基于介电泳的电极阵列电场仿真研究

介电泳方法被广泛地应用于微纳颗粒的分离和操纵中,实现介电泳操作的关键是设计满足所需电场分布的电极阵列.针对目前在微电极阵列设计中尚缺乏简单有效的电场解析方法的现状,提出一种基于格林公式的电极阵列电场的解析方法.首先介绍了传统介电泳和行波介电泳的概念和计算模型,分析了介电泳过程与电极上所施加的交变电压的频率和幅度的关系,然后在确立电极电势的边界条件的基础上,采用基于格林公式的电场解析方法,建立了非均匀电场的解析模型,得出不同条件下的电极阵列电场分布的仿真结果,最后利用FEMLAB有限元仿真软件对解析模型进行了对比仿真, 验证了该解析模型的可行性.基于格林公式的电场解析求解方法能够有效地提高电极阵列设计中的针对性以及缩短电极设计的时间.     

Study of high-throughput cell electrofusion in a microelectrode-array chip

A microfabricated high-throughput cell electrofusion chip with 1,368 pairs of high aspect ratio silicon microelectrodes is presented. These microelectrodes, which were distributed in six individual microscale cell-fusion chambers, were covered with titanium and gold thin film to improve their electric conductivity as well as surface hydrophobility. Six chambers having different electrode distances make the chip highly suitable for fusing cells with different sizes. A microfluidic platform was set up for flowing control, cell manipulation and also experimental observation. Cells for electrofusion were first aligned at the prearranged locations by the dielectrophoretic force between two counter-electrodes, which benefits the traverse of electric pulse through the cell–cell contacting point for electroporation. Several on-chip cell electrofusion experiments have been carried out on different kinds of animal cells and plant protoplasts. Compared with conventional electrofusion methods, higher fusion efficiency was achieved on this device for precisely forming micropores on the proximate membranes of two contacting cells, and high throughput was also obtained due to the use of a large number of microelectrodes for cell manipulation and fusion. Moreover, a much lower power supply was required for the shorter distance between two counter-electrodes.     

基于单脉冲放电的钨微细电极快速成形方法及其应用研究

在传统电火花加工的基础上,通过单脉冲放电方式,在钨细线电极的端部瞬时成形出一个微米级的微细电极。运用试验研究详尽分析了各主要加工参数,如电极材料、加工极性、工作液介质、放电持续时间和峰值电流等对微细电极的成形影响,得出了微细电极瞬时成形的基本规律。此外,在试验的基础上对微细电极成形的机理进行了初步探讨,并对成形后的电极进行了能谱分析。通过本方法可以在直径0.125 mm的钨丝端部瞬间得到长350 μm,直径30 μm左右的微细电极,用该电极成功地完成了多个微米级微细孔的加工。微细电极的尖端半径约为100 nm,可作为扫描仪器和检测仪器的微细探针。极大地提高了微细电极或探针的成形效率,有望成为微细电极和微细探针制备的有力手段之一。     

Electrochemical oxidation of hydrogen peroxide at nanoporous platinum electrodes and the application to glutamate microsensor

The electrochemical behavior of hydrogen peroxide (H₂O₂) at nanoporous platinum (Pt) thin film was investigated and the reaction of the enzymes immobilized on the electrode was examined. The nanoporous Pt underlying the enzyme layer was electrochemically deposited on Pt-Ir alloy microelectrodes in the solution consisting of hexachloroplatinic acid and a non-ionic surfactant, octaethylene glycol monohexadecyl ether (C₁₆EO₈). Glutamate oxidases were entrapped during electro-polymerization of 1,3-phenylenediamine on the nanoporous Pt microelectrodes to form a glutamate oxidase layer. The glutamate microsensors as made were compared with flat Pt-based one in terms of the performance and characteristics.     

Micro-profiles of activated sludge floc determined using microelectrodes

The microbial activity within activated sludge floc is a key factor in the performance of the activated sludge process. In this study, the microenvironment of activated sludge flocs from two wastewater treatment plants (Mill Creek Wastewater Treatment Plant and Muddy Creek Wastewater Treatment Plant, with aeration tank influent CODs of 60-120 and 15-35 mg/L, respectively) were studied by using microelectrodes. Due to microbial oxygen utilization, the aerobic region in the activated sludge floc was limited to the surface layer (0.1-0.2mm) of the sludge aggregate at the Mill Creek plant. The presence of an anoxic zone inside the sludge floc under aerobic conditions was confirmed in this study. When the dissolved oxygen (DO) in the bulk liquid was higher than 4.0mg/L, the anoxic zone inside the activated sludge floc disappeared, which is helpful for biodegradation. At the Muddy Creek plant, with its lower wastewater pollutant concentrations, the redox potential and DO inside the sludge aggregates were higher than those at the Mill Creek plant. The contaminant concentration in the bulk wastewater correlates with the oxygen utilization rate, which directly influences the oxygen penetration inside the activated sludge floc, and results in redox potential changes within the floc. The measured microprofiles revealed the continuous decrease of nitrate concentration inside the activated sludge floc, even though significant nitrification was observed in the bulk wastewater. The oxygen consumption and nitrification rate analyses reveal that the increase of ammonia flux under aerobic conditions correlates with nitrification. Due to the metabolic mechanisms of the microorganisms in activated sludge floc, which varies from one treatment plant to another, the oxygen flux inside the sludge floc changes accordingly.     

Temporal and spatial inhibitory effects of zinc and copper on wastewater biofilms from oxygen concentration profiles determined by microelectrodes

To understand the temporal and spatial toxic effect of heavy metals on the microbial activities of biofilms, microelectrodes were used to measure the inhibitory oxygen (O₂) concentration profiles resulted from the effects of zinc (Zn²⁺) and copper (Cu²⁺). Using the O₂ microprofiles as bases, the spatial distributions of net specific O₂ respiration were determined in biofilms with and without treatment of 5 mg/L Zn²⁺ or 1 mg/L Cu²⁺. Results show that microbial activities were inhibited only in the outer layer (∼400 μm) of the biofilms and bacteria present in the deeper sections of the biofilms became even more active. The inhibition caused by the heavy metals was evaluated by two methods. One was derived from the oxygen influx at the interface and the other was based on the integral of the oxygen consumption calculated from the entire O₂ profile. The two methods yielded significantly different results. We argue that the integral method results in more accurate assessment of toxicity than the surface flux determination.     

微电极针尖的制备方法

针尖工艺是针型微电极制造的关键技术.利用电生理实验室常用设备搭建了加工平台,采用阴极圆环营造出一个渐变电场,通过一组正交试验,研究了电解液浓度、腐蚀电压、通电时间等对针尖质量的影响,得到了最佳加工参数:NaCl溶液浓度为3.0g/L,腐蚀电压为5.0V,通电时间为30s,制备出符合电刺激实验要求的高质量针尖.该方法操作简单、制备时间短、成本低,适用于电生理实验中微电极尖端形态的改进.     

Electrochemical Fabrication and Electrocatalytic Properties of Nanostructured Mesoporous Platinum Microelectrodes

1. IntroductionThe electrochemical reduction of a suitable precur-sor dissolved in the aqueous domains of a homoge-neous lyotropic liquid crystalline phase (only formed athigh concentrations of non-ionic surfactants) can pro-duce a nanostructured material with a well-defined long-range mesoporous structure[1~4]. The generic applica-bility of the liquid crystal templating (LCT) techniquehas been confirmed by the production of a wide rangeof nanostructured metals and metal oxides, and otherrela…     

碳酸铅作为铅酸蓄电池电极材料的研究

根据我国已制定的攀登计划项目中关于方铅矿碳酸化转化的清洁炼铅的思想,为探讨从碳酸铅直接生产铅酸蓄电池的可行性,采用粉末微电极技术和循环伏安法研究了ＰｂＣＯ３ 转化为铅酸蓄电池电极活性物质的途径。结果表明,在不加入任何添加剂的情况下,微电极中ＰｂＣＯ３ 粉末在Ｈ２ＳＯ４ 溶液中经化学转化－ 电化学活化后,正、负极的伏安行为与文献报道的铅电极上的类似,可见,以ＰｂＣＯ３ 为电极材料制造铅酸蓄电池电极是可行的。此外,还研究了几种因素对ＰｂＣＯ３ 转化的ＰｂＳＯ４／Ｐｂ 电极性能的影响     

微机控制微电极伏安仪

本文将 APPLE-Ⅱ计算机与电化学系统联机,研制了微机控制的微电极伏安仪。该仪器除能做稳态实验外,还可以进行结果计算和处理。其电势扫描速度达到几十伏/秒,能用于较快速电势扫描的研究。自动化程度大大提高。