1. OTTER & AquaFlux Perry Xiao London South Bank University Photophysics Research Centre & Biox Systems Ltd University Spin-out Company

2. Plan 1.OTTER Fundamentals 2.OTTER & SC Hydration 3.AquaFlux Fundamentals 4.AquaFlux Applications

3. OTTER Overview (Opto-Thermal Transient Emission Radiometry)

4. OTTER – The Spectroscopic Dimension OTTER Selectivity:- 1.Excitation 2.Thermal Emission Wavelength determines:- 1.Absorbing Species 2.Penetration Depth OTTER requires STRONG Absorption !

5. OTTER Fixed & Fibre Optics Fixed Optics Fingers, Hands & Volar Forearm Mobile Measurement Head Any skin site

6. Plan 1.OTTER Fundamentals 2.OTTER & SC Hydration 3.AquaFlux Fundamentals 4.AquaFlux Applications

7. OTTER Hydration Measurement Excitation @ 2.94µm:- H 2 O Penetration ~0.8µm Emission @ 13µm:- H 2 O Penetration ~3.3µm

8. OTTER Signal Analysis 1

9. OTTER Signal Analysis 2 Mean SC Hydration ModelSC Hydration Gradient Model

10. Example 1: Mean SC Hydration

11. Example 2: SC Hydration Gradient

12. This analysis provides a measure of SC water holding capacity Remove the time dimension by correlating Surface Hydration with Hydration Gradient.

13. Example 3: 3D Hydration Mapping Volar forearm/wrist area.

14. 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

15. 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)

16. OTTER vs Confocal Raman Contact artefacts affect ~5µm of SC Not colour-blind Interference from fluorescence

17. Plan 1.OTTER Fundamentals 2.OTTER & SC Hydration 3.AquaFlux Fundamentals 4.AquaFlux Applications

19. 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.

20. 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

21. Water Vapour Distribution Within the Chamber Skin Condenser

22. Temperature Distribution Within the Chamber Skin Condenser

23. Chamber Microclimate

24. 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

25. Droplet Method of Calibration Simple procedure - just add water Traceable to fundamental measures through research with NPL Calibration brings Tewameter & AquaFlux measurements closer together

26. Plan 1.OTTER Fundamentals 2.OTTER & SC Hydration 3.AquaFlux Fundamentals 4.AquaFlux Applications

27. 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.

28. Example 2: Repeatability

29. 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

30. Example 3b: Occlusion Recovery

31. Example 4: Dermaroller TM Dermaroller TM 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/cm 2

32. Example 5: In-vivo Fingernails

33. Example 6a: In-vitro Nail Transpiration

34. Example 6b: In-vitro Nail Transpiration

35. Example 7: Membrane Resistance

36. Example 8: OTTER - TEWL Correlation

37. Example 9: Hair Desorption Hair samples pre-conditioned in ambient air. Also SC & Nail Plates

38. Example 10: Nail Desorption Ambient T ~25 C Ambient RH ~32 % Q1/W1 ~31 % Q2/W2 ~66%

39. Example 11: Cultured Skin

40. 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.

41. Acknowledgement - The Team