11,846 research outputs found

    A Review of Micro-Contact Physics for Microelectromechanical Systems (MEMS) Metal Contact Switches

    Get PDF
    Innovations in relevant micro-contact areas are highlighted, these include, design, contact resistance modeling, contact materials, performance and reliability. For each area the basic theory and relevant innovations are explored. A brief comparison of actuation methods is provided to show why electrostatic actuation is most commonly used by radio frequency microelectromechanical systems designers. An examination of the important characteristics of the contact interface such as modeling and material choice is discussed. Micro-contact resistance models based on plastic, elastic-plastic and elastic deformations are reviewed. Much of the modeling for metal contact micro-switches centers around contact area and surface roughness. Surface roughness and its effect on contact area is stressed when considering micro-contact resistance modeling. Finite element models and various approaches for describing surface roughness are compared. Different contact materials to include gold, gold alloys, carbon nanotubes, composite gold-carbon nanotubes, ruthenium, ruthenium oxide, as well as tungsten have been shown to enhance contact performance and reliability with distinct trade offs for each. Finally, a review of physical and electrical failure modes witnessed by researchers are detailed and examined

    Kassiopeia: A Modern, Extensible C++ Particle Tracking Package

    Full text link
    The Kassiopeia particle tracking framework is an object-oriented software package using modern C++ techniques, written originally to meet the needs of the KATRIN collaboration. Kassiopeia features a new algorithmic paradigm for particle tracking simulations which targets experiments containing complex geometries and electromagnetic fields, with high priority put on calculation efficiency, customizability, extensibility, and ease of use for novice programmers. To solve Kassiopeia's target physics problem the software is capable of simulating particle trajectories governed by arbitrarily complex differential equations of motion, continuous physics processes that may in part be modeled as terms perturbing that equation of motion, stochastic processes that occur in flight such as bulk scattering and decay, and stochastic surface processes occuring at interfaces, including transmission and reflection effects. This entire set of computations takes place against the backdrop of a rich geometry package which serves a variety of roles, including initialization of electromagnetic field simulations and the support of state-dependent algorithm-swapping and behavioral changes as a particle's state evolves. Thanks to the very general approach taken by Kassiopeia it can be used by other experiments facing similar challenges when calculating particle trajectories in electromagnetic fields. It is publicly available at https://github.com/KATRIN-Experiment/Kassiopei

    Ligand-Receptor Interactions

    Full text link
    The formation and dissociation of specific noncovalent interactions between a variety of macromolecules play a crucial role in the function of biological systems. During the last few years, three main lines of research led to a dramatic improvement of our understanding of these important phenomena. First, combination of genetic engineering and X ray cristallography made available a simultaneous knowledg of the precise structure and affinity of series or related ligand-receptor systems differing by a few well-defined atoms. Second, improvement of computer power and simulation techniques allowed extended exploration of the interaction of realistic macromolecules. Third, simultaneous development of a variety of techniques based on atomic force microscopy, hydrodynamic flow, biomembrane probes, optical tweezers, magnetic fields or flexible transducers yielded direct experimental information of the behavior of single ligand receptor bonds. At the same time, investigation of well defined cellular models raised the interest of biologists to the kinetic and mechanical properties of cell membrane receptors. The aim of this review is to give a description of these advances that benefitted from a largely multidisciplinar approach

    하전된 에어로졸을 이용한 삼차원 금속 나노구조물 어레이의 적층 제조

    Get PDF
    학위논문(박사)--서울대학교 대학원 :공과대학 기계항공공학부(멀티스케일 기계설계전공),2020. 2. 최만수.Additive manufacturing, known as three-dimensional (3D) printing, aims to create any geometry over a large area in a fast, cost-effective manner. Although 3D-printed metal nanostructures are indispensable in many applications, reported 3D printing techniques for metals cannot achieve nanoscale resolution, fast speed, high purity, and intricate geometry simultaneously. Here, we introduce an aerosol 3D nanoprinting technique for manufacturing metal 3D nanostructure arrays in a parallel fashion at atmospheric pressure. Converging electric field lines caused by ion induced nanoscopic electrostatic lens guide charged aerosols to a precise location ensuring nanoscale resolution on a substrate with a programmed manner, and it can therefore be treated as a drawing tool for 3D nanostructures. This technique exhibits two complementary modes: tip-directed growth and surface writing modes; the former enables printing various 3D nanostructures with flexibility including 3D nanopillar-like (e.g., vertical and overhanging nanopillars, helices) and 3D nanowall-like structures and the latter enables writing nanostructures following the repeated movement of nanostage such as ring and the letter 3D structures. Unlike the existing 3D printing methods, the technique adopts a completely dry process that does not need any polymers or inks. The flexible choice of pure metals allows printing composite metal structures (e.g., Cu/Pd). High purity of nanoparticles within the structures enable sintering upon thermal treatment, thereby imparting enhanced mechanical strength (electrical conductivity shows only 6 times higher than bulk and elastic modulus has 10.5GPa). Further, we develop a phenomenological model to predict the resulting 3D geometry, which is consistent with the experimental results. The demonstrated capabilities foreshadow a new paradigm in nanofabrication.삼차원 (3D) 프린팅으로 알려진 적층 가공은 형상에 구애받지 않고 적은 비용으로 넓은 면적에 신속한 프린팅하는 것을 목표로 한다. 특히, 3D 프린팅 된 금속 나노 구조물은 다양한 분야에서 광범위한 수요가 존재하나 3D 나노프린팅 기술 연구는 대부분 고분자 물질에 집중되어 있어 금속 3D 나노프린팅 기술은 나노 스케일 해상도, 빠른 속도, 고순도 및 복잡한 형상을 동시에 달성하지 못했다. 이러한 문제점들을 해결하고자 우리는 대기압에서 병렬 방식의 금속 3D 나노 구조물 제작이 가능한 에어로졸 3D 나노프린팅 기술을 개발했다. 부유형 마스크 표면에 축적된 이온들에 의해 왜곡된 형상의 전기장에 직교하는 전기력선들을 따라 하전된 금속 나노입자들은 나노스테이지 위에 부착된 기판에 축적되고, 자유로운 3D 금속 나노프린팅을 가능하게 했다. 이 기술은 나노스테이지의 이동 속도에 따라 두가지 모드로 구분될 수 있다. 상대적으로 나노스테이지의 움직임이 느린 팁 지향적 모드에서는 수직 및 기울기를 가진 나노스케일의 기둥과 나선 형상을 인쇄할 수 있고 이와 반대로 나노스테이지의 움직임이 빠른 쓰기 모드에서는 기판에 나노스케일로 원하는 형상을 쓸 수가 있었다. 이 공정은 대기압 상에서 이루어지며 액상 등의 고분자 물질이 필요하지 않기 때문에 높은 순도의 금속 나노구조물을 제작할 수 있으며 사용 가능한 금속의 제한이 없으며, 프린팅된 구조물의 강화를 통해 높은 전기 전도도와 기계적 강도를 가질 수 있다. 또한, 이론적 분석 모델을 통해 3D 구조물의 형상을 예측할 수 있는 모델을 개발했으며 실험적 결과와 일치하는 것을 확인해 사용자 친화적인 삼차원 나노프린팅 기술로 발전할 수 있음을 보였다. 우리는 이 기술이 3D 나노프린팅 연구 분야에 새로운 패러다임을 가져와 여러 분야에 적용되는 초석이 될 수 있기를 기대한다.Chapter 1. Introduction 1 1.1. Research Background 2 1.2. Research Objectives 4 1.3. References 5 Chapter 2. Manufacturing 3D metal nanostructure via Ion Assisted Aerosol Lithography 11 2.1. Introduction 12 2.2. Method 14 2.2.1. Nanoparticle generation and characteristics 14 2.2.2. Ion Assisted Aerosol Lithography 18 2.2.3. Concept for 3D metal nanoprinting via ion assisted aerosol lithography 22 2.3. Results and Discussion 30 2.3.1. Tip-directed growth of 3D metal nanostructure 30 2.3.2. Surface writing of 3D metal nanostructure 49 2.3.3. Property analysis of 3D metal nanostructure 52 2.4. Summary 58 2.5. References 59 Chapter 3. Numerical and Mathematical Analysis of 3D metal nanostructure growth 61 3.1. Introduction 62 3.2. Simulation of particle trajectory by solving Langevins equation 64 3.3. Phenomenological model for 3D structural growth 68 3.4. Summary 86 3.5. References 87 Chapter 4. Concluding Remarks 88 Acknowledgement 91 Abstract (in Korean) 92Docto

    Electrowetting: from basics to applications

    Get PDF
    Electrowetting has become one of the most widely used tools for manipulating tiny amounts of liquids on surfaces. Applications range from 'lab-on-a-chip' devices to adjustable lenses and new kinds of electronic displays. In the present article, we review the recent progress in this rapidly growing field including both fundamental and applied aspects. We compare the various approaches used to derive the basic electrowetting equation, which has been shown to be very reliable as long as the applied voltage is not too high. We discuss in detail the origin of the electrostatic forces that induce both contact angle reduction and the motion of entire droplets. We examine the limitations of the electrowetting equation and present a variety of recent extensions to the theory that account for distortions of the liquid surface due to local electric fields, for the finite penetration depth of electric fields into the liquid, as well as for finite conductivity effects in the presence of AC voltage. The most prominent failure of the electrowetting equation, namely the saturation of the contact angle at high voltage, is discussed in a separate section. Recent work in this direction indicates that a variety of distinct physical effects¿rather than a unique one¿are responsible for the saturation phenomenon, depending on experimental details. In the presence of suitable electrode patterns or topographic structures on the substrate surface, variations of the contact angle can give rise not only to continuous changes of the droplet shape, but also to discontinuous morphological transitions between distinct liquid morphologies. The dynamics of electrowetting are discussed briefly. Finally, we give an overview of recent work aimed at commercial applications, in particular in the fields of adjustable lenses, display technology, fibre optics, and biotechnology-related microfluidic devices

    Fog dispersion

    Get PDF
    The concept of using the charged particle technique to disperse warm fog at airports is investigated and compared with other techniques. The charged particle technique shows potential for warm fog dispersal, but experimental verification of several significant parameters, such as particle mobility and charge density, is needed. Seeding and helicopter downwash techniques are also effective for warm fog disperals, but presently are not believed to be viable techniques for routine airport operations. Thermal systems are currently used at a few overseas airports; however, they are expensive and pose potential environmental problems
    corecore