A light writable microfluidic "flash memory": optically addressed actuator array with latched operation for microfluidic applications

This paper presents a novel optically addressed microactuator array (microfluidic "flash memory") with latched operation. Analogous to the address-data bus mediated memory address protocol in electronics, the microactuator array consists of individual phase-change based actuators addressed by localized heating through focused light patterns (address bus), which can be provided by a modified projector or high power laser pointer. A common pressure manifold (data bus) for the entire array is used to generate large deflections of the phase change actuators in the molten phase. The use of phase change material as the working media enables latched operation of the actuator array. After the initial light "writing" during which the phase is temporarily changed to molten, the actuated status is self-maintained by the solid phase of the actuator without power and pressure inputs. The microfluidic flash memory can be re-configured by a new light illumination pattern and common pressure signal. The proposed approach can achieve actuation of arbitrary units in a large-scale array without the need for complex external equipment such as solenoid valves and electrical modules, which leads to significantly simplified system implementation and compact system size. The proposed work therefore provides a flexible, energy-efficient, and low cost multiplexing solution for microfluidic applications based on physical displacements. As an example, the use of the latched microactuator array as "normally closed" or "normally open" microvalves is demonstrated. The phase-change wax is fully encapsulated and thus immune from contamination issues in fluidic environments.     

Charged molecular films on brownian particles: structure, interactions, and relation to stability

The interfacial film of physically adsorbed ionic amphiphilic molecules on submicron particles dispersed in water was studied by a combination of surface tension measurements, laser light scattering (LLS) and high-shear experiments in a microchannel. General features in the structure and morphology of the molecular film are identified and understood in the framework of the two-step Langmuir adsorption model deduced from the adsorption isotherm. On the basis of this approach, the phase transitions and structural ordering of the film at the solid-liquid interface are analyzed in detail. A novel methodology based on high-shear aggregation experiments subsequently analyzed by means of LLS is proposed and turns out to be able to provide significant information on the phase transitions and structural arrangements of the adsorbed molecules (in substantial agreement with the adsorption isotherm model) as well as on the resulting interactions. Particularly important for applications is the result that, with no added salt, the films on two particles can adhere/fuse, leading to aggregation as long as an uncovered (hydrophobic) patch is present (unsaturated molecular layers). In the opposite case of fully developed layers, by analyzing the mechanism of shear aggregation of charged particles in the low-salt limit, we show that, when the hydrophobic attraction is absent, short-range hydration repulsive forces dominate over Derjaguin-Landau-Verwey-Overbeek (DLVO) forces and adhesion can never be achieved even upon application of very high collision energies. Consistently, a lower limiting boundary for the hydration interaction is calculated and found to be in agreement with data in the literature.     

ZrOCl2 x 8H2O: an efficient, cheap and reusable catalyst for the esterification of acrylic acid and other carboxylic acids with equimolar amounts of alcohols

Esterifications of carboxylic acids with equimolar amount of alcohols could be efficiently catalyzed by ZrOCl(2) x 8H(2)O. Acrylate esters were obtained in good yields under solvent-free conditions at ambient temperature. The esterification of other carboxylic acids with alcohols also proceeded at ambient temperature or at 50 oC to afford esters in high yields. If the esterification was performed in toluene under azeotropic reflux conditions to remove water, both the catalytic activity of ZrOCl(2) x 8H(2)O and the rate of esterification could be increased greatly. Furthermore, in the present catalytic system, the esters could be easily separated from the reaction mixtures and the catalyst could be easily recovered and reused.     

热散焦效应对甲烷后向受激喇曼散射的影响

The conversion efficiency of stimulated Raman scattering (SRS) in CH4 is studied by using a single longitudinal mode second-harmonic Nd:YAG laser (532 nm, linewidth 0.003 cm-1, pulse-width (FWHM) 6.5 ns).Due to the heat release from vibrationally excited particles, SRS processes often suffer from the thermal defocusing effect (TDE). In view of 6.5 ns laser pulse width is much shorter than the vibrational relaxation time of CH4 molecules, TDE can only affect the SRS processes afterwards. In the cases of low laser repetition, TDE will be not serious, because it will be removed by the thermal diffusion in Raman medium before the next pulse arrives. At the laser repetition rate 2 Hz, CH4 pressure 1.1 MPa and pump laser energy 95 m J, the quantum conversion efficiency of backward first-Stokes (BS1) has attained 73%. This represents the highest first-stokes conversion efficiency in CH4. Furthermore, due to the relaxation oscillation, the BS1pulses are narrowed to about 1.2 ns. As a result, the BS1 peak power turns out to be 2.7 times that of the pump. Its beam quality is also much better and is only slightly affected by TDE. This reason is that BS1 represents a wave-front-reversed replica of the pump beam, which can compensate the thermal distortions in Raman amplify process. Under the same conditions, but pump laser repetition rate as 10 Hz, the conversion efficiency of BS1 goes down to 36% due to TDE. From this study, we expect that a well-behaved 630 nm Raman laser may be designed by using a closed CH4/He circulating-cooling system, which may have some important applications.     

新型阳离子光引发剂[4-(2-羟基-3-丁氧基-1-丙氧基)苯基]苯碘鎓-六氟锑酸盐的合成及光敏性能的研究

以丁基缩水甘油醚和苯酚为起始原料,进行开环缩合反应制得1-丁氧基-3-苯氧基丙-2-醇.再与羟基对甲苯磺酰氧基苯反应得到[4-(2-羟基-3-丁氧基 -1-丙氧基)]二苯碘鎓-六氟锑酸盐(简称BPI·SbF₆),产率达79%.用¹HNMR、UV、IR和元素分析对其结构进行了分析.初步研究了以BPI·SbF₆为阳离子光引发剂的脂肪族环氧(CY179)感光体系的感光特性,结果表明CY179/BPI·SbF₆感光体系有一定的后固化活性.     

Fabrications of hollow nanocubes of Cu(2)O and Cu via reductive self-assembly of CuO nanocrystals

In this work, a template-free synthetic approach for generating single-crystalline hollow nanostructures has been described. Using the small optical band-gap cuprous oxide Cu(2)O as a model case, we demonstrate that, instead of normally known spherical aggregates, primary nanocrystalline particles can first self-aggregate into porous organized solids with a well-defined polyhedral shape according to the oriented attachment mechanism, during which chemical conversion can also be introduced. In contrast to the spherical aggregates, where the nanocrystallites are randomly joined together, the Cu(2)O nanocrystallites in the present case are well organized, maintaining a definite geometric shape and a global crystal symmetry. Due to the presence of intercrystallite space, hollowing and chemical conversion can also be carried out in order to create central space and change the chemical phase of nanostructured polyhedrons. It has been revealed that Ostwald ripening plays a key role in the solid evacuation process. Using this synthetic strategy, we have successfully prepared single-crystal-like Cu(2)O nanocubes and polycrystalline Cu nanocubes with hollow interiors. For the first time, we demonstrate that nanostructured polyhedrons of functional materials with desired interiors can be synthesized in solution via a combination of oriented attachment and Ostwald ripening processes.     

CE-LIF coupled with flow cytometry for high-throughput quantitation of fluorophores in single intact cells

We report a method of coupled CE-LIF detection with flow cytometry for high-throughput determination and quantitation of fluorophores in single intact K562/S (KS) cells. The membrane properties of KS cell including fluophore transport rate and apparent permeability coefficient were further quantitatively characterized. The method has advantages for accurate quantitation and unique capacity of high-throughput analysis. The strategy will be useful for the quantitation of fluorophores in the intact cells, such as measurement of multidrug resistance, quantitation of specific protein expression, and quantitative characterization of protein and enzyme functions.     

Dynamics of water confined in the interdomain region of a multidomain protein

Molecular dynamics simulations are performed to study the dynamics of interfacial water confined in the interdomain region of a two-domain protein, BphC enzyme. The results show that near the protein surface the water diffusion constant is much smaller and the water-water hydrogen bond lifetime is much longer than that in bulk. The diffusion constant and hydrogen bond lifetime can vary by a factor of as much as 2 in going from the region near the hydrophobic domain surface to the bulk. Water molecules in the first solvation shell persist for a much longer time near local concave sites than near convex sites. Also, the water layer survival correlation time shows that on average water molecules near the extended hydrophilic surfaces have longer residence times than those near hydrophobic surfaces. These results indicate that local surface curvature and hydrophobicity have a significant influence on water dynamics.     

Effect of water on the performance of Pd-ZSM-5 catalysts for the combustion of methane

Palladium-based catalysts were prepared using impregnation （I） and ion-exchange method （E） with ZSM-5 as support. Pd-ZSM-5（I） and Pd-ZSM-5（E） catalysts presented the high activity for the combustion of methane. The order of activity was consistent with Brcnsted acidity of the catalysts： Pd-ZSM-5（I）〉Pd-ZSM-5（E）. It was shown by FT-IR that methane was adsorbed on the acidic bridging hydroxyl groups of ZSM-5-supported Pd catalysts. The effect of water on the activity of Pd-ZSM-5 was investigated. The inhibition effect of water on the conversion of methane was observed. However, water promoted the stability of Pd-ZSM-5 obviously during extended time periods. XPS measurement showed that Pd/Si ratio near the surface of Pd-ZSM-5（E） decreased more pronouncedly with time in dry stream than that of Pd-ZSM-5（I）, this is attributed to the dispersion of Pd into the micropores. The addition of water, however, retarded Pd dispersion. And high partial pressure of methane reduced this effect of water vapor. The decrease in activity during the stability test can be explained on the basis of the reduction of Pd/Si ratio.