Stretchable and flexible thermoelectric polymer composites

Thermoelectric devicesgenerate an electrical current when there is a temperature gradient between thehot and cold junctions of two dissimilar conductive materials typically n-typeand p-type semiconductors. Consequently, also... [ view full abstract ]

Thermoelectric devicesgenerate an electrical current when there is a temperature gradient between thehot and cold junctions of two dissimilar conductive materials typically n-typeand p-type semiconductors. Consequently, also the polymeric semiconductorsfilled by different forms of carbon nanotubes with proper structural hierarchyand thermoelectric properties may transfer temperature difference into electricity.In spite of their lower thermoelectric efficiency in terms of the figure ofmerit, the properties as stretchability, flexibility, light weight, low thermalconductivity, easy processing and low manufacturing cost are advantages in manytechnological and ecological applications.

Polyurethane based highly elastic composites filled by multiwalled carbon nanotubes (MWCTs)were prepared by sonication of nanotube dispersion in a polyurethane solutionfollowed by their precipitation. The amounts of oxygenated functional groups attached on MWCNTsurface, which constitute majority of p-type charge carriers, were further increasedby HNO₃ oxidation. P-type of charge carriers were further increasedby doping with molecules of triphenylphosphine. Foraltering p-type MWCNTs into n-type ones, Ag nanoparticles were deposited onMWCNT surface and then doped by 7,7,8,8-tetracyanoquinodimethane. Both types of MWCNTs were used to manufacturethermoelectric module generating thermoelectric voltage, which proved also as aself-powered thermoelectric sensor for strain, stress and chemical vapordetection. It turned to advantage that the generation of thermoelectric power wassignificantly affected by the applied deformation or change of chemicallymonitored surroundings.

This work was supported by the Ministryof Education, Youth and Sports of the Czech Republic – Program NPU I (LO1504)and with the support of the Operational Program Research and Development forInnovations co-funded by the European Regional Development Fund (ERDF) and the nationalbudget of the Czech Republic, within the framework of the project CPS-strengthening research capacity (reg. number: CZ.1.05/2.1.00/19.0409).