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Cone scales are humidity-sensitive: pine


A fully mature Monterey Pine cone on the forest floor. / Peter Fir000.. / LicenseGFDL - Gnu Free Document License

The scales of pine cones flex passively in response to changes in moisture levels via a two-layered structure.

"Dr Jeronimidis is now taking this concept further by using adaptive materials that flex in response to the level of moisture in the air—an idea borrowed from the way pine-cones open and close. Using a cellulose-like fibre composite, he has created a vent that changes from one curved shape to another, depending on the relative levels of moisture inside and outside a building. When warm, moist air builds up inside the building, the vent opens to allow it to escape. But when the air inside is dry, the vent stays shut and moist air from outdoors is kept out. 'In principle it can be made to respond naturally, without any additional power,' says Dr Jeronimidis." (The Economist 2007)

"The mechanism of bending therefore seems to depend on the way that the orientation of cellulose microfibrils controls the hygroscopic expansion of the cells in the two layers. In sclerids, the microfibrils are wound around the cell (high winding angle) allowing it to elongate when damp. Fibres have the microfibrils orientated along the cell (low winding angle) which resists elongation. The ovuliferous scale therefore functions as a bilayer similar to a bimetallic strip, but responding to humidity instead of heat." (Dawson et al. 1997:668)
About the inspiring organism
Med_pine_cone_edit Pinus

Learn more at
Organism/taxonomy data provided by:
Species 2000 & ITIS Catalogue of Life: 2008 Annual Checklist

Bioinspired products and application ideas

Application Ideas: Building vents that flex in response to humidity, textiles that help maintain comfortable body temperature over a wide range of external temperatures. Indicator for moisture levels on skin of patient.

Industrial Sector(s) interested in this strategy: Buildings, textiles, medicine

Centre for Biomimetics
George Jeronimidis Richard Bonser
University of Reading
Organismic and Evolutionary Biology
L Mahadevan
Harvard University
Dawson, C.; Vincent, J. F. V.; Rocca, A. M. 1997. How pine cones open. NATURE-LONDON-. 668-668.
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2007. Borrowing from nature. The Economist [Internet], Accessed 9/12/2007.
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Reyssat E; Mahadevan L. 2009. Hygromorphs: from pine cones to biomimetic bilayers. Journal of the Royal Society Interface. 6: 951-957.
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over 4 years ago
This comment was removed by a AskNature editor for the following reason:
Personal message not appropriate here.
over 4 years ago
I think it would. You would need to select your material to be sensitive to the range of humidity within your local area.
over 4 years ago
would this strategy work in a tropical climate?
over 7 years ago
See new reference and expert added: Reyssat and Mahadevan's "Hygromorphs: from pine cones to biomimetic bilayers."
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