Publications

Self-powered electronic mechanical metamaterials

Active mechanical metamaterials have shown a glimpse of their capacity to create the foundation for intelligent matter. This study presents the concept of mechanical metamaterial electronics (meta-mechanotronics) to design intelligent matter with information processing capability. This advanced functionality is achieved by fusing the mechanical metamaterials, digital electronics and nano energy harvesting technologies. Electronic mechanical metamaterials explored under the meta-mechanotronics paradigm rely merely on their constituent components to perform self-powered mechanical-electrical-logic operations. A proof-of-concept digital unit cell is presented as the 2-bit building block for electronic mechanical metamaterials. The digital unit cell is rationally designed as a monostable origami-inspired metamaterial with twist buckling behavior and specific multi-motion properties to synthesize discrete mechanical configurations and realize digital logic gates. Experimental studies are performed to evaluate the digital computing performance of the designed mechanical metamaterial logic gate.

Breaking Mass Transport Limit for Hydrogen Evolution‐Inhibited and Dendrite‐Free Aqueous Zn Batteries

Abstract It is commonly accepted that batteries perform better at low current densities below the mass‐transport limit, which restricts their current rate and capacity. Here, it is demonstrated that the performance of Zn metal electrodes can be dramatically enhanced at current densities and cut‐off capacities exceeding the mass‐transport limit by using pulsed‐current protocols. These protocols achieve cumulative plating/stripping capacities of 11.0 Ah cm −2 and 3.8 Ah cm −2 at record‐high current densities of 80 and 160 mA cm −2 , respectively. The study identifies and understands the promoted (002)‐textured Zn growth and suppressed hydrogen evolution based on the thermodynamics and kinetics of competing reactions. Furthermore, the over‐limiting pulsed‐current protocol enables long‐life Zn batteries with high mass loading (29 mg cathode cm −2 ) and high areal capacity (7.9 mAh cm −2 ), outperforming cells using constant‐current protocols at equivalent energy and time costs. The work provides a comprehensive understanding of the current‐capacity‐performance relationship in Zn plating/stripping and offers an effective strategy for dendrite‐free metal batteries that meet practical requirements for high capacity and high current rates.

Structure, Bonding, and Properties

Sliding-Triboelectric Nanogenerators Based on In-Plane Charge-Separation Mechanism

Aiming at harvesting ambient mechanical energy for self-powered systems, triboelectric nanogenerators (TENGs) have been recently developed as a highly efficient, cost-effective and robust approach to generate electricity from mechanical movements and vibrations on the basis of the coupling between triboelectrification and electrostatic induction. However, all of the previously demonstrated TENGs are based on vertical separation of triboelectric-charged planes, which requires sophisticated device structures to ensure enough resilience for the charge separation, otherwise there is no output current. In this paper, we demonstrated a newly designed TENG based on an in-plane charge separation process using the relative sliding between two contacting surfaces. Using Polyamide 6,6 (Nylon) and polytetrafluoroethylene (PTFE) films with surface etched nanowires, the two polymers at the opposite ends of the triboelectric series, the newly invented TENG produces an open-circuit voltage up to ∼1300 V and a short-circuit current density of 4.1 mA/m2 with a peak power density of 5.3 W/m2, which can be used as a direct power source for instantaneously driving hundreds of serially connected light-emitting diodes (LEDs). The working principle and the relationships between electrical outputs and the sliding motion are fully elaborated and systematically studied, providing a new mode of TENGs with diverse applications. Compared to the existing vertical-touching based TENGs, this planar-sliding TENG has a high efficiency, easy fabrication, and suitability for many types of mechanical triggering. Furthermore, with the relationship between the electrical output and the sliding motion being calibrated, the sliding-based TENG could potentially be used as a self-powered displacement/speed/acceleration sensor.

Scalable one-step wet-spinning of triboelectric fibers for large-area power and sensing textiles

Mixed-valent oxide-catalytic carbonization for synthesis of monodispersed nano sized carbon spheres

Abstract A mixed-valent oxide-catalytic carbonization process for synthesizing monodispersed carbon spheres at very low cost is reported for the first time. The carbon spheres are formed by catalytic carbonization of natural gas (primarily methane) with the assistance of mixed-valent metal oxides. The catalyst is reusable and the entire synthesis process produces no environmental waste. The product can be controlled by temperature to produce macroscopic quantities and a high percentage (>95%) of nano sized carbon spheres; thus, measurements of their physical properties can be performed easily. The carbon spheres are solid and comprise layered graphitic flakes. The sphere is nucleated from a pentagonal carbon ring, followed by a spiral shell growth. When the sphere grows larger, graphitic flakes of atomic thickness are nucleated on the surface owing to the nucleation of the paired pentagonal-heptagonal (P-H) carbon rings. The combination of the P-H carbon rings with the hexagonal networks produces eight basic graphitic configurations for forming spheres. The unique microstructures of the carbon spheres make them chemically active, mechanically hard and electronically interesting. The carbon spheres can be accreted by a treatment in acetone. The mechanism for the accretion is attributed to the interaction of the hydrogen and oxygen atoms of the acetone molecules with the adsorbed hydrogen and/or oxygen foreign atoms at the edges of the open graphitic flakes on the surface. The high chemical activity of the carbon spheres can have important applications in catalysis. The accretion of the carbon spheres may improve significantly the strength of composite materials made using the spheres. The use of mixed-valence metal oxides as catalysts has opened a new field in catalyst research and applications.

Theory of phase correlations in localized inelastic electron diffraction and imaging

A fuzzy classification system and its application

This paper proposes a fuzzy classification system and its application in tobacco leaves grading. The mathematic description of the fuzzy classification model is given out, and we discuss the fuzzy membership function to calculate the membership of the feature of the pattern and how to obtain the confidence of the feature vector. We also discuss the technique to standardize the pattern space and the optimization of the class spaces. And then the fuzzy reasoning technique in the classification system is provided. Finally, we apply this fuzzy classification model in the tobacco leaves grading system (TGS) to show the efficiency, and conduct experiments and comparison with different methods to prove that the TGS have the similar grading ability as a human expert in practice.

Enhancing Output Performance of Triboelectric Nanogenerator via Charge Clamping (Adv. Energy Mater. 31/2021)

Triboelectric Nanogenerators In article number 2101356, Tinghai Cheng, Zhong Lin Wang, and co-workers enhance the output performance of triboelectric nanogenerators via charge clamping (CC-TENG). The fabricated device consists of a mechanical-switch direct-current TENG, charge clamping module (CCM), and main-TENG. The accumulated charges flow in the loop circuit formed by the main-TENG and CCM, achieving an enhancement in the output performance.

Multilayer wavy-structured robust triboelectric nanogenerator for harvesting water wave energy

Phonon Scattering in Quantitative High-Resolution Electron Microscopy – effects, problems and approaches

Journal Article Phonon Scattering in Quantitative High-Resolution Electron Microscopy – effects, problems and approaches Get access Zhong Lin (ZL) Wang Zhong Lin (ZL) Wang School of Materials Science and Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0245 USA E-mail: zhong.wang@mse.gatech.edu Search for other works by this author on: Oxford Academic Google Scholar Microscopy and Microanalysis, Volume 8, Issue S02, 1 August 2002, Pages 1602–1603, https://doi.org/10.1017/S1431927602104594 Published: 01 August 2002

Tribotronic Enhanced Photoresponsivity of a MoS₂ Phototransistor

Molybdenum disulfide (MoS 2 ) has attracted a great attention as an excellent 2D material for future optoelectronic devices. Here, a novel MoS 2 tribotronic phototransistor is developed by a conjunction of a MoS 2 phototransistor and a triboelectric nanogenerator (TENG) in sliding mode. When an external friction layer produces a relative sliding on the device, the induced positive charges on the back gate of the MoS 2 phototransistor act as a “gate” to increase the channel conductivity as the traditional back gate voltage does. With the sliding distance increases, the photoresponsivity of the device is drastically enhanced from 221.0 to 727.8 A W −1 at the 100 mW cm −2 UV excitation intensity and 1 V bias voltage. This work has extended the emerging tribotronics to the field of photodetection based on 2D material, and demonstrated a new way to realize the adjustable photoelectric devices with high photoresponsivity via human interfacing.

DAMAGE FORMATION IN SI(100) INDUCED BY MEV SELF-ION IMPLANTATION

Damage formation in Si(100) induced by MeV self-ion implantation was studied using the Rutherford backscattering and channeling technique. Damage accumulations were found to be produced mainly near the ions' end of range. Two distinct regions were observed for dose dependence upon damage. One is for low doses, in which the damage increases slowly with dose. The second region is for high-dose implantation, in which the damage increases rapidly as the dose increases. Beam self-annealing was found in MeV Si ion implanted Si(100). The effects of the energy depositions on the defect production are also discussed.

High performance sound driven triboelectric nanogenerator for harvesting noise energy

Simultaneously Harvesting Electrostatic and Mechanical Energies from Flowing Water by a Hybridized Triboelectric Nanogenerator

Flowing water contains not only mechanical kinetic energy, but also the electrostatic energy owing to the triboelectric charges caused by its contact with surrounding media such as air. In this paper, a water wheel hybridized triboelectric nanogenerator (TENG), composed of a water-TENG part and a disk-TENG part, has been developed for simultaneously harvesting the two types of energies from the tap water flowing from a household faucet. The wheel blades of the hybridized TENG are composed by superhydrophobic polytetrafluoroethylene (PTFE) thin films with nanostructures, which are used as water-TENG to harvest the electrostatic energy from the flowing water. In addition, the flowing water impacted on the wheel blades also causes the rotation motion of disk-TENG and can be used to harvest the mechanical kinetic energy. The short-circuit current of the water-TENG and the disk-TENG at a flowing water rate of 54 mL/s can reach 12.9 and 3.8 μA, respectively. The hybridized TENG is also demonstrated to harvest wind energy and acts as a self-powered sensor to detect the flowing water rate and wind speed. All these results show the potentials of the hybridized TENG for harvesting multiple types of energies from the environment.

Effect of dissimilar anion annealing on structures of InAs/GaAs quantum dots

Raising the Working Temperature of a Triboelectric Nanogenerator by Quenching Down Electron Thermionic Emission in Contact‐Electrification

As previously demonstrated, contact-electrification (CE) is strongly dependent on temperature, however the highest temperature in which a triboelectric nanogenerator (TENG) can still function is unknown. Here, by designing and preparing a rotating free-standing mode Ti/SiO2 TENG, the relationship between CE and temperature is revealed. It is found that the dominant deterring factor of CE at high temperatures is the electron thermionic emission. Although it is normally difficult for CE to occur at temperatures higher than 583 K, the working temperature of the rotating TENG can be raised to 673 K when thermionic emission is prevented by direct physical contact of the two materials via preannealing. The surface states model is proposed for explaining the experimental phenomenon. Moreover, the developed electron cloud-potential well model accounts for the CE mechanism with temperature effects for all types of materials. The model indicates that besides thermionic emission of electrons, the atomic thermal vibration also influences CE. This study is fundamentally important for understanding triboelectrification, which will impact the design and improve the TENG for practical applications in a high temperature environment.

Matryoshka-inspired hierarchically structured triboelectric nanogenerators for wave energy harvesting