J.J. van Baar

Universiteit Twente, Enschede, Overijssel, Netherlands

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Publications (22)12.88 Total impact

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    ABSTRACT: Arrays of MEMS fabricated flow sensors inspired by the acoustic flow-sensitive hairs found on the cerci of crickets have been designed, fabricated and characterized. The hairs consist of up to 1 mm long SU-8 structures mounted on suspended membranes with normal translational and rotational degrees of freedom. Electrodes on the membrane and on the substrate form variable capacitors, allowing for capacitive read-out. Capacitance versus voltage, frequency dependence and directional sensitivity measurements have been successfully carried out on fabricated sensor arrays, showing the viability of the concept. The sensors form a model system allowing for investigations on sensory acoustics by their arrayed nature, their adaptivity via electrostatic interaction (frequency tuning and parametric amplification) and their susceptibility to noise (stochastic resonance).
    Nanotechnology 02/2006; 17(4):S84-9. DOI:10.1088/0957-4484/17/4/013 · 3.67 Impact Factor
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    ABSTRACT: This paper presents bistable microswitches with Au contacts with the aim to combine them with artificial hairs for flow sensing. The Au contacts are applied on both ends of a silicon nitride beam, suspended by a torsional bar at its center. The beam is provided with electrodes for electrostatic actuation, which were used for characterization and can also be used for adaptive control of the mechanical properties of the flow sensor. The electrodes have been actuated in anti-phase to drive the microswitch similarly to an astable multivibrator. Single-sided switching has been measured up to 10 kHz actuation frequency.
    Micro Electro Mechanical Systems, 2006. MEMS 2006 Istanbul. 19th IEEE International Conference on; 02/2006
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    ABSTRACT: This paper presents the modelling, design, fabrication and characterization of flow sensors based on the wind-receptor hairs of crickets. Cricket sensory hairs are highly sensitive to drag-forces exerted on the hair shaft. Artificial sensory hairs have been realized in SU-8 on suspended Si x N y membranes. The movement of the membranes is detected capacitively. Capacitance versus voltage, frequency dependence and directional sensitivity measurements have been successfully carried out on fabricated sensor arrays, showing the viability of the concept.
    Journal of Micromechanics and Microengineering 07/2005; 15:132-138. DOI:10.1088/0960-1317/15/7/019 · 1.73 Impact Factor
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    ABSTRACT: This paper presents the fabrication of flow-sensors based on the drag-force induced motion of artificial hairs connected to capacitive read-out. Artificial hairs were made either out of moulded silicon-nitride structures or by SU-8. The SU-8 hairs were suspended on membranes containing electrodes to form the variable capacitors. Silicon-rich-nitride hairs were made using a silicon wafer as a dissolvable mould. The longest SU-8 hairs were fabricated using a 470 μm thick photoresist layer. Capacitance versus voltage, frequency dependency and directional sensitivity measurements have been carried out on entire arrays and are reported in this paper.
    Micro Electro Mechanical Systems, 2005. MEMS 2005. 18th IEEE International Conference on; 03/2005
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    ABSTRACT: A micro-calorimeter array consisting of superconducting transition-edge sensors is under development for the X-ray imaging spectrometer on board of ESA's XEUS (X-ray Evolving Universe Spectroscopy) mission. An array of 32 × 32 pixels with a pixel size of 250 micron square is envisaged. So far, 5 × 5 pixels arrays were successfully fabricated along two fabrication routes: a bulk micromachining and a surface micromachining route. Both routes result in working arrays with energy resolutions down to 5 eV FWHM for the best pixels.
    Micro Electro Mechanical Systems, 2005. MEMS 2005. 18th IEEE International Conference on; 01/2005
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    ABSTRACT: This paper describes the current status of the development of cryogenic X-ray sensors for space based astronomy applications by SRON in collaboration with the MESA + Research Institute. Focus is given to the design and fabrication aspects of the project. Key part for the design, based on Finite Element Simulation, is the knowledge of material parameters at deep cryogenic temperatures. Measurements of these are presented. Besides the sensor array, integrated read-out structures are required. Development of these is shortly addressed.
    SAFE & ProRISC 2004; 11/2004
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    ABSTRACT: A micro-calorimeter array with superconducting transition-edge sensors read out by a SQUID-based frequency-domain multiplexer is under development for the X-ray imaging spectrometer on board ESA's X-ray Evolving Universe Spectroscopy (XEUS) mission. The XEUS requirements are 2 and 5 eV FWHM energy resolution for 2 and 7 keV X-rays, respectively. An array of 32 x 32 pixels with 250 micron square pixels is envisaged. SRON and MESA + have developed 5 x 5 imaging micro-calorimeter prototype arrays along a bulk micromachining and a surface micromachining route. The present state of array design and development with emphasis on pixel-to-pixel performance measurements of thermal and I-V characteristics, sensor noise and energy resolution are presented. SRON and VTT are developing frequency-domain multiplexing with SQUID current amplifiers to read out the 32 x 32 array. The concept for the frequency division multiplexing read-out will be presented and its performance characteristics discussed. Recent results of sensor operation under AC-bias (500 kHz) are presented.
    Proceedings of SPIE - The International Society for Optical Engineering 09/2004; DOI:10.1117/12.552933 · 0.20 Impact Factor
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    ABSTRACT: We report on the development activities towards a cryogenic array of micro-calorimeters, based on voltage-biased Ti/Au transition edge thermometers. Fabrication issues are discussed along the lines of two fabrication routes. One route utilizes bulk micromachining in [110] Si wafers, the other route surface micromachining with a sacrificial layer. Prototype 5×5 arrays have been fabricated and we present the first performance data: Two arrays were irradiated with 5.9keV X-ray irradiation and an energy resolution of 6-7eV FWHM was obtained. The arrays have been designed and their performance is analyzed with the aid of finite element simulation of the electrothermal behavior of a single pixel and thermal conductivity in the supporting structure.
    Nuclear Instruments and Methods 03/2004; A(520):443-445. DOI:10.1016/j.nima.2003.11.359
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    ABSTRACT: This paper presents the fabrication of artificial hairs of siliconnitride and SU-8 on suspended membranes for flow sensing applications. The suspended membranes contain electrodes for capacitive sensing of the rotation of the hairs. For the siliconnitride hairs a silicon wafer is used as mould and for SU-8 hairs a thick layer was spun. Capacity-voltage measurements have been carried out.
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    ABSTRACT: We present monolithically integrated high-density arrays of artificial hairs for flow pattern measurements based on drag force. A combined bulk/surface micromachining process has been developed to integrate the artificial hairs with capacitive read-out. First fabrication results show the possibility to fabricate out-of-plane hairs without reverting to micro-assembly technologies. This enables realisation of high-density arrays of symmetrical sensors with two-dimensional sensitivity.
    Sensors, 2003. Proceedings of IEEE; 11/2003
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    ABSTRACT: Surface micromachined distributed Pirani pressure gauges, with designed heater-to-heat sink distances (gap-heights) of 0.35 μrn and 1.10 μm, are successfully fabricated, modeled and characterized. Measurements and model response correspond within 5 % of the measured value in a pressure range of 10 to 2*10<sup>4</sup> Pa. The distributed nature of the sensor facilitates pressure measurement to be independent of the Temperature Coefficient of Resistance of the resistors. This also provides an inherent compensation for heat loss via the membrane supporting the heater, extending the lower pressure range.
    Sensors, 2003. Proceedings of IEEE; 11/2003
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    ABSTRACT: A resistive sensor array is presented for two dimensional temperature distribution measurements in a micromachined flow channel. This allows simultaneous measurement of flow velocity and fluid parameters, like thermal conductivity, diffusion coefficient and viscosity. More general advantages of measuring temperature distributions are the inherent compensation of heat losses to the support and the insensitivity to variations in the temperature coefficient of resistance.
    TRANSDUCERS, Solid-State Sensors, Actuators and Microsystems, 12th International Conference on, 2003; 07/2003
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    ABSTRACT: A differential pressure sensor has been realized with thermal readout. The thermal readout allows simultaneous measurement of the membrane deflection due to a pressure difference and measurement of the absolute pressure by operating the structure as a Pirani pressure sensor
    Micro Electro Mechanical Systems, 2002. The Fifteenth IEEE International Conference on; 02/2002
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    ABSTRACT: A differential pressure sensor has been realized with thermal readout. The thermal readout allows simultaneous measurement of the membrane deflection due to a pressure difference and measurement of the absolute pressure by operating the structure as a Pirani pressure sensor. The measuring of the temperature distribution makes it possible to take the heat transfer to the support in to account and make the measurements independent of the temperature coefficient of resistance of the sensing elements.
    Sensors, 2002. Proceedings of IEEE; 02/2002
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    ABSTRACT: In this paper thermal sensor-actuator structures are proposed that can be used to measure various fluid parameters such as thermal conductivity, flow velocity, heat capacity, kinematic viscosity and pressure. All structures are designed in such a way that they can be realized in the same fabrication process and therefore they can be easily combined in a single device. All structures are based on the principle of thermal measurements: resistive structures are used for both heating and temperature measurements. For accurate measurements the temperature coefficient of resistance (TCR) must be well known. Therefore, a special structure, which can be used for auto-calibration, was designed to measure the TCR. A first device containing structures for the combined measurement of flow velocity, thermal conductivity and TCR has been fabricated. Measurements show promising results.
    Journal of Micromechanics and Microengineering 07/2001; 11(4):311. DOI:10.1088/0960-1317/11/4/304 · 1.73 Impact Factor
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    ABSTRACT: In this abstract we present a novel "spirit level"-sensor derived from a well-known thermal flow-sensor. The operation principle is based on the temperature difference of two identical heaters, caused by buoyancy of air. Heating as well as temperature sensing of the structures is carried out using temperature dependent platinum resistors. Due to its simplicity the sensor is easily fabricated in silicon micro-machining technology. Theory describing the sensor is presented. First experiments, using DC signals only, show an adequate sensitivity though high accuracy operation is hampered by thermal drift.
    Journal of Micromechanics and Microengineering 01/1999; DOI:10.1088/0960-1317/10/2/324 · 1.73 Impact Factor
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    ABSTRACT: This paper presents design issues and a theoretical model of electrostatically driven axial-gap polysilicon wobble motors. The motor design benefits from large axial rotor-to-stator overlap and large gear ratios, and motor designs with rotor radii of 50 and 100 μm are capable of generating torques in the nanoNewtonmeter range at high electrostatic fields. Because of the large gear ratio, smaller angular steps and lower rotational speed are obtained, compared to radial-gap motor designs. Aspects like gear ratio, torque generation, excitation schemes and torque coverage, normal forces, friction, rotor kinetics, and dynamical behavior are addressed. The motor design is compliant to the integration of gear linkages with respect to mechanical power transmission
    Journal of Microelectromechanical Systems 04/1998; DOI:10.1109/84.661387 · 1.92 Impact Factor
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    ABSTRACT: For pt. I see ibid., vol. 7, no. 1, p. 79-86 (1998). This paper presents the fabrication and first performance characteristics of electrostatically driven axial-gap polysilicon wobble motors. The fabrication is based on a four mask process using polysilicon surface-micromachining techniques. Three twelve-stator-pole wobble motor designs have been realized with rotor radii of 50 and 100 μm. Motors have been operated successfully at driving voltages as low as 6 V at speeds up to 150 rpm. The motor performance is characterized by gear ratio measurements and measuring starting and stopping voltages. Motor lifetimes of several million wobble cycles, comparable to operating times of several hours, have been obtained
    Journal of Microelectromechanical Systems 04/1998; DOI:10.1109/84.661388 · 1.92 Impact Factor
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    ABSTRACT: Not Available
    Solid-State Sensors and Actuators, 1995 and Eurosensors IX.. Transducers '95. The 8th International Conference on; 07/1995
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    ABSTRACT: This paper presents the design and realization of flow sensors based on wind-receptor hairs of crickets. Natural cricket hairs are weakly suspended at their base, resulting in high sensitivity for drag-forces exerted on the hair shaft. The realized structures consist of an SU-8 hair on a membrane with electrodes for capacitive read-out. The structure is suspended by weak silicon-nitride springs, which results in high sensitivity. Initial capacitance versus voltage measurements are in agreement with theory, and show that measuring drag-forces on the artificial hairs is feasible.