1. Beaver Inspired Textiles
A hairy situation

2. Scratch my back, I scratch yours

3. Leave it to beaver
Beaver and co circa 1960
Beaver circa forever

4. Where do beavers live and why?

5. Beaver’s claim to fame
Stays Warm in Cold Water
Fabulous Hair

6. What is this fabulous hair?
Beaver under hair
Guard hair

7. Underhair: petals, grooves, and fins
50 mm
Air bubbles

8. Study aim Decipher Air Entrainment Process in Simplified System
Working at the Mesoscale (mm to cm)

9. Geometric patterns: something’s up

10. Outliers – something’s up
High hair density
Short hairs
Guard hairs = black bars
Underhairs = white bars

11. Experimental method Step 2: Casting PDMS rubber
Step 1: Laser cutting acrylic molds

12. Fitting the mold: experimental apparatus
Entrained air
Silicone oil
(2.7 mm)
e ~ 0.3 mm
d = 0.5 – 2 mm

13. Take the plunge: getting entrained

14. Physical model
“Tube” of water

15. under pressure: liquid-air interface
Viscous dissipation
Ambient pressure
Laplace
Hydrostatic
Inertia
Fluid mechanics world series champs!
All this pressure pushing down on me…
Liquid
Air

16. Hydrostatic pressure
Image credit:

17. Hydraulic inertia aka momentum change
Pressure differential makes fluid flow
Fluid flow => kinetic energy

18. Laplace pressure aka bubble pressure
Pressure difference across curved surface

19. Viscous dissipation
Image credit:

20. We now pause for a station identification and little mathemagic….

21. The big result

22. The big questions What features did the nasto et al model capture?
What features were not captured? Are they important?
What are the known limitations of the study?
What could potentially do to address these questions? Do we have the equipment/technology to address those questions at W&L? (hint: likely yes)

23. References/image credits
A Nasto et al. Air entrainment in hairy surfaces, Physical Review of Fluids 1, (2016)
JW Weisel et al. River otter hair structure facilities interlocking to impede penetration of water and allow trapping of air, Can. J. Zool. 83: (2005)
HEM Liwanag et al. Morphological and thermal properties of mammalian insulation: the evolution of fur for aquatic living, Biol. Journal of Linnean society, 106, , 2012.
siloxane-pdms-and-microfluidics/