Zichuan Yi

Electrowetting displays (EWDs) are promising reflective display devices featuring simple structures, fast response speeds, and rich colors. However, conventional simulation models for EWDs suffer from numerical over-constraints caused by redundant driving terms, as well as reference frame mismatch inherent in the phase field method (PFM). These two problems hinder the accurate design of driving waveforms. To address these problems, a two-dimensional (2D) single-pixel decoupled model (DM) was proposed in this work. The calculation of microscopic electrostatic volume forces was eliminated to resolve the over-constraints. Simultaneously, the macroscopic contact-angle formula was rigorously corrected to resolve the reference frame mismatch. Comparative simulations demonstrated that the dynamic behavior of the proposed DM was highly consistent with the actual luminance curve measured in physical experiments, verifying its physical fidelity. Finally, a step-sinusoidal alternating current (SSAC) driving waveform was designed based on this reliable DM. Luminance experiments demonstrated that the SSAC waveform effectively improved the response speed and reduced luminance fluctuations. During a 90-second continuous driving durability test, the variance and interquartile range (IQR) of the luminance data were only 1.762 and 2.098, respectively. The stability of the luminance fluctuations improved by 51.7% and 56.8% compared with the two contrast waveforms.

Precise manipulation of two-phase flow in micro-confined electrowetting pixels is limited by contact angle hysteresis (CAH). To elucidate this non-equilibrium process, we establish a high-fidelity electrohydrodynamic (EHD) phase-field simulation framework. The model rigorously couples Navier–Stokes equations with molecular kinetic theory (MKT) to characterize energy dissipation at the three-phase contact line (TCL) and further integrates charge transport kinetics. Numerical results reveal CAH is driven by physical pinning and interfacial charge trapping, with the latter dominating interfacial retreat and causing significant residual displacement. Furthermore, analysis shows alternating current (AC) waveforms mitigate charge accumulation and promote depinning via micro-oscillations, minimizing the hysteresis loop compared to direct current (DC) waveforms. Additionally, an overdrive strategy utilizing a suprathreshold Maxwell stress pulse rapidly overcomes static friction. This strategy significantly improves transient dynamics, substantially reducing the time to reach 90% of the steady-state target from 19.6 ms (under standard DC waveform driving) to 7.4 ms. This work provides a comprehensive theoretical basis and design criteria for optimizing active driving strategies in optofluidic and digital microfluidic systems.

Three-color electrophoretic display (EPD) makes up for the limitation of traditional EPDs in color representation. However, when displaying red color, there are issues such as long response time and low red saturation. In order to improve these defects, a simulation model was constructed using COMSOL finite element simulation method to explore the movement of electro-phoretic particles. Leveraging the principles of three-color EPDs and electrophoresis theory, a novel driving scheme was proposed. This scheme employed high-frequency voltage and low-voltage differential oscillation, aiming to expedite the response time of red particles and enhance the red saturation. The final experimental results showed that the response time of the red particles was 1.76 s, a decrease of 2.42 s, the number of flickers was 1, a decrease of 8, and the maximum red saturation rose to 0.53, an increase of 0.08. The proposed driving scheme effectively improved the red display performance of three-color EPDs.

Electrowetting displays (EWDs) are a new generation of electronic paper displays, featuring low power consumption and a wide viewing angle. Owing to their alignment with green environmental protection and energy conservation concepts, the EWDs exhibit vast market potential. However, current EWDs face challenges such as high driving voltages, ink backflow, response speed and aperture ratio which need further improvement. Hence, this paper describes for the first time the preparation of hexagonal‐pixel EWDs based on the principle of 2D dense tiling and microfluidics theory at the corner. Compared with square‐pixel EWDs, the hexagonal‐pixel EWDs reduced the threshold voltage by 42.67% and the voltage required to maintain the maximum aperture ratio by 13.94%, while keeping the maximum aperture ratio unchanged. Moreover, based on ink motion theory in EWDs, a hybrid driving waveform combining exponential and alternating current (AC) is proposed for the prepared hexagonal‐pixel EWDs. Compared with traditional direct current (DC) and pulse width modulation (PWM) driving waveforms, this driving waveform reduced the brightness fluctuations from 22.374 and 20.726 to 3.110 in the ink driving stage, and from 4.211 and 25.316 to 1.827 in the stable display stage, respectively.

We theoretically investigate the supercurrent and superconducting diode effect (SDE) in an Aharonov–Bohm (AB) interferometer sandwiched between two aluminium-based superconducting leads. The interferometer features a quantum dot (QD), which is created in an indium arsenide (InAs) semiconductor nanowire by local electrostatic gating, inserted in one of its arms and a magnetic flux threading through the ring structure. The magnetic flux breaks the system time-reversal symmetry by modulating the quantum phase difference between electronic transport through the QD path and the direct arm, which enhances constructive interference in one direction and destructive interference in the other. This leads to a discrepancy between the magnitudes of the forward and reverse critical supercurrents and is the core mechanism that induces the SDE. We demonstrate that the critical supercurrents exhibit Fano line shapes arising from the interference between discrete Andreev bound states in the QD and continuous states in the direct arm. It is found that when electron transport is dominated by the QD-containing path as compared to the direct arm path of the interferometer, the diode efficiency reaches a maximum, with values as high as 80%. In contrast, when the direct arm path dominates transport, the diode efficiency becomes weak. This attenuation is attributed to the participation of higher-order quantum interference processes, which disrupt the nonreciprocal supercurrent balance. Importantly, the proposed AB interferometer system has a relatively simple structure, and the realization of the SDE within it is feasible using current nano-fabrication technologies.

As a reflective display technology, electrowetting displays (EWDs) have the advantages of a paper-like appearance, fast response speed, and full-color capability. However, the use of an overdriving voltage to improve the response speed of EWDs can cause fluctuations in display luminance, which manifest as glitches in the luminance change curve. In order to eliminate this luminance instability phenomenon, a new driving pulse is proposed, which consists of an overdriving phase, a switching phase, and a driving phase. Firstly, a simplified equivalent circuit model is proposed to apply a target voltage in the driving phase without break down of the hydrophobic insulating layer. Secondly, a COMSOL (Version 6.3) two-dimensional model is established to simulate the oil contraction process and conduct comparisons, so as to ensure the effectiveness of the overdriving pulse. Then, the overdriving phase is applied to improve oil response speed, and a linear function is used in the switching phase to alleviate glitch phenomena. Moreover, the influences of overdriving voltage, overdriving time, and linear switching time on the luminance curve are analyzed by charge trapping theory in order to obtain optimal performance. The experimental results show that the glitch phenomenon is eliminated effectively, and the luminance of the EWD is increased by 1.02% and 1.96% compared with the step switching pulse and PWM pulse, respectively, while the response time is shortened by 1.82% and 8.05% compared with the step switching pulse and PWM pulse, respectively.

Electronic transport through T-shaped double quantum dots (TDQDs) connected to normal metallic leads is studied theoretically by using a nonequilibrium Green’s function method. It is assumed that the Coulomb interaction exists only in the central QD (QD-1) sandwiched between the leads, and it is absent in the other reference QD (QD-2) side-coupled to QD-1. We also consider the impacts of Majorana bound states (MBSs), which are prepared at the opposite ends of a topological superconductor nanowire (hereafter called a Majorana nanowire) connected to QD-2, on the electrical current and differential conductance. Our results show that by the combined effects of the Coulomb interaction in QD-1 and the MBSs, a negative differential conductance (NDC) effect emerges near the zero-bias point, where MBSs play significant roles. Now, the electrical current decreases despite the increasing bias voltage. The NDC is prone to occur under conditions of low temperature, and both of the two QDs’ energy levels are resonant to the leads’ zero Fermi energy. Its magnitude, which is characterized by a peak-to-valley ratio, can be enhanced up to 3 by increasing the interdot coupling strength, and it depends on the dot-MBS hybridization strength nonlinearly. This prominent NDC combined with the previously found zero-bias anomaly (ZBA) of the differential conductance is useful in designing novel quantum electric devices, and it may also serve as an effective detection means for the existence of MBSs, which is still a challenge in solid-state physics.

Electronic transport through T-shaped double quantum dots (TDQDs) connected to normal metallic leads is studied theoretically by using the nonequilibrium Green's function method. It is assumed that the Coulomb interaction exists only in the central QD (QD-1) that directly coupled to the leads, and is absent in the other reference QD (QD-2) side-coupled to QD-1. We also consider the impacts of Majorana bound states (MBSs), which are prepared at the opposite ends of a topological superconductor nanowire (Majorana nanowire) hybridized to QD-2, on the electrical current and differential conductance. Our results show that by the combined effects of the Coulomb interaction in QD-1 and the MBSs, a phenomenon of negative differential conductance (NDC) emerges near the zero-bias point. Now the electrical current decreases despite of increasing bias voltage. The NDC is prone to occur under the conditions of low temperature and both of the two QDs' energy levels are in resonant to the zero Fermi level. Its magnitude characterized by a peak-to-valley ratio can be enhanced up to 3 by increasing the interdot coupling strength, and depends on the dot-MBS hybridization strength nonlinearly. This prominent NDC combined with the previously found zero-bias anomaly (ZBA) of the differential conductance are useful in designing novel quantum electric devices, and may also serve as an effective detection means for the existence of MBSs which is still a challenge in solid-state physics.

As the most promising new reflective display technology, electrowetting displays (EWDs) have the advantages of a simple structure, fast response, high contrast, and rich colors. However, due to the hysteresis effect, the grayscales of EWDs cannot be accurately controlled, which seriously restricts the industrialization process of this technology. In this paper, the oil movement process in an EWD pixel cell was simulated, and the influence of oil viscosity on the hysteresis effect was studied based on the proposed simulation model. Firstly, the cause of the hysteresis effect was analyzed through the hysteresis curve of an EWD. Then, based on the COMSOL Multiphysics simulation environment, the oil movement process in an EWD pixel cell was simulated by coupling the phase field of laminar two-phase flow and electrostatic field. Finally, based on the simulation model, the influence of oil viscosity on the hysteresis effect in an EWD pixel cell was studied. We observed that the maximum hysteresis difference in the hysteresis effect increased with the increase in oil viscosity and decreased with the decrease in oil viscosity. The oil viscosity had little effect on the maximum aperture ratio of EWD. The pixel-on response time and pixel-off response time increased with the increase in oil viscosity.

Electrowetting displays (EWDs) face challenges such as oil film splitting and luminance fluctuations, hindering stable display performance. This study employed a high-precision three-dimensional simulation model to investigate and validate oil film splitting mechanisms. The model enabled detailed optimization of a new two-stage driving scheme, integrating a sinusoidal directing (SD) and a gradient asymmetrical alternating current (GAAC) driving scheme. The proposed scheme significantly suppressed oil film splitting, reduced luminance variance by 72.3% compared to traditional methods, and improved luminance stability by 41.6%. These findings highlight the potential of simulation-driven approaches to enhance EWD performance and expand applications of microfluidic technologies.