N. F. de Rooij

École Polytechnique Fédérale de Lausanne, Lausanne, Vaud, Switzerland

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Publications (1000)965.77 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Hybrid integration of different components (sampling/filtering, separation and detection) prevails in miniaturized analytical instruments for more selectivity and sensitivity. In this purpose, we report on flexible micro-hotplates usable for gas preconcentration and gas sensing. Our micro-hotplate is made on foil by using inkjet printing. Our technology provides flexibility in the design and paves the way for a new generation of cost-effective analytical instruments. Compared to previous work on Polyethylene Naphthalate (PEN) with silver as electrical conductor, it allows operating at high temperatures (up to 400˚C) thanks to the combination of gold nanoparticles-based heater and polyimide foil substrate. The foil gas preconcentrator is obtained by depositing an adsorbent onto of the foil hotplate whereas the fully printed metal oxide (MOX) sensor is implemented by inkjet-printing gold interdigitated electrodes covered by a metal oxide sensing layer. The Gas preconcentrator and the MOX sensor were successfully tested under benzene and carbon monoxide, respectively.
    ISOEN 2015, Dijon, France; 06/2016
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    ABSTRACT: We report on printed strain sensors on several meters long PET fibers for integration in textile at large scale. The sensors are made by locally inkjet printing capacitive transducers on cylindrical PET fibers used in industrial textiles. Sensor measurements were performed for strains up to 1%. 10 meters long functionalized PET fibers were woven with metallic interconnect fibers using large scale industrial weaving machine and resulted in a 1 m2 smart textile demonstrator. Applications are foreseen in predictive maintenance of industrial textiles and in the automotive industry.
    Procedia Engineering 12/2015; 120:279-282. DOI:10.1016/j.proeng.2015.08.613
  • M. Rieu · M. Camara · G. Tournier · J.P. Viricelle · C. Pijolat · N.F. de Rooij · D. Briand ·
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    ABSTRACT: We report on the development of a metal oxide (MOx) sensor prepared by inkjet printing technology onto polyimide foil. Gold electrodes and a gold heater were printed on each side of the substrate, respectively. SnO2 based ink was developed by sol-gel method and printed onto the electrodes. A final annealing at 400°C compatible with the polymeric transducers allows to synthetize the SnO2 film. Electrical measurements were carried out to characterize the response of fully printed sensor under different gases. The device was operated at a temperature between 200 and 300°C using the integrated heater. The sensor exhibited responses to carbon monoxide and nitrogen dioxide, under dry and wet air.
    Procedia Engineering 12/2015; 120:75-78. DOI:10.1016/j.proeng.2015.08.569
  • M. Camara · M. Rieu · P. Breuil · C. Pijolat · D. Briand · N.F. de Rooij ·
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    ABSTRACT: This paper presents the design and implementation of a foil gas preconcentrator (FGP) on polyimide (PI) substrate. One novelty of the paper is that our device is made on flexible foil by using printing whereas all preconcentrators seen in literature are mainly based on rigid substrates and are micro-machined using cleanroom processes. Printing allows the additive and localized deposition of materials at low temperature on large area and can be applied to both the patterning of the heating element and the integration of the gas absorbent material. The benefits are the easy and flexible processing of cost-effective and lightweight preconcentrators for a variety of target gases. The tubular shape of the FGP is obtained by rolling up and sealing the inkjet printed gold hotplate on foil, which is then filled with the gas absorbent material (Carbopack B and Tenax). The diameter of the inlet/outlet of FGP is adjustable leading to high flow rates, up to 1.5 L/min, much larger than their silicon counterpart. The concept was validated using two target gases (Benzene and Acetophenone) at concentrations down to 250 ppb.
    Procedia Engineering 12/2015; 120:265-268. DOI:10.1016/j.proeng.2015.08.602
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    ABSTRACT: This work presents a planar, longitudinal mode ultrasonic scalpel microfabricated from monocrystalline silicon wafers. Silicon was selected as the material for the ultrasonic horn due to its high speed of sound and thermal conductivity as well as its low density compared to commonly used titanium based alloys. Combined with a relatively high Young's modulus, a lighter, more efficient design for the ultrasonic scalpel can be implemented which, due to silicon batch manufacturing, can be fabricated at a lower cost. Transverse displacement of the piezoelectric actuators is coupled into the planar silicon structure and amplified by its horn-like geometry. Using finite element modeling and experimental displacement and velocity data as well as cutting tests, key design parameters have been identified that directly influence the power efficiency and robustness of the device as well as its ease of controllability when driven in resonance. Designs in which the full- and half-wave transverse modes of the transducer are matched or not matched to the natural frequencies of the piezoelectric actuators have been evaluated. The performance of the Si micromachined scalpels has been found to be comparable to existing commercial titanium based ultrasonic scalpels used in surgical operations for efficient dissection of tissue as well as coaptation and coagulation of tissue for hemostasis. Tip displacements (peak-to-peak) of the scalpels in the range of 10-50 μm with velocities ranging from 4 to 11 m/s have been achieved. The frequency of operation is in the range of 50-100 kHz depending on the transverse operating mode and the length of the scalpel. The cutting ability of the micromachined scalpels has been successfully demonstrated on chicken tissue.
    Biomedical Microdevices 08/2015; 17(4):9981. DOI:10.1007/s10544-015-9981-6 · 2.88 Impact Factor
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    ABSTRACT: This paper presents an analytical and experimental study of a compact configuration to harvest energy from a rotating gear using piezoelectric microelectromechanical system harvesters. The reported configuration realizes a contact-type frequency up-conversion mechanism in order to generate useful electrical energy. The up-conversion mechanism was achieved using an atomic force microscope (AFM)-like piezoelectric cantilever plucked by the teeth of the rotating gear that could be eventually driven by an oscillating mass. This paper describes relevant design guidelines for harvesting energy from the low-frequency mechanical movement of a rotating gear through analytical modeling and finite element method (FEM) simulation followed by experimental validation. Different harvester configurations are investigated to identify the optimal configuration in terms of the output energy and energy conversion efficiency. The latter results are reported for the first time because of the implementation of an original concept based on the coupling of the harvester with a rotational flywheel. The experimental results reveal that free vibrations of the harvester after plucking contribute significantly to the output energy and efficiency. By adding a proof mass, the efficiency of the system can be greatly improved. For plucking speeds between 3 and 19 r/s, average output powers in the order of tens of microwatts were obtained for continuous plucking. By combining interaction energy, friction, and energy absorption, between the harvester and inertial mass, the maximum efficiency of the impact piezoelectric harvesters was found to be 1.4%. The efficiency results obtained were compared with the noncontact magnetic plucking approach further demonstrating the potential of our concept. Finally, different tip-gear materials combinations were evaluated showing the importance of their nature on the reliability of the presented configuration. [2014-0102]
    Journal of Microelectromechanical Systems 06/2015; 24(3):742-754. DOI:10.1109/JMEMS.2014.2349794 · 1.75 Impact Factor
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    ABSTRACT: This paper presents the optimization of a micro gas preconcentrator (µ-GP) system applied to atmospheric pollution monitoring, with the help of a complete modeling of the preconcentration cycle. Two different approaches based on kinetic equations are used to illustrate the behavior of the micro gas preconcentrator for given experimental conditions. The need of a high adsorption flow and heating rate, a low desorption flow and detection volume is demonstrated through this paper. Preliminary to this optimization, the preconcentration factor is discussed and a definition is proposed.
    Analytical Chemistry 03/2015; 87(8). DOI:10.1021/acs.analchem.5b00400 · 5.64 Impact Factor
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    ABSTRACT: Point-of-care (PoC) applications require small, fast, and low power sensors with high reliability. Despite showing promising performances, nanomechanical sensors have not yet demonstrated the excellent reproducibility of measurements necessary to be incorporated in such systems. Coffee-ring effect usually occurs during the deposition of the functionalization layer and produces an inhomogeneous and poorly repeatable profile on the sensor surface. In this study, we investigated how cantilever-based sensors and the previously developed membrane-type surface stress sensor (MSS) are affected by an inhomogeneous functionalization. We functionalized 8 piezoresistive cantilevers and 16 MSS with a dextran solution that formed an inhomogeneous layer due to the coffee ring effect. During expositions to humidity pulses, MSS were five times more reproducible (standard deviations between 5% and 6%) compared to the cantilever-based sensors (standard deviations between 25% and 28%). In fact, the cantilever-based sensors were as reproducible as their functionalization layer while the reproducibility of MSS was only limited by the tolerances of their fabrication. This sensor-to-sensor reproducibility, combined with a high sensitivity, makes the MSS a promising bio/chemical sensor platform for reliable and label-free detection of substances to be integrated into PoC systems.
    Sensors and Actuators A Physical 03/2015; 228. DOI:10.1016/j.sna.2015.02.039 · 1.90 Impact Factor
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    ABSTRACT: In this paper we report on the fabrication of spin-coated biodegradable polylactic acid (PLA) thin films to be used as substrates for the realisation of all-solution-processed organic electronic devices. The full mechanical and electrical characterisation of these substrates shows that they exhibit good mechanical and dielectric properties and are therefore suitable for the fabrication of disposable electronics. To demonstrate practically the functionality of such PLA thin films, organic electronic devices were realised on the top of them, exclusively by means of solution-process fabrication techniques and in particular inkjet-printing. Also, a photonic curing procedure is here presented as a means for sintering the conductive inks without heating up the PLA substrates. Two types of organic transistors were fabricated on the top of PLA: organic field-effect transistors (OFETs), where the PLA film was used not only as a substrate but also as the gate dielectric, and all-inkjet-printed organic electrochemical transistors (OECTs). The second typology of transistors exhibited one of the highest transconductance reported so far in the literature (up to 2.75 mS). This study opens an avenue for the fabrication of disposable, low-cost organic electronic devices.
    Organic Electronics 02/2015; 17:77-86. DOI:10.1016/j.orgel.2014.11.010 · 3.83 Impact Factor
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    Sara Talaei · Peter D. van der Wal · Sher Ahmed · Martha Liley · Nico F. de Rooij ·
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    ABSTRACT: Monitoring metabolism fluctuations inside a cell culture is a valuable method for assessment of the cells vitality. Enzyme-based biosensors can provide selective measurement of metabolites such as glucose, lactate, glutamate and choline. However, integration of these biosensors inside a cell culture is a challenging issue that can disrupt the properties of the cells microenvironment or influence the biosensors’ enzyme functioning. Herein, a technique for measuring the abovementioned metabolites in a cell culture without affecting the enzymes or the cells is presented. In this study, SU-8 is investigated as a suitable substrate for a simple enzyme immobilization. Two SU-8 microreactors are designed inside a microfluidic cartridge and functionalized with different enzymes. The implemented microreactors are used for detection of two metabolites simultaneously in a few microliters of a sample extracted from the cell-culture medium. Sub-micromolar concentrations are detectable using this device. The results of measuring variations in glucose and lactate concentration inside a cell culture, before and after exposing the cells to three different toxicants, are presented. In order to eliminate the enzymes disruption by the toxicants present inside the medium, a protocol for a toxicant-free sampling is investigated.
    Microfluidics and Nanofluidics 02/2015; 19(2). DOI:10.1007/s10404-015-1562-8 · 2.53 Impact Factor
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    Francisco Molina-Lopez · Danick Briand · Nico F. de Rooij ·
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    ABSTRACT: The work presented demonstrates the utilization of micro-contact printing of self-assembled monolayers (SAMs) of gold nanoparticles (NPs) to pattern the porous thin metallic film composing the top electrode of an ultra-fast capacitive relative humidity sensor based on miniaturized parallel-plates electrodes. The rest of the device, which occupies an area of only 0.0314 mm2, is fabricated by inkjet printing stacked individual drops of functional materials, namely gold NPs for the bottom electrode and a polymeric humidity sensing layer, on a polymeric foil. Compared to other printing methods, the use of microcontact printing to pattern the top electrode enables the additive transfer of a solvent-free metallic layer that does not interact chemically with the sensing layer, permitting the thinning of the latter without risk of short-circuits between electrodes, and broadening the range of usable sensing materials for detection of other gases. Thinning the sensing layer yields to ultra-fast response devices with high values of capacitance and sensitivity per surface area. The fabrication process is compatible with low heat-resistant polymeric substrates and scalable to large-area and large-scale fabrication, foreseeing the development of low-cost vapor sensing sheets with high space–time resolution, where every sensor would correspond to a pixel of a large array.
    Organic Electronics 01/2015; 16. DOI:10.1016/j.orgel.2014.10.041 · 3.83 Impact Factor
  • Andrés Vasquez Quintero · Danick Briand · Nico F de Rooij ·
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    ABSTRACT: In this paper, a low temperature flip-chip integration technique for Si bare dies is demonstrated on flexible PET substrates with screen-printed circuits. The proposed technique is based on patterned blind vias in dry film photoresist (DP) filled with isotropic conductive adhesive (ICA). The DP material serves to define the vias, to confine the ICA paste (80 mu m-wide and potentially 25 mu m-wide vias), as an adhesion layer to improve the mechanical robustness of the assembly, and to protect additional circuitry on the substrate. The technique is demonstrated using gold-bumped daisy chain chips (DCCs), with electrical vias resistances in the order to hundreds of milliohms, and peel/shear adhesion strengths of 0.7 N mm(-1) and 3.2 MPa, respectively, (i.e. at 1.2 MPa of bonding pressure). Finally, the mechanical robustness to bending forces was optimized through flexural mechanics models by placing the neutral plane at the DCC/DP adhesive interface. The optimization was performed by reducing the Si thickness from 400 to 37 mu m, and resulted in highly robust integrated assemblies withstanding 10 000 cycles of dynamic bending at 40 mm of radius, with relative changes in vias resistance lower than 20%. In addition, the electrical vias resistance and adhesion strengths were compared to samples integrated with anisotropic conductive adhesives (ACAs). Besides the low temperature and high integration resolution, the proposed method is compatible with large area fabrication and multilayer architectures on foil.
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    ABSTRACT: The brain is probably the least understood organ of our body, in both normal and pathological conditions. In consequence its study requires the development of novel neurotechnologies. Here we report on the development and experimental validation of novel on-chip neurotechnologies for investigating the properties of neural networks and brain tissues in-vitro.
    6th European Conference of the International Federation for Medical and Biological Engineering; 01/2015
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    ABSTRACT: This work presents an approach for increasing operational bandwidth of a vibration energy harvester in low-frequency environments by effectively exploiting contact-based frequency up-conversion. It was implemented by a couple of low-frequency resonators with appropriately spaced natural frequencies impacting high-frequency piezoelectric generators when the device is harmonically excited in 10-40 Hz range. A proof of concept was designed, modeled, fabricated and characterized, demonstrating improved power and bandwidth performance (up to 37 μW and 9 Hz at 1 g) with respect to traditional single-resonator designs.
    Procedia Engineering 12/2014; 87:1517-1520. DOI:10.1016/j.proeng.2014.11.587
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    ABSTRACT: A cleanroom-free fabrication process adapted to microfluidic devices is presented for pyrotechnical microelectromechanical systems balloon actuators. The actuators are intended for on-chip pumping and fluid ejection to replace tabletop pumping solutions in low-cost portable single-use microfluidic devices. The fabrication process leveraged polymeric foils (polyethylene terephthalate, SU-8, polydimethylsiloxane) for the structure, directly bonded using surface treatments, heat and pressure, and inkjet printing and electroplating for the igniter. This paper also presents a semianalytical model that successfully predicted the inflation height of the balloon for a given device geometry and propellant loading.
    Journal of Microelectromechanical Systems 12/2014; 23(6):1417-1427. DOI:10.1109/JMEMS.2014.2314702 · 1.75 Impact Factor
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    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; 86(18). DOI:10.1021/ac501908c · 5.64 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 08/2014; 215:184–188. DOI:10.1016/j.sna.2013.08.043 · 1.90 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 07/2014; 105(4):043502-043502-4. DOI:10.1063/1.4891248 · 3.30 Impact Factor
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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; 14(12). DOI:10.1109/JSEN.2014.2335417 · 1.76 Impact Factor

Publication Stats

11k Citations
965.77 Total Impact Points


  • 2-2015
    • École Polytechnique Fédérale de Lausanne
      • • Sensors, Actuators and Microsystems Laboratory
      • • Institute of Microengineering
      Lausanne, Vaud, Switzerland
  • 2011-2013
    • Centre Suisse d'Electronique et de Microtechnique
      • Centre Suisse d’Electronique et de Microtechnique SA (CSEM)
      Neuenburg, Neuchâtel, Switzerland
    • University of Western Macedonia
      • Department of Engineering Informatics and Telecommunications
      Kozani, West Macedonia, Greece
  • 2012
    • Universität Luzern
      Luzern, Lucerne, Switzerland
  • 1988-2009
    • Université de Neuchâtel
      • Laboratoire Temps-Fréquence (LTF)
      Neuenburg, Neuchâtel, Switzerland
  • 2003
    • Lem Sa Switzerland
      Freiburg, Fribourg, Switzerland
  • 1999
    • Universität Basel
      Bâle, Basel-City, Switzerland
  • 1998
    • Sumitomo Heavy Industries, Ltd
      Edo, Tōkyō, Japan
  • 1996-1998
    • Eawag: Das Wasserforschungs-Institut des ETH-Bereichs
      Duebendorf, Zurich, Switzerland
  • 1991
    • Tohoku University
      Sendai-shi, Miyagi, Japan
  • 1989
    • University of Geneva
      • Faculty of Medicine
      Genève, Geneva, Switzerland
  • 1987
    • Massachusetts Institute of Technology
      Cambridge, Massachusetts, United States
  • 1977-1980
    • Universiteit Twente
      • Department of Electrical Engineering
      Enschede, Overijssel, Netherlands