Electronic Nose (E-Nose) Technology Explained

This article explains electronic nose (e-nose) technology, including different types of electronic nose sensors, a comparison between biological and electronic noses, and applications of e-noses.

An electronic nose (or e-nose) is an electronic device that identifies the odor of specific components and analyzes their chemical composition. It’s called an “electronic nose” because its functionality is similar to that of a biological nose.

The block diagram below illustrates the components of an electronic nose:

The e-nose consists of three main parts:

• Sample Delivery System: Delivers the air sample to the sensors.
• Detection System: The array of sensors that detect the volatile compounds.
• Computing System: Processes and analyzes the signals from the sensors.

Let’s walk through how an electronic nose works:

• Step 1: A pump draws an air sample into a small chamber through a tube. This chamber houses an array of electronic sensors.
• Volatile organic compounds within the sample interact with the active material on the surface of the sensors. This interaction generates a transient response.
• After a short period, a steady-state response is achieved. This response is then sent to a Signal Processing Unit.
• A washing gas (such as alcohol vapor) is applied to the sensor array for approximately one minute. This step removes the odorant mixture from the sensor’s surface and active material.
• Finally, a reference gas is introduced to the array, preparing it for the next measurement.

Electronic nose device model Cyranose 320 from Sensigent California, USA. (Image from Wikimedia Commons)

For further information, contact sales@sensigent.com or visit <www.sensigent.com>

Electronic Nose Sensors

Here are some of the most commonly used types of electronic nose sensors:

• Piezoelectric Sensor: The absorption of gas molecules on the polymer surface leads to changes in mass. These mass changes affect the resonant frequency of the crystal, which is directly proportional to the concentration of the target material.
• Conductivity Sensor: The absorption of gas molecules causes changes in the conductivity of the sensor. This change in conductivity is proportional to the total volatile organic compounds absorbed.
• SAW Sensor: This type of sensor relies on the modulation of Surface Acoustic Waves (SAW) to detect physical phenomena.

Biological Nose vs. Electronic Nose

The following table compares the key features of a biological nose with those of an electronic nose:

Applications of Electronic Nose

Electronic noses have a wide variety of applications, including:

• Medical Diagnosis and Health Monitoring: Examples include the diagnosis of respiratory diseases, cancer detection, and identification of urinary tract infections.
• Environmental Monitoring: Useful for detecting oil leaks, testing groundwater, monitoring household odors, and assessing air quality.
• Food Industry: Used for analyzing fruit ripening processes, and more.