Xi Liang

Bio: Xi Liang is an academic researcher from Chinese Academy of Sciences. The author has contributed to research in topics: Triboelectric effect & Nanogenerator. The author has an hindex of 12, co-authored 19 publications receiving 630 citations.

Spherical triboelectric nanogenerator integrated with power management module for harvesting multidirectional water wave energy

Abstract: With the increasing deterioration of the natural environment, exploiting clean and renewable energy has become the top priority of scientific research today. One of the most prospective routes is to harvest water wave energy using triboelectric nanogenerator (TENG). In this work, a spherical TENG based on spring-assisted multilayered structure was fabricated to collect multidirectional water wave energy, and a power management module (PMM) was integrated to manage the output energy. The output performance of the TENG device was found to be controlled by the water wave frequency, amplitude, and orientation angle between the triggering direction and middle plane. Furthermore, with the PMM, the spherical TENG could output a steady direct current (DC) voltage on a resistance, and the charging speed to a supercapacitor was improved by 100 times. The power-managed performance of the whole TENG was also influenced by the circuit connection configurations among multilayered TENGs. A digital thermometer and a water level detection/alarm system were successfully driven by the power-managed TENG as the demonstrated applications. This work not only provides a type of spherical TENG capable of harvesting multidirectional water wave energy, but also effectively manages the output energy for practical applications toward blue energy. Our study demonstrates a typical example of how to build a self-charging power pack that can effectively use random energy in a regulated manner.

Triboelectric Nanogenerator Networks Integrated with Power Management Module for Water Wave Energy Harvesting

Abstract: Ocean waves are one of the most promising renewable energy sources for large-scope applications. Recently, triboelectric nanogenerator (TENG) network has been demonstrated to effectively harvest water wave energy possibly toward large-scale blue energy. However, the absence of effective power management severely restricts the practicability of TENGs. In this work, a hexagonal TENG network consisting of spherical TENG units based on springassisted multilayered structure, integrated with a power management module (PMM), is constructed for harvesting water wave energy. The output performance of the TENG network is found to be determined by water wave frequencies and amplitudes, as well as the wave type. Moreover, with the implemented PMM, the TENG network could output a steady and continuous direct current (DC) voltage on the load resistance, and the stored energy is dramatically improved by up to 96 times for charging a capacitor. The TENG network integrated with the PMM is also applied to effectively power a digital thermo meter and a wireless transmitter. The thermometer can constantly measure the water temperature with the water wave motions, and the transmitter can send signals that enable an alarm to go off once every 10 s. This study extends the application of the power management module in the water wave energy harvesting.

Robust Swing‐Structured Triboelectric Nanogenerator for Efficient Blue Energy Harvesting

Abstract: With a rapid development of the world economy, energy has been playing the most critical role. Massive consumption of fossil fuels has brought increasing threats of energy crisis and environmental deterioration,[1,2] driving people to search for new energy sources urgently from our environment. Ocean waves are one of the most desirable clean and renewable energy sources for large-scope applications, with superior advantages of abundant reserve and little dependence on ambient environment conditions.[3,4] However, such energy has rarely been exploited due to the lack of effective technology for energy scavenging.[5,6] Usually ocean waves exhibit at a rather low frequency, so that the dominated technology of electromagnetic generator (EMG) is inapplicable owing to the very low efficiency.[7,8] Considering that the EMG faces huge challenges of high cost, easily corroded, and low efficiency at low frequency, to develop a cost-effective, lightweight, and highly efficient technology is of great practical value for water wave energy harvesting. Triboelectric nanogenerator (TENG, also called as Wang generator) has been invented as a promising technology for converting ambient mechanical energy into electricity, by coupling the triboelectrification[9,10] and electrostatic induction.[11] The TENG technology, which adopts an underlying mechanism of Maxwell’s displacement current,[12–14] has been applied to harvest energy from a variety of sources, with unique merits of high power density, high efficiency, and low fabrication cost.[15–17] Due to its distinct mechanism, the TENG generates higher performance than the EMG at low frequency,[18] implying a possible killer application for low frequency energy harvesting, such as the mostly ultra-low frequency ocean wave energy. So far, various TENG prototypes have been designed to effectively harvest water wave energy,[19–32] proving the huge potential toward large-scale blue energy harvesting.[33,34] However, most of the demonstrated TENG devices have the oscillatory frequency close to the water wave triggering frequency. The very low frequency of water waves induces the TENG to generate low frequency outputs, resulting in low average output performance. The main problem is the lack of the structural design Ocean wave energy is a promising renewable energy source, but harvesting such irregular, “random,” and mostly ultra-low frequency energies is rather challenging due to technological limitations. Triboelectric nanogenerators (TENGs) provide a potential efficient technology for scavenging ocean wave energy. Here, a robust swing-structured triboelectric nanogenerator (SSTENG) with high energy conversion efficiency for ultra-low frequency water wave energy harvesting is reported. The swing structure inside the cylindrical TENG greatly elongates its operation time, accompanied with multiplied output frequency. The design of the air gap and flexible dielectric brushes enable mininized frictional resistance and sustainable triboelectric charges, leading to enhanced robustness and durability. The TENG performance is controlled by external triggering conditions, with a long swing time of 88 s and a high energy conversion efficiency, as well as undiminished performance after continuous triggering for 4 00 000 cycles. Furthermore, the SS-TENG is demon strated to effectively harvest water wave energy. Portable electronic devices are successfully powered for self-powered sensing and environment monitoring. Due to the excellent performance of the distinctive mechanism and structure, the SS-TENG in this work provides a good candidate for harvesting blue energy on a large scale.

Spherical Triboelectric Nanogenerators Based on Spring‐Assisted Multilayered Structure for Efficient Water Wave Energy Harvesting

Abstract: Making use of water wave energy at large is one of the most attractive, low-carbon, and renewable ways to generate electric power. The emergence of triboelectric nanogenerator (TENG) provides a new approach for effectively harvesting such low-frequency, irregular, and “random” energy. In this work, a TENG array consisting of spherical TENG units based on springassisted multilayered structure is devised to scavenge water wave energy. The introduction of spring structure enhances the output performance of the spherical TENG by transforming low-frequency water wave motions into high-frequency vibrations, while the multilayered structure increases the space utilization, leading to a higher output of a spherical unit. Owing to its unique structure, the output current of one spherical TENG unit could reach 120 μA, which is two orders of magnitude larger than that of previous rolling spherical TENG, and a maximum output power up to 7.96 mW is realized as triggered by the water waves. The TENG array fabricated by integrating four units is demonstrated to successfully drive dozens of light-emitting diodes and power an electronic thermometer. This study provides a new type of TENG device with improved performance toward large-scale blue energy harvesting from the water waves.

Global trends in wind speed and wave height over the past 25 years

Abstract: Wind speeds over the world’s oceans have increased over the past two decades, as have wave heights. Studies of climate change typically consider measurements or predictions of temperature over extended periods of time. Climate, however, is much more than temperature. Over the oceans, changes in wind speed and the surface gravity waves generated by such winds play an important role. We used a 23-year database of calibrated and validated satellite altimeter measurements to investigate global changes in oceanic wind speed and wave height over this period. We find a general global trend of increasing values of wind speed and, to a lesser degree, wave height, over this period. The rate of increase is greater for extreme events as compared to the mean condition.

Probing Contact-Electrification-Induced Electron and Ion Transfers at a Liquid-Solid Interface.

Abstract: As a well-known phenomenon, contact electrification (CE) has been studied for decades. Although recent studies have proven that CE between two solids is primarily due to electron transfer, the mechanism for CE between liquid and solid remains controversial. The CE process between different liquids and polytetrafluoroethylene (PTFE) film is systematically studied to clarify the electrification mechanism of the solid-liquid interface. The CE between deionized water and PTFE can produce a surface charges density in the scale of 1 nC cm-2 , which is ten times higher than the calculation based on the pure ion-transfer model. Hence, electron transfer is likely the dominating effect for this liquid-solid electrification process. Meanwhile, as ion concentration increases, the ion adsorption on the PTFE hinders electron transfer and results in the suppression of the transferred charge amount. Furthermore, there is an obvious charge transfer between oil and PTFE, which further confirms the presence of electron transfer between liquid and solid, simply because there are no ions in oil droplets. It is demonstrated that electron transfer plays the dominant role during CE between liquids and solids, which directly impacts the traditional understanding of the formation of an electric double layer (EDL) at a liquid-solid interface in physical chemistry.

Stretchable, Biocompatible, and Multifunctional Silk Fibroin-Based Hydrogels toward Wearable Strain/Pressure Sensors and Triboelectric Nanogenerators.

Abstract: Nowadays, great effort has been devoted to establishing wearable electronics with excellent stretchability, high sensitivity, good mechanical strength, and multifunctional characteristics. Herein, a soft conductive hydrogel is rationally designed by proportionally mixing silk fibroin, polyacrylamide, graphene oxide, and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate). The resultant hydrogel has considerable stretchability and compressibility, which enables it to be assembled into a strain/pressure sensor with a wide sensing range (strain, 2%-600%; pressure, 0.5-119.4 kPa) and reliable stability. Then, the corresponding sensor is capable of monitoring a series of physical signals of the human body (e.g., joint movement, facial gesture, pulse, breathing, etc.). In particular, the hydrogel-based sensor is biocompatible, with no anaphylactic reaction on human skin. More interestingly, this conductive hydrogel exhibits a positive response when it works in a triboelectric nanogenerator; consequently, it lights up 20 commericial green light-emitting diodes. Thus, this silk fibroin-based hydrogel is a kind of multifunctional material toward wearable electronics with versatile applications in health and exercise monitors, soft robots, and power sources.

Spherical triboelectric nanogenerator integrated with power management module for harvesting multidirectional water wave energy

Abstract: With the increasing deterioration of the natural environment, exploiting clean and renewable energy has become the top priority of scientific research today. One of the most prospective routes is to harvest water wave energy using triboelectric nanogenerator (TENG). In this work, a spherical TENG based on spring-assisted multilayered structure was fabricated to collect multidirectional water wave energy, and a power management module (PMM) was integrated to manage the output energy. The output performance of the TENG device was found to be controlled by the water wave frequency, amplitude, and orientation angle between the triggering direction and middle plane. Furthermore, with the PMM, the spherical TENG could output a steady direct current (DC) voltage on a resistance, and the charging speed to a supercapacitor was improved by 100 times. The power-managed performance of the whole TENG was also influenced by the circuit connection configurations among multilayered TENGs. A digital thermometer and a water level detection/alarm system were successfully driven by the power-managed TENG as the demonstrated applications. This work not only provides a type of spherical TENG capable of harvesting multidirectional water wave energy, but also effectively manages the output energy for practical applications toward blue energy. Our study demonstrates a typical example of how to build a self-charging power pack that can effectively use random energy in a regulated manner.

Functional Fibers and Fabrics for Soft Robotics, Wearables, and Human-Robot Interface.

Abstract: Soft robotics inspired by the movement of living organisms, with excellent adaptability and accuracy for accomplishing tasks, are highly desirable for efficient operations and safe interactions with human. With the emerging wearable electronics, higher tactility and skin affinity are pursued for safe and user-friendly human-robot interactions. Fabrics interlocked by fibers perform traditional static functions such as warming, protection, and fashion. Recently, dynamic fibers and fabrics are favorable to deliver active stimulus responses such as sensing and actuating abilities for soft-robots and wearables. First, the responsive mechanisms of fiber/fabric actuators and their performances under various external stimuli are reviewed. Fiber/yarn-based artificial muscles for soft-robots manipulation and assistance in human motion are discussed, as well as smart clothes for improving human perception. Second, the geometric designs, fabrications, mechanisms, and functions of fibers/fabrics for sensing and energy harvesting from the human body and environments are summarized. Effective integration between the electronic components with garments, human skin, and living organisms is illustrated, presenting multifunctional platforms with self-powered potential for human-robot interactions and biomedicine. Lastly, the relationships between robotic/wearable fibers/fabrics and the external stimuli, together with the challenges and possible routes for revolutionizing the robotic fibers/fabrics and wearables in this new era are proposed.