다중혈관 관상동맥 환자에서 y-문합을 이용하여 양쪽 내흉동맥만을 사용한 우회술의 조기 성적

Microfabricated integrated circuits revolutionized computation by vastly reducing the space, labor, and time required for calculations. Microfluidic systems hold similar promise for the large-scale automation of chemistry and biology, suggesting the possibility of numerous experiments performed rapidly and in parallel, while consuming little reagent. While it is too early to tell whether such a vision will be realized, significant progress has been achieved, and various applications of significant scientific and practical interest have been developed. Here a review of the physics of small volumes (nanoliters) of fluids is presented, as parametrized by a series of dimensionless numbers expressing the relative importance of various physical phenomena. Specifically, this review explores the Reynolds number Re, addressing inertial effects; the Peclet number Pe, which concerns convective and diffusive transport; the capillary number Ca expressing the importance of interfacial tension; the Deborah, Weissenberg, and elasticity numbers De, Wi, and El, describing elastic effects due to deformable microstructural elements like polymers; the Grashof and Rayleigh numbers Gr and Ra, describing density-driven flows; and the Knudsen number, describing the importance of noncontinuum molecular effects. Furthermore, the long-range nature of viscous flows and the small device dimensions inherent in microfluidics mean that the influence of boundaries is typically significant. A variety of strategies have been developed to manipulate fluids by exploiting boundary effects; among these are electrokinetic effects, acoustic streaming, and fluid-structure interactions. The goal is to describe the physics behind the rich variety of fluid phenomena occurring on the nanoliter scale using simple scaling arguments, with the hopes of developing an intuitive sense for this occasionally counterintuitive world.

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Microfluidics: Fluid physics at the nanoliter scale

介绍了Kirk—Othmer Encyclopedia of Chemical Technology（化工技术百科全书）（第五版）电子图书网络版数据库，并对该数据库使用方法和检索途径作出了说明，且结合实例简单地介绍了该数据库的检索方法。

Kirk-Othmer Encyclopedia of Chemical Technology数据库介绍及实例

基礎講座 電気泳動(Electrophoresis)

This paper presents a review of silicon micromachined accelerometers and gyroscopes. Following a brief introduction to their operating principles and specifications, various device structures, fabrication, technologies, device designs, packaging, and interface electronics issues, along with the present status in the commercialization of micromachined inertial sensors, are discussed. Inertial sensors have seen a steady improvement in their performance, and today, microaccelerometers can resolve accelerations in the micro-g range, while the performance of gyroscopes has improved by a factor of 10/spl times/ every two years during the past eight years. This impressive drive to higher performance, lower cost, greater functionality, higher levels of integration, and higher volume will continue as new fabrication, circuit, and packaging techniques are developed to meet the ever increasing demand for inertial sensors.

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Micromachined inertial sensors

This paper describes electrothermal microactuators that generate rectilinear displacements and forces by leveraging deformations caused by localized thermal stresses. In one manifestation, an electric current is passed through a V-shaped beam anchored at both ends, and thermal expansion caused by joule heating pushes the apex outward. Analytical and finite element models of device performance are presented along with measured results of devices fabricated using electroplated Ni and p/sup ++/ Si as structural materials. A maskless process extension for incorporating thermal and electrical isolation is described. Nickel devices with 410-/spl mu/m-long, 6-/spl mu/m-wide, and 3-/spl mu/m-thick beams demonstrate 10 /spl mu/m static displacements at 79 mW input power; silicon devices with 800-/spl mu/m-long, 13.9-/spl mu/m-wide, and 3.7-/spl mu/m-thick beams demonstrate 5 /spl mu/m displacement at 180 mW input power. Cascaded silicon devices using three beams of similar dimensions offer comparable displacement with 50-60% savings in power consumption. The peak output forces generated are estimated to be in the range from 1 to 10 mN for the single beam devices and from 0.1 to 1 mN for the cascaded devices. Measured bandwidths are /spl ap/700 Hz for both. The typical drive voltages used are /spl les/12 V, permitting the use of standard electronic interfaces that are generally inadequate for electrostatic actuators.

Bent-beam electrothermal actuators-Part I: Single beam and cascaded devices

This paper describes a micro-electro-discharge machining (micro-EDM) technique that uses electrode arrays to achieve high parallelism and throughput in the machining. It explores constraints in the fabrication and usage of high aspect ratio LIGA-fabricated electrode arrays, as well as the limits imposed by the pulse discharge circuits on machining rates. An array of 400 Cu electrodes with 20 /spl mu/m diameter was used to machine perforations in 50-/spl mu/m-thick stainless steel. To increase the spatial and temporal multiplicity of discharge pulses, arrays of electrodes with lithographically fabricated interconnect and block-wise independent pulse control resistance-capacitance (RC) circuits are used, resulting in >100/spl times/ improvement in throughput compared to single electrodes. However, it was found to compromise surface smoothness. A modified pulse generation scheme that exploits the parasitic capacitance of the interconnect offers similarly high machining rates and is more amenable to integration. Stainless steel workpieces of 100 /spl mu/m thickness were machined by 100 /spl mu/m/spl times/100 /spl mu/m square cross-section electrodes using in 85 s using an 80-V power supply. Surface smoothness was unaffected by electrode multiplicity. Using electrode arrays with four circuits, batch production of 36 WC-Co gears with 300 /spl mu/m outside diameter and 70 /spl mu/m thickness in 15 min is demonstrated.

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Batch mode micro-electro-discharge machining

We examine a new class of sensitive and compact passive strain sensors that utilize a pair of narrow bent beams with an apex at their mid-points. The narrow beams amplify and transform deformations caused by residual stress into opposing displacements of the apices, where vernier scales are positioned to quantify the deformation. An analytical method to correlate vernier readings to residual stress is outlined, and its results are corroborated by finite-element modeling. It is shown that tensile and compressive residual stress levels below 10 MPa, corresponding to strains below 6/spl times/10/sup -5/ can be measured in a 1.5-/spl mu/m-thick layer of polysilicon using a pair of beams that are 2 /spl mu/m wide, 200 /spl mu/m long, and bent 0.05 radians (2.86/spl deg/) to the long axis of the device. Experimental data is presented from bent-beam strain sensors that were fabricated from boron-doped single crystal silicon using the dissolved wafer process and from polycrystalline silicon using surface micromachining. Measurements from these devices agree well with those obtained by other methods.

Bent-beam strain sensors

For Part I see L. Que, J.S. Park and Y.B. Gianchandani, ibid., vol.10, pp.247-54 (2001). This paper reports on the use of bent-beam electrothermal actuators for the purpose of generating rotary and long-throw rectilinear displacements. The rotary displacements are achieved by orthogonally arranged pairs of cascaded actuators that are used to rotate a gear. Devices were fabricated using electroplated Ni, p/sup ++/ Si, and polysilicon as structural materials. Displacements of 20-30 /spl mu/m with loading forces >150 /spl mu/N at actuation voltages 200 /spl mu/N at displacements >100 /spl mu/m were measured.

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Bent-beam electrothermal actuators-Part II: Linear and rotary microengines

A single-sided bulk silicon dissolved wafer process that has been used to fabricate several different micromechanical structures is described. It involves the simultaneous processing of a glass wafer and a silicon wafer, which are eventually bonded together electrostatically. The silicon wafer is then dissolved to leave heavily boron doped devices attached to the glass substrate. Overhanging features can be fabricated without additional masking steps. It is also possible to fabricate elements with thickness-to-width aspect ratios in excess of 10:1. Measurements of various kinds of laterally driven comb structures processed in this manner, some of which are intended for application in a scanning thermal profilometer, are described. They comprise shuttle masses supported by beams that are 160-360 mu m long, 1-3 mu m wide, and 3-10 mu m thick. Some of the shuttles are mounted with probes that overhang the edge of the die by 250 mu m. Resonant frequencies from 18 to 100 kHz and peak-to-peak displacements up to 18 mu m have been measured. >

Yogesh B. Gianchandani

Papers

Bent-beam electrothermal actuators-Part I: Single beam and cascaded devices

Batch mode micro-electro-discharge machining

Bent-beam strain sensors

Bent-beam electrothermal actuators-Part II: Linear and rotary microengines

A bulk silicon dissolved wafer process for microelectromechanical devices