Far-field spectral imaging, coupled with computer vision methods, is demonstrated as an effective inspection method for detection, classification, and root-cause analysis of manufacturing defects in large area Si nanopillar arrays. Si nanopillar arrays exhibit a variety of nanophotonic effects, causing them to produce colors and spectral signatures which are highly sensitive to defects, on both the macro- and nanoscales, which can be detected in far-field imaging. Compared with traditional nanometrology approaches like scanning electron microscopy (SEM), atomic force microscopy (AFM), and optical scatterometry, spectral imaging offers much higher throughput due to its large field of view (FOV), micrometer-scale imaging resolution, sensitivity to nm-scale feature geometric variations, and ability to be performed in-line and nondestructively. Thus, spectral imaging is an excellent choice for high-speed defect detection/classification in Si nanopillar arrays and potentially other types of large-area nanostructure arrays (LNAs) fabricated on Si wafers, glass sheets, and roll-to-roll webs. The origins of different types of nano-imprint patterning defects—including particle voids, etch delay, and nonfilling—and the unique ways in which they manifest as optical changes in the completed nanostructure arrays are discussed. With this understanding in mind, computer vision methods are applied to spectral image data to detect and classify various defects in a sample containing wine glass-shaped Si resonator arrays.

Atomized dielectric-based electrical discharge machining (EDM) is a novel machining process in which a thin film of moving fluid resulting from a spray acts as the dielectric in the interelectrode gap. In addition to acting as the dielectric, the thin film also helps to flush the debris away from EDM crater features and requires very small quantity of fluid in doing so. This results in significantly less dielectric consumption compared to the conventional EDM while yielding higher material removal rates and better debris flushing. This paper presents a model-based investigation of the mechanism of debris flushing in atomized dielectric-based EDM. A material removal model is used to predict the amount of debris removed in terms of number of particles ejected during a single EDM discharge. The dielectric material properties and atomization spray parameters are varied in order to produce different ejection conditions and crater geometries, respectively. Particles are ejected from the bottom of crater geometries. The model captures the asymmetry in particle motion caused by the dielectric film flow and predicts the percentage of debris flushed away from the crater center. It is also observed that crater shape and size of debris particles play a role in the amount of debris flushed away.

Graphene is an ideal reinforcement material for metal matrix composites (MMCs) owing to its high strength, high ductility, light weight, as well as good bonding with metal matrix. In this study, graphene nanoplatelets (GNPs) reinforced Inconel 718 composites are fabricated by selective laser melting (SLM) technique and processed under various postheat treatment schemes. It is found that the fabrication of GNPs-reinforced MMC using the SLM technique is a viable approach. The obtained composite possesses dense microstructure and enhanced tensile strength. Postheat treatments at two levels of solution temperature (980 and 1220 °C) for 1 h followed by two-step aging are carried out. The experimental results indicate that the addition of GNPs into Inconel 718 matrix results in significant strength improvement. Under the as-built condition, the ultimate tensile strengths (UTSs) of SLM Inconel 718 materials are 997 and 1447 MPa, respectively, at 0 and 4.4 vol % GNP content. The strengthening effect of GNPs is most prominent under the as-built condition, and the strength of as-built GNPs-reinforced Inconel 718 is higher than that of unreinforced Inconel 718 under any processing conditions. The formation of γ ′ and γ ″ precipitates is suppressed in the GNPs-reinforced composite under the aging condition due to the formation of metallic carbide (MC) carbide and the depletion of Nb. GNPs effectively inhibits grain growth during postheat treatment. Quantitative investigation of the various strengthening effects demonstrates that load transfer effect is dominating among all contributors.

Vibration-assisted nano-impact machining by loose abrasives (VANILA) is a newly developed process based on the atomic force microscope (AFM) platform, where the nanoabrasive (diamond particles) slurry is injected between the workpiece and the vibrating AFM probe. This study aims to use the commercial finite element method (FEM) software package abaqus to simulate the phase transformation experienced by the silicon workpiece and to study the effects of VANILA process parameters, such as impact speed, impact angle, and coefficient of friction between the nanoabrasive and silicon workpiece, on the volume of phase transformation of silicon. Among these three parameters, impact speed is found to have the most dominating effect on the phase transformation process, followed by impact angle and friction coefficient. It is found that the volumes for Si-VII, Si-VIII, and Si-X phases increase with the increase of impact speed from 100 m/s to 200 m/s. The phase volumes of Si-VII and Si-VIII are found to decrease slightly with the increase of friction coefficient from 0.05 to 0.5. The phase volumes for Si-VII, Si-VIII, and Si-X are found to increase with the increase of impact angles from 20 deg to 90 deg. Finally, the multiple linear regression modeling using a design of experiments is carried out to study the relationship among the three parameters and the volume of different phases of silicon.

This paper presents an investigation of green micromachining (GMM) forces during orthogonal micromachining green-state AlN ceramics. Green-state ceramics contain ceramic powders within a binder; processed samples are subsequently debound and sintered to obtain solid ceramic parts. An effective approach to create microscale features on ceramics is to use mechanical micromachining when the ceramics are at their green state. This approach, referred to as GMM, considerably reduces the forces and tool wear with respect to micromachining of sintered ceramics. As such, fundamental understanding on GMM of ceramics is critically needed. To this end, in this work, the force characteristics of powder injection molded AlN ceramics with two different binder states were experimentally investigated via orthogonal cutting. The effects of micromachining parameters on force components and specific energies were experimentally identified for a tungsten carbide (WC) and a single crystal diamond tools. As expected, the thrust forces were seen to be significantly larger than the cutting forces at low uncut chip thicknesses when using the carbide tool with its large edge radius. The cutting forces are found to be more sensitive to uncut chip thickness than the thrust forces are. When a sharp diamond tool is used, cutting forces are significantly larger than the thrust forces even for small uncut chip thicknesses. The specific energies follow an exponential decrease with increasing uncut chip thickness similar to the common trends in metal cutting. However, due to interaction characteristics between cutting edge and ceramic particles in the green body, evidence of plowing and rubbing along the cutting region was observed even with a sharp diamond tool.

As one of the most promising anode materials for high-capacity lithium ion batteries (LIBs), silicon nanowires (SiNWs) have been studied extensively. The metal-assisted chemical etching (MACE) is a low-cost and scalable method for SiNW synthesis. Nanoparticle emissions from the MACE process, however, are of grave concerns due to their hazardous effects on both occupational and public health. In this study, both airborne and aqueous nanoparticle emissions from the MACE process for SiNWs with three sizes of 90 nm, 120 nm, and 140 nm are experimentally investigated. The prepared SiNWs are used as anodes of LIB coin cells, and the experimental results reveal that the initial discharge and charge capacities of LIB electrodes are 3636 and 2721 mAh g −1 with 90 nm SiNWs, 3779 and 2712 mAh g −1 with 120 nm SiNWs, and 3611 and 2539 mAh g −1 with 140 nm SiNWs. It is found that for 1 kW h of LIB electrodes, the MACE process for 140 nm SiNWs produces a high concentration of airborne nanoparticle emissions of 2.48 × 10 9 particles/cm 3 ; the process for 120 nm SiNWs produces a high mass concentration of aqueous particle emissions, with a value of 9.95 × 10 5 mg/L. The findings in this study can provide experimental data of nanoparticle emissions from the MACE process for SiNWs for LIB applications and can help the environmental impact assessment and life cycle assessment of the technology in the future.

One of the limitations of commercially available metal additive manufacturing (AM) processes is the minimum feature size most processes can achieve. A proposed solution to bridge this gap is microscale selective laser sintering ( μ -SLS). The advent of this process creates a need for models which are able to predict the structural properties of sintered parts. While there are currently a number of good SLS models, the majority of these models predict sintering as a melting process which is accurate for microparticles. However, when particles tend to the nanoscale, sintering becomes a diffusion process dominated by grain boundary and surface diffusion between particles. As such, this paper presents an approach to model sintering by tracking the diffusion between nanoparticles on a bed scale. Phase field modeling (PFM) is used in this study to track the evolution of particles undergoing sintering. Changes in relative density are then calculated from the results of the PFM simulations. These results are compared to experimental data obtained from furnace heating done on dried copper nanoparticle inks, and the simulation constants are calibrated to match physical properties.

Opto-thermophoretic manipulation is an emerging field, which exploits the thermophoretic migration of particles and colloidal species under a light-controlled temperature gradient field. The entropically favorable photon–phonon conversion and widely applicable heat-directed migration make it promising for low-power manipulation of variable particles in different fluidic environments. By exploiting an optothermal substrate, versatile opto-thermophoretic manipulation of colloidal particles and biological objects can be achieved via optical heating. In this paper, we summarize the working principles, concepts, and applications of the recently developed opto-thermophoretic techniques. Opto-thermophoretic trapping, tweezing, assembly, and printing of colloidal particles and biological objects are discussed thoroughly. With their low-power operation, simple optics, and diverse functionalities, opto-thermophoretic manipulation techniques will offer great opportunities in materials science, nanomanufacturing, life sciences, colloidal science, and nanomedicine.

Miniaturization of components is one of the major demands of the today's technological advancement. Microslots are one of the widely used microfeature found in various industries such as automobile, aerospace, fuel cells and medical. Surface roughness of the microslots plays critical role in high precision applications such as medical field (e.g., drug eluting stent and microfilters). In this paper, abrasive flow finishing (AFF) process is used for finishing of the microslots (width 450 μ m) on surgical stainless steel workpiece that are fabricated by electrical discharge micromachining (EDμM). AFF medium is developed in-house and used for performing microslots finishing experiments. Developed medium not only helps in the removal of hard recast layer from the workpiece surfaces but also provides nano surface roughness. Parametric study of microslots finishing by AFF process is carried out with the help of central composite rotatable design (CCRD) method. The initial surface roughness on the microslots wall is in the range of 3.50 ± 0.10 μ m. After AFF, the surface roughness is reduced to 192 nm with a 94.56% improvement in the surface roughness. To understand physics of the AFF process, three-dimensional (3D) finite element (FE) viscoelastic model of the AFF process is developed. Later, a surface roughness simulation model is also proposed to predict the final surface roughness after the AFF process. Simulated results are in good agreement with the experimental results.

In this work, investigations were made for enhancing wear properties of rapid tooling (RT) by reinforcement of fillers (nanoscaled) for grinding applications. The RT has been prepared by using biocompatible composite material (BCCM) feed stock filament (consisting of Nylon 6 as a binder, reinforced with biocompatible nanoscale Al 2 O 3 particles) on fused deposition modeling (FDM) for the development of grinding wheel having customized wear-resistant properties. A comparative study has been conducted under dry sliding conditions in order to understand the tribological characteristics of FDM printed RT of BCCM and commercially used acrylonitrile butadiene styrene (ABS) material. This study also highlights the various wear mechanisms (such as adhesive, fatigue, and abrasive) encountered during experimentation. Finally, the FDM printed RT of proposed BCCM feedstock filament is more suitable for grinding applications especially in clinical dentistry.

To date, several additive manufacturing (AM) technologies have been developed for fabricating smart particle–polymer composites. Those techniques can control particle distributions to achieve gradient or heterogeneous properties and functions. Such manufacturing capability opened up new applications in many fields. However, it is still widely unknown how to design the localized material distribution to achieve desired product properties and functionalities. The correlation between microscale material distribution and macroscopic composite performance needs to be established. In our previous work, a novel magnetic field-assisted stereolithography (M-PSL) process was developed, for fabricating magnetic particle–polymer composites. In this work, we focused on the study of magnetic-field-responsive particle–polymer composite design with the aim of developing guidelines for predicting the magnetic-field-responsive properties of the composite. Microscale particle distribution parameters, including particle loading fraction, magnetic particle chain structure, microstructure orientation, and particle distribution patterns, were investigated. Their influences on the properties of particle–polymer liquid suspensions and properties of the three-dimensional (3D) printed composites were characterized. By utilizing the magnetic anisotropy properties of the printed composites, motions of the printed parts could be actuated at different positions in the applied magnetic field. Physical models were established to predict magnetic properties of the composite and trigger distance of fabricated parts. The predicted results agreed well with the experimental measurements, indicating the effectiveness of predicting macroscopic composite performance using microscale distribution data, and the feasibility of using the developed physical models to guide multimaterial and multifunctional composite design.

One of the greatest challenges in the manufacturing and development of nanotechnologies is the requirement for robust, reliable, and accurate characterization data. Presented here are the results of an interlaboratory comparison (ILC) brought about through multiple rounds of engagement with NanoSight Malvern and ten pan-European research facilities. Following refinement of the nanoparticle tracking analysis (NTA) technique, the size and concentration characterization of nanoparticles in liquid suspension was proven to be robust and reproducible for multiple sample types in monomodal, binary, or multimodal mixtures. The limits of measurement were shown to exceed the 30–600 nm range (with all system models), with percentage coefficients of variation (% CV) being calculated as sub 5% for monodisperse samples. Particle size distributions were also improved through the incorporation of the finite track length adjustment (FTLA) algorithm, which most noticeably acts to improve the resolution of multimodal sample mixtures. The addition of a software correction to account for variations between instruments also dramatically increased the accuracy and reproducibility of concentration measurements. When combined, the advances brought about during the interlaboratory comparisons allow for the simultaneous determination of accurate and precise nanoparticle sizing and concentration data in one measurement.

The importance of coatings in modern science and industry is great, and the system presented in this manuscript attempts to provide a method of creating high quality nanoparticle coatings with in situ sintering of nanoparticles. Dual regime nozzle creates close to optimum conditions for particle delivery and deposition and the addition of in situ thermally assisted coating makes it more productive. Preliminary results show systems uniform coating and in situ sintering capability.

Surface plasmon polaritons associated with light-nanoparticle interactions can result in dramatic enhancement of electromagnetic fields near and in the gaps between the particles, which can have a large effect on the sintering of these nanoparticles. For example, the plasmonic field enhancement within nanoparticle assemblies is affected by the particle size, spacing, interlayer distance, and light source properties. Computational analysis of plasmonic effects in three-dimensional (3D) nanoparticle packings are presented herein using 532 nm plane wave light. This analysis provides insight into the particle interactions both within and between adjacent layers for multilayer nanoparticle packings. Electric field enhancements up to 400-fold for transverse magnetic (TM) or X-polarized light and 26-fold for transverse electric (TE) or Y-polarized light are observed. It is observed that the thermo-optical properties of the nanoparticle packings change nonlinearly between 0 and 10 nm gap spacing due to the strong and nonlocal near-field interaction between the particles for TM polarized light, but this relationship is linear for TE polarized light. These studies help provide a foundation for understanding micro/nanoscale heating and heat transport for Cu nanoparticle packings under 532 nm light under different polarization for the photonic sintering of nanoparticle assemblies.

Thermal fiber drawing has emerged as a novel process for the continuous manufacturing of semiconductor and polymer nanoparticles. Yet a scalable production of metal nanoparticles by thermal drawing is not reported due to the low viscosity and high surface tension of molten metals. Here, we present a generic method for the scalable nanomanufacturing of metal nanoparticles via thermal drawing based on droplet break-up emulsification of immiscible polymer/metal systems. We experimentally show the scalable manufacturing of metal Sn nanoparticles (<100 nm) in polyethersulfone (PES) fibers as a model system. The underlying mechanism for the particle formation is revealed, and a strategy for the particle diameter control is proposed. This process opens a new pathway for scalable manufacturing of metal nanoparticles from liquid state facilitated solely by the hydrodynamic forces, which may find exciting photonic, electrical, or energy applications.

In spite of the great progress made toward addressing the challenge of particle contamination in nanomanufacturing, its deleterious effect on yield is still not negligible. This is particularly true for nanofabrication processes that involve close proximity or contact between two or more surfaces. One such process is Jet-and-Flash Imprint Lithography (J-FIL™), which involves the formation of a nanoscale liquid film between a patterned template and a substrate. In this process, the presence of any frontside particle taller than the liquid film thickness, which is typically sub-25 nm, can not only disrupt the continuity of this liquid film but also damage the expensive template upon contact. The detection of these particles has typically relied on the use of subwavelength optical techniques such as scatterometry that can suffer from low throughput for nanoscale particles. In this paper, a novel mechanics-based method has been proposed as an alternative to these techniques. It can provide a nearly 1000 × amplification of the particle size, thereby allowing for optical microscopy based detection. This technique has been supported by an experimentally validated multiphysics model which also allows for estimation of the loss in yield and potential contact-related template damage because of the particle encounter. Also, finer inspection of template damage needs to be carried out over a much smaller area, thereby increasing throughput of the overall process. This technique also has the potential for inline integration, thereby circumventing the need for separate tooling for subwavelength optical inspection of substrates.

Silver nanoparticles were electrodeposited from 0.3 M oxalic acid electrolyte on a pure aluminum working electrode under silver ion concentration-limited condition. A silver wire was held in a glass tube containing 1.0 M KCl solution as the counter electrode. Ion exchange between the glass tube and the main electrodeposition bath through a capillary was driven by the overpotentials as high as 10 V supplied by an electrochemical workstation. Due to the reaction between chlorine anion and silver cation to form AgCl solid at the Ag/AgCl electrode, the silver ion concentration-limited condition holds in the electrolyte. It is found that silver grows at the aluminum working electrode to form nanoparticles with an average size of about 52.4 ± 13.6 nm. With the increasing of the deposition time, the silver nanoparticles aggregate into clusters. The silver particle clusters are separated with approximately 112.6 ± 19.7 nm due to the hydrogen bubble-induced self-assembling, which is shown by the confined deposition of silver on a gold coating. The surface roughness of the aluminum substrate leads to the reduced uniformity of silver nanoparticle nucleation and growth.

A computational model to investigate the flushing of electric discharge machining (EDM) debris from the interelectrode gap during the spray-EDM process is developed. Spray-EDM differs from conventional EDM in that an atomized dielectric spray is used to generate a thin film that penetrates the interelectrode gap. The debris flushing in spray-EDM is investigated by developing models for three processes, viz., dielectric spray formation, film formation, and debris flushing. The range of spray system parameters including gas pressure and impingement angle that ensure formation of dielectric film on the surface is identified followed by the determination of dielectric film thickness and velocity. The debris flushing in conventional EDM with stationary dielectric and spray-EDM processes is then compared. It is observed that the dielectric film thickness and velocity play a significant role in removing the debris particles from the machining region. The model is used to determine the spray conditions that result in enhanced debris flushing with spray-EDM.

A new three-dimensional (3D) printing process designated as shockwave-induced freeform technique (SWIFT) is explored for fabricating microparts from nanopowders. SWIFT consists of generating shockwaves using a laser beam, applying these shocks to pressure sinter nanoparticles at room temperature, and creating structures and devices by the traditional layer-by-layer formation. Shockwave cold compaction of nanoscale powders has the capability to overcome limitations, such as shrinkage, porosity, rough surface, and wide tolerance, normally encountered in hot sintering processes, such as selective laser sintering. In this study, the window of operating parameters and the underlying physics of SWIFT were investigated using a high-energy Q-switched Nd: YAG laser and nanodiamond (ND) powders. Results indicate the potential of SWIFT for fabricating high-performance diamond microtools with high aspect ratios, smooth surfaces, and sharp edges. The drawback is that the SWIFT process does not work for micro-sized powders.

One of the challenges in making layered metal composites reinforced at interfaces has been controlling the dispersion and microstructure of the reinforcement particles. The reinforcement elements are typically applied at the interface by manual spreading using brush or by immersing the substrate in a suspension. In this study, an ultrasonic spraying technique has been used to deposit silicon carbide (SiC) nanoparticles on aluminum 6061 (Al6061) substrate foils to fabricate a laminate metal composite to control the deposited structure. The suspension parameters and the spraying parameters were investigated, and their influence on the deposited microstructure was analyzed. The laminate composite was consolidated using hot compaction, and a three-point bend test was performed to evaluate the mechanical properties. The yield and ultimate flexural strengths of the laminate composite reinforced with SiC nanoparticles increased by 32% and 15%, respectively, compared with those of the unreinforced sample prepared at the same condition.