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The noncontact and wide-band characteristics of the ultrasonic signal excited by the laser make it widely used in nondestructive detection. In this paper, the finite element method is used to simulate multiple ultrasonic signal modes and the responses of them to metal defects. The simulation shows that the changes of excited Rayleigh-wave (RW) and shear-wave (SW) can be used to research the surface crack and internal defect of the sample respectively. By analyzing the reflected wave of RW and SW at the inspection point, the effects of surface crack and internal defect on the ultrasonic signals of the two modes are quantitatively compared. The results show that the time delay of the Rayleigh echo has a linear relationship to the width and transverse position of the crack, and the peak-valley difference of Rayleigh echo at the inspection point and the crack depth can also be fitted linearly. In addition, the Y component displacement of the bottom reflected SW also decays with the change of the internal defect. This simulation model provides a theoretical basis for further experimental verification basis.

Non-collinear stimulated Brillouin scattering (SBS) amplification can obtain high peak power Stokes output while ensuring the stability, but the frequency mismatch reduces the energy conversion efficiency of the system. In this paper, a dual-frequency pulse laser based on acousto-optic crystal modulation is designed. The output pulse pair can be used as pump and Stokes light, respectively, which realizes the active frequency matching of the gain medium Brillouin frequency shift during the SBS amplification process and helps to maintain ideal energy conversion efficiency. The dual-frequency laser finally produced a laser pulse pair with a pulse width adjustment range of 100 ps-50 ns, a frequency shift range of 0 GHz-2 GHz, and the polarization extinction ratio (PER) reaches 20.82dB.

This study investigated the effects of a helium cold atmospheric plasma (CAP) on the bonding performance and surface modification of the caries-affected dentin (CAD). Artificial CAD was created by pH-cycling. The microtensile bond of CAD were examined before and after CAP treatments at 24 h and after 2-year aging. The effects of surface modification were studied with contact-angle measurement, scanning electron microscopy and X-ray photoemission spectroscopy. Thirty-second CAP treatment increased the immediate bond strength of CAD to a level that was statistically the same as sound dentin, and slowed the aging process of the bonding as well. The CAP treatment induced modified CAD surface with increased wettability, cleaner appearance, and increased percentage of the mineral-associated elements and oxygen. This research demonstrated that the helium CAP jet treatments of 30 s and 45 s improved the bond strength of the artificial CAD, and was considerably effective in its surface modification.

A 37-core optical fiber with 14 air holes is proposed in this paper. This optical fiber can transmit the fundamental mode and part of the second mode. Effects of structure parameters on effective refractive index, bending loss and effective area of the fundamental mode HE11 and the second-order mode HE21 are investigated systematically. By adjusting the structure parameters, at wavelength of 1550 nm and bending radius of 5 cm, the effective mode field area of the fundamental mode is 1776.289 μm2 , and the bending loss is 4.656×10-5 dB/m. Due to the flexibility of multi-core structure, it is significant for theoretical research and practical manufacturing.

A novel kind of Cu-based catalytic membrane reactor (CMR) has been developed for the efficient reduction of p-nitrophenol (p-NP) to p-aminophenol (p-AP) in a continuous flow-through system. The CMR is prepared by the composite of MOF-derived nanoporous Cu/Cu2O networks and a porous matrix of nylon film. In this process, the pre-synthesized Cu-MOF-nanosheets are deposited onto a porous nylon film via filtration, and then the composite membrane is in-situ reduced by NaBH4 in the liquid phase, producing nanoporous Cu/Cu2O networks/nylon composite membrane. Remarkably, the nanoporous Cu/Cu2O networks exhibit fluffy structure with multidimensional porosity, which shows relatively high mass transportation ability and excellent catalytic activity. Therefore, the nanoporous Cu/Cu2O networks/nylon composite membrane can work as highly efficient and stable CMR, which can continuously convert over 95% of p-NP to p-AP in an 8 h test (8 mL/min) without obvious structure change and deactivation. This new type two-dimensional MOF-derived CMR offers an effective and convenient continuous catalytic process from p-NP to p-AP, which would have a potential application in this industrial reduction reaction.

Due to the oil-water layers crisscrossing in the oilfield exploitation, oil production engineers keep on research more and more agent with selective water-plugging/profile modifying in order to reduce water and increase oil. In this paper, researchers use the oil soluble resin as the main raw material, and develop the emulsified oil soluble resin selective plugging agent, and the oil soluble resin is emulsified and dispersed by special processing technology to form a stable oil-in-water emulsion. The emulsion can be mixed with any proportion of water, has good fluidity and easy injection into the layer. After entering the layer, the stability of the system is lost under the action of special demulsifiers, contacting rocks, and the formation temperature, the oil-soluble resin occupy the space to plug by the aggregation and mutual adhesion of the particles to form clusters, or they are attached to the rock surface. By changing the wettability of rock surface and forming mechanical blockage of water flow, the purpose of reducing water production and increasing crude oil production is achieved. The experimental results show that the breakthrough pressure of cores with different permeability can be increased by an average of more than 10 times, and the plugging rate of sandstone cores can reach 93% by using 25% emulsified oil soluble resin selective plugging agent. And the plugging rate of water displacement with 300 times pore volume of core is stable. Because the system is insoluble in oil and water, it has self-selectivity after injection. Through the field application of six times sandstone reservoir and once limestone reservoir, the remarkable effect of increasing oil production and reducing water is obtained, which provides a new technical means for water plugging in reservoir and increasing oil production and reducing water production in single well.

Non-spherical metal nanomaterials such as noble metal or transition metal dichalcogenides and MXenes have been employed in different biomedical facets. Because the biological properties of these nanocompounds are governed by their architecture and composition, such factors should be considered prior to their adoption for clinical use. The architecture of metal-based nanomaterials affects cell viability by virtue of the variable geometry of these nanomaterials as well as their physicochemical interactions with mammalian cell membranes. In the present review, the effects of parameters such as interfacial interaction and aspect ratio on cellular uptake of non-spherical metallic nanomaterials will be discussed. The application of these nanomaterials as biosensors, in cancer diagnosis and therapy, tissue engineering and regenerative medicine will also be thoroughly reviewed.

We report a facile method to fabricate a compact Au nanoparticle film with the assistance of surfactants. First, the dodecanethiol-coated Au nanoparticles were floated on the surface of the toluene/acetonitrile solvent mixture and adjusted to an expanded dispersion by changing the mixture ratio. Silicone oil was then added as a surfactant to compress the floating nanoparticles from the original loose status to a closely packed arrangement that produced a compact nanoparticle film. The relationship of the compressed film area to the silicone oil concentration was plotted and compared to the surface tension curve of silicone oil. The results were quite consistent, suggesting that the surface location of the surfactant induced the nanoparticles' compression. The resulting nanoparticle film was uniform and sufficiently robust to be transferred to the solid substrate. Moreover, it could be applied to catalyze the reduction of 4-nitrophenol. Our study indicated that the utilization of surfactants to compress the well-dispersed nanoparticles on the liquid surface is a simple, fast, and adaptable method of fabricateing compact nanoparticle films with great promise for future applications.

We have developed a rapid and convenient method for fabricating metal-organic framework (MOF) and infinite coordination polymer (ICP) nanosheets by spraying the atomized solution of metal ions onto the organic ligand solution. Nanosheet formation could be attributed to the anisotropic diffusion of metal ions in the ligand solution, which may give rise to a lateral interface of metal ions and organic ligands, where the crystals tend to grow laterally in the form of nanosheets. Three kinds of Zn- and Cu-based MOF nanosheets and two kinds of Co-based ICP nanosheets have been successfully obtained by spraying under mild conditions. The two-dimensional structures of nanosheets with a nanometer thickness and a homogeneous size can be evidenced by scanning electron microscopy, atomic force microscopy, X-ray diffraction, Brunauer-Emmett-Teller, and Fourier transform infrared spectroscopy measurements. Furthermore, the fabricated ICP nanosheets have exhibited efficient catalytic performance for the conversion of CO2 to high-value-added chemicals. This spray technique simplifies the nanosheet production process by industrialized means and enhances its controllability by the fast liquid-liquid interfacial fabrication, thus allowing access to the industrialized fabrication of MOF and ICP nanosheets.

Metal-based nanoentities, apart from being indispensable research tools, have found extensive use in the industrial and biomedical arena. Because their biological impacts are governed by factors such as size, shape, and composition, such issues must be taken into account when these materials are incorporated into multi-component ensembles for clinical applications. The size and shape (rods, wires, sheets, tubes, and cages) of metallic nanostructures influence cell viability by virtue of their varied geometry and physicochemical interactions with mammalian cell membranes. The anisotropic properties of nonspherical metal-based nanoarchitectures render them exciting candidates for biomedical applications. Here, the size-, shape-, and composition-dependent properties of nonspherical metal-based nanoarchitectures are reviewed in the context of their potential applications in cancer diagnostics and therapeutics, as well as, in regenerative medicine. Strategies for the synthesis of nonspherical metal-based nanoarchitectures and their cytotoxicity and immunological profiles are also comprehensively appraised.

The tin–bismuth eutectic alloy possesses anomalous physicochemical properties that are dependent on temperature. This paper reports the interfacial reaction and growth behavior of the intermetallic compound (IMC) layer during the dissolution of solid copper in liquid eutectic tin–bismuth at 673–823 K under the influence of the structural transition of liquid eutectic tin–bismuth. The structural transition markedly affected the dissolution rate constant of solid copper and the growth rate of the IMCs. Correspondingly, the application of the liquid structural transition significantly decreased the activation energy of dissolution and increased the apparent activation energy for IMC growth. Moreover, two major roles of elemental Bi on the formation and growth of the IMCs were suggested.

In recent years, translational plasma medicine (TPM), as a novel application area of plasmas, has attracted much attention of experts from both academic and clinical fields. State-of-the-art of the lab-scale research and clinical trials of the cold atmospheric plasmas (CAPs) in the stomatology are reviewed in detail from the direct and indirect applications of the CAPs. Based on the discussions concerning the relationship between the plasma stomatology and the plasma medicine, it is indicated that it would be an important reference for promoting the TPM starting from the fundamental and application studies in the field of dentistry, which is also one of the most three promising application fields of plasma medicine.

This work has mainly investigated the influence of the solvent on the nanoparticles distribution in digestive ripening. The experiments suggested that the solvents played a key role in digestive ripening of Au nanoparticles (Au NPs). For the benzol solvents, the resulting size distribution of Au NPs was inversely related to the solvent polarity. It may be interpreted by the low Gibbs free energy of nanoparticles in the high polarity medium, which was supposedly in favor of reducing the nanoparticles distribution. Through digestive ripening in the highly polar benzol solvent of p-chlorotoluene, monodisperse Au NPs with relative standard deviation (RSD) of 4.8% were achieved. This indicated that digestive ripening was an effective and practical way to prepare high-quality nanoparticles, which holds great promise for the nanoscience and nanotechnology. Graphical AbstractThe polarity of benzol solvent plays significant role in obtaining high-quality monodisperse Au nanoparticles. Electronic supplementary material The online version of this article (doi:10.1186/s11671-016-1797-7) contains supplementary material, which is available to authorized users.

The compensation effect of expansive agent on shrinkage of self-compacting concrete (SCC) are studied. The deformation of Concrete was tested by concrete comparator, and the qualitative and quantitative analysis of hydration products were done by X-ray diffractometer (XRD). The results show that the dosages of mineral admixture and curing conditions affect the application results of expansive agents markedly. SCC samples containing expansive agent cured in the water are expanding within the test time. In the case of watering condition and natural curing condition, the samples are always shrinkage within test time, but mineral admixtures have a good effect to resist the shrinkage of SCC. Microstructure analysis show that ettringite content is reduced slightly due to the reduction of the alkalinity of SCC resulted by more mineral admixture. However, when at water curing condition, humidity inside SCC is much higher, which makes ettringite content larger even though with more mineral admixture. So, curing is the most important factors for the micro-expansion of SCC containing expansive agent.

The conventional TZM alloy plates have limited manufacture and application due to the lacking of enough mechanical property. To resolve this question, La doped TZM alloy plate was made by the powder metallurgy. With solid-solid rare La2O3 doping, sintering, hot rolling, warm rolling and cold rolling, the molybdenum alloy La-TZM plates were got. This kind of TZM alloy has better properties in both strength and elongation. The tensile strength of La-TZM alloy is 1038 MPa, and the elongation is 10.4%. Metallography test and scanning electron microscopy (SEM) are used to examine the microstructure of the La-TZM alloy plate specimen.

Based on the profound application, the Co3O4 was chosen to be research object; the optimized dispersing condition was studied and determined as: dosage of Co3O4 nano particle varied from 0.01 to 0.02mg/ml, sodium citrate was determined to be dispersing adjuvant with a dosage of 0.0005g/ml, ultrasonic time: 10min, and pH value was 7 to 8 when the Zeta potential was –57.1mv. After a detailed discussion of size distribution and dispersing condition, the size distribution of Co3O4 nano particle was measured with Malvern Nano Zetasizer to be 217nm.

The scarcity and noble indium and platinum (Pt) are important elements in photoelectric nanomaterials. Therefore, development of low cost alternative materials to meet different practical applications is an urgent need. Two-dimensional (2D) layered graphene (GE) with unique physical, mechanical, and electrical properties has recently drawn a great deal of attention in various optoelectronic fields. Herein, the large scale (21 cm × 15 cm) high-quality single layer graphene (SLG) and multilayer graphene on a flexible plastic substrate PET were controllably prepared through layer-by-layer (LBL) transfer using the thermal release adhesive transfer method (TRA-TM). Transmission and antibending performance based on PET/GE were superior to traditional PET/ITO. The square resistance of a nine-layer graphene electrode reached approximately 58 Ω. Combined with our newly developed and highly effective Fe3O4@RGO (reduced graphene oxide) catalyst, the power conversion efficiency of the dye-sensitized solar cell (DSC) using flexible PET/GE conductive substrate was comparable to that of the DSC using the PET/ITO substrate. The desirable performance of PET/GE/Fe3O4@RGO counter electrodes (low-cost indium- and platinum-free counter electrodes) is attributed to the interfacial compatibility between 2D graphene composite catalyst (Fe3O4@RGO) and 2D PET/GE conductive substrate. In addition, DSCs that use only PET/GE (without Fe3O4@RGO catalyst) as counter electrodes can also achieve a photocurrent density of 6.30 mA cm(-2). This work is beneficial for fundamental research and practical applications of graphene and graphene composite in photovoltaics, photocatalytic water splitting, supercapacitors.

This study investigated the microstructural stability of Bi–Sb20 alloy under the influence of liquid structural transition combined with repeated melting. Liquid structural transition rendered the solidified microstructure dendritic regardless of the number of times the alloy was remelted, whereas the morphology of grains solidified from the original melt changed from equiaxed crystal to dendrite as the number of recycling times increased. Liquid structural transition improved the crystalline quality of the Bi–Sb alloy and decreased the strain in the lattice. Moreover, the microhardness of the samples after liquid structural transition remained steady at approximately 520 MPa for the different recycling times, while it obviously increased with the recycling times before liquid structural transition. These observations indicated that the microstructural stability and Vickers microhardness of the Bi–Sb20 alloy can be controlled through liquid structural transition.

In contrast to the traditional interpretation of shear bands in sand as a bifurcation problem in continuum mechanics, shear bands in sand are considered as high-strain phase (plastic phase) of sand and the materials outside the bands are still in low-strain phase (elastic phase), namely, the two phases of sand can coexist under certain condition. As a one-dimensional example, the results show that, for materials with strain-softening behavior, the two-phase solution is a stable branch of solutions, but the method to find two-phase solutions is very different from the one for bifurcation analysis. The theory of multi-phase equilibrium and the slow plastic flow model are applied to predict the formation and patterns of shear bands in sand specimens, discontinuity of deformation gradient and stress across interfaces between shear bands and other regions is considered, the continuity of displacements and traction across interfaces is imposed, and the Maxwell relation is satisfied. The governing equations are deduced. The critical stress for the formation of a shear band, both the stresses and strains inside the band and outside the band, and the inclination angle of the band can all be predicted. The predicted results are consistent with experimental measurements.

Non-stoichiometric Ni1.95Mn1.42Ga0.63 (at.%) single crystals with 20 mm diameter and 60 mm length were grown by the Bridgman method with a growth rate of 3 mm/h in argon atmosphere. The martensitic transformation starting temperature was obviously increased compared with that of stoichiometric Ni2MnGa. Although the Ni1.95Mn1.42Ga0.63 single crystal exhibited no obvious magnetically controlled shape memory effect along any direction, ∼6.5% of thermally controlled shape memory effect was detected along the c-axis in Ni1.95Mn1.42Ga0.63 single crystal, and the recovery temperature was up to 473 K, making possible its development as a new candidate of high-temperature shape memory alloys. The compressive strength and the fracture strain of single crystal specimens were measured to be 400 MPa and 19%. Based on the microstructure studied by use of both optical microscope and transmission electron microscope, the mechanism of the high-temperature thermally controlled shape memory effect in this alloy is presented in this paper.

Co-Ni alloys exhibit g(fcc)®e(hcp) martensitic transformation and show reversible induced strain under applied magnetic field, which means they are potential magneto-shape-memory materials. Polystalline of Co-Ni alloys with varied Ni content were prepared. The g(fcc)®e(hcp) martensitic transformation and shape memory effect (SME) of Co-Ni alloy were studied. The influences of Ni content and deformation temperature on SME were discussed. The shape recovery rate and recoverable strain decrease with the increase of Ni content.

The effects of cobalt content on the stacking fault probability (P sf ) determined by means of X-ray diffraction profile analysis and associated with the starting temperature of Y → e transformation (M S ) and the strain-hardening exponent (n) etc, have been investigated in Fe-Mn-Si-Cr-Ni based alloys with four different contents of Co from 0.39% to 3.93%(wt). The results show that M S and n increase with increasing Co content which is related to the increase of the stacking fault probability owing to the addition of cobalt. Addition of proper content of cobalt in Fe-Mn-Si-Cr-Ni alloy can improve its SME.

As micro-actuator materials, TiNi shape memory alloy thin films with substrate are used more and more in MEMS field. The residual stress in Ti-rich TiNi thin films with silicon substrate prepared by the magnetron-sputtering technique is measured by both X-ray glancing and contour method. The influence of crystallization annealing temperature and film thickness on the residual stress is tested. It is shown that the tensile residual stress decreases from 106 to 37 MPa with increasing annealing temperature from 723 to 923 K. However, it increases again above 1023 K. While increasing the film thickness from 2.4 to 6.5 \\micron, the residual stress reduces from 323 to 80 MPa. A lot of beautiful sunflower-like structures in crystal grains are observed by OM and TEM. The origin of the residual stress and its affecting factors are discussed. The thermal stress during cooling after annealing is the main factor resulting in tensile stress and the formation of martensite phase will release a part of tensile stress.

The annealing textures were analyzed by means of an ODF software in an Fe-27Mn-6Si-5Cr alloy wire annealed at various temperatures from 873 ∼ 1223 K. At the same time, the shape-recoverable degrees of the wire specimens were measured by tensile strain at room temperature followed by recovery heating. A nearly unique (001 ) texture appears in the wire specimen annealed at 973 K, in which the highest shape recovery ratio is obtained. A synthesis orientation factor S has been definded as a parameter for estimating the tendency for polycrystalline materials to stress-induced martensitic transformation. The reason for the influence of texture on the shape memory effect is discussed.

The fiber textures for various annealing temperature were determined by XRD and analyzed by means of orientation distribution function (ODF) software in an Fe-27Mn-6Si-5Cr alloy wire. At the same time the shape recoverable degree of the wire specimens annealing at different temperatures from 873 to 1223K was measured by tensile strain at room temperature after heating to recover A nearly unique texture appears in the wire specimen annealed at 973K, in which the highest shape recovery ratio is obtained correspondingly. The reason concerning the influence of the texture on the shape memory effect is discussed.

The influence of some microstructure parameters and characteristics ofγ-phase e.g. Stacking fault probability, grain size and texture etc one-martensitic transformation, shape memory effect and other macro-behaviours in Fe-Mn-Si based alloys are reviewed.

Recently Fe-Mn-Si based shape memory alloys have been studied intensely. Unlike Ni-Ti and Cu-based alloys, the shape memory effect(SME) in Fe-Mn-Si based alloys is often associated with the stress induced martensite by the movement of preferred partial dislocation and its reverse motion during heating. In general, there are two effective ways to improve SME in Fe-Mn-Si alloys: (1) increasing the strength of matrix to inhibit the permanent slip of perfect dislocations to austenite during a shape change and (2) reducing the stacking fault energy to enhance the movement of partial dislocations. For Fe-Mn-Si-Re (rare earth element), Hsu suggested that Re may diminish the stacking fault energy, increase the amount of thermal or stress-induced martensite, lower the T{sub N} temperature of austenite and strengthen austenite. Consequently, the addition of rare earth element in Fe-Mn-Si may significantly improve the SME. In the present study rare earth elements were added to the Fe-Mn-Si alloy in order to investigate their effect on the shape memory effect.

As an important parameter in Fe-Mn-Si based shape memory alloys, the stacking fault probability of {gamma}-phase, P{sub sf}, has been determined by means of X-ray diffraction profile analysis and connected with some macro-behavior such as the starting temperature of the thermo-induced {gamma} {yields} {var_epsilon} transformation, M{sub s}, the critical stress required for inducing {var_epsilon}-martensite, {sigma}{sub M}, the strain-hardening exponent, n, etc. It is revealed that a linear relationship between M{sub s} and the reciprocal of P{sub sf} is established as M{sub s} = 372 {minus} 0.113/P{sub sf}, and also between {sigma}{sub M} and the reciprocal of P{sub sf}, as {sigma}{sub M} = 29 + 0.212/P{sub sf}. It is shown that the strain-hardening exponent n changes monotonically with P{sub sf}. Adding Cr or N, and increasing the content of Mn in a Fe-30Mn-6Si alloy will decrease P{sub sf}, resulting in the reducing of M{sub s} and n, and the increasing of {sigma}{sub M}. The existence of quenched-in vacancies will promote the enhancement of P{sub sf}, that leads to the increase in M{sub s}. The variation of {gamma}-grain size has no obvious effect on P{sub sf}, so that it does not affect the M{sub s} temperature. The thermo-mechanical cycling will increase P{submore » sf}, in turn will lower {sigma}{sub M} and increase n, so that the shape memory effect is improved. The possible mechanism is discussed.« less

Adding a small amount of nitrogen in a Fe-30Mn-6Si alloy increases the degree of shape recovery slightly, this is attributed to the strengthening of the matrix by nitrogen atoms. The critical stress for the formation of {var_epsilon}-martensite for the alloy containing nitrogen is slightly higher than that of the alloy without nitrogen. Both the strain-hardening exponent and the probability of stacking fault of the former are smaller than that of the latter. The degrees of shape recovery in both alloys are improved remarkably by the thermo-mechanical training which may be due to the increase of stacking faults during the training cycle resulting in matrix hardening.

Single-crystalline CaCO(3) nanotablets are synthesized in large quantities through oriented attachment of pristine nanoparticles. The prepared nanotablets can serve as genuine building blocks for the construction of nacreous inorganic-organic hybrids, through which freestanding films and monoliths with tunable composition and mechanical properties are fabricated. These newly available CaCO(3) crystal tablets may also serve as a starting platform for future CaCO(3) research.

Polymers that contain conjugated molecules can change their index of refraction upon bonding with high explosive molecules. These polymers can be incorporated into micro-ring resonators as trace explosive sensor. Since the resonator cavity itself is made of sensing material, the detection is intrinsic, which may lead to higher sensitivity and faster response than other fiber optic chemical sensors. Photobleaching was used for the fabrication of the microrings resonators. The sensor has shown ppb level of sensitivity to the vapor of an explosive stimulant 2,4- dinitrotoluene and is insensitive to common chemical pollutants including nitrates, sulfates and phosphates.

We report the first study of gas phase silicon micromachining using pure bromine trifluoride (BrF/sub 3/) gas at room temperature. This work includes both the design of a new apparatus and etching characterization. Consistent etching results and high molecular etching efficiency (80%) have been achieved by performing the etching in a controlled pulse mode. This pure gaseous BrF/sub 3/ etching process is isotropic and has a high etch rate with superb selectivity over silicon dioxide (3000:1), silicon nitride (400-800:1) and photoresist (1000:1). Moreover, gaseous BrF/sub 3/ etching has also been demonstrated in surface micromachining process, where silicon nitride channels and membranes using polysilicon as the sacrificial layer have been successfully fabricated.

We present here the first surface-micromachined, normally closed, in-channel, Parylene check valve. This device is fabricated monolithically on a silicon substrate using a five-layer Parylene process. The operating structure of the check valve is a circular sealing plate on top of a ring-shaped valve seat. The sealing plate is center-anchored on top of a chamber diaphragm that is vacuum-collapsed to the bottom of the chamber in order to achieve a normally closed position. A thin gold layer on the roughened valve seat surface is used to reduce stiction between the sealing plate and the valve seat. We have achieved an in-channel check valve with a cracking (opening) pressure of 20/spl sim/40 kPa under forward bias and no measurable leakage under reverse bias up to 270 kPa. Using this design, this valve performs well in two-phase microfluidic systems (i.e. microchannel flows containing gas, liquid, or gas/liquid mixture).

Physicochemical properties of liquid metals have great impact on many technological processes. Anomalies in liquid structure of metals are affected by temperature at constant pressure. This study investigated the dissolution kinetics of solid Cu in liquid Sn under the influence of structural transition of liquid Sn at temperatures varying from 673 K to 823 K. Structural transition significantly affected the dissolution rate constant of solid Cu. Correspondingly, application of liquid structural transition significantly decreased the activation energy of dissolution and the apparent activation energy of diffusion.

We report here a surface micromachined leakage proof Parylene MEMS check valve that has nearly ideal performance. This new check valve has a unique design that its valve membrane has a sealing ring directly deposited on, and hence in direct contact with, the gold-coated valve seat. The adhesion between Parylene and gold is studied along with the reduction of adhesion of the sealing ring to the valve seat when self-assembled monolayer (SAM) coatings are used on gold. Testing results clearly demonstrate the effectiveness of SAM coating. Experiments show that the valves have no observable leakage in the reverse flow direction up to 30 psi and a cracking pressure less than 1 psi in the forward flow direction. Integration of this valve with microchannels in a microfluidic system is also demonstrated. Testing shows the in-channel check valve also has nearly ideal performance under both forward and reverse flow.

Two generations of check-valved silicone rubber diaphragm pumps are presented. Significant improvements have been made from pump to pump including the design and fabrication of a double-sided check valve, a bossed silicone membrane, and silicone gaskets. Water flow rates of up to 13 ml/min and a maximum back pressure of 5.9 kPa were achieved through pneumatic operation with an external compressed air source. Using a custom designed solenoid actuator, flow rates of up to 4.5 ml/min and a maximum back pressure of 2.1 kPa have been demonstrated.

In this paper, we present our development of a MEMS chip with an overhanging polymer microcapillary 2.5 mm in length and with a 5 /spl mu/m/spl times/10 /spl mu/m orifice size at the tip. The fabricated chips have been successfully interfaced with a mass spectrometer (MS) to validate electrospray ionization (ESI) for biochemical analysis. The prediction of a reduction in Taylor cone size has also been observed with real time ESI fluid visualization from our chip. Built-in micro particle filters and centimeter long serpentine microchannels were fabricated on the chip with a low temperature process by using the Parylene polymer as a structural material, aluminum and photoresist as sacrificial layers, and bromine trifluoride (BrF/sub 3/) gas phase etching for final microcapillary releasing. The use of an overhanging polymer structure adds a new a level of mechanical robustness that was never achievable with other thin films. Functionality of our device was proven by consistent detection of myoglobin in a 200 nM solution at a flow rate of 35 nL/min and a voltage potential of 1.5 kV. This MS interface chip represents vital and significant improvements in MEMS process technology and MS functionality with respect to the silicon nitride (Si/sub x/N/sub y/) ESI nozzles previously reported.

This paper presents a micro check valve that features a bulk-micromachined valve seat (with an orifice) and a new twist-up tethered Parylene-membrane. The twist-up tethers allow large membrane displacement, and thereby reduce membrane-induced flow resistance to a negligible level. Testing results confirm the excellent performance of our valves. For example, the valves have low cracking pressures (less than 0.5 kPa for nitrogen), high reverse pressure (seater than 600 kPa) and low reverse leakage (undetectable with a 0.2 ml/min flow meter resolution). Fluid flow models and analysis of the performance characteristics of the micro valves are presented.

Several particle membrane filters (8/spl times/8 mm/sup 2/) with circular, hexagonal and rectangular through holes are reported. By varying hole dimensions from 6 to 12 /spl mu/m, opening factors from 4 to 45% are achieved. In order to improve the filter robustness, a composite silicon nitride/Parylene membrane technology is developed. More importantly, fluid dynamic performance of the filters is also studied by both experiments and numerical simulations. It is found that the gaseous flow through the filters depends strongly on opening factors, and the measured pressure drops are much lower than that from numerical simulation using the Navier-Stokes equation. Interestingly, surface velocity slip can only account for a minor part of the discrepancy. This suggests that a very interesting topic for micro fluid mechanics research is identified.

Recent progress in the development and application of highly active, highly thermally stable, and low optical loss electro-optic polymers is presented. Nonlinear optical chromophores with large molecular nonlinearities and high thermal and chemical stabilities are covalently attached to optical grade polyimides to form side-chain polymers with electro-optic coefficients as high as 45 pm/V and lifetime over 10 6 hours at 100 degrees Celsius. Cladding polymers with matching optical, mechanical, and electrical properties have been formulated and processed. Using a novel trench- and-fill process, integrated high speed electro-optic switches and modulators have been fabricated and tested.

The spectrum shape of conventional fiber Bragg gratings is near-rectangular. By means of a discrete layer peeling method we numerically study fiber Bragg gratings with right-angled triangular spectrum. Fiber Bragg grating structures with single- and multi-channel right-angled triangular spectra are synthesized. These kinds of devices provide potential applications in wavelength interrogation in optical sensor systems.

As known to all,shape memory behaviour has been observed in a variety of metallic alloys. This phenomenon, however, is not only observed in that field but also in other materials recently, such as in polymers,intermetallic compounds and ceramics, especially in zirconia ceramics.Swain [1] observed the shape recovery of a bent magnesia-partiallystabilized zirconia (Mg-PSZ) bar upon heating above a certain temperature. The maximum deflection which was nearly completely recovered on heating is about 300 μm.Chen et al [2] investigated the pseudoelasticity and shape memory effect (SME) in ceria-stabilized tetragonal zirconia polycrystals (Ce- TZP) containing 12 mol% CeO2.Wang et al [3] also observed the SME in Ce-TZP containing 10 mol% CeO2,.Here we would like to introduce some of results conducted recently in our group on SHE in Ce-TZP ceramics.