Researchers from CSIC developed large area bacterial nanocellulose films with an embedded highly dispersed carbon nanotubes network
Thermoelectric materials can transform heat into electricity. Now, a team of researchers from the Institute of Materials Science of Barcelona of the Spanish National Research Council (CSIC) developed a new concept of thermoelectric material. The device that was developed using a sustainable and environmentally friendly strategy contains cellulose that is produced in situ in the laboratory by bacteria, along with small amounts of a conductive nanomaterial, carbon nanotubes. The team dispersed bacteria in an aqueous culture medium that contained sugar and carbon nanotubes in order to produce the nanocellulose fibers that form the device embedded with carbon nanotubes.
The approach offer a mechanically resistant, flexible, and deformable material, owing to the cellulose fibers. The material is also has high electrical conductivity due to the carbon nanotubes. According to the researchers, the approach aims at using sustainable materials that are not toxic for the environment. Therefore, the device is made of sustainable and recyclable materials. According to Anna Roig, researcher of this study, the mew material has a higher thermal stability compared to other thermoelectric materials based on synthetic polymers. High thermal stability allows the material to reach temperatures of 250 °C. Moreover, the device does not use toxic elements and the cellulose can easily be recycled as it can be degraded by an enzymatic process that convert it into glucose. The thickness, color, and transparency of the material can also be controlled.
The team used carbon nanotubes due to their dimensions. The nanoscale diameter and length of few microns of the carbon nanotubes allow to obtain electrical percolation, which is a continuous path where the electrical charges can travel through the material with very little quantity. This in turn allows cellulose to be conductive. Moreover, the use of such a small amount of nanotubes makes the process very economic and energy efficient, according to the researchers. The dimensions of carbon nanotubes are similar to those of cellulose nanofibres, which offers a homogeneous dispersion and the inclusion of these nanomaterials positively impacts the mechanical properties of cellulose. This makes the cellulose even more deformable, extensible, and resistant. These devices can be used to generate electricity from residual heat to feed sensors in the field of IoT. The research was published in the journal Energy & Environmental Science on January 22, 2019.