Research into sustainable energy sources has gained significant attention due to global environmental challenges. Vibration energy harvesting (VEH) presents a promising approach for developing self-powered sensors, offering both practical and environmental benefits. This paper reviews recent advancements in VEH with a specific focus on piezoelectric-based methods. It classifies the key techniques in the literature into categories such as multistability (including bistability), internal resonance, optimized designs, and frequency-up conversion. The paper discusses the underlying principles of each technique, provides relevant illustrations, highlights recent studies within each category, and summarizes their main contributions.

In the pursuit of sustainable solutions to the ever-increasing demand for renewable energy, mechanically compliant thermoelectric generators (TEGs) have garnered significant attention owing to the promise they present for application in generating power from waste heat in mechanically challenging scenarios. This review paper examines the ongoing advancements in the efficiency and applicability of TEGs through novel material engineering and design innovations. It delves into the improvement of their thermoelectric (TE) properties via micro- and nanostructural modifications and explores architectural advancements aimed at enhancing functionality and power output. Notably, the integration of TEGs into flexible, stretchable, and wearable electronics has been a significant development, expanding their applications in various domains such as healthcare monitoring, remote sensing, and consumer electronics. The review emphasizes the critical interplay between electronic, thermal, and mechanical aspects in optimizing TEGs performance. By providing an in-depth exploration of these multifaceted interactions and highlighting the significant advancements in materials and design, this review aims to underscore the importance of TEGs in a cleaner and more efficient era of energy generation, with a particular focus on their emerging applications across diverse fields.

Duplex stainless steels (DSSs) exhibit excellent corrosion resistance and are being used in a variety of industrial applications. Reducing/eliminating the amount of nickel in such alloys will contribute significantly to its economic viability. Moreover, a well-established wear behavior for these alloys is also an essential development in most of their applications. Hence, in this work, the Taguchi technique was effectively implemented to investigate the effect of operating factors such as sliding speed and applied load on the wear behavior of different compositions of nickel-free DSSs. It was observed that the composition had a higher contribution of 33.66% to the wear rate (WR) and the contribution of the sliding speed to the coefficient of friction (COF) was found to be 68.17%. With a good agreement, a regression model was also developed to predict the WR and COF within a certain range of factors. Wear tests have also shown that the developed nickel-free DSS is a promising candidate in terms of wear resistance as compared to austenitic stainless steels (ASS).

This paper has explored and analyzed new routes to design new concepts of materials capable of feeling external effects and feed information back to a monitor and/or react through embedded actuators to resist any deformation. The material with its new artificial sensing property can be easily scaled-up to govern a whole structure at macro scale. The research has investigated a variety of manufacturing routes to build prototypes to be tested for the sake of characterization and performance assessment as well as cost analysis to assess effectiveness. This has included ultrasonic fiber optics embedding in thin Metals e.g. Aluminum which has shown some challenges to be discussed. The host materials included mainly layered manufacturing based materials e.g. powder based materials (Alloy Al6061) and additive process e.g. 3D printing with ABS material. This work has considered samples with concepts having embedded fiber optics in 1D, 2D and 3D. The integrity of the fiber optics and the host materials as well as the sensors performance has been investigated under several conditions of pressure, temperature and geometric placement of the fiber optics. A parametric compromise between materials standard performance and integrity of the sensors is to be found.

The paper presents an investigation and analysis of the electromechanical and thermal characteristics of the carbon fiber alone as single tow and embedded in host materials such as polymer e.g., acrylonitrile butadiene styrene (ABS) using 3D printing. While carbon fibers can partially reinforce the structure, they can act as sensors to monitor the structural health of the host material. The piezo-resistive behavior was examined without any pretreatment of the carbon fiber under tensile test in both cases. Special focus on the filaments clamping types and their effects was observed. An auxetic behavior was exhibited; otherwise, the free part shows elastic and yielding ranges with break point at high resistance. An induced temperature of the carbon fiber was measured during the tensile test to show low variation. The carbon fiber can provide strength contribution to the host material depending on the percentage of filling the material in 3D printing. The relative variation of the electrical resistance increases by 400% while embedded in the host material, but decreases as the tows filament density increases from 1 to 12 K.