66.1% after 15min in comparison with the continuous microwave under the same reaction conditions. These results indicated that pulsed microwaves with repetitive strong power could enhance the efficiency of biodiesel production relative to the use of continuous microwave with mild power. [Copyright &y& Elsevier]

Abstract: This paper shows energy-efficiency of microwave-accelerated esterification of free fatty acid with a heterogeneous catalyst by net microwave power measurement. In the reaction condition of 5wt% sulfated zirconia and 1:20M ratio of oil to methanol at 60°C and atmospheric pressure, more than 90% conversion of the esterification was achieved in 20min by microwave heating, while it took about 130min by conventional heating. Electric energy consumption for the microwave heating in this accelerated esterification was only 67% of estimated minimum heat energy demand because of significantly reduced reaction time. [ABSTRACT FROM AUTHOR]

Nanocarbon-based conducting fibres have been produced using solution- or dry-spinning techniques. Highly conductive polymer-composite fibres containing large amounts of conducting nanomaterials have not been produced without dispersants, however, because of the severe aggregation of conducting materials in high-concentration colloidal solutions. Here we show that highly conductive (electrical conductivity ~1.5 × 105 S m−1) polymer-composite fibres containing carbon nanotubes and silver nanowires can be fabricated via a conventional solution-spinning process without any other treatment. Spinning dopes were fabricated by a simple mixing of a polyvinyl alcohol solution in dimethylsulfoxide with a paste of long multi-walled carbon nanotubes dispersed in organic solvents, assisted by quadruple hydrogen-bonding networks and an aqueous silver nanowire dispersion. The high electrical conductivity of the fibre was achieved by rearrangement of silver nanowires towards the fibre skin during coagulation because of the selective favourable interaction between the silver nanowires and coagulation solvents. The prepared conducting fibres provide applications in electronic textiles such as a textile interconnector of light emitting diodes, flexible textile heaters, and touch gloves for capacitive touch sensors. [ABSTRACT FROM AUTHOR]