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This study reports on the fabrication and characterization of an event detection subsystem composed of a flexible piezoelectric pressure sensor and the electronic interface to be integrated into an implantable artificial pancreas (IAP) for diabetic patients. The developed sensor is made of an AlN layer, sandwiched between two Ti electrodes, sputtered on Kapton substrate, with a preferential orientation along c-axis which guarantees the best piezoelectric response. The IAP is made of an intestinal wall-interfaced refilling module, able to dock an ingestible insulin capsule. A linearly actuated needle punches the duodenum tissue and then the PDMS capsule to transfer the insulin to an implanted reservoir. The device is located at the connection of the needle with the linear actuator to reliably detect the occurred punching of the insulin-filled capsule. Finite Element Analysis (FEA) simulations were performed to evaluate the piezoelectric charge generated for increasing loads in the range of interest, applied on both the sensor full-area and footprint area of the Hamilton needle used for the capsule punching. The sensor-interface circuit was simulated to estimate the output voltage that can be obtained in real operating conditions. The characterization results confirmed a high device sensitivity during the punching, in the low forces (0–4 N) and low actuator speed (2–3 mm/s) ranges of interest, meeting the requirement of the research objective. The choice of a piezoelectric pressure sensor is particularly strategic in the medical field due to the request of self-powered implantable devices which do not need any external power source to output a signal and harvest energy from natural sources around the patient.

A poly-(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C-61-butyric-acid-methyl-ester (PCBM) bilayer structure has been realized by single step matrix-assisted pulsed laser evaporation (ss-MAPLE) technique using the same solvent for both the polymers under vacuum conditions. Our ss-MAPLE procedure allows the fabrication of polymeric multilayer device stacks, which are very difficult to realize with the conventional solvent assisted deposition methods. A proof of concept bilayer P3HT/PCBM solar cell based on ss-MAPLE deposition has been realized and characterized. This demonstration qualifies ss-MAPLE as a general and alternative technique for the implementation of polymeric materials in hetero-structure device technology.

Gas sensors based on hybrid ZnPc–TiO 2 nanostructures, produced by molecules and clusters both deposited by supersonic beams, demonstrate enhanced properties in terms of sensitivity, stability and recovery times with respect to pure ZnPc. The hybrid sensors produced by successive deposition of the molecules and the TiO 2 clusters show the ability to detect reducing gases, such as methanol, to which the response of metal-phthalocyanines is quite poor. A mechanism based on the formation of chemical bonding, activated by the kinetic energy of the molecules and the strong reactivity of the inorganic clusters, is proposed as being at the basis of electron transfer occurring between the inorganic nanostructure and the molecule. This mechanism would explain the rise of new gas sensing properties of this novel class of nano-hybrid materials.

Undoped and doped microsensors, based on tin oxide, have been prepared by the sol–gel deposition technique. The influence of the ageing of the Ti/Au interdigitated electrical contacts on the responses of the samples has been investigated. In particular, in this paper, are reported the responses of different sensors towards some gases and vapours, discussing the reproducibility, repeatability and the baseline drift during the measurements. SEM and XPS analyses of the samples were performed before and after the working period. The sensors showed a little drift, probably due to the ageing of the electrical contacts that was observed also in the SEM images. Obtained XPS results are in good agreement with SEM images.

Gas sensors have been prepared by using single crystalline MoO3 nanorods. Structures 50-150 nm and up to 15 mu m in length were synthesized by template directed hydrothermal synthesis. Gas sensing tests showed responses to NO2 up to 740% and to NH3 up to 570%. Moreover, preliminary electrical characterizations were performed, as a function of temperature in 20-520 degrees C range temperature, by means of current-voltage measurements. I-V dependence studies show a linear increase in current at low voltage and a quadratic increase at higher voltages. A study of the current-temperature dependence shows that at high temperature current is thermally active and successively decreases that can be explained by taking in account a change of material morphology.

The detection of aroma volatile compounds emitted by extra virgin olive oils (EVOOs) is of key importance in the quality control of this product. Physical–chemical techniques (GC, GC/MS, HPLC) and sensory analysis (panel test) are the classical methods used for this purpose, but they are expensive, time consuming, and do not allow on-line measurements. In this paper a new device, an Electronic Nose, that is a sensor array based on pure and doped SnO2 sol–gel thin films used for the discrimination of different Mediterranean “single-cultivar” EVOOs, was presented. To confirm the sensor array responses, analytical technique like headspace-solid phase micro-extraction/gas chromatography/mass spectrometry (HS-SPME/GC/MS) analysis was applied to the analysis of volatiles compounds in EVOOs samples. Moreover sensory analysis on EVOOs was carried out. The obtained GC/MS data were used to identify the particular compounds and characterize the chemical composition of the EVOOs samples. In addition a chemometric pattern recognition technique was used for multivariate data analysis. The variations in the GC/MS fingerprint of the different samples were analysed using principal component analysis (PCA). Statistical analyses were carried out on data obtained from Electronic Nose, GC/MS and sensory analysis. © 2005 Elsevier B.V. All rights reserved.

Semiconductor sensors based on nanocrystalline SnO2, In2O3 and In2O3–SnO2 thin films have been investigated for detecting low concentration (2–20 ppm) of nitrogen dioxide in dry air. In this work the gas-sensitive layers were prepared by modified sol–gel methods making use of non-standard precursors and a suitable surfactant. The samples have been structurally and morphologically characterized by X-ray diffraction and SEM, respectively. Good gas-sensing responses towards NO2 have been found for all the prepared samples with improved performances for the In2O3–SnO2 based sensor. The performances of the sensors have been discussed according to the surface chemical reactions between the gas phase and the semiconductor.

Undoped and doped tin oxide-based microsensors have been prepared by the sol-gel deposition technique. The influence of the ageing of the Ti/Au interdigitated electrical contacts on the responses of the samples has been investigated. In particular, in this paper, we report the responses of different sensors towards some gases as hexanal, acetone and pentanal discussing the reproducibility and repeatability and the baseline drift during the measurements. The sensors showed a little drift probably due to the ageing of the electrical contacts that we observe by SEM images. SEM results were also correlated with XPS analysis.

Hybrid CoTPP-SnO2 thin films have been obtained by the sol-gel approach coupled with spin coating technique. These films have been deposited onto interdigital electrodes and their performances as chemical sensors have been measured towards the detection of methanol vapors. These CoTPP-SnO2 sensors showed fast and reversible responses towards different concentrations of methanol and best results were obtained at 250 degrees C working temperature, while a sharp decrease was observed at higher temperatures. These results are attributed to the well known catalytic activity of metalloporphyrins, which is not thermally decomposed at 250 degrees C, as confirmed by optical measurements.

We report on the preparation and characterization of titanium dioxide thin film gas sensor devices for application in lambda measurement. The sensor responses to different oxygen concentrations have been analyzed. Moreover, according to a computing software that simulates the composition of exhaust gases for different λ values, we exposed the sensors to different complex mixtures of exhaust gases, calibrating in such a way the sensor for the measurement of lambda.

This work reports on the use of two innovative techniques in the field of gas sensors for preparing nano-structured materials: sol–gel and supersonic cluster beam deposition. By means of sol–gel, nano-structured In 2 O 3 thin films have been prepared and deposited under different deposition parameters on silicon wafer. In this way the results have shown a good compatibility of the method with silicon technology, then potentially suitable to be used in the fabrication of integrated devices. The second technique has been applied for the preparation of nano-structured TiO 2 thin films showing its capability to be used in the fabrication of gas sensor devices, mainly when a good control of the grain dimension is required.

In this paper, we present the first sensor ever built using films grown by supersonic beam of cluster oxides as sensing material. Supersonic cluster beams, produced by a pulsed micro-plasma cluster source have successfully used to prepare nanocrystalline thin films of TiO/sub 2/. The sensors, prepared by using different deposition parameters, were suitable for use in a gas sensor array for electronic nose. Sensors showed a quite good response to ethanol, methanol and propanol. Principal component analysis was used as method for testing the array capability in discrimination and recognition of the volatile compounds.