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 Pump and valves

Nose - Diaphragm Sampling system

Olfactory Membranes Sensors

Receptor Proteins Many types

Olfactory Area of the Computer and

Brain (Signal Processing) Software

Algorithims,

Neural Networks,

Statistical Analysis

Output = Recognition Output =

of smell / discrimination Discrimination

and recognition

E-noses…2

Conducting Polymer Sensors.

Gold electrode

pair

Sensor

material

Silicon substrate Gap in electrode

Sensor

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

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

-1.2 -1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1

S1 (97%)

S2

(2

%)

Blank Medium M. avium M. scrofulaceum M. tuberculosis P. aeruginosa

Detection of Mycobacterium volatiles

Volatiles associated with TB: methyl phenylacetate, methyl p-anisate,

methyl nicotinate

Miniaturisation to produce

portable instruments is also will

possible.

Second Generation E-noses

RFID odour sensors…1

Zre

Zim

Zp

Z2

Fp

FrequencyFrequency

F1

Z1

F2

Zre

Zim

Zp

Z2

Fp

FrequencyFrequency

F1

Z1

Sensing film

Antenna

IC chip

A B

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