Novel positive-tone thick photoresist for high aspect ratio microsystem technology

 A methacrylate copolymer combining chemically amplified concept and casting technique was developed as a novel thick photoresist for the UV-LIGA process. Photoresist layers up to 500 μm in thickness can be fabricated easily. Microstructures fabricated by the novel thick photoresist were demonstrated. At present, the ring-shape microstructures with 150 μm tall and 15 μm wide have been realized and the calculated aspect ratio is 10. Received: 10 August 2001/Accepted: 24 September 2001     

A linear microactuator with enhanced design

 Based on a previously developed three phase variable reluctance (VR) linear microactuator design features, improving the dynamic properties, were investigated. The active part exhibits, as in the case of its predecessor, permalloy yokes and stator poles with teeth, and is fabricated using thin film technology. Improvements regarding the dynamic motor range were made by varying the number of phases. The new design has substantially improved the dynamic properties, due to the fact that the six phase design greatly reduced the location dependent driving force ripple. Received: 21 May 2001 / Accepted: 30 July 2001     

Microfabrication of freedom and articulated alumina-based components

 In order to obtain three dimensional micro-objects, we developed a new microstereolithography apparatus based on the use of a dynamic mask generator which allows the manufacture of a complete layer by only one irradiation, the part being still layered. In order to improve the mechanical properties of the fabricated micro-objects and the resolution of the process, a mixture of alumina and photopolymer is used. By controlling the fabrication parameters, we present a movable microgimbal which has been realised in only one fabrication step. Received: 5 October 2001/Accepted: 26 November 2001     

A push–pull multi-layered piggyback PZT actuator

 To increase the recording density of hard disk drives (HDDs), we developed a push–pull multi-layered piggyback PZT actuator that enables fine positioning by a dual-stage servo system. This PZT actuator consists of 31-mode push–pull multi-layered PZT strips and a head suspension. It generates a 1.4-μm effective radial head displacement at 5 V. This displacement is twice that of conventional piggyback actuators. The main resonance frequency of the actuator is higher than 9 kHz, its lifetime is longer than five years, and it has a self-latch property. These features mean that the developed actuator can meet all the requirements for implementation in HDD servo systems, including a track density of 100 kTPI (kilo-tracks per inch). The actuator was implemented in two types of HDDs (A-type and B-type), which reduced the repeatable and non-repeatable positioning errors (by 40 to 45% and 28 to 34%, respectively). Received: 25 July 2001/Accepted: 11 December 2001     

High performance flat miniature heat pipes fabricated by UD-LIGA process

 The objective of this work is to process a high performance flat miniature heat pipes (FMHP). The FMHP is fabricated by ultra-deep LIGA (UD-LIGA) process developed by SRRC. Moreover, the performance of the FMHP is theoretically estimated. The dimensions of microgrooves on the FMHP are 1 mm in depth, 100 μm in width, and 60 mm in length. The theoretically predicted results show that the dissipated heat flux can reach to 391 W at a working temperature of 100 °C. Received: 10 August 2001/Accepted: 24 September 2001 This paper was presented at the Fourth International Workshop on High Aspect Ratio Microstructure Technology HARMST 2001 in June 2001.     

A 199-line Matlab code for Pareto-optimal tracing in topology optimization

The paper ‘A 99-line topology optimization code written in Matlab’ by Sigmund (Struct Multidisc Optim 21(2):120–127, 2001) demonstrated that SIMP-based topology optimization can be easily implemented in less than hundred lines of Matlab code. The published method and code has been used even since by numerous researchers to advance the field of topology optimization. Inspired by the above paper, we demonstrate here that, by exploiting the notion of topological-sensitivity (an alternate to SIMP), one can generate Pareto-optimal topologies in about twice the number of lines of Matlab code. In other words, optimal topologies for various volume fractions can be generated in a highly efficient manner, by directly tracing the Pareto-optimal curve.     

High quality laser beam soldering

 In the work presented the potential of a pyrometric process control during laser beam soldering will be enhanced. Primarily we have developed a processing head with an integrated up-to-date pyrometric sensor conditioned for the temperature range of soft soldering. Using high speed photography we have analysed the detected secondary emissions during laser beam soldering and correlated the acquired pyrometric signals of process emissions with processes sequencing. Finally we named different strategies and control methods to achieve reliable high quality solder joints implementing a pyrometric process control. Received: 21 May 2001 / Accepted: 5 July 2001     

Continuous fatigue level estimation for the classification of fatigued bills based on an acoustic signal feature by a supervised SOM

Fatigued bills have a harmful influence on the daily operation of automated teller machines (ATMs). To make the classification of fatigued bills more efficient, the development of an automatic fatigued bill classification method with a continu ous fatigue level is desirable. We propose a new method to estimate the bending rigidity of bills using the acoustic signal feature of banking machines. The estimated bending rigidities are used as the continuous fatigue level for the classification of fatigued bills. By using a supervised self-organizing map (SOM), we effectively estimate the bending rigidity using only the acoustic energy pattern. The experimental results with real bill samples show the effectiveness of the proposed method. This work was presented in part at the 13th International Symposium on Artificial Life and Robotics, Oita, Japan, January 31–February 2, 2008     

A novel contact slider/gimbal to raise recording density in flexible disk drives

 We developed the soft and full-contact head/gimbal assembly (HGA) for card-size flexible disk drive. We used a 150 μg slider and a flexible beam of BeCu alloy to realize soft contact. We designed our HGA using FEM simulation and optimized the load force, the load pressure, and the stress on the beam. We report the mechanical characteristics, read-write signals, and the vibration of the HGA. A new type loading/unloading mechanism was developed for the removable flexible medium, and confirmed the reliability of the loading/unloading mechanism by the deformation of the HGA and the loaded medium. Received: 5 July 2001/Accepted: 1 November 2001     

Design of experiments and evaluation of BDD ordering heuristics

Traditional approaches to the measurement of performance for CAD algorithms involve the use of sets of so-called “benchmark circuits.” In this paper, we demonstrate that current procedures do not produce results which accurately characterize the behavior of the algorithms under study. Indeed, we show that the apparent advances in algorithms which are documented by traditional benchmarking may well be due to chance, and not due to any new properties of the algorithms. As an alternative, we introduce a new methodology for the characterization of CAD heuristics which employs well-studied design of experiments methods. We show through numerous examples how such methods can be applied to evaluate the behavior of heuristics used in BDD variable ordering. Published online: 15 May 2001     

Blood flow through compliant vessels after endovascular repair: wall deformations induced by the discontinuous wall properties

In this paper we derive a set of equations which can be used to study wall deformations and transmural pressure at the anchoring sites of endovascular prostheses. The equations are the jump conditions associated with the underlying model equations. The model equations are derived from the Navier–Stokes equations to describe the blood flow through compliant axi-symmetric vessels after endovascular repair. They are in the form of a quasilinear hyperbolic system of partial differential equations with discontinuous coefficients. Since the weak form of the equations contains the product of the Dirac delta distribution with the Heaviside function, the jump conditions and the weak form cannot be obtained using the standard distribution theory. Driven by the undelying application in mind, we present a preliminary analysis leading to the jump conditions by interpreting the ambiguous products as a mean value with respect to the measure obtained in the limit of the “regularizing kernels” [17]. We show that the numerical solution obtained by using the Richtmyer two-step Lax–Wendroff method satisfies the weak form of the equations associated with a symmetric regularizing kernel in which case the weak form is independent of the particular choice of the kernel. We give an example (treatement of aortic abdominal aneurysm using multiple overlapping stents) where the conditions obtained in this paper can be used in the optimal design of an endovascular procedure. Received: 31 January 2001 / Accepted: 30 September 2001     

Wear resistant tools for reproduction technologies produced by micro powder metallurgy

 Micro system technology (MST) needs cost effective production techniques and for the development of new MST products also new materials are necessary. Reproduction technologies have been developed for large scale production which are allow processing a broad scope of materials (plastic, ceramic and metal). For these, tools are needed which have to fulfil a lot of requirements. In this paper the results of an evaluation of micro powder metallurgy (MPM) as a technology to produce highly productive tools and moulds for structuring of plastics and metals by reproduction, possibly also for difficult materials as glass, are presented. Moulds made of iron, stainless steel and hard metal of different designs were produced and quality issues investigated. Results of hot embossing and injection moulding of metal and plastic using these inserts produced by micro powder metallurgy are given. Received: 15 May 2001 / Accepted: 4 July 2001     

Cyanate ester based resin systems for snap-cure applications

 Resin compositions comprising cyanate ester have been demonstrated to be useful as die attach adhesives, underfills and encapsulants, where the characteristics of the resins can be varied in a wide range by copolymerization with functionalized comonomers such as epoxies, phenols, rubbers, thermoplastics and others. To reach a combination of properties such as long pot life, short cure time and high glass transition temperature, we encapsulated small particles of effective hardeners to make them insoluble and non-reactive when mixed with the resin at room temperature. Pot lifes of more than 3 months could be reached, whereas the same cyanate ester gels and becomes solid within 30 min at room temperature, if the neat hardener is used instead of the capsules. At a certain elevated temperature, which mainly depends on the structure of the hardener, the capsules open and the curing reaction starts immediately. Low-temperature systems with cure times less than 5 min at 80 °C reach glass temperatures of about 140 °C, and a glass transition temperature of 220 °C after 10 s cure can be achieved with another combination. The developed snap cure resin systems can be easily mixed with a lot of common additives such as minerals, tougheners, metallic powders and others to cover a wide range of performance characteristics for use as adhesives, underfills, encapsulants and the like. Received: 15 May 2001/Accepted: 15 October 2001     

Microfabrication of single-use plastic microfluidic devices for high-throughput screening and DNA analysis

 Modern drug discovery and genomic analysis depend on rapid analysis of large numbers of samples in parallel. The applicability of microfluidic devices in this field needs low cost devices, which can be fabricated in mass production. In close collaboration, Greiner Bio-One and Forschungszentrum Karlsruhe have developed a single-use plastic microfluidic capillary electrophoresis (CE) array in the standardized microplate footprint. Feasibility studies have shown that hot embossing with a mechanical micromachined molding tool is the appropriate technology for low cost mass fabrication. A subsequent sealing of the microchannels allows sub-microliter sample volumes in 96-channel multiplexed microstructures. Received: 16 May 2001 / Accepted: 3 July 2001     

Exponential Stability of Nonlinear Time-Varying Differential Equations and Partial Averaging

In this paper we formulate, within the Liapunov framework, a sufficient condition for exponential stability of a differential equation. This condition gives rise to a new averaging result referred to as “partial averaging”: exponential stability of a system , with α sufficiently large, is implied by exponential stability of a time-varying system . Date received: March 28, 2000. Date revised: March 7, 2001.     

A video system to demonstrate interactions of near-infrared radiation with plant leaves

A video system has been developed that displays results of interactions of near-infrared radiation in the 0.78 to 1.1 μm waveband with plant leaves. The system has a video camera, video monitor, cassette player, and cassette recorder. Three examples from the literature that have been shown to affect light reflectance were demonstrated successfully with the video system: leaf water infiltration, leaf maturation, and leaf stacking. The video system has potential use to facilitate teaching, research, and applied remote sensing.     

A MS-Windows simulation tool for synchrotron X-ray exposure and subsequent development

 A prerequisite for the commercialization of the LIGA process (from the German Lithographie=Lithography, Galvanoformung=electroforming and Abformung=moulding) for the fabrication of microstructures is the availability of a simulation tool which allows the simulation of the complete lithographic process, including synchrotron source, exposure parameters and subsequent development method. The program must be highly flexible and allow for the simulation of different sources, chosen beam-line components, exposure parameters and development method independently. A simulation tool, meeting the discussed requirements, is being developed at IMT/FZK in close collaboration with LURE. For user-friendliness, a GUI (Graphical User Interface) working in a MS-Windows environment has been built, which consists of main and sub work sheets (Fig. 1). In each sub work sheet, one “set of parameters” can be defined, e.g. the development method. In this paper, we will provide a general overview of the possibilities the program offers to the user. Received: 10 August 2001/Accepted: 24 September 2001 This work is financed by the European Training and Mobility of Researchers (TMR) research network “Microfabrication with Synchrotron Radiation, deep X-ray for industrial use” (MICROSYNC) under the contract No ERBFMRXCT97-0140. This paper was presented at the Fourth International Workshop on nk;High Aspect Ratio Microstructure Technology HARMST 2001 in June 2001.     

A new approach for the assembly of lenses in front of flexible miniature fibre-scopes

 The article will give some new impulses and first results on the way to a new assembly process of a miniature flexible fibre-scope. New techniques enable the automatic placement of an aspherical lens in front of a fibre-scope depending on the desired working distance. Received: 17 May 2001 / Accepted: 6 June 2001     

Combining Different Methods and Numbers of Weak Decision Trees

Several ways of manipulating a training set have shown that weakened classifier combination can improve prediction accuracy. In the present paper, we focus on learning set sampling (Breiman’s Bagging) and random feature subset selections (Ho’s Random Subspaces). We present a combination scheme labelled ‘Bagfs’, in which new learning sets are generated on the basis of both bootstrap replicates and random subspaces. The performances of the three methods (Bagging, Random Subspaces and Bagfs) are compared to the standard Adaboost algorithm. All four methods are assessed by means of a decision-tree inducer (C4.5). In addition, we also study whether the number and the way in which they are created has a significant influence on the performance of their combination. To answer these two questions, we undertook the application of the McNemar test of significance and the Kappa degree-of-agreement. The results, obtained on 23 conventional databases, show that on average, Bagfs exhibits the best agreement between prediction and supervision. Received: 17 November 2000, Received in revised form: 30 October 2001, Accepted: 13 December 2001     

Long throw linear magnetic actuators stackable to one millimeter of structural height

 Magnetic micro-actuators fabricated using LIGA-like processing and an aligned stacking technique have obtained structural heights of greater than one millimeter with structure aspect ratios greater than 100 to 1. Actuator displacements approaching 500 μm have been obtained under DC drive conditions with minimal input power. The actuator produces large output force and large sensitivity of inductance with respect to displacement. Inductance changes of ∼50 μH/μm are ideal for position sensing and closed loop actuator control. Received: 25 August 1997/Accepted: 22 October 1997