A high-performance magneto-mechano-triboelectric nanogenerator (MMTEG) was demonstrated by introducing accelerated water-soluble nano-bullet modified nanostructures to convert a gentle magnetic field into electric energy for powering an indoor wireless positioning system. NaCl salt nanoparticles were accelerated by an aerosol deposition (AD) process to collide on a perfluoroalkoxy (PFA) film with a high kinetic energy for the formation of a complicated nanomorphology on the triboelectric active surface. Under an alternating current (AC) magnetic field of 7 Oe, the MMTEG generated an open-circuit peak-to-peak voltage (V_pp) and a short-circuit current of 708 V and 277 μA, respectively. The harvesting device also presented a maximum peak power of 21.8 mW as well as a continuous AC output power of 4.8 mW (4.8 mJ per second). A self-powered indoor IoT positioning system was constructed by integrating the MMTEG, a power managing circuit, a storage element, and an IoT Bluetooth beacon. The electric energy from the MMTEG device enabled continuous operation of a beacon device, and we successfully confirmed the accurate location of the installed wireless positioning system, subsequently resulting in transmission of our indoor position to the main monitoring computer. Lastly, the MMTEG generated an open-circuit V_pp and a short-circuit current of 330 V and 23 μA, respectively, near a 60 Hz power cable connected to home appliances, which were large enough to turn on 108 blue light emitting diodes (LEDs).

Materials offering high energy density are currently desired to meet the increasing demand for energy storage applications, such as pulsed power devices, electric vehicles, high-frequency inverters, and so on. Particularly, ceramic-based dielectric materials have received significant attention for energy storage capacitor applications due to their outstanding properties of high power density, fast charge–discharge capabilities, and excellent temperature stability relative to batteries, electrochemical capacitors, and dielectric polymers. In this paper, we present fundamental concepts for energy storage in dielectrics, key parameters, and influence factors to enhance the energy storage performance, and we also summarize the recent progress of dielectrics, such as bulk ceramics (linear dielectrics, ferroelectrics, relaxor ferroelectrics, and anti-ferroelectrics), ceramic films, and multilayer ceramic capacitors. In addition, various strategies, such as chemical modification, grain refinement/microstructure, defect engineering, phase, local structure, domain evolution, layer thickness, stability, and electrical homogeneity, are focused on the structure–property relationship on the multiscale, which has been thoroughly addressed. Moreover, this review addresses the challenges and opportunities for future dielectric materials in energy storage capacitor applications. Overall, this review provides readers with a deeper understanding of the chemical composition, physical properties, and energy storage performance in this field of energy storage ceramic materials.

A magneto-mechano-electric (MME) generator comprising a cantilever structured magnetoelectric (ME) composite having a magnet-proof mass is an ideal candidate for powering autonomous Internet of Things (IoT) sensor networks by scavenging electric energy from ambient magnetic noise. However, charging an energy storage device in a short time using an MME generator from low-intensity magnetic noise flux spreading in radial directions, e.g., around power cables, requires the generator volume to be enlarged. Here, we demonstrated a novel method to enhance the output power of the given MME generator by concentrating a magnetic flux around the circumference of an MME generator structure using a magnetic flux concentrator (MFC) fabricated from a high-permeability magnetic material. The output power of the MME generator was significantly enhanced by optimizing the MFC structure in terms of its shape, aspect ratio, magnetic permeability, and the number of layers, both through finite element analysis and experiments. The MME generator with the MFC was observed to generate a maximum power of 3.33 mW, which was 285% of that of the condition without the MFC (1.17 mW) under a weak magnetic field of 8 Oe (= 8 G = 800 μT in air), which was sufficient to charge the 2.2 mF storage capacitor within 13 s and continuously operate an IoT sensor for a long period. The stored energy is also sufficient enough to turn on 100 blue LEDs with high intensity. Furthermore, we demonstrated a realistic practical application by installing the self-powered wireless environmental monitoring module consisting of the MME generator with the MFC at a power substation, which successfully scavenges the power from the magnetic fields around the power cables and continuously operates a temperature wireless sensor. These results indicated that the MFC has great potential to enhance the performance of an MME generator as the power source of standalone IoT sensors without enlarging the MME generator.

With the expansion of Internet of Things (IoT) and sensor network systems, transparent and flexible energy supply devices are becoming more vital for ultra-connected and highly convenient human interfaces. In particular, the mechanical energy harvesting technology using piezoelectric materials is very attractive due to the ability of direct energy conversion from wasted mechanical energy to useful electrical energy. In this work, we demonstrate a highly transparent and flexible piezoelectric energy harvester (f-PEH) using a metallic nanowire-percolated piezoelectric copolymer on a flexible plastic substrate. The silver nanowire (Ag NWs)-based conductor has been considered as a powerful future electrode material with high transparency and flexibility, while poly(vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) is a representative high-performance piezoelectric polymer material. Based on these two attractive materials, the proposed transparent f-PEH generated an output voltage, current, and power of ∼17 V, ∼2.5 μA, and ∼12 μW, respectively, which are a record-high performance compared to previously reported transparent f-PEHs. Besides material and device characterizations, a multiphysics simulation was firmly investigated to clarify the properties of the transparent f-PEH devices. Finally, the transparent f-PEH devices were directly modified and used as a self-powered pressure sensor array (5 × 5), which well detected the pattern images of the external pressure input without serious cross-talk. This work can guide the field of transparent and flexible piezoelectric devices to the way to accomplish transparent self-powered electronics for high-performance applications.

A fully-flexible magnetoelectric (ME) composite with 2-2 type structure is developed by adopting CoFe₂O₄ nanofiber-based magnetostrictive film and piezoelectric P(VDF-TrFE) and using simple electrospinning and spin-coating process.