The aqueous processing of carbon nanofibers via cellulose nanocrystals as a green path towards e-textiles with n-type thermoelectric behaviour

Cellulose nanocrystals (CNCs) are a nanostructured biopolymer with unique properties, such as high strength and water stability. These properties make CNCs ideal for diverse applications, including dispersing agents for hydrophobic carbon nanomaterials in water. Specifically, carbon nanomaterials can be integrated into textiles to produce flexible electronic wearables with excellent performance. However, the necessary prerequisite of achieving stable liquid dispersions of these carbon nanomaterials, such as nanofibers (CNFs) typically involves the use of organic solvents or high concentrations of hazardous surfactants in water. Thus, in this study, for the first time, cellulose nanocrystals (CNCs) were successfully used to prepare CNFs aqueous dispersions, referred to as inks, at CNF concentrations up to 0.7 g L−1. As a proof of principle, these inks were then integrated into a cotton fabric using a facile dip coating and drying strategy, resulting in an e-textile with a negative Seebeck coefficient. Furthermore, a theoretical model was developed to describe the nonlinear Seebeck coefficient of the nanocomposite textile, shedding light on the physics governing the electrical conductivity and Seebeck coefficient over a temperature range from 30 °C to 100 °C. These promising results pave the way towards the development of environmentally friendly and durable CNF aqueous dispersions and wearable e-textiles.