Publications by Thomas Maeder | EPFL Graph Search

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The processing and application of graphite powder-based sacrificial layer for fabrication of microfluidic structures in LTCC is described. Such layers are produced as pastes, which are screen-printed in LTCC sheets to avoid sagging, by supporting closed, t ...

Pb(Zr1–xTix)O3 thin films (x = 0.55 and 0.85) were prepared on fine grained, polished ZrO2 ceramic substrates by a sol-gel method. The high thermal expansion of ZrO2 relative to Si allows the preparation of thicker PZT films with reduced thermal stress. For the x = 0.85 films, this reduction of thermal stress gives a preference of (001) over (100) oriented domains. For x = 0.55 films, square P–E hysteresis loops were obtained with: Pr = 36 µC/Cm2, and Ec = 45 kV/cm, at a field of 160 kV/cm. Pyroelectric fig

Thick-film resistors (TFRs) consist of a percolating network of conducting oxide nanoparticlesdispersed in an insulating glassy matrix, whose resistive properties are dominated by quantumtunneling across insulating layers separating adjacent conducting grains. Tunneling processes are at the origin of the high sensitivity of the TFRs resistances to applied strains. We have measuredtransport and piezoresistive response for different RuO2-based TFRs as a function of metallic concentration x and RuO 2 grain siz

This poster is an overview of work carried out on the design of the ITER high-frequency magnetic diagnostic coil (HF sensor). In the first part, the ITER requirements for the HF sensor are presented. In the second part, the ITER reference design of the HF sensor has been assessed and showed some potential weaknesses, which led us to the conclusion that alternative designs could usefully be examined. Several options have been explored, and are presented in the third part: (3.1) direct laser cutting a metalli

This document gives an approximate calculation of the frequency bandwidth of the MilliNewton – and serves as a starting point for calculations on other cantilever-type sensors. The mechanical resonance frequencies of MilliNewton are high, due to the very small cantilever size. The working frequency is in fact limited by the electrical circuit at ca. 1 kHz (MilliNewton-A) or ca. 200 Hz (MilliNewton-B).

Estimation of the stress distribution in the solder or glue joint between a cantilever and its base, and of the corresponding bending stress distribution in the cantilever. This reports details results of modelling of the stresses in the solder or glue joints linking a cantilever to its base, using analytical and finite difference methods. The additional compliance due to joint deformation and its effect on the resonance frequency is also calculated. The parameters used in the examples are those of the Mill

Increasing situational awareness at human-machine interface level is a key success factor for high efficiency therapies and surgical procedures. On a technical level, cost-effective, reliable sensor integration becomes the most critical element where multi-disciplinary approaches are needed in the fields of sensor design, sensory intelligence, energy management, packaging and materials. We present two examples of mechanical human-machine-interfaces (HMIs) in completely different use cases in the medical fie

We investigate in this work the formulation of composite resistive pastes based on epoxy resins and graphite for micro-heater manufacturing via thick-film technology. The resistive paste is first screen-printed onto a printed circuit board (PCB) substrate, and then coated with expandable polydimethylsiloxane (PDMS), a composite based on an elastomeric matrix and expandable microspheres, resulting into one-shot thermal actuators allowing pumping and sealing in microfluidic devices. The resistive paste must t

Force and pressure sensors based on the piezoresistive properties of thickfilm resistors are widely used due to their reliability, simplicity and lowcost. Recently, the introduction of low-temperature co-fired ceramic(LTCC) substrates has allowed further increases in miniaturisation and integration, while new high-strength ceramic substrates such as zirconia- toughened alumina (ZTA) has enabled better sensor response.However, the materials' properties are still insufficiently characterised for sensor applic

Résumé. Ce document décrit la cinétique de réponse électrique des capteurs de force MilliNewton-B et CentoNewton (toutes versions) utilisant l'électronique "moderne" à un seul amplificateur opérationnel, comparée au capteur MilliNewton-A utilisant un circuit différentiel basé sur un amplificateur double. La réponse électrique est testée en introduisant une perturbation à 1 kHz sur les entrées des amplificateurs, et les résultats sont comparés à des simulations et des calculs simplifiés. La valeur optimale d

Série de capteurs de force MilliNewton, version Bb (embases 08-400...08-546 ; poutres 08-550...08-574) : avec bumps larges pour montage fiable de la poudre ; qualification RoHS de matériaux pour la poutre. Ce document rend compte des résultats sur la version Bb du capteur de force MilliNewton, dont la principale innovation est l'introduction de grands plots de brasure embase-poutre afin de fiabiliser la liaison électrique. D'autre part, une caractérisation de nouveaux matériaux sans plomb a été réalisée pou

We propose a model of transport in thick-film resistors which naturally explains the observed nonuniversal values of the conductance exponent t extracted in the vicinity of the percolation transition. Essential ingredients of the model are the segregated microstructure typical of thick-film resistors and tunneling between the conducting grains. Nonuniversality sets in as a consequence of wide distribution of interparticle tunneling distances. © 2003 American Institute of Physics.

Deposition, integration and application issues of ferroelectric thin films are briefly reviewed. Applications in ultrasonic micromotors and infra-red sensors are treated in more detail. Current results on stress measurements across the ferroelectric phase transition and on pyroelectric devices are presented.

LTCC (low temperature co-fired ceramic) technology has recently gained a remarkable application potential in sensors field. This can be ascribed to many advantages it offers: the ease of LTCC tape handling providing a great freedom in design and fabrication, feasible processing conditions bringing down the costs, excellent thermal and chemical resistance, and combination of electrical and mechanical functions in a reliable hermetic system. In scope of this, fabrication of an LTCC-based millinewton force sen

Ceramic technologies such as thick-film and LTCC (Low Temperature Cofired Ceramic) are excellent platforms for the fabrication of mesoscale devices such as sensors, actuators, microreactors and MEMS packaging. This work presents two alternative screen-prin ...

In this work, a novel sensor for measuring the viscosity of a gas, based on the combination of a heating cavity, a pressure sensor and a meander with a high resistance to flow, all integrated in low-temperature co-fired ceramic (LTCC) technology, is presented. This paper reports the design, thermal characterisation and modelling of the heater module in quasi-stationary operation. The performance of the heater is satisfactory, and good agreement between experimental and calculated thermal properties is found

A complete six degree of freedom (6 DOF) force/torque sensor has been designed and fabricated, adapted to wrist rehabilitation applications, with the focus laid on simple, straightforward manufacturing processes. This paper details the mechanical design, 3 ...

The tedious and expensive process of attaching SIL contacts to the sensor edges may be advantageously replaced by soldering wires and cables directly to the sensor contact pads. However, this process is a bit more critical, as applying excessive heat can damage contact pad metallisations and alter the sensor characteristics. This document details how to safely solder wires onto the pre-tinned contact pads of MilliNewton B sensors (figure 1), which have been designed to be relatively tolerant to this process

In this work, a low-temperature thick-film dielectric consisting of a high-lead low-temperature glass with a reactive nanoscale filler is characterised to enable deposition of thick-film electronics onto substrates such as glass and metals (steel, aluminium, brass, titanium) which cannot be exposed to the standard high-temperature 850 C thick-film firing cycle. The dielectric is stabilised by reaction of the filler with the lead in the glass. For a TiO2 filler, we get : PbO (glass) + TiO2 (filler) -> PbTiO3

Ceramic and glass hotplates are useful for a wide range of applications, such as solid- oxide fuel cells, microreactors and sensors. This work reviews different encountered hotplate geometries, materials and applications. Simple devices may use standard thick-film technology on elongated substrates. On the other hand, LTCC, due to its excellent structuration characteristics, allows much more design freedom and is the technology of choice for achieving high temperatures in a compact package.

Thomas Maeder

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Processing of Graphite-Based Sacrificial Layer for Microfabrication of Low Temperature Co-fired Ceramics (LTCC)

Sol-gel deposition of PZT thin films on ceramic ZrO2 substrates

Transport nonuniversality and critical behavior of the piezoresistive response in thick-film resistors

Design of the ITER High-Frequency Magnetic Diagnostic Coils

T0001 / MilliNewton force sensor / frequency bandwidth

Stress distribution in cantilever – base joints

Sensors for human-machine-interfaces in smart medical systems – Integration challenges and solutions

Formulation of composite resistive pastes for micro-heater manufacturing

Strength of ceramic substrates for piezoresistive thick-film sensor applications

MilliNewton & CentoNewton - réponse électrique

MilliNewton Bb - série 08-400

A model of transport nonuniversality in thick-film resistors

Ferroelectric thin films for microsystems

Fabrication and characterization of LTCC-based millinewton force sensor: influence of design and materials compatibility on device performance

Formulation and processing of screen-printing vehicles for sacrificial layers on thick-film and LTCC substrates

LTCC thermal gas viscometer – heater module

Thick-film multi-DOF force / torque sensor for wrist rehabilitation

T0004 / Soldering wires to sensor contact pads

Low-temperature thick-film dielectrics stabilised by reaction with a nanocrystalline powder

Ceramic hotplates based on thick-film and LTCC technology