arXiv subjects

Zhong Lin Wang

Publications and source records attributed to Zhong Lin Wang.

11 recordsLinked to original sources

arXiv2026

On the multi-frequency electromagnetic emission from a rotating charged dielectric disk made of isotropic media: -a verification of Maxwell's equations for a mechano-driven medium system

The electromagnetic behavior of a uniformly moving medium has been traditionally described by the Minkowski's theory, based on which the electromagnetic (EM) emission from a rotating isotropic medium should be linear with the rotation frequency, which means that the frequency of the EM emission should be the same as that of the excitation source. However, we experimentally observed that the near-field EM emission from a rotating charged dielectric disk shows discrete multi-harmonics at frequencies of nfR, with n =1 to 6, where fR is the rotation frequency of the disk. By reversing the rotating direction of the disk, the phase shift for the observed magnetic field is π for odd harmonics, but it remains in phase for the even harmonics. The experimental results may not be consistent with the Minkowski's theory, but the data can be well explained using the Maxwell's equations for a mechano-driven media system (MEs-f-MDMS). This study not only provides a solid proof to MEs-f-MDMS, but also establishes the theory for describing the near-field EM emission from accelerated medium motion, which has many engineering applications.

physics.app-ph↗

arXiv2026

Physics-governed executable modelling of triboelectric nanogenerators

Predictive modelling of triboelectric nanogenerators (TENGs) remains fragmented across analytical theories, finite-geometry solvers and disconnected simulation workflows. These disparate approaches must be unified into an executable framework to advance quantitative TENG research.Here we introduce a charge-defined modelling framework and implement it as TENG-CLAW, a physics-governed platform for traceable TENG simulation. The framework establishes a self-consistent electrostatic hierarchy in which triboelectric charges, pre-charging charges and compensating electrode charges serve as defining state variables.This hierarchy connects the infinite plate analytical limit for near-uniform fields with finite-geometry numerical formulations required for edge-dominated devices. Built on this basis, TENG-CLAW converts user-defined research requests into physically admissible simulation tasks, so that generated outputs are tied to explicit charge states, boundary conditions, solver routes and reusable artifacts across spatial, temporal, field-level, comparative and reporting workflows. This work establishes a rigorous computational basis for interpreting TENG mechanisms and provides reproducible research infrastructure for simulation and physics-guided device design.

physics.app-ph↗

arXiv2026

Coupling the Minkowski's theory with the Maxwell's equations for a mechano-driven media system for engineering electromagnetism

The Minkowski's theory is regarded as the classical approach for describing the electromagnetism of uniformly moving objects by elegantly utilizing the format-invariance of the Maxwell's equations in inertia reference frames under Lorentz transformation. However, in practice, we usually have the cases of a medium that has boundary and moves with acceleration, such as a rotating dielectric disc or a magnetic object. To fully describe the electromagnetic behavior of such a system, we have developed the Maxwell's equations for a mechano-driven media system (MEs-f-MDMS). This paper is to expand the Minkowski's approach for deriving the constitutive equations and the boundary conditions for MEs-f-MDMS under low-speed approximation (v << c), based on which the equations can be properly solved for describing engineering electromagnetism, with considering the coupling among electric field - magnetic field - mechanical force field. In practice, mechanical action is not merely passive motion through space but an active source of electromagnetic generation and modulation. Our theory makes it possible to treat the electrodynamics by including medium deformation, strain gradients, rotational dynamics, and interfacial contact processes in the full calculation.

physics.gen-ph↗

arXiv2025

Integrating Machine Learning with Triboelectric Nanogenerators: Optimizing Electrode Materials and Doping Strategies for Intelligent Energy Harves

The integration of machine learning techniques with triboelectric nanogenerators (TENGs) offers a transformative pathway for optimizing energy harvesting technologies. In this study, we propose a comprehensive framework that utilizes graph neural networks to predict and enhance the performance of TENG electrode materials and doping strategies. By leveraging an extensive dataset of experimental and computational results, the model effectively classifies electrode materials, predicts optimal doping ratios, and establishes robust structure-property relationships. Key findings include a 65.7% increase in energy density for aluminum-doped PTFE and an 85.7% improvement for fluorine-doped PTFE, highlighting the critical influence of doping materials and their concentrations. The model further identifies PTFE as a highly effective negative electrode material, achieving a maximum energy density of 1.12 J/cm$^2$ with 7% silver (Ag) doping when copper (Cu) is used as the positive electrode. This data-driven approach not only accelerates material discovery but also significantly reduces experimental costs, providing novel insights into the fundamental factors influencing TENG performance. The proposed methodology establishes a robust platform for intelligent material design, advancing the development of sustainable energy technologies and self-powered systems.

cond-mat.mtrl-sci↗

arXiv2024

Wireless Electronic-free Mechanical Metamaterial Implants

Despite significant advancements in wireless smart implants over the last two decades, current implantable devices still operate passively and require additional electronic modules for wireless transmission of the stored biological data. To address these challenges, we propose an innovative wireless force sensing paradigm for implantable systems through the integration of mechanical metamaterials and nano energy harvesting technologies. We demonstrate composite mechanical metamaterial implants capable of serving as all-in-one wireless force sensing units, incorporating functions for power generation, sensing and transmission with ultra-low power requirements. In this alternative communication approach, the electrical signals harvested by the implants from mechanical stimuli are utilized directly for the wireless transmission of the sensed data. We conduct experimental and theoretical studies to demonstrate the wireless detection of the generated strain-induced polarization electric field using electrodes. The feasibility of the proposed wireless force sensing approach is evaluated through a proof-of-concept orthopedic implant in the form of a total knee replacement. The findings indicate that the created wireless, electronic-free metamaterial implants with a power output as low as 0.1 picowatts enable direct, self-powered wireless communication during force sensing across air, simulated body fluid and animal tissue. We validate the functionality of the proposed implants through a series of experiments conducted on an ex vivo human cadaver knee specimen. Furthermore, the effect of electrode size and placement on the strength of the received signals is examined. Finally, we highlight the potential of our approach to create a diverse array of mechanically-tunable wireless force sensing implants without relying on any external power sources.

physics.med-ph↗

arXiv2023

In-Situ Single Particle Reconstruction Reveals 3D Evolution of PtNi Nanocatalysts During Heating

Tailoring nanoparticles composition and morphology is of particular interest for improving their performance for catalysis. A challenge of this approach is that the nanoparticles optimized initial structure often changes during use. Visualizing the three dimensional (3D) structural transformation in situ is therefore critical, but often prohibitively difficult experimentally. Although electron tomography provides opportunities for 3D imaging, restrictions in the tilt range of in situ holders together with electron dose considerations limit the possibilities for in situ electron tomography studies. Here, we present an in situ 3D imaging methodology using single particle reconstruction (SPR) that allows 3D reconstruction of nanoparticles with controlled electron dose and without tilting the microscope stage. This in situ SPR methodology was employed to investigate the restructuring and elemental redistribution within a population of PtNi nanoparticles at elevated temperatures. We further examined the atomic structure of PtNi and found a heat induced transition from a disordered to an ordered phase. Changes in structure and elemental distribution were linked to a loss of catalytic activity in the oxygen reduction reaction. The in situ SPR methodology employed here could be extended to a wide range of in situ studies employing not only heating, but gaseous, aqueous or electrochemical environments to reveal in operando nanoparticle evolution in 3D.

physics.app-ph↗

arXiv2023

Triboelectric Junction: A Model for Dynamic Metal-Semiconductor Contacts

Static metal-semiconductor contacts are classified into Ohmic contacts and Schottky contacts. As for dynamic metal-semiconductor contacts, the in-depth mechanism remains to be studied. We here define a "triboelectric junction" model for analyzing dynamic metal-semiconductor contacts, where a space charge region induced by the triboelectric effect dominates the electron-hole separation process. Through theoretical analysis and experiments, we conclude that the triboelectric junction affects the electric output in two aspects: 1) the junction direction determines the output polarity; 2) the junction strength determines the output amplitude. The junction direction and junction strength are both related to the electron-affinity difference between the contact metal and semiconductor. We find that the standard electrode potential in electrochemistry best describes the electron affinity of a dynamic metal-semiconductor contact.

physics.app-ph↗

arXiv2023

The expanded Maxwell's equations for a mechano-driven media system that moves with acceleration

In classical electrodynamics, by motion for either the observer or the media, it always naturally assumed that the relative moving velocity is a constant along a straight line (e.g., in inertia reference frame), so that the electromagnetic behavior of charged particles in vacuum space can be easily described using special relativity. However, for engineering applications, the media have shapes and sizes and may move with acceleration, and recent experimental progresses in triboelectric nanogenerators have revealed evidences for expanding the Maxwell's equations to include media motion that could be time and even space dependent. Therefore, we have developed the expanded Maxwell's equations for a mechano-driven media system (MEs-f-MDMS) by neglecting relativistic effect. This article first presents the updated progresses made in the field. Secondly, we extensively investigated the Faraday's law of electromagnetic induction for a media system that moves with an acceleration. We concluded that, the newly developed MEs-f-MDMS are required for describing the electrodynamics inside a media that has a finite size and volume and move with and even without acceleration. The classical Maxwell's equations are to describe the electrodynamics in vacuum space when the media in the nearby are moving.

physics.class-ph↗

arXiv2022

Maxwell's equations for a mechano-driven, shape-deformable, charged-media system, slowly moving at an arbitrary velocity field v(r,t)

The differential form of the Maxwell's equations was first derived based on an assumption that the media are stationary, which is the foundation for describing the electro-magnetic coupling behavior of a system. For a general case in which the medium has a time-dependent volume, shape and boundary and may move at an arbitrary velocity field v(r,t) and along a general trajectory, we derived the Maxwell's equations for a mechano-driven slow-moving media system directly starting from the integral forms of four physics laws, which should be accurate enough for describing the coupling among mechano-electro-magnetic interactions of a general system in practice although it may not be Lorentz covarance. Our key point is directly from the four physics laws by describing all of the fields, the space and the time in the frame where the observation is done. The equations should be applicable to not only moving charged solid and soft media that has acceleration, but also charged fluid/liquid media, e.g., fluid electrodynamics. This is a step toward the electrodynamics in non-inertia frame of references. General strategies for solving the Maxwell's equations for mechano-driven slowing moving medium are presented using the perturbation theory both in time and frequency spaces. Finally, approaches for the electrodynamics of moving media are compared, and related discussions are given about a few interesting questions.

physics.class-ph↗

arXiv2022

Interface inter-atomic electron-transition induced photon emission in contact-electrification

Contact electrification (CE) (or triboelectrification) is the phenomena where charges are produced through physical contact between two materials. Here we report the atomic featured photon emission spectra during CE between two solid materials. Photon emission provides the evidence that electron transfer takes place at the interface from an atom in one material to another atom in the other material during CE. This process is the contact electrification induced interface photon emission spectroscopy (CEIIPES). It naturally paves a way to a spectroscopy corresponding to the CE at an interface, which might impact our understanding of the interaction between solids, liquids, and gases. The physics presented here could be expanded to Auger electron excitation, x-ray emission, and electron emission in CE for general cases, which remain to be explored. This could lead to a general field that may be termed as contact electrification induced interface spectroscopy (CEIIS).

cond-mat.mtrl-sci↗

arXiv2013

Electrical Tuning of Surface Plasmon Polariton Propagation in Graphene-Nanowire Hybrid Structure

We demonstrate a dynamic surface plasmonic modulation of graphene-nanowire hybrid structures in visible light range, which was thought to be a tough task for graphene based field effect transistor modulator previously. Static modulation depth of as high as 0.07 dB/μm has been achieved experimentally. Carefully simulation indicates the strongly focused electromagnetic field and dramatically enhanced electric field at the interface between a silver NW and a graphene sheet are key roles for bringing the optical response of the device to the visible range. Furthermore, the modulation behaviors near the Dirac point of monolayer graphene and the singularity of gap-induced bilayer graphene are investigated.

cond-mat.mes-hall↗