With the increase of interest in the application of piezoelectric polyvinylidene fluoride (PVDF) in nanogenerators (NGs), sensors, and microdevices, the most efficient and suitable methods of their synthesis are being pursued. Electrospinning is an effective method to prepare higher content β-phase PVDF nanofiber films without additional high voltage poling or mechanical stretching, and thus, it is considered an economically viable and relatively simple method. This work discusses the parameters affecting the preparation of the desired phase of the PVDF film with a higher electrical output. The design and selection of optimum preparation conditions such as solution concentration, solvents, the molecular weight of PVDF, and others lead to electrical properties and performance enhancement in the NG, sensor, and other applications. Additionally, the effect of the nanoparticle additives that showed efficient improvements in the PVDF films was discussed as well. For instance, additives of BaTiO3, carbon nanotubes, graphene, nanoclays, and others are summarized to show their contributions to the higher piezo response in the electrospun PVDF. The recently reported applications of electrospun PVDF films are also analyzed in this review paper.

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Currently, different metal sulfides (NiS, Co 9 S 8 , FeS 2 , and CuS) have been extensively studied as alternative electrodes for rechargeable batteries that can satisfy the performance requirements for more powerful energy supply and storage technologies for various applications and industries. Among them, copper sulfides have gained significant attention as a promising electrode material in rechargeable metal-ion (Li, Mg, Na, and Al) batteries. A wide range of synthesis routes and methods have been implemented in order to prepare various stoichiometry Cu x S (1 ≤ x ≤ 2) micro-/nanostructured materials with excellent electrochemical properties. Since the bulk microsized electrode materials have almost reached their performance limits for energy devices, the introduction of nanoscale Cu x S composites is now in high demand. This review focuses on the influence of the material morphology and dimensions on their performance in secondary batteries. The structures of Cu x S materials from zero-dimensional (0D) to 3D and their preparation are discussed. The primary purpose of this work is to provide an overview of the unique electrochemical and physical properties of particular structure and dimensionality which can promote these materials' application in the energy storage field. Along with this, this work summarizes the information on various synthesis strategies and how they can manage the morphologies of Cu x S micro-/nanocomposites. In the current fast technologically advancing society, the development of the most economically profitable and efficient synthesis routes is especially encouraged and required, and this aspect is also commented on in this review.

Harvesting abundant mechanical energy has been considered one of the promising technologies for developing autonomous self-powered active sensors, power units, and Internet-of-Things devices. Among various energy harvesting technologies, the triboelectric harvesters based on contact electrification have recently attracted much attention because of their advantages such as high performance, light weight, and simple design. Since the first triboelectric energy-harvesting device was reported, the continuous investigations for improving the output power have been carried out. This review article covers various methods proposed for the performance enhancement of triboelectric nanogenerators (TENGs), such as a triboelectric material selection, surface modification through the introduction of micro-/nano-patterns, and surface chemical functionalization, injecting charges, and their trapping. The main purpose of this work is to highlight and summarize recent advancements towards enhancing the TENG technology performance through implementing different approaches along with their potential applications. Graphic Abstract This paper presents a comprehensive review of the TENG technology and its factors affecting the output power as material selection, surface physical and chemical modification, charge injection, and trapping techniques.

Critical thinking extends to all aspects of professional engineering, especially in technical development, and, since the introduction of the ABET 2000 criteria, there has been an increased emphasis in engineering education on the development of critical thinking skills. What is hoped for is that the students obtain critical thinking skills to complement their abundant logical thinking skills. Critical thinking is a developmental skill that cannot be taught simply by traditional methods, i.e., step-by-step instruction followed by repetitive skills, as used for logical thinking skills. The research and development reported here is concerned with outlining how students first can be alerted to what critical thinking is, and how critical thinking can be nurtured through practical experience with appropriate guidance and reinforcement. The module 'Introduction to Fluid Mechanics' has been selected to demonstrate how formal critical thinking components may be introduced with the development of principles of logic and an obligatory problem solving procedure. A method of assessment during various phases of critical thinking, i.e., initial design or set-up, testing of method or prototype, and evaluation of the results, of open-ended assignments in engineering for each year of the undergraduate course has been developed.