Simone Pantalei

Biomimetic sensing layer based on electrospun conductive polymer webs

The aim of the present study is to combine a bio-inspired nanofibrous artificial epithelium to the electronic nose (e-nose) principles. The sensing device set up was an electronic nose consisting of an array of 9 micro-chemoresistors (Cr-Au, 3×3) coated with electrospun nanofibrous structures. These were comprised of doped polyemeraldine base blended with 3 different polymers: polyethylene oxide, polyvinilpyrrolidone and polystyrene, which acted as carriers for the conducting polymer and were the major responsible of the features of each fibrous overlay (electrical parameters, selectivity and sensitivity ranges). The two sensing strategies here adopted and compared consisted in the use of 2 different textural coatings: a single- and a double-overlay, where the double-overlay resulting from overdeposition of 2 different polymer blends. Such e-nose included a plurality of nanofibres whose electrical parameters were at the same time depending on each polymer exposure to analytes (NO(2), NH(3)) and on the spatial distribution of the interlacing fibres. The morphology of the coating arrangements of this novel e-nose was investigated by scanning electron microscopy (SEM) and its sensor responses were processed by multicomponent data analyses (PCA and PLS) reporting encouraging results for detection and recognition of analytes at ppb levels.

Large-Scale Chemical Sensor Array Testing Biological Olfaction Concepts

Biological olfactory systems are characterized by a large number of sensors with broad overlapping specificities. The sensitivity and selectivity of the system may be enhanced by the huge redundancy of the olfactory receptor neurons (ORNs). A European project, NEUROCHEM, was devoted to test computational models of the olfactory system of vertebrates and insects. To test these models, a realistic artifact of the olfactory epithelium was developed as a large sensor array mimicking some features of biological ORNs, in particular, the broad and overlapping selectivity to many odors, the combinatorial response, the high level of redundancy, and the different dynamic ranges exhibited by same types of ORNs. The sensor array is composed of 16 384 elements arranged in four smaller arrays of 64 × 64 interdigitated electrodes deposited on a borosilicate substrate. To mimic the redundancy of the biological ORNs, tens of organic conductive polymers were chosen as active sensing materials because of their broad and diverse, but overlapping, specificity to different classes of volatile organic compounds. These sensors were characterized by their responses to varying concentrations of test analytes. The collected sensor data were processed with standard multivariate techniques and the results are reported in this paper.

Alcohol vapor sensory properties of nanostructured conjugated polymers

The response to relative humidity (RH) and alcohol vapors of resistive-type sensors based on nanobeads of conjugated polymers, namely polyphenylacetylene (PPA) and copolymer poly[phenylacetylene-(co-2-hydroxyethyl methacrylate)] (P(PA/HEMA)), were investigated. Sensors based on ordered arrays of these nanostructured polymeric materials showed stable and reproducible current intensity variations in the range 10–90% of relative humidity at room temperature. Both polymers also showed sensitivity to aliphatic chain primary alcohols, and a fine tuning of the sensor response was obtained by varying the chain length of the alcohol in relation to the polarity. The nanostructured feature of polymeric-based membranes seems to have an effect on the sensing response and an enhancement of the sensitivity was observed for the response to water and alcohol vapor variations with respect to previous studies based on amorphous polyphenylacetylene. High stability of the polymeric nanostructured membranes was detected with no aging after two weeks in continuum stressing measurement conditions.

Enhanced Sensory Properties of a Multichannel Quartz Crystal Microbalance Coated with Polymeric Nanobeads

In this study the sensorial performances of a four-channel quartz crystal microbalance implemented on a single quartz plate are reported and compared with those of four independent quartz crystal microbalances. Particular attention has been devoted to both cross talk in responses and sensor sensitivity. A recently synthesized nanostructured polymer, poly[phenylacetylene-(co-2-hydroxyethyl methacrylate)], has been used as chemical interactive material. The interactions of our sensor system with relative humidity are also reported. The multichannel device shows a better homogeneity of the mass sensitivity with a spread of the values less then 4% compared to a 50% spread observed in the set of four microbalances.

Very large chemical sensor array for mimicking biological olfaction

Olfactory receptor neurons (ORN) in the mammalian olfactory system, transduce molecular properties of the odorants into electrical signals and project these into the olfactory bulb (OB). In the biological system several millions of receptor neurons of a few hundred types create redundancy and the massive convergence of the ORNs to the OB, is thought to enhance the sensitivity and selectivity of the system. To explore this concept, the NEUROCHEM project will build a polymeric chemical sensor array consisting of 216 (65536) sensors with tens of different types. To interface such a large sensor array, a topological array configuration with n rows and m columns, has been adopted, to reduce the total wiring connections to n+m. A method of addressing a single element in the array in isolation of the rest of the network has been developed. Over the array ten different conductive polymers with different sensing characteristics will be deposited by means of electrodeposition and inkjet printing. A smaller prototyp...

Interdigitated sensorial system on flexible substrate

In this paper we present the design and fabrication of two flexible sensor devices: humidity sensor and ammonia sensor integrated with electronic circuit interface on thin flexible substrate (8 mum). The transducers layout has been optimized by means of numerical simulations. A thin layer of Bisbenzocyclobytene (BCB) is used as dielectric sensitive material in humidity sensor. Conversely a mixed polymer layer based on polyaniline emeraldine base (PANi-EB) is used as sensing conductive polymer for ammonia.

Comparison Between Sensing Systems for Ammonium Detection And Measurement In Soil

Usually, ammonium in soil is carried out through steam distillation of ammonia obtained after alkalinization of soil extracts and further back titration of the collected solutions. Alternatively, ion selective electrodes (ISE) specific for ammonium ions can be used, in order to measure their concentration in aqueous soil extracts. The aim of this study is to assess the possibility to use, alternatively to the previous techniques, two kinds of chemical sensors able to measure NH3, such as an interdigital microelectrode (IDE) coated of conductive polymer and a sensors array, usually named electronic nose (EN), based on quartz crystal microbalances (QCMs) covered with functionalized polymers. These sensors were chosen on the base of their ability to detect NH3 in sample headspace (specifically or aspecifically, respectively). Therefore, NH4+ in solution was converted to NH3 by alkalinizing soil extracts. Sensors were calibrated at first against known concentrations of NH4+. Results were compared with those o...

Measurement of carbon dioxide hydration by carbonic anhydrase entrapped in submicrometer-sized nanoreactor

This work describes a biosensor for direct measurements of carbon dioxide (CO2). The functionality of this device was tested by a QMB transducer coated by a liposome containing carbonic anhydrase (AC). During the CO2 adsorption process a change in the QMB frequency was observed. Another transducer was used in this context. By a high resolution temperature variation transducer, such as the LiTaO3. It has been possible to detect the heat generated during the reaction CO2 +H2O -->HCO3- + H+ occurring inside the liposomes. In this work, the response curves of QMB and LiTaO3 are shown and commented.