Emanuela Proietti

The evaluation of quality of post-harvest oranges and apples by means of an electronic nose

Abstract The measure of quality of post-harvest fruits is considered a promising application field for electronic nose technology such as the detection of defects. Among the possible defects present in fruits those due to post-harvest treatment are particularly important. Among them defects like mealiness (due to post-harvest over-ripening), skin damage (due to mechanical or temperature stresses), and infections affect strongly the perception of consumers. They have to be avoided in order to achieve high quality products. In this paper, the study of the variations of aroma of oranges, during the storage, and apples, due to the presence of mealiness and skin damage by means of a thickness shear mode quartz resonators- (TSMR) based electronic nose, is illustrated and discussed. Results have evidenced that the electronic nose has enough sensitivity and resolution to distinguish among the various classes and to correctly predict the amount of defects (for apples) and storage days (for oranges).

Electronic nose based investigation of the sensorial properties of peaches and nectarines

Abstract Quality of fruit is traditionally associated with the physical characteristics, such as surface colour, shape, and firmness. Although, it is well known that the aroma is also associated with the ripening processes, this feature never resulted in any practical instrumentation due to the complexity of the aroma analysis. Over the past years, electronic nose technology opened the possibility to exploit information on aroma to assess fruit ripening stage, and more generally, fruit quality. In order to match the instrumental analysis with the consumer requirements, a sensorial profile of the fruit is necessary. From the point of view of sensory analysis, fruits have not been extensively studied and a complete and detailed description of the aroma components is not well established. In this paper, an electronic nose and a sensory panel are considered together in order to study the sensorial properties of a number of peaches and nectarines. Fruits were divided into four classes; each composed of several cultivars. The research is aimed at evaluating the sensorial features typical of each class. This work represents a first attempt toward the definition of a sensorial profile for these fruits, and it can be considered a further proof of the fruitful interactions between natural olfaction and electronic nose.

Development of a ChemFET sensor with molecular films of porphyrins as sensitive layer

The interaction of chemical species with molecular films of porphyrins causes variations of the work function of the film itself, as it has been recently demonstrated by using the Kelvin probe technique. This characteristic makes porphyrins films suitable to be used as sensitive layers in ChemFET sensors. In this paper, we present a preliminary report about the fabrication and testing of such gas sensitive devices. The technological solutions towards an optimised device are also illustrated and discussed.

Comparison and integration of arrays of quartz resonators and metal-oxide semiconductor chemoresistors in the quality evaluation of olive oils

Abstract Olive oil analysis is considered as a promising application of electronic noses. In this paper, two electronic noses, based on different sensor technologies (quartz resonators and metal-oxides chemoresistors) are applied to the measure of samples of olive oils of different qualities and values. Among them, samples of oil produced from organically farmed olives have also been measured. While both the sensor systems provided very similar images for the commercial oils defining a sort of quality growing direction in their principal component analysis score plots, the organically farmed product has been differently interpreted by the two arrays. Merging of data, both at high and low abstraction level, shown that the co-operation of the two sensor arrays identified the organically farmed product different from the commercial samples. Details about the single sensors behavior, and the option of sensors data fusion will be illustrated and discussed.

Dielectric charging in microwave microelectromechanical Ohmic series and capacitive shunt switches

The charging of the dielectric used for the actuation in microelectromechanical system (MEMS) devices is one of the major failure sources for switches based on this technology. For this reason, a better understanding of such an effect is vital to improve the reliability for both ground and space applications. In this paper, the expected response of MEMS switches to unipolar and bipolar dc actuation voltages has been measured and modeled. Two configurations of MEMS switches, namely, an Ohmic series and a shunt capacitive one designed for microwave applications, have been studied as a test vehicle for charging effects related to the dc actuation pads. The recorded data have been interpreted mainly through the Poole–Frenkel effect due to charge injection when a high voltage is applied to the dielectric layer. Metal-Insulator-Metal (MIM) structures have been also considered as a complementary information for the response of the dielectric material.

Analysis of a transmission mode scanning microwave microscope for subsurface imaging at the nanoscale

We present a comprehensive analysis of the imaging characteristics of a scanning microwave microscopy (SMM) system operated in the transmission mode. In particular, we use rigorous three-dimensional finite-element simulations to investigate the effect of varying the permittivity and depth of sub-surface constituents of samples, on the scattering parameters of probes made of a metallic nano-tip attached to a cantilever. Our results prove that one can achieve enhanced imaging sensitivity in the transmission mode SMM (TM-SMM) configuration, from twofold to as much as 5× increase, as compared to that attainable in the widely used reflection mode SMM operation. In addition, we demonstrate that the phase of the S21-parameter is much more sensitive to changes of the system parameters as compared to its magnitude, the scattering parameters being affected the most by variations in the conductivity of the substrate. Our analysis is validated by a good qualitative agreement between our modeling results and experimen...

Analytic Modeling Of RF MEMS Shunt Connected Capacitive Switches

Abstract —This paper deals with a general analytic approach for the design of RF microelectromechanical system (MEMS) switches. The chosen configuration for these microwave devices is composed of twocoplanar transmission line sections separated by a metal membrane providing a shunt connected variable impedance. Using a bias voltage it is possible to actuate the switch. The adopted methodology for the development of the circuital model is based on the image impedance parameter representation of a two-port network. Synthesis equations are presented, and design considerations are discussed. The proposed approach is validated by means of electromagnetic simulations.

RF MEMS ohmic switches for matrix configurations

Two different topologies of radio frequency micro-electro-mechanical system (RF MEMS) series ohmic switches (cantilever and clamped–clamped beams) in coplanar waveguide (CPW) configuration have been characterized by means of DC, environmental, and RF measurements. In particular, on-wafer checks have been followed by RF test after vibration, thermal shocks, and temperature cycles. The devices have been manufactured on high resistivity silicon substrates, as building blocks to be implemented in different single-pole 4-throw (SP4 T), double-pole double-throw (DPDT) configurations, and then integrated in Low Temperature Co-fired Ceramics (LTCC) technology for the realization of large-order Clos 3D networks.

Charge transport in pentacene and porphyrin-based organic thin film transistors

Transport properties of a field effect transistor based on pentacene have been investigated by experimental and numerical analysis. Moreover, thin film transistors based on porphyrin have been realized and characterized. In order to derive from basic principles the transport properties of the organic semiconductors, we used a Monte Carlo (MC) simulator to calculate the field-dependent mobility. The overall device simulation is performed by using two-dimensional drift-diffusion simulations taking into account field-dependent mobility obtained from MC simulations, interface/bulk trap states and fixed charge density at the organic/oxide interface. We demonstrate how carrier mobility can be extracted from experimental device characteristics, without using the conventional MOSFET theory that could lead to the wrong result. Finally we demonstrate the realization of simple organic logic circuitry, namely an organic inverter with a different configuration of load transistor.

Modeling of APCVD-doped silicon dioxide deposition process by a modular neural network

This paper describes a methodology based on the combined utilization of both a multisensor system and an optimized artificial neural network that has been applied to equipment utilized for the production of doped silicon dioxide films. The model exhibits an average relative error around 1% in predicting the concentrations of dopants and the thickness of the oxide layer. One of the major benefits of such a predictor is the ability of providing an on-line estimate of the process yield, thus avoiding off-line testing and gaining a significant reduction of risks of wafer loss. The neural model here described is currently utilized as a control tool at the Texas Instruments Avezzano, Italy, plant.