eNose - Design, Applications and Challenges

This article is a republished version of the Technical Article Board at SSET

Abstract

Sensors are widely used today to collect local databases on various parameters. In this article, a sensor which can measure olfactory(smell) signals is presented. The eNose or the Electronic Nose is a biologically inspired sensor, having origins in the functioning of the mammalian olfactory system. A review of the various sensing techniques along with the classification methods and applications are presented.

Introduction

The term ``electronic nose" was coined in 1988 by Gardner and Bartlett wherein they defined e-nose (EN) as ``an instrument which comprises an array of electronic chemical sensors with partial specificity and appropriate pattern recognition system, capable of recognizing simple, or complex odours". The design of the sensor replicates the functioning of the mammalian olfactory system, although it has some limitations. For instance, EN's are more application specific, that is the sensor available for bio-sensing cannot be employed for food testing or environment monitoring. Recently, chemical based sensors are employed in measuring food quality and in select beverages and fast foods. The figure below illustrates the broad parts of the eNose.

How it is done : Components that are used

The eNose consists of the following components :

• Multiple Sensor Array
• Data Acquisition System
• Pattern Recognition System

There are different sensing mechanisms for the functioning of the eNose, viz. Optical, Mass and Ion Mobility based, Gas Chromatography based, Infrared Spectroscopy based, Chemical Sensors. Of these the Chemical sensors are the most popular and widely employed, as it is possible to tailor various parameters and due to its close resemblance to mammalian olfaction. These are again classifies as MOS, MOSFET, surface and bulk acoustic wave, and conductive polymers.

Role of Nanomaterials

The preferred choice of sensor is to employ nano-structures which offer many advantages such as low cost, compact size, low power consumption, and faster response. With the advancement in microelectromechanical systems (MEMS), nanoelectromechanical systems (NEMS) very large-scale integration (VLSI), and nanoscience various novel nanostructures are successfully being employed in the fabrication of EN devices.

Reference : Ramgir, Niranjan S. "Electronic nose based on nanomaterials: Issues, challenges, and prospects." ISRN Nanomaterials 2013 (2013).