Optofluidic tunable microlens by manipulating the liquid meniscus using a flared microfluidic structure

We have designed, demonstrated, and characterized a simple, novel in-plane tunable optofluidic microlens. The microlens is realized by utilizing the interface properties between two different fluids: CaCl(2)solution and air. A constant contact angle of ～90° is the pivotal factor resulting in the outward bowing and convex shape of the CaCl(2) solution-air interface. The contact angle at the CaCl(2) solution-air interface is maintained by a flared structure in the polydimethylsiloxane channel. The resulting bowing interface, coupled with the refractive index difference between the two fluids, results in effective in-plane focusing. The versatility of such a design is confirmed by characterizing the intensity of a traced beam experimentally and comparing the observed focal points with those obtained via ray-tracing simulations. With the radius of curvature conveniently controlled via fluid injection, the resulting microlens has a readily tunable focal length. This ease of operation, outstandingly low fluid usage, large range tunable focal length, and in-plane focusing ability make this lens suitable for many potential lab-on-a-chip applications such as particle manipulation, flow cytometry, and in-plane optical trapping.     

盆腔炎性包块的研究进展

为了解临床治疗盆腔炎性包块的慨况,在临床中探求疗效好、无毒副作用、易于患者接受的治疗方法,对近年来有关盆腔炎性包块的资料和文献进行归纳总结,从中医中药、西医、中西医结合几方面进行论述,为今后的临床研究提供思路。     

探讨消费者对包装设计的情感

本文首先阐述了包装设计的定义,进而引出井分析了消费者对包装设计的情感,最后倡导包装设计者如何有效地设计包装。     

现行快递包装运送方式缺乏便捷性的研究

快递行业伴随着网络购物的流行,所占邮递比例日渐增大。文章快递运送方式的不便捷性则作为一个亟待解决的问题进行研究,提出解决方向。     

利用电力系统分析综合程序开展银川电网分析计算工作的探讨

根据目前开展银川电网运行分析的需要，讨论了利用中国电力科学研究院开发的电力系统分析综合程序（PSDASP）进行电网实用计算的内容、意义、目的及基本计算分析方法，为进一步电网分析工作的开展奠定基础。     

The significance of the dielectric constant of a mixture

The above review of the experimental data on the dielectric constants of mixtures shows that the dielectric constant of a mixture cannot in general be calculated from the dielectric constants of the components.     

Improving the dielectric properties of an electrowetting-on-dielectric microfluidic device with a low-pressure chemical vapor deposited Si3N4 dielectric layer

Dielectric breakdown is a common problem in a digital microfluidic system, which limits its application in chemical or biomedical applications. We propose a new fabrication of an electrowetting-on-dielectric (EWOD) device using Si₃N₄ deposited by low-pressure chemical vapor deposition (LPCVD) as a dielectric layer. This material exhibits a greater relative permittivity, purity, uniformity, and biocompatibility than polymeric films. These properties also increase the breakdown voltage of a dielectric layer and increase the stability of an EWOD system when applied in biomedical research. Medium droplets with mouse embryos were manipulated in this manner. The electrical properties of the Si₃N₄ dielectric layer—breakdown voltage, refractive index, relative permittivity, and variation of contact angle with input voltage—were investigated and compared with a traditional Si₃N₄ dielectric layer deposited as a plasma-enhanced chemical vapor deposition to confirm the potential of LPCVD Si₃N₄ applied as the dielectric layer of an EWOD digital microfluidic system.     

On revising the definition of the dielectric loss angle

It is pointed out in this paper that, in the area of dielectric investigation, all habitually used formulae are the results of the unifying admittance calculation. In the event that a new definition is given to the loss angle in IEC-TC-15, Publication 250 (1st edition, 1969) according to the unifying admittance calculation concept, it will no longer be necessary to make any alterations to the other formulae and conclusions.     

Spatial concentration distribution analysis of cells in electrode-multilayered microchannel by dielectric property measurement

The spatial concentration distribution of cells in a microchannel is measured by combining the dielectric properties of cells with the specific structure of the electrode-multilayered microchannel. The dielectric properties of cells obtained with the impedance spectroscopy method includes the cell permittivity and dielectric relaxation, which corresponds to the cell concentration and structure. The electrode-multilayered microchannel is constructed by 5 cross-sections, and each cross-section contains 5 electrode-layers embedded with 16 micro electrodes. In the experiment, the dielectric properties of cell suspensions with different volume concentrations are measured with different electrode-combinations corresponding to different electric field distributions. The dielectric relaxations of different cell concentrations are compared and discussed with the Maxwell-Wagner dispersion theory, and the relaxation frequencies are analysed by a cell polarization model established based on the Hanai cell model. Moreover, a significant linear relationship with AC frequency dependency between relative permittivity and cell concentration was found, which provides a promising way to on-line estimate cell concentration in microchannel. Finally, cell distribution in 1 cross-section of the microchannel (X and Y directions) was measured with different electrode-combinations using the dielectric properties of cell suspensions, and cell concentration distribution along the microchannel (Z direction) was visualized at flowing state. The present cell spatial sensing study provides a new approach for 3 dimensional non-invasive online cell sensing for biological industry.     

Dynamic double layer effects on ac-induced dipoles of dielectric nanocolloids

Normal and tangential surface ionic currents around low-permittivity nanocolloids with surface charges are shown to produce three different conductive mechanisms for ac-induced dipoles, all involving dynamic space charge accumulation at the double layer∕bulk interface with a conductivity jump. However, the distinct capacitor dimensions and diffusive contributions produce three disparate crossover frequencies at which the induced dipole reverses direction relative to the bulk field. A highly conducting collapsed diffuse layer, with bulk ion mobility, renders the particle conductive and produces an ionic strength independent crossover frequency for weak electrolytes. A precipitous drop in crossover frequency occurs at high ionic strengths when charging occurs only at the poles through field focusing around the insulated colloid. A peculiar maximum in crossover frequency exists between these two asymptotes for colloids smaller than a critical size when normal charging of the diffuse layer occurs over the entire surface. The crossover frequency data for latex nanocolloids of various sizes in different electrolytes of wide ranging ionic strengths are collapsed by explicit theoretical predictions without empirical parameters.