Academic literature on the topic 'Microscale fabrication process'

Three-dimensional printing technology has been implemented in microfluidic mold fabrication due to its freedom of design, speed, and low-cost fabrication. To facilitate mold fabrication processes and avoid the complexities of the soft lithography technique, we offer a non-sacrificial approach to fabricate microscale features along with mesoscale features using Stereolithography (SLA) printers to assemble a modular microfluidic mold. This helps with addressing an existing limitation with fabricating complex and time-consuming micro/mesoscale devices. The process flow, optimization of print time and feature resolution, alignments of modular devices, and the advantages and limitations with the offered technique are discussed in this paper.

Using liquid crystalline suspension of the phage, we successfully fabricated nano- and microscale pure phage fibers. Through a near field electrospinning process, we fabricated the desired phage fiber pattern with tunable direction and spacing.

Silicon nanowires are widely used for sensing applications due to their outstanding mechanical, electrical, and optical properties. However, one of the major challenges involves introducing silicon-nanowire arrays to a specific layout location with reproducible and controllable dimensions. Indeed, for integration with microscale structures and circuits, a monolithic wafer-level process based on a top-down silicon-nanowire array fabrication method is essential. For sensors in various electromechanical and photoelectric applications, the need for silicon nanowires (as a functional building block) is increasing, and thus monolithic integration is highly required. In this paper, a novel top-down method for fabricating vertically-stacked silicon-nanowire arrays is presented. This method enables the fabrication of lateral silicon-nanowire arrays in a vertical direction, as well as the fabrication of an increased number of silicon nanowires on a finite dimension. The proposed fabrication method uses a number of processes: photolithography, deep reactive-ion etching, and wet oxidation. In applying the proposed method, a vertically-aligned silicon-nanowire array, in which a single layer consists of three vertical layers with 20 silicon nanowires, is fabricated and analyzed. The diamond-shaped cross-sectional dimension of a single silicon nanowire is approximately 300 nm in width and 20 μm in length. The developed method is expected to result in highly-sensitive, reproducible, and low-cost silicon-nanowire sensors for various biomedical applications.

3D printing by two-photon polymerization enables the fabrication of microstructures with complex shapes and critical dimensions of a few hundreds of nanometers. On state-of-the art commercial two-photon polymerization systems, an immense 3D design freedom can be put into practice by direct laser writing using a precise fabrication technology, which makes this approach highly attractive for different applications on the microscale, such as microrobotics, micro-optics, or biosensing. However, navigating the different possible configurations and selecting the optimal parameters for the fabrication process often requires intensive testing and optimization. In addition to the more established acrylate-based resins, there is a growing interest in the use of soft materials. In this paper, we demonstrate the fabrication of various microscale structures by two-photon polymerization using a Nanoscribe Photonic Professional GT+ commercial system. Furthermore, we describe the different configurations of the system and parameter selection, as well as commercial resins and their chemical and mechanical properties. Finally, we provide a short guide aiming to serve as starting point for the two-photon polymerization-based fabrication of various microscale architectures with distinct characteristics.

Microscale polyurethane modified epoxy resin film has been fabricated using MEMS tehnologies in the present paper. The effect of different process conditions on the thickness of fabricated film was discussed. The microscale film shows smooth and uniform surface morphology. The tensile test of the film by DMA indicates its tensile strength and Young's modulus are approximately 55MPa and 1.8GPa, respectively. The fracture section of the film was characterized by SEM. In addition, the interface bonding strength of the fabricated film between Ni substrate is much higher than Parylene-C and SU-8. This microscale polymer film is promising in several smart MEMS fields, especially bio-MEMS structures.

Moiré grating is a basic optical component, and can be used in various moiré methods. The conventional grating fabrication technology is based on photolithography and holographic interferometry, however, it requires complex optical components and is very difficult to put into practice. In this study, nanoimprint lithography (NIL), or rather, hot embossing lithography (HEL), is proposed for producing high frequency grating. Compared with silicon mold, holographic moiré grating mold costs less and is not easy to break, thus is chosen to be the mold in HEL. Using this mold and the hot embossing system, the grating structure can be transferred to the polymer after HEL process. Through a number of experiments, the process parameters were optimized and gratings were successfully fabricated. The multi-scale morphology of the fabricated gratings was then characterized by scanning electron microscope (SEM), atomic force microscope (AFM) and moiré interferometry. The microscale images observed by AFM and SEM show the regulate dots with equal spacing and the macroscale moiré patterns illuminate the excellent qualities of fabricated grating in a large area. The successful experimental results demonstrate the feasibility of the grating fabricated by HEL for the moiré measurement.

Abstract Social distancing measures due to the SARS-CoV-2 virus have profoundly challenged the educational experimental work. We have sought to remediate this issue by designing a series of low cost, low risk, quick, and qualitative electrochemistry and corrosion experiments to be performed in the student’s homes at the microscale with a kit provided by the teacher. One such experience is the electroplating of Sn from an aqueous chloride solution using readily available soldering wires (e.g., Sn–Pb alloy, or Sn–Ag–Cu alloy). This process catches students’ attention due to its simplicity and variety of possible applications that include corrosion protection, fabrication of electronic components, plating of cooking utensils, lithium batteries, etc.

The rapid development of smart technologies is accelerating the growing demand for microscale energy storage devices. This work reports a facile and practical approach to fabricating interdigitated graphene micro-patterns through the LSC process accompanied by the l-ascorbic acid (L-AA) and preheating treatment. Our work offered a higher degree of GO reduction than the conventional microfabrication. It significantly shortened the overall processing time to obtain the micro-patterns with improved electrical and electrochemical performances. The interdigitated MSC composed of 16 electrodes exhibited a high capacitance of 14.1 F/cm3, energy density of 1.78 mWh/cm3, and power density of 69.9 mW/cm3. Furthermore, the fabricated MSC device demonstrated excellent cycling stability of 88.2% after 10,000 GCD cycles and a high rate capability of 81.1% at a current density of 1.00 A/cm3. The fabrication process provides an effective means for producing high-performance MSCs for miniaturized electronic devices.

Thesis (S.M.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, February 2001.
Includes bibliographical references (p. 179-182).
by Karen Young-Waithe.
S.M.

La détection de signaux magnétiques faibles a suscité une attention considérable en raison de ses applications potentielles dans des domaines tels que la médecine et la nanotechnologie. Diverses méthodes ont été employées pour améliorer la détection de signaux faibles, notamment les dispositifs SQUID, les capteurs diamant et les résonateurs magnétoélectriques (ME). Le choix de la méthode dépend de facteurs tels que le contexte d'application, le coût et les exigences de sensibilité. Parmi ces méthodes, les résonateurs MEMS-ME ont retenu l'attention en raison de leur flexibilité de conception, de leur compacité et compatibilité avec les circuits intégrés. Dans ces résonateurs à microéchelle, l'interaction entre films magnétostrictifs et piézoélectriques permet d'obtenir des effets de contrainte à l'échelle-micrométrique, offrant ainsi une grande précision et une résolution spatiotemporelle élevée. Cette thèse explore le régime nonlinéaire du fonctionnement des résonateurs, caractérisé par des formes asymétriques, des bifurcations et des résonances nonlinéaires. Le régime nonlinéaire permettre des modes de fonctionnement analogiques, qui sont obtenus en balayant la fréquence d'excitation jusqu'au point de bifurcation. Malgré les défis liés au comportement nonmonotonique, le régime nonlinéaire se révèle être une méthode précieuse pour détecter les signaux faibles. La bistabilité, courante dans les résonateurs fonctionnant de manière nonlinéaire, n'est pas largement utilisée dans les configurations piézoélectriques. Cette thèse explore le potentiel du régime de bifurcation dans les résonateurs actionnés piézoélectriquement et présente dispositif de preuve-de-concept pour quantifier les changements du signal en mesurant la fréquence. Mathématiquement, les équations différentielles sont transformées en équations de Duffing normalisées à l'aide de la méthode de Galerkin, permettant ainsi aux comportements dynamiques de se manifester à travers les coefficients Duffing. Différents modèles ont été développés pour répondre à différentes conditions et hypothèses, révélant des liens entre les paramètres mécaniques. Combler l'écart entre les modèles basés sur l'amplitude des vibrations et les données d'impédance s'est avéré complexe mais réalisable. Grâce à des expériences et à l'affinement itératif du modèle, le modèle basé sur l'amplitude des vibrations a fourni des informations sur les réponses en fréquence, bien qu'il ne prédise pas directement l'ampleur et la phase de l'impédance. La recherche a reconnu les limitations liées à l'emplacement de l'axe neutre dans les films minces monocouches, suggérant de réévaluer les hypothèses, de tenir compte des effets multicouches et d'effectuer des simulations numériques pour obtenir des représentations plus précises. Le concept d'axe neutre relatif a été introduit, reconnaissant les écarts par rapport aux prédictions du modèle monocouche. Cette approche a été justifiée de manière transparente et alignée sur le comportement expérimental observé. Parallèlement, la fabrication de microcantilevers à base de PZT, composants essentiels du capteur résonant, a subi de multiples itérations pour relever les défis. Ces améliorations itératives ont abouti à un processus de fabrication plus robuste et fiable. En conclusion, cette étude a fait progresser la compréhension des résonateurs actionnés piézoélectriquement et de leur potentiel dans la détection de signaux faibles. Les améliorations itératives de la fabrication et les modèles mathématiques ont contribué au développement de dispositifs de détection multifonctionnels. Elle a mis en lumière l'interaction complexe entre la nonlinéarité et la résonance dans les systèmes de résonateurs, fournissant informations pour des recherches futures et des applications pratiques
The detection of weak magnetic field signals has gained significant attention for its potential applications in fields such as medicine, geophysics, and nanotechnology. Various methods, including Superconducting Quantum Interference Devices (SQUIDs), optically pumped magnetometers (diamond sensors), and magnetoelectric (ME) resonators, have been used to enhance the detection of these weak signals. The choice of detection method depends on factors such as application context, available resources, cost, and sensitivity requirements. Among these methods, MEMS ME resonator-based sensors have garnered attention due to their design flexibility, compactness, and compatibility with integrated circuits. In these microscale resonators, the interaction between magnetostrictive and piezoelectric thin films enables a strain-mediated effect at micro- and nano-scales, resulting in high precision and spatial-temporal resolution. The thesis delves into the nonlinear regime in resonator operation, characterized by nonlinearity in vibrational responses, including asymmetrical peak shapes, multivalued responses, bifurcations, and nonlinear resonances. The nonlinear regime, particularly bifurcation, promises enhanced sensing capabilities and analog operation modes by sweeping the excitation frequency. Despite challenges like noise-activated stochastic switching, the nonlinear regime is valuable for detecting weak signals. Bistability in resonators within the nonlinear regime, underutilized in piezoelectric configurations, is explored. A proof-of-concept device quantifies signal changes through jumping frequency. Mathematically, differential equations are transformed into normalized Duffing equations using Galerkin's method, enabling dynamic behaviors to manifest through coefficients. Distinct models accommodate various conditions and assumptions, revealing connections between mechanical parameters and normalized coefficients in linear and nonlinear regimes. Bridging the gap between vibrational amplitude-based models and impedance data is complex but achievable. Experiments and iterative model refinement provide insights into frequency responses. Limitations regarding the neutral axis in monolayer thin films are acknowledged, with suggestions to reevaluate assumptions, consider multilayer effects, and employ numerical simulations. A relative neutral axis concept is introduced, transparently justified, and aligned with observed experimental behavior. The nonlinear regime widens resonance peaks, enhancing sensitivity in magnetic field detection. Parameters like piezoelectric and dielectric coefficients influence the transition to the nonlinear regime. The research extends beyond ideal scenarios, requiring further investigation to replicate the bifurcation regime under different conditions. In parallel, the fabrication of PZT-based microcantilevers, vital components of the resonant sensor, underwent multiple iterations to address challenges. These iterative improvements resulted in a more robust and reliable fabrication process. In conclusion, this study advanced the understanding of piezoelectrically actuated resonators and their potential applications in weak signal detection. The iterative fabrication enhancements and mathematical models contributed to the development of multifunctional sensing devices. The research also emphasized the importance of bridging the gap between vibrational amplitude-based models and impedance data. Finally, it shed light on the intricate interplay of nonlinearity and resonance in resonator systems, providing insights for future investigations and practical applications

Intact whole cells may be the ultimate functional molecular-scale machines, and our ability to manipulate the genetic mechanisms that control these functions is relatively advanced when compared to our ability to control the synthesis and direct the assembly of man-made materials into systems of comparable complexity and functional density. Although engineered whole cells deployed in biosensor systems provide one of the practical successes of molecular-scale devices, these devices explore only a small portion of the full functionality of the cells. Individual or self-organized groups of cells exhibit extremely complex functionality that includes sensing, communication, navigation, cooperation, and even fabrication of synthetic nanoscopic materials. Adding this functionality to engineered systems provides motivation for deploying whole cells as components in microscale and nanoscale devices. In this chapter we focus on the device science of whole cell components in a way analogous to the device physics of semiconductor components. We consider engineering the information transport within and between cells, communication between cells and synthetic devices, the integration of cells into nanostructured and microstructured substrates to form highly functional systems, and modeling and simulation of information processing in cells. Even a casual examination of the information processing density of prokaryotic cells produces an appreciation for the advanced state of the cell’s capabilities. A bacterial cell such as Escherichia coli ( 2 μm2 cross-sectional area) with a 4.6 million basepair chromosome has the equivalent of a 9.2-megabit memory. This memory codes for as many as 4300 different polypeptides under the inducible control of several hundred different promoters. These polypeptides perform metabolic and regulatory functions that process the energy and information, respectively, made available to the cell. This complexity of functionality allows the cell to interact with, influence, and, to some degree, control its environment. Compare this to the silicon semiconductor situation as described in the International Technology Roadmap for Semiconductors (ITRS). ITRS predicts that by the year 2014, memory density will reach 24.5 Gbits/cm2, and logic transistor density will reach 664 M/cm2. Assuming four transistors per logic function, 2 μm2 of silicon could contain a 490-bit memory or approximately three simple logic gates.

In this paper, a unique implant containing Gentamicin sulfate with biocompatible poly-lactide powders was developed by using such 3D printing (3D printing) process. The implantable drug delivery system prototypes, which were constructed with matrix structure; double-layer structure and sandwich structure, were manufactured with different processing parameters. The cross-sectional morphology of the implant was characterized by three dimensional video microscopic system and environmental scanning electron microscope. The microscopic morphologies and the in vitro releasing experiments of the implants fabricated by both 3D printing technique and conventional technique were investigated to evaluate the performance of the implant devices. At about 60-day release of the implants in vitro, the drug concentration was measured and the profiles were made. The release behavior and the microstructure were subsequently compared between the samples prepared using the 3D printing technology and the conventional technology. The as-described 3D printing technology in this work allows for the design and fabrication of implants with a sophistically micro- and macro-architecture, and thus having unambiguous advantage over the conventional technology.

Hydrophobic surfaces with microscale roughness can be rendered ultrahydrophobic by the addition of sub-micron scale roughness. A simple yet highly effective concept of fabricating hierarchical structured surfaces using a single-step deep reactive ion etch process is proposed. Using this method the complexities generally associated with fabrication of two-tier roughness structures are eliminated. Experiments are conducted on two double-roughness surfaces with different surface roughness, achieved by varying the size of the microscale roughness features. The surfaces are characterized in terms of static contact angle and roll-off angle and compared with surfaces consisting of only single-tier microscale roughness. The robustness of the new hierarchical roughness surfaces is verified through droplet impingement tests. The hierarchical surfaces are more resistant to wetting than the single roughness surfaces and show higher coefficients of restitution for droplets bouncing off the surface. The droplet dynamics upon impingement are explored.

Abstract Recent advancements in additive manufacturing such as Direct Write Inkjet printing introduced novel tools that allow controlled and precise deposition of fluid in nano-liter volumes, enabling fabrication of multiscale structures with submillimeter dimensions. Applications include fabrication of flexible electronics, sensors, and assembly of Micro-Electro-Mechanical Systems (MEMS). Critical challenges remain in the control of fluid deposition parameters during Inkjet printing to meet specific dimensional footprints at the microscale necessary for the assembly process of microscale structures. In this paper we characterize an adhesive deposition printing process with a piezo-electric dispenser of nano-liter volumes. Applications include the controlled delivery of high viscosity Ultraviolet (UV) and thermal curable adhesives for the assembly of the MEMS structures. We applied the Taguchi Design of Experiment (DOE) method to determine an optimal set of process parameters required to minimize the size of adhesive printed features on a silicon substrate with good reliability and repeatability of the deposition process. Experimental results demonstrate repeatable deposition of UV adhesive features with 150 μm diameter on the silicon substrate. Based on the observed wettability effect of adhesive printed onto different substrates we propose a solution for further reduction of the deposit-substrate contact area for microassembly optimization.

Rapid creation of devices with microscale features is a vital step in the commercialization of a wide variety of technologies, such as microfluidics, fuel cells and self-healing materials. The current standard for creating many of these microstructured devices utilizes the inexpensive, flexible material poly-dimethylsiloxane (PDMS) to replicate microstructured molds. This process is inexpensive and fast for small batches of devices, but lacks scalability and the ability to produce large surface-area materials. The novel fabrication process presented in this paper uses a cylindrical mold with microscale surface patterns to cure liquid PDMS prepolymer into continuous microstructured films. Results show that this process can create continuous sheets of micropatterned devices at a rate of 3.94 in2/sec (100 mm2/sec), almost an order of magnitude faster than soft lithography, while still retaining submicron patterning accuracy.

Cold roll bonding (CRB), a fabrication process that proceeds at room temperature, has been widely used in fabricating large-scale sheet metal composites. In this study, the effect of reinforcement particle sizes, ranging from nanoscale to microscale, on the bond strength of cold roll bonded aluminum silicon carbide (Al-SiC) composites has been investigated. The bond strength was measured by the T-peel test. Scanning electron microscope was employed to study the bonding behavior at the interface of the laminate composites. Nanoparticles failed to increase the bond strength compared with the unreinforced Al sample. On the other hand, relatively large particles (tens of micrometers) increased the bond strength noticeably due to the mechanical interlocking introduced by the particles. For the largest particle (60 μm) used in this study, the bond strength was large enough to tear the Al1100 strip during the T-peel test.

Realistic random roughness of channel surfaces is known to affect the fluid flow behavior in microscale fluidic devices. This has relevance particularly for applications involving non-Newtonian fluids, such as biomedical lab-on-chip devices. In this study, a surface texturing process was developed and integrated into microfluidic channel fabrication. The process combines colloidal masking and Reactive Ion Etching (RIE) for generating random surfaces with desired roughness parameters on the micro/nanoscale. The surface texturing process was shown to be able to tailor the random surface roughness on quartz. A Large range of particle coverage (around 6% to 67%) was achieved using dip coating and drop casting methods using a polystyrene colloidal solution. A relation between the amplitude roughness, autocorrelation length, etch depth and particle coverage of the processed surface was built. Experimental results agreed reasonably well with model predictions. The processed substrate was further incorporated into microchannel fabrication. Final device with designed wall roughness was tested and proved a satisfying sealing performance.

Elastomer-based microfluidic devices, created by soft lithography methods, are emerging as valuable tools in a constantly expanding research field. As their complexity inevitably increases, robust design and fabrication methods become critical to ensure that all of the components are well-integrated and functional. Microfluidics offers the possibility of solving system integration issues for biochemistry, while minimizing the necessity for external control hardware. Many applications, such as enzymatic library screening in bacteria, are currently carried out as a series of multiple, labor-intensive steps. While the industrial approach to complexity has been to develop elaborate mechanical workstations, this technology comes at a price, requiring considerable expense, space and labor. For small laboratories or research institutions, this technology is simply out of reach. Devices consisting of addressable elastomeric microfluidic networks can dramatically simplify the screening process, providing an environment where reagents can be injected and compartmentalized into sub-nanoliter aliquots to create a platform for high-throughput, sensitive analysis of biological material.

The ability to create 3D ICs can significantly increase transistor packing density, reduce chip area and power dissipation leading to possibilities of large-scale on-chip integration of different systems. A promising process for this application is the microscale additive manufacturing (AM) of 3D interconnect structures and capability of writing 3D metal structures with feature sizes of approximately 1 μm on a variety of substrates. Current microscale AM techniques are limited in their capabilities to produce 3D conductive interconnect structures. This paper presents the design and development of a new micro AM technique — microscale selective laser sintering (μ-SLS) — which overcomes many of the limitations of other micro AM processes to achieve true micron sized, electrically conductive features on a variety of substrates. This paper will present preliminary results from set of sintering experiments on copper (Cu) nanoparticle (NP) ink using the continuous wave (CW) laser to be employed in the μ-SLS system which will be compared to Cu NP sintering results produced with other laser sources such as nanosecond (ns) & femtosecond (fs) lasers. This study is important to estimate the optimum working range of fluence/irradiance to be used in the μ-SLS setup depending upon the laser employed. In general, it provides an experimental estimate of the sintering fluence/irradiance range of Cu NPs depending upon the type of laser used and compares their sintering quality based on morphology of sintered spots.

Ratcheted structures with superhydrophobicity have potential to drive motion of liquid drops in microfluidic devices. We report development of a new process to integrate microscale pillars with varied periods of ratchets from sub-micrometer to 1.5 mm in SU-8. For the fabrication, an hierarchical mixed process of thermal imprint lithography and optical UV-lithography was employed. Use of Ni ratchets as stamps and a hydrophobic silane coating on the stamp surfaces significantly improved imprinting performance into SU-8. We have successfully demonstrated fabrication of ratcheted micropillars as well as submicrometer ratchets integrated into micropillars. In addition, we will discuss optimization of the SU-8 imprinting process and the air gap compensation for photolithography of ratcheted SU-8 layers, which are essential for the fabrication.

Superhydrophobic hierarchical structures can not only enhance stability against wetting transition but, if well designed, also produce a larger slip compared to single-scale microstructures. Selective, rather than unilateral, roughening of the microstructure surfaces is desirable to realize increased slip and to study the role of nanoscale roughening; our superhydrophobic hierarchical structures are microscale posts and grates whose top surfaces are kept smooth while sidewall surfaces are etched into nanostructures. To obtain such two-scale micro-nano structures, we have combined two recent microfabrication techniques — gold coating by galvanic displacement and gold-assisted porous etching of silicon. As a result, we have obtained a slip length as large as ∼400 μm on micro-nano structures, which is a ∼100% increase from the previous record of ∼200 μm obtained on micro-smooth structures. Preservation of the microscale geometric parameters was what differentiated our hierarchical samples from others, which showed enhanced stability but would not result in an increased slip. The paper presents the process details developed to fabricate the micro-nano hierarchical structures.