Search

A microfluidic chip with integrated microelectrodes for real-time dopamine (DA) detection was designed and fabricated. The chip consisted of a polydimethylsiloxane (PDMS) channel plate and a glass electrode plate. One central channel as the culture chamber of neural stem cells and two lateral channels for the transportation of the culture medium were integrated on the PDMS channel plate. Microelectrodes for real-time dopamine detection were integrated on the glass electrode plate. To solve the problem in demoulding the PDMS channel plate from the silicon mold, a novel demoulding method was developed. An Au-Au-Au three-electrode system was constructed, and it performed well in electrochemical detection. The performance of the microfluidic chip was primarily studied by detecting dopamine dissolved in the medium for the culture of neural stem cells. The detection limit of dopamine was 3.92 μM, the linear detection range was from 10 μM to 500 μM, and the detection reproducibility from different chips was less than 4%.

The effects of silica nanoparticles on the properties of a commonly used Sylgard 184 polydimethylsiloxane (PDMS) in microfluidics were systemically studied. Two kinds of silica nanoparticles, A380 fumed silica nanoparticles and MCM-41 mesoporous silica nanoparticles, were individually doped into PDMS, and the properties of PDMS with these two different silica nanoparticles were separately tested and compared. The thermal and mechanical stabilities of PDMS were significantly enhanced, and the swelling characteristics were also improved by doping these two kinds of nanoparticles. However, the transparency of PDMS was decreased due to the light scattering by nanoparticles. By contrast, PDMS/MCM-41 nanocomposites showed a lower coefficient of thermal expansion (CTE) owing to the mesoporous structure of MCM-41 nanoparticles, while PDMS/A380 nanocomposites showed a larger elastic modulus and better transparency due to the smaller size of A380 nanoparticles. In addition, A380 and MCM-41 nanoparticles had the similar effects on the swelling characteristics of PDMS. The swelling ratio of PDMS in toluene was decreased to 0.68 when the concentration of nanoparticles was 10 wt %.

Node localization technology is one of the most important technologies in wireless sensor networks. Due to the advantages of saving and convenience, received signal strength indication (RSSI) technology is widely taken to measure the distance between the sensor nodes, and then trilateral localization algorithm which is one of the classic algorithms can calculate the position result quickly. However, the result always comes with an irregularly wide error. Environment, temperature and electromagnetism are generally considered the interference factors, which have been widely researched. From another angle, this study focuses on the error of the algorithm itself, and discusses the stability of equations. A trilateral localization algorithm for outliers suppression is proposed. Through a large number of simulation, it is demonstrated that the proposed algorithm has a good performance than classic trilateral algorithm based-on the nearest three anchor nodes. A significant meaning of this research is that the deepest source of gross errors has been found when we use classic trilateral algorithm.

Glutamic-pyruvic transaminase (GPT) is one of the most important enzymes in human liver and has a valuable clinical reference for the diagnosis of many liver diseases. Here a method for the determination of GPT activity based on transdeamination is presented. In this method, a three electrode setup was used for the cyclic voltammetric determination of the enzyme. With the electrochemical detection of reduced nicotinamide adenine dinucleotide (NADH) produced from transdeamination, the GPT activity was characterized under optimal circumstances. Firstly, to verify the response of the electrode to NADH, a series of NADH concentrations varying from 39 μM to 2.5 mM were calibrated with cyclic voltammetry (CV). A linear relationship between the NADH concentration and the peak current with R2 0.9999 was obtained. Then the concentration of α-ketoglutarate (α-KG) which can exert great influence on transdeamination was also optimized and the most sensitive response was achieved at the point of 0.75 mM α-KG. Finally, the GPT activity was determined using both the unmodified screen-printed carbon electrode (SPCE) and the electrode modified with CNTs. The results showed that the relationship between the GPT activity and the peak current of the CV curve was linear between 60 U L−1 and 300 U L−1 and the modified electrode exhibited a slightly better linear relationship than the unmodified electrode. This work proposes a new enzymatic reactive system based on transdeamination for the electrochemical detection of GPT activity and combines the electrochemical detection of NADH with the determination of GPT activity.

Organic light-emitting diodes (OLEDs) based on red and green phosphorescent iridium complexes are successfully commercialized in displays and solid-state lighting. However, blue ones still remain a challenge on account of their relatively dissatisfactory Commission International de L'Eclairage (CIE) coordinates and low efficiency. After analyzing the reported blue iridium complexes in the literature, a new deep-blue-emitting iridium complex with improved photoluminescence quantum yield is designed and synthesized. By rational screening host materials showing high triplet energy level in neat film as well as the OLED architecture to balance electron and hole recombination, highly efficient deep-blue-emission OLEDs with a CIE at (0.15, 0.11) and maximum external quantum efficiency (EQE) up to 22.5% are demonstrated. Based on the transition dipole moment vector measurement with a variable-angle spectroscopic ellipsometry method, the ultrahigh EQE is assigned to a preferred horizontal dipole orientation of the iridium complex in doped film, which is beneficial for light extraction from the OLEDs.

The activity of glutamic pyruvic transaminase (GPT) is an important clinical evidence for some acute diseases such as acute hepatopathy and myocardial infarction. Thus, there is a demand for rapid determination of GPT in small formats at point-of-need. Herein, we describe a novel method of electrochemical determination of GPT with microfluidic technique. GPT activity was indirectly determined via the electrochemical (EC) detection of nicotinamide adenine dinucleotide (NADH) produced from the GPT transdeamination reaction. A type of microfluidic chip was developed, in which a passive mixer comprising 100 sub-ribs and a three-electrode strip for EC were integrated. To verify the response to NADH, a series of NADH concentrations varying from 19 µM to 5 mM were calibrated with cyclic voltammetry within the microfluidic chip. And a linear relationship with R 2 0.9982 between the peak current and the concentration of NADH was obtained. Then, the GPT activity was determined using the chips containing and not containing a ribs-type mixer. And a linear relationship which contained two sections between the GPT activity and the peak current was obtained. The chip with a ribs-type mixer exhibited the sensitivity of 0.0341 μA U−1 L in the range of 10–50 U L−1 and 0.0236 μA U−1 L in the range of 50–250 U L−1. And the detection limit of the chip with a ribs-type mixer was 9.25 U L−1. The complete detection process of GPT activity within the microfluidic chip was realized, and the time-consuming problem was remarkably improved too.

A new technique was developed for embossing microstructures on thermoplastic substrates, which can achieve high accuracy replication with little loss of the production efficiency. The technique is no need of the preheating process and cooling device. In the new technique, just the surface layer of the polymer substrate was heated through heat transmission and ultrasonic viscoelastic heating was the major heat source. For our new technology, the temperature of the mould just provided the initial temperature of the mould-substrate interface and a higher boundary temperature for embossing. The replication accuracies of three embossing technologies were contrasted, including ultrasonic embossing at room temperature (HER), thermal assisted ultrasonic embossing (TUE) and local thermal assisted ultrasonic embossing (L-TUE). The results indicated that, the replication accuracy of L-TUE was approximate with TUE. Moreover, the effects of the processing parameters on the replication quality, including average replication depth and uniformity over the entire chip, were investigated. Different with our prediction, the replication accuracy did not monotonously improved with the ultrasonic force and the temperature of the mold. Finally, the temperature test was carried out to study the temperature characteristic of our new technology.

The ultra-precision master gear with high pitch accuracy has important applications in the calibration of high-precision gear measuring instruments or coordinate measuring machines and in military industries. In order to improve pitch deviations of ultra-precision gear, two gear-grinding techniques to improve pitch deviations of ultra-precision gear were proposed. First, based on the indexing plate system, the working principle of indexing plate and error transferring rules were discussed, and the technical approaches of decreasing the geometric eccentricity were proposed. Then according to the error interference principle, the offset-compensated technique and the neighbour-tooth translocation technique were proposed to improve the pitch machining accuracy of ultra-precision master gear. Finally, precision gear-grinding experiments were conducted by adopting the neighbour-tooth translocation technique based on offset-compensated technique. And the single pitch deviation fp of the test specimen is reduced from 1.06 to 0.63μm and the total cumulative pitch deviation Fp is reduced from 3.11 to 1.98μm with measurement uncertainty U95 = 0.33μm, which both reach the highest class (class 1 defining in ISO 1328-1:2013). The results show the efficiency and practicability of the two gear-grinding techniques to machine ultra-precision master gear.

Many electroforming microstructures need their substrates to be bonded with electroforming layers in micromanufacturing. A controlling current density method to improve the adhesion performance of the copper substrate to the nickel electroforming layer was presented. Lower direct current density was employed to activate the substrate. A scratch test was conducted to evaluate the adhesion strength quantitatively by observing the friction load versus the normal load and the scratch track using a digital microscope. The experimental results indicated that electrochemical activation occurred on the cathode surface with an initial current density of between 0.2 and 1.0 A/dm2. The adhesion performance of the activated substrate to the nickel layer was higher than that of a substrate without activation. While the direct current density was 0.4 A/dm2, the adhesion strength was the highest. Electrochemical activation at the beginning of microelectroforming can enhance the adhesion strength of microstructures.

A novel method for fabricating a three-layer SU-8 mould with inverted T-shaped cavities is presented. The first two SU-8 layers were spin coated and exposed separately, and simultaneously developed to fabricate the bottom and the horizontal part of the inverted T-shaped cavity. Then, a positive photoresist was filled into the cavity, and a wet lapping process was performed to remove the excess photoresist and make a temporary substrate. The third SU-8 layer was spin coated on the temporary substrate to make the vertical part of the inverted T-shaped cavity. The sacrificial photoresist layer can prevent the first two SU-8 layers from being secondly exposed, and make a temporary substrate for the third SU-8 layer at the same time. Moreover, the photoresist can be easily removed with the development of the third SU-8 layer. A polydimethylsiloxane (PDMS) microchip with arrays of T-shaped cantilevers for studying the mechanics of cells was fabricated by using the SU-8 mould.

A new method for fabrication of micro-nanofluidic devices through photopolymerization was developed and related experimental research on trace enrichment was undertaken. COMSOL software was utilized to calculate and analyze the gel photopolymerization process on microscale. Moreover, a mathematical model of photopolymerization including photoinitiator decomposition, radical consumption, polymerization, etc., was established and the influence of the exposure time and the light intensity on gel nanosieve width was obtained. With an inverted fluorescence microscope, the micro-nanofluidic chip was prepared by integrating pore density-tunable gel nanosieves into specific areas of the microchannels through focusing, beam splitting and other control means. Based on the Poisson-Nernst-Planck model, the process of nanofluid-based electrokinetic enrichment process was simulated numerically, and the relationship between nanopore density and concentration ratio was investigated. By utilizing the prepared chips, the experiments of nanofluid-based electrokinetic enrichment were performed and the enrichment ratio of fluorescein isothiocyanate (FITC) could reach 600-fold when the mass ratio of the monomer acrylamide to the crosslinker N,N '-methylenebisacrylamide is 9:1.

Microelectroforming is a modern manufacturing process for producing metal microstructures in the field of microelectronic mechanical systems. Electrochemical activation of the substrate surfaces can enhance the adhesion strength between the electroforming layer and the substrate at the first stage of microelectroforming. The mechanism of current density affecting the activation of the substrate surfaces was explored. The cathodic overpotential was carried out with the chronopotentiometric method under different current density conditions. The current density at the first stage of microelectroforming was the largest contributor to the electrochemical activation of the substrate surfaces. As the current density was set in the range of 0.2—1.2 A/dm 2 , effective electrochemical activation occurred on the substrate surfaces. Although the current density was 0.4 A/dm 2 , the effect of substrate activation is optimal and the adhesion strength between the electroforming layer and the substrate reached its maximum.

The subsystems risk assessment of CNC machine tools is an important and yet key problem for reliability management. A novel method based on posterior probability function for assessing subsystem risk was proposed. Firstly, the subsystem reliability of the CNC machine tools was calculated by the John estimator, since the failure data was censored. Secondly, Weibull distribution parameters were estimated using the Maximum Likelihood Estimation (MLE) and Least Square Estimation (LSE), and the best distribution functions were chosen based on the maximum error and Mean Square Error between the estimated reliability and fitting reliability. Thirdly, the posterior probability functions of each subsystem of the CNC machine tools were constructed using the total probability formula, and the comparative analysis of subsystem unreliability was conducted for identifying the key subsystems based on the posterior probability of each subsystem. Finally, a case example analysis proved that the proposed method could assess subsystem risk of the CNC machine tools rapidly and accurately.

Energy efficiency and quality of service (QoS) are both essential issues in the applications of wireless sensor networks (WSNs) all along, which are mainly reflected in the development of routing and MAC protocols. However, there is little design for achieving the dual performances simultaneously. In this paper, we develop a practical passive cluster-based node-disjoint many to one multipath routing protocol to satisfy the requirements of energy efficiency and QoS in practical WSNs. Passive clustering approach is put to use in the first round, while active clustering technique is taken in the other rounds. Implementation of smart delay strategy makes the cluster distribute uniformly, as well as lessen the number of nodes that have taken part in routing. Among cluster heads, a node-disjoint many to one multipath routing discovery algorithm, which is composed of the optimal path searching process and multipath expansion process, is implemented to find multiple paths at the minimum cost. The simulation results show the proposed protocol achieved very good performance both in energy efficiency and QoS.

We present a new method to fabricate one-dimensional (1D) nanochannels on a thermoplastic substrate. This method has two main steps. First, a mold with microscale features is used to replicate microchannels on a thermoplastic substrate. Second, the fabricated microchannel is compressed to a 1D nanochannel at a temperature above the glass transition temperature (Tg) of the themoplastics. The effects of compression temperature, compression pressure, retaining time and loading rate on microchannel compression have been studied. Results have shown that a 1D nanochannel of 1---30 μm wide and 200---300 nm deep can be readily fabricated by using this method.

The accuracy requirement of ultra-precision involute artefacts and master gears, which are used to calibrate the gear measuring machines, is increasing as power density increases; however, the complexities and specificities in the involute processing and measuring have been the bottleneck of manufacturing technique for high-grade involute artefacts and ultra-precision master gears. In order to develop the ultra-precision involute gear profile, related researches were conducted in this study. First, the manufacturing level of high-grade involute artefacts was introduced. Then, the forming principle of the involute was discussed, and the roller–rail type and cam–baffle type of mechanical generating mechanism with little effects of driving accuracy on generating accuracy and less error sources were pointed out. Finally, the double roller–rail type of grinding and measuring devices for high-grade involute artefacts were designed according to the optimal forming principle of the involute, and a precision grinding experiment on an involute cam (a kind of high-grade involute artefacts) was conducted. The measured results show that the total profile deviation is not more than 0.6 µm and the profile form deviation is less than 0.4 µm in 105 mm generating length of the specimen. By using the refined involute cam and gear grinder with cam–baffle type of mechanical generating mechanism, a precision grinding experiment on the specimen of a master gear was conducted. The experimental results verify that the roller–rail type of mechanical generating mechanism has the processing capacity of high-grade involute artefacts with submicron-level profile accuracy and the refined gear grinder with cam–baffle type of mechanical generating mechanism has the processing capacity of ultra-precision master gear with grade-1 profile accuracy.

A novel equivalent circuit model of capacitively coupled contactless conductivity detection (C4D) on microfluidic chips is presented. The impedance of the solution in microchannels facing the two electrodes for C4D was first introduced in the model of C4D on microfluidic chips. The electrodes and the solution facing electrodes were divided into individual segments in the model, and the effect of the length of divided segments on the model was studied. A back-calculating method was put forward to calculate the stray capacitance between the electrodes, and the variation between the calculated value and the simulated value was only 6 %. To evaluate the accuracy of the model, a hybrid poly (methyl methacrylate) (PMMA)/polydimethylsiloxane (PDMS) microchip was fabricated and a simple model was built. Compared with the outputs of the simple model, the data predicted by the novel model show a much closer fit to experimental results, and the variations were within 8 % over a wide concentration range of 1–500 μm for potassium chloride.

Aiming at the uncertainty of the expert judgment in the failure mode and effect analysis of machining centers, a failure mode analysis method for the machining centers based on the possibility theory is proposed. To express the uncertainty of the expert judgment, the possibility distribution of the attribute of the judgment is established and the information fusion of the possibility distribution is implemented using the comprehensive analysis method, obtaining the possibility distribution of the influence factor; The values are assigned to the weights using the subjective-objective combination weighting approach which combines the variation coefficient method and the subjective weighting method. And then the possibility values of the RPN are calculated and ranked. A machining center is taken as the example, and the proposed method is applied to analyze the criticality of its failure modes, and the design for reliability promotion is presented according to the ranking of criticality.

A polydimethylsiloxane (PDMS) electrophoresis microchip with a thickness-controllable insulating layer for capacitatively coupled contactless conductivity detection is presented. A PDMS film is spin-coated on a glass slide with Pt microelectrodes to be the insulating layer, and then permanently bonded with a PDMS channel plate to make the whole microchip. The thickness of PDMS films can be precisely controlled down to submicrometers. With a microchip with a 0.6 μm-thick PDMS insulating layer, a superior limit of detection (LOD) of 0.07 μM for Na+ was obtained. For comparison, another two microchips with the same design but different insulating layer thicknesses (15 μm and 50 μm) were tested, and LODs were 1 μM and 3 μM respectively, which are almost two orders of magnitude higher. Moreover, the microchip detector also exhibited excellent linearity, reproducibilities and separation efficiencies. Keywords: Capacitatively coupled contactless conductivity detection, Electrophoresis, Microchip, Microfluidic, PDMS

“Reservoir unsealed” and “boundary layer separation” are two main issues in the fabrication of a multilayer poly(methyl methacrylate) (PMMA) microfluidic chip. In this paper, embedded sacrificial layer bonding (ESLB) and laser edge welding (LEW) are presented to avoid them. ESLB is performed by inserting a sacrificial-layer into a reservoir to enhance the transfer of bonding pressure among different layers. LEW is performed by using CO2 laser to weld the edge of a bonded multilayer chip. By using these two methods, a three-layer microchip and a five layer micro-mixer are fabricated. Our results demonstrated that ESLB and LEW can be implemented readily in the fabrication of a multilayer thermoplastic microfluidic chip which may facilitate the development of sophisticated microfluidic systems.

This paper presents ultrasonic embossing using silicon molds to replicate microstructures on Polymethyl Methacrylate (PMMA) substrates. The pattern of the silicon mold consists of micro grooves with different sizes. The molds were fabricated by wet etching, and both concave and convex types were fabricated. The effects of the processing parameters on replication quality, including average microstructure depth, uniformity and the location-related replication depth were investigated via orthogonal experiments. The results show that the ultrasonic amplitude is the most important parameter for replication depth. The ultrasonic time benefits the accumulation of the heat, so it also influences replication depth. As for ultrasonic force, it has less influence on replication depth but significant influence on replication uniformity. The width of the grooves of the high density patterning molds ranged from 10 to 30 μm, and the center distance between the two microstructures from 20 to 50 μm in our experiments. The concave molds were intended to reach higher replication depth than that of convex molds with the same micro grooves. The average replication depth reached 98 %, and the uniformity on one chip reached 99 % with an area of 11 × 11 mm. All experiments were finished in 60 s, which is more efficient than the hot embossing technique, thus this paper provides a potential method for medium-sized bulk production and rapid fabrication for polymer microcomponents.

A novel hot embossing method is developed to fabricate polymer nanochannels. The pattern on the silicon nanomould is transferred to polymethylmethacrylate (PMMA) plates, and then polyethylene terephthalate (PET) nanochannels are embossed by using the PMMA mould. The use of the PMMA intermediate mould can extremely increase the device yield of the expensive silicon nanomould. To avoid the use of nanolithography, a method based on UV-lithography techniques for fabricating silicon nanomoulds with sub-micrometer width was put forward. 1 PMMA mould can be used to repeatedly emboss at least 30 PET substrates without damage and obvious deformation. Good pattern fidelity of PET nanochannels was obtained at the optimized embossing temperature of 90 °C. For an 808 nm-wide and 195 nm-deep nanochannel, the variations in width and depth between PET nanochannels and PMMA moulds were 1.8 and 2.5 %, respectively. The reproducibility was also evaluated, and the relative standard deviations in width and depth of 5 PET nanochannels were 5.1 and 7.3 %, respectively.

One method of fabricating micro/nanofluidic chips is to form microchannels and nanochannels in different plates and then assemble them together. In this paper, two practicable methods for the assembly of the micro/nanofluidic chips were built up. One was the rotating-then-pushing method (RP) and the other was the picking-up-then-placing-down method (PP). Only an inverted microscope and a few mechanical parts were needed. With the well-assembled chips, the experiments of enrichment and micro/nano-flow were conducted. Relevant devices, processes, and characteristics were presented in detail. These flexible assembly methods present the advantages such as low-cost, flexibility, and interchangeability.

Nanocrystalline nickel was produced by pulse reverse microelectroforming. The pulse microelectroforming was also performed for the comparative purposes. The surface morphology and microstructure of electroformed nickel layers were investigated by scanning electron microscopy and X-ray diffractometry. The microhardness of nickel layers was measured with a Vickers microhardness tester. The friction and wear experiments for nickel layers were performed on a friction and wear tester. The results indicate that the nickel layers prepared by pulse reverse microelectroforming exhibit higher density and their grain sizes in the nanometer range. The nickel layers with fine grains, high microhardness and better wear resistance are obtained at positive current density of 20 A/dm2 and negative current density of 2 A/dm2. The microhardness and wear resistance of nickel layers are improved as the positive and negative current densities are increased.

In this paper, we demonstrate the effects of electrophoresis (EP) and electroosmotic flow (EOP) on ion enrichment in micro-nanofluidic preconcentrator via numerical simulation. The difference of sample fluxes resulted from EP and EOP at the micro-nano interface is defined to distinguish the contributions of EOF and EP to ion enrichment. The influences of several parameters related to the enrichment ratio are investigated in detail. The results show that the enrichment ratio can be improved via enhancing the difference. To increase the difference, several proposals are presented, including raising imposed electric potential, increasing surface charge density and enhancing fluid viscosity.

Compression pressure has significant influence on the performance of direct methanol fuel cell (DMFC) and the effect of compression is more significant for a DMFC than a proton exchange membrane fuel cell (PEMFC). But there are few data concerning the compression pressure on the performance of DMFCs. Loading history and feeding mode may also affect the optimal compression pressure for the DMFC. This paper investigates the influence of compression pressure on the DMFC. The effects of reload and air feeding mode are also examined. The optimal pressure of the DMFC is 1 MPa when the cell is assembled for the first time in forced convection mode. However, the optimum pressure decreases to 0.05 MPa when the cell is compressed again because of the residual strain of the GDL. The optimal pressure decreases to 0.5 MPa when the cell operates in air-breathing mode. Therefore, the optimum compression pressure for a DMFC strongly depends on the loading history and the feeding mode.

Pb1-xSrx (Zr0.53Ti0.47) O3 (PSZT) thin films with different x values (x = 0, 0.02, 0.04, 0.06) are prepared by sol-gel method and their properties are studied. All PSZT thin films get a single perovskite phase. The dielectric properties are studied. The leakage current density at an applied electric field of 61.2 kV/cm is 293.0 × 10−9A/cm2 when x = 0.04. The remanent polarization and coercive field values of the PSZT (x = 0) thin film are 8.4 μC/cm2 and 67.5kV/cm, respectively.

Because of extremely small dimensions of nanochannels and low rigidity of polymer, most bonding techniques which are suitable for sealing polymer microscale channels (width and depth in tens to hundreds microns) are not competent for bonding of polymer nanochannels. In this study, a new thermal assisted ultrasonic bonding method for sealing poly (methyl methacrylate) (PMMA) nanochannels was presented. Substrates were preheated to 30–40°C lower than glass transition temperature (T g ) of the material by hot plate. Then low amplitude ultrasonic vibration was employed to generate facial heat at the interface of the substrates. Influences of preheating temperature on bonding strength and dimension loss were studied. The nanochannels were successfully bonded with depth loss less than 5.3% (10.6 nm) and bonding strength of 0.21 J/cm2 at the preheating temperature of 70°C. Thermal assisted ultrasonic bonding is proven to be competent for bonding of polymer nanochannels with high bonding strength, low dimension loss and short bonding time.

With the dimensional reduction of micro-structure, the surface effects greatly influence the dimension precision and surface quality of micro-structure during micro-processing of thermoplastic materials. In this paper, the surface characteristics of several thermoplastic materials usually used in industry are investigated. The Axisymmetric Drop Shape Analysis (ADSA) method in nitrogen gas (N2) environment is adopted to measure the surface tensions of polymethylmethacrylate (PMMA), polystyrene (PS), polypropylene (PP), high-density polyethylene (HDPE) melt under different temperatures. The theoretical relationships between surface tension and temperature of polymer melts are obtained. The comparisons are made among different polymer melts according to the relationship of molecular dynamics. The static contact angles between polymer melts (PMMA, PS) and mold materials (silicon, nickel) under different temperatures are also measured in N2 environment using the ADSA method. The results indicate that the contact angle decreases with the increase of temperature and/or the increase surface energy of the mold material. This study provides relevant data to support for micro-injection molding and to optimize processing parameters.

A thermal assisted ultrasonic bonding method for poly(methyl methacrylate) (PMMA) microfluidic devices has been presented. The substrates were preheated to 20–30 °C lower than glass transition temperature ( T g ) of the polymer. Then low amplitude ultrasonic vibration was employed to generate facial heat at the interface of PMMA substrates. PMMA microfluidic chips were successfully bonded with bulk temperature well below T g of the material and with pressure two orders lower than conventional thermal bonding, which was of great benefit to reduce the deformation of microstructures. The bonding process was optimized by Taguchi method. This bonding technique showed numerous superiorities including high bonding strength (0.95 MPa), low dimension loss (0.3–0.8%) and short bonding time. Finally, a micromixer was successfully bonded by this method and its performance was demonstrated.

This work reports laser ionization combined with Time-Of-Flight (TOF) mass spectrometry investigation on intermediate species in the hydrocarbon plasma of atmospheric-pressure fast-flow pulsed dc-discharge. All neutral intermediate species including transient radicals from benzene/Ar discharge have been characterized by a molecular beam sampling combined with TOF mass spectrometry. This shows that with a hydrocarbon gas mixture of 0.3% C6H6 in Ar discharge the intermediate species consist of simple radicals (such as C2, C5H5, C7H7) and polycyclic organic molecules (C10H8, C13H10, C14H10). Theoretical studies on total energies and ionization potentials of the intermediate species have been carried out using the hybrid density functional theory. Effect of the ionization potential on mass spectral intensity has been discussed. Based on the observed data, the possible major neutral reaction channels of the plasma chemistry have been discussed. The developed experimental method has implications in volatile organic compounds removing and impurities diagnosis in Tokamak edge-plasma.

Bonding is a bottleneck for mass-production of polymer microfluidic devices. A novel ultrasonic bonding method for rapid and deformation-free bonding of polymethyl methacrylate (PMMA) microfluidic chips is presented in this paper. Convex structures, usually named energy director in ultrasonic welding, were designed and fabricated around micro-channels and reservoirs on the substrates. Under low amplitude ultrasonic vibration, localized heating was generated only on the interface between energy director and cover plate, with peak temperature lower than T g (glass transition temperature) of PMMA. With the increasing of temperature, solution of PMMA in isopropanol (IPA) increases and bonding was realized between the contacting surfaces of energy director and cover plate while no solution occurs on the surfaces of other part as their lower temperature. PMMA microfluidic chips with micro-channels of 80 μm × 80 μm were successfully bonded with high strength and low dimension loss using this method.

Heating mechanisms of ultrasonic welding for thermoplastics were studied via numerical simulation and experiment. Relationship between dynamic modulus and static relaxation modulus of thermoplastics was theoretically analyzed. Segment time—temperature equivalency equation for different temperature ranges and a method for directly separating viscoelastic heat from strain energy were used in the simulation. Temperature measurement tests with poly(methyl methacrylate) specimens were carried out to verify the simulation results. Results of simulation and experiment reveal that interfacial friction rather than viscoelastic heat initially start the whole welding process. Viscoelastic heating becomes dominant when temperature reaches Tg (glass transition temperature) of the material. And viscoelastic heat provides most required heat during welding.

Direct methanol fuel cell (DMFC), with benefits such as high energy efficiency, quick start capability and instantaneous refueling, is a promising power source to meet the ever-increasing power demand for portable electronic products. In this paper, a novel CO2-driven fuel-feed device was produced and equipped in a passive 8-cell DMFC twin-stack for long-term operation. It was shown that this fuel-feed device was capable of supplying methanol solution continuously in response to the change in discharging current of the stack. Stainless steel sheet was photochemically etched as current collectors based on MEMS techniques. Series interconnections between two neighbor cells were realized in banded configuration which avoided the external connection. TiN-plated mesh was placed between current collector and membrane electrode assembly (MEA), which was used to lessen the internal resistance of the stack. A peak power density of 16.9 mW cm−2 was achieved with 4 M methanol at ambient temperature and passive operation. The stack equipped with the fuel feed device successfully powered a sensor node for 39 h with the consumption of 80 ml of 4 M methanol.

Fracture of integrated metal microelectrodes likely happens during the thermal bonding process of PMMA [poly (methylmethacrylate)] microfluidic chips. In this paper, the fracture behaviors are studied. The fracture is mainly caused by the plastic deformation of the electrode plate (the PMMA plate with microelectrodes) and the thermal stress of microelectrodes, which is due to the high bonding temperature. To decrease the bonding temperature, a plasma assisted thermal bonding method is evaluated and first used to eliminate the fracture of microelectrodes. In this process, the surface of the cover plate (the PMMA plate with microchannels) is modified using oxygen plasma before the electrode plate is thermally bonded to the cover plate. The parameters of the oxygen plasma treatment are optimized, and the contact angle is decreased from 71.7° to 43.6°. The thermal bonding temperature is optimized, which decreases the temperature from 100 °C to 85 °C. Testing of bonding strength shows an average failure pressure of 1.75 MPa, which is comparable to the bonding strength of 1.46 MPa for chips bonded at 100 °C without plasma modification. In order to demonstrate this bonding method, a PMMA microfluidic chip with integrated copper interdigitated microelectrode arrays for AC electroosmotic pump is fabricated.

The forming process of U-form glass micro-nanofluidic chip with long nanochannels is presented in this paper, in which the fabrication of channels and the assembly of plates are included. The micro-nanofluidic chip is composed of two glass plates in which there are microchannels and nanochannels, respectively. This chip can be used for trace sample enrichment, molecule filtration, and sample separation, etc. In fabrication process, the two-step photolithograph on one wafer is often required in early papers, as nano and micro structure designed in one plate have different depths. In this paper, the channels in micro-nanofluidic chip are designed in two glass plates instead of in one wafer. The nanochannels and microchannels are, respectively, formed on plates using wet etching and two-step photolithograph on one wafer is not required. Since the channels are formed, the upper plate and the bottom plate are assembled together by alignment, preconnection and thermal bonding orderly. Firstly these plates are aligned with the cross-marks on an inverted microscope. The aqueous film between plates is controlled to decrease the static friction force for accurate adjustment. Then the adhesion strength of connection is enhanced with semi-dry status for limiting movement from slight inclining and shaking. At last, the bottom plate and the upper one are irreversibly linked together with thermal bonding. The heating period and max temperature of thermal bonding are optimized to eliminate thermal stress gradient and the size shrinking. With the micro-nanofluidic chip, the 1 μM fluorescein isothiocyanate in 10 mM PBS buffer is concentrated successfully. The sample concentrating factor of light intensity varies from 2.2 to 8.4 with applied voltages between 300 and 2,000 V. The switch effect and the instability effect in concentrating process are described and analyzed too.

Microforce sensors made of PT/PZT/PT thin films were designed in the micro-Newton range. The PT/PZT/PT thin films were deposited on the Pt/Ti/SiO2/Si substrate by the sol–gel process. Structure and the crystallinity of the deposited films were characterized. The sensing properties of the microforce sensors were measured in static state and in quasi-static state. The sensitivities of the microforce sensors with two different sizes were 0.004 and 0.040 mV μ N−1 in the quasi-static state.

Calibration of the micro force sensors is necessary for the measurement of microNewton forces, which are critical to analytical applications of micro force sensor in the analysis of micromanipulators, microrobots and microgrippers. This paper proposes a novel calibration system to calibrate PZT thin film micro force sensor using the bimorph probe as the loading part. Sensitivities of PZT thin film micro force sensors were calibrated by the calibration system composed of the drive system and the testing system. The drive system combines 3-dimensional positioning stage, a bimorph probe and a frequency synthesizer, and the testing system combines an electronic balance for static state or a charge amplifier and a lock-in amplifier for the quasi static state.

A large-scale laser plane calibration system is developed. This plane is constructed by a 35 m long horizontal granite guide rail and a 1.5 m long vertical metal guide rail. Two dual-frequency interferometers are used to measure the coordinates of a target moving on the plane. One of them can measure the horizontal displacement while eliminating the Abbe errors caused by the straightness of the granite guide rail. Another measures the sum of horizontal displacement and vertical displacement. This laser plane can be used as a lab standard to calibrate portable coordinate measuring machines by measuring the target on the plane. Calibration tests for a laser tracker are given.

Reliability modeling and assessment for a single numerical control (NC) machine tool with zero-failure is a new problem that cannot be solved using classic statistical methods. Thus a Bayesian method is proposed aiming at this problem. In combination with the two-parameter Weibull distribution, the Bayes model of zero-failure problem for a single NC machine tool is built. The method of building the Weibull parameters’ prior distributions is presented. The theoretical formula for the parameter vector’s posterior distribution is derived. In software WinBUGS, the Markov chain Monte Carlo (MCMC) simulation is developed to simulate each parameter’s posterior distribution, solving calculation difficulties in high-dimensional integration and parameter estimation. The proposed method is applied to real data, obtaining the parameter estimators and meant time between failures (MTBF). The result is in consistent with the engineering reality. Given the fact that the actual MTBF cannot be achieved by any means, the proposed method achieves the fusion of the expert experience, multi-source prior information and data. The proposed method is advocated to be a standard solution to the zero-failure reliability assessment for NC machine tools.

PZT thin films of various thickness were deposited on Pt(111)/Ti/SiO2/Si(100) substrates by the sol?gel method. A new method to control the crystallographic orientation of the PZT thin films by modifying the coating layers in one annealing cycle is presented in this paper. PZT films with (111) and (100) preferred orientation were obtained using the multi-coating-layer-annealed and the one-coating-layer-annealed sol?gel methods, respectively. The optimized baking and annealing temperatures at 200 and 600??C were obtained by analyzing the phase transformation of the PZT precursor solution. The effect of film thickness on the microstructures, crystalline phases, and electrical properties of the PZT films was investigated. Compared to the multi-coating-layer-annealed method, the one-coating-layer-annealed method decreases the residual stress of the PZT films. The remanent polarization increases with the thickness of the PZT films. The remanent polarization (Pr) and coercive fields (Ec) of the one-coating-layer-annealed PZT films with 1.6??m thickness are 25.7??C?cm?2 and 59.2?kV?cm?1, respectively. New microcantilevers with two PZT piezoelectric elements and three electric electrodes were designed. These structures can be applied to microsensors, microactuators, or versatile devices having both sensing and actuating functions. The cantilevers were successfully fabricated with wet and dry combined bulk micromachining technique.

Fabrication of microchannels on polymethylmethacrylate (PMMA) substrates using novel microfabrication methods is demonstrated. The image of microchannels is transferred from a silicon master possessing the inverse image of the microchannel to a PMMA plate by using hot embossing methods. The silicon master is electrostatically bonded to a Pyrex7740 glass wafer, which improves the device yield from ∼20 devices to hundreds of devices per master. Effects of embossing temperature, pressure and time on the accuracy of replication are systematically studied. According to the suggested experimental model, the time for the whole embossing procedure is shortened from about 20 to 6 min, and the accuracy of replication is 99.3%. The reproducibility of the hot embossing method is evaluated using 10 channels on different microfluidic devices, with variations of 1.4% in depth and 1.8% in width.

In order to fabricate qualified ZnO piezoelectric thin films by sol–gel method, the relationships between the heat treatment temperatures (preheating temperature and annealing temperature) and the quality characteristics of ZnO piezoelectric thin films (c-axis orientation, residual stress, grain size, roughness and resistivity) were investigated. The chemical composition of the precursor sol and the intermediate produced in the films heating process were analyzed by TGA–SDTA and FT-IR. The c-axis orientation and the residual stress of the ZnO thin film were identified by XRD. The morphologies, roughness and grain size were observed and estimated by AFM. The I–V characteristics were measured by using semiconductor characterization system. Experimental results show that the c-axis orientation is determined by both preheating and annealing temperatures, and that the residual stress, grain size, roughness and resistance of the ZnO thin films are mainly influenced by the annealing temperature. A qualified ZnO piezoelectric thin film has been prepared by using sol–gel with preheating temperature 400 °C for 10 min and annealing temperature 700 °C for 30 min.

This paper presents a NURBS (non-uniform rational B-splines) curves based stereo matching algorithm for which curves replace the edges extracted with a wavelet-based method. Curves in the left images are projected onto the right view and the stereo correspondence problem becomes simply the estimation of the similarity between these projections and the original curves in the right image. The projective invariance characteristic of NURBS curves is effective in reducing false matches due to distortion of the perspective projection and image noise. Experimental results demonstrate that the proposed method is robust and effective in removing abnormal reconstruction data. The obtained 3D reconstruction shape is closer to the real one.

The paper presents the modeling of two types of piezoelectric microcantilevers, the two-layer and two-segment piezoelectric cantilevers, in which the two piezoelectric parts perform sensor and actuator functions, respectively. An analytic model is proposed to evaluate the sensing and actuating effects of multiporph microcantilevers formed of several layers or segments of piezoelectric materials. The analytical model is used to analyze the tip deflection of the cantilever and the piezoelectric charge generated on the sensor element as a function of the microcantilever geometry. The cantilevers of sensing and actuation are compared for the different working situations of the two-layer and two-segment cantilevers. The theoretical results can be used to optimize the design of the piezoelectric cantilever structures.

A modified sol-gel multiple coating and annealing process was developed to prepare lead zirconate titanate PbZr 0.5 Ti 0.5 O 3 (PZT) thin films with various thickness on Pt(111)/Ti/SiO 2 /Si(100) substrates. The PZT films with thickness 280, 560 and 810 nm underwent one, two and three annealing cycles, respectively, which consisted of 5 coating layers, 10 coating layers and 15 coating layers. Surface morphology and phase structure of the thin films were studied by SEM and XRD, respectively. The relationship between the thickness, namely different annealing cycles, and degree of texture was investigated. The dielectric constant increases with increasing film thickness. The dielectric constant and dielectric loss of PZT films as functions of applied field and frequency had also been examined and discussed.