The synthesis of vertically aligned carbon nanotubes (CNTs), also referred to as CNT forest, by chemical vapor deposition (CVD) is an intricate process that is sensitive to multiple factors other than control of temperature, pressure, and gas flows. In particular, growth is highly sensitive to factors like ambient humidity, as well as small quantities of oxygen-containing species and carbon deposits inside the reactor. These typically uncontrolled factors significantly affect growth reproducibility and hinders the fundamental study of process–structure–property relationship for these emerging materials. Accordingly, universally applicable design modifications and process steps toward improving growth consistency are sought after. In this study, we introduce two new modifications to our custom-designed multizone rapid thermal CVD reactor and demonstrate their impact on growth: (1) reconfiguring the inlet gas plumbing to add a gas purifier to the helium (He) line, and (2) designing a new support wafer for consistent loading of substrates. We use statistical analysis to test the effectiveness of these modifications in improving growth and reducing variability of both CNT forest height and density. Analysis of our experimental results and hypothesis testing show that combining the implementation of He purifier with the redesigned support wafer increases forest height and reduces the variability in height (17-folds), both at statistically significant and practically significant levels.

Microassembly systems utilizing precision robotics have long been used for realizing three-dimensional microstructures such as microsystems and microrobots. Prior to assembly, microscale components are fabricated using micro-electromechanical-system (MEMS) technology. The microassembly system then directs a microgripper through a series of automated or human-controlled pick-and-place operations. In this paper, we describe a novel custom microassembly system, named NEXUS, that can be used to prototype MEMS microrobots. The NEXUS integrates multi-degrees-of-freedom (DOF) precision positioners, microscope computer vision, and microscale process tools such as a microgripper and vacuum tip. A semi-autonomous human–machine interface (HMI) was programmed to allow the operator to interact with the microassembly system. The NEXUS human–machine interface includes multiple functions, such as positioning, target detection, visual servoing, and inspection. The microassembly system's HMI was used by operators to assemble various three-dimensional microrobots such as the Solarpede, a novel light-powered stick-and-slip mobile microcrawler. Experimental results are reported in this paper to evaluate the system's semi-autonomous capabilities in terms of assembly rate and yield and compare them to purely teleoperated assembly performance. Results show that the semi-automated capabilities of the microassembly system's HMI offer a more consistent assembly rate of microrobot components and are less reliant on the operator's experience and skill.

Acoustic radiation force in the near-field of a vibrating source can be utilized to lift and transport objects, which provides a noncontact driving technology in addition to maglev. This paper presents a novel design of a self-levitated planar stage based on near-field acoustic transportation. A closed-loop system is proposed to design a capacitance surface encoder to provide direct two-dimensional (2D) position feedback. A dynamic model based on the Reynolds equation is established to study its driving mechanism. A prototype including the levitation stage, encoder, and controller is implemented to demonstrate the potential of arbitrary trajectory tracking in two-dimensional space.

The plunger part in temporary electronic connectors is traditionally fabricated by micromachining. Progressive forming of microparts by directly using sheet metals is developed and proven to be an efficient microforming process to overcome some intrinsic drawback in realization of mass production of microparts. By employing this unique micromanufacturing process, an efficient approach with progressive microforming is developed to fabricate plunger-shaped microparts. In this endeavor, a progressive forming system for making microplungers using extrusion and blanking operations is developed, and the grain size effect affected deformation behaviors and of surface qualities of the microformed parts are studied. The knowledge for fabrication of plunger-shaped microparts via progressive microforming is developed, and the in-depth understanding and insight into the deformation behaviors and tailoring the product quality and properties will facilitate the design and development of the forming process by using this unique microforming approach.

A custom-made stereolithographic printer using a digital light processing optical (DLP) system based on a digital micromirror device (DMD) was characterized. Several sizes of slanted grooved micromixers (SGM) were produced and typical dimensions were measured and compared to nominal values. The results show that the developed SLA printer is precise enough to be used for prototyping of larger microfluidic devices. The lateral geometries of the smallest printed micromixer designs deviated less than 20 μ m from the nominal values and related feature depths deviated for less than 15 μ m. However, further modifications are needed in order to improve the repeatability, accuracy, and printing resolution.

We present an inexpensive, repeatable, and efficient method of patterning silver nanowires onto polydimethylsiloxane (PDMS) using a mold-based approach. A micromilling machine is used to prepare an aluminum mold with a raised pattern so that PDMS cured in these molds is imprinted with the design. A solution of silver nanowires and ethanol can then be injected into the pattern. This method can be used to pattern silver nanowires onto PDMS in any two-dimensional (2D) layout, meaning it can be extended to produce a wide range of PDMS/silver nanowire-based sensors and devices. We demonstrate this by the development of two separate patterns. An intricate logo is developed in order to demonstrate the capability of patterning curved and sharp edges, and a strain gauge is developed in order to demonstrate a functional device.

Lightweight microstructures with high area-to-mass ratios, or low surface densities, show great potential applications in microrobots, soft electronics, medical devices, and solar sailing. However, the bending stiffness of such microstructures is usually too low to work effectively. In order to obtain active microstructures with enhanced bending stiffness, a new design for thermally actuated multilayered metallic microstructures with high area-to-mass ratios is presented in this article. The microstructures made of aluminum and NiTi alloy are fabricated to demonstrate the feasibility of vertical deployment of such microstructures under thermal actuation. The concept design and working principle of designed multilayered metallic microstructures are based on symmetrical deposition of metals Al\NiTi\NiTi\Al, followed by practical microfabrication processes, such as photolithography, physical vapor deposition (PVD), and dry etch. The area-to-mass ratios of such microstructures could be up to 400 m 2 /kg. Then, experiments for electrical characterization are set up for thermal actuation or Joule heating. Besides that, the equivalent resistances of such microstructures with regard to temperatures are calibrated, allowing for the determination of in situ temperatures of deformed microstructures when being heated in the vacuum chamber of scanning electron microscope (SEM). Finally, vertical deployment of such thin microstructures is detected and measured, which validates the feasibility of stiffness enhancement through the symmetrical design and thermal actuation.

This paper presents the development of a prototype exfoliation tool and process for the fabrication of thin-film, single crystal silicon, which is a key material for creating high-performance flexible electronics. The process described in this paper is compatible with traditional wafer-based, complementary metal–oxide–semiconductor (CMOS) fabrication techniques, which enables high-performance devices fabricated using CMOS processes to be easily integrated into flexible electronic products like wearable or internet of things devices. The exfoliation method presented in this paper uses an electroplated nickel tensile layer and tension-controlled handle layer to propagate a crack across a wafer while controlling film thickness and reducing the surface roughness of the exfoliated devices as compared with previously reported exfoliation methods. Using this exfoliation tool, thin-film silicon samples are produced with a typical average surface roughness of 75 nm and a thickness that can be set anywhere between 5 μ m and 35 μ m by changing the exfoliation parameters.

Fresnel zone plates (FZPs) have been gaining a significant attention by industry due to their compact design and light weight. Different fabrication methods have been reported and used for their manufacture but they are relatively expensive. This research proposes a new low-cost one-step fabrication method that utilizes nanosecond laser selective oxidation of titanium coatings on glass substrates and thus to form titanium dioxide (TiO 2 ) nanoscale films with different thicknesses by controlling the laser fluence and the scanning speed. In this way, phase-shifting FZPs were manufactured, where the TiO 2 thin-films acted as a phase shifter for the reflected light, while the gain in phase depended on the film thickness. A model was created to analyze the performance of such FZPs based on the scalar theory. Finally, phase-shifting FZPs were fabricated for different operating wavelengths by varying the film thickness and a measurement setup was built to compare experimental and theoretical results. A good agreement between these results was achieved, and an FZP efficiency of 5.5% to 20.9% was obtained when varying the wavelength and the oxide thicknesses of the zones.

This paper reports the development of an original design of chip breaker in a metal-matrix polycrystalline diamond (MMPCD) insert brazed into a milling tool. The research entailed finite element (FE) design, laser simulation, laser fabrication, and machining tests. FE analysis was performed to evaluate the effectiveness of different designs of chip breaker, under specified conditions when milling aluminum alloy (Al A356). Then, the ablation performance of an MMPCD workpiece was characterized by ablating single trenches under different conditions. The profiles of the generated trenches were analyzed and fed into a simulation tool to examine the resultant thickness of ablated layers for different process conditions, and to predict the obtainable shape when ablating multilayers. Next, the geometry of the designated chip breaker was sliced into a number of layers to be ablated sequentially. Different ablation scenarios were experimentally investigated to identify the optimum processing conditions. The results showed that an ns laser utilized in a controllable manner successfully produced the necessary three-dimensional feature of an intricate chip breaker with high surface quality (Ra in the submicron range), tight dimensional accuracy (maximum dimensional error was less than 4%), and in an acceptable processing time (≈51 s). Finally, two different inserts brazed in milling tools, with and without the chip breaker, were tested in real milling trials. Superior performance of the insert with chip breaker was demonstrated by the curled chips formed and the significant reduction of obtained surface roughness compared to the surface produced by the insert without chip breaker.

Oscillating microprobes avoid high stress and the sticking effect during contact between microprobe and measured surface. The full performance and application scope of oscillating microprobes can be explored and utilized once the reliable prediction of the microprobe contact behavior is understood. Here, an improved contact model considering adhesion forces, surface roughness, and viscoelastic damping for oscillating microprobes is presented and it is validated by exemplary measurements utilizing a uniaxially oscillating electrostatic microprobe. These results show that the nondestructive identification of material classes seems to be feasible by evaluating the phase shift between the sinusoidal signals of sensor and actuator, respectively.

This paper presents the design and characteristics of a new two-dimensional nonresonant tertiary motion generator which is based on the flextensional structure. A tool holder connects two perpendicularly placed flextensional actuators with flexure hinges which decouple the motion outputs from the two actuators. Piezoelectric stacks, which are preloaded through precision screws, are used to provide input displacements. By balancing the requirements of driving current, stiffness, and the displacement amplification ratio, the proposed design is targeted to operate at above 10 kHz with two-dimensional vibrations amplitude of 10 μ m in each direction. Technical difficulties in driving a nonresonant mode piezoelectric actuator at a high frequency are discussed. The solutions and optimization procedures are presented in this paper. The design is optimized by finite-element simulation; and the results are presented and verified by our prototype design.

One of the major challenges in nanoscale manufacturing is defect control because it is difficult to measure nanoscale features in-line with the manufacturing process. Optical inspection typically is not an option at the nanoscale level due to the diffraction limit of light, and without inspection high scrap rates can occur. Therefore, this paper presents an atomic force microscopy (AFM)-based inspection system that can be rapidly implemented in-line with other nanomanufacturing processes. Atomic force microscopy is capable of producing very high resolution (subnanometer-scale) surface topology measurements and is widely utilized in scientific and industrial applications, but has not been implemented in-line with manufacturing systems, primarily because of the large setup time typically required to take an AFM measurement. This paper introduces the design of a mechanical wafer-alignment device to enable in-line AFM metrology in nanoscale manufacturing by dramatically reducing AFM metrology setup time. The device consists of three pins that exactly constrain the wafer and a nesting force applied by a flexure to keep the wafer in contact with the pins. Kinematic couplings precisely mate the device below a flexure stage containing an array of AFM microchips which are used to make nanoscale measurements on the surface of the semiconductor wafer. This passive alignment system reduces the wafer setup time to less than 1 min and produces a lateral positioning accuracy that is on the order of ∼1 μ m.

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.

A suitable tooling strategy is identified to enable mass production of a microreactor baseplate via injection moulding. A bottom grooved micromixer design suitable for micromilling of a tool insert is developed. To identify suitable polymer and process parameters, injection moulding simulations are performed. Mesh generation is described; two approaches of gate description as well as mould temperature control in simulation software are discussed. Three materials are examined from the injection moulding point of view, polystyrene (PS), cyclic olefin copolymer (COC), and polyether ether ketone (PEEK). A microreactor baseplate is produced by injection moulding of PS.

The advances in the Terahertz (THz) technology drive the needs for the design and manufacture of waveguide devices that integrate complex three-dimensional (3D) miniaturized components with meso- and micro-scale functional features and structures. Typical dimensions of the waveguide functional structures are in the range from 200 μ m to 50 μ m and dimensions decrease with the increase in the operating frequency of the waveguide devices. Technological requirements that are critical for achieving the desired microwave filtering performance of the waveguides include geometrical accuracy, alignment between functional features and surface integrity. In this context, this paper presents a novel manufacturing route for the scaled-up production of THz components that integrate computer numerical control (CNC) milling and laser micromachining. A solution to overcome the resulting tapering of the laser-machined structures while achieving a high accuracy and surface integrity of the machined features is applied in this research. In addition, an approach for two-side processing of waveguide structures within one laser machining setup is described. The capabilities of the proposed manufacturing process chain are demonstrated on two THz waveguide components that are functionally tested to assess the effects of the achieved machining results on devices' performance. Experimental results show that the proposed process chain can address the manufacturing requirements of THz waveguide filters, in particular the process chain is capable of producing filters with geometrical accuracy better than 10 μ m, side wall taper angle deviation of less than 1 deg from vertical (90 deg), waveguide cavities corner radius better than 15 μ m, and surface roughness (Sa) better than 1.5 μ m. The manufacturing efficiency demonstrated in this feasibility study also provides sufficient evidences to argue that the proposed multistage manufacturing technique is a very promising solution for the serial production of small to medium batches of THz waveguide components. Finally, analyses of the manufacturing capabilities of the proposed process chain and the photoresist-based technologies were performed to clearly demonstrate the advantages of the proposed process chain over current waveguide fabrication solutions.

This paper reports on design, fabrication, and characterization of a microfilter to be used in biomedical applications. The microfilter, with mesh of 80 μ m, is fabricated by micro-injection molding process in polymeric material (polyoxymethylene (POM)) using a steel mold manufactured by micro-electrical discharge machining process. The characteristics of the filter are investigated by numerical simulation in order to define a suitable geometry for micro-injection molding. Then, different process configurations of parameters (melt temperature, injection velocity, mold temperature, holding pressure and time, cooling time, pressure limit) are tested in order to obtain the complete part filling via micro-injection molding process preventing any defects. Finally, the component is dimensionally characterized and the process parameters optimized to obtain the maximum filtration capacity.

Wrinkling of thin films is a strain-driven process that enables scalable and low-cost fabrication of periodic micro- and nano-scale patterns. In the past, single-period sinusoidal wrinkles have been applied for thin-film metrology and microfluidics applications. However, real-world adoption of this process beyond these specific applications is limited by the inability to predictively fabricate a variety of complex functional patterns. This is primarily due to the inability of current tools and techniques to provide the means for applying large, accurate, and nonequal biaxial strains. For example, the existing biaxial tensile stages are inappropriate because they are too large to fit within the vacuum chambers that are required for thin-film deposition/growth during wrinkling. Herein, we have designed a compact biaxial tensile stage that enables (i) applying large and accurate strains to elastomeric films and (ii) in situ visualization of wrinkle formation. This stage enables one to stretch a 37.5 mm long film by 33.5% with a strain resolution of 0.027% and maintains a registration accuracy of 7 μ m over repeated registrations of the stage to a custom-assembled vision system. Herein, we also demonstrate the utility of the stage in (i) studying the wrinkling process and (ii) fabricating complex wrinkled patterns that are inaccessible via other techniques. Specifically, we demonstrate that (i) spatial nonuniformity in the patterns is limited to 6.5%, (ii) one-dimensional (1D) single-period wrinkles of nominal period 2.3 μ m transition into the period-doubled mode when the compressive strain due to prestretch release of plasma-oxidized polydimethylsiloxane (PDMS) film exceeds ∼18%, and (iii) asymmetric two-dimensional (2D) wrinkles can be fabricated by tuning the strain state and/or the actuation path, i.e., the strain history. Thus, this tensile stage opens up the design space for fabricating and tuning complex wrinkled patterns and enables extracting empirical process knowledge via in situ visualization of wrinkle formation.

Atomization-based cutting fluid systems (ACFs) are increasingly being used in micromachining applications to provide cooling and lubrication to the tool–chip interface. In this research, a shielding nozzle design is presented. A computational fluid dynamic model is developed to perform parameter analysis of the design. The numerical simulations were accomplished using the Eulerian approach to the continuous phase and a Lagrangian approach for droplet tracking. Based on the results of the simulations it is determined that the shielding nozzle is effective at providing droplets to the cutting surface at an appropriate speed and size to create a lubricating microfilm.

Mass-production of microfluidic devices is important for biomedical applications in which disposable devices are widely used. Injection molding is a well-known process for the production of devices on a mass scale at low-cost. In this study, the injection molding process is adapted for the fabrication of a microfluidic device with a single microchannel. To increase the product quality, high-precision mechanical machining is utilized for the manufacturing of the mold of the microfluidic device. A conventional injection molding machine is implemented in the process. Injection molding was performed at different mold temperatures. The warpage of the injected pieces was characterized by measuring the part deformation. The effect of the mold temperature on the quality of the final device was assessed in terms of the part deformation and bonding quality. From the experimental results, one-to-one correspondence between the warpage and the bonding quality of the molded pieces was observed. It was found that as the warpage of the pieces decreases, the bonding quality increases. A maximum point for the breaking pressure of the bonding and the minimum point for the warpage were found at the same mold temperature. This mold temperature was named as the optimum temperature for the designed microfluidic device. It was observed that the produced microfluidic devices at the mold temperature of 45 °C were able to withstand pressures up to 74 bar.