Renewable energy harvesting technologies, which convert ambient resources such as wind into electrical energy, have attracted significant attention as sustainable power sources for self-powered systems. However, the long-term applicability of wind energy harvesters in remote or extreme environments has not yet been fully discussed, particularly in terms of structural robustness and environmental adaptability. In this study, we designed a double-clamped flutter-type triboelectric generator (DFTEG) for efficient wind energy harvesting and evaluated its output performance under various simulated outdoor conditions. The DFTEG features a modular acrylic frame with a magnet-based assembly for easy maintenance and film replacement, utilizing PTFE films and aluminum electrodes to maximize the charge density difference according to the triboelectric series. Structural optimization revealed that a single-film configuration with a length of 110 mm produced the most stable flutter vibration and a large effective contact area, achieving a maximum open-circuit voltage of 42.28 V and a short-circuit current of 2.89 μA. Furthermore, performance evaluations under various environmental variables, including relative humidity, temperature, and sand particles interference, confirmed consistent electrical output across diverse environmental conditions. These results demonstrate the potential of the proposed DFTEG as an environmentadaptive independent power source capable of stable operation under complex environmental factors.

Metamaterials, as artificially engineered structures with unconventional mechanical and acoustic properties, have recently emerged as a transformative platform for enhancing the capabilities of triboelectric nanogenerator (TENG) systems. Since the invention of TENG devices, extensive efforts have been devoted to improving charge density, output stability, and overall performance. Conventional performance optimization strategies mainly rely on device-level improvements such as surface chemistry modification, microstructuring, and nanopatterning. However, limited emphasis has been given to system-level development of smart self-powered intelligent systems. The integration of metamaterials into TENG devices opens a new era by enabling frequency-selective localization, mechanical impedance matching, and controllable deformation pathways. These engineered mechanical structures not only improve energy harvesting efficiency but also introduce new functionalities into the system. This review systematically summarizes recent advances in metamaterial-integrated TENG systems across four major application domains: (i) energy harvesting, (ii) acoustic telecommunication and acoustic-to-electric conversion, (iii) self-powered sensing, and (iv) vibration suppression and monitoring. Overall, the integration of metamaterials into TENG systems will pave the way for next-generation sustainable, intelligent, self-powered devices with diverse functionalities.

Porous polymeric structures with piezoelectric properties have attracted considerable attention in the fields of biomaterials and tissue engineering due to their ability to convert mechanical stimuli into electrical signals. However, conventional fabrication methods for porous structures often face limitations in controlling pore architecture, maintaining structural uniformity, and achieving process reproducibility, in addition to requiring complex processing conditions. To address these issues, we propose a facile and reproducible fabrication method for porous poly (vinylidene fluoride) (PVDF) piezoelectric sponges using molded sugar cubes as sacrificial pore templates. By adjusting the particle size of the sugar templates, the pore size and distribution of the sponges could be effectively controlled, and a uniform open-pore network was achieved. The fabricated sponges were evaluated with a focus on pore morphology, mechanical behavior, and piezoelectric performance depending on the sugar particle size, and these evaluations confirmed the structural properties and functional efficacy. This study presents a simple and reproducible fabrication strategy along with a quantitative analysis method for porous structures, which is expected to enhance process accessibility and practical applicability in the development of piezoelectric polymer-based biomaterial platforms.

Piezoelectricity refers to the phenomenon where mechanical stress is converted into electrical signals or, conversely, electrical signals are converted into mechanical stress. Ferroelectric materials, characterized by high dielectric permittivity and spontaneous polarization, retain their polarization even after the removal of an electric field. In such materials, poling plays a crucial role in enhancing the piezoelectric effect, with the process of aligning dipoles being known as poling. This review focuses on studies that have compared and analyzed the enhancement of piezoelectric properties in ceramics and polymers through two representative poling methods: AC poling (ACP) and DC poling (DCP). Even within the same category of ceramics or polymers, variations in piezoelectric properties are observed based on the material type, poling method, and poling conditions. Under certain conditions, ACP has been shown to provide superior poling effects compared to DCP. Through this review, we propose that ACP has the potential not only to replace the traditionally used DCP in the poling of piezoelectric materials but also to serve as a more effective method. This could spark increased interest in the study of poling methods for piezoelectric polymers, a field that has received relatively less attention.

Triboelectric devices are attracting attention from researchers as self-powered electronic systems that can instantly convert mechanical input into electrical energy output. To improve triboelectric energy harvesting performance, increasing the number of contacts as well as the contact area has been carried out by numerous researchers. In this study, we design a shaker-type energy harvester which is called as maracas triboelectric generator (M-TEG), inspired by the structure of maracas, one of the musical percussion instruments. A tripod frame is inserted to the inside of a cylindrical case, which is a device with the electrodes of aluminum and copper. Then, the triboelectric energy harvesting characteristics between polypropylene (PP) balls and the electrodes are measured. The M-TEG with the frame generates the energy harvesting signals up to ~100 V and ~2.5 μA due to larger contact area and numbers, which enhances the voltage and current output by 250% and 610% compared to that without the frame, respectively. This study presents the feasibility of self-powered sensors and toys using improved triboelectric energy performance with a low-cost and simple manufacturing process in the interesting structure.

Morphotropic phase boundary (MPB), which is a special boundary that separates two or multiple different phases in the phase diagram of some ferroelectric ceramics, is an important concept in identifying physics that includes piezoelectric responses. MPB, which had not been discovered in organic materials until recently, was discovered in poly(vinylidene fluoride-co- trifluoroethylene (P(VDF-TrFE)), resulting from a molecular approach. The piezoelectric coefficient of P(VDF-TrFE) in this MPB region was achieved up to -63.5 pC N^-1, which is about two times as large as the conventional value of -30 pC N^-1 of P(VDF-TrFE). An order-disorder arrangement greatly affects the rise of the piezoelectric effect and the ferroelectric, paraelectric and relaxor ferroelectric of P(VDF-TrFE), so the arrangement and shape of the polymer chain is important. In this review, we investigate the origin of negative longitudinal piezoelectric coefficients of piezoelectric polymers, which is definitely opposite to those of common piezoelectric ceramics. In addition to the mainly discussed issue about MPB behaviors of ferroelectric polymers, we also introduce the consideration about polymer chirality resulting in relaxor ferroelectric properties. When the physics of ferroelectric polymers is unveiled, we can improve the piezoelectric and pyroelectric properties of ferroelectric polymers and contribute to the development of next-generation sensor, energy, transducer and actuator applications.