Room-temperature bonding for plastic high-pressure microfluidic chips

A generic method for the rapid, reproducible, and robust bonding of microfluidic chips fabricated from plastics has been developed and optimized. One of the bonding surfaces is exposed to solvent vapor prior to bringing the mating parts into contact and applying a load. Nanoindentation measurements performed by atomic force microscopy show that a reversible material softening occurs upon exposure to solvent vapor. Subsequent exposure of the bonded chip to UV light then strengthens the bond between mating parts and increases the burst pressure by 50% due to partial cross-linking and chain scission reactions as measured by size exclusion chromatography-multiangle light scattering (SEC-MALS). Performing all steps of this procedure at room temperature eliminates channel distortion observed during thermal bonding and affords channels with highly uniform cross-sectional dimensions. Our technique enables chips resistant to pressures as high as 34.6 MPa.     

Low auto‐fluorescence fabrication methods for plastic nanoslits

Plastic nanofluidic devices are becoming increasingly important for biological and chemical applications. However, they suffer from high auto‐fluorescence when used for on‐chip optical detection. In this study, the auto‐fluorescence problem of plastic nanofluidic devices was remedied by newly developed fabrication methods that minimise their auto‐fluorescence: one by depositing a gold (Au) layer on them, the other by making them ultra‐thin. In the first method, the Au layer [minimum thickness is 40 nm on 150 μm SU‐8, 50 nm on 1 mm polyethylene terephthalate (PET), and 40 on 2 nm polymethyl methacrylate (PMMA)] blocks the auto‐fluorescence of the polymer; in the second method, auto‐fluorescence is minimised by making the chips ultra‐thin, selected operating thickness of SU‐8 is 20 μm, for PET it is 150 μm, and for PMMA it is 0.8 mm.Inspec keywords: nanofluidics, nanofabrication, plastics, optical sensors, nanosensors, biological techniques, gold, biosensorsOther keywords: autofluorescence fabrication methods, plastic nanoslits, plastic nanofluidic devices, biological applications, chemical applications, on‐chip optical detection, gold layer, SU‐8, polyethylene terephthalate, size 20 mum, size 150 mum, size 0.8 mm, Au     

Mutual diffusion process for continuous fabrication of graded-index plastic rod lenses

We propose a new process for fabrication of plastic rod lenses based on the traditional method of fiber extrusion. The process consists of the following steps: multilayer conjugate extrusion, monomer diffusion between adjacent layers, and photopolymerization of an uncured strand fiber. We call this process a mutual diffusion process for continuous plastic rod lens fabrication. Characteristics of this process are as follows: fast production speed (approximately 100 cm/min), precision control of refractive-index distribution, high angular aperture, and long-term reliability. The optical resolution of the rod-lens array is 300 dpi, which is high enough for application to G3 facsimiles with transmission time of less than 1 min and monochromatic scanners.     

Patterned solvent delivery and etching for the fabrication of plastic microfluidic devices

A very simple method for micropatterning flat plastic substrates that can be used to build microfluidic devices is demonstrated. Patterned poly(dimethylsiloxane) elastomer is used as a template to control the flow path of an etching solvent through a channel design to be reproduced on the plastic substrate. The etching solvent was a acetone/ethanol mixture for poly(methyl methacrylate) substrates or a dimethylformamide/acetone mixture for polystyrene. The method is extremely fast in that duplicate plastic substrates can be patterned in just a few minutes each. We identified conditions that lead to smooth channel surfaces and characterized the rate of etching under these conditions. We determined that, for sufficiently short etching times (shallow channel depths), the etch rate is independent of the linear flow rate. This is very important since it means that the etch depth is approximately constant even in complex channel geometries where there will be a wide range of etchant flow rates at different positions in the pattern to be reproduced. We also demonstrate that the method can be used to produce channels with different depths on the same substrate as well as channels that intersect to form a continuous fluid junction. The method provides a nice alternative to existing methods to rapidly fabricate microfluidic devices in rigid plastics without the need for specialized equipment.     

Inegrated autocorrelation method for plastic strain determination

This paper presents an integrated autocorrelation method for the measurement of plastic deformation in metallic materials. The method employs a laser beam to illuminate the test objects. The diffracted images are digitised, recorded and processed on a computer based image processing system. The subsequent speckle pattern correlation analysis yields information on the surface deformation of the test objects. The technique is applied to brass tensile specimens and it is found that the integrated autocorrelation coefficient is linearly proportional to the plastic shear strain. For the range of plastic strain measured the error involved would be less than 10%.     

钨丝微电极阵列的简易制备方法

本文提出了一种简易、低成本的钨丝微电极阵列制作工艺和方法.该方法采用MEMS工艺制作的玻璃模具实现钨丝阵列的精密有序排列,同时,在钨丝电极表面涂覆一层光敏性的聚酰亚胺作为绝缘层,结合"双面光刻"技术和电化学腐蚀技术实现电极位点大小和电极丝几何尺寸的精确控制.最后,通过注模、光刻制作SU-8固定座体完成钨丝微电极阵列的组装固定.整个制作工艺简单快速,且玻璃模具可重复使用,大大降低了制作成本.此外,本文还测试和评价了所制作微电极的表面形貌、电学性能以及生物相容性.     

A novel fabrication method for titania resistive switching device

The titania showing reversible resistive switching are attractive for today's semiconductor technology in nonvolatile random-access memories. A novel fabrication method for titania resistive switching device with vertical structure is proposed. First, the Pt electrode was fabricated the bottom using conventional photolithography and chemical etching technique. Next, the titania thin films with the thickness about 50 nm was deposited on the bottom electrode by electron beam evaporation (EBE). Then, the trench of photoresist for electrode deposit was etched with mild chemical process to preserve the original structure of titania layer. After that, the platinum was deposited in the trench of photoresist using ion sputter. A final lift-off process to define the Pt top electrodes was performed with acetone in an ultrasonic bath to remove the resist. The resistive bistability was observed in this device. The on-threshold voltage is +1.5 V and the off-threshold voltage is -0.6 V. The resistance ratio between the two stable states of the device including Al electrode is approximately 1 x 10(3), the state is nonvolatile and the retention-time test performed over an hour in sweeping mode measurement. The results indicate the forming and rupture of conductive channel relate to the defects and distributing of oxygen vacancy. This method is low-cost, high-yielding, and easy to implement, which is applicable to the fabrication of nonvolatile memories.     

An effective fabrication method for ultra thin aluminum structures

In this paper we discuss the various effects on resistivity of thin metal films, concluding that grain boundary scattering and the material's electron-mean-free-path are the dominant factors. We also present an effective procedure for the fabrication of patterned ultra thin aluminum (sub 100 nm thick) structures on thermally grown SiO₂ substrates, the results of which are compared to other commonly used electrode fabrication methods. A general 4-point probe measurement of an as-deposited 60 nm aluminum film's resistivity was performed. We also found our unique wet-etching method to deliver reproducible results with varying film thickness and yielding a favorable environment for the integration of nanomaterials.     

Wet etching rates of InGaZnO for the fabrication of transparent thin-film transistors on plastic substrates

The wet etch process for amorphous indium gallium zinc oxide (a-IGZO or a-InGaZnO) by using various etchants is reported. The etch rates of a-IGZO, compared to another indium-based oxides including indium gallium oxide (IGO), indium zinc oxide (IZO), and indium tin oxide (ITO), are measured by using acetic acid, citric acid, hydrochloric acid, perchloric acid, and aqua ammonia as etchants, respectively. In our experimental results, the etch rate of the transparent oxide semiconductor (TOS) films by using acid solutions ranked accordingly from high to low are IZO, IGZO, IGO and ITO. Comparatively, the etch rate of the TOS films by using alkaline ammonia solution ranked from high to low are IGZO, IZO, IGO and ITO, in that order.Using the proposed wet etching process with high etch selectivity, bottom-gate-type thin-film transistors (TFTs) based on a-IGZO channels and Y₂O₃ gate-insulators were fabricated by radio-frequency sputtering on plastic substrates. The wet etch processed TFT with 30 µm gate length and 120 µm gate width exhibits a saturation mobility of 46.25 cm² V^− 1 s^− 1, a threshold voltage of 1.3 V, a drain current on-off ratio > 10⁶ , and subthreshold gate voltage swing of 0.29 V decade^− 1. The performance of the TFTs ensures the applicability of the wet etching process for IGZO to electronic devices on organic polymer substrates.     

Novel method for fabrication of NiO sensor for NO2 monitoring

Nickel oxide (NiO) sensor films were prepared on glass substrate by a sol–gel spin coating technique. These films were characterized for their structural and morphological properties by means of X-ray diffraction, field emission scanning microscopy and atomic force microscopy. The NiO films are oriented along (200) plane with the cubic crystal structure. These films were utilized in nitrogen dioxide gas (NO₂) sensor. The dependence of the NO₂ response on operating temperature, NO₂ concentration was investigated. The NiO film showed selectivity for NO₂ over Cl₂ compared to H₂S $ \left( {{\text{S}}_{{{\text{NO}}_{ 2} }} /{\text{S}}_{{{\text{Cl}}_{ 2} }} = 3 7. 5,{\text{ S}}_{{{\text{NO}}_{ 2} }} /{\text{S}}_{{{\text{H}}_{ 2} {\text{S}}}} = 3. 4} \right) $ . The maximum NO₂ response of 23.3 % with 85 % stability at gas concentration of 200 ppm at 200 °C was achieved. The response time of 20 s and recovery time of 498 s was also recorded with same operating parameters.     

A method for the fabrication of low-noise carbon fiber nanoelectrodes

A new and facile method has been developed for the fabrication of low-noise carbon fiber microelectrodes (CFMEs) and carbon fiber nanoelectrodes (CFNEs). The carbon fiber was flame-fuse sealed in the tip of the glass capillary. The CFMEs were made by cutting the protruding carbon fiber to the desired length, and the CFNEs were achieved by etching the protruding carbon on the flame to form a nanometer-scale tip. The tip of CFNEs can be controlled within the range from 100 to 300 nm. Thus, no epoxy wax was involved in the CFMEs and CFNEs. The experimental results of inspecting CFMEs and CFNEs by scanning electron microscopy demonstrated that the surface of the electrodes and the glass/fiber interface are very smooth. Therefore, the noise caused by the glass/fiber of these electrodes is much lower than that of the electrodes fabricated conventionlly. The electrodes were characterized by ferricyanide, catecholamine (dopamine,DA), norepinephrine (NE), and epinephrine (E)) and 5-hydroxytryptamine (5-HT) neurotransmitters using CV, LSV, DPV, and FSCV. The results showed that the CFMEs and CFNEs have very excellent electrochemical behavior and high sensitivity. The CV and DPV detection limits of DA, NE, and E are 7.6 x 10(-8), 7.0 x 10(-8), and 5.0 x 10(-8) mol/L, and the DPV detection limits of DA, NE, and E are 4.0 x 10(-8), 1.0 x 10(-7), and 2.2 x 10(-7) mol/L, respectively. This experiment offers a new and facile method for the fabrication of CFMEs and CFNEs of very high sensitivity and low noise.     

A novel method for massive fabrication of β-SiC nanowires

Silicon carbide nanowires (NWs), that were over 200 μm in length and 20–200 nm in diameter, were prepared by high-pressure reaction from SiBONC powder tablets. Annealing temperatures between 1,500 °C and 1,600 °C and Si/B molar ratios between 70:30 and 60:40 were suitable for the growth of the nanowires. The nanowires were fabricated by in situ chemical vapor growth process on the tablets. The SiC nanowires were identified as single crystal β-SiC. The analysis of X-ray diffraction (XRD) and transmission electron microscopy (TEM) showed the single crystalline nature of nanowires with a growth direction of <111>. Massive growth of single crystalline SiC nanowires is important to meet the requirements of the fabrication of SiC nanowire-based nanodevices.     

A facile method for fabrication of large area graphene nanostructures

In this study, we introduce a novel method to produce large area interconnected graphene nanostructures. A single layer CVD (Chemical Vapor Deposition) grown graphene was nanostructured by employing dewetted Ni thin film as an etching mask for the underlying graphene. As a result, a network of graphene nanostructures with irregular shapes and widths down to 10 nm is obtained. The FET (field effect transistor) devices fabricated employing the nanostructured graphene as channel material exhibit increased on/off current ratio compared to pristine graphene indicating a slight band gap opening due to the quantum confinement effect in such narrow graphene nanostructures. This technique can be useful for the large scale fabrication of graphene based electronic devices such as FETs and sensors.     

The fabrication of protein nano arrays using 3-dimensional plastic nanopillar patterns

A plastic nanopillar array was used as the basis for development of a cheap, spatially patterned immobilization method that was applied to nano biochips. A plastic nanopillar array (diameter: 500 nm, height: 1.2 microm) was fabricated using poly(urethane acrylate) (PUA) by simple and fast UV-curable soft lithography. Antibodies were immobilized on top of the nanopillar structure due to the 'lotus effect'; the aqueous solution containing proteins could only contact the top portion of the nanopillar array due to the hydrophobicity of the surface. This phenomenon was verified by atomic force microscopy and confocal microscopy. Optimal conditions were investigated to effectively generate a clear protein pattern on the nanopillar array. The immunoreaction capability of captured antibodies immobilized on the nano pattern was validated using various concentrations of complimentary antibodies.     

长条形超声塑料焊接焊头的简明设计

焊头是超声塑料焊接设备中一个很重要的部件,其设计的好坏直接关系到焊接质量。将长条形焊头通过合理开槽划分为若干相等的单元．每个单元可作为复合阶梯形变幅杆来处理,用传递矩阵法得出了焊头单元的频率方程,为长条形开槽焊头的设计提供了理论依据。实验表明,利用该方程设计的长条形焊头,其实测频率与设计频率符合很好。本设计方法物理意义明显,计算简单,非常适合工程设计。此外利用该方法可方便的求出开槽数、槽宽度以及槽长度等因素对焊头尺寸的影响,也为焊头的优化设计提供了一定的理论依据。