Publications by Thomas Maeder | EPFL Graph Search

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Background. The small characteristic sizes (in the range of 102 - 103 μm) of Microstructured reactors (MSR) lead to very high specific interfacial area which, in turn, increases heat- and mass transfer efficiency. However, for quasi instantaneous exothermic reactions, the overall reaction kinetics in MSR is strongly influenced by mixing. The characteristic time of the latter phenomenon varies from millisecond to seconds depending on the operating conditions used. If mixing is the rate determining step for h

Micro solid oxide fuel cells (μ-SOFCs) based on MEMS fabrication processes have become an increasingly attractive option for portable power generation applications, due to their high power density and their compatibility with hydrocarbon fuels. For system packaging, the silicon-based fuel cell membrane module needs to be integrated together with other functional elements such as the gas processing unit and the post-combustor. Silicon wafer bonding techniques can be utilized to avoid thermo-mechanical stress

In recent years there has been a strong effort to reduce the size and power consumption of vapour cell atomic clocks [1,2]. The progress in this direction is driven by several factors such as the use low power laser diodes (VCSEL), Coherent Population Trapping resonances (CPT), and micro-fabricated (MEMS) alkali-vapour cells. Here the micro-fabrication of vapour cells has proven a challenging task. All results reported on this task use anodic bonding at high-temperatures (>300°C) to seal the cell [3]. Howev

Low temperature micro-solid oxide fuel cell (micro-SOFC) systems are an attractive alternative power source for small-size portable electronic devices due to their high energy efficiency and density. Here, we report a thermally self-sustainable reformer – ...

Recently, the development of micro-scale solid oxide fuel cells (µ-SOFCs) has become a promising research topic in the area of portable energy production. A µ-SOFC system, which can provide 1 to 2 W electrical power under an operating temperature of 550°C 1-2, mainly consists of a fuel processor, an electrochemical power generator, and a post combustor. The role of the fuel processor is to generate a hydrogen-rich product stream that is fed to the power generation module. In previous works, various micromac

An integrated system of a microreformer and a carrier allowing for syngas generation from liquefied petroleum gas (LPG) for micro-SOFC application is discussed. The microreformer with an overall size of 12.7 mm × 12.7 mm × 1.9 mm is fabricated with micro-e ...

We investigate in this work the fabrication of polymer micro-fluidic and micro-mechanical devices based on sublimable compounds as sacrificial layers, using a thick-film screen-printing deposition process. Fabrication of printed polymer microstructures featuring properties such as low cost, transparency and biocompatibility is particularly attractive and suitable for disposable biomedical devices. Channel, cavities and spacings for micro-devices are first defined by sacrificial material layers. This is foll

The miniaturized solid oxide fuel cells (µ-SOFCs) has become an intensively studied device for portable power generation technology due to its wide choice of hydrocarbon fuels, its high energy density and its great operation efficiency. It is being considered as a battery replacement [1]. The µ-SOFC system, which aims to provide electrical energy (≤ 10 W) at an operating temperature of ca. 550°C, consists of a fuel cell unit for the electrochemical conversion [2-3]; a fuel processing unit for the thermal st

Highlights • A “plug-and-play” microreaction system for high-temperature reactions (>500 °C). • Efficient thermal decoupling for using standard electrical/fluidic connections. • Automatic and accurate temperature control for calorimetric measurements. • A ...

Current low temperature electronics (175°C) for prolonged periods of time require packaging technologies that have to tackle many new problems. At high temperatures traditionally used materials such as organic circuit boards, adhesives and standard solders degrade rapidly or undergo changes in structure and pro

Micro-scale solid oxide fuel cells (μ-SOFCs) based on microfabrication processes have been found to be interesting as a battery replacement for portable power generation. The system consists of a fuel cell element, a fuel processing unit, a thermal control system and packaging for the electrical and fluidic connections as well as for mechanical support. The system is capable of operating above 500°C under both oxidizing and reducing atmospheres. Due to the relatively large size, complex fluidics and silicon

Micro solid-oxide fuel cells (μ-SOFCs) based on microfabrication processes are a promising alternative to batteries for supplying portable electronics, as very high energy densities may be achieved. However, a complete μ-SOFC module is a quite intricate structure, comprising 1) a gas-processing unit (GPU) to process a convenient energy source such as lighter gas into a more usable form, 2) the energy-generating cells proper, and 3) a post-combustor. The mechanical integration of these elements and their flu

A common problem when using piezoceramic actuators for precise positioning is their hysteresis. Either external sensors such as capacitive or inductive probes, optical sensors or strain gauges are commonly used. The latter are the most favorable solution in many cases, as they occupy the smallest volume and disturbances can mostly be avoided. Drawbacks are the assembly of these strain gauges on the target, their small gauge factor and their size. We propose a sensor based on thick-film technology which perm

The authors report the fabrication and characterization of chemiresistive sensors, composed of a thermoplastic elastomer (TPE), styrene‐ethylene‐ran‐butylene‐styrene, and a high‐structure carbon black (CB) targeted for detecting hydrocarbons at or near roo ...

To monitor high-frequency fluctuations of the equilibrium magnetic field in tokamaks, a 3D magnetic sensor has been developed. The sensor, which is positioned inside the vacuum vessel behind the protective tiles of the tokamak and is exposed to potential temperatures up to 400°C, is based on thick-film and LTCC (low-temperature co-fired ceramic) technology. To connect the sensor to the cabling that runs inside the vacuum vessel, mineral-insulated cables have to be brazed to the sensor to ensure electrical c

The present work critically reviews the scientific and patent literature on low-melting bismuth-based oxide glass frits in materials for electronics, sensors and related applications such as sealing glasses, solar cells, architectural and automotive glass, ...

Quasi-instantaneous exothermic reactions lead to the formation of unwanted hot spots even when carried out in conventional microstructured reactors (MSR) with tube diameter of 100 − 1000 μm. For this reason, alternative MSR designs are warranted to enable ...

This paper presents the design and thermal characterization of a 15 × 22 mm2 LTCC module dedicated to the packaging of the elements of a miniature atomic clock. This module acts as a carrier for the components of the clock as well as temperature controller; this is particularly attractive since each component of the atomic clock requires precise and well defined working temperatures. For the thermal characterization of the designed module, various thermal simulations have been performed, by finite-element m

We investigate in the present work the fabrication of polymer-based micro-fluidic and micro-mechanical devices using sacrificial, resistive/conductive pastes, through a screen-printing process. An organic sacrificial paste is first screen-printed onto a su ...

Biogas is a fuel made from the anaerobic digestion of organic material to form methane. It can be used to power a stationary engine to generate electricity making it a viable method of decentralised power generation from renewables. However, biogas is a mixture of methane and carbon dioxide, and other trace gases such as hydrogen, hydrogen sulphide and oxygen. As such the quality can vary and setting the air-fuel ratio for efficient combustion can be problematic under these conditions. The Wobbe Index, or W

Thomas Maeder

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Effect of hot spots in microstructured reactors on product distribution during quasi-instantaneous exothermic reactions

An evaluation of thick-film silver die-attach as micro solid oxide fuel cells (μ-SOFCs) interconnection packaging

CPT spectroscopy on low-temperature sealed MEMS rubidium vapour cells

A thermally self-sustained micro-power plant with integrated micro-solid oxide fuel cells, micro-reformer and functional micro-fluidic carrier

A novel fuel processing platform for micro-scale solid oxide fuel cells

Syngas generation from n-butane with an integrated MEMS assembly for gas processing in micro-solid oxide fuel cell systems

Fabrication of polymer micro-devices based on organic sacrificial pastes

Development of a low temperature co-fired ceramic fuel processor for the micro-scale solid oxide fuel cell system

Design and packaging of a highly integrated microreactor system for high-temperature on-board hydrogen production

Packaging technologies for high temperature control electronics

A new platform concept for micro-scale SOFC using low temperature co-fired ceramic technology

Ceramic modules for micro solid-oxide fuel cells

Integrated sensors for PZT actuators based on thick-film resistors

Inkjet‐Printed Composites for Room‐Temperature VOC Sensing: From Ink Formulation to Sensor Characterization

Solutions for thermally mismatched brazing operations for ceramic tokamak magnetic sensor

Review of Bi2O3-based glasses for electronics and related applications

Multi-injection microstructured reactor for intensification of fast exothermic reactions: proof of concept

Thermal characterization of an LTCC module for miniature atomic clock packaging

Fabrication of Polymer-Based Micro Devices: Formulation and Study of the Paste

Validation of Novel Wobbe Index Sensor for Biogas Cogeneration