OTTER & AquaFlux

OTTER&

AquaFlux

Perry Xiao

London South Bank University

Photophysics Research Centre

&

Biox Systems Ltd

University Spin-out Company

Plan

1. OTTER Fundamentals

2. OTTER & SC Hydration

3. AquaFlux Fundamentals

4. AquaFlux Applications

OTTER Overview(Opto-Thermal Transient Emission Radiometry)

OTTER – The Spectroscopic Dimension

OTTER Selectivity:-

1. Excitation

2. Thermal Emission

Wavelength determines:-

1. Absorbing Species

2. Penetration Depth

OTTER requires STRONG Absorption !

OTTER Fixed & Fibre Optics

Fixed Optics

Fingers, Hands & Volar Forearm

Mobile Measurement Head

Any skin site

Plan

1. OTTER Fundamentals

2. OTTER & SC Hydration

3. AquaFlux Fundamentals

4. AquaFlux Applications

OTTER Hydration Measurement

Excitation @ 2.94µm:-

H2O Penetration ~0.8µm

Emission @ 13µm:-

H2O Penetration ~3.3µm

OTTER Signal Analysis 1

OTTER Signal Analysis 2

Mean SC Hydration Model SC Hydration Gradient Model

Example 1: Mean SC Hydration

Example 2: SC Hydration Gradient

Example 2: SC Hydration Gradient

This analysis provides a measure of SC water holding capacity

Remove the time dimension by correlating Surface Hydration with Hydration Gradient.

Example 3: 3D Hydration Mapping

Volar forearm/wrist area.

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

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)

OTTER vs Confocal Raman

Contact artefacts affect ~5µm of SC

Not colour-blind

Interference from fluorescence

Plan

1. OTTER Fundamentals

2. OTTER & SC Hydration

3. AquaFlux Fundamentals

4. AquaFlux Applications

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.

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

Water Vapour Distribution Within the Chamber

Skin Condenser

Jz

HD

H

Lzt

H

z

HD

z

Lz

0

2

2

0

0

Temperature Distribution Within the Chamber

Skin Condenser

00

1

2

2

0

TT

TT

Lzt

T

z

TD

z

Lz

Chamber Microclimate

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

Droplet Method of Calibration

Simple procedure - just add water

Traceable to fundamental measures through research with NPL

Calibration brings Tewameter & AquaFlux measurements closer together

Plan

1. OTTER Fundamentals

2. OTTER & SC Hydration

3. AquaFlux Fundamentals

4. AquaFlux Applications

Example 1: AquaFlux vs DermaLab

Measurement speed is comparable, but the fluctuations are much lower in condenser-chamber signals.

DermaLab Signals [1] AquaFlux Signals

[1] GL Grove, MJ Grove C Zerweck & E Pierce: Computerized Evaporimetry using the DermaLab TEWL Probe. Skin Res. Technol. 5, 9-13, 1999.

Example 2: Repeatability

Example 3a: Occlusion Recovery

Final TEWL = 9.3 ± 0.2 g m-2 h-1 Occlusion effectiveness = 17.0 ± 1.6 %

Skin Surface Water Loss

Example 3b: Occlusion Recovery

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

Example 5: In-vivo Fingernails

Example 6a: In-vitro Nail Transpiration

Example 6b: In-vitro Nail Transpiration

Example 7: Membrane Resistance

Example 8: OTTER - TEWL Correlation

Example 9: Hair Desorption

Hair samples pre-conditioned in ambient air.

Also SC & Nail Plates

Example 10: Nail Desorption

Ambient T ~25 C

Ambient RH ~32 %

Q1/W1 ~31 %

Q2/W2 ~66%

Example 11: Cultured Skin

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.

Acknowledgement - The Team