Publications by Nico de Rooij | EPFL Graph Search

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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 pres ...

The goal is to develop a miniaturized system allowing continuous measurement of glucose concentration profiles over 24 hours for several days. The unique feature of the PharmaSens / IMT approach lies in the insertion mechanism and the needle size to assure optimum user-friendliness and patient comfort. The measurement method is based on classical amperometric detection using an enzymatic membrane. The sensor substrate is made on a flexprint substrate and consists of a 3-electrode cell on a needle-shaped tip

A germanium strip waveguide on a silicon substrate is integrated with a microfluidic chip to detect cocaine in tetrachloroethylene solutions. In the evanescent field of the waveguide, cocaine absorbs the light at 5.8μm, which is emitted from a quantum cascade laser. The lowest measured concentration is 100μg/ml.

Shaping light with microtechnology components has been possible for many years. The Texas Instruments digital micromirror device (DMD) and all types of adaptive optics systems are very sophisticated tools, well established and widely used. Here we present, however, two very dedicated systems, where one is an extremely simple MEMS-based tunable diffuser, while the second device is complex micromirror array with new capabilities for femtosecond laser pulse shaping. Showing the two systems right next to each o

This paper presents a low-complexity and low temperature (85°C) fabrication process for vibration energy harvesters. The process employs lamination steps to transfer thinned PZT thick sheets onto flexible polymeric substrates, using dry film photoresist. The influence of geometrical parameters on the device performance were assessed by FEM simulations (using COMSOL) and supported by experiments. Optimization of the output power was performed by modifying the neutral plane within the device and by using a lo

Future space exploration will emphasize on cost effectiveness and highly focused mission objectives. Missions costs are directly proportional to its total weight, thus, the trend will be to replace bulky and heavy components of space carriers, communicatio ...

We present results on various post processing techniques to create complex 3-dimensional nanostructures with enhanced capabilities. The starting point for all architectures is a self aligned nanopillar with surrounding circular rim in PMMA. This particular shape is obtained by the energy density distribution of incident and backscattered electrons of e-beam exposure and reflects the dual behavior of PMMA as positive and negative resist. Employing only 1 lithographic step and several batch processing techniq

We are developing single-crystalline silicon micromirror arrays (MMA) fro future generation infrared multiobject spectroscopy (IR MOS). The micromirrors are 100 mu m x 200 mu m in size and can be tilted by electrostatic actuation yielding a tilt-angle of 20 degrees. Arrays of 5x5 micromirrors were gold-coated and tested at below 100K. The coated and uncoated micromirrors are optically flat (peak-to-valley deformation < lambda/20 for lambda > 1 mu m) at room temperature and in cryogenic environment. Successf

A new kind of MEMS reflective display is being developed having high contrast and reflectivity, better than on printed paper. The system is based on novel vertical flaps, which can be electrostatically turned by 90° to horizontal position. After fabrication, the poly-silicon flaps are vertical to the wafer surface and on the top suspended by torsion beams. In this state the pixel is black, incoming ambient light passes by the flaps and is absorbed by an underlying absorptive layer. When the flaps are turned

Bulk PZT ceramics provide high electromechanical coupling (k) which is desirable for piezoelectric energy harvesters since the energy transformed from a mechanical agitation into an electrical output is proportional to k2 [1-2]. However, piezoelectric cantilever-based energy harvesters using bulk PZT require a bonding layer to couple the thick PZT sheet to the elastic layer substrate, typically silicon. We present the characteristics and performance of vibration energy harvesters comparing three different b

A micro-pump for medical applications is being developed using organometallic derived PZT thin films and silicon micromachining technology. Critical issues include the deposition of 'thick' PZT films (1 to 2 mu m thickness), film processing compatibility with available Si/SixNy/Ta/Pt structures and the establishing of piezoelectric poling parameters. A processing technique for the preparation of thick PZT films is presented. Piezoelectric properties are characterized by both direct method using alternating

This paper presents the optimization of a micro gas preconcentrator based on a micro-channel in porous and non-porous silicon filled with an adequate adsorbent. This micro gas preconcentrator is both applicable in the fields of atmospheric pollution monito ...

We report on recent advances in micro fabrication technology using micromolding and high aspect ratio structuring of photopolymer. The direct application is the realization of components for millimeter-size, ultrasonic piezoelectric motors. A new fabrication process using a thick epoxy-based material (SU-8) and the electroplating of nickel is demonstrated. Photopolymer structures have also been realized and released using a positive tone resist as sacrificial layer. The main advantages over past fabrication

A novel one-step microfabrication process of SU-8 films for the development of inexpensive light-weight and small size optical glucose micro-biosensors is proposed. Experimental work was carried out in order to investigate whether SU-8 photoresists, which are polymers widely used in MEMS applications, can be utilised as immobilisation matrices for the simultaneous encapsulation of glucose oxidase and an oxygen-sensitive fluorescent indicator. The immobilisation of the enzyme, the encapsulation of the indica

We report on recent advances in micro fabrication technology using micromoulding and high-aspect ratio structuring of photopolymer. The direct application is the realization of components for millimeter-size, ultrasonic piezoelectric motors. A new fabrication process using a thick epoxy-based material (SU-8) and the electroplating of nickel is demonstrated. Photopolymer structures have also been realized and released using a positive tone resist as sacrificial layer. The main advantages over past fabricatio

In this paper, the development of a low temperature bonding process focused on indium-based technology for microfabricated alkali cells is presented. The intended application is the use of these cells in chip scale atomic clocks. The existing technology is mainly based on anodic bonding. For some applications, such as where wall coating is used instead of buffer gas, anodic bonding cannot be applied because of the relatively high temperature of the process.

We present a thermally activated solvent bonding technique for the formation of embedded microstructures in polymer. It is based, on the temperature dependent solubility of polymer in a liquid that is not a solvent at room temperature. With thermal activation, the liquid is transformed into a solvent of the polymer, creating a bonding capability through segmental or chain interdiffusion at the bonding interface. The technique has advantages over the more commonly used thermal bonding due to its much lower o

This work presents three applications of dry photoresist film for printed and flexible electronics devices. First, as part of the flexible encapsulation of printed gas sensors (i.e. humidity). This process was performed at relatively low temperatures (85 °C) and was shown to be mechanically robust. Second, as mechanical protection layer of printed circuitry to increase the robustness to bending forces and protect against environmental-induced wear. Mechanical robustness was increased by optimizing the neutr

We report on the application of a silicon micromachined lamellar grating interferometer in a Fourier Transform Infrared (FTIR) spectrometer for the detection of gases in the mid-infrared (MIR) region. The FTIR spectrometer was equipped with MIR optical fib ...

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 in

Nico de Rooij

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On the experimental determination of the efficiency of piezoelectric impact-type energy harvesters using a rotational flywheel

Flexprint substrate enzyme sensor for determination of daily glucose-profiles for diabetic patients

Mid infrared waveguide spectroscopy for cocaine detection in liquid environments

Shaping Light with MOEMS

Vibration energy harvester on plastic foil based on transferring PZT thick sheets

MEMS for space

Pattern transfer and post processing of complex nanostructures formed by e-beam exposure in PMMA

Micromirror array for multiobject spectroscopy in ground-based and space telescopes

Vertical electrostatically 90° turning flaps for reflective MEMS display

Assembling of Thick PZT Sheet on Silicon for Energy Harvesting Applications

PZT films for micro-pumps

A micro gas preconcentrator with improved performance for pollution monitoring and explosives detection

Fabrication process of high aspect ratio elastic and SU-8 structures for piezoelectric motor applications

Proof of Concept of a Novel Optical Glucose Enzyme-Based Micro-Biosensor using SU-8

Two steps micromoulding and photopolymer high-aspect ratio structuring for applications in piezoelectric motor components

Low Temperature Indium-based Sealing of Microfabricated Alkali Cells for Chip Scale Atomic Clocks

Thermally activated solvent bonding of polymers

Applications of dry photoresist film for printed and flexible electronics

Gas Detection with a Micro FTIR Spectrometer in the MIR Region

Gas Preconcentrator Made by Rolling up a Printed Hotplate on Foil