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双稳态电润湿；非平面；控制电极；低电压；高对比度 1

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Modeling and simulation of droplet translocation and fission by electrowetting-on-dielectrics (EWOD)

Nathan HOWELL, Weihua LI

《机械工程前沿（英文）》 2010年第5卷第4期页码 376-388 doi: 10.1007/s11465-010-0104-z

摘要： This paper discusses methods of microfluidic droplet actuation by means of electrowetting-on-dielectrics (EWOD) and provides a technique for modeling and simulating a microfluidic device by using the computational fluid dynamics (CFD) program, Flow3D. Digital or droplet microfluidics implies the manipulation of droplets on a scale of nanoliters (10 L) to femtoliters (10 L), as opposed to continuous microfluidics that involve the control of continuous fluid within a channel. The two operations in focus here are droplet translocation (moving) and droplet fission (splitting), in which the pressures and velocities within the droplet are analyzed and compared to existing works, both theoretical and experimental. The variation in the pressure of the leading and trailing faces of a droplet indicates the variation in surface energy—an important parameter that explains how a droplet will move toward a region of higher electric potential. The higher voltage on one side of a droplet reduces surface energy, which leads to an induced pressure drop, thus resulting in fluid motion. Flow3D simulations are for both water and blood droplets at voltages between 50 V and 200 V, and the droplet size, surface properties (Teflon coated), and geometry of the system are kept constant for each operation. Some peculiarities of the simulation are brought to light, such as instabilities of the system to higher voltages and fluids with higher dielectric constants, as well as the creation of a tertiary droplet when the applied voltage causes a large enough force during fission. The force distribution across the droplet provides a general understanding of the electrowetting effect and more specifically allows for a comparison between the effects that different voltages have on the forces at the droplet surface. The droplet position and mean kinetic energy of the droplet are also investigated and compared to other works, proving the dynamics of a droplet motion found here.

关键词： electrowetting-on-dielectrics (EWOD) electrowetting microfluidics droplet translocation droplet fission Flow3D dielectric constant

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Assessing the effects of different dielectrics on environmentally conscious powder-mixed EDM of difficult-to-machine

Jagdeep SINGH,Rajiv Kumar SHARMA

《机械工程前沿（英文）》 2016年第11卷第4期页码 374-387 doi: 10.1007/s11465-016-0388-8

摘要：

Electrical discharge machining (EDM) is a well-known nontraditional manufacturing process to machine the difficult-to-machine (DTM) materials which have unique hardness properties. Researchers have successfully performed hybridization to improve this process by incorporating powders into the EDM process known as powder-mixed EDM process. This process drastically improves process efficiency by increasing material removal rate, micro-hardness, as well as reducing the tool wear rate and surface roughness. EDM also has some input parameters, including pulse-on time, dielectric levels and its type, current setting, flushing pressure, and so on, which have a significant effect on EDM performance. However, despite their positive influence, investigating the effects of these parameters on environmental conditions is necessary. Most studies demonstrate the use of kerosene oil as dielectric fluid. Nevertheless, in this work, the authors highlight the findings with respect to three different dielectric fluids, including kerosene oil, EDM oil, and distilled water using one-variable-at-a-time approach for machining as well as environmental aspects. The hazard and operability analysis is employed to identify the inherent safety factors associated with powder-mixed EDM of WC-Co.

关键词： WC hazard and operability analysis (HAZOP) discharging aerosol concentration dielectrics powders

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Review of recent advances of polymer based dielectrics for high-energy storage in electronic power devices

Wenjie Sun, Jiale Mao, Shuang Wang, Lei Zhang, Yonghong Cheng

《化学科学与工程前沿（英文）》 2021年第15卷第1期页码 18-34 doi: 10.1007/s11705-020-1939-4

摘要： Polymer-based dielectric capacitors are widely-used energy storage devices. However, although the functions of dielectrics in applications like high-voltage direct current transmission projects, distributed energy systems, high-power pulse systems and new energy electric vehicles are similar, their requirements can be quite different. Low electric loss is a critical prerequisite for capacitors for electric grids, while high-temperature stability is an essential pre-requirement for those in electric vehicles. This paper reviews recent advances in this area, and categorizes dielectrics in terms of their foremost properties related to their target applications. Requirements for polymer-based dielectrics in various power electronic equipment are emphasized, including high energy storage density, low dissipation, high working temperature and fast-response time. This paper considers innovations including chemical structure modification, composite fabrication and structure re-design, and the enhancements to material performances achieved. The advantages and limitations of these methods are also discussed.

关键词： dielectric capacitors polymer-based dielectrics energy density dielectric loss working temperature frequency response

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非平面电极双稳态电润湿显示器件研究 Regular Papers-Research Articles

Han ZHANG, Xue-lei LIANG

《信息与电子工程前沿（英文）》 2019年第20卷第9期页码 1289-1295 doi: 10.1631/FITEE.1800167

摘要：双稳态电润湿显示器仅在状态切换时耗能，在状态稳定时无耗能，是一种非常有潜力的低能耗电子纸显示技术。本文设计和实现了通过常规光刻工艺制备一种非平面电极结构的双稳态电润湿器件。该器件不仅具备视频响应速度，而且有潜力实现可控的像素灰阶。与现有平面电极结构双稳态电润湿器件相比，该新型电极结构可实现更低驱动电压和更高对比度。

关键词：双稳态电润湿；非平面；控制电极；低电压；高对比度

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Surface tension of liquid metal: role, mechanism and application

Xi ZHAO, Shuo XU, Jing LIU

《能源前沿（英文）》 2017年第11卷第4期页码 535-567 doi: 10.1007/s11708-017-0463-9

摘要： Surface tension plays a core role in dominating various surface and interface phenomena. For liquid metals with high melting temperature, a profound understanding of the behaviors of surface tension is crucial in industrial processes such as casting, welding, and solidification, etc. Recently, the room temperature liquid metal (RTLM) mainly composed of gallium-based alloys has caused widespread concerns due to its increasingly realized unique virtues. The surface properties of such materials are rather vital in nearly all applications involved from chip cooling, thermal energy harvesting, hydrogen generation, shape changeable soft machines, printed electronics to 3D fabrication, etc. owing to its pretty large surface tension of approximately 700 mN/m. In order to promote the research of surface tension of RTLM, this paper is dedicated to present an overview on the roles and mechanisms of surface tension of liquid metal and summarize the latest progresses on the understanding of the basic knowledge, theories, influencing factors and experimental measurement methods clarified so far. As a practical technique to regulate the surface tension of RTLM, the fundamental principles and applications of electrowetting are also interpreted. Moreover, the unique phenomena of RTLM surface tension issues such as surface tension driven self-actuation, modified wettability on various substrates and the functions of oxides are discussed to give an insight into the acting mechanism of surface tension. Furthermore, future directions worthy of pursuing are pointed out.

关键词： surface tension liquid metal soft machine printed electronics electrowetting self-actuation

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Digital microfluidics: A promising technique for biochemical applications

He WANG, Liguo CHEN, Lining SUN

《机械工程前沿（英文）》 2017年第12卷第4期页码 510-525 doi: 10.1007/s11465-017-0460-z

摘要：

Digital microfluidics (DMF) is a versatile microfluidics technology that has significant application potential in the areas of automation and miniaturization. In DMF, discrete droplets containing samples and reagents are controlled to implement a series of operations via electrowetting-on-dielectric. This process works by applying electrical potentials to an array of electrodes coated with a hydrophobic dielectric layer. Unlike microchannels, DMF facilitates precise control over multiple reaction processes without using complex pump, microvalve, and tubing networks. DMF also presents other distinct features, such as portability, less sample consumption, shorter chemical reaction time, flexibility, and easier combination with other technology types. Due to its unique advantages, DMF has been applied to a broad range of fields (e.g., chemistry, biology, medicine, and environment). This study reviews the basic principles of droplet actuation, configuration design, and fabrication of the DMF device, as well as discusses the latest progress in DMF from the biochemistry perspective.

关键词： digital microfluidics electrowetting on dielectric discrete droplet biochemistry