Thermoelectric textiles with nanostructured copper iodide films on cotton and polyester fabrics, stabilized and reinforced with nanocellulose

Inexpensive, flexible and durable, efficient thermoelectric (TE) fabrics have been developed for thermoelectric generators (TEGs) to power wearable electronics by harvesting body heat. To do this, we impregnated commercial cotton (Ct) and polyester (PET) fabrics with nanocellulose (NC) hydrogel prepared by TEMPO-mediated oxidation of organosolv pulp from common reed ( Phragmites australis) , and thus improved the functional properties of fabrics with NC by creating NC/Ct and NC/PET nanocomposites. For the production of thermoelectric textiles, we deposited nanostructured copper iodide (CuI) films on pure cotton and polyester fabrics, as well as on NC/Ct and NC/PET nanocomposites, using a low-temperature, low-cost, simple, and scalable water-based deposition method Successive Ionic Layer Adsorption and Reaction (SILAR). Transmission and scanning electron microscopy, energy dispersive spectrometry, X-ray diffraction and X-ray fluorescence analysis, optical spectrophotometry, and measurement of deviations in the electrical resistance of TE fabrics during continuous and cyclic bending were used to study the effect of NC hydrogel dilution with water on changes in the structure and properties of nanocellulose coatings on fabric fibers, which affects the functionality of TE textiles. Studies have shown the benefits of using dilute NC hydrogel in terms of thermoelectric performance and wear resistance of TE textiles, confirming their ability to generate electricity from human body heat. For single-leg TEGs based on CuI/NC/Ct and CuI/NC/PET textiles, whose nanocomposites were obtained using dilute NC hydrogel, continuous deformation for 24 h at a nominal bending strain ε nom = 5.56% did not cause cracking, interfacial separation, or an increase in internal resistance of more than 1.7%. An analysis of the change in their electrical resistance at 5 and 100 bending and release cycles at ε nom up to 3.3% showed that the relative increase in resistance did not exceed 5%, which confirms their sufficient flexibility and ability to withstand to mechanical forces applied by the user when worn on the body. After five cycles of such tests, the output power density of a single-leg TEG based on CuI/NC/PET thermoelectric textile reached 3 μW/cm 2 at a temperature difference of 50 K between cold and hot chromium contacts. Its open-circuit output voltage was 2.9 mV. Thus, due to the creation of nanocomposites of fabrics and nanocellulose, the achieved TE characteristics correspon