Ferromagnetic nanoparticle-embedded hybrid nanogenerator for harvesting omnidirectional vibration energy

Recent Advances in Mechanical Vibration Energy Harvesters Based on Triboelectric Nanogenerators

With the development of autonomous/smart technologies and the Internet of Things (IoT), tremendous wireless sensor nodes (WSNs) are of great importance to realize intelligent mechanical engineering, which is significant in the industrial and social fields. However, current power supply methods, cable and battery for instance, face challenges such as layout difficulties, high cost, short life, and environmental pollution. Meanwhile, vibration is ubiquitous in machinery, vehicles, structures, etc., but has been regarded as an unwanted by-product and wasted in most cases. Therefore, it is crucial to harvest mechanical vibration energy to achieve in situ power supply for these WSNs. As a recent energy conversion technology, triboelectric nanogenerator (TENG) is particularly good at harvesting such broadband, weak, and irregular mechanical energy, which provides a feasible scheme for the power supply of WSNs. In this review, recent achievements of mechanical vibration energy harvesting (VEH) related to mechanical engineering based on TENG are systematically reviewed from the perspective of contact-separation (C-S) and freestanding modes. Finally, existing challenges and forthcoming development orientation of the VEH based on TENG are discussed in depth, which will be conducive to the future development of intelligent mechanical engineering in the era of IoT.

From Triboelectric Nanogenerator to Multifunctional Triboelectric Sensors: A Chemical Perspective toward the Interface Optimization and Device Integration

Triboelectric nanogenerators (TENGs) have intrigued scientists for their potential to alleviate the energy shortage crisis and facilitate self-powered sensors. Triboelectric interfaces containing triboelectric functionalized molecular groups and tunable surface charge densities are important for improving the electrical output capability of TENGs and the versatility of future electronics. In this review, following an introduction to the fundamental progress of TENG systems for mechanic energy harvesting, surface modifications that aim to increase the surface charge density and functionality are highlighted, with an emphasis on interfacial chemical modification and triboelectric energetics/dynamics optimization for efficient electrostatic induction and charge transfer. Recent advances in assemblies of multifunctional triboelectric sensing are briefly introduced, and future challenges and chemical perspectives in the field of TENG-based electronics are concisely reviewed. This review presents and advances the understanding of the state-of-the-art chemical strategies toward rational triboelectric interface engineering and system assembly and is expected to guide the rational design of highly efficient and versatile triboelectric sensing.

Switchless Oscillating Charge Pump-Based Triboelectric Nanogenerator and an Additional Electromagnetic Generator for Harvesting Vertical Vibration Energy

According to energy crisis and increasing number of small electronics, energy harvesting is one of the most promising technologies for scavenging several types of wasted energy. Especially, with regard to vibrational energy harvesting, triboelectric nanogenerators and electromagnetic generators stand out due to their working mechanisms. Here, an oscillating charge pump-based hybrid generator with two triboelectric nanogenerators and an electromagnetic generator using a switching-free characteristic was fabricated with material optimization. To enhance the electrical output of the triboelectric nanogenerator, a concept of charge pumping with simply connecting an additional charge pump device and the nanostructure formation process on the contact metal layer were adopted. The electrical outputs were characterized as an output current of 9.17 μA with a current density of 83.2 mA m-3 in the triboelectric nanogenerator. The power density of the triboelectric nanogenerator reached 4.45 W m-3 with a 40 MΩ resistor. The electromagnetic generator showed an output current density of 0.91 A m-2. Moreover, with the cuboid structure, the device can sense the collision force with different angular displacements from 5 to 30°. The proposed hybrid generator with a simple structure can be applied to sensing applications with the one-point-fixed state.

Forced Triboelectrification of Fine Powders in Particle Wall Collisions

Triboelectric separation as an inexpensive and environmentally friendly technique could contribute to material-specific sorting. However, the application as a widespread method is limited due to the complexity of the process. In particle wall collisions, various parameters like collision energy and angle, work function of the contact partners, humidity, surface roughness, etc. influence the particle charging in a hardly predictable way. This study investigates the possibilities of forced triboelectric particle charging by applying an electrical potential to the metal contact partner (copper/steel pipe). The variations included different pipe lengths (0.5 m–3 m), particle materials, and particle sizes for limestone. A distinction is made between the net charge of the particles and the positive, negative, and neutral mass fractions. The work functions of the investigated materials vary from about 3.2 eV to >8.5 eV for glass, limestone, artificial slag, and lithium aluminate particles. With the applied high-voltage potential, the particle net charge can be shifted linearly. For limestone, it is shown that the neutral fraction is highest at the Point of Zero Net Charge (PZNC). This observation may identify an approach for the material selective separation of one target component from a multi-material mixture.

Expecting the unexpected: high pressure crystallization significantly boosts up triboelectric outputs of microbial polyesters

Polyhydroxybutyrate (PHB) with special wrinkled spherulites enables significant improvement in triboelectric outputs of the microbial polyester.