CSIR-Central Glass & Ceramic Research Institute
A Unit of Council of Scientific and Industrial Research

सीएसआईआर-केंद्रीय काँच एवं सिरामिक अनुसंधान संस्थान
वैज्ञानिक और औद्योगिक अनुसंधान परिषद की एक इकाई
(An ISO 9001:2015 Certified Institute)
Participating Institutes - JU  

Development of QCM Sensors for tea aroma classification using E-Nose.
The objective is to develop Quartz crystal microbalance (QCM) sensor array for tea aroma classification. Commercially available MOS sensors have limited selectivity towards volatiles in tea and need high temperature of operation. To overcome these problems, QCM based electronic nose has been proposed. QCM sensors can be easily fabricated, have less response time and can be coated with a variety of materials to obtain different sensitivities and selectivity.

  Deliverables/Outcome of the project is:
  • Sensor array for E-Nose using QCM Sensors for quality testing of black tea.
  • QCM Sensors for quality evaluation of basmati rice and other agro products.
  • Hybrid sensor array comprising of MOS and QCM Sensors in electronic nose.

  Development Methodology:
QCM sensors are based on chemical or physical interaction of substances with the coating material and the combined mass increase. A QCM sensor consists of a quartz crystal, coated with an analyte-sensitive polymer or a metal oxide. The volatile compounds are adsorbed on contact onto the surface of polymer/ metal oxide, increasing the mass of the QCM sensor and hence resulting in a change in resonant frequency. A QCM sensor coated with a given material is multi-specific, i.e. it responds to multiple analytes, hence QCM-based electronic nose systems make use of an array of sensors, each using a distinct sensor coating.

Suitable adsorbent materials, selected after an extensive literature survey, are converted into solutions with appropriate solvents. These are then loaded on an electrostatic spray system and deposited on the quartz crystal blanks.

Coating materials used:
  • Polythelene glycol
  • D-Glucose
  • Ethyl cellulose
  • Adenine
  • Phenylalanine
A coated QCM sensor is shown in fig. 1

Fig. 1: A coated QCM sensor.

The measuring setup is shown in fig. 2

Fig. 2: Schematic of experimental setup

The snapshots of odour delivery setup and QCM sensors are presented in fig. 3:

Fig. 3: (a) The odour delivery setup                         (b) The QCM sensors in sensor chamber

In an experiment with two orthodox varieties and two CTC varieties, the aroma sensing using five sensors were carried out. It was observed that the sensors were able to distinguish among four types of tea. The response of a polythelene-glycol (PEG) coated sensor is presented in fig. 4.

  1. Sensor development and characterization with pure standard gases.
  2. Improvement of electrostatic spray setup.
  3. Data collection using developed sensors for tea aroma.
  4. Data analysis with collected observations.

    Updated on: 05-04-2016 15:15 
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