Electrophoretic display is realized by controlling colored nanoparticles moving in micrometer spaces via electrophoresis. The quality of information display is therefore affected by the unsynchronized particle moving speed and the mismatched electric signal according to the crosstalk of the electric field and inhomogeneous material distribution. In this work, we analyzed the mechanism of a fringe phenomenon that affected the information display quality of electrophoretic displays (EPDs). Electrical driving waveforms (voltage signals) are designed to reduce the fringe phenomenon. By using the optimizing driving waveform, we proposed that the fringe phenomenon is quantified as gray value that can be diminished by 25.5, while keeping a response time of 200 ms.
Janus particles (JNPs) with controlled anisotropies are regarded as promising materials for sophisticated building blocks and assembly. Herein a straightforward method was proposed for the synthesis of uniformly distributed JNPs with controllable anisotropies, showing two compartmental bulbs with different surface wettability. The synthetic strategy is based on the phase separation-induced styrene liquid protrusion on seed poly(styrene-co-acrylic acid) (CPSAA) nanoparticles via controlled swelling, with the formed polystyrene (PS) and CPSAA compartments corresponding to the amount of monomers. The size (lateral length) ratio of formed PS and CPSAA bulbs, D PS /D CPSAA , defined as "Janusity", has been precisely tuned in the range of 0−0.91 by controlling the mass ratio of two monomers. Obtained JNPs with tunable amphiphilicity are utilized as colloid surfactants to prepare Pickering-emulsions of both water-in-oil (W/O) and oil-in-water (O/W) with proper Janusity. The stability of achieved W/O and O/W Pickering-emulsions is dependent on the adhesion energy of a JNP at the water−oil interfaces. Prepared JNPs have also being utilized to prepare and stabilize monodisperse droplets in microfluidic devices, demonstrating their high potential for fundamental research and practical applications.
Displays can present information like text, images, or videos in a different color (visible light) by activating the materials in pixels. In a display device, pixels are typically of micrometer size and filled with displaying materials that are aligned and controlled by a display driver integrated circuit. Typical reflective displays can show designed information by manipulating ambient light via the microfluidic behavior in pixels driven by electrophoresis, electrowetting, or electromechanical forces. In this review, we describe the basic working principles and device structures of three reflective displays of electrophoresis display (EPD), electrowetting display (EWD), and interferometric modulator display (IMOD). The optofluidic behavior and controlling factors relating to the display performance are summarized.
Electrophoretic displays (EPDs) have excellent paper-like display features, but their response speed is as long as hundreds of milliseconds. This is particularly important when optimizing the driving waveform for improving the response speed. Hence, a driving waveform design based on the optimization of particle activation was proposed by analyzing the electrophoresis performance of particles in EPD pixels. The particle activation in the driving waveform was divided into two phases: the improving particle activity phase and the uniform reference grayscale phase. First, according to the motion characteristics of particles in improving the particle activity phase, the real-time EPD brightness value can be obtained by an optical testing device. Secondly, the derivative of the EPD brightness curve was used to obtain the inflection point, and the inflection point was used as the duration of improving particle activity phase. Thirdly, the brightness curve of the uniform reference grayscale phase was studied to set the driving duration for obtaining a white reference grayscale. Finally, a set of four-level grayscale driving waveform was designed and validated in a commercial E-ink EPD. The experimental results showed that the proposed driving waveform can cause a reduction by 180 ms in improving particle activity phase and 120 ms in uniform reference grayscale phase effectively, and a unified reference grayscale can be achieved in uniform reference grayscale phase at the same time.
At present, three-color electrophoretic displays (EPDs) have problems of dim brightness and insufficient color saturation. In this paper, a driving waveform based on a damping oscillation was proposed to optimize the red saturation in three-color EPDs. The optimized driving waveform was composed of an erasing stage, a particles activation stage, a red electrophoretic particles purification stage, and a red display stage. The driving duration was set to 360 ms, 880 ms, 400 ms, and 2400 ms, respectively. The erasing stage was used to erase the current pixel state and refresh to a black state. The particles’ activation stage was set as two cycles, and then refreshed to the black state. The red electrophoretic particles’ purification stage was a damping oscillation driving waveform. The red and black electrophoretic particles were separated by changing the magnitude and polarity of applied electric filed, so that the red electrophoretic particles were purified. The red display stage was a low positive voltage, and red electrophoretic particles were driven to the common electrode to display a red state. The experimental results showed that the maximum red saturation could reach 0.583, which was increased by 27.57% compared with the traditional driving waveform.
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