1. Literature Review on
Superhydrophobic Self-Cleaning
Surfaces produced by Electrospinning.
AUTHORS: Iurii Sas, Russell E. Gorga, Jeff A. Joines,
Kristin A. Thoney
PRESENTED BY: Niranjan Ramakrishnegowda.

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INDEX
 Applications.
 Introduction.
 Self-Cleaning and Superhydrophobicity.
 Electrospinning.
 The Electrospinning Parameters.
 Modifications of Electrospinning Apparatus and techniques.
 Superhydrophobic Polystyrene Webs.
 Ready to see the Magic?
 References.

3. Applications
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thats-impossible-stain.html
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http://www.cnet.com/news/this-superhydrophobic-coating-is-truly-
stunning/

4. Introduction
Requirements: Right surface chemistry and Roughness to
control wettability.
Two approaches to fulfill the requirements,
Complete wettability of the surface is achieved by incorporating photocatalytic
chemicals, for example, TiO2.
With the help of high water-repellency or superhydrophobicity of a surface.
Quote: Mother Nature isn't a muse exclusive to the artist, she can also
inspire scientists, engineers and industrialists.
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http://www.thenakedscientists.com/HTML/articles/article/biomimeticsborrow
ingfrombiology/

5. Introduction
Why Electrospinning?
 Easy to set up for laboratory research.
 Flexibility in controlling the parameters to obtain required
surface Morphology.
 Fibers produced possess same properties as the natural
Superhydrophobic fibers.
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6. Self-Cleaning and Superhydrophobicity
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Static contact angle of liquid droplet on smooth
solid surface.
Young’s Model (Static Case).
Even for the lowest surface energy (6.7 mJ/m2) of the surface with regularly aligned closest-
hexagonal-packed CF3 groups the WCA was just 119 degrees.

7. Self-Cleaning and Superhydrophobicity
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Wenzel and Cassie’s Model (Static Case).
Static contact angle of liquid droplet on rough
surface: (a) Wenzel’s model. (b) Cassie’s model.

8. Self-Cleaning and Superhydrophobicity
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Water droplet on tilted surface. Adapted from Ref. 26, with
permission from American Chemical Society.
Dynamic Case for tilted Surface proposed by Oner and McCarthy.
H= θR – θA (contact angle hysteresis).

9. Electrospinning
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Schematic of the basic set-up for electrospinning.

10. The Electrospinning Parameters
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The morphology of resulting fibers is affected by a combination of all
electrospinning parameters.

11. Modifications of Electrospinning Apparatus and
Techniques
Intention:
 To increase Process Productivity.
 To extend the range of polymers used.
 To Produce multicomponent fibers/ webs.
Modifications to basic single-needle in Electrospinning.
 Melt spinning.
 Coaxial spinning.
 Multijet spinning.
 Needless spinning (Production rate 170 g/h.)
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12. Superhydrophobic Polystyrene Webs
Why Polystyrene?
Cheap and easy to use in electrospinning.
Relatively low surface energy.
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Effect of solvent composition (THF:DMF ratio) on
fiber diameter of electrospun polystyrene fibers.
Effect of solvent composition (THF:DMF ratio) on
water contact angle (squares) and roll-off angle (circles) of
electrospun polystyrene webs.

13. Superhydrophobic Polystyrene Webs
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SEM images of electrospun PS fibers formed from various weight ratios of THF:DMF in solvent: (a) 4:0, (b) 3:1, (c) 2:2,
(d) 1:3, (e) 0:4.

14. Superhydrophobic Polystyrene Webs
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SEM image of electrospun PANI/PS composite
film.

15. Superhydrophobic Polystyrene Webs
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SEM image of electrospun BMIPF6/PS
composite film.

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Ready to see the Magic?

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References
 Gould, P. Mater. Today 2003, 6, 44–48.
 Parkin, I. P.; Palgrave, R. G. J. Mater. Chem. 2005, 15, 1689–1695.
 Li, X. M.; Reinhoudt, D.; Crego-Calama, M. Chem. Soc. Rev. 2007, 36,
1350–1368.
 Ma, M.; Hill, R. M. Curr. Opin. Colloid Interface Sci. 2006, 11,193–202.
 Sun, T.; Feng, L.; Gao, X.; Jiang, L. Acc. Chem. Res. 2005, 38, 644–652.
 Ma, M.; Hill, R. M.; Rutledge, G. C. J. Adhes. Sci. Technol. 2008, 22,
1799–1817.
 Li, J.; Zhang, Z.; Xu, J.; Wong, C. P. In Kirk-Othmer Encyclopedia of
Chemical Technology; Othmer, K., Eds.; Wiley: Hoboken, NJ, 2007; Vol.
22, pp 108–127.