Acoustic Waves for Gas and Liquid Phase Sensing Seminar January... · MIPs for steroids, terpenes & amino acids, SAMs for PAHs Selectivity Surface texture & hydrophobicity Wetting

Acoustic Waves for Gas and Liquid Phase Sensing

Glen McHale

School of ScienceThe Nottingham Trent University

Nottingham NG11 8NS, UK

Overview

1. Acoustic Waves• Acoustic wave modes• Principles of sensing (QCM/SAW)

2. Literature Examples• SAW for dew/frost point sensing• QCM for monolayer phase transitions

3. Our Recent Work• Steroid and particulate detection• Combined optical-SAW• Love waves and biosensing: Theory & Experiment• Super-hydrophobicity and acoustic waves

Acoustic Wave Modes

Basic Sensor DevicesQCM SAW

Rayleigh Acoustic Plate Mode

Lamb Wave (FPW)

STW

Love Wave

Delay Line Config’s ⇒

Acoustic Waves

Sensing Principles

• Create resonator or measure impedance/spectrum

QCM/SAW determines oscillation freq. v=fλ

• Mass (thin film) loadingMain effect is change in frequency

Sauerbrey equation ⇒ ∆f∝f2∆m/A

• Quartz Crystal Microbalance (QCM)Thickness shear mode oscillation

• Surface Acoustic Wave (SAW)Mechanical wave travelling along a surface (+electric field)

• Liquid Loading & Penetration DepthNeed shear mode devices

(QCM, Shear type SAWs)

Penetration depth δ=(η/πfρ)1/2

Sense mass in penetration depth

Kanazawa ⇒ ∆f∝√(ηρ) f3/2

For water δ ~ 250 nm (at 5 MHz)

• Surface Loading Alters Resonance

Mass loading reduces frequencyNon-rigid mass (e.g. polymers)

broadens resonance/creates damping

(senses shear modulus)

Devices

Quartz (IQD)Blank/ with Contacts

RS 7MHz Package

Specialist QuartzCrystal/5 MHz

50 MHZ RACAL MESL SAWTEK Package

AcousticAbsorber

Apodized IDT Offset IDTsMultistripCoupler

35 MHz Resonator

Copper Board

CentralIDT

Reflectors to create cavity

Dual delay line with one side coated

110 MHzSAW

Contact Pads

Sensing Area

170 MHz SAW Delay line

QCMs SAWs

Two Example Applicationsfrom the Literature

Atmospheric Data

• 400 MHz Saw Based Frost Point HygrometerDr Rod Jones – Cambridge, UKCycle temperature of substrate using a Peltier

– loss of SAW resonance gives frost/dew pointDeployed in a weather balloon

-120 -100 -80 -60 -40 -20 0 20 40

10

100

1000

Ascent, July 1999 from Gap Frost Point (degC)

Heat Sink Temp (degC)

Ambient Temperature (degC)

PTU unit Frost Point (degC)

Temperature (degC)

Pre

ss

ure

(h

Pa

)

-60 -50 -40 -30 -20 -10 0

200

300

400

500

Ascent, July 1999 from Gap; close up of 600 to 200 hPashows clouds recorded bythe SAW hygrometer and faster response of SAW device compared to the

PTU sonde

Frost Point (degC)

Heat Sink Temp (degC)

Ambient Temperature (degC)

PTU unit Frost Point (degC)

Temperature (degC)

Pre

ss

ure

(h

Pa

)

From PTU sonde From SAW

Cloud layers

From SAW

Cloud layer

Cloud layer

• 8 MHz QCMProf. J KrimSliding friction on gold surfaces via monolayer adsorption in UHV

Larger surface area for 80 K deposited Au gives larger frequency shift

Monolayer Phase Transitions

Krypton adsorption (77.4 K)Au film deposited at (a) 80 K (b) 300 K

(a)

Liquid to solid monolayer transition point

Nitrogen adsorption (77.4 K)Au film deposited at (a) 80 K (b) 300 K

NTU Based Acoustic Wave Research

Overview• Experimental

QCMsMIPs for steroids, terpenes & amino acids, SAMs for PAHs

Selectivity

Surface texture & hydrophobicity Wetting

SAWsElectrostatic precipitation of atmospheric particulatesSpreading oils and Rayleigh-SAWs Instrumentation

Love waves for biosensingMultiple modes and layer-guided SH-APMs Sensitivity

• TheoreticalAcoustic wave response to multiple viscoelastic layersInterfacial slip and interfacial layers of waterHydrophobic effects

Two of Our Applications

Molecularly Imprinted Polymers

• Target Applications (Liquid Phase)Recognition/selectivity via molecularly imprinted polymers (MIPs)Applications: monoterpenes, amino acids, topical steroidsTailor made enantioseparation materials

Acoustic Wave Sensor

Recognition element (MIP)

• MIP - Polymer Type Artificial ReceptorEmil Fisher’s ‘Lock and Key’(enzyme analogy)

Specific to the target analytein terms of their spatial and electronic environment

0

5

10

15

20

25

30

35

0 0.5 1

concentration / ppm

Fre

quen

cy D

ecre

ase

/ Hz

Nandrolone

Testosterone

Epitestosterone

Stanazolol

Selectivity to Nandrolone

• QCM CoatingSpin coated/cast layerCovalent imprinting strategy

Polymer 1 - ImprintedPolymer 2 - Non-Imprinted

0

5

10

15

20

25

30

35

0 0.2 0.4 0.6 0.8 1

concentration (ppm)

∆f (

Hz)

• Response to ReplicatesOne-shot screeningTest data for 5 crystals

EP-SAW for Atmospheric Particulates

• System DesignAir sampled via filterParticles ionised by N2

+

Particles collected onto pathof biased metallised SAWi.e. Electrostatic precipitation

• Electrostatic PrecipitationCharged particles deposited on a collector plateEstablished principle for atmospherically borne microorganisms High (99-100%) efficiency

Particulate Response with Bias

• Test Device ConfigurationLiNbO3 - Rayleigh-SAW, λ ~ 45 µm86 MHz & 253 MHzTest particulates via a mono-disperse ~ (2.0±0.1) µm NaClaerosol

-66

-61

-56

-51

-46

-41

0 10 20 30 40

Time / mins

Ph

aseo

Bias induced precipitation

Vbias~100 V

Not requiredfor test

Test particulates

• Preliminary ResultsVoltage of plate increasedto > 120 V in 20 V steps

⇒ Phase changes

Our Historical Development

Dynamic Wetting and SAWs

Concept of the Experiment Schematic of Experiment

SAW AttenuationInterferometry

SAW propagation direction

SAW Reflection

01

23

45

hêêêêdddd0

2

46

810

wtwtwtwt

----0.0250

0.0250.05

----DwDwDwDwêêêêwwww

01

23

45

hêêêêdddd

Viscoelastic Layer on QCM/SAW - Theory

Frequency Shift

Increasing depth Liquid

Solid

Biological Mass and Vesicle Deposition

OH OH OH OH

rough hydroplilic surface

+ vesiclesOH OH OH OH

supported vesicle layer

Bilayer Vesicle layer

Monolayer

S

OH

S

OH

S

OH

S

OH

S

OH

S

OH

S

OH

S

OH

S

OH

S

OH

S

OH

S

OH

S

CH3

S

CH3

S

CH3

S

CH3

S

CH3

S

CH3

Vesicle • Concept

Vesicle deposition to givebilayers and monolayers

• ExperimentFlow through systemWater, buffer solution, vesicle deposition (POPC),detergent

Vesicle Deposition on Love Wave Devices

• Love Wave Devices110 MHz (+ 330 Harmonic)Pulse (and CW) modeFlow cell usedIL and phase measured

• Experimental SequenceWaterBuffer solution (PBS)Vesicle deposition (POPC)Detergent

Repeat

Multiple Love Wave Modes

• SpectraThick guiding layersPhotoresist layersQuartz substrate (SSBW)

• Experimental ResultsPoints = results for devices110/330 and 309 MHzLines = theory

-90-80-70-60-50-40-30-20

95 100 105 110 115 120

Frequency/MHz

Inse

rtio

n L

oss

/dB

Initial increase

Laterdecrease

0 0.5 1 1.5 2 2.5 3 3.5dêêêêlllll

4200

4400

4600

4800

5000

5200

esah

Pd

ee

pS

Love Waves v SH-APMs

• Surface Acoustic Wave (SAW)

• Love WaveLayer guided SH-SAW

with vl < vs

• SH-APMSubstrate resonance

Layer-Guided SH-APMs

0 0.2 0.4 0.6 0.8 1 1.2 1.4dêêêêlllll

250

500

750

1000

1250

1500

1750

2000

ytivitis

ne

S,»» »»S

m»» »»m

2gk-- --

1

0 0.2 0.4 0.6 0.8 1 1.2 1.4dêêêêlllll

1000

2000

3000

4000

5000

6000

7000

8000

esah

Pd

ee

pS

,vm

s-- --1

v=vs

v=vl

APM’s

LoveWaves

• Theoretical DispersionLove waves for v<vs

SH-APMs for v>vs

Enhanced sensitivity

Sensitivity ∝ slope

Love Wave Sensitivity SH-APM Sensitivity

0 0.2 0.4 0.6 0.8 1 1.2 1.4dêêêêlllll

50

100

150

200

250

300

350

400

ytivitis

ne

S, »» »»

S m»» »»m

2gk-- --

1

Experimental Results for SH-APMs

• IDT Face CoatedLove wave and SH-APMboth sensitivive

• Opposing Face to IDTsSH-APM changesLove wave insensitive

25

35

45

55

65

0 0.3 0.6 0.9 1.2 1.5z

f (M

Hz)

25

30

35

40

45

50

55

60

65

0 0.3 0.6 0.9 1.2 1.5z

f (M

Hz)

Rough/Structured Surfaces & Hydrophobicity

Lithographic Surface SEM Images

0

20

40

60

80

100

120

140

160

180

35 45 55 65 75 85 95 105 115 125 135 145

Contact angle on smooth surfaceo

Co

nta

ct a

ng

le o

n r

ou

gh

su

rfac

eo Roughness (r=5)

Penetration (f=0.7, g=0.3)

Saturation

Complete wetting

"Film formation"

Saturation

Completenon-wetting

"Planar roll-up"

Am

plifi

catio

n

Super-Hydrophobicity

• Contact AngleSide view imagesIdentical chemical functionalityDifferent topography

• Effect on QCM?Response in air

versus response in water

4.938

4.940

4.942

4.944

4.946

4.948

0 50 100 150 200

Time / s

Freq

uenc

y / M

Hz

_

air

water

Anomaly or not?

Acoustic Waves are

• Highly sensitive to interfacial properties• Operate in-situ in gas/liquid phase• Understood for

Uniform mass filmsSimple liquidsUniform viscoelastic films

Summary

The End

Acoustic Waves are notIntrinsically species selectiveUnderstood for many situations

AcknowledgementsCollaborators at Nottingham Trent

Academics PDRAs/PhDs

Dr Mike Newton Dr Fabrice Martin All experimentalDr Carl Percival Dr Simon Stanley QCM/MIPs & SAWs for particulatesProf. Krylov Dr John Cowen SAWs and wetting (Now at L’boro)Mr Mike Rowan Dr Markus Banerjee SAWs and wettingDr Alan Braithwaite MIPsDr Carole Perry Dr Neil Shirtcliffe Superhydrophobic surfaces

Ms Sanaa Aqil + Mr Edward Harding (Student)

External Collaborators

Dr Electra Gizeli/Dr Kathryn Melzak Institute of Biotechnology, Cambridge UniversityDr Ralf Lücklum/Prof. Peter Hauptmann IPE, Magdeburg, GermanyDr Wayne Hayes Reading University, UKProf. Yildirim Erbil Istanbul, TurkeyDr Brendan Carroll Unilever plc

Funding Bodies

EPSRC GR/L82090, GR/R36718 , GR/R01284 BBSRC 301/E11140The Royal Society-DAAD, Nuffield Foundation, The British Council-TUBITAK/EU COSTEPSRC for funding and Dr Cernosek an Dr Casalnuovo for hosting this visit

Acoustic Waves - Comparisons

Mode Rel. Sens. Complexity Robustness Gas/LiquidQCM Low Low/Xtal Med g+l

SAW High Med/metal on Xtal High g

Love High Med/film+metal+Xtal High g+lSTW High Med/metal on Xtal High g+l

Lamb High High/membrane Low g+l

APM Med Med/metal on Xtal Med g+l

• Types of WaveThickness shear mode

Quartz crystal microbalance (QCM)Surface Acoustic Waves (SAWs)

Rayleigh waves, Love waves, Surface transverse waves(STWs), Lamb waves/Flexural plate waves (FPWs)

Acoustic Plate ModesShear horizontally polarised SAWs (SH-SAWs)Surface skimming bulk waves (SSBWs)

Acoustic Waves Devices - Parameters • QCM v SAW

QCM Simple, off-the-shelf, 5 to10 MH, fragileSAWs Flexibility by design, MHz to GHz, robust

• Basic CharacteristicsHigher frequencies Higher sensitivity

Smaller λ, smaller devices

• Typical SAW ParametersFrequency and wavelength MHz → GHz 400 µm → 4 µmRapid response in-situ and better than 10 HzSensitive 13 Hz per ng cm-2 at 100 MHzSize, mass and cost mm/cm, low and < $1Power consumption lowTemp. stability depends on crystal cut

• Problems?Selectivity and reproducibility poor and depends on coating

01

23

45

hêêêêdddd0

2

4

6

810

wtwtwtwt

00.050.1

0.150.2

----L

01

23

45

hêêêêdddd

Viscoelastic Layer on QCM/SAW - Theory

Insertion Loss

Increasing depth Liquid

Solid

MIPs as Recognition Elements

• Non-Covalent Approach

Self-assemble functional monomers around template molecule

Add cross-linker and ‘fix’ assembly by polymerisation

Remove non-covalently bound template via solvent

Self-assembly

Template cleavage

Polymerisationto fix cavityAnalyte

rebinding

Analyte

Functional monomers

Analyte : monomer complex

Imprinted cavity

MIPs as Recognition Elements

• Covalent Approach

Convert template into a polymerisable derivative

Co-polymerise with a cross-linker

Resin covalently incorporates the template

Synthesis of polymerisable

template

Chemical

cleavage

Polymerisationto fix cavityAnalyte

rebinding

Analyte

Functional monomers

Polymerisablederivative of analyte

Imprinted cavity

Nandrolone Nandrolone chloroformate Nandrolone 4vinyl phenyl carbonate

Phosgene, N2 4-vinylphenol

Polymerisation Template cleavage

Synthesis of Nandrolone MIP

• Covalent Approach (Scheme 1)

Gives non-covalent recognition sites

Selectivity Between Steroids

• Future Extension of Scheme 1

Can be applied to any steroid containing an OH moiety

O H

O

O H

O

H N

N

H O

Testosterone Epitestosterone Stanazolol

• Selectivity between Stereoisomers

Stereoisomers testosterone and epitestosterone

preliminary work shows can distinguish them

Natural ratio is 1.5:1 steroid abuse disturbs this ratio

• Steroids of Interest