This past week I had the opportunity to apply the FBS analysis tool. FBS stands for Function – Behavior – Structure. FBS paths are utilized in design by analogy as an abstract mapping technique between a source concept and a target concept. My focus was on pine cones and how they open. I used the pine cone FBS path outcomes to progress from Biology to Design and complete an ADP. ADP is essentially the translation of biology into an Abstracted Design Principle (ADP), which can then be used in various domains. I chose to focus mainly on architecture in the below ADP, and suggest a few directions for potential uses.  

F<-B<-S —> ADP

 

Strategy

Pinus roxburghii (chir pine or long-needle pine) scales expand when exposed to humidity.

Biomimicry Taxonomy Function:

  • Modify chemical/electrical state – reactivity with water
  • Process information – sense signals/environmental cues – temperature/atmospheric conditions

Functions (FBS):

  • Open
  • Close
  • Expand
  • Collapse
  • Shrink
  • Swell
  • Rotate
  • Move
  • Compress
  • Adapt

pine cone 3.png

Mechanism

Pine cones have the remarkable ability to expand (open/close) in response to changes in humidity. Scales of the pine cone are made up of various structures and materials, which behave differently when in contact with water. Scales have varying sized pores with the outer scale pores measuring 50 μm in diameter, and the scales attached to the centre of the cone, pores of approximately 150 μm in diameter. When the scale pores get in contact with water molecules, change in air pressure inside the cells occur. This change in ratio between water and air in the cell structure, induces expansion of the scale. The differential expansion of both pore layers results in rotation of Isometric shaped scales. This rotation creates a folding motion of the scales. The fractal placement of the scales also enables faster folding times for different scales. Response times and duration differs between open and closing states of scales, but can be induced by changing certain variables. The pine tree makes use of this ingenious scale expansion design, in order to protect its seeds and close its scales when exposed to humidity. 

Abstracted Design Principle

Water-absorbent structures that expand and rotate when in contact with water (Bilayered structure of individual scales that change conformation when humidity changes).

Potential uses in Architecture:

  • When it rains…roofs or windows which are open can close up automatically
  • When a room gets cold… the door can automatically close
  • When a room gets too humid… it could trigger a notification to dry out the air
  • If dams leak…. adaptive damn walls can expand and cover leak

pine cone 2

“With artificial heating of cones at 40 °C, bursting and complete opening of the cones occurred after 6–6.2 d in all provenances, whereas at 75 °C the cones opened after 6–6.75 h (Table 2). At 90 °C bursting of the cones occurred after 4.5–4.75 h. At 100 °C, 120 °C and 135 °C the minimum time required for cone bursting and release of seeds was 2.5 h, 1.5 h and 1 h, respectively. At 150 °C the seeds were released within 45 min in all provenances. In the control (sun drying), it took 25 d for the cones to release the seeds.” (Ghildiyal) 

“Cones of most species can be opened at a kiln temperature not exceeding 55 °C and humidity of c. 20%, but the cones of a few species, e.g. P. banksiana, P. clausa and P. ponderosa var. scopulorum, require a higher temperature for opening and seed dispersal.” (Ghildiyal) 

“The passive motions in these plants are driven by the humidity (water-potential) gradient between the cells at the tissue level (sclerenchymal tissue) and the ambient air15. When water is absorbed/expelled in response to air humidity, the tissue expands/shrinks anisotropically in a direction perpendicular to the fibrils’ orientation2,16. Asymmetric orientation of the fibrils at the organ level converts local swelling/shrinking to a global bending movement17. This change occurs sensitively; with a 1% change in relative humidity at 23 °C, the coefficient of hygroscopic expansion of the fibers (0.06 ± 0.02) is significantly lower than that of sclerids (0.20 ± 0.04) in pine cones1. These microscopic humidity-induced strains on the cells lead to macroscopic changes17.” (Song) 

“the bract scales, fibers and innermost lignified structure, respectively. Brown bract scales and white fibers are of different materials: not only are the colors but the constructions of these layers differentiable. The bract scales have dense structures with pores of small sized (Fig. 3f). However, the threads like fibers in the middle layer are tangled up (Fig. 3g). Thus, the middle layer has relatively large pores. Detailed 3D structures are shown in Supplementary Video 1 and 2.” (Song, 2015) 

“After the droplet reaches the center of the pine cones (Fig. 2a), the water is absorbed by the bract scales and spreads out into the scales and fibers….which eventually causes the structural transformation.” (Song, 2015)

Primary Resources:

Ghildiyal, Sk, et al. “Effect of temperature on cone bursting, seed extraction and germination in five provenances ofPinus roxburghiifrom Garhwal Himalaya in India.” Southern Forests: a Journal of Forest Science, vol. 70, no. 1, 2008, pp. 1–5., doi:10.2989/south.for.2008.70.1.1.511.

Reyssat, E., and L. Mahadevan. “Hygromorphs: from pine cones to biomimetic bilayers.” Journal of The Royal Society Interface, vol. 6, no. 39, Jan. 2009, pp. 951–957., doi:10.1098/rsif.2009.0184.

Song, Kahye, et al. “Journey of water in pine cones.” Scientific Reports, vol. 5, no. 1, June 2015, doi:10.1038/srep09963.

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