Ultra-Sensitive Microsensors for Chemical Analysis, pumpsandpipesmdhc

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Alan Schilowitz, Andy Riley, Dalia Yablon, Mark DiskoExxonMobil Research and Engineering Co.

Corporate Strategic Research Laboratory

Annandale, New Jersey

Ultra-Sensitive Microsensors for Chemical Analysis

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Why Microsensors ?

• High sensitivity

• Low power consumption– Enables wireless– Improved safety

• Redundancy– Potential for large number of parallel sensors

• Portability– Personal monitoring (e.g. badges)

• Small sample size

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How Many Cantilevers Can Fit on the Head of a Pin ?

2 mm

• Two Modes of Operation

– Dynamic

– Static

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Micro-Cantilevers Background

• Extension of Atomic Force Microscopy- Some experiments carried out in Atomic Force Microscope head- Ultrahigh sensitivity to mass change

• Use for chemical measurement pioneered by Thundat (ORNL) and Gerber (IBM Zurich)

• Applied to analysis of gas and aqueous solutions

• Cantilevers commercially available in variety of shapes and materials- Range of resonant frequencies, spring constants, shapes

Focusing Lens

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• Dynamic Mode – Increasing viscosity changes resonance spectrum– Ultra sensitive to mass changes

• Cantilevers can be driven with piezo-electric crystal

• Mass build-up changes resonant frequency − Viscosity change alters resonant frequency and width of spectrum

0 2000 4000 6000 8000 10000 12000Frequency (Hz)

Am

pli

tud

e

Air

Increasing Viscosity

Analysis in Dynamic Mode

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Cantilevers Respond to Viscous Damping

Viscosity = 5.238 Q-1.88

R2 = 0.9971

0

1

2

3

4

0 1 2 3 4 5

Q

Vis

co

sit

y (

cP

)Frequency

Am

pli

tud

e

Frequency

Am

pli

tud

e

High Q Low Q

Increasing Viscosity

• Viscosity can also be measured by frequency change– Less sensitive than Q

• Measurements can be made on micro liter samples

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Chemical Analysis in Static Mode

• Detection limit is in sub picogram range

Selective adsorbant on one side only

-50

0

50

100

150

200

250

200 300 400

Time (minutes)C

anti

leve

r D

efle

ctio

n (

nm

)

UntreatedCantilever

Gold Coated Cantilever Detects Mercaptans

Mercaptan Injection

• Static Mode - coated cantilevers respond to adsorption- Detect deflection of cantilevers coated on one side

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Functionalized Cantilever Arrays for Aromatics Detection

Self-Assembled Monolayer

Candidates:

SH

Benzyl Mercaptan

SH

Naphthalenethiol

SH

OH

Mercaptohexanol

SH

( )6

Octadecanethiol

Self-Assembled Monolayers Impart Chemical Selectivity to Highly Sensitive Cantilever Transducers

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S

OH

S

S

( )6

S

Cantilever Response To Aromatic Vapor

• Cantilevers exposed to aromatic vapor (parts per thousand) in laboratory air

• Treated cantilevers have unique response to aromatics

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-25

-15

-5

5

15

0 200 400 600 800 1000 1200Time (s)

Def

lect

ion

(nm

)

-35

-30

-25

-20

-15

-10

-5

0

5

10

15

0 200 400 600 800 1000 1200 1400 1600

Time (s)

Def

lect

ion

(nm

)

-35

-25

-15

-5

5

15

450 950 1450 1950

Time

Def

lect

ion

(nm

)

-35

-25

-15

-5

5

15

0 500 1000 1500Time (s)

Def

lect

ion

(nm

) toluene xylene

toluene xylene

d. ODT - octadecanethiol

c. MH - mercaptohexanol

b. NT - naphthalenethiola. BM – benzyl mercaptan

toluene xylenetoluene xylene

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Summary

• Micro-Cantilever sensor applications

– Viscosity on micro-liter samples– Potential for sub picogram chemical sensitivity

• Chemical specificity with Self Assembled Monolayers (SAM)

• Potential for applications where:– Sample size is limited– Large scale redundancy is desirable– Low power consumption is necessary

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Medical Applications

Light traces are before exposure to e-coliDark traces are after exposure

mk /

B. Illic et.al., Appl. Phys. Lett. 77(3), 450 (2000)

W. Guanghua et.al., Nature Biotechnology 19, 856 (2001)

Prostate Specific Antigen (PSA) Sensor

E-Coli Sensor

• Vibrational frequency reduced as cells bind to cantilever

– Frequency =

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References - Medical Applications

Rapid and label-free nanomechanical detection of biomarker transcripts in human RNA Zhang, J.; Lang, HP.; Huber, F.; Bietsch, A.; Grange, W.; Certa, U.; McKendry, R.; Guntherodt, HJ.; Hegner, M. & Gerber, Ch.  Nature Nanotechnology, 1, 214-220 (2006).

Novel electrical detection of label-free disease marker proteins using piezoresistive self-sensing micro-cantileversWee KW, Kang GY, Park J, Kang JY, Yoon DS, Park JH, Kim TSBiosens Bioelectron 2005 Apr 15;20(10):1932-8

Array of Nano Cantilevers as a Bio Assay for Cancer DiagnosisKlein, K.M.; Jiantao Zheng; Gewirtz, A.; Sarma, D.S.; Rajalakshmi, S.; Sitaraman, K.Electronic Components and Technology Conference, 2005. Proceedings. 55thVolume , Issue , 31 May-3 June 2005 Page(s): 583 - 587

A Review of Microcantilevers for Sensing ApplicationsVashist, S.K., June 2007www.azonano.com/details.asp?ArticleID=1927