Electroosmotic flow in microchannels is restricted to low Reynolds number regimes characterized by extremely weak inertia forces and laminar flow. Consequently, the mixing of different species occurs primarily through diffusion, and hence cannot readily be achieved within a short mixing channel. The current study presents a numerical investigation of electrokinetically driven flow mixing in microchannels with various numbers of incorporated patterned rectangular blocks. Furthermore, a novel approach is introduced which patterns heterogeneous surfaces on the upper faces of these rectangular blocks in order to enhance species mixing. The simulation results confirm that the introduction of rectangular blocks within the mixing channel slightly enhances species mixing by constricting the bulk flow, hence creating a stronger diffusion effect. However, it is noted that a large number of blocks and hence a long mixing channel are required if a complete mixing of the species is to be obtained. The results also indicate that patterning heterogeneous upper surfaces on the rectangular blocks is an effective means of enhancing the species mixing. It is shown that increasing the magnitude of the heterogeneous surface zeta potential enables a reduction in the mixing channel length and an improved degree of mixing efficiency.

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In this study, we present a theoretical and numerical investigation of electrokinetic energy conversion in short-length nanofluidic channels, taking into account reservoir resistance and concentration polarization effects. The concentration polarization effect was demonstrated through numerical modeling using the Poisson-NernstPlanck (PNP) model. In the absence of concentration polarization, the modified Onsager reciprocal relation for the electrokinetic flow through a one-dimensional (1D) nanochannel is derived from both Ohm's law and Kirchhoff's current law while considering the reservoir resistance. Based on this modified Onsager reciprocal relation and the Poisson-Boltzmann (PB) model, a theoretical model for electrokinetic energy conversion is proposed to address the importance of the reservoir resistance effect on electrokinetic energy conversion. The applicability of our proposed model is also verified through numerical modeling of the PNP model. The results calculated from our proposed model are shown to be in good agreement with those from the PNP model when the concentration polarization effect does not occur significantly at the reservoirs. The conversion efficiency and generation power are decreased when the channel resistance is not much larger than the reservoir resistance, especially for a shorter-length nanochannel (e.g., a channel several micrometers in length) with a lower electrolyte concentration and a higher surface charge density. After the concentration polarization effect becomes increased as a larger pressure gradient is applied through an ideal ion-selective nanochannel, the conversion efficiency/generation power is further decreased due to the ion depletion at the inlet reservoir, which increases the electrical resistance of the inlet reservoir or the equivalent electrical resistance of the electrokinetic energy conversion system. The onset pressure difference (or gradient) for a significant concentration polarization is identified both theoretically and numerically. In order to avoid decreases in the conversion efficiency/generation power mentioned above, some key factors such as the length of the nanochannel, the position of electrodes at the reservoirs, and the applied pressure gradient were noticed in this study.

Low temperature thin film LixMn.,O~ spinel, with x ~ 1, are fabricated for use in secondary batteries. The spinel crystal structure is obtained by in situ postdeposition annealing of the films at temperatures as low as 400"C. Such temperatures are compatible with semiconductor processing, permitting future integration of the batteries with electronics. 1-3 ~m thin LiMn204 films are tested in LiMn204/EC + DEE + LiC104/Li arrangements. They intercalate nearly one Li* ion at an average potential of 4.1 V and show very good intercalation kinetics, so that a 10 C discharge rate produces an energy density of 500 W-h per kilogram of active cathode material. These LiMn204 films show very promising cycle life, even at 55~ Films cycled more than 220 times maintain more than 70% of their original capacity. ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 132.239.1.231 Downloaded on 2015-04-13 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 132.239.1.231 Downloaded on 2015-04-13 to IP ) unless CC License in place (see abstract). ecsdl.org/site/terms_use address. Redistribution subject to ECS terms of use (see 132.239.1.231 Downloaded on 2015-04-13 to IP

Fuzzy weighted average (FWA), which can be applied to various fields such as engineering design, decision analysis, etc., and as function of fuzzy numbers, is suitable for the problem of multiple occurrences of fuzzy parameters. Additional fuzziness may be introduced in the -cut arithmetic. This paper reviews and compares discrete algorithms for the FWAs in both theoretical comparison and numerical comparisons, as opposed to the linear programming algorithms that may be efficient but require the help of linear programming software. An alternative efficient algorithm is also proposed. The algorithm introduces an all-candidate (criteria ratings) weights-replaced benchmark adjusting procedure other than a binary (dichotomy) search in the existing methods. The theoretical worst-case comparison shows that the algorithms of Guu and Guh et al. and our alternative algorithm require the same order of calculation complexity ( ), where is the number of FWA terms. Yet, the Guh et al. algorithm always requires 2 ( 1) calculations to be performed. The algorithm of Guu requires the elemental comparison complexity ( ), and is superior to the other algorithms, in the worst case. On the other hand, our alternative algorithm and Lee and Park algorithm have the same comparison complexity ( log ). Yet, our alternative algorithm requires ( ) calculation complexity which is better than ( log ) of the Lee and Park algorithm. The numerical experiments show that the algorithm of Guu and our alternative algorithm generally perform and converge faster by requiring fewer calculations than that of Lee and Park's algorithm. The alternative algorithm requires a slightly smaller number of calculations than that of the Guu algorithm, due to the use of the convergent benchmark adjustment procedure rather than a somewhat fixed binary search. Conversely, in the number of element comparisons, Lee and Park's algorithm is shown numerically generally slightly better than the alternative algorithm due to the simple binary search scheme used. The alternative algorithm also requires fewer comparisons than that of the Guu algorithm. Furthermore, in comparison of the average CPU time requirements, the ranks of the results of these algorithms are consistent with those of the algorithms for the average numbers of calculations. In general, the alternative algorithm may provide an efficient alternative algorithm to the FWAs. In the worse-case situation, the Guu algorithm still may be considered as an efficient alternative.Index Terms--cut arithmetic, fuzzy arithmetic, fuzzy number, fuzzy weighted average (FWA).

Understanding the properties of liquid confined in extended nanospaces (10-1000 nm) is crucial for nanofluidics. Because of the confinement and surface effects, water may have specific structures and reveals unique physicochemical properties. Recently, our group has developed a super resolution laser-induced fluorescence (LIF) technique to visualize proton distribution with the electrical double layer (EDL) in a fused-silica extended nanochannel (Kazoe, Y.; Mawatari, K.; Sugii, Y.; Kitamori, T. Anal. Chem.2011, 83, 8152). In this study, based on the coupling of the Poisson-Boltzmann theory and site-dissociation model, the effect of specific water properties in an extended nanochannel on formation of EDL was investigated by comparison of numerical results with our previous experimental results. The numerical results of the proton distribution with a lower dielectric constant of approximately 17 were shown to be in good agreement with our experimental results, which confirms our previous observation showing a lower water permittivity in an extended nanochannel. In addition, the higher silanol deprotonation rate in extended nanochannels was also demonstrated, which is supported by our previous results of NMR and streaming current measurements. The present results will be beneficial for a further understanding of interfacial chemistry, fluid physics, and electrokinetics in extended nanochannels.

This paper presents an investigation into two crucial aspects of microfluidic applications, namely electrokinetic focusing and switching. This study commences by modeling the electrokinetic focusing phenomenon theoretically using the potential flow theory. A new theoretical model is derived and applied to predict the width of the focused stream. The results predicted by the theoretical model are shown to be in good agreement with the experimental data. The paper then proceeds to study the electrokinetic switching functions systematically using both experimental and theoretical approaches. A new control model for ‘one-to-multiple’ electrokinetically pre-focused micro flow switches is proposed. Using this new model, the sample flow can be pre-focused electrokinetically into a narrow stream and then injected directly into the desired outlet port. The results of this study provide a useful methodology for the analysis of flow control in microfluidic devices. Finally, an electrokinetically driven micro flow cytometer utilizing electrokinetic focusing and switching effects is demonstrated. Experimental data show that the developed methods could successfully focus microparticles and direct them into any desired outlet port.

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