Research suggests plant fibers can be used for sustainable devices

Thermal insulation is a characteristic of several materials generated from plants, including cellulose. In contrast, a novel material derived from cellulose nanofibers has high thermal conductivity. This makes it practical in fields where synthetic polymer materials were previously the norm.

Research into cellulose-based materials could result in more environmentally friendly technology applications when thermal conductivity is required because they are more environmentally friendly than polymers.

Because cellulose plays a crucial structural role in plant cell walls, trees are able to reach such heights. But its overlapping nanoscopic threads are what gives the object its surprising material toughness.

Cellulose nanofiber (CNF) materials have been employed in a lot of commercial items lately because of how strong and long-lasting they are compared to polymer-based materials like plastics, which can be bad for the environment. But now and for the first time, a research team from the Graduate School of Engineering at the University of Tokyo, under the direction of Professor Junichiro Shiomi, has examined hitherto unrecognized thermal properties of CNF, and their findings suggest these materials may be much more valuable.

"If you see plant-derived materials such as cellulose or woody biomass used in applications, it's typically mechanical or thermally insulating properties that are being employed," said Shiomi. "When we explored the thermal properties of a yarn made from CNF, however, we found that they show a different kind of thermal behavior, thermal conduction, and it's very significant, around 100 times higher than that of typical woody biomass or cellulose paper."

Because of how it is manufactured, yarn made from CNF has excellent heat conductivity. The cellulose fibers found in nature are incredibly disordered, but CNF is made by combining cellulose fibers and aligning them in the same direction using a technique known as the flow-focusing method.

Heat can move along this firmly connected and arranged bundle of rod-shaped fibers, whereas, in a more disorganized arrangement, heat would evaporate more quickly.

"Our main challenge was how to measure the thermal conductivity of such small physical samples and with great accuracy," said Shiomi. "For this, we turned to a technique called T-type thermal conductivity measurement. It allowed us to measure the thermal conductivity of the rod-shaped CNF yarn samples which are only micrometers (a micrometer equaling one-thousandth of a millimeter) in diameter. But the next step for us is to perform accurate thermal tests on two-dimensional textilelike samples.