Proposed Manufacturing Process Research Articles

Monolithic full-color micro-LED displays featuring three-dimensional chip bonding and quantum dot-based color conversion layer

What we believe to be a novel fabrication process for monolithic full-color (RGB) micro-LED (µLED) display technology, featuring three-dimensional (3D) and quantum dot (QD)-based color conversion layer, has been proposed. This method offers advantages such as a wide color gamut, high pixel density, high yield, and low cost. A 16 × 16 passive matrix (PM) RGB µLED array, with a pitch size of 80 µm and a pixel density of 328 pixels per inch (PPI), has been successfully realized using flip-chip bonding technology. When measuring the electroluminescence (EL) spectra of the green and red pixels with the addition of color filters, the color gamut can achieve a maximum of 124% of the National Television System Committee (NTSC) standard. Additionally, this process significantly reduces the risk of damage to the QD film during photolithography compared to using two different colored QDs for RGB µLED arrays. The proposed manufacturing process shows considerable promise for commercialization.

Closed-loop control of a 3D printed soft actuator with integrated flex sensors and SMA wires

This article presents a soft SMA-driven actuator capable of achieving desired bending angles. To create the actuator, flex sensors and Shape memory alloy (SMA) wires were embedded into the thermoplastic polyurethane (TPU) matrix of the sample during the 3D printing process. By deactivating and activating the two SMA wires according to sensing signals from the flex sensors, the actuator sample can track the input bending angle. This approach enabled closed-loop control and improved the overall efficiency of the system. Additionally, the proposed manufacturing process provides a simple and cost-effective solution for the rapid prototyping and custom design of smart materials with complex structures and high resolutions.

Holistic Enlightening of Blackspots With Passive Tailorable Reflecting Surfaces for Efficient Urban mmWave Networks

Mitigating outage regions is of particular interest for emerging millimeter-wave (mmWave) and future sub-terahertz frequency cellular networks. Whereas smart radio environments based on metasurfaces constitute a key concept for 6G research, current networks cannot be served as new control procedures are required. Although small prototypes are already emerging, costs will be higher for the dense deployment of reconfigurable intelligent surfaces (RISs) than for passive reflectors. It is argued that passive reflectors can be used to effectively, cost-efficiently, and permanently boost connectivity in well-defined service areas. Leveraging the advantages of 3D printing and spray-painted conductive varnish, we introduce the Holistic Enlightening of bLackspots with passIve reflectOr moduleS (HELIOS) approach which is characterized by its scalability and parametrizability to meet the reflection requirements derived from sophisticated network planning. These slim reflectors meet the core criteria of ease of installation and minimal visual impact on the cityscape, which are imperative for market success. Our measurements-based comparison of prototypes against typical metal/aluminum reflectors shows at least equal reflectivity at a higher practicality of the proposed manufacturing process. The conducted simulation study validates the modular reflector pattern design process and finds a trade-off between the reflector efficiency and the minimum protrusion depth, which relates to the number of modules in the designated mounting area. An urban ray-tracing simulation-based case study further underlines the high applicability of the proposed approach, with the growth of the beyond line-of-sight (LOS) connectivity region being nearly twice as large for a site-tailored HELIOS configuration as for a simple reflector plate.

Defocus digital light processing stereolithography for rapid manufacture of microlens arrays

This study applied defocusing to digital light processing (DLP) stereolithography for the fabrication of microlens arrays (MLAs) within 1 s. We studied the effects of exposure energy, defocus distance, and a diameter adjustment algorithm to ensure printed MLAs with designed dimensions. Experiment results demonstrate that our simple fabrication method is applicable to the manufacture of various MLA designs, while achieving nanoscale surface roughness and good image quality. We determined that the height of the MLAs is proportional to the exposure energy. The highest height-to-diameter ratio achieved in this study was 0.63 (diameter = 200 µm; height = 126 µm). Our use of defocusing significantly reduced the average surface roughness (Ra) of the printed MLAs to 129 nm with a corresponding improvement in image resolution 45.3 lp/mm. Our use of a diameter adjustment algorithm in designing the digital mask helped preserve the dimensionality of the printed MLAs. The proposed manufacturing process was used to create a variety of MLAs with numerical apertures as high as 0.980, multiple focal lengths on a single substrate (from 21 µm to 199 µm), and fill factors as high as 77.98 %.

High-temperature thermal storage-based cement manufacturing for decarbonization

Cost-effective CO2 capture is essential for decarbonized cement production since it is one of the largest CO2 emission sources, where 60% of direct emissions are from CaCO3 decomposition and 40% are from fuel combustion. This work presents a low-carbon cement manufacturing process by integrating it with renewable energy for electric heating and thermal storage to replace the burning of fossil fuels in the conventional calciner. The low-carbon renewable energy reduces the indirect CO2 emissions from electricity consumption. The high-temperature CO2 is employed as the heat transfer fluid between the energy storage system and the calciner. In the proposed basic manufacturing process, the CO2 from the CaCO3 decomposition can be directly collected without energy-consuming separation since no impurities are introduced. Furthermore, the remaining CO2 from fuel combustion in the kiln can be captured through monoethanolamine (MEA) absorption using waste heat. In the two situations, the overall CO2 emissions can be reduced by 69.7% and 83.1%, respectively, including the indirect emissions of electricity consumption. The economic performance of different energy storage materials is investigated for materials selection. The proposed manufacturing process with a few high-temperature energy storage materials (BaCO3/BaO, SrCO3/SrO, Si, etc.) offers a higher CO2 emission reduction and lower cost than alternative carbon capture routes, i.e., oxyfuel. The cost of CO2 avoided as low as 39.27 $/t can be achieved by thermochemical energy storage with BaCO3/BaO at 1300 °C, which is superior to all alternative technologies evaluated in recent studies.

A new method for manufacturing dry electrodes on textiles. Validation for wearable ECG monitoring

This paper presents a new dry ECG electrode printed on a textile substrate. The proposed manufacturing process permits cost-effective mass production. The ECG dry electrode is obtained through screen printing a conductive silver ink coated with a biocompatible carbon layer. Three different designs combining two shapes (circular and square) and two sizes were developed. The resulting measured impedances are similar to those obtained via a conventional electrode. The prototypes were attached to a bracelet and used with a commercial electrocardiogram (ECG) device to register ECG signals. The dry electrodes were validated via ECG monitoring and compared with a conventional wet electrode. The clinical interest intervals reported similar results and the QRS morphology presented slight differences. Noise evaluation showed no notable differences for all the analyzed parameters.

Fabrication and characterization of ultra-thin vapour chambers with printed copper powder wick

With the increasing heat flux required in portable electronic devices, ultra-thin vapour chambers (UTVCs) have attracted increasing attention as efficient phase-change heat-transfer components. In this work, a sintered copper powder wick fabricated through a screen-printing process is proposed, providing a novel method for manufacturing large-area and complex-shaped UTVCs. UTVCs with a thickness of 0.55-mm and printed copper powder wicks were fabricated, and the copper powder paste preparation and UTVC manufacturing processes are described in detail. The copper powder paste was made by mixing dipropylene glycol monomethyl ether and copper powder with a particle size of 65–75 μm in a 5:1 ratio. The thickness of the copper layer after sintering was 0.2 mm and its porosity was 59.7%. The heat transfer performance of UTVCs under different liquid-filling ratios and test states was investigated. The results showed that the optimal liquid-filling ratio of the presented UTVCs is 43.2% and that its maximum heat-transfer capability is 6.5 W with a thermal resistance of 0.46 °C/W in the horizontal state. The thermal resistance of the UTVC in the anti-gravity state is more than twice that of the UTVC in the horizontal state. The proposed manufacturing process provides a new solution for the research of the thinner VC and the patterned wick structures.

Novel sustainable metallic powder production process with water used as milling medium.

Today, Fe–Al intermetallic compounds are receiving a great interest from the mechanical, aerospace, and biomedical industries. A novel production process for Fe–Al intermetallic powders based on the generation of metallic tapes by rapid solidification and disintegration by water vapor was proposed. In this research work, a comparison is made between the energy required to manufacture of Fe–Al powder using the aforementioned process and one of the most commonly used manufacturing processes within the industry such as mechanical alloying. In addition, some other benefits of the proposed manufacturing process are analyzed. To carry out this comparison, the theoretical equations that take into account the most important variables involved during the process such as the type of material and hardness, the initial and final particle size, the grinding stages and the heating of the treatment powder were considered. In the case of calculating the energy required for the new proposed process, the two main stages were considered such as (1) the production of FeAl metal tape and (2) the subsequent transformation of the tape into powder by means of injection water vapor. For the first stage, the CASTRIP process is considered, and for the second stage, the energy required for the generation steam. Although the calculations may have certain limitations, it is obvious that the energy required to Fe–Al powder production using the new process is much lower than that required by mechanical alloying, resulting in at least three orders of magnitude lower (2.75 × 106 versus 2.206 × 109 kJ/ton). This lower energy implies considerable economic savings in the production process. On the other hand, when using water as a grinding medium during the process, it results in less environmental and acoustic pollution, less manipulation risks for humans and finally, no harmful agents or additives are used, making the proposed process sustainable.Graphic abstract

Effect of Synthesis Procedure on Particle Dispersion and Hardness of Al- Sic Functionally Graded Metal Matrix Composite

Abstract Fabrication of Functionally Graded Metal Matrix Composites (FGMMC) especially with high ceramic reinforcement's volume fraction is highly challenging. Depending on the processing technique and process parameters various defects may arise. This research aims to find the best procedure to make FGMMCs with the highest quality and minimum cost. A new method is proposed that incorporates lost-foam and melt infiltration with semicentrifugal casting to produce FGMMC. Experiments were performed to in-situ fabricate 6061-Aluminum alloy reinforced with gradient distributed Silicon carbide particles (Al/SiC FGMMC). Effect of SiC %, Al pouring temperature and rotational speed on the fabricated specimens hardness and reinforcement gradient were investigated using design of experiments and regression analysis. Results reveal the optimum procedure and process settings based on desired properties/gradient required. Mathematical model formulated captures the effect of these process parameters on process cost, and cost of poor quality. Improper selection of those parameters may lead to extensive losses due cost of poor quality which is 12 times higher than the material cost. The proposed manufacturing process proved satisfactory in ensuring proper dispersion. A desirability function can by used to determine the process parameters and volume fraction that minimizes the defects and gives superior properties for a specific application.

A Novel Trench-Based Triple Gate Transistor With Enhanced Driving Capability

This letter addresses the design, implementation, and characterization of a novel high-density Triple Gate Transistor in a 40 nm embedded Non-Volatile Memory technology. Deep trenches are used to integrate two vertical transistors connected in parallel with the main planar transistor. Thanks to the built-in trenches, the proposed manufacturing process increases the transistor width without impacting its footprint. The voltage/current characteristics of a planar MOS structure are compared with the features of the new Triple Gate Transistor. The new architecture provides an improved driving capability, with an on-state drain current twice as high as its equivalent standard MOS, combined with a lower threshold voltage, suitable for low-voltage applications. Finally, the gate oxide and junction reliability are validated over the operating voltage range.

Design, manufacture, and characterization of a novel Ti-based nanocrystalline alloy

A novel titanium-based alloy with low density, high hardness, and corrosion resistance was manufactured and characterized in this paper. The Ti60Ni9Fe8Co8Si15 alloy was created from its elemental components and subjected to further manufacturing. To reach a homogeneous phase, the samples were broken into small pieces and were repeatedly re-melted with arc-melting. This base alloy was further processed to manufacture an amorphous/nanocrystalline material by ball milling followed by high-pressure torsion (HPT). For subsequent characterization, X-ray diffraction (XRD), pycnometer densitometry, scanning electron microscopy (SEM) with X-ray energy dispersive spectroscopy (EDS), and hardness measurements were performed. X-ray diffractometry confirmed the formation of a amorphous/nanocrystalline structure, as most of the characteristic peaks related to the crystalline phase disappeared or flattened after ball milling. In accordance, the hardness of the manufactured samples increased by nearly 50 HV compared to the base alloy. The density of the final alloy was measured to be 4.125 g/cm3, with a hardness of 762 ± 39 HV, which confirms that an exceptionally light and, at the same time, hard material was manufactured. In order to distinguish the effects of elemental composition and manufacturing on the measured properties of our alloy, a similar Ti-based alloy with a different elemental composition (Ti47Cu40Zr7.5Fe2.5Sn2Si1) was also prepared with the same proposed manufacturing process. This reference composition resulted in significantly lower hardness (489 ± 31 HV) at a significantly higher density (5.767 g/cm3).

Direct-Write Spray Coating of a Full-Duplex Antenna for E-Textile Applications.

Recent advancements in printing technologies have greatly improved the fabrication efficiency of flexible and wearable electronics. Electronic textiles (E-textiles) garner particular interest because of their innate and desirable properties (i.e., conformability, breathability, fabric hand), which make them the ideal platform for creating wireless body area networks (WBANs) for wearable healthcare applications. However, current WBANs are limited in use due to a lack of flexible antennas that can provide effective wireless communication and data transfer. In this work, we detail a novel fabrication process for flexible textile-based multifunctional antennas with enhanced dielectric properties. Our fabrication process relies on direct-write printing of a dielectric ink consisting of ultraviolet (UV)-curable acrylates and urethane as well as 4 wt.% 200 nm barium titanate (BT) nanoparticles to enhance the dielectric properties of the naturally porous textile architecture. By controlling the spray-coating process parameters of BT dielectric ink on knit fabrics, the dielectric constant is enhanced from 1.43 to 1.61, while preserving the flexibility and air permeability of the fabric. The novel combination textile substrate shows great flexibility, as only 2 N is required for a 30 mm deformation. The final textile antenna is multifunctional in the sense that it is capable of operating in a full-duplex mode while presenting a relatively high gain of 9.12 dB at 2.3 GHz and a bandwidth of 79 MHz (2.260–2.339 GHz) for each port. Our proposed manufacturing process shows the potential to simplify the assembly of traditionally complex E-textile systems.

Gel electrolyte for a 4V flexible aqueous lithium-ion battery

A system of electrolytes using water as a solvent was successfully used to support a typical lithium-ion battery chemistry that operates at 3.7V–4.2 V using standard ultraviolet-cured acrylic-based polymers as hydrophobic barriers. The aqueous electrolyte is contained in a system of poly(ethylene glycol) acrylate polymers crosslinked to produce an electrolyte gel that has electrochemical properties similar to that of the liquid phase component. The electrolyte gels have elastic moduli in the kPa range, making them soft enough to tolerant flexing, cutting, and blunt force impacts while keeping the electrodes covered and safe from shorting. While batteries based on water-in-salt electrolyte provides intrinsic safety that is otherwise unavailable from typical non-aqueous electrolytes, acrylate-based aqueous gel electrolytes offer the potential of large-scale manufacturing owing to the relatively low volatility of the electrolyte components and the low complexity of the proposed manufacturing process.

FE Simulation of the residual stress reduction in industrial-sized T-section component during a newly proposed manufacturing process

This paper focused on FE simulations of the residual stress distributions and evolutions during a newly established manufacturing process (i.e. Solution heat treatment, Cold rolling and Constrained ageing) for the 1:1 industrial-sized aircraft T-section component, which is a problematic component that is currently experiencing the residual stress-induced distortion issue. The integrated FE simulation included three sub-models (i) quenching, (ii) 1.5% cold rolling and (iii) T74 constrained ageing, using two sets of validated constitutive equations. The evolutions and distributions of the residual stress after quenching, cold rolling and constrained ageing were predicted. The simulation results showed that using the given process parameters, the distribution of the residual stresses from quenching was completely reversed and reduced. The final residual stresses in the transverse (σx) and thickness direction (σy) were reduced to ~ 0 MPa. The final residual stress in the rolling direction (σz) followed a “parabolic” distribution, with tensile stresses at the surface while uniform compression stresses ( ~ 140 MPa) at the core. This distribution is expected to benefit the subsequent machining distortion control. The predicted residual stress distributions after each processing stage further verified the effectiveness of the manufacturing process in producing low and controllable residual stresses and provide direct simulation results for industrial-sized components, which are valuable for future industrial application.

Microstructure and Mechanical Properties of 34CrMo4 Steel for Gas Cylinders Formed by Hot Drawing and Flow Forming.

An integral manufacturing process with hot drawing and cold flow forming was proposed for large-diameter seamless steel gas cylinders. The main purpose of this study was to find out the effects of the manufacturing process on the microstructure and mechanical properties of gas cylinders made of 34CrMo4 steel. Two preformed cylinders were produced by hot drawing. One cylinder was then further manufactured by cold flow forming. The experiments were carried out using three types of material sample, namely, base material (BM), hot drawing cylinder (HD), and cold flow-formed cylinder (CF). Tensile and impact tests were performed to examine the mechanical properties of the cylinders in longitudinal and transverse directions. Microstructure evolution was analyzed by scanning electron microscopy (SEM) and electron backscatter diffraction (EBSD) to reveal the relation between the mechanical properties and the microstructure of the material. It is found that the mechanical properties of the 34CrMo4 steel gas cylinders were significantly improved after hot drawing and flow forming plus a designed heat treatment, compared with the base material. The observations of microstructure features such as grain size, subgrain boundaries, and residual strain support the increase in mechanical properties due to the proposed manufacturing process.

A manufacturing process design for producing a membrane-based energy recovery ventilator with high aspect ratio support ribs

Heating, ventilation, and air conditioning systems represent nearly half of building energy usage in the United States. Recent building regulations requiring increased air turnover within buildings will result in even greater air conditioning usage. To alleviate these concerns, membrane-based heat-and-moisture exchangers known as energy recovery ventilators have been developed to reduce the energy expenditure of air conditioning systems by pre-conditioning incoming air through sensible and latent heat transfer with building air exhaust. In this work, we propose and validate a manufacturing process design for channel lamination based on surface mount adhesives capable of meeting the process requirements of a membrane-based ventilator. In particular, the device requires rib supports with height-to-width aspect ratios greater than one. The proposed manufacturing process design is capable of meeting this process requirement by stretching the adhesive after initial adhesive tacking. A manufacturing process flow diagram, a machine tool specification and a cost model are proposed for meeting process requirements. A set of design constraints are developed detailing the adhesive requirements necessary for meeting requirements. The cost model is validated by building a sub-scale mesochannel array demonstrating the ability to meet process requirements. Results show that additional work is needed to validate the curing step but that the process is capable of producing a mesochannel array with an acceptable level of variation.

Electroless-Deposited Platinum Antennas for Wireless Surface Acoustic Wave Sensors.

In an effort to develop a cost-efficient technology for wireless high-temperature surface acoustic wave sensors, this study presents an evaluation of a combined method that integrates physical vapor deposition with electroless deposition for the fabrication of platinum-based planar antennas. The proposed manufacturing process becomes attractive for narrow, thick, and sparse metallizations for antennas in the MHz to GHz frequency range. In detail, narrow platinum-based lines of a width down to 40 m were electroless-deposited on -AlO substrates using different seed layers. At first, the electrolyte chemistry was optimized to obtain the highest deposition rate. Films with various thickness were prepared and the electrical resistivity, microstructure, and chemical composition in the as-prepared state and after annealing at temperatures up to 1100 C were evaluated. Using these material parameters, the antenna was simulated with an electromagnetic full-wave simulation tool and then fabricated. The electrical parameters, including the S-parameters of the antenna, were measured. The agreement between the simulated and the realized antenna is then discussed.

Fabrication of complex 3D composites by fusing automated fiber placement (AFP) and additive manufacturing (AM) technologies

Automated fiber placement (AFP) is emerging as one of the advanced methods toward fabrication of polymer matrix based composite structures. This automated technique focuses on polymer composite manufacturing for use in a wide range of automotive and aerospace applications. The AFP process offers an elevated level of customization through the possibility of placing each individual tow at custom-designed trajectories. Additive manufacturing (AM) method, on the other hand, has the potential to fabricate functional end user parts of complex geometries, thus eliminating the need for costly tooling, multi-step processing and fasteners or joints. This paper will highlight the potential of fusing AFP and AM processes to fabricate complex 3D polymer based composite parts. A combination of these two processes suggests a promising option for composite materials development, improving composite structures in terms of complexity and customizability. The paper presents the adopted research methodology, background research, the design, development and set up of an experimental workcell that fuses AM and AFP, and the design methodology which is required to design complex composite parts using the proposed manufacturing process. Main challenges and opportunities are discussed, such as how restrictions of conventional composite production can be eased, and additional freedoms of design can be achieved.

Development of a micromachined accelerometer for particle acceleration detection

We are reporting on the design, fabrication, and experimental results for a micromachiend accelerometer that is intended to be used in the detection of acoustic signals, where the main requirements include low noise, wide bandwidth, and high linearity. The device design requirements are discussed and analytically modelled. Microfabrication details to build prototypes are provided in detail. The final device structure employs membrane as the suspension mechanism and a proof-mass made from the entire thickness of a wafer that is suspended above a fixed electrode. The proposed manufacturing process allows for precise and independent control of the structural components of the device and the capacitive gap. Prototype devices were fabricated and characterized. Measurements on the device performance demonstrate a 0.6 μg/Hz noise floor with resonance frequency of 5.2 kHz, sensitivity of ∼0.9 pF/g, and open-loop dynamic range of higher than 145 dB while operating at atmospheric pressure. The device meets the requirements for measuring sonar signals in the range of 50 Hz to 5 kHz under low environmental noise conditions.

Mechanical performance of epoxy coated AR-glass fabric Textile Reinforced Mortar: Influence of coating thickness and formulation

Abstract The mechanical performance of epoxy coated AR-glass fabric reinforced composite is investigated. A three-stage manufacturing process is considered, which involves fabric surface functionalization, liquid coating deposition and long-term setting and finally fabric embedment in the mortar matrix. Two epoxy coatings are considered, which only differ by the hardening agent. However, coating thickness is significantly diverse as a result of modified viscosity during liquid deposition. Performance is assessed in uni-axial tension as well as in three-point bending and it is expressed in terms of strength curves, data dispersion, crack pattern and failure mechanism. Remarkably, despite being very similar, the analyzed coatings produce a significantly different performance, especially when data dispersion is incorporated and design limits are considered. Indeed, although both coatings are able to consistently deliver fabric rupture at failure, only the thinnest is associated with small data scattering and an almost plastic post-peak behavior in bending. The associated design elongation limit reaches the maximum allowed value according to the ICC guidelines. In fact, it appears that coating thickness plays a crucial role in determining mechanical performance and fabric flexibility. The proposed manufacturing process proves extremely effective at enhancing matrix-to-fabric adhesion and thereby prevent telescopic failure.