Publications de Peter Ryser | EPFL Graph Search

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Although inorganic thick-film materials are usually very stable, load sensors (i.e. force, torque and pressure) based on the piezoresistive effect of thick-film resistors often exhibit some drift, with major contributions stemming from a) temperature changes or gradients, coupled with the temperature coefficient of resistance (TCR) of the sensing bridge resistors, and b) ill- defined mechanical boundary conditions, due to insufficient decoupling, plastic deformation used materials, friction or loading error

Force and pressure sensing technology applied to smart surgical instruments as well as implants allow to give a direct feedback of loads to the surgeon lead to better reliability and success of surgical operations. A common technology used for sensors is l ...

A vast class of disordered conducting-insulating compounds close to the percolation threshold is characterized by nonuniversal values of transport critical exponents. The lack of universality implies that critical indexes may depend on material properties ...

Recently, high-strength zirconia-toughened alumina (ZTA) ceramic substrates have attracted interest, because they offer much improved mechanical properties over straight alumina, while maintaining advantages such as good thermal conductivity and chemical stability. This allows their application in high-power electronics and piezoresistive thick-film sensors, where the substrate is subjected to considerable stress. This work examines the impact of processing a range of thick film materials (Ag- and Au-based

We report on our Monte Carlo calculations of the conductivity of monosized and conducting spherical particles dispersed in a homogeneous matrix, with interparticle transport mechanism given by electron tunneling. We show that our numerical results can be r ...

The piezoresistive effect of thick-film resistors has found widespread application in pressure and force sensors due to their high strain-sensitivity, stability and low-cost. The main material requirements for these applications are a high piezoresistive response, low noise and low temperature dependence. However, many useful elastic substrate materials are degraded at the standard thick-film processing temperature of 850 °C, and therefore require a lower one. This is achieved by engineering the glass compo

Polymer adhesives offer a viable method for mounting silicon dies for high temperature applications. Here a test vehicle for comparing the thermal conductivity of different die attach materials is presented. The setup can be used to determine the degree of ...

This article describes the design and fabrication of a hermetic LTCC package for an optical MEMS chip designed for space applications. The package must ensure electrical and optical connections, mechanical positioning, atmosphere control, and finally low thermally induced stress on the MEMS during final packaging operation. The package consists of a 10-layer LTCC case with a recessed cavity for the MEMS chip, and glass lid (with antireflection coating and thin-film metallisation for soldering) for optical I

In conductor-insulator nanocomposites in which conducting fillers are dispersed in an insulating matrix, the electrical connectedness is established by inter-particle tunneling or hopping processes. These systems are intrinsically non-percolative and a coh ...

A novel sensor based on thick-film + LTCC (low-temperature cofired ceramic) technology has been recently developed for sensing high-frequency 3D magnetic fields in tokamak fusion devices. For integration within the walls of the tokamak, the sensor has to be connected to the mineral-insulated cabling, which is carried out by brazing to ensure sufficient thermal stability. However, thermal mismatch stresses between the braze and the cable vs. the alumina substrate may cause local cracking of the latter during

The aim of this work is to examine the possibility of high performance pressure sensors based on piezoresistive thick films deposited on steel membranes, which combine the performance advantage of thin-film sensors (high-strength steel substrates, assembly without elastomer seal) with the low cost of ceramic thick-film sensors. As standard thick-film firing conditions degrade the properties of most high-strength steels, two routes were explored: 1) application of a special steel, which does not undergo mech

LTCC and thick-film technologies constitute excellent platforms for hermetic and controlled-atmosphere packaging, for applications in MEMS, space, micro/nanofabrication and biological fields. This work presents an active oxygen getter module, based on an integrated LTCC micro-hotplate coated with an oxygen-reactive metal in thick-film form. Gettering is activated by heating the platform, and getter consumption is monitored by the increase of its electrical resistance. Different reactive metals, ceramics or

A Venturi-type flow sensor has been designed and fabricated for neonatal respiratory assistance to control airway pressure and tidal volume. As the low flow range and sensing principle require the measurement of correspondingly very low pressures, a very responsive sensor, based on a polymer membrane acting onto a piezoresistive cantilever force sensor based on low-temperature co-fired ceramic (LTCC), was developed. This paper details the 3D modelling, manufacture, assembly and characterisation of the senso

Purpose: The resistivity dependence on temperature of composite resistors made of carbon fillers dispersed in an organic matrix are known to be strongly affected by the matrix thermal expansion. High positive temperature coefficient (PTC) effects, i.e. ess ...

The retention, diffusion and structural properties of 2–4 nm nanoporous alumina membranes were investigated in view of their integration as size-selective interface in a glucose sensor. These membranes exhibit remarkable glucose diffusion properties with o ...

The introduction of micro-spacecrafts in the space industry has led to the development of various micro-propulsion techniques. Microthrusters are micropropulsion devices used in a microspacecraft for precise station keeping, orbit adjustment, attitude control, drag compensation and apogee kicking. The principle of operation of a solid propellant thruster is based on the combustion of a solid energetic material stored in a microfabricated chamber. In the current work, Low-Temperature Co-fired Ceramic (LTCC)

In this work, we present an integrated flow / pressure / temperature multisensor in LTCC (low- temperature co-fired ceramic) technology designed for diagnostics monitoring of standard industrial compressed air circuits and devices, such as valves and actuators. The pressure sensor is based on a membrane carrying a thick-film piezoresistive Wheatstone bridge. Flow is sensed using the constant- temperature anemometric principle, with the sensing thermistors placed in a fluidics channel, which also comprises s

We propose a theory of the origin of transport nonuniversality in disordered insulating-conducting compounds based on the interplay between microstructure and tunneling processes between metallic grains dispersed in the insulating host. We show that if the metallic phase is arranged in quasi- one-dimensional chains of conducting grains, then the distribution function of the chain conductivities g has a power-law divergence for g-->0, leading to nonuniversal values of the transport critical exponent t. We ev

In industrial applications, the controlled adjustment (trimming) of resistive elements via the application of high voltage pulses is a promising technique, with several advantages with respect to more classical approaches such as the laser cutting method. The microscopic processes governing the response to high voltage pulses depend on the nature of the resistor and on the interaction with the local environment. Here we provide a theoretical statistical description of voltage discharge effects on disordered

Peter Ryser

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Thick-film Load-sensing bridges – Effect of Temperature and Mechanical Boundary Conditions

Load sensing surgical instruments

Study of electrical properties of piezoresistive pastes and determination of the electrical transport

Effect of thick-film materials on the mechanical integrity of high-strength ceramic substrates

Electron tunneling in conductor-insulator composites with spherical fillers

Effect of composition and microstructure on the transport and piezoresistive properties of thick-film resistors

Test vehicle for studying thermal conductivity of die attach adhesives for high temperature electronics

Hermetic package for optical MEMS

Tunneling conductivity in composites of attractive colloids

Porous thick-film silver metallisation for thermally mismatched brazing operations in tokamak magnetic sensor

High performance thick-film pressure sensors on steel

Hermetic package for optical MEMS

LTCC active oxygen getter module for hermetic packaging applications

Ultra-low pressure sensor for neonatal resuscitator

Tuneable PTC effect in polymer-wax-carbon composite resistors

Size-selective diffusion in nanoporous alumina membranes for a glucose affinity sensor

Realization of a solid-propellant based microthruster using low temperature co-fired ceramics

SMD pressure and flow sensor for compressed air in LTCC technology with integrated electronics

Piezoresistivity and conductance anisotropy of tunneling-percolating systems

A random-resistor network model of voltage trimming