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20, Feb 2020 -

Unlocking the properties of wood... next step, wooden skyscrapers?

Unlocking the properties of wood... next step, wooden skyscrapers?

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The ever-strengthening case for using wood as a construction material was given yet another boost recently, as researchers were able to capture the visible nanostructure of living wood for the first time.

While wood has been used as a construction material for centuries, its mechanical properties have so far struggled to meet all modern standards for inclusion in major superstructures. The case for wood has not been helped by the relatively limited understanding of its cells’ exact structure.

Dr Jan Lyczakowski, from Cambridge University's Department of Biochemistry, which was involved with the new research, said while we knew that the molecular architecture of wood determined its strength, we did not know the precise molecular arrangement of the cylindrical structures found in wood cells, known as macrofibrils.

“A new technique has allowed us to see the composition of the macrofibrils, and how the molecular arrangement differs between plants, helping us understand how this might impact on wood density and strength," Dr Lyczakowski said.

Wood has its secondary cell walls to thank for its strength and rigidity. Many trees only achieve their impressive heights as a result of these secondary walls, which form a rigid structure around the cells of the trunk.

Previous imaging of wood was limited to dehydrated, heated or chemically processed samples. The team on this project adapted scanning electron microscopy at low-temperature to image the nanoscale architecture of the cell walls of living spruce, gingko and poplar trees. The secondary cell wall macrofibrils, which are 1,000 times narrower than a human hair, were revealed in microscopic detail.

Dr Raymond Wightman, Imaging Core Facility Manager at the University of Cambridge’s Sainsbury Laboratory, said the advanced techniques used in the research allowed the team to image hydrated wood cells for the first time.

"It has revealed that there are macrofibril structures with a diameter exceeding 10 nanometres in both softwood and hardwood species, and confirmed they are common across all trees studied," Dr Wrightman said.

The team also imaged the secondary cell walls of Arabidopsis thaliana, the standard reference plant for genetics and molecular research. It too was found to have prominent macrofibrils, and could therefore be invaluable as a model for further wood architecture research, including the involvement of specific molecules in the formation of macrofibrils.

Professor Paul Dupree, of Cambridge's Department of Biochemistry, a co-author of the study, said visualising the molecular architecture of wood allows for investigation into how changing the arrangement of certain polymers might alter wood strength.

"Understanding how the components of wood come together to make super strong structures is important for understanding both how plants mature, and for new materials design,” Professor Dupree said.

"There is increasing interest around the world in using timber as a lighter and greener construction material.

"If we can increase the strength of wood, we may start seeing more major constructions moving away from steel and concrete to timber."

And now somehow it does not seem too extreme to imagine cities built from skyscrapers made from wood!

Source: University of Cambridge / Science Daily

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