Single Fabrication Process Research Articles

Multiplexed All‐Optical Permutation Operations Using a Reconfigurable Diffractive Optical Network

AbstractLarge‐scale and high‐dimensional permutation operations are important for various applications in, for example, telecommunications and encryption. Here, all‐optical diffractive computing is used to execute a set of high‐dimensional permutation operations between an input and output field‐of‐view through layer rotations in a diffractive optical network. In this reconfigurable multiplexed design , every diffractive layer has four orientations: , , , and . Each unique combination of these layers represents a distinct rotation state, tailored for a specific permutation operation. Therefore, a K‐layer rotatable diffractive design can all‐optically perform up to independent permutation operations. The original input information can be decrypted by applying the specific inverse permutation matrix to output patterns. The feasibility of this reconfigurable multiplexed diffractive design is demonstrated by approximating 256 randomly selected permutation matrices using = 4 rotatable diffractive layers. To further enhance its multiplexing capability, input polarization diversity is also utilized. Additionally, this reconfigurable diffractive design is experimentally validated using terahertz radiation and 3D‐printed diffractive layers, providing a decent match to numerical results. The presented rotation‐multiplexed diffractive processor is particularly useful due to its mechanical reconfigurability, offering multifunctional representation through a single fabrication process.

Vapor Sublimation and Deposition Polymerization to Fabricate a Directional Scaffold for Guiding Tubular Dentin Regeneration

AbstractDental caries, or tooth decay, is a widespread problem and is generally considered irreversible, yet a regeneration solution exists to cure them. In this study, a multifunctional and biocompatible dental scaffold is fabricated by a unique vapor sublimation and deposition polymerization process with the well‐accepted material Parylene, resulting in the construction of a 3D and porous polymer scaffold that accommodates living cells and a combination of growth factor molecules in a single fabrication process, which differentiates the coating formation from a conventional vapor process. Physically, a directional interior structure is constructed to guide dental pulp stem cells (DPSCs) attachment and alignment. Biochemically, necessary growth factors, including Wnt‐3a and FGF‐2, are incorporated within the scaffold during fabrication to guide the cell differentiation of odontogenesis. The synergistic effects of the attachment and alignment of DPSCs, as well as the biocompatibility and odontogenic activities of the components accommodated in the scaffold, result in the upregulation of the cell differentiation into odontoblasts, as shown by the morphology of odontoblasts and the expressions of odontogenesis markers. Thus, the reported fabrication technique and its products represent an alternative approach for dentin regeneration in dental caries and tooth decay.

Weighted spin torque nano-oscillator system for neuromorphic computing

Neuromorphic computing is a promising strategy to overcome fundamental limitations, such as enormous power consumption, by massive parallel data processing, similar to the brain. Here we demonstrate a proof-of-principle implementation of the weighted spin torque nano-oscillator (WSTNO) as a programmable building block for the next-generation neuromorphic computing systems (NCS). The WSTNO is a spintronic circuit composed of two spintronic devices made of magnetic tunnel junctions (MTJs): non-volatile magnetic memories acting as synapses and non-linear spin torque nano-oscillator (STNO) acting as a neuron. The non-linear output based on the weighted sum of the inputs is demonstrated using three MTJs. The STNO shows an output power above 3 µW and frequencies of 240 MHz. Both MTJ types are fabricated from a multifunctional MTJ stack in a single fabrication process, which reduces the footprint, is compatible with monolithic integration on top of CMOS technology and paves ways to fabricate more complex neuromorphic computing systems.

Development of the multi-directional ablation process using the femtosecond laser to create a pattern on the lateral side of a 3D microstructure

Two-photon stereolithography (TPS) is widely used for the fabrication of various three–dimensional (3D) structures with sub-micron fabrication resolution in a single fabrication process. However, TPS is unsuitable for microstructures with fine-hole patterns. The laser ablation process can be easily drilled, or made holes in various materials. However, in the case of laser ablation, the focal plane of the laser is fixed, which is limited to the processing plane. In this study, a multidirectional ablation process is studied to apply laser ablation to various processing planes of a 3D microstructure fabricated by the TPS process. A 3D hybrid fabrication process with the advantages of both TPS and laser ablation is expected to improve the fabrication efficiency. The 3D hybrid process is proposed based on a single laser source. The microstructure is fabricated using TPS, and the multi-directional ablation process creates a hole in the lateral side of the 3D microstructure. To develop the multidirectional ablation process, the reflecting mirror system should be designed to adaptably rotate the laser focal plane and guide the laser path for the target process plane. Through various examples, we demonstrate the ability of the multi-directional ablation process with various examples.

A 3D printed liquid metal emulsion for low stress activated stretchable electronics

A strain-induced electrically conductive liquid metal emulsion for the programmable assembly of soft conductive composites is reported. This emulsion exhibits the shear yielding and shear thinning rheology required for direct ink writing. Examples of complex self-supported 3D printed structures with spanning features are presented to demonstrate the 3D printability of this emulsion. Stretchable liquid metal composites are fabricated by integrating this emulsion into a multi-material printing process with a 3D printable elastomer. The as-printed composites exhibit a low electrical conductivity but can be transformed into highly conductive composites by a single axial strain at low stresses ([Formula: see text] 0.3 MPa), an order of magnitude lower than other mechanical sintering approaches. The effects of axial strain and cyclic loading on the electrical conductivities of these composites are characterized. The electrical conductivity increases with activation strain, with a maximum observed relaxed conductivity of 8.61 × 105 S⋅m−1, more than 300% higher than other mechanical sintering approaches. The electrical conductivity of these composites reaches a steady state for each strain after one cycle, remaining stable with low variation ([Formula: see text] standard deviation) over 1000 cycles. The strain sensitivities of these composites are quantitatively analyzed. All samples exhibit strain sensitivities that are lower than a bulk conductor throughout all strains. The printed composites showed low hysteresis at high strains, and high hysteresis at low strains, which may be influenced by the emulsion internal structure. The utility of these composites is shown by employing them as wiring into a single fabrication process for a stretchable array of LEDs.

Intellectual Data Aggregation Using Independent Cluster based Medicaid Method for Network Functionality Fabrication

Objectives: Network functionality-based tracking is difficult for the fabrication processing under the various environment condition. In order to achieve the efficient result Intellectual data cluster-based Medicaid aggregation method applied for the network functionality analysis of the attack on network entities aggregate the fabrication process for balancing the network to normal flow. Methods: The proposed Independent Cluster based Medicaid Intellectual Data Aggregation (ICAMA) is compared with the K-means and GSVM, DBSCAN algorithm for classification of the attack entities to understand the response and reinforcement of the network functionality against the interconnection nodes by using energy and weighted aggregation, accuracy metrics on the CIC-IDS 2019 dataset. Findings: The Experiment studies provide the 15.23% lower energy consumption for interconnection of nodes comparing with the DBSCAN and 17.18% against the K-means algorithms. The network functional fabrication progress of proposed method has the weighted aggregation15.07%,8.32%, 6.41%, 5.12%, 5.52%, 8.08% and 2.21% against the given K-means, DBSCAN, GSVM, SOM, PCA, ocSVM and ICA methods and also improves accuracy to 11.07% compared with the GSVM method. ICAMA applies the intellectual functionality based on the distribution of entities in the network as a cluster or a single fabrication process. Novelty: In order to restore the regular network progress, ICAMA continuously runs the dynamic collection of network analysis by employing intellectual functional support to identify various types of network anomalies. Keywords: Clustering; Data aggregation; Energy consumption; Fabrication; Network attacks

Single-process 3D-printed stacked dielectric actuator

Single-process additive manufacturing provides fully functional 3D-printed structures in a single 3D printer without the need for additional manufacturing processes. The 3D-printed parts can be scaled, individualized, embedded, and combined into multi-functional structures without modifications to the fabrication technology.This manuscript reports the first demonstration of monolithically 3D-printed stacked dielectric actuators (SDEAs) in a single fabrication process utilizing a commercially accessible extrusion 3D printer and thermoplastic filaments. Neither single-layer nor stacked dielectric actuators have been 3D printed with thermoplastic filament extrusion in a single process until now.To achieve single-process fabrication, this research successfully addresses the main challenges: single-process fabrication of the dielectric layer and electrodes, repeatability and reliability of the 3D-printed thin dielectric layer, and layer stacking.Four actuators with different active areas and a number of stacked active layers were 3D printed. The functionality of the 3D-printed actuators was demonstrated with dynamic electromechanical characterization in a free-displacement and blocked-force configuration in a broad frequency range (up to 5 kHz).The actuators show promise for applications that require high-frequency resonators or high controllability in the sub-resonance region.

Novel fabrication of soft microactuators with morphological computing using soft lithography

A simple and cost-effective method for the patterning and fabrication of soft polymer microactuators integrated with morphological computation is presented. The microactuators combine conducting polymers to provide the actuation, with spatially designed structures for a morphologically controlled, user-defined actuation. Soft lithography is employed to pattern and fabricate polydimethylsiloxane layers with geometrical pattern, for use as a construction element in the microactuators. These microactuators could obtain multiple bending motions from a single fabrication process depending on the morphological pattern defined in the final step. Instead of fabricating via conventional photolithography route, which involves multiple steps with different chromium photomasks, this new method uses only one single design template to produce geometrically patterned layers, which are then specifically cut to obtain multiple device designs. The desired design of the actuator is decided in the final step of fabrication. The resulting microactuators generate motions such as a spiral, screw, and tube, using a single design template.

Improved Performance and Fabrication of Interlayer for Advanced Lithium-Sulfur Batteries

In the search for next-generation energy-storage materials, the lithium-sulfur battery has drawn much attention due to its immensely high theoretical specific capacity of 1675 mAh g-1 and energy density of 2600 Wh kg-1. Its added benefit of being a low-cost, copiously available, and environmentally benign material has also prioritized the Li-S battery as an auspicious candidate. Despite such auspiciousness, the lithium-sulfur battery has inherent disadvantages that hinder its commercialization: (i) elemental sulfur and Li2S suffer from poor electrical conductivity which makes the use of high-sulfur content electrodes challenging and (ii) polysulfide migration to and reverse reaction at the negative electrode during the charge/discharge process, known as shuttle effect, result in a loss of active material and degeneration of capacity and Coulombic efficiency. A plethora of efforts has been made to resolve these issues. A traditional approach taken by researchers is the use of sulfur mixed with, confined by, and impregnated in all kinds of carbons to augment conductivity. However, polysulfide migration still occurs and cycle life is inadequate for practical applications. Previous papers introduced the use of carbon-paper interlayers in between the sulfur cathode and the polymer separator or carbon-coated membrane and demonstrated high sulfur utilization with better cycle life due to the suppression of polysulfide diffusion to the anode and the serving of the carbon-paper interlayer as a pseudo-upper current collector.We present here the fabrication of an interlayer consisting of MWCNT and the electrolyte in a single fabrication process. Such MWCNT-electrolyte-paper interlayers are much more effective compared to the bare MWCNT-paper interlayer due to the fast ionic and electronic transport and a better interface between the sulfur cathode and the interlayer as well as between the separator and the interlayer.

Self-Assembled MWCNT Interlayer for High-Performance Lithium-Sulfur Batteries

Rechargeable batteries are one of the prime approaches for electrical energy storage. The current lithium-ion battery technology based on transition-metal oxide cathodes and graphite anode have limited energy storage capacity, so there is immense interest to develop alternate high-capacity cathode and anode materials. Lithium-sulfur (Li-S) batteries are appealing in this regard as they offer a high energy density of 2500 Wh kg-1 when coupled with lithium-metal anode due to the large charge-storage capacity of sulfur.[1] Moreover, sulfur is much more abundant, inexpensive, and non-toxic compared to the transition-metal oxide cathodes. There are several challenges with the Li-S batteries, such as low electrical conductivity of sulfur and the discharge product Li2S and the migration of dissolved polysulfides from the cathode to the anode, resulting in low efficiency and inadequate cycle life.[2] Well-designed carbon-sulfur composites have been extensively explored to overcome these issues.[3] In these strategies, sulfur was entrapped in carbon structures using porous carbon, carbon nanotubes (CNT), and hollow carbon spheres. Carbon backbone serves as the electron conducting path for sulfur and reduce polysulfide migration by trapping the polysulfides during cycling. However, polysulfide migration still occurs and cycle life is inadequate for practical applications. Manthiram group and other groups introduced the use of carbon-paper interlayers in between the sulfur cathode and the polymer separator or carbon-coated membrane and demonstrated high sulfur utilization with better cycle life due to the suppression of polysulfide diffusion to the anode and the serving of the carbon-paper interlayer as a pseudo-upper current collector.[4] We present here the fabrication of an interlayer consisting of MWCNT and the electrolyte in a single fabrication process. Such MWCNT-electrolyte-paper interlayers are much more effective compared to the bare MWCNT-paper interlayer due to the fast ionic and electronic transport and a better interface between the sulfur cathode and the interlayer as well as between the separator and the interlayer.

Novel H⁺-Ion Sensor Based on a Gated Lateral BJT Pair.

An H+-ion sensor based on a gated lateral bipolar junction transistor (BJT) pair that can operate without the classical reference electrode is proposed. The device is a special type of ion-sensitive field-effect transistor (ISFET). Classical ISFETs have the advantage of miniaturization, but they are difficult to fabricate by a single fabrication process because of the bulky and brittle reference electrode materials. Moreover, the reference electrodes need to be separated from the sensor device in some cases. The proposed device is composed of two gated lateral BJT components, one of which had a silicide layer while the other was without the layer. The two components were operated under the metal-oxide semiconductor field-effect transistor (MOSFET)-BJT hybrid mode, which can be controlled by emitter voltage and base current. Buffer solutions with different pH values were used as the sensing targets to verify the characteristics of the proposed device. Owing to their different sensitivities, both components could simultaneously detect the H+-ion concentration and function as a reference to each other. Per the experimental results, the sensitivity of the proposed device was found to be approximately 0.175 μA/pH. This experiment demonstrates enormous potential to lower the cost of the ISFET-based sensor technology.

Factors influencing variations in the thermal conductivity of polycrystalline ZnS and Cr2+:ZnS

The thermal conductivities of polycrystalline ZnS grown by chemical vapor deposition (CVD), hot pressing, and CVD with hot isostatic press post-processing were measured. Results showed that the grain boundary is the key factor influencing the thermal conductivity of polycrystalline ZnS. The thermal conductivities of Cr2+:ZnS obtained through a single fabrication process but with different doping concentrations were measured. Findings revealed that the doping process, temperature, and doping concentration are the main factors contributing to variations in the thermal conductivity of Cr2+:ZnS.

Recent advancements and vision toward stretchable bio-inspired networks for intelligent structures

Significant progress has recently been achieved in structural health monitoring, maturing the technology through quantification, validation, and verification to promote implementation and fielding of SHM. In addition, there is ongoing work seeking to detect damage precursors and to deploy structural health monitoring systems over large areas, moving the technology beyond hot-spot monitoring to global state sensing for full structural coverage. A large number of small sensors of multiple types are necessary in order to accomplish the goals of structural health monitoring, enabling increased sensing capabilities while reducing parasitic effects on host structures. Conventional sensors are large and heavy, adding to the weight of a structure and requiring physical accommodation without adding to and potentially degrading the strength of the overall structure. Increased numbers of sensors must also be deployed to span large areas while maintaining or increasing sensing resolution and capabilities. Traditionally, these sensors are assembled, wired, and installed individually, by hand, making mass deployment prohibitively time consuming and expensive. In order to overcome these limitations, the Structures and Composites Lab at Stanford University has worked to develop bio-inspired microfabricated stretchable sensor networks. Adopting the techniques of complementary metal-oxide semiconductor and microelectromechanical system fabrication, new methods are being developed to create integrated networks of large numbers of various micro-scale sensors, processors, switches, and all wiring in a single fabrication process. Then the networks are stretched to span areas orders of magnitude larger than the original fabrication area and deployed onto host structures. The small-scale components enable interlaminar installation in laminar composites or adhesive layers of built-up structures while simultaneously minimizing parasitic effects on the host structure. Additionally, data processing and interpretation capabilities could be embedded into the network before material integration to make the material truly multifunctional and intelligent once fully deployed. This article reviews the current accomplishments and future vision for these systems in the pursuit of state sensing and intelligent materials for self-diagnostics and health monitoring.

Origami and Tessellation in Design

For centuries, origami artists have invested immeasurable effort developing models under extreme self-imposed constraints (e.g., only paper, no cutting or gluing, one regular-shaped sheet). The accessible and formable medium of paper has enabled swift prototyping of vast numbers of possible designs. This effort has resulted in stunning origami structures and mechanisms created in a simple medium with only a single fabrication process (folding). Origami artists' methods and perspectives have created systems that have not previously been conceived using traditional engineering methods. Using origami-inspired methods, it may be possible to design origami-like systems but using different materials and processes to meet emerging product requirements. Origami-inspired systems have the potential to meet needs that are presently unfulfilled because the design of such systems was previously too difficult or they were not yet envisioned.Origami tessellations also show promise for impact in engineering design. There are theoretical, computational, and artistic challenges associated with many aspects of design that take advantage of symmetry of patterns and ability to fold complex shapes. While various approaches exist, it is important to bring together good examples of practical design and the thought process of the designers who created folding and/or tiled/patterned based products with theoretical approaches so as to catalyze new ideas in engineering design.As the research and design community has begun to realize the potential impact that origami and tessellation principles may have on engineering design, there has been an increased interest in better understanding possible connections. This interest is likely to accelerate due to the support of funding agencies, including the U.S. Air Force Office of Scientific Research (AFOSR) and the National Science Foundation's Emerging Frontiers in Research and Innovation (EFRI) program with its “Origami Design for Integration of Self-assembling Systems for Engineering Innovation (ODISSEI)” research topic area. It is refreshing to see how art can be so inspiring to engineering and science disciplines, and we hope that this is just the beginning of greater understanding and collaboration between the artistic, engineering, manufacturing, and scientific communities. Art may indeed be the critical catalyst needed to ignite a passion for engineering and science in our youth and thus be a key to the future of STEM (science, technology, engineering, and mathematics).This special issue of the Journal of Mechanical Design was created as an early venue for work in this emerging research area. Topics in this issue are intentionally varied, and include the following:We thank all of the authors who have submitted their work for publication in this special issue. We are also grateful to the many reviewers that provided their time and expertise in providing valuable peer review. Special thanks also go to Shapour Azarm and Panos Papalambros, current and past editors of the Journal of Mechanical Design, who had the foresight to support a special issue in this emerging research area, to Amy Suski for her administrative support to make the issue possible and to the ASME staff for production of the issue.

Free Form Fluidics

This article introduces the concept of blending fluid power with mechanical structure through addictive manufacturing. Today, fluid-powered devices are manufactured using conventional fabrication practices. The additive process enables integrated structure, actuation, fluid passages, thermal management, and control within a single fabrication process. Fluid can be routed efficiently through the structure without the need for cross-drilled holes or plugs. Fluid passages can be optimized for heat dissipation and minimized head loss. One of the primary issues regarding parts manufactured using the additive manufacturing process is their mechanical properties. Results show that components made with Ti-6-4 powders have a minimum yield stress and ultimate strength that exceeds Grade 5 specifications. The Arcan system uses a powder bed that has an elevated temperature. Therefore, the part exhibits very little residual stress during the manufacturing process. This leads to improved mechanical strength but induces challenges in powder removal. The specific advantages are reduced weight, potential for lower cost, and reduced part counts.

INTEGRATION OF N- AND P-CONTACTS TO GaN-BASED LIGHT EMITTING DIODES

Low-resistance Ohmic contacts are essential for the fabrication of electrical devices. While low contact resistance has been achieved to p -type layers or n -type layers separately, contacts are likely to degrade when both types need to be integrated into a single fabrication process, in particular when prior mesa etching is required. We present a solution to the problem, resulting in low-resistance Ohmic contacts on n -type GaN layers without post-deposition thermal anneal, while maintaining the quality of typical p -type contacts. We implement an integrated process for both, n - and p -contacts, involving an oxygen pretreatment to fabricate light emitting diodes with lower series resistance in the contacts and lower voltage drop at high current when compared to separately optimized contacts.

Bubble inclusion and removal using PDMS membrane-based gas permeation for applications in pumping, valving and mixing in microfluidic devices

Several advancements in fluid handling applications of a gas-permeable polydimethylsiloxane (PDMS) membrane are demonstrated. Devices for controlled pumping, bubble injection, bubble removal and mixing are demonstrated using a three-layered fabrication method. The ability of a gas-permeable membrane to control flow in glass channels is determined. Consistent flow rates ranging from approximately 1 to 14 µl min−1 were observed using control pressures from 100 to 700 mbar. Bubble injection and removal from microfluidic channels was performed in monolithic PDMS devices using several bubble trap geometries at fluid flow rates over 100 µl min−1. The rate of removal of the air in the bubble trap was determined as a function of the area of membrane exposed and the applied vacuum. The PDMS membrane was shown to be an effective tool for the injection and removal of air bubbles in a method of enhancing mixing using bubbles and branched microchannels. The amount of mixing was optically determined before and after bubbles entered the fluid channel. The ability to produce all of these compatible components using a single fabrication process is a step toward inexpensive, parallel, highly integrated microfluidic systems with minimal external controls.

All‐Solid‐State Reference Electrodes with Poly(n‐butyl acrylate) Based Membranes

AbstractA new kind of all‐solid‐state reference electrode, suitable for potentiometry with ion‐selective electrodes is proposed, where a poly(n‐butyl acrylate) based membrane is coated on a glassy carbon support with conducting polymer–polypyrrole ion‐to‐electron transducing layer. These electrodes are compatible with poly(acrylate) based ion‐selective electrodes in simple disposable cells, where both indicator and reference electrode can be produced in a single fabrication process, using the same or similar methods. The composition of the membrane with lipophilic salt and Ag/AgCl system was tuned to expose nonselectivity and to obtain a stable potential, independent of solution composition. Near‐zero slopes of potentiometric characteristics were recorded in typical electrolyte solutions in the concentration range: 1 to 10−5 M, stable potentials and only slight influence of interferents: oxygen, redox reactants, H+/OH− ions and surfactants make this arrangement promising for practical applications, particularly when matched against a similar ion‐selective electrode. Tests of cells with poly(n‐butyl acrylate) based membrane potassium selective sensors and reference electrodes confirmed their analytical applicability.

The Two-Bit NROM Reliability

Saifun NROM/spl trade/ is a novel localized charge-trapping-based nonvolatile memory technology that employs inherent two-bits-per-cell operation. NROM technology is able to provide code flash, data flash, embedded flash, and true EEPROM functionality with a single fabrication process and minor architectural adjustments. Reliability topics of NROM technology are discussed, focusing on the ability to achieve 10-year data retention after 10/sup 5/ program and erase cycles. The accumulated knowledge of NROM physics allows this technology to successfully compete with the industry standard floating-gate memory technology and to gain the acceptance of the memory market.

Optical properties of Li + doped electrochromic WO 3 thin films

As component parts of electrochromic devices, WO 3 layers are understood to be chiefly responsible for the colour change of the former when cationic ions are inserted into their crystalline lattice. In seeking to develop a suitable all-solid electrochromic device, the light ions have to be inserted into the structure in one step of a single fabrication process (a one-run process). In this paper, Li + ions were incorporated into the WO 3 layer from the gas phase during the deposition process. Electrochromic WO 3 thin films were deposited on fused silica and silicon substrates by physical vapour deposition techniques. The substrate temperature during the WO 3 deposition process was kept at 150°C and the oxygen pressure at 5×10 –2Pa. In order to improve the performance of this one-run doping method, a series of samples, with Li to W atomic ratio 0 (as-deposited) and 0.4, was prepared to study the effect of Li insertion on the optical properties of the WO 3 thin films. Optical characterisation in the ultra violet–visible and infrared ranges was carried out using ultra violet–visible transmittance, ultra violet–visible multichannel spectroscopic ellipsometry and FTIR spectroscopy. The optical properties were clearly dependent on the level of Li. The evolution of the optical properties in a sample, with a Li–W ratio of 0.4, was also analysed after exposure to atmosphere. These results represent an initial step towards achieving a better understanding of problems related to the doping of electrochromic layers with lithium ions, including irreversibility, stoichiometry effects, the correlation between optical and electrical properties and optical absorption modelling.