Key Engineering Materials Vols. 326-328

Abstract: We design and fabricate a novel flexural plate wave (FPW) accelerometer which has wide working range and improved sensitivity. A bridge as well as a rectangular diaphragm with a proof mass has been considered for a wave propagation medium to enhance the performance. The performance improvement is also verified with the bridge structure and the existence of the proof mass in the simulation results.

Abstract: This paper presents a design and performance evaluation of a valveless micropump fabricated from polydimethylsiloxane (PDMS) based on molding techniques. A circular lightweight piezo-composite actuator (LIPCA) was successfully developed for the actuating diaphragm of the micropump. The LIPCA is a composite actuator designed and fabricated with piezoceramics in combination with carbon fabric and glass epoxy. Numerical and experimental methods were used to investigate the performance of the circular LIPCA. The LIPCA was glued to a PDMS membrane to form the diaphragm of the micropump. The diaphragm has several advantages, such as high displacement, dome-shaped deformation and geometrically independent actuation profile. The diaphragm based on a LIPCA 9 mm in diameter produces a deflection of 27 μm at the applied voltage of ± 200 V and a frequency of 1 Hz. The micropump has a maximum water flow rate of 0.95 ml/min and a maximum backpressure of 3.8 kPa. The merits of the present micropump are low cost, ease of manufacturing and high level of effectiveness. The proposed LIPCA is proven to be a promising alternative to the conventional piezoelectric actuator used in micropumps.

Abstract: In this paper, a digital rebalance loop for MEMS gyroscope is designed and its performance test is performed. First, the system model of MEMS gyroscope is established by dynamic analysis. Then, the digital rebalance loop is designed using modern control technique. The performance of the digital rebalance loop is compared with that of conventional PID rebalance loop. Through frequency response analysis using MATLAB and experiments using a real MEMS gyroscope and digital controller, which is realized using digital signal processor (DSP), it is confirmed that the controller improves the performance of the gyroscope.

Abstract: In this paper, the behavior of microparticles subjected to the AC electric fields generated by planar microelectrode systems is studied. Microelectrodes including interdigitated array, castellated array, and jagged array are constructed using microfabrication techniques. Micron-sized latex beads are used to study their movements. Positive and negative dielectrophoresis (DEP) are studied. In the interdigitated electrodes, particles experiencing n-DEP are levitated stably to certain heights where the vertical DEP force is balanced by the gravitational force. The levitation heights of the particles are measured using the consecutively focusing method. The results provide significant instructions for the dielectrophoretic manipulation and separation of bioparticles.

Abstract: A novel selective metallization process to fabricate the fine conductive line based on drop-on-demand (DoD) inkjet printing was studied. Direct inkjet printing is an alternative and costeffective technology for patterning and fabricating objects directly from design or image files without making masks and patterns. The conductive ink used in this experiment consists of 1 to 50 nm silver particles that are homogeneously suspended in an organic carrier. A piezo-electric inkjet print head driven by a bipolar voltage signal is used to dispense 20-40μm diameter droplets. Repeatability of circuitry fabrication is closely related to the formation of steady, satellite-free droplets. Therefore, the ability to form small and stable droplets with a same size, constant velocity and the correct flight angle must be taken into consideration for fine and precise conductive lines. In this study, parameters affecting the pattern formation such as drop formation, drop placement accuracy and velocity deviation between each nozzle have been investigated. As a result, direct inkjet patterning systems equipped with several functioning modules and fine metallic patterns have been developed.

Abstract: This paper proposes a method of applying Cu nanoparticles on the surface of miniature specimen for micro-deformation measurement. The microscope image processing system, making and preparation of Cu nanoparticles are described. Use of the nanoparticles on a miniature specimen to determine the Young’s modulus is demonstrated through a tensile testing with an image resolution of 0.3 μm/pixel. Comparable well result is shown and discussed.

Abstract: The strength of micro heat exchanger under pressure is studied in this paper. Micro heat exchanger is made with brazing technology. It is constructed of stainless steel thin plates with micro channels and in/out port for fluid flow. Micro channels in thin plates are formed by etching and all parts including thin plates are joined by brazing. The study on the strength under pressure is performed by structural analysis. For structural analysis, one layer of micro heat exchanger body is considered. It is composed of thin plate with micro channel and brazing filler which is used to join thin plates. This paper shows the tendency of stress behavior and gives design guideline of micro heat exchanger.

Abstract: This paper presents a droplet-based micro chemical plant with the chemical preparation, volume-fragmentation reaction and continuous separation of product with quantitative evaluation. It consists of a cross-channel network to prepare the droplet-based chemicals, a bifurcation channel to obtain the volume fragmentation of droplet and the pelican mouth separator to extract the reaction-completed chemicals.

Abstract: Interfacial residual stresses play an important role in the mechanical properties. In this paper, the interfacial residual stresses of SCI/Epoxy composites were determined using a novel technique-microphotoelastic method. The thermal residual stress field was also numerically simulated using a finite element software
MSC.MARC. The difference and the similarities between the experimental results and the simulation of FEM analysis were discussed and the availability of the method was preliminarily certified.

Abstract: As advanced ferritic/martensitic heat-resistant steels generally have a complex structure consisting of several microstructural units (lath, block, packet, and prior austenite grain), it is very hard to separate the contribution of each microstructural unit (or its each boundary) to the strengthening mechanism in such steels. Here we explore the role of each microstructural unit in strengthening of advanced high Cr steel through nanoindentation experiments performed at different load levels. Nanoindentation results are analyzed by comparing with microstructural observations and discussed in terms of prevailing descriptions of strengthening mechanism.