D. Aloisio

On paper colorimetric sensor for ascorbic acid detection

In this study, a simple methodology for the development and application of a solid-state sensor for the measurement of ascorbic acid (AA) by means of on paper colorimetric assay, is reported. Ink-jet printing has been used to fabricate paper strips used for the assay. An apparatus for the simple readout of the paper strips, comprising a CMOS camera which allows to acquire RGB (Red, Green, Blue) colors and an image analysis software for data elaboration, has been also developed. The printed paper strips developed allow the determination of AA in practical applications.

Development of Sensing Transducers on Compact Disc Substrates

Here is reported about the development of gold electrodes for sensors starting from high fidelity compact discs (CDs) as substrates. The CDs were chemically etched to remove the protective layers and to expose the metal one. Several transducer layouts were designed by means of electronic CAD, and then, realized with a LPKF rapid prototyping system (Protomat S103). The gold CDs transducers were employed in the realization of resistive sensors and electrochemical ones. Some examples of the use of the prototypes developed are also reported.

Dissolved Oxygen Sensor Based on Reduced Graphene Oxide

The monitoring of dissolved oxygen (DO) in water is of great interest in order to provide information concerning the presence of pollutants or more generally about the health state of aquatic ecosystems. The majority of existing dissolved oxygen analyzers use electrochemical sensors which are accurate, reliable, stable, and require low or zero maintenance. However, these commercial sensors are not very compact and relatively expensive, since the fabrication process is complicated and noble metals are normally used as electrode materials. Herein, we present an electrochemical sensor for the determination of dissolved oxygen, by using reduced graphene oxide (RGO) as the oxygen sensitive probe. We prepared RGO by a chemical reduction method from graphene oxide (GO). A simple sensor was fabricated by printing RGO dispersed in Nafion, on the working electrode surface of a flexible commercial device. The surface and morphological properties of the sensing layer were investigated by XPS and TEM analysis. The electrochemical characteristics of the RGO-modified electrode were investigated by cyclic voltammetry (CV). Amperometric measurements were also performed in order to evaluate the sensor performance. Preliminary tests show good sensitivity and reproducibility. Tests of dissolved oxygen monitoring on environmental samples show the possibility of use in real applications.

A Portable System for the Monitoring of Dissolved Oxygen in Aquatic Environment

Here is reported about the development of a sensing apparatus for dissolved oxygen (DO) in water. The purpose is achieved by means of a home-made electrochemical sensor, with working probe functionalized with Ag-iron oxide nanoparticles, and a readout system based on custom electronics for sensor interfacing and ATMEL microcontroller. Oxygen concentration was varied by bubbling an argon and oxygen mixture at different partial pressure (PO2/P0) into a 1 M phosphate buffer solution (pH = 7.4). A graphical user interface (GUI), developed in Python environment, allows the real-time visualization and recording of data coming from the sensor. The system is biased by USB connection and, employed with a notebook, it can be considered as a portable stand-alone one for outdoor applications.

Optical, electrical and sensing properties of ZnO nanoparticles synthesized by sol-gel technique

Optical, electrical and sensing properties of ZnO nanoparticles, prepared by sol-gel process and subsequent dried in supercritical conditions, are presented. To investigate the morphological and microstructural properties, transmission electron microscopy (TEM), X-ray powder diffraction (XRD), UV-visible spectroscopy and photoluminescence (PL) spectroscopy analysis have been used. From microstructure analysis we showed that pure ZnO nanoparticles were polycrystallines and exhibited the hexagonal wurtzite structure. Chemoresistive sensor consisting of a thick layer of ZnO nanoparticles annealed at 400 °C for 2h in air on interdigitated alumina substrate has been fabricated and its electrical and sensing characteristics were investigated. The sensor performances towards carbon monoxide (CO) with and without UV illumination were reported. An increase of sensitivity, along a reduction of ZnO thick film resistance, was observed when the sensor operates under UV irradiation.

A Low Cost Inkjet Deposition System for Sensors Development

This paper reports on the development of an inkjet deposition apparatus for the realization of low cost sensing devices. The printing system is based on a HP720 printer modified with custom mechanics and electronics. The developed system is able to print aqueous inks of multiwalled carbon nanotubes (MWCNT) composites with poly(methacrylic acid) (PMA) or poly(diallyldimethylammonium chloride) (PDDAC). The thickness and electrical resistance of the printed films can be modulated simply by varying the printing cycles. Examples of the reliable ink-jet printing of MWCNTs/PMA and MWCNTs/PDDAC film on different kinds of substrates are reported.

Arduino-Based Shield for Resistive Gas Sensor Array Characterization Under UV Light Exposure

In this paper, the development and validation of a shield prototype for resistive sensor array characterization with Arduino UNO, a platform based on ATmega328 microcontroller provided by ATMEL, is reported. The resistance variation of the sensor can be evaluated by properly choosing the capacitance value and by measuring the period (frequency) of a custom inverter-based oscillator. The GUI and the developed firmware are able to perform the real-time monitoring of the sensor responses. The developed shield is able to measure the response of up to six sensors under UV radiation by means of LED devices. First results carried out with resistive sensors based on mesoporous In2O3-based material under UV light exposure are reported.

Sensing Properties Characterization of a Poly (Diallyldimethylammonium Chloride)-Based Saw Device

In this paper is reported about the development and characterization of Surface Acoustic Wave Sensors for ethanol vapors monitoring. The SAW devices are fabricated by inkjet printing a water-based solution of PDDAC (poly(diallyldimethylammonium chloride)) on commercial SAW resonators with nominal resonance frequency value of 433.92 MHz. A thin polymeric film acting as sensing element is achieved on the top of the piezoelectric substrate. The devices are characterized by means of custom oscillator circuits. The experimental activities regarding the Pierce like oscillator circuit development are also reported.

Development of Electronic-Nose Technologies for Biomedical Applications

In this paper the development of an electronic nose for biomedical applications is reported. The key concept guiding the development of the analyzer has been the portability, its easy use, and interface with the patient and hospital facilities. With this in mind, a small analyzer with an e-nose, comprising commercial gas sensors and a breath sampling device, was assembled and tested. After the calibration tests carried out in laboratory, the real-time breath monitoring of patients under hemodialysis treatment has been performed to validate the developed analyzer.

Polymer/Metal Oxides Composites on Flexible Commercial Substrates as Capacitive Sensors

The development of a low level humidity capacitive sensing device working at room temperature, based on a thick layer of iron oxide nanopowders dispersed into a poly(diallyldimethylammoniumchloride) (PDDAC) hydrophilic host matrix deposited on flexible commercial plastic substrates provided with silver electrodes, is reported. The sensor response was tested in a transduction system based on a capacity-frequency conversion of the timing circuit by means of a microcontroller unit. The sensor was investigated in the absolute humidity range from 0% to 1%, showing a good sensitivity and response linearity.