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Fiber Bundle Topology Optimization for Surface Flows

Chinese Journal of Mechanical Engineering 2024年第3期37卷 236-264页

作者： Yongbo Deng Weihong Zhang Jihong Zhu Yingjie Xu jan g korvink State Key Laboratory of Applied Optics Changchun Institute of OpticsFine Mechanics and PhysicsChinese Academy of SciencesChangchun 130033China State IJR Center of Aerospace Design and Additive Manufacturing Northwestern Polytechnical UniversityXi’an 710072China Institute of Microstructure Technology(IMT) Karlsruhe Institute of Technology(KIT)Hermann-von-Helmholtzplatz 176344 Eggenstein-LeopoldshafenGermany

This paper presents a topology optimization approach for the surface flows on variable design *** this approach,the matching between the pattern of a surface flow and the 2-manifold used to define the pattern can be optimized,where the 2-manifold is implicitly defined on another fixed 2-manifold named as the base *** fiber bundle topology optimization approach is developed based on the description of the topological structure of the surface flow by using the differential geometry concept of the fiber *** material distribution method is used to achieve the evolution of the pattern of the surface *** evolution of the implicit 2-manifold is realized via a homeomorphous *** design variable of the pattern of the surface flow and that of the implicit 2-manifold are regularized by two sequentially implemented surface-PDE *** two surface-PDE filters are coupled,because they are defined on the implicit 2-manifold and base manifold,*** surface Navier-Stokes equations,defined on the implicit 2-manifold,are used to describe the surface *** fiber bundle topology optimization problem is analyzed using the continuous adjoint method implemented on the first-order Sobolev *** numerical examples have been provided to demonstrate this approach,where the combination of the viscous dissipation and pressure drop is used as the design objective.

关键词： Fiber bundle Topology optimization 2-manifold Surface flow Material distribution method Porous medium model

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Design of small-scale gradient coils in magnetic resonance imaging by using the topology optimization method

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Chinese Physics B 2018年第5期27卷 91-100页

作者： Hui Pan Feng Jia Zhen-Yu Liu Maxim Zaitsev Juergen Hennig jan g korvink Changchun Institute of Optics Fine Mechanics and PhysicsChinese Academy of SciencesChangchun 130033China University of Chinese Academy of Sciences Beijing 100049China Deptartment of Radiology Medical PhysicsMedical Center University of FreihurgFaculty of MedicineUniversity of FreiburgFreiburg 79106Germany Institute of Microstructure Technology Karlsruhe Institute of Technology(KIT)Karlsruhe 76344Germany

A topology optimization method based on the solid isotropic material with penalization interpolation scheme is utilized for designing gradient coils for use in magnetic resonance *** the popular stream function method,the proposed method has design variables that are the distribution of conductive material.A voltage-driven transverse gradient coil is proposed to be used as micro-scale magnetic resonance imaging(MRI)gradient coils,thus avoiding introducing a coil-winding pattern and simplifying the coil *** proposed method avoids post-processing errors that occur when the continuous current density is approximated by discrete wires in the stream function *** feasibility and accuracy of the method are verified through designing the z-gradient and y-gradient coils on a cylindrical *** design results show that the proposed method can provide a new coil layout in a compact design space.

关键词： topology optimization method gradient coils solid isotropic material with penalization magnetic resonance imaging

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Accurate surface normal representation to facilitate gradient coil optimization on curved surface

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Magnetic Resonance Letters 2023年第1期3卷 67-84,I0004页

作者： Hao Ren Hui Pan Feng Jia jan g.korvink Zhenyu Liu Changchun Institute of Optics Fine Mechanics and PhysicsChinese Academy of SciencesChangchun130033China School of Optoelectronics University of Chinese Academy of SciencesBeijing101499China Department of Radiology Medical PhysicsMedical Center University of FreiburgFaculty of MedicineUniversity of FreiburgFreiburg79110Germany Institute of Microstructure Technology Karlsruhe Institute of Technology(KIT)Karlsruhe76049Germany

The design methods for gradient coils are mostly based on discrete extrinsic methods(e.g.,the BioteSavart integration calculation),for which the surface normal vector strongly influences any numerical calculation of the discretized *** studies are mostly based on regular or analytical surfaces,which allow normal vectors to be expressed *** certain applications,design methods for extending currentcarrying surfaces from developable or analytic geometries to arbitrary surfaces generated from a scanned point cloud are *** key task is to correctly express the discretized normal vectors to ensure geometrical accuracy of the designed ***,it has been proven that applying a Delaunay triangulation to approximate a smooth surface can result in the discrete elemental normal vectors converging to those of the original ***,this article uses Delaunay triangulation to expand upon previous design methods so that they encompass arbitrary piecewise continuous *** design methods,the stream function and the so-called solid isotropic material with penalization(SIMP)method,are used to design circumvolute and noncircumvolute gradient coils on general surfaces.

关键词： gradient coils Delaunay triangulation Stream function SIMP method

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Molecular Dynamics Simulations of Nanoparticle Interactions with a Planar Wall:Does Shape Matter?

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Communications in Computational Physics 2013年第3期13卷 900-915页

作者： Andreas Fuchs David Kauzlaric Andreas greiner Sauro Succi jan.g.korvink Laboratory for Simulation Department of Microsystems Engineering(IMTEK)University of FreiburgGeorges-Kohler-Allee 10379110 FreiburgGermany School of Soft Matter Research Freiburg Institute for Advanced StudiesUniversity of FreiburgAlbertstr.1979104 FreiburgGermany Istituto Applicazioni Calcolo CNRvia dei Taurini 900185RomaItaly

We investigate the hydrodynamic interactions of spherical colloidal nano particles and nano tetrahedra near a planar wall by means of molecular dynamics(MD)simulations of rigid particles within an all-atom *** both spherical and nano-tetrahedral particles,we find that the parallel and perpendicular components of the local diffusion coefficient and viscosity,show good agreement with hydrodynamic theory of Fax´en and *** provides further evidence that low perturbations from sphericality of a nanoparticle’s shape has little influence on its local diffusive behaviour,and that for this particular case,the continuum theory fluid dynamics is valid even down to molecular scales.

关键词： Molecular dynamics simulation nanoparticle hydrodynamic interaction

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Portable dielectrophoresis for biology:ADEPT facilitates cell trapping,separation,and interactions

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Microsystems & Nanoengineering 2024年第2期10卷 193-205页

作者： Lourdes Albina Nirupa Julius Dora Akgül gowri Krishnan Fabian Falk jan korvink Vlad Badilita Department Institute of Microstructure TechnologyKarlsruhe Institute of TechnologyHermann-von-Helmholtz-Platz 1Eggenstein-Leopoldshafen76344Baden-WürttembergGermany

Dielectrophoresis is a powerful and well-established technique that allows label-free,non-invasive manipulation of cells and particles by leveraging their electrical *** practical implementation of the associated electronics and user interface in a biology laboratory,however,requires an engineering background,thus hindering the broader adoption of the *** order to address these challenges and to bridge the gap between biologists and the engineering skills required for the implementation of DEP platforms,we report here a custom-built,compact,universal electronic platform termed ADEPT(adaptable dielectrophoresis embedded platform tool)for use with a simple microfluidic chip containing six *** versatility of the open-source platform is ensured by a custom-developed graphical user interface that permits simple reconfiguration of the control signals to address a wide-range of specific applications:(i)precision positioning of the single bacterium/cell/particle in the micrometer range;(ii)viability-based separation by achieving a 94%efficiency in separating live and dead yeast;(iii)phenotype-based separation by achieving a 96%efficiency in separating yeast and Bacillus subtilis;(iv)cell–cell interactions by steering a phagocytosis process where a granulocyte engulfs *** RgB-S ***,the set of experiments and the platform form a complete basis for a wide range of possible applications addressing various biological questions exploiting the plug-and-play design and the intuitive gUI of ADEPT.

关键词： Together separation separating

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Integrated impedance sensing of liquid sample plug flow enables automated high throughput NMR spectroscopy

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Microsystems & Nanoengineering 2021年第2期7卷 177-193页

作者： Omar Nassar Mazin Jouda Michael Rapp Dario Mager jan g.korvink Neil MacKinnon Institute of Microstructure Technology Karlsruhe Institute of Technology(KIT)Hermann-von-Helmholtz-Platz 176344Eggenstein-LeopoldshafenGermany

A novel approach for automated high throughput NMR spectroscopy with improved mass-sensitivity is accomplished by integrating microfluidic technologies and micro-NMR resonators.A flow system is utilized to transport a sample of interest from outside the NMR magnet through the NMR detector,circumventing the relatively vast dead volume in the supplying tube by loading a series of individual sample plugs separated by an immiscible *** dual-phase flow demands a real-time robust sensing system to track the sample position and velocities and synchronize the NMR *** this contribution,we describe an NMR probe head that possesses a microfluidic system featuring:(i)a micro saddle coil for NMR spectroscopy and(ii)a pair of interdigitated capacitive sensors flanking the NMR detector for continuous position and velocity monitoring of the plugs with respect to the NMR *** system was successfully tested for automating flow-based measurement in a 500 MHz NMR system,enabling high resolution spectroscopy and NMR sensitivity of 2.18 nmol s1/2 with the flow sensors in *** flow sensors featured sensitivity to an absolute difference of 0.2 in relative permittivity,enabling distinction between most common *** was demonstrated that a fully automated NMR measurement of nine individual 120μL samples could be done within 3.6 min or effectively 15.3 s per sample.

关键词： flow spectroscopy enable

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Electrospun carbon nanofibre-assisted patterning of metal oxide nanostructures

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Microsystems & Nanoengineering 2022年第3期8卷 263-276页

作者： Monsur Islam Christian Dolle Ahsana Sadaf Peter g.Weidler Bharat Sharma Yolita M.Eggeler Dario Mager jan g.korvink Institute of Microstructure Technology Karlsruhe Institute of TechnologyHermann-von-Helmholtz-Platz 176344 Eggenstein-LeopoldshafenGermany Microscopy of Nanoscale Structures&Mechanisms(MNM) Laboratory for Electron Microscopy(LEM)Karlsruhe Institute of TechnologyEngesserstr.7D-76131 KarlsruheGermany Institut fur Funktionlle grenzflachen Karlsruhe Institute of TechnologyHermann-von-Helmholtz-Platz 176344 Eggenstein-LeopoldshafenGermany

This work establishes carbon nanofibre-mediated patterning of metal oxide nanostructures,through the combination of electrospinning and vapor-phase transport *** of a suitable precursor with subsequent carbonization results in the patterning of catalyst gold nanoparticles embedded within carbon *** vapor-phase transport growth,these nanofibres allow preferential growth of one-dimensional metal oxide nanostructures,which grow radilly outward from the nanofibril axis,ielding a hairy caterpilr-ike *** synthesis of metal oxide caterpilars is demonstrated using zinc oxide,indium oxide,and tin *** and substrate temperatures play the most crucial role in determining the morphology of the metal oxide caterpillars,whereas the distribution of the nanofibres also has a significant impact on the overall *** the current methodology with near-field electrospinning further facilitates user-defined custom patterning of metal oxide caterpllr-like structures.

关键词： fibre carbon patterning

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Pyrolysis-induced shrinking of threedimensional structures fabricated by twophoton polymerization:experiment and theoretical model

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Microsystems & Nanoengineering 2019年第1期5卷 303-315页

作者： Braulio Cardenas-Benitez Carsten Eschenbaum Dario Mager jan g.korvink Marc JMadou Uli Lemmer Israel De Leon Sergio O.Martinez-Chapa School of Engineering and Sciences Tecnologico de MonterreyAv.Eugenio Garza Sada 2501 Sur64849 MonterreyNLMexico Light Technology Institute Karlsruhe Institute of Technology(KIT)Engesserstraße 1376131 KarlsruheGermany Institute of Microstructure Technology Karlsruhe Institute of Technology(KIT)Hermann-von-Helmholtz-Platz 176344 Eggenstein-LeopoldshafenGermany Department of Mechanical and Aerospace Engineering University of CaliforniaIrvine4200 Engineering GatewayIrvineCA 92697USA

The introduction of two-photon polymerization(TPP)into the area of Carbon Micro Electromechanical Systems(CMEMS)has enabled the fabrication of three-dimensional glassy carbon nanostructures with geometries previously unattainable through conventional UV *** of TPP structures conveys a characteristic reduction of feature size—one that should be properly estimated in order to produce carbon microdevices with *** this work,we studied the volumetric shrinkage of TPP-derived microwires upon pyrolysis at 900℃.Through this process,photoresist microwires thermally decompose and shrink by as much as 75%,resulting in glassy carbon nanowires with linewidths between 300 and 550 *** after the thermal decomposition induced by the pyrolysis step,the linewidth of the carbon nanowires was found to be dependent on the TPP exposure *** have also found that the thermal stress induced during the pyrolysis step not only results in axial elongation of the nanowires,but also in buckling in the case of slender carbon nanowires(for aspect ratios greater than 30).Furthermore,we show that the calculated residual mass fraction that remains after pyrolysis depends on the characteristic dimensions of the photoresist microwires,a trend that is consistent with several works found in the *** phenomenon is explained through a semi-empirical model that estimates the feature size of the carbon structures,serving as a simple guideline for shrinkage evaluation in other designs.

关键词： lithography pyrolysis structures

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喷墨打印微制造技术

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作者： (德)简 g. 考文科(jan g. korvink) (英)帕特里克 J. 史密斯(Patrick J. Smith) (韩)申东勇

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glassy carbon microelectrodes minimize induced voltages,mechanical vibrations,and artifacts in magnetic resonance imaging

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Microsystems & Nanoengineering 2019年第1期5卷 89-99页

作者： Surabhi Nimbalkar Erwin Fuhrer Pedro Silva Tri Nguyen Martin Sereno Sam Kassegne jan korvink MEMS Research Lab Department of Mechanical EngineeringCollege of EngineeringSan Diego State University5500 Campanile DriveSan DiegoCA 92182USA NSF-ERC Center for Neurotechnology(CNT) SeattleWAUSA Institute of Microstructure Technology–Karlsruhe Institute of Technology Hermann-von-Helmholtz-Platz76344 Eggenstein-LeopoldshafenGermany Magnetic Resonance Imaging Lab San Diego State UniversitySan DiegoCA 92182USA

The recent introduction of glassy carbon(gC)microstructures supported on flexible polymeric substrates has motivated the adoption of gC in a variety of implantable and wearable *** probes such as electrocorticography and penetrating shanks with gC microelectrode arrays used for neural signal recording and electrical stimulation are among the first beneficiaries of this *** the expected proliferation of these neural probes and potential clinical adoption,the magnetic resonance imaging(MRI)compatibility of gC microstructures needs to be established to help validate this potential in clinical ***,we present gC microelectrodes and microstructures—fabricated through the carbon micro-electro-mechanical systems process and supported on flexible polymeric substrates—and carry out experimental measurements of induced vibrations,eddy currents,and *** induced vibration,induced voltage,and MRI experiments and finite element modeling,we compared the performances of these gC microelectrodes against those of conventional thin-film platinum(Pt)microelectrodes and established that gC microelectrodes demonstrate superior magnetic resonance compatibility over standard metal thin-film ***,we demonstrated that gC microelectrodes experienced no considerable vibration deflection amplitudes and minimal induced currents,while Pt microelectrodes had significantly larger *** also showed that because of their low magnetic susceptibility and lower conductivity,the gC microelectrodes caused almost no susceptibility shift artifacts and no eddy-current-induced artifacts compared to Pt *** together,the experimental,theoretical,and finite element modeling establish that gC microelectrodes exhibit significant MRI compatibility,hence demonstrating clear clinical advantages over current conventional thin-film materials,further opening avenues for wider adoption of gC microelectrodes in chronic clinical app

关键词： magnetic compatibility resonance

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