Nonlinear Oscillations: Exact Solutions and their Approximations

https://northumbria-test.eprints-hosting.org/id/document/270135

Origami-inspired electret-based triboelectric generator for biomechanical and ocean wave energy harvesting

With the rapid development of the Internet of Things (IoT), the number of sensors utilized for the IoT is expected to exceed 200 billion by 2025. Thus, sustainable energy supplies without the recharging and replacement of the charge storage device have become increasingly important. Among various energy harvesters, the triboelectric nanogenerator (TENG) has attracted considerable attention due to its high instantaneous output power, broad selection of available materials, eco-friendly and inexpensive fabrication process, and various working modes customized for target applications. The TENG harvests electrical energy from wasted mechanical energy in the ambient environment. Three types of operational modes based on contact-separation, sliding, and freestanding are reviewed for two different configurations with a double-electrode and a single-electrode structure in the TENGs. Various charge transfer mechanisms to explain the operational principles of TENGs during triboelectrification are also reviewed for electron, ion, and material transfers. Thereafter, diverse methodologies to enhance the output power considering the energy harvesting efficiency and energy transferring efficiency are surveyed. Moreover, approaches involving not only energy harvesting by a TENG but also energy storage by a charge storage device are also reviewed. Finally, a variety of applications with TENGs are introduced. This review can help to advance TENGs for use in self-powered sensors, energy harvesters, and other systems. It can also contribute to assisting with more comprehensive and rational designs of TENGs for various applications.

Triboelectric Nanogenerator: Structure, Mechanism, and Applications.

Wearable triboelectric nanogenerators for biomechanical energy harvesting

The triboelectric nanogenerator (TENG) is a new type of energy generator first demonstrated in 2012. TENGs have shown potential as power sources for electronic devices and as sensors for detecting mechanical and chemical stimuli. To date, studies on TENGs have focused primarily on optimizing the systems and circuit designs or exploring possible applications. Even though triboelectricity is highly related to the material properties, studies on materials and material designs have been relatively less investigated. This review article introduces recent progress in TENGs, by focusing on materials and material designs to improve the electrical output and sensing performance. This article discusses the current technological issues and the future challenges in materials for TENG. The development of materials for a technology that uses the movement of the human body to provide power has been reviewed by scientists in South Korea. A triboelectric nanogenerator converts mechanical energy into electricity by harnessing the fact that two surfaces rubbing against one another can become electrically charged. This is known as the triboelectric effect. One exciting use for these nanogenerators is in wearable electronics, where the motion of the body provides the power. Unyong Jeong and colleagues from Pohang University of Science and Technology have reviewed recent progress in material advances in the four main elements of a triboelectric nanogenerator: the charge-generating layer, the charge-trapping layer, the charge-collecting layer, and the charge-storage layer. These improvements all aim to increase the electrical output of such devices. Over the last decade, triboelectric nanogenerator (TENG) has been verified to be an effective way of converting daily mechanical energy into electric power or detecting various stimuli in the external environment. To promote the material researches in TENG, we introduce recent progresses in materials and material designs to improve the power generation and sensing performance. Also, we discuss on the future challenges and suggest possible approaches to solve the challenges.

/pdf/material-aspects-of-triboelectric-energy-generation-and-2j8tumglpy.pdf

Material aspects of triboelectric energy generation and sensors

Mechanical oscillators employing varying capacitance scheme for the transduction of the motion are significantly limited by the effects of capacitive feedthrough. This work focuses on revealing the nature of feedthrough parasitic dominated resonance and demonstrating a phase-controlled oscillation technique for operating microresonators beyond the nonlinear regime with on-chip feedthrough effect (FE) de-embedding. Our method imposes hybrid control on the phase offset of the resonant motion and electromechanical coupling of the transducers to enable the isolation of the FE in the nonlinear bifurcation points. The strategies of the on-chip FE control in our capacitive platform can be suitably transformed for the use in feedthrough parasitic dominated systems using alternative transduction principles as well.

Phase-Controlled Oscillation in a Capacitive Nonlinear Ring Resonator with On-Chip Feedthrough De-Embedding

This paper reports experimental results demonstrating significant gains in frequency stability for bulk acoustic wave (BAW) silicon disk resonator oscillators due to the locking of degenerate modes. The results show that when two degenerate modes are locked, the minimum Allan deviation is improved by a factor of more than two times in comparison with the minimum Allan deviation for oscillators locked to the individual degenerate modes. A shortterm stability of 48.3 μHz (51 ppt @ 0.27 s integration time) is recorded for a MEMS oscillator with an output of ~1 MHz which benchmarks favourably relative to the MEMS oscillator state-of-the-art and commercial crystal oscillators. The approach is applicable to the locking of oscillators based on degenerate modes generally and can be scaled to higher frequency axisymmetric resonators with the higher-order bulk modes also providing inherent immunity to shock and vibration.

Enhancement of Frequency Stability in Injection Locked Bulk Mode MEMS Oscillators

General analysis and optimization of a two-stage power management circuit for electrostatic/triboelectric nanogenerators

In this paper, nonlinear modal interactions in a micromachined disk resonator with 2:1 internal resonance are demonstrated. By means of the multiple scales method, two types of transition from stable to unstable behavior including jump phenomena and modulated motion corresponding to M-shaped responses are explained in a coupled nonlinear system dominated by quadratic nonlinearity. At the same time, these exotic responses and stability under different driving forces and the strength of internal resonance are also investigated. Furthermore, the frequency and amplitude stability and signal-to-noise ratio (SNR) can be improved under this condition.

Nonlinear Modal Interactions and Internal Resonance in a Micromachined Disk Resonator

This paper reports a self-sustained thermal-actuation piezoresistive-detection oscillator with boosted startup time and quality (Q) factor in the order of a million. A high Q-factor is an essential property for resonant sensors to achieve a high signal to noise ratio. It is demonstrated that the thermal-piezoresistive effect can increase the Q-factor. We obtained an effective Q-factor up to 1.06 million operating in air with direct-current induced self-oscillation. Furthermore, a fast startup time is achieved when stimulating the self-sustained oscillator with a current just below the threshold of self-oscillation requirements. The experimental results show that the startup time can be decreased by a factor of ~3 by initially thermally pre-expanding the actuating nanobeam compared to a cold-startup condition.

Hemin Zhang

Papers

Phase-Controlled Oscillation in a Capacitive Nonlinear Ring Resonator with On-Chip Feedthrough De-Embedding

Enhancement of Frequency Stability in Injection Locked Bulk Mode MEMS Oscillators

General analysis and optimization of a two-stage power management circuit for electrostatic/triboelectric nanogenerators

Nonlinear Modal Interactions and Internal Resonance in a Micromachined Disk Resonator

A Fast-Startup Self-Sustained Thermal-Piezoresistive Oscillaror with >106 Effective Quality Factor In The Air