Publications by Peter Ryser | EPFL Graph Search

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This work presents the preliminary results on application of mineral sacrificial layer that is prepared to structure LTCC (low temperature co-fired ceramic). The proposed method suggests utilization of a sacrificial paste, which remains "permanent" during firing and later removed by chemical dissolution, thus providing an effective support throughout the firing. The paste is based on a mixture of B2O3 and alkaline earth oxides and screen-printed on an LTCC sheet that is laminated with additional LTCC layers

Depending on the materials and processing parameters, composite materials consisting of an insulating matrix and a conductive filler may be electrically insulating, resistive or conducting. Previously, we had manufactured composites consisting of a resin and a conducting magnetic filler, and shown that polymerisation under magnetic field could achieve oriented conductors, with essentially unidirectional electrical conduction. In this work, we explore the possibility of replacing the resin matrix by a thermo

In this work, we present the general concept of an instrumented smart knee prosthesis for in-vivo measurement of forces and kinematics. This system can be used for early monitoring of the patient after implantation and prevent possible damage to the prosth ...

In this work, a low-firing thick-film materials system allowing fabrication of piezoresistive sensors on surgical alloys is presented in detail, with application to a force-sensing surgical instrument. The system comprises a series of individual thick-film dielectric, conductor, resistive and overglaze compositions based on a lead borosilicate glass matrix. The moderate achieved firing temperature, around 625°C, greatly increases compatibility with metallic substrates, allowing the use of high-strength medi

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 this work, a novel low-temperature thick-film system (dielectrics, resistors and conductors) is characterised for application on substrates, which cannot be exposed to the standard high-temperature 850 C thick-film firing cycle. Aluminium alloy sheets are ideal substrate materials for high power electronics, due to their excellent thermal dissipation, mechanical sturdiness, easy packaging and adjustable thermal expansion coefficient (Al-Si system). In addition to standard hybrid electronics, potential ap

In this work, we study in detail the sensing characteristics of piezoresistive force sensors based on structured LTCC (Low Temperature Co-fired Ceramic) cantilevers carrying a thick-film piezoresistive bridge. These devices show much improved sensitivity compared to classical alumina-based devices, but may exhibit abnormally large signal and drift, which indicates the presence of structural defects originating from fabrication issues or deleterious interactions between materials. To eliminate these effects,

In this work, we introduce a simple, low-cost and acid-resistant materials system for carbon-based screen-printed electrodes (SPEs), and apply it to chemical sensing of hexavalent chromium, i.e. Cr(VI), in acid environments, as encountered in bioremediation of industrial effluents. The developed composite materials comprised of 1) dense organic-carbon conductor, 2) porous polymer-carbon-ligand active sensing material, and 3) insulating and protective dielectric. All materials were formulated with two differ

In this paper, the resistive and piezoresistive properties of a commercial resistive composition (Du Pont 2041), often used for strain-gauge applications, are examined on several dielectric compositions, which themselves are deposited onto various ceramic and metal substrates. The choice of suitable dielectrics allows to achieve good adhesion and coverage of the metal substrate, while retaining similar properties of the resistors as on alumina. The combinations of dielectrics and substrates also allows to s

Although LTCC (low temperature co-fired ceramics) technology is an attractive solution for smart-packaging of micro-electronic devices, numerous studies are still underway to overcome the difficulties encountered during processing and application. These difficulties center on chemical and physical issues occurring between the LTCC components during firing. The chemical issues arise from the interaction of the glass phase(s) in the tape and the thick-films, whereas the physical issues are usually due to the

In this work, we investigate the piezoresistive response of epoxy-graphite composites. A resistive thick-film Wheatstone bridge is deposited by screen-printing onto an alumina beam, a weight is then applied on the tip of the beam and the resulting electrical signal response is recorded, allowing the calculation of the gauge factor. The characterization was made at room temperature, 60°C and 100°C for different matrixes (epoxies with different glass transition temperatures, Tg) and particles sizes (4 μm and

The present contribution gives an overview of our work on non-conventional magnetic coil sensors for diagnostics and plasma stability control of nuclear fusion experiments in tokamaks. Instead of wire wound around a core, these devices consist of printed conductor wire coils on ceramic substrates, and are based on LTCC (low-temperature co-fired ceramic) and thick-film technology, which allow creation of monolithic multilayer coils with excellent stability. For 3D sensing, an innovative modular design combin

Piezoresistive sensors based on steel and other metallic substrates provide higher strain response than on standard ceramic substrates and are more easily packaged. But exposing high-strength steels to the standard high- temperature 850°C thick-film firing cycle affects their mechanical properties. In previous studies, we have developed a range of low-firing thick-film materials based on lead borosilicate glass, which allows processing at low temperatures. However, it is desirable to develop alternatives to

We report here on an integrated mini-lamp module (15x26x4 mm3) with a microfabricated rf-powered Rb dielectric barrier discharge (DBD) lamp (10x10x3 mm3) positioned on top of a 0.6 mm thick (thickness adjustable) 4-layer LTCC (Low Temperature Co-fired Cera ...

An innovative method for filling and sealing the reference cell for a Rubidium (Rb) integrated atomic clock is presented. We used a simple, low-temperature solder sealing technique for producing mini-cells of the size of 12 x 10 x 2 mm, suitable for Rb min ...

We examine, in this work, the integration and high-strain response of piezoresistive thick-film resistors on titanium and titanium alloy, as compared with ferritic stainless steel and the standard alumina substrates. In general, titanium and its alloys are relatively ill suited for use as a thick-film substrate using the standard 850 °C firing process, because of its low oxidation resistance and tendency to dissolve oxygen. This problem can be alleviated by applying suitable thick-film glassy protection lay

We have designed and fabricated a low-range (ca. 100 mN) thick-film piezoresistive force sensor with a cantilever beam fabricated in LTCC (Low Temperature Co-fired Ceramic). The beam was soldered onto a standard thick-film 25.4 x 12.7 mm signal conditioning base [1]. Switching from a classical Al2O3-based thick-film beam to LTCC allows design of a 3D structured beam with increased sensitivity of the piezoresistive bridge, yet largely conserved strength and stiffness. Another advantage of LTCC compared to al

In conductor-insulator composites in which the conducting particles are dispersed in an insulating continuous matrix the electrical connectedness is established by interparticle quantum tunneling. A recent formulation of the transport problem in these kind ...

Numerous evidence suggests that thick-film resistors are close to a metal– insulator transition and that tunneling processes between metallic grains are the main source of resistance. By theoretical analysis of various percolative resistor network models we show that the piezoresistive response under imposed uniaxial strain is strongly dependent on the concentration of the conducting phase. In particular, the piezoresistive anisotropy is reduced as the system approaches its percolation threshold, following

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Preparation and application of minerals-based sacrificial pastes for fabrication of LTCC structures

Magnetically tuneable thermoplastic resistive composites

Instrumented Knee Prosthesis for Force and Kinematics Measurements

Low-firing thick-film piezoresistive sensors for medical instruments

Segregated tunneling-percolation model for transport nonuniversality

Integrated thick-film hybrid microelectronics on aluminium substrates

Ultra-low pressure sensor for neonatal resuscitator

Screen-printed electrochemical chromium (VI) sensing electrodes for effluent bioremediation monitoring

Properties of thick-film resistors on dielectric and metal substrates for piezoresistive sensors

Materials compatibility issues in LTCC technology and their effects on structural and electrical properties

Piezoresistive effect in epoxy-graphite composites

LTCC and thick-film ceramic magnetic sensors for tokamak nuclear fusion

Development of low-firing lead-free thick-film materials on steel alloys for piezoresistive sensor applications

LTCC integrated miniature Rb discharge lamp module for stable optical pumping in miniature atomic clocks and magnetometers

Dispensing and Hermetic Sealing Rb in a Miniature Reference Cell for Integrated Atomic Clocks

Signal Stability of LTCC Cantilever Force Sensors

High-strain response of piezoresistive thick-film resistors on titanium alloy substrates

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

Transport properties of nonhomogeneous segregated composites

Piezoresistive anisotropy of thick-film resistors