N. F. de Rooij

École Polytechnique Fédérale de Lausanne, Lausanne, Vaud, Switzerland

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Publications (966)716.12 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Conducting polyaniline-based chemiresistors on printed polymeric micro-hotplates were developed, showing sensitive and selective detection of ammonia vapor in air. The devices consist of a fully inkjet-printed silver heater and interdigitated electrodes on a polyethylene naphthalate substrate, separated by a thin dielectric film. The integrated heater allowed operation at elevated temperatures, enhancing the ammonia sensing performance. The printed sensor designs were optimized over two different generations, to improve the thermal performance through careful design of the shape and dimension of the heater element. A vapor-phase deposition polymerization technique was adapted to produce polyaniline sensing layers doped with poly(4-styrenesulfonic acid). The resulting sensor had better thermal stability and sensing performance when compared with conventional polyaniline-based sensors, and this was attributed to the polymeric dopant used in this study. Improved long-term stability of the sensors was achieved by electrodeposition of gold on the silver electrodes. Response to sub-ppm concentrations of ammonia even under humid conditions was observed.
    Analytical chemistry. 08/2014;
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    ABSTRACT: Taking advantage of the sensor interface capabilities of a Radiofrequency Identification (RFID) chip, the integration of different types of sensors on printed Ultra High Frequency (UHF) RFID tags is investigated. The design, development and testing of printed smart sensing tags compatible with the RFID standard Electronic Product Code (EPC) Gen 2 is presented. Two different strategies are employed to interface the sensors: passive single-chip and semi-passive architectures. Both strategies provide sensor data by directly answering to the RFID reader inquiries or by using a data logging mechanism to store the sensor data in the RFID chip memory. Temperature read out is measured using the embedded sensor in the RFID chip. Additionally a light sensor and a pressure sensor interfaced to a microcontroller are implemented in the passive and semi-passive tags versions, respectively. For the employed RFID chip, two different UHF antennas are designed and printed using inkjet and screen printing to compare their radiofrequency performances. Finally, the fabricated smart tags are fully validated through measurements in an anechoic chamber and their behaviors are compared to numerical simulation. The screen printed semi-passive RFID tag with loop antenna shows a better reading range than the inkjet-printed one, whereas the passive tag can be considered as the most cost-effective system.
    IEEE Sensors Journal 07/2014; · 1.48 Impact Factor
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    ABSTRACT: Forward osmosis (FO) is a well-established process that has been used for different applications like desalination of water, concentration of foods or drugs, and energy harvesting. We exploited this process in a fully automatic system to adjust osmolality of environmental water samples that are to be tested by cell-based biosensors. In cell-based biosensors, samples are brought into contact with living cells. Therefore, the samples0 osmolality and pH should be in a range that is tolerable for the cells. Controlling these parameters has been a significant challenge especially in environmental monitoring, where the biosensors are required to work on-site. In this paper, we introduce a low-cost portable fluidic system that works automatically, and adjusts the osmolality and pH of environmental samples without diluting or denaturizing the ingredients of the samples. We report the performance of this system in adjusting the osmolality and pH of Swiss environmental waters with a natural osmolality of 471 mmol/kg and a pH of 7.8470.02.
    Journal of Membrane Science 03/2014; 454:470–477. · 4.09 Impact Factor
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    ABSTRACT: The design optimization through modeling of a thinned bulk-PZT-based vibration energy harvester on a flexible polymeric substrate is presented. We also propose a simple foil-level fabrication process for their realization, by thinning the PZT down to 50 μm and laminating it via dry film photoresist onto a PET substrate at low temperature (<85 °C). Two models, based on analytical and finite element modeling (FEM) methods, were developed and experimentally validated. The first, referred to as the hybrid model, is based mainly on analytical equations with the introduction of a correction factor derived from FEM simulations. The second, referred to as the numerical model, is fully based on COMSOL simulations. Both models have exhibited a very good agreement with the measured output power and resonance frequency. After their validation, a geometrical optimization through a parametric study was performed for the length, width, and thicknesses of the different layers comprising the device. As a result, an output power of 6.7 μW at 49.8 Hz and 0.1 g, a normalized power density (NPD) of 11 683 μW g−2 cm−3, and a figure of merit (FOM) of 227 μW g−2 cm−3 were obtained for the optimized harvester.
    Smart Materials and Structures 03/2014; 23(4):045041. · 2.02 Impact Factor
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    ABSTRACT: We report the modeling, and geometrical and electrical characterization, of inkjet and screen-printed patterns on different polymeric substrates for use as antennas in radio-frequency identification (RFID) applications. We compared the physical and electrical characteristics of two silver nanoparticle-based commercial inkjet-printable inks and one screen-printable silver paste, when deposited on polyimide (PI), polyethylene terephthalate (PET), and polyetherimide (PEI) substrates. First, the thickness of the inkjet-printed patterns was predicted by use of an analytical model based on printing conditions and ink composition. The predicted thickness was confirmed experimentally, and geometrical characterization of the lines was completed by measuring the root-mean-square roughness of the patterns. Second, direct-current electrical characterization was performed to identify the printing conditions yielding the lowest resistivity and sheet resistance. The minimum resistivity for the inkjet-printing method was 8.6 ± 0.8 μΩ cm, obtained by printing four stacked layers of one of the commercial inks on PEI, whereas minimum resistivity of 44 ± 7 μΩ cm and 39 ± 4 μΩ cm were obtained for a single layer of screen-printed ink on polyimide (PI) with 140 threads/cm mesh and 90 threads/cm mesh, respectively. In every case, these minimum values of resistivity were obtained for the largest tested thickness. Coplanar waveguide transmission lines were then designed and characterized to analyze the radio-frequency (RF) performance of the printed patterns; minimum transmission losses of 0.0022 ± 0.0012 dB/mm and 0.0016 ± 0.0012 dB/mm measured at 13.56 MHz, in the high-frequency (HF) band, were achieved by inkjet printing on PEI and screen printing on PI, respectively. At 868 MHz, in the ultra-high-frequency band, the minimum values of transmission loss were 0.0130 ± 0.0014 dB/mm for inkjet printing on PEI and 0.0100 ± 0.0014 dB/mm for screen printing on PI. Although the resistivity achieved is lower for inkjet printing than for screen printing, RF losses for inkjetted patterns were larger than for screen-printed patterns, because thicker layers were obtained by screen printing. Finally, several coil inductors for the HF band were also fabricated by use of both printing techniques, and were used as antennas for semi-passive smart RFID tags on plastic foil capable of measuring temperature and humidity.
    Journal of Electronic Materials 02/2014; 43(2). · 1.64 Impact Factor
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    ABSTRACT: We present a portable microsystem to quantitatively detect cocaine in human saliva. In this system, we combine a microfluidic-based multiphase liquid–liquid extraction method to transfer cocaine continuously from IR-light-absorbing saliva to an IR-transparent solvent (tetrachloroethylene) with waveguide IR spectroscopy (QC-laser, waveguide, detector) to detect the cocaine on-chip. For the fabrication of the low-cost polymer microfluidic chips a simple rapid prototyping technique based on Scotch-tape masters was further developed and applied. To perform the droplet-based liquid–liquid extraction, we designed and integrated a simple and robust droplet generation method based on the capillary focusing effect within the device. Compared to well-characterized and commonly used microfluidic H-filters, our system showed at least two times higher extraction efficiencies with potential for further improvements. The current liquid–liquid extraction method alone can efficiently extract cocaine and pre-concentrate the analytes in a new solvent. Our fully integrated optofluidic system successfully detected cocaine in real saliva samples spiked with the drug (500 μg/mL) and allowed real time measurements, which makes this approach suitable for point-of-care applications.
    Analytical Chemistry 01/2014; · 5.70 Impact Factor
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    ABSTRACT: We present a complete wafer level microfabrication process for the production of unimorph MEMS energy harvesters based on thinned bulk piezoelectric ceramic, lead zirconate titanate (PZT), sheets. This process eliminates the need for individual bonding of PZT pieces and proof masses at the chip level while still benefitting from the excellent properties of bulk PZT. With the process presented in this paper, 20 piezoelectric energy harvesters have been fabricated in parallel at the wafer level by bonding a single bulk (PZT) sheet onto a silicon-on-insulator (SOI) wafer using a low-temperature process and structuring the bonded stack with standard microfabrication techniques including thinning of the bulk PZT sheet using mechanical grinding as well as electrodeposition to deposit a thick nickel proof mass on the tip of each cantilever. A single fabricated harvester with an effective volume of 47.82 mm3 is capable of generating a normalized power density of 3346 μW cm−3 g−2 with an average power of 1.6 μW under an excitation of 0.1 g (1 g = 9.81 m s−2) at a resonant frequency of 100 Hz through an optimal resistive load of 11.8 kΩ. Thinned bulk PZT exhibits high power and a useable voltage while maintaining a low optimal resistive load, demonstrating the potential of high performance piezoelectric MEMS energy harvesters using bulk PZT sheets fabricated at the wafer level.
    Sensors and Actuators A Physical 01/2014; · 1.84 Impact Factor
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    ABSTRACT: We have experimentally studied the variation in electrical resistance of flexible platinum lines patterned on polyimide foil when they are subjected to circular bending constraints. The lines were patterned by means of standard photolithography and sputtering deposition. Two different photolithography masks were used for comparative evaluation: an un-expensive transparency mask and a standard chromium mask. Measurements of the temperature coefficient of resistance (TCR) and time stability of the resistance have been acquired for lines bent down to 1.25 mm radius of curvature on a customized bending setup, showing good reliability results. The robustness of the lines has been also assessed by registering their change in resistance while bending at different radii of curvature. The lines showed reliability issues for radii of curvature below 1.25 mm, presenting a resistance variation of 19% for transparency mask-fabricated lines and 9% for chromium mask-fabricated lines. The worse reliability performances of transparency mask lines, compared to the chromium mask ones, was found to be due to their imperfect edges, which promoted the formation and propagation of cracks during bending. The results of the experiments in this work permitted to compare the performances of flexible conductive lines with different geometry and fabricated with two different masks, establishing quantitative and qualitative bending limits for their appropriate operation in flexible electronics systems.
    Microelectronics Reliability 01/2014; · 1.14 Impact Factor
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    ABSTRACT: A new and versatile fabrication process of insulated gold tip probes for atomic force microscopy (AFM) is presented by Wu et al. (In-plane fabricated insulated gold-tip probe for electrochemical and molecular experiments, in: 2013 IEEE 26th International Conference on Micro Electro Mechanical Systems (MEMS), IEEE, 2013, pp. 492–495). The novelty of the process lies in the fact that the length and the thickness of the cantilever are defined by photolithography and Si etching from the wafer top surface. Width of the cantilever is defined by the device layer of a silicon-on-insulator (SOI) wafer. The tip is fabricated in the wafer top plane. E-beam lithography was employed outlining the gold nanowire tip. The chip body is formed with the handling layer of the SOI by deep reactive ion etching in later steps. In a practical operation, the probe chip is rotated by 90 degree. The tip radius of curvature is approximately 20 nm. The high-quality insulation on the probe was demonstrated by performing electrodeposition of gold on the tip-end. The spring constant of the cantilever was obtained by measuring resonance frequency of the cantilever. With this in-plane fabrication process, probes with different spring constants ranging from 0.05 N/m to 13.67 N/m were fabricated on the same wafer.
    Sensors and Actuators A Physical 01/2014; 215:184–188. · 1.84 Impact Factor
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    ABSTRACT: We present a microfabricated alkali vapor cell equipped with an anti-relaxation wall coating. The anti-relaxation coating used is octadecyltrichlorosilane and the cell was sealed by thin-film indium-bonding at a low temperature of 140 °C. The cell body is made of silicon and Pyrex and features a double-chamber design. Depolarizing properties due to liquid Rb droplets are avoided by confining the Rb droplets to one chamber only. Optical and microwave spectroscopy performed on this wall-coated cell are used to evaluate the cell's relaxation properties and a potential gas contamination. Double-resonance signals obtained from the cell show an intrinsic linewidth that is significantly lower than the linewidth that would be expected in case the cell had no wall coating but only contained a buffer-gas contamination on the level measured by optical spectroscopy. Combined with further experimental evidence this proves the presence of a working anti-relaxation wall coating in the cell. Such cells are of interest for applications in miniature atomic clocks, magnetometers, and other quantum sensors.
    Applied Physics Letters 01/2014; 105(4):043502-043502-4. · 3.79 Impact Factor
  • N. Besse, A. P. Pisano, N. F. de Rooij
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    ABSTRACT: Thin circular piezoelectric energy harvester diaphragms undergoing large deflection in a harsh liquid environment are investigated in this paper. A material set combining AlN as transducer, SiC as electronics, Mo as wiring and Si as holder is considered. A highly accurate analytical model, which presents less than 5% error compared to FEM simulations in COMSOL, is first developed to study thoroughly flat diaphragms. Consequently, etching the wafer and adding a corrugation are proposed to reduce both the stress concentration at the edge and the influence of residual stress on the device behavior, respectively. Both ideas are predicted to increase the power density compared to the standard flat case by at least a factor of 5 to 10.
    Journal of Physics Conference Series 12/2013; 476(1):2056-.
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    ABSTRACT: This paper presents experimentally-verified multiphysics finite element model of a wideband vibration energy harvester with impact coupling, which operates on the principle of frequency up-conversion: under low-frequency harmonic base excitation a cantilever-type resonator (with resonant frequency of 18.8 Hz) impacts a high-frequency piezoelectric cantilever, which starts freely vibrate at its resonant frequency of 374 Hz. Such input frequency amplification enables efficient power generation under low-frequency ambient excitations. The model was implemented in COMSOL and the contact between the cantilevers was formulated by using a nonlinear viscoelastic model. Reported results of dynamical and electrical testing of the fabricated vibration energy harvester confirm the accuracy of the model as well as reveal some operational characteristics of the device under varying impact and excitation conditions.
    Journal of Physics Conference Series 12/2013; 476(1):2090-.
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    ABSTRACT: This paper presents the fabrication and characterization of multilayer PVDF resonant micro-vibrational energy harvesters designed to withstand environments in which high levels of acceleration are present. The multilayer cantilevers are fabricated by combining two folded PVDF stacks into a multilayered, bimorph structure. This acts to increase the overall capacitance of the harvester, a problem that plaques PVDF cantilevers as a result of its low dielectric constant. Moderate powers (7 μW) are produced from the cantilevers even at high acceleration levels (20 g) due to the limited piezoelectric coefficient of PVDF; however, as a result of the high tensile strength and low elastic modulus of PVDF, the cantilevers are able to survive extremely high accelerations (> 4000 g) without breakage - a critical problem for harvesters based on brittle piezoelectric materials and substrates.
    Journal of Physics Conference Series 12/2013; 476(1):2113-.
  • F. Molina-Lopez, D. Briand, N.F. de Rooij
    Sensors and Actuators B Chemical 12/2013; 189:89-96. · 3.84 Impact Factor
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    ABSTRACT: This paper demonstrates a novel methodology using a rotational flywheel to determine the energy conversion efficiency of the impact based piezoelectric energy harvesters. The influence of the impact speed and additional proof mass on the efficiency is presented here. In order to convert low frequency mechanical oscillations into usable electrical energy, a piezoelectric harvester is coupled to a rotating gear wheel driven by flywheel. The efficiency is determined from the ratio of the electrical energy generated by the harvester to the mechanical energy dissipated by the flywheel. The experimental results reveal that free vibrations of the harvester after plucking contribute significantly to the efficiency. The efficiency and output energy can be greatly improved by adding a proof mass to the harvester. Under certain conditions, the piezoelectric harvesters have an impact energy conversion efficiency of 1.2%.
    Journal of Physics Conference Series 12/2013; 476(1):2137-.
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    ABSTRACT: In this paper we present two compact, quantum cascade laser absorption spectroscopy based, sensors developed for trace substance detection in gases and liquids. The gas sensor, in its most integrated version, represents the first system combining a quantum cascade laser and a quantum cascade detector. Furthermore, it uses a toroidal mirror cell with a volume of only 40 cm(3) for a path length of up to 4 m. The analytical performance is assessed by the measurements of isotope ratios of CO2 at ambient abundance. For the (13)CO2/(12)CO2 isotope ratio, a measurement precision of 0.2‰ is demonstrated after an integration time of 600 s. For the liquid sensor, a microfluidic system is used to extract cocaine from saliva into a solvent (PCE) transparent in the mid-infrared. This system is bonded on top of a Si/Ge waveguide and the concentration of cocaine in PCE is measured through the interaction of the evanescent part of the waveguide optical mode and the solvent flowing on top. A detection limit of <100 μg mL(-1) was achieved with this system and down to 10 μg mL(-1) with a simplified, but improved system.
    The Analyst 10/2013; · 4.23 Impact Factor
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    ABSTRACT: Abstract A miniature device enabling parallel in vivo detection of the neurotransmitter choline in multiple brain regions of freely behaving rodents is presented. This is achieved by combining a biosensor microprobe array with a custom-developed CMOS chip. Each silicon microprobe comprises multiple platinum electrodes that are coated with an enzymatic membrane and a permselective layer for selective detection of choline. The biosensors, based on the principle of amperometric detection, exhibit a sensitivity of 157±35 µA mM-1 cm-2, a limit of detection of below 1 µM, and a response time in the range of 1 s. With on-chip digitalization and multiplexing, parallel recordings can be performed at a high signal-to-noise ratio with minimal space requirements and with substantial reduction of external signal interference. The layout of the integrated circuitry allows for versatile configuration of the current range and can, therefore, also be used for functionalization of the electrodes before use. The result is a compact, highly integrated system, very convenient for on-site measurements.
    Biomedizinische Technik/Biomedical Engineering 10/2013; · 1.16 Impact Factor
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    ABSTRACT: A micromirror array composed of 2048 silicon micromirrors measuring 200 × 100 μm<sup>2</sup> and tilting by 25° was developed as a reconfigurable slit mask for multi-object spectroscopy (MOS) in astronomy. The fill factor, contrast, and mirror deformation at both room and cryogenic temperatures were investigated. Contrast was measured using an optical setup that mimics a MOS instrument, and mirror deformation was characterized using a Twyman-Green interferometer. The results indicate that the array exhibited a fill factor of 82%, a contrast ratio of 1000:1, and surface mirror deformations of 8 nm and 27 nm for mirrors tilted at 298 K and 162 K, respectively.
    Optics Express 09/2013; 21(19):22400-22409. · 3.55 Impact Factor
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    ABSTRACT: We present a compact frequency-stabilized laser system locked to the Rubidium absorption line of a micro-fabricated reference cell. A printed circuit board (PCB) is used to carry all the components and part of the electronics, and low-temperature co-fired ceramic (LTCC) modules are used to temperature-stabilize the laser diode and the miniature Rubidium cell (cell inner dimensions: 5 mm diameter and 2 mm height). The measured frequency stability of the laser, in terms of Allan deviation, is ≤8×10−10 for integration times of 103–105s. The current overall dimensions of the system are 70×40×50 mm3, with good potential for realization of a frequency-stabilized laser module with few cm3 volume.
    Optics and Lasers in Engineering 08/2013; 51(8):1023–1027. · 1.92 Impact Factor
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    ABSTRACT: This paper reports on low-temperature and hermetic thin-film indium bonding for wafer-level encapsulation and packaging of delicate and temperature sensitive devices. This indium-bonding technology enables bonding of surface materials commonly used in MEMS technology. The temperature is kept below 140 °C for all process steps and no surface treatment is applied before and during bonding. This bonding technology allows hermetic sealing at 140 °C with a leak rate below 4 × 10−12 mbar l s−1 at room temperature. The tensile strength of the bonds up to 25 MPa goes along with a very high yield.
    Journal of Micromechanics and Microengineering 06/2013; 23(7):075007. · 1.79 Impact Factor

Publication Stats

5k Citations
716.12 Total Impact Points

Institutions

  • 2–2014
    • École Polytechnique Fédérale de Lausanne
      • • Sensors, Actuators and Microsystems Laboratory
      • • Laboratoire des microsystèmes pour les technologies spatiales
      • • Institut de microtechnique
      • • Ceramics Laboratory
      Lausanne, Vaud, Switzerland
  • 1991–2013
    • Centre Suisse d'Electronique et de Microtechnique
      • Centre Suisse d’Electronique et de Microtechnique SA (CSEM)
      Neuenburg, Neuchâtel, Switzerland
  • 2012
    • Universität Luzern
      Luzern, Lucerne, Switzerland
    • Zurich University of Applied Sciences
      • Institute of Computational Physics (ICP)
      Winterthur, Zurich, Switzerland
  • 1988–2010
    • Université de Neuchâtel
      • Laboratoire Temps-Fréquence (LTF)
      Neuenburg, Neuchâtel, Switzerland
  • 2009
    • Delft University Of Technology
      • Section of Electronic Instrumentation
      Delft, South Holland, Netherlands
  • 2007–2009
    • École Nationale Supérieure des Mines de Saint-Étienne
      Saint-Étienne, Rhône-Alpes, France
    • University of Tuebingen
      • Institute of Physical and Theoretical Chemistry
      Tübingen, Baden-Wuerttemberg, Germany
  • 2008
    • Università degli studi di Cagliari
      • Department of Electrical and Electronic Engineering
      Cagliari, Sardinia, Italy
  • 2006
    • Johannes Kepler University Linz
      • Institut für Mikroelektronik und Mikrosensorik
      Linz, Upper Austria, Austria
    • The University of Tokyo
      Edo, Tōkyō, Japan
    • Hochschule Reutlingen
      Reutlingen, Baden-Württemberg, Germany
  • 2005
    • Intel
      Santa Clara, California, United States
  • 2003
    • IBM
      Armonk, New York, United States
    • Tohoku University
      Japan
  • 2000
    • Tel Aviv University
      Tell Afif, Tel Aviv, Israel
  • 1998–2000
    • Sumitomo Heavy Industries, Ltd
      Edo, Tōkyō, Japan
  • 1999
    • Universität Basel
      Bâle, Basel-City, Switzerland
  • 1996–1998
    • Eawag: Das Wasserforschungs-Institut des ETH-Bereichs
      Duebendorf, Zurich, Switzerland
  • 1979–1994
    • Universiteit Twente
      • Department of Electrical Engineering
      Enschede, Overijssel, Netherlands
  • 1989
    • University of Geneva
      • Faculty of Medicine
      Genève, GE, Switzerland