acoustic waves for gas and liquid phase sensing seminar january... · mips for steroids, terpenes...
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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
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