A Liquid-Metal-Based Freestanding Triboelectric Generator for Low-Frequency and Multidirectional Vibration

There are a lot of vibrational energies, which are low frequency, multidirectional, and broadband, in the nature. This creates difficulties for devices that aim at harvesting vibration energy. Here, we present a liquid-metal-based freestanding triboelectric generator (LM-FTG) for vibration energy harvesting. In this device, the fluidity of liquid is used to increase sensitivity to vibration for better low-frequency response and multidirectional vibration energy harvesting capability. The freestanding power generation mode is able to increase power generation stability. Experiments show that the bandwidth of LM-FTG can almost cover the entire sweep frequency range, and a 10 μF capacitor can be charged to 6.46 V at 7.5 Hz in 60 s by LM-FTG. In particular, 100 LEDs are illuminated in the low-frequency environmental experiment successfully. The proposed LM-FTG can work in low frequency with large working bandwidth, which provides an effective method for energy harvesting of low-frequency and multidirectional vibrations.

Enhancing the Triboelectric Nanogenerator Output by Micro Plasma Generation in a Micro-Cracked Surface Structure

Energy harvesting, especially for powering low-power internet-of-things (IoT) devices, is gaining attention in recent years. Triboelectric nanogenerators have been studied to improve the output by applying a structure that can concentrate electrons on the surface of the generator materials. For enhancing the triboelectrification output, we herein focused on the power output line. A method for increasing the amount of electrons on the power lead by potential difference and their acceleration was studied. A rod was shaken by external vibrations; the accumulated charges were discharged in a manner similar to that of a lightning rod. Micro plasma was generated when the rod made contact with the mating micro-cracked surface innumerable times. The micro-cracked surface was fabricated with a diamond tip moving horizontally to the surface. As the resistance of the micro plasma was close to zero, the amount of electron movement was instantaneously accelerated. This type of triboelectric generator can be fabricated in the form of an electric box. By using this triboelectric power amplifier, voltage can be amplified 2 to 3 times, and the current can be amplified 10 to 15 times; thus, enhanced energy harvesting efficiency is attained.

Performance Enhancement of Flexible Polymer Triboelectric Generator through Polarization of the Embedded Ferroelectric Polymer Layer

In this work, we report on a flexible triboelectric generator (TEG) with a multilayer polymer structure, consisting of a poly(vinylidene fluoride-co-trifluoroethylene) (PVDF-TrFE) layer sandwiched by polydimethylsiloxane (PDMS) layers for the performance enhancement of TEGs. We confirmed that the output performance of the TEG is closely dependent on the structure and polarization direction of the PVDF-TrFE layer. In addition, the PDMS layer serves as the electron trapping layer and suppresses the discharging of the surface charges, boosting the output performance. Furthermore, the polarized PVDF-TrFE layer in the preferred direction contributes to increasing the surface potential during the contact–separation motion. The interaction between these two polymer layers synergistically leads to the boosted output performance of TEGs. Specifically, the maximum peak-to-peak output voltage and current density of 420 V and 50 μA/cm2 generated by the proposed architecture, representing approximately a fivefold improvement compared with the TEG with a single layer, even though the same friction layers were used for contact electrification.