HIPOT-RR (Slovenia)

This is an exploratory study on the effect of electrolysis, delivered during the thawing stage of a cryoablation protocol, on tissue ablation. This treatment protocol, that combines freezing and electrolysis, is named “cryoelectrolysis”. In cryoelectrolysis the cryoablation probe is also used as the electrolysis delivering electrode. The study was performed on the liver of Landrace pigs and the tissues were examined 24 hours after treatment (two pigs) and 48 hours after treatment (one pig). The cryoelectrolysis device and different cryoelectrolysis ablation configurations tested are described. This exploratory, non-statistical study shows that the addition of electrolysis expands the ablated area in comparison to cryoablation alone and that there is a substantial difference between the histological appearance of tissue treated by cryoablation alone, tissue treated by cryoablation and electrolysis at the anode and tissue treated by cryoablation and electrolysis at the cathode.

PurposeIn this contribution, the design and integration of a piezoelectric vibrating device into low-temperature, co-fired ceramic (LTCC) structures are presented and discussed. The mechanical vibration of the diaphragm was stimulated with a piezoelectric actuator, which was integrated onto the diaphragm. Three different methods for the integration were designed, fabricated and evaluated.Design/methodology/approachThe vibrating devices were designed as an edge-clamped diaphragm with an integrated piezoelectric actuator at its centre, whose role is to stimulate the vibration of the diaphragm via the converse piezoelectric effect. The design and feasibility study of the vibrating devices was supported by analytical methods and finite-element analyses.FindingsThe benchmarking of the ceramic vibrating devices showed that the thick-film piezoelectric actuator responds weakly in comparison with both the bulk actuators. On the other hand, the thick-film actuator has the lowest dissipation factor and it generates the largest displacement of the diaphragm with the lowest driving voltage. The resonance frequency of the vibrating device with the thick-film actuator is the most sensitive for an applied load (i.e. mass or pressure).Research limitations/implicationsResearch activity includes the design and the fabrication of a piezoelectric vibrating device in the LTCC structure. The research work on the piezoelectric properties of integrated piezoelectric actuators was limited.Practical implicationsPiezoelectric vibrating devices were used as pressure sensors.Originality/valuePiezoelectric vibrating devices could be used not only for pressure sensors but also for other type of sensors and detectors and for microbalances.

In the frame of a bilateral project Romania-Slovenia (partners: University ¿Politehnica¿ of Bucharest and ¿Jozef Stefan¿ Institute from Ljubljana) a capacitive pressure sensor with air using LTCC (low temperature co-fired ceramic) and thick-film materials and technologies was developed. After establishing the optimal dimensions from the point of view of the sensitivity as well as costs, question arise concerning the functioning of the sensor in real employment conditions. It has been observed that temperature as well as humidity influence the way the sensor behaves, requiring additional calibration actions. The influence of water vapors was also of interest. In order to fully characterize the sensor, all this influences need to be studied. This paper focuses on characterizing the sensor by highlighting these effects through measurements and, where possible, through simulations.

For temperature sensors in MEMS (the ceramic micro electro-mechanical systems) thick-film temperature-dependent resistors PTC-5093 (Du Pont) and NTC-4993 (Ferro) resistor materials were evaluated. Thick-film piezo-resistors for strain-gauges were realised with Du Pont 2041 (low noise and very stable resistors) and ESL 341-B (high gauge factor) 10 kohm/sq. resistor materials. The PZT paste was prepared from a pre-reacted PZT powder with the composition near the morphotropic phase boundary (Zr/Ti 53/47). Thick-film PTC and NTC thermistors, "normal" low TCR resistors and PTZ piezoelectric pastes were printed and fired on Heraeus HL-2000 LTCC zero shrink substrates. Results obtained on relatively inert alumina substrates were used for the comparison. In most cases the required characteristics of thick film materials on LTCC substrates were inferior to those obtained on relatively inert alumina substrates. This is attributed to the inter-diffusion of oxides, mainly SiO <inf xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</inf> , from the rather glassy LTCC substrates into active layers and presumably also to the diffusion of some from oxides from thick fil layers into LTCC substrates.

The electrical and microstructural characteristics of 1 kohm/sq. thick-film thermistors with high positive (PTC) and negative (NTC) temperature coefficients of resistivity (TCR) fired on green LTCC (Low-Temperature Cofired Ceramics) substrates were evaluated. Electrical characteristics, i.e., sheet resistivities, TCRs and noise indices were measured. Microstructures of thick films were investigated by scanning electron microscopy (SEM) and analysed by energy dispersive X-ray analysis (EDS). Functional phases in thermistors were determined by X-ray powder diffraction analysis. Obtained results were compared with characteristics of thick film thermistors fired on relatively inert alumina substrates which were used as a reference.

Yttria-doped zirconia nanopowders have been obtained using the hydrothermal procedure starting from soluble inorganic salts. The mechanisms and kinetics of the process have been studied to obtain high purity powders with a crystalline size range of 4 to 22nm and specific surface near 200 m2/g. These powders have been have been used to obtain membranes with controlled thickness and with densities over 95% of the theoretical value by employing the tape casting technique using organic binders, dispersants and surfactants. The influence of the additives and sintering regime on the density and microstructure of membranes has been studied. The ionic conductivity of the materials was investigated and modelled. Different types of ruthenate pastes were used to obtain thick resistive films on the zirconia membranes and interactions between the substrate and membranes were studied. Finally the gauge characteristics of the device and possibilities for applications as mechanical pressure sensors with high sensitivity are discussed.