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Summary: Nanogenerators is the growing technology that facilitates self‐powered systems, sensors, and flexible and portable electronics in the thriving era of internet of things (IoT). Since the first invention of the triboelectric nanogenerators (TENGs) in 2012, it has become one of the most important inventions in energy harvesting technologies. In this paper, a brief review on the recent progress of energy harvesting research based on TENGs technology is discussed. Basic working modes of the TENG are discussed in detail and the general procedure to synthesize, measure, and characterize a nanogenerator is presented in a direct structure. The triboelectric material choices are extremely important for TENGs since the triboelectric effects of the materials are fundamental for TENGs. The materials used as triboelectric layers are varied from polymers, metals, and inorganic materials with the commonly used materials are dielectric polymers such as PTFE, PVDF, PDMS, nylon, and Kapton. Recently, two‐dimensional (2D) materials have been widely reported as candidate materials for TENGs. Graphene, the most attractive 2D materials exhibits an excellent electrical property, great flexibility, and a high surface‐to‐volume ratio. Owing to the very low thickness of the atomic unit, a stacking graphene structure can be also made to form a very thin and miniature TENGs device. The major applications of the graphene as active materials for TENGs as a sustainable energy harvester are presented, following which structural designs and materials optimization for output performance improvement of the graphene‐based TENGs are summarized. Finally, the future directions and perspectives of the graphene‐based TENGs are outlined. The graphene‐based TENGs is not only a sustainable micro‐power source for small devices, but also serves as a potential macro‐scale generator of power from blue energy in the future. [ABSTRACT FROM AUTHOR]

Summary: Thermal interface materials (TIMs) are applied in electronic devices that are involved in heat generation and raising the temperature. The optimization of TIMs is important in heat dissipation to maintain the good performance of devices, low power during operation, and reduced internal damages among small components. The TIMs are inserted between two contact surfaces to enhance thermal conductivity that will reduce the increment of surface temperature in a longer time and facilitates the cooling process with a consistent power supplied to the system with minimum increment. Research on nanomaterials and hybrid materials aims to obtain maximum thermal conductivity and reduce resistance in the devices. However, the suitable fabrication method for achieving good production and performance is still debatable. Therefore, significant fabrication methods have been explored for various materials. This review provides insights into the current work focusing on the materials used in the development of TIMs by various methods. The discussion begins with the introduction of thermal management and the working principles applied in the system. Then, the methods applied for material fabrication into TIMs, including the advantages and disadvantages of the methods, are discussed. Last, the current challenges and opportunities in methods used are discussed to offer new inputs and improvement in method modification for TIMs design. The targeted thermal performance for the industrial market of TIMs for nanomaterial applications is approximately 100 W/mK and 1 × 10−6 m2/WK with lowest power of 100 W. [ABSTRACT FROM AUTHOR]

Multi-step chemical vapor deposition (CVD) is a synthesis method which is capable of producing a uniform, large area, and high-quality thin films. In this work, we report the effect of post-annealing on the structural and optical properties of few-layers (FL) MoS2 thin films synthesized by multi-step CVD. Based on atomic force microscopic image, the thickness of the MoS2 thin film is ∼3 nm, which is equivalent to five layers. After annealing at 900°C for 17 min, intensity of the A1g and E 2 g 1 full-width-at-half-maximum (FWHM) Raman modes increased by ∼3 times while the reduced from ∼10 cm−1 to ∼7.5 cm−1 for A1g and from ∼13.6 cm−1 to ∼7.5 cm−1 for E 2 g 1 . Both of the as-grown and annealed samples showed X-ray (002) diffraction peak at 14.2° but the intensity was more prominent for the annealed sample. It was found that the annealed sample showed clear and distinct absorbance peaks at 666, 615, 448, 401, and 278 nm which correspond to the A, B, C, D, and E excitons, respectively. The results indicate that annealing significantly improved the optical and structural quality of the MoS2 film. Field-effect transistor based on annealed MoS2 thin film was fabricated and showed electron mobility of 0.21 cm2V−1s−1, on/off ratio of 1.3 × 102 and a threshold voltage of 0.72 V. Our work highlights the importance of high-temperature annealing in multi-step CVD to obtain a uniform and high-quality FL MoS2 thin films. [ABSTRACT FROM AUTHOR]

Summary: The performance of electronic devices, mostly in medical applications, has been investigated to determine whether they meet the requirements of healthcare monitoring and patient's satisfaction. Mobile health monitoring is preferable at present given the current innovations in handheld, wearable, and implantable devices. However, these applications require appropriate thermal management because they are attached directly to the human body and operate for a long period. Moreover, a sophisticated design with functional mobility necessitates proper thermal circulation during the process. This review provides the current research direction for cooling systems, the thermal working principle of wearable and implantable devices, and its implementation on design architecture. Then, the importance of internal and external functional properties in thermal management and their effects on device performance are discussed. Operating temperature is among the most important elements in monitoring thermal performance due to the tendency of tissue and component damages to occur after an increment of only 1°C or 2°C in temperature. Challenges and available solutions for thermal management are listed in detail to improve cooling methods and service to the healthcare field. [ABSTRACT FROM AUTHOR]

This study reports the performances of a single structured light-emitting diode (LED) devices based on polymer material poly(9,9-di- n -hexylfluorenyl-2,7-diyl) (PHF) mixed with various concentrations of perovskite oxide strontium titanate (SrTiO3) particles deposited as a composite PHF: SrTiO3 emitting layer. The performances of the single structured organic LED indium tin oxide (ITO)/PHF/aluminum (Al) device and the composite LED ITO/PHF: SrTiO3/Al devices were compared in terms of turn-on voltage and luminance intensity. By incorporating perovskite SrTiO3 particles into PHF emitting layer, the turn-on voltage of the device is significantly reduced from 11.25 V to 1.80 V and the luminance intensity increased from 57.7 cd/m2 to 609 cd/m2. The improvement of turn-on voltage and the electroluminescence spectrum of the composite devices were found to be dependent on the weight ratios of SrTiO3 content in the PHF emitting layer. [ABSTRACT FROM AUTHOR]

Kretschmann-based surface plasmon resonance sensor utilizing chromium and gold nanofilms is ideal for label-free biomedical sensing. In this work, Taguchi's L9 orthogonal array method was used to optimize the effects of three control factors and noise factor, which are the incident optical wavelength, chromium and gold nanofilm thicknesses, and their root-mean-square surface roughness, on the performance of the Kretschmann-based surface plasmon resonance sensor. The control factors were varied at three levels for a novel multi-response optimization of the Kretschmann-based surface plasmon resonance sensor for the minimum reflectivity, the full-width-at-half-maximum, and the sensitivity of 3% glucose detection, executed using Lumerical's two-dimensional finite-difference time-domain method. Using Taguchi method, the best control factor setting in air was A3B2C2 corresponding to 785 nm optical wavelength, 0.5 nm chromium, and 50 nm gold layer thickness, respectively, with minimum reflectivity of 0.0017%, full-width-at-half-maximum of 0.4759°, and glucose-sensing sensitivity of 106.73°·RIU−1. The detection accuracy and quality factor were 0.01 and 224.26 RIU−1, respectively. It was also indicated that chromium nanofilm thickness of 0.5–3 nm and its root-mean-square surface roughness has a negligible factor effect compared to other control factors. Taguchi method's factor effect analysis showed that for chromium layer thickness of 1–3 nm, the minimum reflectivity values are predominantly determined by the gold layer thickness with 75% factor effect, followed by optical wavelength with 11%. Factor effect of full-width-at-half-maximum is determined by optical wavelength (57%), followed by gold layer thickness (38%). Sensitivity is 88% determined by optical wavelength and 10% determined by gold layer thickness. The Kretschmann-based surface plasmon resonance glucose sensor with the best glucose-sensing sensitivity was at optical wavelength of 632.8 nm with a higher sensitivity value of 163.415°·RIU−1 but lower detection accuracy and quality factor values of 0.001 and 24.86 RIU−1, respectively, compared to near-infrared wavelength of 785 nm. In conclusion, finite-difference time-domain and Taguchi method is suitable for multi-response optimization of control and noise factors of Kretschmann-based surface plasmon resonance sensors. [ABSTRACT FROM AUTHOR]

Summary: The performance of allotrope carbon materials has been explored because of their superior properties in energy system applications. This review provides an understanding of the current work focusing on the applications of selected carbon materials in important energy systems, focus on thermal interface materials (TIMs), and fuel cell applications. This article begins with the introduction of TIMs and fuel cell in general working principle and presents details on carbon materials. The discussion focuses on updates from the latest research work and addresses current challenges and opportunities for research toward TIMs and fuel cell applications. The optimum performance of TIMs was seen when thermal conductivity achieved at a maximum of 3000 W (m K)−1 by using vertically aligned carbon nanotubes (CNTs) and a minimum internal thermal resistance of 0.3 mm2 K W−1. Meanwhile for fuel cell, the platinum/CNTs catalyst applied proton exchange membrane fuel cell achieved high power density of 661 mW cm−2 in the presence of Nafion electrolyte membrane. This review provides insights for scientists about the use of carbon materials, especially in energy system applications. [ABSTRACT FROM AUTHOR]