Elastic and Brush-Paintable Organic Ternary Thermoelectric Composites for Dual-Functional Wearable Sensors

The development of wearable thermoelectric (TE) sensors necessitates materials that combine high TE performance with exceptional mechanical compliance and scalable processability. Herein, we present a ternary TE composite composed of single-walled carbon nanotubes (SWCNTs), carboxymethyl cellulose (CMC), and waterborne polyurethane (WPU), formulated as a water-processable and paintable ink for direct application onto arbitrary flexible substrates. In this composite, SWCNTs form the primary TE network, CMC stabilizes their dispersion, and WPU imparts excellent mechanical softness and elasticity. The modulation of WPU content enables systematic tuning of both TE parameters and mechanical properties, allowing the ternary composites to maintain stable TE performance under highly stretched conditions. As a result, we demonstrate dual-functional sensing capability with reliable resistance-based monitoring of joint motion and TE detection of temperature stimuli. These results position our organic ternary composite as a scalable and versatile platform for next-generation multifunctional wearable TE electronics.