Hydrogen-bonded n-type waterborne polyurethane/lysine/single-walled carbon nanotube ternary composite: Combining excellent thermoelectric and stretchable properties toward self-powered temperature and strain sensors

In recent years, there has been a growing interest in exploring stretchable conductive composites for flexible electronics applications. Organic p-type composites with excellent stretchability and thermoelectric (TE) performance have been widely studied and made great progress. However, organic n-type counterparts remain relatively unexplored. In this work, we introduce green, natural-derived lysine as an n-type dopant and waterborne polyurethane (WPU) as an elastomeric polymer in single-walled carbon nanotubes (SWCNTs). The hydrogen bonds formed between lysine and WPU contribute to the enhancement of both mechanical and TE properties of the composites. The resultant n-type composite shows a high power factor (94.3 µW m−1 K−2) and good stretchability (28.9%) at room temperature with a WPU content of 50%. To date, this is the most stretchable n-type composite with such a high power factor reported in literature. Moreover, the composite demonstrates excellent temperature resolution and response stability when assembled as a sensor, with a minimum discernible temperature difference far surpassing previous findings. Additionally, self-powered temperature and strain sensors are fabricated to detect the different temperature sources and finger movements, respectively. Our work provides an innovative approach to develop stretchable n-type composites with high TE performance for human–computer interaction and wearable electronics in the future.