Odour detection
Bruce Warburton
Landcare Research, Lincoln
Odour Detectors
• Biological:
– Dogs
– Rats
– Bees
• Electronic:
– E-noses
– RFID tags
Bees…1
Bees…2
Bees…3
Sensitivity and Specificity
•
Bees
E-noses…1
Biological System
Electronic Nose
Respiratory system
Nose - Diaphragm
Pump and valves
Sampling system
Olfactory Membranes
Receptor Proteins
Sensors
Many types
Olfactory Area of the
Brain (Signal Processing)
Computer and
Software
Algorithims,
Neural Networks,
Statistical Analysis
Output = Recognition
of smell / discrimination
Output =
Discrimination
and recognition
E-noses…2
Conducting Polymer Sensors.
Sensor
Gold electrode
pair
Gap in electrode
Sensor
material
-
Silicon substrate
The resistance of the polymer material deposited on the
electrode changes when volatile chemicals interact with the surface.
E-noses…3
Bloodhound ST214
Flow injection system (pulse or
sniff of volatiles to give transient
response)
Constant flow rate
Reference gas, cleaned air
Automatic system check to a
control substance (usually aqueous
butanol)
Typical sampling time 1-3 minutes
including wash and baseline steps.
14 Conducting polymer sensors
Lightweight (<2.5Kg)
Windows-based software
Detection of Mycobacterium volatiles
Blank Medium
M. avium
M. scrofulaceum
M. tuberculosis
P. aeruginosa
0.4
0.3
0.2
S2 (2%)
0.1
0
-1.2
-1
-0.8
-0.6
-0.4
-0.2
0
0.2
0.4
0.6
0.8
-0.1
-0.2
-0.3
S1 (97%)
Volatiles associated with TB: methyl phenylacetate, methyl p-anisate,
methyl nicotinate
1
Second Generation E-noses
Miniaturisation to produce
portable instruments is also will
possible.
RFID odour sensors…1
A
B
Zre
Sensing film
Fp
Zp
IC chip
Zim
F1
Antenna
Z1
Z2
F2
Frequency
C
D
Specific VOCs change the impedance of the RFID sensor antenna
RFID odour sensors…2
• Can use passive and
active RFID tags
• Low-power
requirements
• Large-scale
production
• Lend themselves to
Wireless Sensor
Networks
• E.g. Can detect rabbit
Hexanal, Nonaldehyde
& Octenol