非均匀电场下原油乳化液脱水特性

为了提高陆上及海上原油平台的脱水效率,利用同轴圆柱电极结构开展了乳化液在非均匀电场下的脱水特性研究;通过分析水滴在非均匀电场中的极化特性,建立了水滴极化及受力模型,分别对水滴运动、聚结和破裂的动力学特性进行了分析。研究结果表明:随着非均匀系数的升高,乳化液脱水速度增大;在一定范围内提高电场非均匀系数有利于乳化液最终含水率的降低,但电场非均匀系数过高容易造成电分散。在非均匀电场中,水滴受到的介电泳力和水滴之间的偶极聚结力与电场场强、水滴半径、电场的非均匀系数成正比,与水滴距电极中心的距离和水滴之间的距离成反比。水滴电分散场强与水滴电荷面密度、水滴粒径、表面张力有关,当水滴发生荷电后,其电分散场强减小。所建立的非均匀电场脱水模型较好地解释了电脱水试验现象,可为高效电脱水器的设计提供依据。     

基于光诱导介电泳的单粒子操纵技术

在综合分析当前生物粒子微操纵技术的基础上,设计一种基于光诱导介电泳技术的微操纵芯片,并完成芯片关键部件——光电导薄膜的加工。在准静态电场条件下,对光斑操纵模式进行建模仿真,光斑光强服从高斯分布,光斑尺寸直接影响电场平方梯度的分布,随着光斑尺寸缩小电场平方的x向梯度峰值增大,而随着高度升高电场平方的x向梯度峰值急剧减小。最后通过光诱导介电泳测试平台对单粒子操纵性能进行试验验证。试验结果表明,在去离子水中,当电压峰—峰值为20 V,频率1 MHz时,粒子受负介电泳作用而远离光斑,并且在光斑模式下直径50μm的粒子移动的最大速度可达45μm/s;而在环型虚拟电极模式下能有效控制单粒子运动方向。     

Directed Assembly of Liquid Metal–Elastomer Conductors for Stretchable and Self-Healing Electronics

Growing interest in soft robotics, stretchable electronics, and electronic skins has created demand for soft, compliant, and stretchable electrodes and interconnects. Here, dielectrophoresis (DEP) is used to assemble, align, and sinter eutectic gallium indium (EGaIn) microdroplets in uncured poly(dimethylsiloxane) (PDMS) to form electrically conducting microwires. There are several noteworthy aspects of this approach. 1) Generally, EGaIn droplets in silicone at loadings approaching 90 wt% remain insulating and form a conductive network only when subjected to sintering. Here, DEP facilitates assembly of EGaIn droplets into conductive microwires at loadings as low as 10 wt%. 2) DEP is done in silicone for the first time, enabling the microwires to be cured in a stretchable matrix. 3) Liquid EGaIn droplets sinter during DEP to form a stretchable metallic microwire that retains its shape after curing the silicone. 4) Use of liquid metal eliminates the issue of compliance mismatch observed in soft polymers with solid fillers. 5) The silicone–EGaIn “ink” can be assembled by DEP within the crevices of severely damaged wires to create stretchable interconnects that heal the damage mechanically and electrically. The DEP process of this unique set of materials is characterized and the interesting attributes enabled by such liquid microwires are demonstrated.     

Aligned Immobilization of Proteins Using AC Electric Fields

Protein molecules are aligned and immobilized from solution by AC electric fields. In a single‐step experiment, the enhanced green fluorescent proteins are immobilized on the surface as well as at the edges of planar nanoelectrodes. Alignment is found to follow the molecules' geometrical shape with their longitudinal axes parallel to the electric field. Simultaneous dielectrophoretic attraction and AC electroosmotic flow are identified as the dominant forces causing protein movement and alignment. Molecular orientation is determined by fluorescence microscopy based on polarized excitation of the proteins' chromophores. The chromophores' orientation with respect to the whole molecule supports X‐ray crystal data.     

介电泳芯片的研制及不同细胞介电分离的应用

制备了包括指状交叉、城墙状和梯形的微电极阵列芯片装置.并用这些芯片探索了生物细胞的介电响应.另外观察了酵母和鸡血红细胞的迁移、旋转和融合以及几种细胞收集图片.发现了两种细胞的正、负介电泳现象,确定了这两种细胞的分离条件.讨论了两种细胞正、负介电泳的原因.利用同一芯片在相同的条件下一种细胞移向强场区(正介电泳),另一种细胞移向弱场区(负介电泳).因此可用同一芯片分离不同的细胞.有望建立一种非接触式细胞分离技术,而且在分离过程中不需要添加任何试剂.     

Manipulation of bioparticles using traveling wave dielectrophoresis: numerical approach

A typical microelectrode structure, interdigitated bar electrodes, has been developed for the selective manipulation and separation of bioparticles using traveling field dielectrophoresis effects under AC electrokinetics. This paper presents meshless numerical solutions of traveling wave dielectrophoresis for such interdigitated electrode array energized with 4-phase signal. This meshless method is based on a truncated 2D Taylor series expansion with the first three orders together with a weighted least-square approximation procedure. Dielectrophoretic forces and traveling wave forces are calculated and their applications for bioparticle manipulation and separation are discussed.     

集成阻抗识别的介电泳芯片设计及其关键工艺

以微粒的阻抗识别为目的,设计出一种三维网格阵列微电极传感器.传感器将介电泳分离与阻抗识别集成在同一芯片上.首先通过介电泳将微粒中的一种分离至测试区域,再通过阻抗信号描述微粒特性.针对芯片关键区域,提出了调节SU8曝光时间以提高阻抗测试有效信号的工艺解决方案.实验表明,SU8最佳曝光时间为70 s.对芯片性能的相关实验表明,芯片可对不同直径的乳胶微粒进行介电泳分离与阻抗识别.     

Non-linear electrohydrodynamics in microfluidic devices

Since the inception of microfluidics, the electric force has been exploited as one of the leading mechanisms for driving and controlling the movement of the operating fluid and the charged suspensions. Electric force has an intrinsic advantage in miniaturized devices. Because the electrodes are placed over a small distance, from sub-millimeter to a few microns, a very high electric field is easy to obtain. The electric force can be highly localized as its strength rapidly decays away from the peak. This makes the electric force an ideal candidate for precise spatial control. The geometry and placement of the electrodes can be used to design electric fields of varying distributions, which can be readily realized by Micro-Electro-Mechanical Systems (MEMS) fabrication methods. In this paper, we examine several electrically driven liquid handling operations. The emphasis is given to non-linear electrohydrodynamic effects. We discuss the theoretical treatment and related numerical methods. Modeling and simulations are used to unveil the associated electrohydrodynamic phenomena. The modeling based investigation is interwoven with examples of microfluidic devices to illustrate the applications.