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Charlotte Py, Charles Baroud, José Bico , Benoît Roman, Sébastien Neukirch, Arezki Boudaoud

Elastocapillarity in wet hairs. Charlotte Py, Charles Baroud, José Bico , Benoît Roman, Sébastien Neukirch, Arezki Boudaoud with Loïc Moulin, Renaud Bastien, Lionel Doppler, Paul Reverdy. nanotubes forest. Chakrapani et al . 2004. 2 m m. 1 m m. photoresist. artificial gecko.

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Charlotte Py, Charles Baroud, José Bico , Benoît Roman, Sébastien Neukirch, Arezki Boudaoud

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  1. Elastocapillarity in wet hairs Charlotte Py, Charles Baroud,José Bico, Benoît Roman, Sébastien Neukirch, Arezki Boudaoud with Loïc Moulin, Renaud Bastien, Lionel Doppler, Paul Reverdy nanotubes forest Chakrapani et al. 2004 2 mm 1 mm photoresist artificial gecko Tanaka et al. 1993 Geim et al. 2003 PMMH-ESPCI, LadHyx, LPS-ENS, LMM-Paris6

  2. Macroscopic brushes 1mm with Loïc Moulin

  3. 2-lamellae Lwet[mm] Ltotal Lstick d Lstick 2g hJurin = rgd Lwet Ltotal [mm] plastic transparency, d = 1mm, h = 100mm silicone oil

  4. 170 mm 100 mm Eh 3 50 mm Fracture ? Lstick/LEC 2 d g 3 Lstick Lstick Eh ~ Lstick 2 d Griffith, 1921 Lstick 1/4 3 Eh d ~ LECd Lstick ~ 1/2 1/2 1/2 g Elasto-capillary length LEC = g d/LEC

  5. Multi-lamellae Lstick ~ NdLEC 2 2 4 3 d dN/2 Lstick[mm] Eh3N/2 Lstick N lamellae N lamellae

  6. n(N) f(N/Nmax) Nmax = 2 Ntotal p actual brush ≠ 2 Self-similar distributions coalescence Nmax f(N/Nmax) 2 3 Nmax = 6 Nmax = 7 Nmax = 8 Nmax = 9 Nmax = 10 Nmax = 11 4 5 … fragmentation N/Nmax

  7. d 1/2 1/2 3/8 Lstick ~ N d LEC d N/2 N/2 N/2 Lstick/d LEC 1/2 1/2 Eb3N/2 Lsec LEC = g Eb 3 Fibre bundles N with Renaud Bastien

  8. LEC = L > g /R g Eh 3 Wrapping a droplet 3d ? flexible sheet L folds ? crumpling ? singularities ? 2d g g R with Lionel Doppler & Paul Reverdy

  9. 3d-shapes 1 mm 1 mm

  10. Pyramides 1 mm

  11. N = 2 p Sticking cascade Ideal brush Actual brush n(N)/Ntotal -2 n(N)/Ntotal ~1/N size N

  12. ge3 L ~ hQ ge3 Qmax~ hd "Poils" liquides Q Q d e ~ 1mm x y y/L = ln(x/Lq0 +1) cellule de Hele-Shaw gravité  élasticité avec Jérôme Guilet, Vithiya Vairon, Priscilla Poulay Ramen

  13. Spéculations : pattes de Gecko Kellar Autumn setae adhésion sèche : van der Waals souplesse  bon contact, mais autocollage structure ramifié optimale rigidité / adhésion ?

  14. ~ LECd Lstick 1/2 1/2 Eb 3 Fibres b elementary sticking: Lstick/LEC Ikea lamp fibre optical fibre glass fibre Elasto-capillary length LEC = g d/LEC with Renaud Bastien

  15. Électromouillage ? U U = 0 U = 50V Krupenkin et al. (2004) mPhase Technologies

  16. Nmax 1 2 3 4 5 … n(N)/Ntotal ~1/N 2 Simulation numérique Espacement régulier perturbé + collage du couple le plus intime

  17. Coalescence de Smoluchowski k N1-N2 N1+N2 t  L k(N1,N2) ~ CN1 CN2 d[N1 +N2 -Nmax(t)] Solution auto-similaire coalescence fracture 1 f(N/Nmax) CN(t) = Nmax 2 avec Arezki Boudaoud

  18. Piercing hairs

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