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Manufacturing strategies to create three‐dimensional (3D) structures with multifunctional nanomaterials are of intense interest for fabricating building blocks in many electromechanical applications. A coil spring composed of graphene provides an important step toward the realization of all‐carbon devices, as it is one of the essential elements for a wide range of systems. In this connection, here an unprecedented fabrication strategy to create a new type of 3D coil spring composed of laser‐induced graphene springs (LIG‐S) which is spontaneously produced via the pyrolytic jetting technique, is presented. Similar to wood or metal shavings observed in traditional machining processes, a pair of LIG‐S with two opposite chiralities and controllable macroscopic dimensions is produced by a single scanning of a focused continuous‐wave (CW) laser on a polyimide (PI) substrate. The resulting LIG‐S, plastic shavings by laser, exhibits sufficient mechanical and electrical properties to enable many applications including strain‐tolerant spring electrodes, antennas, supercapacitors, gas sensors, and luminescent filaments under extreme conditions. Without using any conventional fabrication techniques or other labor‐intensive, time‐consuming, and expensive processes, this novel approach enables a high‐throughput mass production of macro‐, micro‐, and nanoscale featured LIG‐S that can be manufactured within seconds to realize many open opportunities in all‐carbon electromechanical systems. [ABSTRACT FROM AUTHOR]

A microscopic finite element model validated by the quasi-static mechanical test on lithium ion battery cell is presented in this study. The investigated condition involves three-point bending and cell discharge test, which include the mechanical response and thermal response of lithium ion battery cell. The cell is investigated through computational simulation. Results show great correlation between the experiment and finite element simulation. A microscopic model requires a greater effort during simulation. Investigating the fracture on steel casing and cell core is possible by considering the fracture mechanism in steel shell and jelly roll. The classic von-Mises criterion is applied to predict the failure of carbon steel shell, and the maximum von-Mises strain criterion is used to investigate the jelly roll region. On the basis of the verified battery cell model, battery package with microscopic model, including cell core (cathode, anode, and separator) is constructed to analyze the mechanical response of battery pack. The von-Mises criterion is used to predict the fracture point location of the battery pack with various packing modes and packing densities. [ABSTRACT FROM AUTHOR]

Quick progress in the field of smart wearable devices requires self‐sustainable power systems to help the devices execute the desired functions within a sufficient time scale. Because these devices have started to become small, light, compliant, complex, and multifunctional, it is challenging to provide them with the large amounts of energy necessary for their operation. Thus, future multifunctional wearable devices should not only incorporate mechanical flexibility for conformal contacts but also include sustainable energy units for stable operation. Hence, strategies for designing the assembly of nanoscale materials in macroscale‐structured devices have attracted intense interest, with an aim to achieve mechanically deformable and sustainable wearable devices while exploiting the recent advances in nanomaterials and device fabrication. This review highlights the recent progress in nanomaterial‐enabled and structured energy harvesting, energy storage, and hybrid devices for powering sustainable wearables. In particular, one summarizes describe biomechanical energy harvesters (piezoelectric nanogenerators and triboelectric nanogenerators), solar energy harvesters (solar cells), biothermal energy harvesters (thermoelectric nanogenerators), energy storage devices (batteries and supercapacitors), and hybrid devices and focus on the use of nanomaterials and device configurations in 1D, 2D, and 3D structures, with an aim to shape the future demand for self‐sustainable wearables. [ABSTRACT FROM AUTHOR]

Liquid precursor‐based laser‐induced reductive patterning techniques enable fast and economical fabrication of flexible electronics. Herein, an eco‐friendly and particle‐free copper ionic solution for laser‐induced reductive patterning of copper microlines on a low glass transition temperature and transparent flexible substrate is successfully developed. The solvent used is water and the reducing agent is l‐ascorbic acid. A continuous wave 640 nm laser is used as the heat source to initiate the reductive reaction and to deposit copper microlines on the substrate surface. The resistivity of the copper microlines fabricated with optimized laser parameters is remarkably low at 4.7 μΩ cm. To further improve the electrical conductivity and to enhance mechanical durability, the fabricated microlines are annealed using the same laser after the copper ionic liquid precursor is removed. The microstructures and mechanical robustness of the copper microlines, as well as the adhesion between the copper microlines and the substrate, are investigated by cyclic bending test, pull‐off test and scanning electron microscope analyses. Up to 39% reduction of electrical resistance and up to 77% enhancement of mechanical durability after a 1000 cycle bending test can be achieved by laser postprocessing. [ABSTRACT FROM AUTHOR]

The maximum effective thermal conductivity of the HPHX reached 12,798 W/m-K. Based on the prediction of an -NTU theoretical model for single-tube thermosyphons with boiling and film condensation, this indicates that the total resistance R SB tot sb of the HPHX decreases as the heat transfer rate and the airflow rate increase. Heating, ventilation, air conditioning and refrigeration (HVAC&R) systems provide physical environment comfort for the occupants at a possible expense of large amount of energy consumption. The heat transfer rate of 6.65 kW can be achieved with the evaporation section of the HPHX being immersed in a 150 °C oil bath at a cooling air flow rate of 1600 CMH. [Extracted from the article]

Radiofrequency ablation (RFA) is a minimally invasive technique, used with ultrasound or computed tomography guidance, which can produce tissue coagulation necrosis in various kinds of tumors in the human body. In the past 10 years, numerous studies about RFA in benign thyroid nodules have been published. Reviewing these studies, we noticed that the effectiveness of ablation was higher when it was performed with the “moving-shot technique” via an internally cooled electrode. A consensus statement published from the Korean Society of Radiology also suggested the moving-shot technique as a standard ablation procedure for benign thyroid nodule ablation in Korea. In Taiwan, most symptomatic benign nodules are currently treated with surgical removal. RFA for mass lesions is primarily performed for the treatment of metastatic hepatic tumors. In our case, we have attempted to introduce RFA for benign thyroid nodules in Taiwan. Because endocrinologists in Taiwan were not familiar with this technique, we adopted a stepwise approach in learning how to perform RFA. We conducted ex vivo animal ablation exercises to gain experience in setting the radiofrequency generator for the right ablation mode and appropriate power output. The thyroid nodule volume reduction rate after 1 year of follow up was approximately 50% in this case. The most important thing we learned from this trial is that we confirmed the safety of thyroid nodule ablation. To the best of our knowledge, this is the first reported study of RFA of a thyroid nodule in Taiwan. [ABSTRACT FROM AUTHOR]

Radiofrequency ablation is a minimally invasive technique that can produce tissue coagulation necrosis effectively and safely in humans with ultrasound or computed tomography guidance. The most frequent treatment site for radiofrequency ablation to date is the liver for hepatocellular carcinoma. Reviewing the history of radiofrequency ablation, we can see the evaluation of electrodes from conventional monopolar electrode to multiprobe arrays, hook expandable electrodes, and internally cooled electrodes. All of these are trying to ablate the tumor more widely and completely. From history, we also notice that the target can range from heart, neurological disorders, and thyroid diseases to a variety of other diseases, in addition to liver malignancy. Studies have already shown that radiofrequency ablation is an excellent alternative treatment for nodular thyroid disease, including benign and malignant lesions. For treatment of recurrent well-differentiated thyroid cancer, radiofrequency ablation has shown good results, such as no recurrence at treatment sites or reduced serum thyroglobulin level. The possible complications include hoarseness, hematoma, severe pain, esophageal perforation, or tracheal perforation. The reported rate for major complications in previous studies is low. Therefore, if the patients have severe comorbidity that is not suitable for reoperation for thyroid malignancy, radiofrequency ablation is a good alternative. Furthermore, radiofrequency ablation can be used for benign thyroid nodules to relieve local compressive symptoms. Some patients who receive such treatment for cosmetic reasons also show a satisfactory outcome. Here, we review previous studies about radiofrequency ablation in nodular thyroid disease in many aspects, such as ablation system, ablation techniques, ablation efficacy, and complications, both in benign thyroid nodules and recurrent thyroid cancer. [Copyright &y& Elsevier]

Abstract: In the present study, a hydrogen polymer electrolyte fuel cell (PEFC) micropowerplant in combination with a steam reformer fed by methanol and a direct methanol fuel cell (DMFC) micropowerplant are analyzed numerically regarding their exergetic efficiency. The effects of concentration and activation overpotentials, and ohmic resistance on the efficiency are considered in quasi-two-dimensional fuel cell models. The influence of significant operational parameters on the exergetic efficiency is examined numerically. Experimental results are conducted for the steam reformer. This work shows the importance of an exergy analysis of the fuel cell as part of an entire thermodynamic system generating electric power and compares PEFC and DMFC micropowerplants exergetically. [Copyright &y& Elsevier]

Copper oxide particles of various sizes and constituent phases were used to form conductive circuits by means of photonic sintering. With the assistance of extremely low-energy-density xenon flash pulses (1.34 J/cm2), a mixture of nano/submicron copper oxide particles can be reduced in several seconds to form electrical conductive copper films or circuits exhibiting an average thickness of 6 μm without damaging the underlying polymeric substrate, which is quite unique compared to commercial nano-CuO inks whose sintered structure is usually 1 μm or less. A mixture of submicron/nano copper oxide particles with a weight ratio of 3:1 and increasing the fraction of Cu2O in the copper oxide both decrease the electrical resistivity of the reduced copper. Adding copper formate further improved the continuity of interconnects and, thereby, the electrical conductance. Exposure to three-pulse low-energy-density flashes yields an electrical resistivity of 64.6 μΩ·cm. This study not only shed the possibility to use heat-vulnerate polymers as substrate materials benefiting from extremely low-energy light sources, but also achieved photonic-sintered thick copper films through the adoption of submicron copper oxide particles. [ABSTRACT FROM AUTHOR]

The frequency shift of a shear-horizontal surface-acoustic-wave (SH-SAW) biosensor in which the concentration of biomolecule is determined by the amount of its adsorption on the sensing film was studied. Simulation results were compared with experimental results to investigate its sensitivity and to develop a model to estimate the concentration of a cancer-related biomarker antigen epidermal growth factor (EGF) in the sample, with two types of sensing films, 3-aminopropyltriethoxysilane (APTES) and glutaraldehyde. With the concentration of the targeted biomarker varying from 0.2 to 5 ng/mL, a typical exponential relationship was found between the concentration and the frequency shift of the SH-SAW sensor. Measurement results showed a clear response of this immunosensor to the mass-loading effects of the antibody–antigen. The sensitivity of the glutaraldehyde film is greater than that of the APTES film owing to the chemisorption of the antibody. In the simulation, a shift of the SH-SAW resonant frequency due to added mass occurred on applying an incremental surface mass density on the sensing film, while in real applications, the concentration of the targeted biomarker to be absorbed in the sensing film is demanded. An empirical model was proposed to calculate the frequency shift in the simulation of the SH-SAW biosensor, corresponding to the concentration of specific biomolecules absorbed on a specific film. From the semi-empirical model, the sensitivity level is found to be 0.641 and 1.709 kHz/(ng/mL) for APTES and glutaraldehyde sensing films, respectively, at a biomarker concentration of less than 1 ng/mL. The developed method is useful for quickly estimating the frequency shift with respect to the concentration of the target molecules in the simulation for SH-SAW sensors. [ABSTRACT FROM AUTHOR]

We have fabricated CuO/ZnO nanowire (NW) catalyst for hydrogen production by solar thermal steam-methanol reforming (SMR). Such NW catalyst is expected to be more durable than the conventional nanoparticle catalysts by avoiding agglomeration. ZnO NWs are synthesized by hydrothermal growth on quartz and glass substrates. The ZnO NWs are then coated with CuO by thermal decomposition of copper nitrate using UV pulsed laser as a heat source for prototyping. A solar simulator is used as a heat source for the demonstration of the SMR in water/methanol mixture solution. Gas chromatograph (GC) exhibits increasing mole fraction of produced hydrogen with irradiated time. We then fabricate the catalyst on a large area glass plate substrate by the CuO deposition using an electric heater to confirm the SMR and demonstrate scaling-up. The SMR is briefly demonstrated by feeding water vapor/methanol mixture gas to the catalyst heated by an electric heater, giving thermally produced hydrogen (CO/H 2 = 0.019) in the product gas detected by GC. [ABSTRACT FROM AUTHOR]

Laser-assisted, one-step direct nanoimprinting of metal and semiconductor nanoparticles (NPs) was investigated to fabricate submicron structures including mesh, line, nanopillar and nanowire arrays. Master molds were fabricated with high-speed (200 mm s−1) laser direct writing (LDW) of negative or positive photoresists on Si wafers. The fabrication was completely free of lift-off or reactive ion etching processes. Polydimethylsiloxane (PDMS) stamps fabricated from master molds replicated nanoscale structures (down to 200 nm) with no or negligible residual layers on various substrates. The low temperature and pressure used for nanoimprinting enabled direct nanofabrication on flexible substrates. With the aid of high-speed LDW, wafer scale 4 inch direct nanoimprinting was demonstrated. [ABSTRACT FROM AUTHOR]

In this study a numerical simulation was carried out to analyze the transport phenomena in a vertical type metal organic chemical vapor deposition (MOCVD) reactor for Gallium Nitride (GaN) growth. The simulated results were compared and validated by experiment. The effects of showerhead design and chamber height are investigated and discussed. It was found that, by properly adjusting the height of the chamber, both the growth rate and film uniformity could be significantly improved. This is attributed to the suppression of the thermal and mass transfer boundary layers by the injection flow of reacting gas mixtures, as well as the confined vertical vortices caused by the geometry of the reduced space. However, inappropriate design of the distance between the showerhead and the susceptor can result in uneven distribution of the organic source in the vicinity of the substrate surface resulting in an uneven growth rate of the GaN film. Consequently, there exists an optimal chamber height that will give the best growth rate and uniformity to the GaN film as discussed in this study. This study provides comprehensive insight into the transport phenomena of GaN growth that includes coupled heat and mass transfer as well as chemical reactions. The results provide important information in a succinct format and enable decisions to be made about the showerhead and the geometrical design and size of a vertical MOCVD reactor. [ABSTRACT FROM AUTHOR]

Abstract: The present study proposes a combination of solar-powered components (two heaters, an evaporator, and a steam reformer) with a proton exchange membrane fuel cell to form a powerplant that converts methanol to electricity. The solar radiation heats up the mass flows of methanol–water mixture and air and sustains the endothermic methanol steam reformer at a sufficient reaction temperature (typically between 220 and 300°C). In order to compare the different types of energy (thermal, chemical, and electrical), an exergetic analysis is applied to the entire system, considering only the useful part of energy that can be converted to work. The effect of the solar radiation intensity and of different operational and geometrical parameters like the total inlet flow rate of methanol–water mixture, the size of the fuel cell, and the cell voltage on the performance of the entire system is investigated. The total exergetic efficiency comparing the electrical power output with the exergy input in form of chemical and solar exergy reaches values of up to 35%, while the exergetic efficiency only accounting for the conversion of chemical fuel to electricity (and neglecting the ‘cost-free’ solar input) is increased up to 59%. At the same time, an electrical power density per irradiated area of more than 920Wm−2 is obtained for a solar heat flux of 1000Wm−2. [Copyright &y& Elsevier]

• Laser direct synthesis and patterning (LDSP) is applicable for flexible electronics. • Thermocapillary yields concave surface profile of microline fabricated from LDSP. • A model is derived and validated to analyze the marangoni effect in LDSP. Laser direct synthesis and patterning technology (LDSP) is a promising way to realize flexible electronic circuitry. In LDSP, functional materials microstructure can be fabricated in-situ on flexible substrates using laser induced photo thermal reduction of ions from precursor that is free of nanoparticles. However, previous studies showed that concave curvature was found on the surface of developed LDSP micro-lines. This occurrence of concave curvature is contradictory to the convex structure expected from the temperature distribution of the precursor and on the substrate. Controlled surface morphology is crucially important for the fabrication of electronic circuitry with ultra-fine structure. Therefore, an analysis of the transport phenomena prevailing near the laser processing spot by both numerical simulation and experiment was carried out. The underlying physics behind the surface reconstruction of silver micro-lines fabricated by LDSP was investigated. The analysis included the opto-thermo-fluidic transport phenomena as well as thermo-capillary flow, i.e. the Marangoni effect. Results showed that the Marangoni effect dominated the movement kinetics on the interfacial surface between the ultra-thin silver nanocluster film and the surrounding fluid during the LDSP process. The surface morphology of the synthesized and deposited silver micro-line is therefore affected by the Marangoni effect. An empirical model was developed to determine the values of characteristic parameters for the Marangoni effect in the present case. The model was applied successfully to determine the micro-line surface morphology evolved during multiple laser scans in LDSP process with three different scanning speeds. Theoretical solution on the silver line thickness was compared with that obtained from the experiments, and the discrepancy was less than 12%. The results and analysis techniques developed provide insights to the coupled heat and mass transport phenomena with thermo-capillary effects, and can be used to improve the quality of microstructures fabricated by LDSP and similar technologies. [ABSTRACT FROM AUTHOR]

The Laser Direct Synthesis and Patterning (LDSP) technology has advantages in terms of processing time and cost compared to nanomaterials-based laser additive microfabrication processes. In LDSP, a scanning laser on the substrate surface induces chemical reactions in the reactive liquid solution and selectively deposits target material in a preselected pattern on the substrate. In this study, we experimentally investigated the effect of the processing parameters and type and concentration of the additive solvent on the properties and growth rate of the resulting metal film fabricated by this LDSP technology. It was shown that reactive metal ion solutions with substantial viscosity yield metal films with superior physical properties. A numerical analysis was also carried out the first time to investigate the coupled opto-thermo-fluidic transport phenomena and the effects on the metal film growth rate. To complete the simulation, the optical properties of the LDSP deposited metal film with a variety of thicknesses were measured. The characteristics of the temperature field and the thermally induced flow associated with the moving heat source are discussed. It was shown that the processing temperature range of the LDSP is from 330 to 390 K. A semi-empirical model for estimating the metal film growth rate using this process was developed based on these results. From the experimental and numerical results, it is seen that, owing to the increased reflectivity of the silver film as its thickness increases, the growth rate decreases gradually from about 40 nm at initial to 10 nm per laser scan after ten scans. This self-controlling effect of LDSP process controls the thickness and improves the uniformity of the fabricated metal film. The growth rate and resulting thickness of the metal film can also be regulated by adjustment of the processing parameters, and thus can be utilized for controllable additive nano/microfabrication.

This study presents a novel approach for the rapid fabrication of conductive nano/microscale metal structures on flexible polymer substrate (polyimide). Silver film is simultaneously synthesized and patterned on the polyimide substrate using an advanced continuous wave (CW) laser direct writing technology and a transparent, particle-free reactive silver ion ink. The location and shape of the resulting silver patterns are written by a laser beam from a digitally controlled micromirror array device. The silver patterns fabricated by this laser direct synthesis and patterning (LDSP) process exhibit the remarkably low electrical resistivity of 2.1 μΩ cm, which is compatible to the electrical resistivity of bulk silver. This novel LDSP process requires no vacuum chamber or photomasks, and the steps needed for preparation of the modified reactive silver ink are simple and straightforward. There is none of the complexity and instability associated with the synthesis of the nanoparticles that are encountered for the conventional laser direct writing technology which involves nanoparticle sintering process. This LDSP technology is an advanced method of nano/microscale selective metal patterning on flexible substrates that is fast and environmentally benign and shows potential as a feasible process for the roll-to-roll manufacturing of large area flexible electronic devices.