Sensors and Actuators B 117 (2006) 115–122 A WO 3 -based gas sensor array with linear temperature gradient for wine quality monitoring A. Adami a , L. Lorenzelli a,∗ , V. Guarnieri a , L. Francioso b , A. Forleo b , G. Agnusdei c , A.M. Taurino b , M. Zen a , P. Siciliano b a ITC-irst—Microsystems Division, via Sommarive 18, Povo, 38050 Trento, Italy b IMM—Microelectronic and Microsystems Institute, National Council of Research, Department of Lecce, Italy c OPTEL, S.S. 7 per Mesagne, Km 7+300, 72100 Brindisi, Italy Received 5 August 2005; accepted 7 November 2005 Available online 13 December 2005 Abstract In this work we describe the design implementation, validated by experimental results, of an innovative gas sensor array for wine quality monitoring. The main innovation of this integrated array deals with the simultaneous outputs, from a single chip on custom SMD socket, of eight different signals coming from a WO 3 thin film structure heated in a linear temperature gradient mode, allowing an overall evaluation of gas sensing properties of the material in a 100 ◦ C-wide window, typically from 300 to 400 ◦ C. The implemented sensitive layer is a WO 3 film deposed by RF-sputtering. Preliminary tests of gas sensing showed good responses to the target analytes for the specific application (1-heptanol, 3-methylbutanol, benzaldehyde and ethyl-hexanoate). © 2005 Elsevier B.V. All rights reserved. Keywords: Gas sensor array; WO 3 ; Wine quality monitoring; Microhotplates 1. Introduction The monitoring of the quality and safety control in the food industry is an up-to-date topic, because of the important issues of quality of life and health care as well as its possible industrial applications. The organoleptic analysis, based on both analyti- cal methods and trained inspectors who use odour evaluation, is the wider used method to define quality and safety in foods. In many cases, monitoring and determining the constituents of a sample gas typically involves collecting samples and ana- lyzing them in traditional analytical instruments such as gas chromatograph–mass spectrometer (GC–MS) of significant size and cost. In addition, in some cases the sample preparation is time consuming and thus on-line, real-time analysis cannot be easily performed. Besides, many applications, such as the detec- tion of volatile organic compounds (VOCs) or smells generated from food in agro-food industry, need smaller, more portable, cheaper, and even disposable sensor-based systems designed to ∗ Corresponding author. Tel.: +39 0461 314 455; fax: +39 0461 314 591. E-mail address: lorenzel@itc.it (L. Lorenzelli). analyse such complex mixtures. The most important analytical requirement is a high discrimination power capable of distin- guishing between single gases or, more frequently, between gas ensembles. The aim of the work is the evaluation of innovative micro- machined gas sensor array performance into field of wine qual- ity monitoring, looking towards new applications into fast and cheap miniaturized multisensor systems in a more general food quality scenario. In the last decade, the micro-machined gas sensors based on semiconducting metal oxides (MOX) have benefited from a parallel evolution in which micromachining technologies for MEMS, aimed to improve thermal response and power con- sumption of the sensors, have been added to on-chip sensors and electronics. Thus, conductivity sensors based on n-type semi- conducting metal oxides are powerful candidates for the growing demand for cheap and highly sensitive gas sensors [1–2]. However, the selectivity of an individual sensor remains as a problem to be solved. Several approaches, including the study of new sensitive layers [3], advanced sensor array architectures for electronic noses [4,5] and the gas identification by mod- ulating the metal oxide temperature [6–7] have been adopted 0925-4005/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.snb.2005.11.006