Cost-effective Fabrication Process Research Articles

High Resolution OLED Using Eco-Friendly Quantum-Dots Functional Color-Filter

Recently, the quantum-dots enhancement film (QDEF) has been introduced to improve the color gamut for LCD technology. Although this QDEF has been realized approximately zero cross-talk between the main blue-(B-), green-(G-), and red-(R-) light emissions in LCDs to almost zero, it would have a considerable loss (> 10%) in the intensity of light due to the light absorbed in the resin medium and transparent sheets. To solve this undesirable loss of light, the LCD technology has been adopted the QD-functional CF LCD which is simply adding the B, G, and R-QDs directly to the color filters (CFs) in conventional LCDs using a blue back-light-unit (BLU). Motivated by this idea, we suggest this QDCF technology for organic light emitting diode (OLED) devices. In our research, B-, G-, and R-QD-functional CFs were fabricated by using eco-friendly ZnSe / ZnS and InP-based core/shell structure, showing a high photoluminescence-quantum yield (PL-QY) and a narrow full-width at half-maximum (FWHM) as well as a good flexibility in tuning the suitable PL peak wavelength between emitted from QDs and transmitted from CFs. To make the QD-functional color filter layer, blue, green, and red emitting quantum dots dissolved in hexane of 20wt%. Then they were mixed with the blue, green, and red color filters at a rate of 1 to 1. In order to disperse the QD-functional color filter well, ultra-sonication was performed for 10 minutes. Then, the QD-functional color filter solution was coated on the cleaned substrate using the drop process. After drying for 60 minutes, we analyzed the QD-functional CF structures through photoluminescence and UV-visible spectroscopy. It was confirmed that the B-, G, and R-QDs functional CF OLED exhibited that the PL peak emit at 432, 530, and 621 nm-wavelength with a PL FWHM of 13.4, 39, and 42 nm and a PL-QY of 71, 85, and 75 %, respectively. As a result, the RGB color gamut of the proposed OLED using the fabricated QDs function CFs presented a higher value of 118 % (NTSC) and 88.5% (Rec. 2020) result from the zero cross-talk among PL spectrums of RGB colors (Figure 1). These findings make our study unique and applicable for ultra-super high-resolution OLED and become the cornerstone for trying different types of QDs in QD-functional CFs through a simple, environment-issue free, and cost-effective fabrication process. We will present in detail the wide RGB gamut characteristics and optical properties of QDCF structures using environmentally friendly ZnSe / ZnS and InP quantum dots in addition to driving OLED. Figure 1

Facile Preparation of a Hierarchical C/rGO/FeO x Composite with Superior Microwave Absorption Performance.

A hierarchical carbon/reduced graphene oxide (rGO)/FeO x (CGF) composite has been successfully prepared utilizing a sequential process of immersion and carbonization. During the immersion of melamine foam in a liquid precursor, graphene oxide (GO) is covered on the interconnected framework of the foam and is decorated by metallic ions simultaneously. Therefore, the hierarchical structure is constructed in one step. The CGF composite exhibits a maximum reflection loss of as much as -51.2 dB and an ultrawide effective absorption bandwidth of 8.2 GHz. Detailed investigation suggests that the hierarchical structure contributes to the superb microwave absorption performance significantly through enhancing the interfacial polarization and inducing multireflection of microwave. The simple and cost-effective fabrication process together with the excellent microwave absorption performance endows the CGF composite with great potential for practical application.

NO2 sensing properties of porous Au-incorporated tungsten oxide thin films prepared by solution process

The use of chemoresistive gas sensors based on metal oxides has expanded to various fields such as medical diagnosis and air quality systems as well as gas leakage detectors with the development of the Internet of Things. Accordingly, sensitivity, selectivity, power consumption, and reproducibility become important factors in the development of gas sensors. Herein, we developed a facile method to fabricate a gas sensor based on porous Au-incorporated tungsten trioxide (WO3) thin films for highly sensitive and selective NO2 sensing. The mixed solution of ammonium tetrathiotungstate [(NH4)2WS4] and gold chloride (AuCl3) was transformed to Au-incorporated WO3 thin films through the spin-coating and annealing process. The gas sensors based on the Au-incorporated WO3 thin films exhibited improved sensitivity, selectivity, and response time upon exposure to NO2 with a significantly low theoretical detection limit of 28 ppt at 150 ℃ compared to gas sensors based on the pristine WO3 thin film. The high sensing properties are attributed to the porous structure and catalytic effects of Au nanoparticles. In addition to these remarkable NO2 sensing properties, the facile and cost-effective fabrication process enlarges the potential of the Au-incorporated WO3 thin films for practical and commercial gas sensing applications.

An experimental analysis on the performance of single mode-multimode-single mode and multimode- single mode-multimode fiber optic sensor

A cost effective and simple fabrication process for Mach Zehnder Interferometer (MZI) fiber based sensor has been proposed based on single mode-multimode-single mode structure and multimode-single mode-multimode. These proposed structures employed a standard fusion arc splicing by varying the length of sensing region instead of the structures. This sensor has been experimentally demonstrated for three different concentration of solutions such as water, 1mol sucrose solution and oil with the refractive index of 1.333, 1.384 and 1.464 respectively. Furthermore, the intention of this experiment is to determine which structure that provides superior performance in terms of the sensitivity of the device. The operating wavelength of different structures corresponds to the different refractive index. It is observed that the shifting response was influenced by the length of the sensing-area and the best sensitivity achieved for is -10.45nm/RIU.

Site-specific growth of oriented ZnO nanocrystal arrays.

We report on the growth of ZnO nanocrystals having a hexagonal, prismatic shape, sized 700 nm × 600 nm, on bare indium tin oxide (ITO) substrates. The growth is induced by a low ion flux and involves a low-temperature electrodeposition technique. Further, vertically aligned periodic nanocrystal (NC) growth is engineered at predefined positions on polymer-coated ITO substrates patterned with ordered pores. The vertical alignment of ZnO NCs along the c-axis is achieved via ion-by-ion nucleation-controlled growth for patterned pores of size ≈600 nm; however, many-coupled branched NCs with hexagonal shape are formed when a patterned pore size of ≈200 nm is used. X-ray diffraction data is in agreement with the observed morphology. A mechanism is proposed to interpret the observed site-specific oriented/branched growth that is correlated to the pore size. As ordered NC arrays have the potential to generate new collective properties different from single NCs, our first demonstration of a cost effective and facile fabrication process opens up new possibilities for devices with versatile functionalities.

Highly Transparent, Flexible Conductors and Heaters Based on Metal Nanomesh Structures Manufactured Using an All-Water-Based Solution Process.

Metal mesh is a promising material for flexible transparent conducting electrodes due to its outstanding physical and electrical properties. The excellent control of the sheet resistance and transmittance provided by the metal mesh electrodes is a great advantage for microelectronic applications. Thus, over the past decade, many studies have been performed in order to realize high-performance metal mesh; however, the lack of cost-effective fabrication processes and the weak adhesion between the metal mesh and substrate have hindered its widespread adoption for flexible optoelectronic applications. In this study, a new approach for fabricating robust silver mesh without using hazardous organic solvents is achieved by combining colloidal deposition and silver enhancement steps. The adhesion of the metal mesh was greatly improved by introducing an intermediate adhesion layer. Various patterns relevant to optoelectronic applications were fabricated with a minimum feature size of 700 nm, resulting in high optical transmittance of 97.7% and also high conductivity (71.6 Ω sq-1) of the metal mesh. In addition, we demonstrated an effective transparent heater using the silver mesh with excellent exothermic behavior, which heated up to 245 °C with 7 V applied voltage.

Fabrication of low cost and scalable carbon-based conductive ink for E-textile applications

In this work, we demonstrate a simple, highly scalable and cost-effective fabrication process of functional carbon black (CB) ink from burned charcoal of dry woods. Our process consists of both dry and wet medium blending of burned charcoals which reduces the consumption of high processing time and uses of sophisticated instruments to manufacture functional CB. The process includes formulation of functional CB ink prepared with poly-vinyl alcohol (PVA) binder, which is applied to the textile fabric using a simple pad-dry process. The sheet resistance and the loading percentage of carbon ink on the cotton fabric are saturated to ∼(25–28) kΩ/sq. and ∼(115–130) wt.% of the native fabric, respectively after 7 repeated padding cycles. The carbon-coated fabrics are demonstrated durable and reliable with repeated bending cycles. Although the resistance of the conductive fabric increases after the first wash cycle, interestingly, the resistance of the fabric tends to decrease in the following 11 consecutive wash cycles. The coated conductive fabrics are used as bend-sensors since it is able to detect very low bending angle for at least 1000 repeated bending cycles. Additionally, we demonstrate the use of carbon coated cotton fabric as heat-spreading materials of a textile heater.

Monolithic glass suspended microchannel resonators for enhanced mass sensing of liquids

Suspended microchannel resonators (SMRs) have been recently developed as highly sensitive platforms to study bacteria, cell populations, antibiotic resistance and other micron-sized analytes. Unfortunately, the time-consuming and challenging fabrication process represents the main drawback for the implementation of these platforms as new point-of-care devices. In this work, we show that femtosecond laser direct writing can be successfully implemented as a rapid and cost-effective 3D fabrication process able to define the suspended resonant structure and the embedded microfluidic channel in one-step, only. Furthermore, the use of a fused silica substrate guarantees a totally transparent resonator, a useful property in view of adding optical analyses to the mechanical one. The resonance properties of the fabricated SMRs were accurately characterized in terms of frequency, quality factor and Allan deviation, in different working conditions. The monolithic glass SMR is able to analyze with high precision liquids with different mass density, thanks to a density resolution (1.04·10−3 kg/m3) that is the highest among SMRs and microcapillaries used for this purpose. Finally, the effective biosensing capability is demonstrated by evaluating the microbial load of aqueous solutions containing different concentrations of P. fluorescens.

All-fabric flexible supercapacitor for energy storage

An all-fabric solid-state flexible supercapacitor has been fabricated using three types of commercial woven fabrics made of carbon fiber, activated carbon fiber, and polyester fiber, respectively. The activated carbon fiber fabric is viscose-based twill through carbonization and activation, followed by a deposition of CeO2 or ZnO nanoparticles through a hydrothermal process. The resultant fabric supercapacitor displays a high specific capacitance of 13.24 mF cm−2 at a scan rate of 0.2 mV s−1, an excellent capacitance retention of 87.6% at 5000 charge/discharge cycles, and a high energy density of 4.6 × 10−7 Wh cm−2 at a power density of 3.31 × 10−6 W cm−2. The supercapacitor is capable of bending in any angles without losing its performance, revealing an excellent flexibility. The facile, cost-effective fabrication process and excellent electrochemical performance allow this all-fabric solid-state flexible supercapacitor to be potentially used in new generation of wearable and self-powered electronic devices.

Dual Light Trapping and Water-Repellent Effects of a Flexible-Based Inverse Micro-Cone Array for Organic and Perovskite Solar Cells.

A simple and cost-effective fabrication process of a flexible-based inverse micro-cone array (i-MCA) structure textured on flexible transparent conductive electrodes (TCEs) was successfully demonstrated via a micro-imprinting process. The flexible i-MCA films exhibited an extremely high total transmittance of ∼93% and a haze of ∼95% with reduced reflectance while simultaneously demonstrating water-repellent properties. Introducing i-MCA on the illuminating side of organic solar cells (OSCs)- and perovskite solar cells-rigid glass substrate showed improved power conversion efficiencies (PCEs) due to the light trapping effect by multiple light bounces between cone array structures (forward scattering). This results in an increase of the optical path length in the photoactive layer. Similarly, flexible TCEs embedded with textured i-MCA increased the PCE by 14% for flexible OSCs. More importantly, i-MCA-TCE-based OSCs were highly flexible with 98% retention from the initial PCE at both 0° and at 60° even after 2000 bending cycles at a radius of 2 mm. This finding demonstrates that textured i-MCA is promising for improving: (a) the light harvesting efficiency of solar cells when installed in low-/high-latitude locations and (b) the wearable technology where a flexible device attached on curved objects could retain the PCE, even at an oblique angle, with respect to the normal incidence angle.

Design and characterisation of a dissolving microneedle patch for intradermal vaccination with heat-inactivated bacteria: A proof of concept study

This work describes the formulation and evaluation of dissolving microneedle patches (MNs) for intradermal delivery of heat-inactivated bacteria. Pseudomonas aeruginosa, strain PA01, was used as a model bacterium. Utilising a simple, cost effective fabrication process, P. aeruginosa was heat-inactivated and formulated into dissolving MNs, fabricated from aqueous blends of 20% w/w poly(methylvinylether/maleic acid). The resultant MNs were of sufficient mechanical strength to consistently penetrate a validated skin model Parafilm M®, inserting to a depth of between 254 and 381 µm. MNs were successfully inserted into murine skin and partially dissolved. Analysis of MN dissolution kinetics in murine ears via optical coherence tomography showed almost complete MN dissolution 5 min post-insertion. Mice were vaccinated using these optimised MNs by application of one MN to the dorsal surface of each ear (5 min). Mice were subsequently challenged intranasally (24 h) with a live culture of P. aeruginosa (2 × 106 colony forming units). Bacterial load in the lungs of mice vaccinated with P. aeruginosa MNs was significantly (p = 0.0059) lower than those of their unvaccinated counterparts. This proof of concept work demonstrates the potential of dissolving MNs for intradermal vaccination with heat-inactivated bacteria. MNs may be a cost effective, potentially viable delivery system, which could easily be implemented in developing countries, allowing a rapid and simplified approach to vaccinating against a specific pathogen.

Thin Film of Amorphous Zinc Hydroxide Semiconductor for Optical Devices with an Energy-Efficient Beneficial Coating by Metal Organic Decomposition Process

An effective metal oxide coating with solution processes by the metal organic decomposition method as deposited at room temperature (RT) poses great challenge. In this study, we report the characterization and evaluation of the semiconductor properties of a zinc hydroxide thin film with RT just as deposition by solution coating method. The films worked well as an inter-layer of the organic photovoltaic cell and optimized the film thickness condition with chemical and physical properties. As a result, we achieved a power conversion efficiency performance level, which was almost similar to that in the cells used after calcination in the crystal ZnO inter-layer. The presented process without any additional decomposition energy is expected to make a significant contribution to the realization of a flexible and cost-effective solution process for device fabrication.

A Stretchable Array of Electronic Receptors for Esophageal Swallowing Robot for Biomimetic Simulations of Bolus Transport

This paper presents the design, fabrication, calibration, and implementation of a novel stretchable array of capacitive sensors that mimics human receptors for an esophageal swallowing robot. The array is used to measure deformation of the esophageal conduit wall and the interaction between food bolus and the esophagus in the form of pressure and shear stress, which is a novel in vitro method of food bolus transport study. It is constructed from a thin sheet of copper-polyimide laminate via a cost effective fabrication process involving photolithography, wet etching, and laser engraving technique. Calibration is conducted individually on the pressure, shear, and strain sensor elements of the array. The pressure, shear, and strain sensors response exhibit an average hysteresis of 10.17%, 11.78%, and 26.37% caused by the soft silicon rubber encapsulation. Linear regression technique is used to determine the linear sensitivity transfer function for all the three sensors. The array is embedded beneath the surface of the esophageal conduit of the swallowing robot and a series of swallowing experiments are conducted. Three types of food bolus with a viscosity of 0.18, 0.62, and $1.55~\text {Pa}\cdot \text {s}$ are prepared using a commercial food thickener. The swallowing robot generates a peristaltic wave of 60-mm wavefront length and 40- $\text {mm}\cdot \text {s}^{-1}$ wave speed to mimic the swallowing action seen in the human esophagus. Manometer measurements are taken alongside for validation. The pressure sensor records maximum pressures of 2.24, 3.17, and 7.74 kPa, respectively, for the three types of bolus during swallowing. By comparison, the maximum pressures recorded by the manometer are 1.68, 2.82, and 8.08 kPa. The shear sensor on the other hand records maximum shear values of −0.3, −0.35, and −0.37 kPa, respectively, for the three food bolus mixtures. This works prove that the novel stretchable array of capacitive sensors can be used to mimic mechanoreceptors for the esophageal swallowing robot, which significantly extends its capability to be used by food scientists as a platform for a new novel method of bolus transport study.

Investigation of electrically conducting yarns for use in textile actuators

Textile actuators are an emerging technology to develop biomimetic actuators with synergetic actuation. They are composed of a passive fabric coated with an electroactive polymer providing with mechanical motion. Here we used different conducting yarns (polyamide + carbon, silicon + carbon, polyamide + silver coated, cellulose + carbon, polyester + 2 × INOX 50 μm, polyester + 2 × Cu/Sn and polyester + gold coated) to develop such textile actuators. It was possible to coat them through direct electrochemical methods, which should provide with an easier and more cost-effective fabrication process. The conductivity and the electrochemical properties of the yarns were sufficient to allow the electropolymerization of the conducting polymer polypyrrole on the yarns. The electropolymerization was carried out and both the linear and angular the actuation of the yarns was investigated. These yarns may be incorporated into textile actuators for assistive prosthetic devices easier and cheaper to get and at the same time with good mechanical performance are envisaged.

Water-insoluble, nanocrystalline, and hydrogel fibrillar scaffolds for biomedical applications

Recently, micro/nanofibrillar materials have been widely utilized for a variety of applications in many different fields of research due to their relatively large surface-to-volume ratios, high porosity, and three-dimensional connectivity, along with their cost-effective fabrication processes. Herein, we present a review of recent progress in the development of micro/nanofibrillar scaffolds with a specific focus on their biomedical applications. From the perspective of controlling polymer–polymer and polymer–water molecular interactions, we categorized the fibrillar scaffolds into insoluble, nanocrystalline, and hydrogel fibers. Based on our recent studies related to this research topic, we provide the significance and essential information on four different micro/nanofibrillar scaffolds: (1) solid micro/nanofibrillar scaffolds based on water-insoluble polymers, (2) hydrogel nanofibrillar network scaffolds based on crystalline bacterial cellulose, (3) hydrogel micro/nanofiber scaffolds based on partially precipitated PVA, and (4) hydrogel micro/nanofiber scaffolds based on chemically cross-linked PVA. The present discussion should provide guidance to researchers in selecting a micro/nanofibrillar scaffold suitable for their own purposes and should help inspire them to develop more sophisticated fibrillar scaffolds in the future. We reviewed the recent progress in the development of micro/nanofibrillar scaffolds for biomedical applications. We demonstrated the significance and essential information on four different micro/nanofibrillar scaffolds: (1) solid micro/nanofibrillar scaffolds (2) hydrogel nanofibrillar network scaffolds based on bacterial cellulose, (3) hydrogel micro/nanofiber scaffolds based on partially precipitated PVA, and (4) hydrogel micro/nanofiber scaffolds based on cross-linked PVA. This review would guide researchers for selecting a proper scaffold suitable for their own purposes and developing more sophisticated scaffolds.

Continuously tunable optical notch filter and band-pass filter systems that cover the visible to near-infrared spectral ranges.

Spatially continuous tunable optical notch and band-pass filter systems that cover the visible (VIS) and near-infrared (NIR) spectral ranges from ∼460 nm to ∼1,000 nm are realized by combining left- and right-handed circular cholesteric liquid crystal (CLC) wedge cells with continuous pitch gradient. The notch filter system is polarization independent in all of the spectral ranges. The band-pass filter system, when the left- and right-handed CLCs are arranged in a row, is polarization independent, while when they are arranged at right angles, they are polarization dependent; furthermore, the full-width at half-maximum of the band-pass filter can be changed reversibly from the original bandwidth of 36nm to 16nm. Depending on the CLC materials, this strategy could be applied to the UV, VIS, and IR spectral ranges. Due to the high performance in the broad spectral range, cost-effective facile fabrication process, simple mechanical control, and small size, it is expected that our optical tunable filter strategies could become one of the key parts of laser-based Raman spectroscopy, fluorescence, life science devices, optical communication systems, astronomical telescopes, and so forth.

Sonochemical synthesis of CuIn0.7Ga0.3Se2 nanoparticles for thin film photo absorber application

CuInGaSe2 (CIGS) has been considered as promising solar absorber material for thin film solar cells leading to efficiencies exceeding 22% on lab scale. CIGS thin film solar cells fabricated from CIGS nanoparticles (NPs) inks by nonvacuum techniques is essential for cost effective cell fabrication process and for upscaling. In this regard, one step sonochemical synthesis of CIGS NPs employing relatively non-toxic precursors of metallic salts and selenourea in an aqueous medium under ambient conditions is being presented. Precursor ratios and sonication time were optimized to realize high-quality chalcopyrite crystal phases of CIGS NPs obtained by sonochemical route. X ray diffraction, UV–vis–NIR, Raman, Energy dispersive spectroscopy and Transmission electron microscopy confirmed the formation of tetragonal chalcopyrite CIGS NPs with a band gap of 1.42 eV and NPs size of about 20 nm.

Cellular Structure Fabricated on Ni Wire by a Simple and Cost-Effective Direct-Flame Approach and Its Application in Fiber-Shaped Supercapacitors.

Cellular metals with the large surface/volume ratios and excellent electrical conductivity are widely applicable and have thus been studied extensively. It is highly desirable to develop a facile and cost-effective process for fabrication of porous metallic structures, and yet more so for micro/nanoporous structures. A direct-flame strategy is developed for in situ fabrication of micron-scale cellular architecture on a Ni metal precursor. The flame provides the required heat and also serves as a fuel reformer, which provides a gas mixture of H2 , CO, and O2 for redox treatment of metallic Ni. The redox processes at elevated temperatures allow fast reconstruction of the metal, leading to a cellular structure on Ni wire. This process is simple and clean and avoids the use of sacrificial materials or templates. Furthermore, nanocrystalline MnO2 is coated on the microporous Ni wire (MPNW) to form a supercapacitor electrode. The MnO2 /MPNW electrode and the corresponding fiber-shaped supercapacitor exhibit high specific capacitance and excellent cycling stability. Moreover, this work provides a novel strategy for the fabrication of cellular metals and alloys for a variety of applications, including catalysis, energy storage and conversion, and chemical sensing.

All polymer asymmetric Mach–Zehnder interferometer waveguide sensor by imprinting bonding and laser polishing**Project supported by the National Natural Science Foundation of China (Grant Nos. 61605057, 61475061, and 61575076), the Science and Technology Development Plan of Jilin Province, China (Grant No. 20140519006JH), and the Excellent Youth Foundation of Jilin Province, China (Grant No. 20170520158JH).

We present an all polymer asymmetric Mach–Zehnder interferometer (AMZI) waveguide sensor based on imprinting bonding and laser polishing method. The fabrication methods are compatible with high accuracy waveguide sensing structure. The rectangle waveguide structure of this sensor has three sensing surfaces contacting the test media, and its sensing accuracy can be increased 5 times compared with that of one surface sensing structure. An AMZI device structure is designed. The single mode condition, the length of the sensing arm, and the length deviation between the sensing arm and the reference arm are optimized. The length deviation is optimized to be in a refractive index range between 1.470 and 1.545. We fabricate the AMZI waveguide by lithography and wet etching method. The imprinting bonding and laser polishing method is proposed and investigated. The insertion loss is between −80.36 dB and −10.63 dB. The average and linear sensitivity are 768.1 dB/RIU and 548.95 dB/RIU, respectively. And the average and linear detection resolution of the sensor are 1.30 × 10−6 RIU (RIU: refractive index unit) and 1.82 × 10−5 RIU, respectively. This sensor has a fast and cost-effective fabrication process which can be used in the cases of requiring portability and disposability.

Fabrication of anode-supported microtubular solid oxide fuel cells by sequential dip-coating and reduced sintering steps

The expensive and time-consuming fabrication of microtubular solid oxide fuel cells (MT-SOFCs) is one of the main barriers for their commercialization. In this study, a sequential dip-coating coupled with co-firing process was developed to fabricate anode-supported MT-SOFCs using carbon rods as a sacrificial template. Both anode and electrolyte layers underwent co-firing at 1400 °C rather than conventional pre-sintering and co-sintering steps. The whole cell structure was fabricated through sequential dip-coating and drying cycles that are flexible to various tube sizes and fast in turnaround time. The fabricated MT-SOFCs were comprised of Ni–yttria-stabilized zirconia (3YSZ) anode support, scandia-stabilized zirconia (ScSZ) electrolyte, Ni-ScSZ anode functional layer, strontium-doped lanthanum manganite (LSM)–ScSZ cathode functional layer, and LSM cathode current collector layer, respectively. The electrochemical performance of the fuel cell was measured at temperatures between 650 and 800 °C. The MT-SOFC delivered stable performance for more than 50 h operation at 700 °C. The fabricated fuel cell also exhibited excellent thermal cycling stability. The results demonstrated that the sequential dip-coating coupled with co-firing is a simple, flexible and cost-effective fabrication process to produce reliable and robust MT-SOFCs.