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Editorial

J. Micro Nano-Manuf. 2016;4(4):040201-040201-1. doi:10.1115/1.4034644.
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Many fabrication techniques have demonstrated the ability to fabricate small quantities of nanomaterials, nanostructures, and nanodevices for device testing purposes. Such nanoscale devices have novel physical, chemical, and biological properties that derive from their nano-to-meso length scales, where unique properties between atomic and bulk behaviors can be obtained. The design and fabrication of such devices is a field of active research over the world. However, manufacturing such devices at an industrially relevant scale requires scalable production of nanomaterials, nanostructures, devices, and systems while retaining functional reliability, low cost, and high throughput. The innovation of new processes for large-area continuous manufacturing of nanomaterials and mesoscale structures assembled from these nanomaterials is a key component of this thrust. Such processes may include top-down and bottom-up approaches as well as self-assembly and hybrid processes, e.g., integration of top-down and bottom-up approaches via physical, chemical, biological, and thermal means. Control of such processes requires understanding of the process physics, thus creating the need for theoretical and computational developments related to nanoscale phenomenon that are relevant to control of product quality, reliability, and throughput. Another critical need is reliable, high-speed, high-resolution, online metrology and real-time control. This includes design principles and architectures for nanoscale measurement and processing as well as new design automation tools for assembling systems of large numbers of heterogeneous nanocomponents.

Commentary by Dr. Valentin Fuster

Research Papers

J. Micro Nano-Manuf. 2016;4(4):041001-041001-7. doi:10.1115/1.4034607.
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Nanotechnology has been presenting successful applications in several fields, such as electronics, medicine, energy, and new materials. However, the high cost of investment in facilities, equipment, and materials as well as the lack of some experimental analysis at the nanoscale can limit research in nanotechnology. The implementation of accurate computer models can alleviate this problem. This research investigates the Leidenfrost effect at the nanoscale using molecular dynamics (MDs) simulation. Models of water droplets with diameters of 4 nm and 10 nm were simulated over gold and silicon substrates. To induce the Leidenfrost effect, droplets at 293 K were deposited on heated substrates at 373 K. As a baseline, simulations were run with substrates at room temperature (293 K). Results show that for substrates at 293 K, the 4 nm droplet has higher position variability than the 10 nm droplets. In addition, for substrates at 373 K, the 4 nm droplets have higher velocities than the 10 nm droplets. The wettability of the substrate also influences the Leidenfrost effect. Droplets over the gold substrate, which has hydrophobic characteristics, have higher velocities as compared to droplets over silicon that has a hydrophilic behavior. Moreover, the Leidenfrost effect was observed at the boiling temperature of water (373 K) which is a significantly lower temperature than reported in previous experiments at the microscale. This research lays the foundation for investigating the fluid–structure interaction within several droplet based micro- and nano-manufacturing processes.

Commentary by Dr. Valentin Fuster
J. Micro Nano-Manuf. 2016;4(4):041002-041002-5. doi:10.1115/1.4034643.

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.

Commentary by Dr. Valentin Fuster
J. Micro Nano-Manuf. 2016;4(4):041003-041003-7. doi:10.1115/1.4034608.

Presently, nanomanufacturing capabilities limit the commercialization of a broader range of nanoscale structures with higher complexity, greater precision and accuracy, and a substantially improved performance. Atomic force microscopy (AFM)-based nanomachining is a promising technique to address current limitations and is considered a potential manufacturing (MFG) tool for operations such as machining, patterning, and assembling with in situ metrology and visualization. Most existing techniques for fabrication of nanofluidic channels involve the use of electron-beam lithography, which is a very expensive process that requires a lengthy calibration procedure. In this work, atomic force microscopy (AFM) is employed in the fabrication of nanofluidic channels for medical applications. Channels with various depths and widths are fabricated using AFM indentation and scratching. A nanoscale channel is mainly used in the study of the molecular behavior at single molecule level. The resulting device can be used for detecting, analyzing and separating biomolecules, DNA stretching, and separation of elite group of lysosome and other viruses. The nanochannels are integrated between microchannels and act as filters to separate biomolecules. Sharply developed vertical microchannels are produced from deep reaction ion etching. Poly-dimethylsiloxane (PDMS) bonding is performed to close the top surface of the silicon device. An experimental setup is used for testing by flowing fluid through the channels. A cost evaluation shows 47.7% manufacturing-time and 60.6% manufacturing-cost savings, compared to more traditional processes.

Commentary by Dr. Valentin Fuster
J. Micro Nano-Manuf. 2016;4(4):041004-041004-8. doi:10.1115/1.4034609.
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Widespread adoption of carbon nanomaterials has been hindered by inefficient production and utilization. A recently developed method has shown possibility to directly synthesize bulk nanostructured nonwoven materials from catalytically deposited carbon nanofibers (CNFs). The basic manufacturing scheme involves constraining carbon nanofiber growth to create three-dimensionally featured, macroscale products. Although previously demonstrated as a proof of concept, the possibilities and pitfalls of the method at a larger scale have not yet been explored. In this work, the basic foundation for using the constrained formation of fibrous nanostructures (CoFFiN) process is established by testing feasibility in larger volumes (as much as 2000% greater than initial experiments) and by noting the macroscale carbon growth characteristics. It has been found that a variety of factors contribute to determining the basic qualities of the macroscale fiber collection (nonwoven material), and there are tunable parameters at the catalytic and constraint levels. The results of this work have established that monolithic structures of nonwoven carbon nanofibers can be created with centimeter dimensions in a variety of cross-sectional shapes. The only limit to scale noted is the tendency for nanofibers to entangle with one another during growth and self-restrict outward expansion to the mold walls. This may be addressed by pregrowing carbon before placement or selective placement of the catalyst in the mold.

Commentary by Dr. Valentin Fuster
J. Micro Nano-Manuf. 2016;4(4):041005-041005-6. doi:10.1115/1.4034611.
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The purpose of this work is to introduce a new fabrication technique for creating a fluidic platform with embedded micro- or nanoscale channels. This new technique includes: (1) a three-axis robotic dispensing system for drawing micro/nanoscale suspended polymer fibers at prescribed locations, combined with (2) dry film resist photolithography, and (3) replica molding. This new technique provides flexibility and precise control of the micro- and nano-channel location with the ability to create multiple channels of varying sizes embedded in a single fluidic platform. These types of micro/nanofluidic platforms are attractive for numerous applications, such as the separation of biomolecules, cell transport, and transport across cell membranes via electroporation. The focus of this work is on the development of a fabrication technique for the creation of a nanoscale electroporation device.

Commentary by Dr. Valentin Fuster
J. Micro Nano-Manuf. 2016;4(4):041006-041006-8. doi:10.1115/1.4034610.

This paper introduces a low-cost, automated wafer alignment system capable of submicron wafer positioning repeatability. Accurate wafer alignment is critical in a number of nanomanufacturing and nanometrology applications where it is necessary to be able to overlay patterns between fabrication steps or measure the same spot on a wafer over and over again throughout the manufacturing process. The system presented in this paper was designed to support high-throughput nanoscale metrology where the goal is to be able to rapidly and consistently measure the same features on all the wafers in a wafer carrier without the need for slow and expensive vision-based alignment systems to find and measure the desired features. The wafer alignment system demonstrated in this paper consists of a three-pin passive wafer alignment stage, a voice coil actuated nesting force applicator, a three degrees-of-freedom (DOFs) wafer handling robot, and a wafer cassette. In this system, the wafer handling robot takes a wafer from the wafer cassette and loads it on to the wafer alignment stage. The voice coil actuator is then used to load the wafer against the three pins in the wafer alignment system and align the wafer to an atomic force microscope (AFM)-based metrology system. This simple system is able to achieve a throughput of 60 wafers/h with a positional alignment repeatability of 283 nm in the x-direction, 530 nm in the y-direction, and 398 nm in the z-direction for a total capital cost of less than $1800.

Commentary by Dr. Valentin Fuster
J. Micro Nano-Manuf. 2016;4(4):041007-041007-9. doi:10.1115/1.4034641.

Transparent polycrystalline yttrium aluminum garnet (YAG) ceramics have garnered an increased level of interest for high-power laser applications due to their ability to be manufactured in large sizes and to be doped in relatively substantial concentrations. However, surface characteristics have a direct effect on the lasing ability of these materials, and a lack of a fundamental understanding of the polishing mechanisms of these ceramics remains a challenge to their utilization. The aim of this paper is to study the polishing characteristics of YAG ceramics using magnetic field-assisted finishing (MAF). MAF is a useful process for studying the polishing characteristics of a material due to the extensive variability of, and fine control over, the polishing parameters. An experimental setup was developed for YAG ceramic workpieces, and using this equipment with diamond abrasives, the surfaces were polished to subnanometer scales. When polishing these subnanometer surfaces with 0–0.1 μm mean diameter diamond abrasive, the severity of the initial surface defects governed whether improvements to the surface would occur at these locations. Polishing subnanometer surfaces with colloidal silica abrasive caused a worsening of defects, resulting in increasing roughness. Colloidal silica causes uneven material removal between grains and an increase in material removal at grain boundaries causing the grain structure of the YAG ceramic workpiece to become pronounced. This effect also occurred with either abrasive when polishing with iron particles, used in MAF to press abrasives against a workpiece surface, that are smaller than the grain size of the YAG ceramic.

Commentary by Dr. Valentin Fuster
J. Micro Nano-Manuf. 2016;4(4):041008-041008-7. doi:10.1115/1.4034612.

Thermal fiber drawing process has emerged as a promising nanomanufacturing process to generate high-throughput, well aligned, and indefinitely long micro/nanostructures. However, scalable fabrication of metal–polymer nanocomposite is still a challenge, since it is still very difficult to control metal core geometry at nanoscale due to the low-viscosity and high-surface energy of molten metals in cladding materials (e.g., polymer or glass). Here, we show that a scalable nanomanufacture of metal–polymer nanocomposite via thermal fiber drawing is possible. Polyethersulfone (PES) fibers embedded with Sn nanoparticles (<200 nm) were produced by the iterative size reduction thermal fiber drawing. A post-characterization procedure was developed to successfully reveal the metal core geometry at submicron scale. A three-stage control mechanism is proposed to realize the possible control of the metal nanoparticle morphology. This thermal drawing approach promises a scalable production of metal–polymer nanocomposite fibers with unique physicochemical properties for exciting new functionalities.

Commentary by Dr. Valentin Fuster

Technology Review

J. Micro Nano-Manuf. 2016;4(4):044001-044001-12. doi:10.1115/1.4033968.
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Smart goods are everyday products with wireless connection to cloud computing enabling cost-effective strategies for embedded computation, memory and sensing. A 2015 workshop sponsored by the National Science Foundation and the Oregon Nanoscience and Microtechnologies Institute brought industry and academic leaders together in the Pacific Northwest to help identify future manufacturing research needs in this emerging industry. Workshop findings show that the impetus exists to drive the costs of smart goods lower and several technological challenges stand in the way. This paper summarizes the outcomes of the workshop including the current state of practice, future potential, technological gaps, and research recommendations to realize lower cost routes to manufacture smart goods.

Commentary by Dr. Valentin Fuster

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