Cost-effective Fabrication Research Articles

All Knitted and Integrated Soft Wearable of High Stretchability and Sensitivity for Continuous Monitoring of Human Joint Motion.

E-textiles have recently gained significant traction in the development of soft wearables for healthcare applications. However, there have been limited works on wearable e-textiles with embedded stretchable circuits. Here, stretchable conductive knits with tuneable macroscopic electrical and mechanical properties are developed by varying the yarn combination and the arrangement of stitch types at the meso-scale. Highly extensible piezoresistive strain sensors are designed (>120% strain) with high sensitivity (gauge factor 8.47) and durability (>100,000 cycles), interconnects (>140% strain) and resistors (>250% strain), optimally arranged to form a highly stretchable sensing circuit. The wearable is knitted with a computer numerical control (CNC)knitting machine that offers a cost effective and scalable fabrication method with minimal post-processing. The real-time data from the wearable is transmitted wirelessly using a custom designed circuit board. In this work, an all knitted and fully integrated soft wearable is demonstrated for wireless and continuous real-time sensing of knee joint motion of multiple subjects performing various activities of daily living.

(Invited) Integration of InP Heterojunction Bipolar Transistors on Silicon Substrates for 6G Networks

The power amplifier (PA) in an RF front-end module operating above 100 GHz required for 6G wireless networks is the most power-hungry device circuit component. In that respect, InP-based heterojunction bipolar transistors (HBT) clearly outperform other PA technologies, but being processed on small size wafers, they lack a cost-effective fabrication for mass production. This paper presents a comprehensive comparison of various integration approaches for InP-based HBTs. A key aspect in achieving high yield device fabrication is the use of large-diameter silicon wafers. This study discusses the advantages and disadvantages of different InP-based HBT integration concepts on Si, emphasizing important factors for upscaling InP technologies. Furthermore, this work introduces nano-ridge engineering (NRE), a novel monolithic III-V integration approach currently being explored at imec, which holds the potential for cost-effective and complementary metal oxide semiconductor (CMOS)-compatible production.

Ultrafast and Cost-Effective Fabrication of High-Performance Carbon-Based Flexible Thermoelectric Hybrid Films and Their Devices.

Due to their cost-effectiveness and industry-scale feasibility, carbon-based composites have been considered to be promising thermoelectric materials for low-grade power generation. However, current fabrications for carbon-based composites are time-consuming, and their thermoelectric properties are still low. Herein, we develop an ultrafast and cost-effective hot-pressing method to fabricate a novel carbon-based hybrid film, which consists of ionic liquid/phenolic resin/carbon fiber/expanded graphite. This method only costs no more than 15 min. We found that the expanded graphite as the major component enables high flexibility and the introduction of phenolic resin and carbon fiber enhances the shear resistance and toughness of the film, while the ion-induced carrier migration contributes to a high power factor of 38.7 μW m-1 K-2 at 500 K in the carbon-based hybrid film. After the comparison based on the ratios between the power factor with fabrication time and cost among the current conventional carbon-based thermoelectric composites, our hybrid films show the best cost-effective property. Besides, a flexible thermoelectric device, assembled by the as-designed hybrid films, shows a maximum output power density of 79.3 nW cm-2 at a temperature difference of 20 K. This work paves a new way to fabricate cost-effective and high-performance carbon-based thermoelectric hybrids with promising application potential.

Practical work for exploring the capabilities and benefits of CNC technology

Computer Numerical Control (CNC) technology's precision and complexity in design are two of its greatest strengths. CNC machines can make consistent and accurate cuts, drills, and shapes because they are controlled by computer programs. This precision is especially useful in sectors where producing complex components is mission-critical, such as the aerospace, medical, and automotive industries. The capacity to automate mundane processes is another benefit of CNC technology. CNC machines, once programmed, can mass-produce parts with little to no human intervention, greatly boosting efficiency and lowering production costs. By eliminating the potential for human error, this automation also increases the reliability and consistency of the final output. In addition, CNC machinery can facilitate quicker production runs and shorter setup times, both of which boost productivity. Enhanced productivity has the potential to boost a company's bottom line. Overall, CNC technology has the potential to revolutionize manufacturing by facilitating the rapid, precise, and cost-effective fabrication of intricate parts and components. Since this is a hotspot for innovation, new uses and capabilities appear frequently.

Beyond mobile phone displays: Flat panel display technology for biomedical applications

Organ-on-Chips (OoCs) have emerged as a human-specific experimental platform for preclinical research and therapeutics testing that will reduce the cost of pre-clinical drug development, provide better physiological relevance and replace animal testing. Yet, the lack of standardization and cost-effective fabrication technologies can hamper wide-spread adoption of OoCs. In this work we validate the use of flat panel display (FPD) technology as an enabling and cost-effective technology platform for biomedical applications by demonstrating facile integration of key OoC modules like microfluidics and micro electrode arrays (MEAs) in the standardized 96-well plate format. Individual and integrated modules were tested for their biological applicability in OoCs. For microelectrode arrays we demonstrate 90–95% confluency, 3 days after cell seeding and >70% of the initial mitochondrial cell activity for microfluidic devices. Thus highlighting the biocompatibility of these modules fabricated using FPD technology. Furthermore, we provide two examples of monolithically integrated microfluidics and microelectronics, i.e. integrated electronic valves and integrated MEAs, that showcase the strength of FPD technology applied to biomedical device fabrication. Finally, the merits and opportunities provided by FPD technology are discussed through examples of advanced structures and functionalities that are unique to this enabling platform.

Silicon nanostructure – Smart antibacterial, cost-effective implantable material for health care applications

Silicon nanocomposites and nanomaterials have been instrumental in diagnose and effective treatment of bacterial complications. Over the years, usage of antibiotics for antibacterial applications has been a conventional remedy for their highly effectiveness nature, early pain relaxation, and cost effectiveness. But due to bacterial resistance to antibiotics, these medicines do not neutralise the bacteria completely rather provide a temporary solution against the microbes. The techniques applied for treatment of bacterial cells involves fusion of drug coated nanoparticles on bacterial cell walls and its impinging to the targeted bacterial cell wall for release of drug molecules to enter into the microorganisms. These nanoparticles can be polymeric nanoparticles, solid lipid nanoparticles as well as liposomes for anti microbial drug delivery. Also, nanoparticles-based technique for drug delivery has certain advantages over local antibiotic treatment since they favour release of drug at appropriate sites, offers no side effects having minimum drug resistance developments, enables drug solubility, and transport multiple drugs at a time. Further, tailoring of Silicon Nanostructures (SiNs) to obtain porous SiNs enhances their drug loading capacity for targeted delivery of antibiotics on affected cells. Effective bacteria neutralisation is hindered by the formation of biofilms around bacterial cellular cells to which antibiotics prove to be ineffective, however usage of SiNPs and SiNs provide to be an effective solution for easy malfunctioning of bacterial cells. In our prospects, Metal Assisted Chemical Etching (MAC-Etching) is adopted as the cost-effective fabrication methodology for obtaining versatile nanostructures of Si. The operating temperature and etching time have considerable effects on geometries of SiNs ranging from Si Nanoporous structures to highly branched zigzag porous Si Nanostructures. The high porosity levels of as obtained SiNs can be exploited as a potential advantage for drug coating and as an application in bio- implantable material in biomedical field. The so-obtained SEM images of SiNs are analysed using iMAGEJ software producing area distribution plots of all nanostructures. The results of simulation work depict that majority of SiNPs have negligible area having large surface to volume ratio, and so can be largely exploited for effective interfacing onto bacterial cells. Our work demonstrates the use of SiNs synthetization using MAC-Etching as smart anti-bacterial surfaces since the optimized response is obtained as the morphology of as-synthesised SiNs varies.

Facile fabrication of optical diffusers by ablation-assisted nanosecond laser micromachining of glass substrates

Optical diffusers are essential components in modern technologies such as liquid crystal displays (LCDs), light emitting diodes (LEDs), imaging systems, etc., and a facile, quick, and cost effective fabrication technique is highly desired. Among the various known techniques femtosecond laser micromachining of glass substrates is known to work well for this purpose at the expense of high fabrication cost. On the other hand, low-cost nanosecond laser micromachining at 1064 nm does not always work well for most of the commonly used glass substrates. We demonstrate that this dilemma can be easily solved by ablation-assisted nanosecond laser micromachining of glass, where a metal target is placed just behind the glass substrate and the nanosecond laser is focused to the metal target through the glass so that the back surface of the glass substrate is efficiently etched by ablation fragments and plasma of the metal target. By varying the laser parameters and the gap between the glass and metal target we can control the optical properties of the fabricated diffusers. We also demonstrate that laser cleaning is an efficient way to remove all deposits after laser micromachining. All those results indicate that the demonstrated technique is a facile, quick, and cost effective fabrication method of optical diffusers.

Non-ultrawide bandgap CsPbBr3 nanosheet for sensitive deep ultraviolet photodetection

In this study, we report the fabrication of a sensitive deep ultraviolet (DUV) photodetector by using CsPbBr3 nanosheets synthesized through confined-space growth at room temperature. The peak photoresponse of the device upon illumination blueshifts with decreasing thickness and a 68 nm CsPbBr3 nanosheet based device displays a peak response to 265 nm illumination, showing responsivity and specific detectivity of 85 mA/W and 4.05 × 1011 Jones at 3 V bias, respectively. Theoretical simulation reveals that the blueshift is associated with the wavelength-dependent absorption coefficient of CsPbBr3 nanosheet: incident light with shorter wavelengths can be absorbed on the superficial surface, while long-wavelength light has a larger penetration depth, leading to dominant DUV absorption in thinner CsPbBr3 nanosheet. This work will shed light on the facile and cost-effective fabrication of DUV photodetectors from non-ultrawide bandgap (UWBG) all-inorganic perovskite materials.

Color-tunable multilayered laminated luminescent solar concentrators based on colloidal quantum dots

Luminescent solar concentrators (LSC) are a promising technology for building integrated photovoltaics (BIPV). Besides obtaining satisfactory efficiencies and aesthetic appeal, a simple and low-cost fabrication process is required to deploy large-scale LSCs. Herein, we introduced a facile and cost-effective fabrication method to obtain laminated LSC (L-LSC) devices. By optimizing the fabrication parameters, L-LSC based on polymer substrates exhibited higher efficiency (power conversion efficiency, PCE=0.24%, external photon efficiency, ηext=4.14% and optical efficiency, ηopt=3.46%) compared to glass-based L-LSC (PCE=0.09%, ηext=1.59%, ηopt=1.76%) due to their excellent optical properties and good compatibility with the laminated emissive layer. Using the optimized L-LSC device, a color-tunable multilayered L-LSC structure is then proposed. By embedding different QDs into two interlayers, the color appearance of the device can be tuned, simultaneously improving the overall efficiency. This study presents a notable advancement towards a practical application of L-LSCs with a satisfactory efficiency and color aesthetics for sustainable BIPVs.

Fabrication of wafer-scale ordered micro/nanostructures for SERS substrates using rotational symmetry cantilever-based probe lithography

Surface-enhanced Raman spectroscopy (SERS) is considered as a powerful analytical tool with a fingerprint-level resolution. Nevertheless, it is still challenging to fabricate large-area, sensitive, and reproducible SERS substrates through facile and cost-effective process. Herein, a novel double-layer rotational symmetry cantilever (DRSC)-based probe lithography was proposed for the facile and cost-effective fabrication of wafer-scale ordered micro/nanostructures towards SERS applications. Using finite element simulation, the architecture of DRSC was optimized, and its strength and fatigue were checked. Several typical fabrication parameters were evaluated using the DRSC-based probe lithography. The results indicated that the proposed lithography exhibited identical stiffness in all horizontal directions, and can effectively suppress the horizontal drift and achieve high-precision fabrication under the condition of high-speed reciprocating processes. Several high-quality micro/nanostructures were achieved to demonstrate its excellent ability in large-area and high-precision fabrication. SERS spectra of malachite green (MG) indicated an impressive enhancement, excellent stability, and high reproducibility (including intra-substrate and batch-to-batch sampling), and practical applications of prepared SERS substrates were demonstrated by detecting MG residues from various water environments and fish scales. This study provides a promising approach for the facile and cost-effective fabrication of large-area, sensitive, and reproducible SERS substrates.

Structural coloration with two-dimensional nanostructures fabricated by elliptical vibration nanoindentation

Structural color stemming from the two-dimensional (2D) nanostructures that induced light interference attracts more attention than 1D grating due to its higher design flexibility. However, the fast and cost-effective fabrication of pixel-by-pixel 2D nanostructures is challenging. This study prompts nanoindentation as a promising technique for fabricating 2D nanostructure on metallic surfaces by adding an ultrafast elliptical vibration on the nanoindenter. First, the elliptical vibration nanoindentation (EVN) process principle is analyzed. Next, an ultrafast elliptical vibration nanoindentation tool (UEVNT) with a maximum working frequency of 2 kHz is developed. Then, machining experiments were conducted on aluminum to evaluate the performance of EVN, whose results demonstrate the successful fabrication of pyramid-type nanostructures with a depth of hundreds of nanometers and a spacing of 1–3 μm. Based on the unique spatial diffraction characteristic of 2D nanostructures, a high-decoupling optical variable device has also been fabricated on the aluminum surface by rendering two images into two orthogonal observation directions. Finally, the 2D nanostructures on a metallic surface were transferred to the flexible polymer to fabricate a structural color-based bidirectional strain sensor. Stretching tests have been performed with results verifying the potential application of 2D nanostructures-induced structural color in the wireless measurement of mechanical deformation.

Cost-Effective Strategy for Developing Small Sized High Frequency PMUTs Toward Phased Array Imaging Applications

This article presents the development of small sized piezoelectric micromachined ultrasound transducer (PMUT) with cost effective fabrication process. Improved ultrasound imaging quality requires small sized, high frequency and high performance PMUT cell and further high density arrays. Fabrication with currently well developed and cost effective sacrificial process benefits their mass production and application. To determine small sized AlN PMUT cell, commonly reported elastic layer materials including Si, Si3N4, SiO2 are compared by mathematic derivation under the same stack thickness and device frequency. SiO2 has the smallest Young modulus and it serving as elastic layer can yield the expected one. Arranging SiO2 layer at the top of the device is compatible with phosphor silicate glass (PSG) sacrificial manufacturing process for cost effective fabrication. This fabrication strategy further downsizes cell size since extra device protection layer is omissible. We make 12MHz PMUT linear arrays with cell diameter, thickness and element pitch to be <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$40~\mu \text{m}$ </tex-math></inline-formula> , <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.9~\mu \text{m}$ </tex-math></inline-formula> and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$120~\mu \text{m}$ </tex-math></inline-formula> . Their electrical and ultrasound results are quite uniform at both device and wafer levels. One PMUT line with 20 parallelly connected units can produce pulse-echo signal with over 25dB SNR at 10mm distance. Lateral and axial ultrasound imaging resolutions of ~1 mm and ~0.3 mm are obtained in practical verification. These indicate the good ultrasound performance of our developed PMUT array. Plus the advantages of small size and cost effective fabrication, using SiO2 elastic layer and arranging it at the top of the device is a competitive strategy to develop phased array PMUTs. [2022-0184]

Tolerancing for an Apple Pie: A Fundamental Theory of Tolerances

Abstract Tolerancing began with the notion of limits imposed on the dimensions of realized parts both to maintain functional geometric dimensionality and to enable cost-effective part fabrication and inspection. Increasingly, however, component fabrication depends on more than part geometry as many parts are fabricated as a result of a “recipe” rather than dimensional instructions for material addition or removal. Referred to as process tolerancing, this is the case, for example, with IC chips. In the case of tolerance optimization, a typical objective is cost minimization while achieving required functionality or “quality.” This article takes a different look at tolerances, suggesting that rather than ensuring merely that parts achieve a desired functionality at minimum cost, a typical underlying goal of the product design is to make money, more is better, and tolerances comprise additional design variables amenable to optimization in a decision theoretic framework. We further recognize that tolerances introduce additional product attributes that relate to product characteristics such as consistency, quality, reliability, and durability. These important attributes complicate the computation of the expected utility of candidate designs, requiring additional computational steps for their determination. The resulting theory of tolerancing illuminates the assumptions and limitations inherent to Taguchi’s loss function. We illustrate the theory using the example of tolerancing for an apple pie, which conveniently demands consideration of tolerances on both quantities and processes, and the interaction among these tolerances.

Achieving robust and enhanced pool boiling heat transfer using micro–nano multiscale structures

Vapor chamber thermal management technology has become a high-reliability cooling method to solve the heat dissipation problem. However, this is still a crucial challenge to overcome when the capillary wick is exposed to harsh service environments. In this paper, a fabrication method of capillary wicks with micro–nano multiscale structures combining micro hot embossing and high-pressure hydrothermal treatment is proposed. Micro pyramid-channel is fabricated by micro hot embossing, and when the axis-to-diameter ratio of nanobars reaches 3.16–3.17, superhydrophilicity is realized. In the pool boiling experiment, the heat transfer performance of the pyramid-channel is better than that of the triangular-channel. Importantly, the superhydrophilic micro–nano structures achieve significantly improved critical heat flux and heat transfer coefficient simultaneously, increased by 162.1% and 180.8%. Moreover, the fabricated micro–nano capillary wick, which comprise high-strength pyramid-channel and specific wettability nanostructures, can maintain their outstanding superhydrophilicity and superhydrophobicity and their enhanced boiling property even after high-pressure high-velocity fluid scouring. The proposed cost-effective fabrication method provides an ideal and industrialized approach for the mass production of vapor chamber capillary wicks suitable for severe application environments.

Supramolecular G-quadruplex hydrogels: Bridging fabrication to biomedical application

G-quadruplex hydrogel is a class of self-assembled supramolecular hydrogel formed by guanine derivatives. As a biomimetic hydrogel, G-quadruplex hydrogels demonstrate wide biomedical applications, such as drug delivery, tissue engineering, and biosensing. The advantages of using G-quadruplex hydrogels include adequate biocompatibility and biodegradability, tunable multifunctionality, and cost-effective and large-scalable fabrication process. In this review, we focus on recent progress in the fabrication and characterization of G-quadruplex hydrogels to help readers understand the principles of G-quadruplex hydrogel formation. Meanwhile, the applications of G-quadruplex hydrogels in the biomedical area are discussed, aiming to pave the way for downward clinical or industry translation. The development of G-quadruplex hydrogel is still in its infancy. We hope this review will boost the development of this area and that more applications of G-quadruplex hydrogel will be developed.

Internet of Things Wearable Healthcare System for Monitoring the Challenges of COVID-19 Pandemic

During the COVID-19 situation, various application-based work has to be studied and deployed to enable an IoT-based health framework. This work-based study may guide professionals in envisaging solutions to related problems and fighting against the COVID-19 type pandemic. Therefore, it identifies various technologies of IoT-based systems for monitoring pandemic situations. The mechanisms included in IoT like actuators, sensors, and the cloud-based network serves to help people from home rather than visiting the hospital occasionally. It uses optimizers to train the “noise” and “cough” target classes. Mel Frequency Cepstral Coefficients (MFCCs) were initially employed in several speech processing approaches, but as the discipline of Music Information Retrieval (MIR) advanced alongside machine learning, it was discovered that MFCCs could accurately capture timbre. Overall, the study finds different IoT applications for the medical area during the pandemic situation with detailed descriptions. In this present condition, advanced methodologies have given way to innovation in day-to-day life. The IoT-based model provides an enhancement of 98.8% with a minimum training loss of 0.15. The framework depicts the excellent working of the proposed framework, and a true positive value of around 96.6% is shown in the confusion matrix and a true negative rate of around 97% was illustrated using this model. By making it possible for the cost-effective fabrication of wearable sensors through printing on a variety of flexible polymeric substrates, the rapid advancements in solution-based nanomaterials presented a hopeful viewpoint to the field of wearable sensors. This review focuses on the most recent significant advancements in the field of wearable sensors, including novel nanomaterials, manufacturing techniques, substrates, sensor types, sensing mechanisms, and readout circuits. It concludes with difficulties in the subject's future application.

TiO2-SnS2 Nanoheterostructures for High-Performance Humidity Sensor

The larger surface-to-volume ratio of the hierarchical nanostructure means it has attracted considerable interest as a prototype gas sensor. Both TiO2 and SnS2 can be used as sensitive materials for humidity sensing with excellent performance. However, TiO2-SnS2 nanocomposites are rarely used in humidity detection. Therefore, in this work, a new humidity sensor was prepared by a simple one-step synthesis process based on nano-heterostructures, and the humidity sensing performance of the device was systematically characterized by much faster response/recovery behavior, better linearity and greater sensitivity compared to pure TiO2 or SnS2 nanofibers. The enhanced sensitivity of the nanoheterostructure should be attributed to its special hierarchical structure and TiO2-SnS2 heterojunction, which ultimately leads to a significant change in resistance upon water molecule exposure. In consideration of its non-complicated, cost-effective fabrication process and environmental friendliness, the TiO2-SnS2 nanoheterostructure is a hopeful candidate for humidity sensor applications.

Topical advances in fabrication technologies of perovskite solar cell heterostructures: Performance and future perspective

Organic-inorganic hybrid perovskite light-harvesting materials are becoming one of the most capable potential contenders in photovoltaic technology because of their low-cost fabrication, ease of processing, and high power conversion efficiency (PCE). However, it is still challenging to extend these perovskite materials with a cost-effective fabrication technique to meet the demand for roll-to-roll manufacturing and mass production. Several fabrication methods have been developed and tested with different device configurations to enhance properties like device stability and photon-to-current conversion efficiency. The quality of thin-films has a vital role in determining the suitable fabrication method and appropriate structure to improve the overall performance of perovskite devices. This review article summarizes various deposition techniques used in fabrication of perovskite solar cells (PSCs), device technologies for perovskite light-absorbing heterostructures and future research perspectives.

Fiber-reinforced liquid crystalline elastomer composite actuators with multi-stimulus response properties and multi-directional morphing capabilities

Liquid crystalline elastomers (LCEs) are promising materials for soft actuations. LCE composites (LCECs), via the inclusion of fillers into LCEs, bring diverse functionalities and stimuli-responsive capabilities. It is still a challenge to improve the mechanical properties of LCEC and ensure that the material can perform reversible transformations. Here we present a cost-effective LCEC design and fabrication method by dispersing continuous carbon fibers and carbon nanotubes into LCEs, forming a new type of LCEC actuator. We found that through adjusting the angle (such as 45° and 90°) between the carbon fiber and the stretching axis of LCEC matrix, complex deformable geometries can be easily achieved including bending and twisting structures with enhanced storage modulus (400.9 MPa at 25 °C). Furthermore, the LCEC actuators could be driven by various stimuli including heat (120 °C), light (800 mW cm−2), and electricity (2.0 V). As a result, our new LCEC actuator outperforms other LCE actuators by having the largest number of morphing geometries and stimulus-responsive modes. Our LCEC design and manufacturing strategy represents a promising general methodology that can be easily extended to other continuous fibers (such as glass fiber, aramid fiber, etc.) filled LCECs, bringing even rich shape-changing capabilities that are needed for soft robots and beyond.

Medical micro- and nanomotors in the body.

Attributed to the miniaturized body size and active mobility, micro- and nanomotors (MNMs) have demonstrated tremendous potential for medical applications. However, from bench to bedside, massive efforts are needed to address critical issues, such as cost-effective fabrication, on-demand integration of multiple functions, biocompatibility, biodegradability, controlled propulsion and invivo navigation. Herein, we summarize the advances of biomedical MNMs reported in the past two decades, with particular emphasis on the design, fabrication, propulsion, navigation, and the abilities of biological barriers penetration, biosensing, diagnosis, minimally invasive surgery and targeted cargo delivery. Future perspectives and challenges are discussed as well. This review can lay the foundation for the future direction of medical MNMs, pushing one step forward on the road to achieving practical theranostics using MNMs.