Quantification of feather structure, wettability and resistance to liquid penetration
Birds in the cormorant (Phalacrocoracidae) family dive tens of metres into water to prey on fish while entraining a thin layer of air (a plastron film) within the microstructures of their feathers. In addition, many species within the family spread their wings for long periods of time upon emerging...
| Main Authors: | , , , , , , , |
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| Format: | Article |
| Language: | en_US |
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Royal Society Publishing
2017
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| Online Access: | http://hdl.handle.net/1721.1/109814 https://orcid.org/0000-0003-4591-6090 https://orcid.org/0000-0003-3570-8917 https://orcid.org/0000-0003-1085-7692 |
| _version_ | 1826190112821608448 |
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| author | Parker, A. R. Srinivasan, Siddarth Chhatre, Shreerang Sharad Guardado, Jesus Omar Park, Kyoo Chul Rubner, Michael F McKinley, Gareth H. Cohen, Robert E |
| author2 | Massachusetts Institute of Technology. Department of Chemical Engineering |
| author_facet | Massachusetts Institute of Technology. Department of Chemical Engineering Parker, A. R. Srinivasan, Siddarth Chhatre, Shreerang Sharad Guardado, Jesus Omar Park, Kyoo Chul Rubner, Michael F McKinley, Gareth H. Cohen, Robert E |
| author_sort | Parker, A. R. |
| collection | MIT |
| description | Birds in the cormorant (Phalacrocoracidae) family dive tens of metres into water to prey on fish while entraining a thin layer of air (a plastron film) within the microstructures of their feathers. In addition, many species within the family spread their wings for long periods of time upon emerging from water. To investigate whether wetting and wing-spreading are related to feather structure, microscopy and photographic studies have previously been used to extract structural parameters for barbs and barbules. In this work, we describe a systematic methodology to characterize the quasi-hierarchical topography of bird feathers that is based on contact angle measurements using a set of polar and non-polar probing liquids. Contact angle measurements on dip-coated feathers of six aquatic bird species (including three from the Phalacrocoracidae family) are used to extract two distinguishing structural parameters, a dimensionless spacing ratio of the barbule (D*) and a characteristic length scale corresponding to the spacing of defect sites. The dimensionless spacing parameter can be used in conjunction with a model for the surface topography to enable us to predict a priori the apparent contact angles of water droplets on feathers as well as the water breakthrough pressure required for the disruption of the plastron on the feather barbules. The predicted values of breakthrough depths in water (1–4 m) are towards the lower end of typical diving depths for the aquatic bird species examined here, and therefore a representative feather is expected to be fully wetted in a typical deep dive. However, thermodynamic surface energy analysis based on a simple one-dimensional cylindrical model of the feathers using parameters extracted from the goniometric analysis reveals that for water droplets on feathers of all six species under consideration, the non-wetting ‘Cassie–Baxter’ composite state represents the global energy minimum of the system. By contrast, for other wetting liquids, such as alkanes and common oils, the global energy minimum corresponds to a fully wetted or Wenzel state. For diving birds, individual feathers therefore spontaneously dewet once the bird emerges out of water, and the ‘wing-spreading’ posture might assist in overcoming kinetic barriers associated with pinning of liquid droplets that retard the rate of drying of the wet plumage of diving birds. |
| first_indexed | 2024-09-23T08:35:14Z |
| format | Article |
| id | mit-1721.1/109814 |
| institution | Massachusetts Institute of Technology |
| language | en_US |
| last_indexed | 2024-09-23T08:35:14Z |
| publishDate | 2017 |
| publisher | Royal Society Publishing |
| record_format | dspace |
| spelling | mit-1721.1/1098142022-09-30T09:49:07Z Quantification of feather structure, wettability and resistance to liquid penetration Quantification of feather structure, wettability and resistance to liquid penetration Parker, A. R. Srinivasan, Siddarth Chhatre, Shreerang Sharad Guardado, Jesus Omar Park, Kyoo Chul Rubner, Michael F McKinley, Gareth H. Cohen, Robert E Massachusetts Institute of Technology. Department of Chemical Engineering Massachusetts Institute of Technology. Department of Materials Science and Engineering Massachusetts Institute of Technology. Department of Mechanical Engineering Srinivasan, Siddarth Chhatre, Shreerang Sharad Guardado, Jesus Omar Park, Kyoo Chul Rubner, Michael F McKinley, Gareth H. Cohen, Robert E Birds in the cormorant (Phalacrocoracidae) family dive tens of metres into water to prey on fish while entraining a thin layer of air (a plastron film) within the microstructures of their feathers. In addition, many species within the family spread their wings for long periods of time upon emerging from water. To investigate whether wetting and wing-spreading are related to feather structure, microscopy and photographic studies have previously been used to extract structural parameters for barbs and barbules. In this work, we describe a systematic methodology to characterize the quasi-hierarchical topography of bird feathers that is based on contact angle measurements using a set of polar and non-polar probing liquids. Contact angle measurements on dip-coated feathers of six aquatic bird species (including three from the Phalacrocoracidae family) are used to extract two distinguishing structural parameters, a dimensionless spacing ratio of the barbule (D*) and a characteristic length scale corresponding to the spacing of defect sites. The dimensionless spacing parameter can be used in conjunction with a model for the surface topography to enable us to predict a priori the apparent contact angles of water droplets on feathers as well as the water breakthrough pressure required for the disruption of the plastron on the feather barbules. The predicted values of breakthrough depths in water (1–4 m) are towards the lower end of typical diving depths for the aquatic bird species examined here, and therefore a representative feather is expected to be fully wetted in a typical deep dive. However, thermodynamic surface energy analysis based on a simple one-dimensional cylindrical model of the feathers using parameters extracted from the goniometric analysis reveals that for water droplets on feathers of all six species under consideration, the non-wetting ‘Cassie–Baxter’ composite state represents the global energy minimum of the system. By contrast, for other wetting liquids, such as alkanes and common oils, the global energy minimum corresponds to a fully wetted or Wenzel state. For diving birds, individual feathers therefore spontaneously dewet once the bird emerges out of water, and the ‘wing-spreading’ posture might assist in overcoming kinetic barriers associated with pinning of liquid droplets that retard the rate of drying of the wet plumage of diving birds. 2017-06-13T14:45:26Z 2017-06-13T14:45:26Z 2014-04 2014-03 Article http://purl.org/eprint/type/JournalArticle 1742-5689 1742-5662 http://hdl.handle.net/1721.1/109814 Srinivasan, S.; Chhatre, S. S.; Guardado, J. O.; Park, K.-C.; Parker, A. R.; Rubner, M. F.; McKinley, G. H. and Cohen, R. E. “Quantification of Feather Structure, Wettability and Resistance to Liquid Penetration.” Journal of The Royal Society Interface 11, no. 96 (April 2014): 20140287 © 2014 The Author(s) https://orcid.org/0000-0003-4591-6090 https://orcid.org/0000-0003-3570-8917 https://orcid.org/0000-0003-1085-7692 en_US http://dx.doi.org/10.1098/rsif.2014.0287 Journal of The Royal Society Interface Creative Commons Attribution-Noncommercial-Share Alike http://creativecommons.org/licenses/by-nc-sa/4.0/ application/pdf Royal Society Publishing MIT Web Domain |
| spellingShingle | Parker, A. R. Srinivasan, Siddarth Chhatre, Shreerang Sharad Guardado, Jesus Omar Park, Kyoo Chul Rubner, Michael F McKinley, Gareth H. Cohen, Robert E Quantification of feather structure, wettability and resistance to liquid penetration |
| title | Quantification of feather structure, wettability and resistance to liquid penetration |
| title_full | Quantification of feather structure, wettability and resistance to liquid penetration |
| title_fullStr | Quantification of feather structure, wettability and resistance to liquid penetration |
| title_full_unstemmed | Quantification of feather structure, wettability and resistance to liquid penetration |
| title_short | Quantification of feather structure, wettability and resistance to liquid penetration |
| title_sort | quantification of feather structure wettability and resistance to liquid penetration |
| url | http://hdl.handle.net/1721.1/109814 https://orcid.org/0000-0003-4591-6090 https://orcid.org/0000-0003-3570-8917 https://orcid.org/0000-0003-1085-7692 |
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