Botanists aren't always genetic engineers. This week Nigel Chaffey finds some have branched out into civil engineering.
Whilst it is said that necessity is the mother of invention*, nature is increasingly the source of the necessary inspiration for human inventiveness**. And so important is that nature-inspiration that it’s been developed as the discipline of biomimetics. Three items with a building construction theme admirably demonstrate this in action.
First we have Thomas Simmons et al. and their study of the folding of xylan onto cellulose microfibrils in plant cell walls. Cellulose is the primary strengthening component of plant cell walls, and it is further strengthened by interaction with the hemicellulose xylan (which is apparently the most prevalent non-cellulosic polysaccharide on the planet). Examining Arabidopsis with solid state nuclear magnetic resonance (ssNMR), the team identified how this cellulose-xylan bonding occurs in planta. Knowing how this takes place is likely to lead to better ways of uncoupling the two components, when it is desirable that plant cell walls are more completely digested – e.g. in biofuel production. But, equally, knowing the coupling mechanism involved – and improving upon it – could pave the way to development of ‘better’ wood that may enable construction of buildings as tall as skyscrapers.
In my mind I now imagine the slightly surreal situation where wooden skyscrapers might be built in the far East with scaffolding made from bamboo. Have plants – or their products – ever scaled such lofty heights before? However, if we are to build such tall buildings, we don’t want them toppling over if an earthquake strikes. In this connection, workers at the Plant Biomechanics Group of the University of Freiburg (Germany) are trying to unlock the structural secrets of the extremely tough shell of the coconut (the fruit of the coconut palm Cocos nucifera). One of the striking anatomical features they’ve discovered is the ladder-like arrangement of the vessels within the endocarp layer, which organisation is thought to help the coconut better withstand bending forces. Transferring this insight into a civil engineering context, the group are investigating whether this endocarp geometry could be applied to the arrangement of ‘textile fibres’ within concrete, to enable deflection of cracks – such as those that may be caused by earthquakes, rockfall and other natural or man-made hazards. Elegant, endocarpal enlightenment for enduring edifices? ***
And, completing this item’s trilogy, a team that includes Prof. Dr Thomas Speck and Dr Tom Masselter from the Plant Biomechanics Group won a Materialica Design + Technology Gold Award in 2016 for their three-armed ‘technical fiber-reinforced ramification’. This structure was inspired by a magnetic resonance imaging study of the functional anatomy and biomechanics of the Madagascar dragon tree (Dracaena marginata). This multi-purpose structure is expected to have uses in automotive and mechanical and aerospace engineering, as well as in architecture. Plants, showing humans the way (again, still…)!
*** Which personal protective property appears to have been anticipated by the coconut-hiding octopus long before humans stumbled upon this possibility…
Simmons, T. J., Mortimer, J. C., Bernardinelli, O. D., Pöppler, A.-C., Brown, S. P., deAzevedo, E. R., … Dupree, P. (2016). Folding of xylan onto cellulose fibrils in plant cell walls revealed by solid-state NMR. Nature Communications, 7, 13902. https://doi.org/10.1038/ncomms13902
Masselter, T., Hesse, L., Böhm, H., Gruhl, A., Schwager, H., Leupold, J., … Speck, T. (2016). Biomimetic optimisation of branched fibre-reinforced composites in engineering by detailed analyses of biological concept generators. Bioinspiration & Biomimetics, 11(5), 055005. https://doi.org/10.1088/1748-3190/11/5/055005
Hesse, L., Masselter, T., Leupold, J., Spengler, N., Speck, T., & Korvink, J. G. (2016). Magnetic resonance imaging reveals functional anatomy and biomechanics of a living dragon tree. Scientific Reports, 6(1). https://doi.org/10.1038/srep32685