Eric Assaf

When you think about bamboo, you might conjure up images of pandas snacking in a distant jungle. In fact, bamboo finds many versatile uses, in food, construction, and use in the manufacture of textiles, to name a few (Gupta 2008). People have recognized the versatility and utility of bamboo plants for centuries, especially in regions where the plant naturally occurs, and have successfully integrated it into many facets of their societies. The unique properties of bamboo have sparked considerable research interest in the plant and have led researchers at the Nanostructures for Electrical Energy Storage (NEES) Energy Frontier Research Center (EFRC) to research new processing methods that could, one day, revolutionize the construction, transportation, and aerospace industries!

Bamboo has a number of unique properties that make it a beneficial structural material.  Bamboo grows fast with an average growth rate of one hundred centimeters per day (Li 2020). Conversely, common hardwood trees grow only about 4% of their total volume per year(Alexander 2003) meaning that thousands of bamboo plants could be grown and harvested in a fraction of the time required for more traditional hardwoods. A shift away from traditional wood sources may also lead to decreased deforestation helping to heal those ecosystems devastated by the global demand for timber. Bamboo can also grow on slopes and in other areas where traditional wooded forests cannot (Hossain 2015), which opens up several new regions to a potentially profitable industry. Finally, bamboo contains a series of important molecules, such as cellulose, that create an inherently strong and create an incredibly strong material even without the need for chemical processing.

In January, 2020, researchers developed a “Strong, Tough, and Scalable Structural Material from Fast-Growing Bamboo (Li 2020).” The approach creates a densified bamboo material that is lightweight yet several times stronger than normal bamboo. The process requires only a few steps. First, the bamboo is cut and part of the inner section is removed. The bamboo is then flattened into a sheet of bamboo and chemically treated to induce a swelling and softening of the bamboo’s cell walls. The chemical treatment also removes some of the lignin from the cells of the bamboo plant. Lignin is an organic polymer, which provides the cell wall’s of plants with their characteristic rigid and tough attributes. When the lignin is removed, vacancies in the cell wall occur. Pressing these chemically treated bamboo sheets, using a high-temperature compression, allows the molecules of cellulose within the bamboo to form new hydrogen bonds in the absence of lignin. A hydrogen bond is a strong intermolecular interaction between hydrogen and some elements on the periodic table. Some more familiar hydrogen bond networks include those formed between water molecules. Upon pressing, the newly formed hydrogen bond network along with the alignment of bamboo’s cell walls cause an increase in the strength of the material while the thickness of the material decreases seventy percent.

A pictorial representation of the chemical processing and compression techniques that produce densified bamboo (Li 2020).

The researchers at NEES compared their densified bamboo material to other common infrastructure materials using metrics like specific stiffness and tensile strength. Specific stiffness is a measure of a material’s resistance to bending. A high specific stiffness means that even a lower weight material will not bend easily. Tensile strength is a measure of how much a material can be pulled on before it will break. A high tensile strength means that a material can be used to support heavy weights without failing.

They found that the densified bamboo material had a considerably higher stiffness and tensile strength than natural bamboo, stainless steels, high-alloy steels, and titanium alloys, many of which are in use in a myriad of industries. For example, bamboo is used as food, and can be used in construction to build fairly robust buildings. In essence, the densified bamboo could withstand more force than many materials often viewed as the gold-standard in terms of robustness and strength. Bamboo would not immediately replace other materials; new infrastructure would be required for bamboo to increase its prevalence as an industrial material. But advancements, such as the one cited in this paper, could represent a first step in the growth of bamboo as a building material.

As America’s infrastructure continues to age, replacement projects will be necessary to provide safety and continuity in a number of sectors, including transportation and construction. Because the densified bamboo process is largely scalable, industries may find the densified bamboo to be a cost-effective and environmentally friendly alternative for larger scale infrastructure projects, such as bridges. The natural abundance and ease of transport for this lightweight material would almost certainly further reduce its cost. While this technology is still in the research phase of development, the future for bamboo remains bright!

So, the next time you see a panda munching on a stick of bamboo, try to imagine how that bamboo might, one day, hold up your office building, or the bridge you take on your morning commute. Imagine how a plant that you may only rarely think about may, in fact, become an essential part of your daily life without you even realizing that it is there.

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The authors received funding from the US Department of Energy as part of the Nanostructures for Electrical Energy Storage (NEES) Energy Frontier Research Center (EFRC). The authors also acknowledge the support of the Maryland Nanocenter, its Surface Analysis Center, and AIMLab.


About the author(s):

Eric Assaf is a Ph.D. graduate student at the University of North Carolina at Chapel Hill under Dr. Alexander Miller. He is a member of the Alliance for Molecular PhotoElectrode Design (AMPED) EFRC. His research focuses mainly on the reduction of CO2 into higher energy and higher value molecules.

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