By Josh Perry, Editor
Researchers at the Institute of Materials Science of Barcelona, Spain (ICMAB-CSIC) created a new thermoelectric paper from cellulose and carbon nanotubes to convert waste heat into electricity for IoT sensors, according to a report from the institute.
Researchers in Barcelona have created thermoelectric paper. (ICMAB-CSIC)
The cellulose was grown through bacteria in the lab with small amounts of carbon nanotubes added. The researchers claim that this makes the process sustainable and environmentally-friendly. In addition, this material offers flexibility to cover devices where the waste heat is in unusual forms or large areas.
According to the report, bacteria was dispersed in a water solution containing sugars and carbon nanotubes and that created the nanocellulose fibers. The result is a mechanically-resistant, flexible material that has high electrical conductivity. It also has higher thermal stability than thermoelectric materials formed from synthetic polymers, performing at temperatures as high as 250°C.
There are no toxic elements to the material, which makes it easily recyclable, and researchers demonstrated that the thickness, color, and transparency of the material can all be tuned.
The research was recently published in Energy and Environmental Science. The abstract read:
“Waste heat to electricity conversion using thermoelectric generators is emerging as a key technology in the forthcoming energy scenario. Carbon-based composites could unleash the as yet untapped potential of thermoelectricity by combining the low cost, easy processability, and low thermal conductivity of biopolymers with the mechanical strength and good electrical properties of carbon nanotubes (CNTs).
“Here we use bacteria in environmentally friendly aqueous media to grow large area bacterial nanocellulose (BC) films with an embedded highly dispersed CNT network. The thick films (≈10 μm) exhibit tuneable transparency and colour, as well as low thermal and high electrical conductivity.
“Moreover, they are fully bendable, can conformally wrap around heat sources and are stable above 500 K, which expands the range of potential uses compared to typical conducting polymers and composites. The high porosity of the material facilitates effective n-type doping, enabling the fabrication of a thermoelectric module from farmed thermoelectric paper.
“Because of vertical phase separation of the CNTs in the BC composite, the grown films at the same time serve as both the active layer and separating layer, insulating each thermoelectric leg from the adjacent ones. Last but not least, the BC can be enzymatically decomposed, completely reclaiming the embedded CNTs.”