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Xu W, Yi Z, Long Z, Zhang H, Jiang J, Liu L, Chi F, Tan D, Wang H. Stability Study of Multi-Level Grayscales Based on Driving Waveforms for Electrowetting Displays. MICROMACHINES 2023; 14:1123. [PMID: 37374707 DOI: 10.3390/mi14061123] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/12/2023] [Revised: 05/24/2023] [Accepted: 05/25/2023] [Indexed: 06/29/2023]
Abstract
Electrowetting Display (EWD) is a new reflective display with an outstanding performance of color video playback. However, some problems still exist and affect its performance. For instance, oil backflow, oil splitting, and charge trapping phenomena may occur during the driving process of EWDs, which would decrease its stability of multi-level grayscales. Therefore, an efficient driving waveform was proposed to solve these disadvantages. It consisted of a driving stage and a stabilizing stage. First, an exponential function waveform was used in the driving stage for driving the EWDs quickly. Then, an alternating current (AC) pulse signal waveform was used in the stabilizing stage to release the trapped positive charges of the insulating layer to improve display stability. A set of four level grayscale driving waveforms were designed by using the proposed method, and it was used in comparative experiments. The experiments showed that the proposed driving waveform could mitigate oil backflow and splitting effects. Compared to a traditional driving waveform, the luminance stability was increased by 8.9%, 5.9%, 10.9%, and 11.6% for the four level grayscales after 12 s, respectively.
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Affiliation(s)
- Wanzhen Xu
- College of Electronic Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China
- South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China
| | - Zichuan Yi
- College of Electronic Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China
| | - Zhengxing Long
- College of Electronic Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China
- School of Information and Optoelectronic Science and Engineering, South China Normal University, Guangzhou 510006, China
| | - Hu Zhang
- College of Electronic Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China
| | - Jiaquan Jiang
- College of Electronic Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China
| | - Liming Liu
- College of Electronic Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China
| | - Feng Chi
- College of Electronic Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China
| | - Ding Tan
- Power China Hubei Engineering Co., Ltd., Wuhan 430048, China
| | - Huan Wang
- Hydro Electric Power System Engineering Company, Wuhan 430000, China
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Inhibiting Oil Splitting and Backflow in Electrowetting Displays by Designing a Power Function Driving Waveform. ELECTRONICS 2022. [DOI: 10.3390/electronics11132081] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Electrowetting display (EWD) is one of the latest and most promising reflective displays. However, some defects are easily caused in a driving process. For example, the aperture ratio of pixels can be reduced due to oil splitting, and the grayscale cannot be stabilized due to charge trapping. These defects can be effectively solved by designing driving waveforms for EWDs. So, a power function driving waveform was proposed in this paper, which consisted of an oil splitting suppression stage, a direct current (DC) driving stage and an oil stabilization stage. Firstly, the relationships among luminance values, power constants and driving time were measured. An optimal oil splitting suppression stage was obtained, which could effectively inhibit oil splitting. Then, the response time could be reduced by a DC voltage in the DC driving stage. Finally, a voltage slope was tested during the oil stabilization stage, which was used to counteract voltage created by the charge trapping. The experimental results showed that compared with a linear function waveform, the response time could be shortened by 16.1%, and the luminance value could be increased by 3.8%. The aperture ratio and oil stability of EWD can be effectively improved by these findings, thereby increasing its potential application in the display field.
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A Driving Method for Reducing Oil Film Splitting in Electrowetting Displays. MEMBRANES 2021; 11:membranes11120920. [PMID: 34940421 PMCID: PMC8707651 DOI: 10.3390/membranes11120920] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/23/2021] [Revised: 11/16/2021] [Accepted: 11/22/2021] [Indexed: 11/16/2022]
Abstract
Electrowetting displays (EWDs) are one of the most potential electronic papers. However, they have the problem of oil film splitting, which could lead to a low aperture ratio of EWDs. In this paper, a driving waveform was proposed to reduce oil film splitting. The driving waveform was composed of a rising stage and a driving stage. First, the rupture voltage of oil film was analyzed by testing the voltage characteristic curve of EWDs. Then, a quadratic function waveform with an initial voltage was applied at the rising stage to suppress oil film splitting. Finally, a square wave was applied at the driving stage to maintain the aperture ratio of EWDs. The experimental results show that the luminance was increased by 8.78% and the aperture ratio was increased by 4.47% compared with an exponential function driving waveform.
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Zeng W, Yi Z, Zhou X, Zhao Y, Feng H, Yang J, Liu L, Chi F, Zhang C, Zhou G. Design of Driving Waveform for Shortening Red Particles Response Time in Three-Color Electrophoretic Displays. MICROMACHINES 2021; 12:578. [PMID: 34069735 PMCID: PMC8161037 DOI: 10.3390/mi12050578] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/16/2021] [Revised: 05/18/2021] [Accepted: 05/18/2021] [Indexed: 01/18/2023]
Abstract
Three-color electrophoretic displays (EPDs) have the advantages of multi-color display and low power consumption. However, their red particles have the disadvantage of long response time. In this paper, a driving waveform, which is based on electrophoresis theory and reference gray scale optimization, was proposed to shorten the response time of red particles in three-color EPDs. The driving waveform was composed of erasing stage, reference gray scale forming stage, red driving stage, and white or black driving stage. Firstly, the characteristics of particle motion were analyzed by electrophoresis theory and Stokes law. Secondly, the reference gray scale of the driving waveform was optimized to shorten the distance between red particles and a common electrode plate. Finally, an experimental platform was developed to test the performance of the driving waveform. Experimental results showed that the proposed driving waveform can shorten the response time of red particles by 65.57% and reduce the number of flickers by 66.67% compared with the traditional driving waveform.
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Affiliation(s)
- Wenjun Zeng
- College of Electron and Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China; (W.Z.); (X.Z.); (Y.Z.); (H.F.); (J.Y.); (L.L.); (F.C.); (C.Z.)
- South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China;
| | - Zichuan Yi
- College of Electron and Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China; (W.Z.); (X.Z.); (Y.Z.); (H.F.); (J.Y.); (L.L.); (F.C.); (C.Z.)
| | - Xichen Zhou
- College of Electron and Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China; (W.Z.); (X.Z.); (Y.Z.); (H.F.); (J.Y.); (L.L.); (F.C.); (C.Z.)
| | - Yiming Zhao
- College of Electron and Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China; (W.Z.); (X.Z.); (Y.Z.); (H.F.); (J.Y.); (L.L.); (F.C.); (C.Z.)
| | - Haoqiang Feng
- College of Electron and Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China; (W.Z.); (X.Z.); (Y.Z.); (H.F.); (J.Y.); (L.L.); (F.C.); (C.Z.)
- South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China;
| | - Jianjun Yang
- College of Electron and Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China; (W.Z.); (X.Z.); (Y.Z.); (H.F.); (J.Y.); (L.L.); (F.C.); (C.Z.)
| | - Liming Liu
- College of Electron and Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China; (W.Z.); (X.Z.); (Y.Z.); (H.F.); (J.Y.); (L.L.); (F.C.); (C.Z.)
| | - Feng Chi
- College of Electron and Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China; (W.Z.); (X.Z.); (Y.Z.); (H.F.); (J.Y.); (L.L.); (F.C.); (C.Z.)
| | - Chongfu Zhang
- College of Electron and Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China; (W.Z.); (X.Z.); (Y.Z.); (H.F.); (J.Y.); (L.L.); (F.C.); (C.Z.)
| | - Guofu Zhou
- South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China;
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Liu L, Bai P, Yi Z, Zhou G. A Separated Reset Waveform Design for Suppressing Oil Backflow in Active Matrix Electrowetting Displays. MICROMACHINES 2021; 12:mi12050491. [PMID: 33925329 PMCID: PMC8146728 DOI: 10.3390/mi12050491] [Citation(s) in RCA: 12] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/16/2021] [Revised: 04/18/2021] [Accepted: 04/20/2021] [Indexed: 01/18/2023]
Abstract
The electrowetting display (EWD) is a kind of reflective paper-like display. Flicker and grayscale distortion are caused by oil backflow, which is one of the important factors restricting the wide application of EWDs. The charge embedding caused by the electric field force in the dielectric layer is the cause of oil backflow. To suppress oil backflow, a separated reset waveform based on the study of oil movement is proposed in this paper. The driving waveform is divided into two parts: a reset waveform and a grayscale waveform. The reset waveform generated by a reset circuit can be used to output various voltages. The grayscale waveform is set as a traditional PWM waveform. The reset waveform is composed of a charge-releasing stage and oil-moving back stage. Two phases are contained in the charge releasing stage. The overdriving voltage is used during the first phase to reverse the voltage of all pixels. The trapped charges can then be released from the dielectric layer during the second phase. A higher voltage is used during the oil-moving back stage to drive the oil faster in the pixel. By comparing the experimental data, the oil backflow time is extended 761 times by the reset waveform. The four grayscales can be maintained by the reset waveform after driving for 300 s.
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Affiliation(s)
- Linwei Liu
- Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China; (L.L.); (G.Z.)
| | - Pengfei Bai
- Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China; (L.L.); (G.Z.)
- Correspondence: ; Tel.: +86-13631401100
| | - Zichuan Yi
- College of Electron and Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China;
| | - Guofu Zhou
- Guangdong Provincial Key Laboratory of Optical Information Materials and Technology & Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China; (L.L.); (G.Z.)
- Academy of Shenzhen Guohua Optoelectronics, Shenzhen 518110, China
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6
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Controlling the breakup of toroidal liquid films on solid surfaces. Sci Rep 2021; 11:8120. [PMID: 33854150 PMCID: PMC8046813 DOI: 10.1038/s41598-021-87549-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2021] [Accepted: 03/26/2021] [Indexed: 11/09/2022] Open
Abstract
The breakup of a slender filament of liquid driven by surface tension is a classical fluid dynamics stability problem that is important in many situations where fine droplets are required. When the filament is resting on a flat solid surface which imposes wetting conditions the subtle interplay with the fluid dynamics makes the instability pathways and mode selection difficult to predict. Here, we show how controlling the static and dynamic wetting of a surface can lead to repeatable switching between a toroidal film of an electrically insulating liquid and patterns of droplets of well-defined dimensions confined to a ring geometry. Mode selection between instability pathways to these different final states is achieved by dielectrophoresis forces selectively polarising the dipoles at the solid-liquid interface and so changing both the mobility of the contact line and the partial wetting of the topologically distinct liquid domains. Our results provide insights into the wetting and stability of shaped liquid filaments in simple and complex geometries relevant to applications ranging from printing to digital microfluidic devices.
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Progress in Advanced Properties of Electrowetting Displays. MICROMACHINES 2021; 12:mi12020206. [PMID: 33670530 PMCID: PMC7922812 DOI: 10.3390/mi12020206] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/23/2020] [Revised: 02/14/2021] [Accepted: 02/15/2021] [Indexed: 11/17/2022]
Abstract
Electrowetting display (EWD) has promising prospects in the electronic paper industry due to it having superior characteristics, such as the ability to provide a comfortable reading experience and quick response. However, in real applications, there are also problems related to dielectric deterioration, excess power consumption, optical instability and narrow color gamut etc. This paper reviewed the existing challenges and recent progress made in terms of improving the optical performance and reliability of EWD. First, the principle of electrowetting applied in small and confined configurations is introduced and the cause of the failure of the dielectric layer is analyzed. Then, the function of the pixel structures is described to avoid display defects. Next, electric signal modulations are compared in terms of achieving good image quality and optical stability. Lastly, the methods are presented for color panel realization. It was concluded that multi-layer dielectrics, three-dimensional pixel structures, proper electric frequency-and-amplitude modulation and an RGB color panel are expected to resolve the current limitations and contribute to designing advanced reflective displays.
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Editorial for the Special Issue on Optofluidic Devices and Applications. MICROMACHINES 2020; 11:mi11100884. [PMID: 32977550 PMCID: PMC7598251 DOI: 10.3390/mi11100884] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Received: 09/09/2020] [Accepted: 09/20/2020] [Indexed: 11/16/2022]
Abstract
Optofluidic devices are of high scientific and industrial interest in chemistry, biology, material science, pharmacy, and medicine [...].
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Yi Z, Huang Z, Lai S, He W, Wang L, Chi F, Zhang C, Shui L, Zhou G. Driving Waveform Design of Electrowetting Displays Based on an Exponential Function for a Stable Grayscale and a Short Driving Time. MICROMACHINES 2020; 11:mi11030313. [PMID: 32188157 PMCID: PMC7142935 DOI: 10.3390/mi11030313] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 02/08/2020] [Revised: 03/09/2020] [Accepted: 03/12/2020] [Indexed: 11/29/2022]
Abstract
The traditional driving waveform of the electrowetting display (EWD) has many disadvantages, such as the large oscillation of the target grayscale aperture ratio and a long time for achieving grayscale. Therefore, a driving waveform based on the exponential function was proposed in this study. First, the maximum driving voltage value of 30 V was obtained by testing the hysteresis curve of the EWD pixel unit. Secondly, the influence of the time constant on the driving waveform was analyzed, and the optimal time constant of the exponential function was designed by testing the performance of the aperture ratio. Lastly, an EWD panel was used to test the driving effect of the exponential-function-driving waveform. The experimental results showed that a stable grayscale and a short driving time could be realized when the appropriate time constant value was designed for driving EWDs. The aperture ratio oscillation range of the gray scale could be reduced within 0.95%, and the driving time of a stable grayscale was reduced by 30% compared with the traditional driving waveform.
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Affiliation(s)
- Zichuan Yi
- College of Electron and Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China; (Z.Y.); (F.C.); (C.Z.); (L.S.)
| | - Zhenyu Huang
- Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China; (W.H.); (L.W.); (G.Z.)
- Shenzhen Guohua Optoelectronics Tech. Co., Ltd., Shenzhen 518110, China;
- Correspondence: ; Tel.: +86-0755-2941-5855
| | - Shufa Lai
- Shenzhen Guohua Optoelectronics Tech. Co., Ltd., Shenzhen 518110, China;
| | - Wenyao He
- Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China; (W.H.); (L.W.); (G.Z.)
| | - Li Wang
- Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China; (W.H.); (L.W.); (G.Z.)
- Shenzhen Guohua Optoelectronics Tech. Co., Ltd., Shenzhen 518110, China;
| | - Feng Chi
- College of Electron and Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China; (Z.Y.); (F.C.); (C.Z.); (L.S.)
| | - Chongfu Zhang
- College of Electron and Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China; (Z.Y.); (F.C.); (C.Z.); (L.S.)
| | - Lingling Shui
- College of Electron and Information, University of Electronic Science and Technology of China, Zhongshan Institute, Zhongshan 528402, China; (Z.Y.); (F.C.); (C.Z.); (L.S.)
- Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China; (W.H.); (L.W.); (G.Z.)
| | - Guofu Zhou
- Institute of Electronic Paper Displays, South China Academy of Advanced Optoelectronics, South China Normal University, Guangzhou 510006, China; (W.H.); (L.W.); (G.Z.)
- Shenzhen Guohua Optoelectronics Tech. Co., Ltd., Shenzhen 518110, China;
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