No Slide Title Folliate Filiform Fungiform Taste bud (c) Taste bud (b) Fungiform papilla (a) Tongue...

IEE Seminar on MEMS Sensor Technologies, 25 April 2005 1/24

Electronic TonguesJulian W. Gardner

Professor of Electronic EngineeringUniversity of Warwick


Acknowledgements

• Dr Marina Cole (e-tongue) • Dr James Covington (e-nose & MSL)• Research Students at Warwick• Universities of PennState & Georgia Tech (USA)• Royal Academy of Engineering - Global Award• Royal Society and Wolfson Foundation


Overview

• Research at Warwick on Biomimetic Devices• Concept of artificial tongue• 60 MHz dual delay-line miniature system• Discrimination of basic human tastes • Detection of bacterial loading in milk• 433 MHz based microsystem with filter• Artificial nose & tongue system


Biomimetic devices: Warwick Electronic Nose

• Device to mimic human olfactory system

• 1-100 million olfactory receptor cells• 300 genes that encode olfactory

binding proteins• 1,000s glomeruli nodes• Mitral/tufted cells• 1-2% genome coding!

• E-nose concept 1980s• First companies created

in 1990s

• Emerging market valued in 2003 at €10-20 M

• Potential market €1.2B


Commercial E-nose Instruments from Warwick University

Input(Odour)

Output(Predictor)

Olfactory epithelium (Receptor cells)

Mammalian Nose Olfactory bulb

Brain(Olfactory cortex)

Electronic Nose Sensor array Analogue to Digital

Converter

Computer ( Signal Processor & Pattern Recognition Engine)

SENSOR 1

SENSOR 2

SENSOR 3

SENSOR n

ARRAYPROCESSOR

PARCENGINE

KNOWLEDGE BASE

SENSORPROCESSOR

SENSORPROCESSOR

SENSORPROCESSOR

SENSORPROCESSOR

TRAIN TEST

ANALOGUE SENSING DIGITAL PROCESSING

V1j(t)

V2j(t)

V3j(t)

Vnj(t)

X1j

X2j

X3j

Xnj

Xj

Sensor-based e-nose


Screening for pathogens

Medical diagnosis of ENT infections


Bacterial Population Genetics

Streptococcus pyogenes


Screening for strainEnvironmental biohazards

Toxic strain of Microcystis aeruginosa

-0.5

-0.4

-0.3

-0.2

-0.1

0

0.1

0.2

0.3

0.4

0.5

-1 -0.5 0 0.5 1

Second Principal Component

Third

Prin

cipa

l Com

pone

nt

PCC 7806PCC 7941


Gustation

(d) Taste cell

H+

H+ Na+

Na+

Salt Sour Sweet Bitter

(e) Receptor cells on tip of taste cell

Nerve fibres

Taste pore

Taste cell

Circumvilliate

Folliate

Filiform

Fungiform

Taste bud

(c) Taste bud

(b) Fungiform papilla

(a) Tongue


Warwick Electronic Tongue

• Mimic human sense of gustation

Piezoelectric wafer 36YX.LT

Shorted delay line

Output IDTs

Input IDTs

Aperture

Finger width λ/4 Periodicity λ

Free delay line Liquid

Free area

SH-SAW propagation

• Concept in late 1990s• Warwick SAW based design – 60 MHz

• No companies yet

20

200

22

)()/())(()/(

2 TPr

TPrrrsK

vv

εεεωσεεεεεεωσ

+′+′

+′−′+′−≈

∆

20

20

2

)()/())(/(

2 TPr

TPrsK

k εεεωσεεεωσα+′+′

+′≈

∆

PCB with SH-SAW device SMB RF Connector

PTFE Liquid cell

Guiding pin

Liquid reservoir

10 mm


Smart Tongue ApplicationsTaste discrimination

-1

-0.5

0

0.5

1

-3 -2 -1 0 1 2 3 4

Full Milk Semi-skimmed Skimmed milk

PC 2

PC 1

PC 1

PC

2

-2

-1.5

-1

-0.5

0

0.5

1

1.5

2

-3 -2 -1 0 1 2 3 4

Day 1

Day 4

Day 5

Day 3

Day 2

DI water

Sweet

Bitter

Sour

Salt

Fat content in Milk

Milk freshness/bacterial load


Dilution Tests• Experiments

performed with the original solutions diluted in steps by a factor of 2n

• Volume of DI water was increased by 2n

and added to fixed volume of solution

• As the concentration of the solutions decreased the results tended towards that of the DI water

• Typical limit of detection of 0.1% or 1 part in 103

Component 1

Com

pone

nt 2

Sour

Salt

Bitter

Sweet

Water

3

2

1

0

-1

-2

-3-3 -2 -1 0 1 2 3 4 5 6


Drivers for 3-D Microsystems• Need to miniaturise e-noses and e-tongues

• Need to reduce cost and power consumption

• Need to penetrate mass market

• CMOS sensor array chips developed but need for integrated 3-D microfluidic packages


Design of 433 MHz Electronic Tongue

5 mm


Wireless MEMS Tongue System

2.4 µm 9.6 µm 2.4 µm

Reflectors at different distances from IDTs

Metallised reflective delay line

Free reflective delay line

Transmitting IDTs connected to loop antenna

Device antenna Response Request

Interrogation unit

RF LINK


Design of Micro-concentratorfor Bacterial Screening


Making 3-D Microfluidic Packages• Direct writing of 3D

structures in resins• Developed in 1993• Pioneered in US and

Japan• Capability from 50

microns to 50 nm


Warwick 3-D Microsculpting Lab for Biomimetic Devices

• SRIF2 Funding from HEFCE £200k

• Royal Society WolfsonFoundation Award £200k

• Installed 2 EnvisionTec units of 25 micron resolution

• Electroplater for 3-D micro-antenna

• Custom submicron unit from PSU


3-D Fluidic Micro-packages

• Disposable microfluidic packages for e-tongue

5 mm

Designed by Warwick made at GIT, USA


Total Tongue System

Signal generator Vector voltmeterComputer

Flow

con

trol

elec

troni

cs P

CB

GPIB SH-SAW sensor and liquid cell

Sample liquids DI water

Pump

Valves Flowmeter

IEEE Port

Temperature controlled chamber

Waste


Taste Discrimination at 433 MHz


Combined Nose-Tongue System

-4 -3 -2 -1 0 1 2 3 4 5 -2

-1

0

1

2

0

1

2

WaterWaterWaterWaterW ate rSweetSweetSweetSweetSweet

SaltySalty

SaltySaltySalty

BitterBitterBitterBitter

Bitter

Et her yEtheryEtheryEtheryEthery

EsteryEstery

Estery

Estery

Estery

Component 1 Component 2

Com

pone

nt 3

Solution Concentration Vapourpressure

E-Tongue

E-Nose

NaCl (0.1M) 0.1 M Very low

Sucrose (0.1M) 0.1 M Very low

Quinine 1 mg/mL Very low

Ethanol (ethereal) 1000 ppm High

Ethyl acetate (estery) 1000 ppm High

Ref: G. Sehra, PhD thesis, Warwick University, 2004


Conclusions

• Dual delay based electronic tongues show promise in some screening applications

• High frequency, low cost MEMS devices feasible• Combined e-nose/e-tongue can add

discriminating power

• Biological coatings may be added for even greater specificity/sensitivity


Recent PublicationsJournal Papers Cole M, Sehra G, Gardner JW and Varadan VK, Development of smart tongue devices for measurement of liquid properties, IEEE Sensors Journal, Vol. 4, No. 5, (2004), pp. 543-550.Sehra G, Cole M, and Gardner JW, Miniature tasting system based on dual SH-SAW sensor device: an electronic tongue, Sensors and Actuators B, 103, (2004), pp. 233-239.

Conference PapersM. Cole, G. Sehra, J.W. Gardner and V.K. Varadan, Fabrication and Testing of a Smart Tongue Device for Liquid sensing, Proc. of IEEE Sensors 2002 Conference, June 12-14, 2002, Orlando, Florida, USA, pp. 237-241.Sehra G S, Covington JA, Cole MV, and Gardner JW Combined electronic nose/tongue for liquid analysis, Proc. of 9th International Symposium on Olfaction and Electronic Nose, eds A d’Amico and C di Natale, 29 September –2 October 2002, Rome, Italy, pp. 58-63.Sehra G, Cole M and Gardner JW, Miniature taste sensing system based on dual SAW sensor device, Proc. of 17th European Conference on Solid State Transducers EurosensorsXVII, 21-24 September 2003. Guimaraes, Portugal.I.I. Leonte, M.S. Hunt, G. Sehra, M. Cole, J.W. Gardner, M. Noh and P.J. Hesketh, A wireless microsystem for liquid analysis, Proc. of IEEE Sensors 2004 Conference, October 24-27, 2004, Vienna, Austria.I. Leonte, M. Hunt, G. Sehra, M. Cole and J. W. Gardner, SAW bio-liquid sensors with RF interrogation, Proc. Of IEEE High Frequency Postgraduate Students Colloquium, IEEE catalog no. 04TH8740, 6th and 7th September, 2004 UMIST Manchester, UK, pp. 47-52.

No Slide Title Folliate Filiform Fungiform Taste bud (c) Taste bud (b) Fungiform papilla (a) Tongue...

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