The pinecone and ice plant disperse their seeds in an artistic way
– folding and unfolding like origami.
Even though the cells of a pinecone are dead when it has fallen from the tree, the scales are still able to move in order to release the seeds which are captured inside. This passive mechanism works due to response in changes in relative humidity. The structure of the scales is combined by two different layers with fibers in different directions and sizes. When the pinecone dries the fibers shrink differently, which causes the scales bend out and the seeds will be dispersed. (The scale can also close again when it is moistened, as the fibers elongates differently) 1
Ice plants (Delosperma) are a group of species which grow in arid and semi-arid landscapes. They have, like the pinecone, a similar way of dispersing their seeds. However, unlike the pinecone the ice plants seed capsules have adapt to dry conditions and will only open when it is sufficiently hydrated and thus disperse the seeds when the conditions are the most favorable for growth. The Ice plant’s capsule has, in addition, a more complex structure of fibers than the pine cones’ two-layer-structure. It has a tree-dimensional hierarchy of different cell structures, arranged in a complex geometry, allowing it to unfold in a more complex, origami-like manner, unlike the simple bending movement of the pinecone’s scales. The unfolding mechanism of the desert ice plant seed capsule from the species Delosperma nakurense is illustrated in the figure below. The figure illustrates each level within the hierarchical structure, in both dry and humid conditions.2
When designing a building in an environment with great daily changes in temperature, such as the desert, we can find inspiration from the pinecone’s and Ice plant’s seed capsule’s way of adapting to daily changes in humidity. This passive bending movement of components could enhance different functions of a building’s façade at various conditions, to make the façade more efficient and adaptive. For example, it could be used to improve indoor climate by increasing the self-shading or ventilation by adjusting the façade in correspondence to the sun’s movement around the building and to temperature changes. In addition, the opening and closing movement changes the appearance and characteristics over time which could be a very interesting architectonical feature.
Building materials, design process and fabrication
To achieve a bending movement in a façade corresponding to temperature changes, a material which responds to temperature is needed. Metal is a good example of a building material which elongates with changing temperatures. By attaching two different metals with different thermal expansion to each other, it will bend according to the same principle as the pinecone. This configuration of two metals goes by the term Bimetallic strip and is used in various applications such as thermostats, ovens and irons where it turns off the power at a specific temperature.
Metal is also a quick absorber of heat as it has a low thermal capacity and therefore is very sensitive to changes in temperature. Also, as it is heated by sun radiation, temperatures above the aerial temperature can be reached, and with higher temperature, more bending.
Cladding the whole façade with bimetallic strips would be too expensive and difficult to produce. I suggest that the bimetallic strips are attached to a light weight material which could be shaped with digital fabrication methods to enable computer-based parametric design and more complex, geometric shapes and movements.
A very common building material in Morocco is clay. However, clay has a high density. A lighter alternative is expanded clay which has a third as high density. The sphere-shaped expanded clay can either be cast into forms or be 3D-printed, namely, letting robots place them and glue them together into a configuration. The pictures below, to the left, show 3D-printed rocks, a project by Gramzio Kohler, together with ETH Zurich and Self-assembly Lab. 3
Another accessible material in Morocco is cork oak. Morocco possesses 277,000 ha of Cork oak forests and is neighbor with Portugal which is the biggest producer of cork oak products.4 Expanded cork is one example of a product which could be CNC-milled into shapes or cast into forms. In addition, Morocco has a very big textile industry making fabric a third alternative of façade cladding. The pictures to the right above, shows an example of using fabric as cladding.5
The design of the bending component depends on several parameters in order to be a part of an adaptive and moveable façade. Therefore, it is useful to use a computer software which can handle many different parameters in the design process. Some parameters which needs to be considered are: Changes in aerial temperature during day and night and seasonally, sun angles (sun radiation), dimensions of the bimetallic strips, function of the shape (shading/exposed, open or closed), patterns (cladding) and building material properties.
A project done by the London-based office, rat[LAB], use temperature differences and sun radiation angels as design parameters to develop a pattern on the façade. 6
1. How pine cones open, 1997, Nature, 390, 6661, p. 668, Academic Search Complete, EBSCOhost, (viewed 5 September 2016)
2. Harrington, M, Razghandi, K, Ditsch, F, Guiducci, L, Rueggeberg, M, Dunlop, J, Fratzl, P, Neinhuis, C, & Burgert, I 2011, Origami-like unfolding of hydro-actuated ice plant seed capsules, Nature Communications, 2, p. 337, MEDLINE, EBSCOhost, (viewed 5 September 2016)
3. Gramazio Kohler Research (2015) Roch print, Chicago, 2015, Internet: http://gramaziokohler.arch.ethz.ch/web/e/forschung/297.html (viewed 9 September 2016)
4.WWF (2006) Cork Screwed? Environmental and economic impacts of the cork stoppers market, (Rapport 2006:5) Internet: http://www.wwf.org.uk/filelibrary/pdf/corkscrewed.pdf (viewed 9 September 2016)
5. Laylin, Tafline (2011) The Little Dutch “Herenhuis” Features Fabric Shingles That Flap in the Wind. Inhabitat. Internet: http://inhabitat.com/the-little-herenhuis-in-the-netherlands-has-fabric-shingles-that-flap-in-the-wind/fabric-facade-gerald-lindner-8-2 (viewed 9 September 2016)
6. Grozdanic, Lidija (2015) Cellular Morphology Facade uses design to allow buildings to adapt to different climatic conditions. Inhabitat. Internet: http://inhabitat.com/cellular-morphology-facade-uses-parametric-design-to-adapt-to-different-climatic-conditions/ (viewed 9 September 2016)