Conversion of Wood into Nanogenerators:
The team began by transforming wood into a nanogenerator by sandwiching two pieces of functionalized wood between electrodes. Like a shirt-clinging sock fresh out of the dryer, the wood pieces become electrically charged through periodic contacts and separations when stepped on, a phenomenon called the triboelectric effect. The electrons can transfer from one object to another, generating electricity. However, there's one problem with making a nanogenerator out of wood. But there was a big challange for researchers in the development of electricity conducting wood.
A Big challenge - Neutral Wood
Wood is basically triboneutral. It means that wood has no real tendency to acquire or to lose electrons. This limits the material's ability to generate electricity, so the challenge was making wood that is able to attract and lose electrons.
To boost wood's triboelectric properties, the scientists coated one piece of the wood with polydimethylsiloxane (PDMS), a silicone that gains electrons upon contact, while functionalizing the other piece of wood with in-situ-grown nanocrystals called zeolitic imidazolate framework-8 (ZIF-8). ZIF-8, a hybrid network of metal ions and organic molecules, has a higher tendency to lose electrons.
Testing with diffrent types of wood:
Then researchers tested different types of wood to determine whether certain species or the direction in which wood is cut could influence its triboelectric properties by serving as a better scaffold for the coating.
Results:
The researchers found that a triboelectric nanogenerator made with radially cut spruce, a common wood for construction in Europe, performed the best. Together, the treatments boosted the triboelectric nanogenerator's performance: it generated 80 times more electricity than natural wood. The device's electricity output was also stable under steady forces for up to 1,500 cycles.
"Our focus was to demonstrate the possibility of modifying wood with relatively environmentally friendly procedures to make it triboelectric," says Panzarasa. "Spruce is cheap and available and has favorable mechanical properties. The functionalization approach is quite simple, and it can be scalable on an industrial level. It's only a matter of engineering."
Applications of electricity generating wood:
Besides being efficient, sustainable, and scalable, the newly developed nanogenerator also preserves the features that make the wood useful for interior design, including its mechanical robustness and warm colors. The researchers say that these features might help promote the use of wood nanogenerators as green energy sources in smart buildings. They also say that wood construction could help mitigate climate change by sequestering CO2 from the environment throughout the material's lifespan.
The next step for Panzarasa and his team is to further optimize the nanogenerator with chemical coatings that are more eco-friendly and easier to implement. "Even though we initially focused on basic research, eventually, the research that we do should lead to applications in the real world," says Panzarasa. "The ultimate goal is to understand the potentialities of wood beyond those already known and to enable wood with new properties for future sustainable smart buildings."
References:
- Materials provided by Cell Press.
- Jianguo Sun, Kunkun Tu, Simon Büchele, Sophie Marie Koch, Yong Ding, Shivaprakash N. Ramakrishna, Sandro Stucki, Hengyu Guo, Changsheng Wu, Tobias Keplinger, Javier Pérez-RamÃrez, Ingo Burgert, Guido Panzarasa. Functionalized wood with tunable tribopolarity for efficient triboelectric nanogenerators. Matter, 2021; 4 (9): 3049 DOI: 10.1016/j.matt.2021.07.022
