OTTER

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OTTERAquaFlux

• Perry Xiao
• London South Bank University
• Photophysics Research Centre
• Biox Systems Ltd
• University Spin-out Company

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Plan
1. OTTER Fundamentals 2. OTTER SC
Hydration 3. AquaFlux Fundamentals 4. AquaFlux
Applications
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OTTER Overview
(Opto-Thermal Transient Emission Radiometry)
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OTTER The Spectroscopic Dimension
OTTER Selectivity- 1. Excitation 2. Thermal
Emission Wavelength determines- 1. Absorbing
Species 2. Penetration Depth
OTTER requires STRONG Absorption !
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OTTER Fixed Fibre Optics
Fixed Optics Fingers, Hands Volar
Forearm Mobile Measurement Head Any skin site
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Plan
1. OTTER Fundamentals 2. OTTER SC
Hydration 3. AquaFlux Fundamentals 4. AquaFlux
Applications
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OTTER Hydration Measurement
Excitation _at_ 2.94µm- H2O Penetration
0.8µm Emission _at_ 13µm- H2O Penetration 3.3µm
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OTTER Signal Analysis 1
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OTTER Signal Analysis 2
Mean SC Hydration Model
SC Hydration Gradient Model
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Example 1 Mean SC Hydration
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Example 2 SC Hydration Gradient
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Example 2 SC Hydration Gradient
Remove the time dimension by correlating Surface
Hydration with Hydration Gradient.
This analysis provides a measure of SC water
holding capacity
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Example 3 3D Hydration Mapping
Volar forearm/wrist area.
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Summary of OTTER Capabilities

• SC Hydration Depth Profiling
• SC Water-holding Binding Energy Measurement
• SC Thickness Swelling Measurement
• SC Renewal Time Measurement
• Epidermis Pigment Depth Profiling
• Epidermis Thickness Measurement
• Trans-dermal Diffusion Measurement
• Sunscreen Persistence Measurement

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Why OTTER ?

• Non-contacting
• In-vivo In-vitro capability
• Colour-blind
• Surface Sensitive (10 - 50 µm)
• Depth Profiling (surface-referenced)
• Small probed diameter (1 mm, down to 20 µm)
• Spectral Selectivity (excitation emission)
• Arbitrary sample (no preparation required)
• Quick (30 sec/point)
• Imaging Capability (slow)

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OTTER vs Confocal Raman
Contact artefacts affect 5µm of SC Not
colour-blind Interference from fluorescence
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Plan
1. OTTER Fundamentals 2. OTTER SC
Hydration 3. AquaFlux Fundamentals 4. AquaFlux
Applications
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Condenser Chamber Method
(Water vapour flux density measurement)
Closed-Chamber Shields from ambient air
movements. Condenser Removes water
vapour. Controls the microclimate. Single RHT
Sensor Improves accuracy sensitivity.
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Measurement Head Design

• Protects measurements from ambient disturbance
• Maintains a consistent microclimate
• Protects sensor from contamination by hair etc
• Does not distort with contact pressure
• Insensitive to heating by skin
• Can use purpose-designed measurement caps
• Rugged

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Water Vapour Distribution Within the Chamber
Skin
Condenser
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Temperature Distribution Within the Chamber
Skin
Condenser
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Chamber Microclimate
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AquaFlux the TEWL Guidelines

• The following recommendation remains valid-
• Acclimatisation - you cannot take the bio out
  of bioengineering!
• The following recommendations are not relevant-
• Air movement - no effect
• Instrument handling - no effect
• Probe heating by skin - no effect
• Contact pressure - no effect
• Pause between measurements - no need, you can
  site-hop
• Measuring surface orientation - minimal effect
  with correct probe orientation

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Droplet Method of Calibration
Simple procedure - just add water Traceable to
fundamental measures through research with
NPL Calibration brings Tewameter AquaFlux
measurements closer together
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Plan
1. OTTER Fundamentals 2. OTTER SC
Hydration 3. AquaFlux Fundamentals 4. AquaFlux
Applications
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Example 1 AquaFlux vs DermaLab
DermaLab Signals 1
AquaFlux Signals
Measurement speed is comparable, but the
fluctuations are much lower in condenser-chamber
signals.
1 GL Grove, MJ Grove C Zerweck E Pierce
Computerized Evaporimetry using the DermaLab TEWL
Probe. Skin Res. Technol. 5, 9-13, 1999.
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Example 2 Repeatability
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Example 3a Occlusion Recovery
Skin Surface Water Loss
Final TEWL 9.3 0.2 g m-2 h-1
Occlusion effectiveness 17.0 1.6
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Example 3b Occlusion Recovery
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Example 4 DermarollerTM
DermarollerTM on Volar Forearm Cylinder diameter
20mm Cylinder length 20mm No. of microneedles
192 Microneedle length 130µm Microneedle tip
diameter 1-5µm Hole depth in SC 130µm Hole
diameter in SC 70µm Hole density 250/cm2
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Example 5 In-vivo Fingernails
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Example 6a In-vitro Nail Transpiration
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Example 6b In-vitro Nail Transpiration
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Example 7 Membrane Resistance
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Example 8 OTTER - TEWL Correlation
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Example 9 Hair Desorption
Hair samples pre-conditioned in ambient air.
Also SC Nail Plates
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Example 10 Nail Desorption
Ambient T 25 C Ambient RH 32 Q1/W1 31
Q2/W2 66
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Example 11 Cultured Skin
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Why the AquaFlux ?

• Easy to use - unfettered by Guideline grief !
• Highest repeatability through consistent
  microclimate
• Klingon sensor - tough protected
• Highest sensitivity
• Highest flux capability
• Reliable calibration
• Versatile - transpiration, desorption, in-vivo,
  in-vitro, etc.

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Acknowledgement - The Team