Proceedings Volume 7269

Micro- and Nanotechnology: Materials, Processes, Packaging, and Systems IV

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Proceedings Volume 7269

Micro- and Nanotechnology: Materials, Processes, Packaging, and Systems IV

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Volume Details

Date Published: 29 December 2008
Contents: 10 Sessions, 32 Papers, 0 Presentations
Conference: SPIE Smart Materials, Nano- and Micro-Smart Systems 2008
Volume Number: 7269

Table of Contents

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Table of Contents

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  • Front Matter: Volume 7269
  • Fabrication for Bio-applications
  • Bio-Nano
  • Photonics
  • Carbon Nanotechnology
  • Fabrication
  • Simulation
  • System and Design I
  • System and Design II
  • Poster Session
Front Matter: Volume 7269
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Front Matter: Volume 7269
This PDF file contains the front matter associated with SPIE Proceedings Volume 7269, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.
Fabrication for Bio-applications
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Electrospray from hot embossed polymer microfluidic chips formed using laser machined and electroformed tools
Sana Malahat, Pio G. Iovenitti, Igor Sbarski
The aim of this project was to develop high performance polymer microfluidic chips with reduced complexity for Electrospray Ionization Mass Spectrometry (ESI-MS) analysis. This paper presents the fabrication and testing of developed hot embossed open channel polymer microfluidic chips for ESI-MS. Hot embossing was done using a laser machined steel tool and an electroformed nickel tool on polystyrene (PS) and polycarbonate (PC) substrates. Stable electrosprays were generated at microchannel exits of replicated microchips without cover using a high voltage difference between a positive stainless steel electrode in the reservoir and a negative aluminum plate. Electrospray parameters such as; nozzle tip distance from counter electrode, ESI onset potential and duration were investigated. For open channel systems, the results show that the electric field for stable ES directly relates to the distance between the channel tip and counter electrode, onset potential applied and to the flow velocity of the test solution in the microchannel. Fluid is delivered as a result of electroosmosis due to an applied electric field and capillary action, thereby eliminating the need for external pressure devices. From experimental results, for an open-channel of 100μm width, 100μm depth, length 12.5mm attached to an open reservoir of diameter 2 mm, the optimum distance between the channel exit tip and counter electrode is 1.2 mm for initiation of electrospray at voltage of ~2000 volts. The laser machined steel tool was found to be more durable than the nickel tool for PS/PC microstructure fabrication.
Paramagnetic microchip for high-gradient separation of blood cell
Ciprian Iliescu, Guolin Xu, Elena Barbarini, et al.
This paper presents a magnetophoretic separation method on a chip of white blood cells from blood under continuous flow. The separation of red blood cells from the whole blood is performed using a high gradient magnetic separation method under continuous flow to trap the particles inside the device. The device is fabricated by microfabrication technology and enables to capture the red blood cells without the use of labelling tecniques such as magnetic beads. The method consists of flowing diluted whole blood through a microfluidic channel where a ferromagnetic layer, subjected to a permanent magnetic field, is located. The majority of red blood cells are trapped at the bottom of the device while the rest of the blood is collected at the outlet. Experimental results show that an average of 95% of red blood cells are trapped in the device.
Bio-Nano
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Modeling pattern dependencies in the micron-scale embossing of polymeric layers
Hayden Taylor, Ciprian Iliescu, Ming Ni, et al.
We describe a highly computationally efficient method for calculating the topography of a thermoplastic polymeric layer embossed with an arbitrarily patterned stamp. The approach represents the layer at the time of embossing as a linear-elastic material, an approximation that is argued to be acceptable for the embossing of thermoplastics in their rubbery regime. We extend the modeling approach to represent the embossing of layers with thicknesses comparable to the characteristic dimensions of the pattern on the stamp. We present preliminary experimental data for the embossing of such layers, and show promising agreement between simulated and measured topographies. Where the thickness of the embossed layer is larger than the characteristic dimensions of the pattern being embossed, the stamp-layer contact pressure exhibits peaks at the edges of regions of contact, and material fills stamp cavities with a single central peak. In contrast, when the layer thickness is smaller than the characteristic dimensions of the features being embossed, contact pressures are minimal at the edges of contact regions, and material penetrates cavities with separate peaks at their edges. These two apparently distinct modes of behavior, and mixtures of them, are well described by the simple and general model presented here.
Solid-phase purification of gene synthesis products using magnetic beads
Herein we report three novel methods which utilize chemical conjugated magnetic beads to purify synthetic gene from its synthesis solution and prepare the synthesized gene in suitable buffer for downstream applications. Silica-coated magnetic beads are applied for non-specific DNA purification to remove short oligonucleotides and monomers. Streptavidin conjugated magnetic beads and (dT)25 Oligo immobilized magnetic beads are introduced for specific DNA extraction. The performances of these methods are investigated and compared using gel electrophoresis. The optimal conditions for enhancing the extraction efficiency are discussed. In addition, the approach to integrate these solid-phase purification methods into microfluidic devices is presented.
Rapid prototyping of multi-level polydimethylsiloxane-based microfluidic devices
Wai Chye Cheong, Yoke Kong Kuan, Mo-Huang Li, et al.
There has been considerable progress in the development of micro-fabricated systems for the field of chemical and biological sciences. Much development has been driven by the need of miniaturized systems that allow cost-effective and rapid processing of samples at the point of need. In this work, we investigate the application practicality of Objet Eden500VTMPolyjet as a rapid and economical tool for multi-level microfluidic device rapid prototyping. The Polyjet is a commercial system that utilizes ink-jet technology to print 3-dimensional structures with photopolymer materials. The reproducing capability of the Polyjet system in term of lateral and vertical resolutions, aspect ratio and smoothness of fabricated structures are investigated. In addition, the capability of the Polyjet is demonstrated by fabricating three different devices including: 1) multi-level microfluidic chip for two-step gene synthesis, 2) a fluidic component for micro/macro fluidic interfacing, and 3) PDMS-based microlens.
Low-stress PECVD amorphous silicon carbide (α-SiC) layers for biomedical application
A detailed characterization of PECVD to produce low stress amorphous silicon carbide (α-SiC) layers at high deposition rate has been done and the biomedical applications of α-SiC layers are reported in this paper. By investigating different working principles in high-frequency mode (13.56MHz) and in low frequency mode (380KHz), it is found that deposition in high-frequency mode can achieve low stress layers at high deposition rates due to the structural rearrangement from high HF power, rather than the ion bombardment effect from high LF power which results in high compressive stress for α-SiC layers. Furthermore, the effects of deposition temperature, pressure and reactant gas ratios are also investigated and then an optimal process is achieved to produce low stress α-SiC layers with high deposition rates. To characterize the PECVD α-SiC layers from optimized process, a series of wet etching experiments in KOH and HF solutions have been completed. The very low etching rates of PECVD α-SiC layers in these two solutions show the good chemical inertness and suitability for masking layers in micromachining. Moreover, cell culture tests by seeding fibroblast NIH3T3 cells on the monocrystalline SiC, low-stress PECVD α-SiC released membranes and non-released PECVD α-SiC films on silicon substrates have been done to check the feasibility of PECVD α-SiC layers as substrate materials for biomedical applications. The results indicate that PECVD α-SiC layers are good for cell culturing, especially after treated in NH4F.
Electrical impedance properties of bulk carbon nanotube composites for chemical sensors and biosensors
Dae-Sup So, Hoon Huh, Gyeong Rak Choi, et al.
Electrical impedance properties of bulk carbon nanotube (CNT) composite electrodes have been studied to develop chemical and biosensors. The CNTs embedded in composite electrodes were fabricated by means of traditional film casting and electrospun nanoweb. The morphology of the bulk CNT electrode was investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Under the various amounts of buffer solution, electrical impedance of the composite electrodes was measured by means of LCR meter. It is generally known that electrical impedance measurement provides rapid and simple sensing mechanism. In this study, we found out that CNT bulk composite electrodes showed good sensing properties for chemical and bio sensors.
Photonics
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Sealed air-core planar waveguide arrays in SU8 epoxy
Nonlinear optics in fluid infiltrated air structured 'holey' fibres has attracted much research interest due to the flexibility of infiltration materials and geometries that are possible. Equivalently to these 2D examples, planar structures with 1D arrays of air holes can offer a complimentary platform for nonlinear optics investigations. Importantly, if these structures can be photolithographically defined with longitudinal variations, then a rich array of periodic nonlinear phenomena can be studied. We present a novel planar integrated optic platform for fluid infiltration experiments. The platform consists of layers of SU8 epoxy fabricated with 3×3 μm photolithographically defined microfluidic channels. The channel layer can be doped with rhodamine in order to increase its refractive index to enable vertical confinement and also provides a fluorescent trace to clearly indicate the path of the light. The air channels can be filled with fluids, such as high refractive index oil, to act as optical waveguides in the visible range. Our fabrication consists of spin coating and curing the SU8 lower cladding. We then spin-coat and cure the doped SU8 channel layer and pattern using conventional photolithography. In order to seal the channels with the upper cladding, an SU8 dry film is applied using lamination techniques. The fabrication process is highly flexible and can be easily extended to more complex waveguides like splits, mach zehnder structures. Multiple layers of fluid-infiltrated channels are also possible.
Lithographically defined intersecting optical waveguides and fluidic channels
Many optofluidic devices rely on interfacing optical waveguides with microfluidic channels. Often it can be difficult to realize micron scale waveguides and fluidic channels that are 100 times larger on the same platform. Further, it is often desirable for an optical waveguide intersection to occur at the vertical centre of a fluidic channel rather than at its top or at its bottom where the fluid is effectively stationary. We present a platform for optofluidics which can achieve straightforward integration of large scale fluidic channels and micron scale waveguides in the epoxy material SU8. A soft imprinting technique is used to define the optical waveguides as a thin inverted rib core layer between two thick cladding layers. The core is doped with Rhodamine dye to increase the refractive index and render it optically active for potential use as a lasing material. The fluidic channels are then formed by a single exposure through the core and both claddings.
Fabrication of solid immersion lens with gold nanoparticles by surface tension mold technique
T. Kishi, S. Furusawa, T. Yano, et al.
A super-hemispherical (i.e. a truncated spherical) glass lens with gold (Au) nanoparticles was obtained using a surface tension mold (StM) technique. Recently, surface plasmon of noble metal nanoparticle has attracted a considerable amount of interest because it is extremely sensitive to the properties of the materials attached to its surface. On the other hand, in the field of high-resolution microscopy, solid immersion lenses (SILs) with super-hemispherical shape have received much attention because it is a convenient and powerful means of improving both the spatial resolution and the light collection efficiency. A combination of the SIL and the Au nanoparticles could be very suitable for use in surface plasmon microscopy. In this study, Na2O-CaO-SiO2 glass was heated on Au-coated glassy-carbon substrate up to 800 °C. The obtained glasses were found to have super-hemispherical shape, and the Au nanoparticles were deposited on its bottom planar surface. The effects of the deposition condition of Au on the distribution of Au nanoparticles and the shape of glass were investigated, and the surface plasmon resonance absorption spectra from the obtained samples were measured.
Carbon Nanotechnology
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An effective multiscale approach for deformation analyses of carbon nanotube-based nanoswitches
Y. T. Gu, A. Tan, Prasad K. D. V. Yarlagadda
This paper aims to develop an effective multiscale simulation technique for the deformation analysis of nanotube-based nanoswitches. In the multiscale simulation, the key material parameters, (e.g., Young's modulus and moment of inertia) are extracted from the MD simulation which can explore the atomic properties. Then, the switches are simplified to continuum structure which is discretized and simulated by the advanced RBF meshfree formulation. The system of equations is nonlinear because the nonlinear loading is calculated from coupled the electrostatic, the elastostatic, and the van der Waals energy domains. Besides the normal deformation analysis, the pull-in voltage characteristics of different nanoswitches based on the double-walled nanotubes are analyzed. Comparing with the results in the literature and from experiments, it has proven that the developed multiscale approach is accurate and efficient.
Dielectric performance of diamond-like carbon nanofilms deposited by electron-beam-induced deposition
Eugeniu Balaur, Andrew G. Peele
The effect of electron beam dose and low accelerating voltage on diamond-like-carbon (DLC) deposition rate and the resulting current-voltage characteristics in thin metal/DLC/semiconductor junctions was studied. We show that thicker DLC films can be obtained using lower accelerating voltages (2 kV) than when using higher accelerating voltage (20 kV). However, under the conditions used the insulating performance of the thicker films is worse than the thinner films. We attribute this effect to the variation of tunnelling barrier height in DLC deposited using different accelerating voltages. DLC films with a tunnelling barrier height of up to 3.12 eV were obtained using a 20 kV electron-beam, while only 0.73 eV was achieved for 2 kV DLC films.
Fabrication
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Development of thick film PECVD amorphous silicon with low stress for MEMS applications
Bangtao Chen, Francis E. H. Tay, Ciprian Iliescu
This paper presents a solution for the deposition of thick amorphous silicon (α-Si:H) in plasma-enhanced chemical vapor deposition (PECVD) reactors for MEMS applications. Thick α-Si film up to 2 μm is widely used as a sacrificial layer in the MEMS release process, however, the film quality and smoothness are limited by the cracking or peeling of thick film due to their intrinsic stress. This achievement of as thick as 12 μm film was possible by tuning the deposition parameters to a 'zero' value of the residual stress in the α-Si:H layer. The influence of the PECVD process parameters, such as power, frequency mode, temperature, pressure and SiH4/Ar flow rates on tuning the residual stress and a good deposition rate was analyzed. As a result, an almost "zero-stress" α-Si:H film and a deposition rate of 85nm/min was achieved for a temperature of 200ºC, a pressure of 800 mTorr, a high-frequency power of 120W, with SiH4 flow rate of 120 sccm and Ar flow rate of 500 sccm. The deposition of low-stress and thick (more than 12 μm in our case) α-Si:H layers was possible without generation of peeling or hillock defects. Finally, the paper presents some MEMS applications of such a deposited α-Si:H layer: a very good masking layer for dry and deep wet etching of glass; and a sacrificial layer for dry or wet release of bridge/cavity structure.
Ni-PTFE electroformed micro parts by SU8-based UV-LIGA
Yuhua Guo, Yingnan Wang, Tom C. Kong, et al.
The SU8-based UV-LIGA process, which combines lithography with electroforming, is a low cost fabrication method for producing MEMS and precision engineering parts. With lower surface energy and friction coefficient, these micro parts are required for applications such as micro gears and movable microstructures. This paper introduces a technique to fabricate Ni-PTFE micro parts using special treated galvanic bath. The experiment results show that the composite electroforming process is robust and the fabricated Ni-PTFE parts have good tribological properties.
Development of polyimide-based flexible tactile sensing module integrated with strain gauges & flexible flat cable
Kunnyun Kim, Kang Ryeol Lee, Won Hyo Kim, et al.
A flexible tactile sensing module with NiCr strain gauges as sensing elements was fabricated by polymer MEMS technology using polyimide materials where the one was the photo-definable polyimide precursor and the other was nonphoto- definable. The unit sensor cell size of 32×32 tactile sensor array was 1mm × 1mm cell and its overall size was 5.5cm × 6.5cm. Especially, both the tactile sensor arrays and the pluggable terminals as flexible flat cable were fabricated on the same polymer substrate easily to be connected the sensor array with a PCB board. The fabricated tactile sensing module was measured continuously in the normal force range of 0~1N with tactile sensor evaluation system. The value of resistance was relatively linear with normal force in the overall range of 0~1N. However, the variation of resistance was decreased by more than 0.6N. The variation rate of resistance was 2.0%/N in the range of 0~0.6N and 1.5%/N in the range of 0.6~1N. Image display was identified corresponding by distribution of applied force. The flexibility of the sensing module was adequate to be placed on any curved surface as a cylinder.
Simulation
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A scheme to calculate higher-order homogenization as applied to micro-acoustic boundary value problems
Current technological challenges in materials science and high-tech device industry require the solution of boundary value problems (BVPs) involving regions of various scales, e.g. multiple thin layers, fibre-reinforced composites, and nano/micro pores. In most cases straightforward application of standard variational techniques to BVPs of practical relevance necessarily leads to unsatisfactorily ill-conditioned analytical and/or numerical results. To remedy the computational challenges associated with sub-sectional heterogeneities various sophisticated homogenization techniques need to be employed. Homogenization refers to the systematic process of smoothing out the sub-structural heterogeneities, leading to the determination of effective constitutive coefficients. Ordinarily, homogenization involves a sophisticated averaging and asymptotic order analysis to obtain solutions. In the majority of the cases only zero-order terms are constructed due to the complexity of the processes involved. In this paper we propose a constructive scheme for obtaining homogenized solutions involving higher order terms, and thus, guaranteeing higher accuracy and greater robustness of the numerical results. We present
Construction of Wannier functions in phononic structures
The modelling and simulation of periodic structures with defects define boundary value problems (BVPs) which are conceptually and numerically difficult to solve. Innovative and problem-tailored analysis methods need to be devised to solve defect problems efficiently and accurately. One possible attractive method is based on the ideas related to the construction of Wannier functions. Wannier functions constitute a complete sequence of localised orthogonal functions which are derived from associated periodic versions of defect problems. In this paper we review general properties of Wannier functions from a linear algebra point of view, introduce an easy-to-use symbolic notation for the diagonalisation of the governing equations and construct the Wannier functions for a variety of phononic devices. Using certain distinguished properties inherent in the wavenumber-dependence of the eigenvalues we prove the orthogonality and completeness of the Wannier functions in a conceptually novel way.
A novel approach for symbolically calculating polynomial integrals arising in 2D and 3D FEM applications
The rapid growth of the telecommunication and microelectronic industry has been pushing the performance limit of the passive and active electronic components and devices alike. Thereby, improved performance of the devices has become a necessity for operating frequencies moving into the MW region. Examples are Surface Acoustic Wave (SAW) and Bulk AcousticWave (BAW) Devices which are miniaturized microelectronic devices with a wide range of applications in signal processing, forming and sensing. Computation of electroacoustic field distribution in these structures needs to be accurate, efficient and rigorous. However, the amount of data required for preand post-processing is immensely large, and the processing and handling of data are extremely time consuming. In this paper we propose a conceptually novel method for significantly reducing the computational time and thus enhancing efficiency by pre-calculating relevant data, storing, and subsequently retrieving them whenever they are required for device analysis and simulation. We propose a method for symbolically and conveniently calculating two- or three dimensional integrals over the surface of an arbitrary triangle or within the volume of an arbitrary tetrahedral. The results we have obtained are universal in that their application is not limited to microacoustic devices.
System and Design I
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Wet anisotropic etching by TMAH with NCW-1002 surfactant on crystalline silicon surface
Paper reports the use of a new surfactant NCW-1002 as an addictive in TMAH wet anisotropic etching to improve the etching characteristic on three silicon principle planes (i.e. (100), (110), (111) planes). Concentrations of TMAH from 2.5% to 10% with addition of various concentration of NCW-1002 are studied to find an optimal combination for a improved smoothness and etch selectivity between (100) and (110) planes, which is necessary for the formation of 45°mirror plane (110) in (100) silicon surface. Etch rate and roughness of silicon planes were measured by Dektak II and AFM respectively. Besides, this paper will explain the formation of 45°slope. By improving the selectivity or extending the etching depth, we are able to enlarge the 45°portion on the mirror surface.
Investigation of the performance of micro-thermoelectric coolers
Z. W. Zhong, W. Fan, C. W. Low
In this study, the performance of two micro-thermoelectric coolers fabricated was investigated by theoretical calculation and experimental testing of the samples. The natural convection rate and conduction rate were also considered. The corrective implementation improved the theoretical calculation results.
System and Design II
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MEMS product engineering using fabrication process development tools
The development of MEMS devices differs substantially from product engineering methods used in more traditional industries. The approach is characterized by a close customer involvement and product specific fabrication processes. A large number interdependencies between device design on the one hand and manufacturing process development on the other hand make product engineering in the MEMS area a rather tedious and complicated task. In this paper we discuss a comprehensive customer-oriented MEMS product engineering methodology. Both MEMS design and fabrication process development are analyzed with regard to procedures and interfaces used in order to develop an appropriate CAD support either in terms of existing tools or by specifying individual tools to be implemented. The manufacturing process development is part of this holistic approach and is supported by a CAD environment for the management and the design of thin-film MEMS fabrication processes. This environment has been developed by the authors and became recently commercially available.
Rapid prototyping of microfluidic devices using imprinting: application to microvalves and micropumps
Adrian J. Keating, Michael Gager, Donald Clarke
A method to create microfluidic devices by utilizing hot imprinting stamps formed using printed circuit boards is demonstrated. Very large microfluidic devices (15×15 cm2) can be created with lateral features down to 100 microns and depths of nominally 17-70 μm. Room temperature solvent bonding was found to be a simple method of sealing the channels. The work also decribes the fabriation and operation of thermally actuated microvalves with sub-second switching and micropumps based on the imprinting techniques described.
Joint time-frequency analysis of micro-acoustic devices
In this paper, a novel analysis technique for the performance evaluation of micro-acoustic devices has been proposed. Whereas traditional techniques typically focus solely on the frequency domain characteristics, we employ a Joint Time-Frequency Analysis (JTFA), which has been shown to provide a more complete characterisation of overall device performance and underlying physical phenomena. Although an emphasis is placed on a Flexural Plate Wave (FPW) device, the analysis technique presented is applicable to a wider range of micro-acoustic devices including Surface Acoustic Wave (SAW) structures and Thin-Film Bulk Acoustic Wave Resonators (TFBARs). SAWdevices, and indeed general filters, are typically described by a frequency domain characteristic, whereby the entire time domain information is discarded. This type of analysis assumes that the device has reached quasistationary conditions. By employing JTFA, the device performance can simultaneously be studied as a function of both time and frequency. This type of analysis is typically useful where spurious acoustic modes are generated which may influence the overall filter characteristic. We have investigated the functional properties of various JTFA kernels, including those appearing in the Wigner-Ville, Choi-Williams and Page distributions. A known deficiency associated with JTFA is the appearance of a number of spurious cross-terms in the computations. Whereas the cross-terms are relatively simple to detect for "monochromatic" (single-component) signals, it is not a trivial task to minimise such artifacts for "polychromatic" (multi-component) signals, which are typical in micro-acoustic devices. We propose novel methods for reducing the cross-terms interference appearing in JTFA, thereby improving the performance of the analysis technique. To investigate the application of the proposed technique, the simulated time domain response of a FPW device was investigated. The Finite Element Method (FEM) package ANSYS 8.0 was utilised to obtain the impulse response of the FPW structure under a dynamic transient analysis. A comparison is also made with the spectral domain Green's function to verify the FEM solution, where excellent agreement is obtained. Based on the FEM solutions, the insertion loss characteristics is calculated which represents a commonly applied frequency domain method of analysing micro-acoustic devices. A comparison has been made between the insertion loss characteristics and the proposed approach, where it is clearly demonstrated that the problem-adapted technique provides significantly more detailed information.
Poster Session
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Transparency conversion mechanism and laser induced fast response of bimetallic Bi/In thin film
Sihai Cao, Chuanfei Guo, Yongsheng Wang, et al.
Transparency conversion mechanism and laser induced fast response velocity of bimetallic Bi/In thin film is studied. Heat-treatment and laser exposure with different pulse width induced transparency is investigated by using ultraviolet-visible (UV-VIS) spectrometer, X-ray diffraction (XRD), Auger Electron Scan (AES), microscope and field emission scanning electron microscopy (FESEM). Research results show that oxidation is regarded as the reason for heat treated and long-pulsed laser exposure induced transparency conversion. Laser ablation is demonstrated to be the main reason for short-pulsed (~7ns) laser induced transparency conversion. For Bi/In thin film covered with a protection layer of (ZnS)0.85(SiO2)0.15 thin film, it exhibit fast response as fast as less than 100ns. The conclusions contribute to understanding and development of materials for thermal resist, photomask, optical storage medium and transparent conductive oxide with better performance.
Carbon nanotubes on polymer-based pressure micro-sensor for manometric catheters
In this paper we investigate the fabrication process of a novel polymer based pressure micro-sensor for use in manometric measurements in medical diagnostics. Review and analysis of polymer materials properties and polymer based sensors has been carried out and has been reported by us elsewhere [1]. The interest in developing a novel polymer based flexible pressure micro-sensor was motivated by the numerous problems inherent in the currently available manometric catheters used in the hospitals. The most critical issue regarding existing catheters was the running and maintenance costs [2]. Thus expensive operation costs lead to reuse of the catheters, which increase the risk for disease transmission. The novel flexible polymer based pressure micro-sensor was build using SU-8, which is a special kind of negative photoresist. Single-walled carbon nanotubes (SWCNTs) and aluminum are used as the sensing material and contacting electrodes respectively. The pressure sensor diaphragm was first patterned on top of an oxidized silicon wafer using SU-8, followed by aluminum deposition to define the electrodes. The carbon nanotube is then deposited using dielectrophoresis (DEP) process. Once the carbon nanotubes are aligned in between these electrodes, the remaining of the sensor structure is formed using SU-8. Patterning of SU-8 and release from the substrate make the device ready for further testing of sensing ability. This research not only investigates the use of polymeric materials to build pressure sensors, but also explores the feasibility of full utilization of polymeric materials to replace conventional silicon materials in micro-sensors fabrication for use in medical environments. The completed sensor is expected to form an integral part of a large versatile sensing system. For example, the biocompatible artificial skin, is predicted to be capable of sensing force, pressure, temperature, and humidity, and may be used in such applications as medical and robotic system.
Fabrication and characterization of AZ91/CNT magnesium matrix composites
Yong-Ha Park, Yong-Ho Park, Ik-Min Park, et al.
Carbon Nano Tube (CNT) reinforced AZ91 metal matrix composites (MMC) were fabricated by the squeeze infiltrated method. Properties of magnesium alloys have been improved by impurity reduction, surface treatment and alloy design, and thus the usage for the magnesium alloys has been extended recently. However there still remain barriers for the adaption of magnesium alloys for engineering materials. In this study, we report light-weight, high strength heat resistant magnesium matrix composites. Microstructural study and tensile test were performed for the squeeze infiltrated magnesium matrix composites. The wear properties were characterized and the possibility for the application to automotive power train and engine parts was investigated. It was found that the squeeze infiltration technique is a proper method to fabricate magnesium matrix composites reducing casting defects such as pores and matrix/reinforcement interface separation etc. Improved tensile and mechanical properties were obtained with CNT reinforcing magnesium alloys
Performance evaluation of a chemical fume extractor for indoor working environment improvement
The purpose of this study is to systematically evaluate the performance of a portable chemical fume extractor used for cleaning chemical fume in small work places. Four chemical liquids, a closed chamber, and a metal-oxide sensor were used to evaluate its performance. The experimental results show that the unit under test is able to extract high concentrations of the tested chemical vapors and the cleaning processes take 5 minutes in average to clean out a strong-smelling fume concentration of 29 ppm. The performance is evaluated in terms of the cleaning efficiency (η) and clean air delivery rate (CADR).
The analysis of surface treatment of PDMS on prostate cancer and smooth muscle cells
Cory Huggins, Smitha M. N. Rao, Kytai Nguyen, et al.
The analysis of cellular activity when exposed to polydimethylsiloxane (PDMS) is necessary as this material has been used in various applications such as tissue engineering and microfluidic devices for cellular studies due to the polymer's unique mechanical properties. In this particular study, we investigated the effects of corona surface treated PDMS with different cross-linker ratios on cellular activities by analyzing prostate cancer cell (PC-3) and vascular smooth muscle cell (VSMC) adhesion and proliferation. Both cell lines were subjected to a thin PDMS layer immediately after and 24 hours after corona treatment. The results indicated steady cell adhesion and proliferation rates for both smooth muscle and prostate cancer cells when seeded onto PDMS 24 hours after corona surface treatment, but significantly less cell adhesion when seeded immediately after activation and controls (PDMS without any treatment). These results would allow future PC-3 and VSMC experiments to be performed in a PDMS environment that is not detrimental for adhesion and proliferation.
Visible-light-driven TiO2 photocatalyst synthesis and photocatalytic properties
Vu Anh Tuan, Bui Thi Hai Linh, Hoang Yen, et al.
Nano TiO2 was synthesized by hydrothermal method. The sample was modified by doping transition metal ion (V, Cr and Fe) and non metal (N). Doped TiO2 samples were characterized by XRD (X-ray diffraction), FE-SEM (Fieldemission scanning electron microscopy) and UV-Vis (UV-Vis diffuse reflectance spectroscopy). Photocatalytic activity in mineralization of xylene (vapor phase), methylene blue and active dyer PR (liquid phase) were tested. In comparison to non-doped TiO2, V-,Cr-,Fe-doped TiO2 and N-doped TiO2 samples exhibited much higher photocatalytic activity using visible light instead of UV.
Investigation of repeatability of sol-gel iridium oxide pH sensor on flexible substrate
In this paper, we presented the fabrication process of miniature pH sensor arrays on flexible polymer substrates. The repeatability of the sensors based on sol-gel fabrication processes was investigated. The sensor repeatability was characterized with linearity, decay time, environmental parameter control and potential stability. Similar linear responses were found in different batches of sensor arrays. Near super- Nernstian responses were measured on each sensor with slope ranges from -71.6 to -110 mV/pH within a pH range between 2 and 12. The response times were compared in different batches. Six to twenty five seconds of average decay time were shown in each sample repeatedly. Three sensors showed the close potential response in different volumes of pH buffer solution. The sensor showed good stability in each step of the titration process between pH values of 1.8 and 11.9. The peak and saturated potential values presented high correlation with pH values with minor noises. The results showed good sensitivity, stability and repeatability using the sol-gel processes for iridium-oxide pH sensors on flexible substrates.
Study on the medical application of silver material
Min Han, Shan Li
There are several ways to kill the bacterium and treat the wound by use of silver material. The silver material also is a kind of sedative to keep people calm, especially for children. Because the bacterium resistance to the action of drug, the medical application of silver material should be paid attention to.