Jan Lienemann | Albert-Ludwigs-University of Freiburg (original) (raw)

Papers by Jan Lienemann

Springer eBooks, Nov 7, 2006

ABSTRACT Electrowetting is an elegant method to realize the motion, dispensing, splitting, and mi... more ABSTRACT Electrowetting is an elegant method to realize the motion, dispensing, splitting, and mixing of single droplets in a microfluidic system without the need for any mechanical—and fault-prone—components. By only applying an electric voltage, the interfacial energy of the fluid–solid interface is altered and the contact line of the droplet is changed. However, since the droplet shape is usually heavily distorted, it is difficult to estimate the droplet shape during the process. Further, it is often necessary to know if a process, e.g., droplet splitting on a given geometry, is possible at all, and what can be done to increase the system's reliability. It is thus important to use computer simulations to gain an understanding about the behavior of a droplet for a given electrode geometry and voltage curve. Special care must be exercised when considering surface-tension effects. We present computer simulations done with the Surface Evolver program and a template library combined with a graphical user interface (GUI) that facilitates standard tasks in the simulation of electrowetting arrays.

An automated near-field testbed for system- to chip-level EMC/EMI evaluations in the RF domain ca... more An automated near-field testbed for system- to chip-level EMC/EMI evaluations in the RF domain capable of precise EM phasor measurements is presented. The scanning system combines a large scanning volume with micrometre resolution. An optical surface reconstruction system allows measurement of the surface structure of the device under test (DUT) with better than 20μm uncertainty, allowing scans at a precisely known separation above arbitrary electronic components. Miniaturized active electro-optical time-domain ultra-wideband E- and H-field sensors for the frequency range from 0.01 to 6 GHz combined with a high speed vector signal analyser are applied to measure the EM phasor field distribution with a dynamic range of >120dB. The isolation of the probes eliminates perturbation of the EM field of the DUT compared to electrically connected probes and offers up to 60dB better sensitivity than passive electro-optical probes.

Abstract As the development of microelectronics is still driving towards further miniaturization,... more Abstract As the development of microelectronics is still driving towards further miniaturization, new materials, processes and technologies are crucial for the realization of future cost effective microsystems and components. Futures ICs and passives will also decrease in size, eg for RF-ID applications forecast die sizes are smaller than 250? m, thicknesses less than 50? m and pitches way below 100? m. Passives, if not directly integrated into the system carrier, will be even smaller. Touchless and self-assembly ...

In the process of physical modelling of microsystems operating on various energy domains, the eng... more In the process of physical modelling of microsystems operating on various energy domains, the engineer is used to apply Finite Element techniques for the discrete representation of the functionality of the device under investigation in a simulation environment. There are many commercial products that help the engineer in performing this task. The common feature of all these simulation tools is that the discrete representation consists of a system of ordinary differential equations. The dimension of this system is directly connected to the number of degrees of freedom for the respective problem. For a spatial displacement field, e.g., the degrees of freedom are three times the number of discretization nodes. The higher the requirements for precision of the simulation results, the more discretization nodes are usually introduced. Nevertheless, the results the engineer will use are in most cases of low dimensional order. In other words, the characteristic features of the required functionality of the device under developement are well represented in low dimensional subspace of the entire solution space of a very fine Finite Element model. Moreover, the requirement for system behaviour simulation makes it impossible to couple large-scale the dimension of the mathematical representation of subsystems. An approach to this task will be presented in this work, together with the modeling of an RF-microswitch as an example.

TechConnect Briefs, Feb 23, 2003

Proceedings of SPIE, Apr 19, 2002

ABSTRACT Self-alignment in the fluidic phase is an alternative technique to conventional pick-and... more ABSTRACT Self-alignment in the fluidic phase is an alternative technique to conventional pick-and-place assembly, providing cost-effective, precise assembly of millions of microparts. For accurate alignment, the control of unwanted surface defects lowering alignment precision. Local minima are investigated and the modulation of the energy curve is simulated. Furthermore, hytsteresis effects are studied. The simulation results allow predictions for the modeling of the fluidic surface tension driven self alignment and thus provide conditions for the robustness of the fabrication process.

TechConnect Briefs, Apr 22, 2002

Parallel self-assembly in the fluidic phase is a promising alternative technique to conventional ... more Parallel self-assembly in the fluidic phase is a promising alternative technique to conventional pick-and-place assembly. In this work the hydrophobic-hydrophilic material system between binding sites for microparts is simulated with respect to alignment precision. The results are compared with experimental findings and allow predictions for the optimization of the fluidic self assembly technique.

Linear Algebra and its Applications, Jun 1, 2006

The needs for model reduction in microsystem technology (MST) are described from an engineering p... more The needs for model reduction in microsystem technology (MST) are described from an engineering perspective. Two representative MST model reduction benchmarks are presented in order to facilitate further development in this area. The first benchmark application is from the area of electro-thermal simulation, the second one considers an electrostatically actuated beam as found in radio frequency applications. Model reduction is contrasted with compact modeling, which currently enjoys widespread use among engineers, and important challenges to be addressed are listed.

First-order moving least-squares are typically used in conjunction with smoothed particle hydrody... more First-order moving least-squares are typically used in conjunction with smoothed particle hydrodynamics in the form of post-processing filters for density fields, to smooth out noise that develops in most applications of smoothed particle hydrodynamics. We show how an approach based on higher-order moving least-squares can be used to correct some of the main limitations in gradient and second-order derivative computation in classic smoothed particle hydrodynamics formulations. With a small increase in computational cost, we manage to achieve smooth density distributions without the need for post-processing and with higher accuracy in the computation of the viscous term of the Navier-Stokes equations, thereby reducing the formation of spurious shockwaves or other streaming effects in the evolution of fluid flow. Numerical tests on a classic two-dimensional dam-break problem confirm the improvement of the new approach.

TechConnect Briefs, Mar 7, 2004

Modeling and simulation of the behavior of a system consisting of many single devices is an essen... more Modeling and simulation of the behavior of a system consisting of many single devices is an essential requirement for the reduction of design cycles in the development of microsystem applications. Analytic solutions for the describing partial differential equations of each component are only available for simple geometries. For complex geometries, either approximations or numerical methods can be used. However, the numerical treatment of the PDEs of thousands of interconnected single devices with each exhibiting a complex behavior is almost impossible without reduction of the order of unknowns to a lower-dimensional system. We present a fully automatic method to generate a compact model of second-order linear systems based on the Arnoldi process, and provide an example of successfull model order reduction to a gyroscope.

Springer eBooks, Oct 7, 2005

Summary. The simulation of heat transport for a single device is easily tackled by current comput... more Summary. The simulation of heat transport for a single device is easily tackled by current computational resources, even for a complex, finely structured geometry; however, the calculation of a multi-scale system consisting of a large number of those devices, eg, assembled printed circuit boards, is still a challenge. A further problem is the large change in heat conductivity of many semiconductor materials with temperature. We model the heat transfer along a 1D beam that has a nonlinear heat capacity which is represented by a ...

IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems, Feb 1, 2006

Tm-technisches Messen, Jun 1, 2001

The ambitious goal of magnetic field microsystems is to measure, in a space as small as possible,... more The ambitious goal of magnetic field microsystems is to measure, in a space as small as possible, the vector-valued magnetic induction accurately and reliably. The miniaturization aspect makes use of the use of silicon semiconductor technology a prerequisite since no other technology is currently capable of economically producing electrical devices with a smaller spatial resolution. When we add the requirements of specific application areas, the use of micromachining steps typical for micro-electromechanical systems (MEMS) provides further advantages to the designer. Magnetic field sensors based on the Hall effect make use of the Lorentz force F qv Â B that an external magnetic induction B induces on each charged carrier with velocity v moving within the device. The force acts in a direction perpendicular to the carrier velocity vector and the magnetic induction vector. Since electrons and holes move to opposite sides of the device they accumulate at the surfaces and build up a potential difference between those two surfaces, which is a measure for the magnetic field intensity (Fig. 1).

Sensors Update, Dec 1, 2003

The parallel fluidic self-assembly of microdevices is a new technology that promises to speed up ... more The parallel fluidic self-assembly of microdevices is a new technology that promises to speed up the production of complex microsystems made up of many separate parts. The technology brings many advantages. First, it enables a mix of chipmaking technologies for each of the component parts, with each technology selected for its particular technical or financial benefits. Second, it eliminates the need for pickand-place assembly that would unnecessarily slow down any manual assembly technique. Third, it enables massively parallel assembly, almost independent of the number of parts involved, and thereby mimics the elegant parallelism inherent in microchip circuit manufacture. In this chapter we explore this new technology with the ultimate goal of discovering the practical limits for its practical use in manufacturing real microsystems. The driving force of the assembly process is interface surface tension, and our approach is to find the simplest models that correctly describe the attachment, orientation, and bonding of parts to a suitably prepared substrate. We follow both an analytical and a numerical approach in describing the surface tension effects, the latter mainly to gain geometrical generality, and we couple modeling and simulation with suitable laboratory experiments. The ultimate goal of this work is to find practical design rules with which to select bond site geometries and the properties of participating liquids, and to find practical tolerances for all required geometrical and rheological parameters. This chapter extensively documents all results found to date, and carefully cites other work in this area.

Mathematical and Computer Modelling of Dynamical Systems, Aug 1, 2011

Model order reduction techniques are known to work reliably for finite-element-type simulations o... more Model order reduction techniques are known to work reliably for finite-element-type simulations of MEMS devices. These techniques can tremendously shorten computational times for transient and harmonic analysis. However, standard model reduction techniques cannot be applied if the equation system incorporates time-varying matrices or parameters that are to be preserved for the reduced model. However, design cycles often involve parameter modification, which should remain possible also in the reduced model. In this paper we demonstrate a novel parametrization method to numerically construct highly accurate parametric ODE systems based on a small number of systems with different parameter settings. This method is demonstrated to parameterize the geometry of a model of a micro-gyroscope, where the relative error introduced by the parametrization lies in the region of 10 −9. We also present novel semi-automatic order reduction methods that can preserve scalar parameters or functions during the reduction process. The first approach is based on a multivariate Padé-type expansion. The second approach is a coupling of the balanced truncation method for model order reduction of (deterministic) linear, time-invariant systems with interpolation. The approach is quite flexible in allowing the use of numerous interpolation techniques like polynomial, Hermite, rational, sinc, and spline interpolation. As technical examples we investigate a micro anemometer as well as the gyroscope. Speedup factors of 20 to 80 could be achieved, whilst retaining up to 6 parameters, and keeping typical relative errors below 1%.

CRC Press eBooks, Oct 8, 2018

Needs for model reduction in microsystem technology (MST) are described from an engineering persp... more Needs for model reduction in microsystem technology (MST) are described from an engineering perspective. The MST model reduction benchmarks are presented in order to facilitate further development in this area. The first benchmark application is electro-thermal simulation and the second one is an electrostatically actuated beam. Model reduction is contrasted with compact modeling, which currently enjoys widespread use among engineers, and important problems to be solved are listed.

We present an optimization strategy for the offset reduction of integrated magnetic field sensors... more We present an optimization strategy for the offset reduction of integrated magnetic field sensors with simultaneous maximization of sensitivity. We use the topology optimization method to automatically find a design with maximal sensitivity for given constraints on the offset by changing the conductivity of the Hall plate locally.

Self assembly in the fluidic phase is a technique excellently suited for the parallel assembly of... more Self assembly in the fluidic phase is a technique excellently suited for the parallel assembly of millions of microparts, as it is necessary for pixel displays. In this work, we investigate the effect of volume shrinking during the hardening of the glue and discuss the implications for the design of the assembled micro-parts. We simulate the response of the micro-part position to an inhomogeneous polymerization process and provide guidelines to the material choice for the glue.

International Journal of Modern Physics C, Nov 13, 2013

Fast and thorough mixing is a crucial operation of digital microfluidic devices, where discrete a... more Fast and thorough mixing is a crucial operation of digital microfluidic devices, where discrete and small fluid portions are moved and processed. In this paper, we want to analyze and to optimize the mixing process by substituting conventional motion and superposing oscillatory and translational modes. An accurate multiphase smoothed particle hydrodynamics (SPH) discretization for incompressible flow is instantiated. Different harmonic excitation patterns for the solid–liquid surface energy are applied and their influence on droplet mode shapes, formation of eddies and the Shannon entropy of droplet fluid components are measured. We tailor enhanced actuation patterns which improve mixing grade and reduce mixing time.