Flexible and Stretchable Self-Powered Multi-Sensors Based on the N-Type Thermoelectric Response of Polyurethane/Nax(Ni-ett)n Composites

Flexible and stretchable electronic devices have a broad range of potential uses, from biomedicine, soft robotics, and health monitoring to the internet-of-things. Unfortunately, finding a robust and reliable power source remains challenging, particularly in off-the-grid and maintenance-free applications. A sought-after development overcome this challenge is the development of autonomous, self-powered devices. A potential solution is reported exploiting a promising n-type thermoelectric compound, poly nickel-ethenetetrathiolates (Na-x(Ni-ett)(n)). Highly stretchable n-type composite films are obtained by combining Na-x(Ni-ett)(n) with commercial polyurethane (Lycra). As high as 50 wt% Na-x(Ni-ett)(n) content composite film can withstand deformations of approximate to 500% and show conductivities of approximate to 10(-2) S cm(-1) and Seebeck coefficients of approx. -40 mu V K-1. These novel materials can be easily synthesized on a large scale with continuous processes. When subjected to a small temperature difference (<20 degrees C), the films generate sufficient thermopower to be used for sensing strain (gauge factor approximate to 20) and visible light (sensitivity factor approximate to 36% (kW m(-2))(-1)), independent of humidity (sensitivity factor approximate to 0.1 (%RH)(-1)). As a proof-of-concept, a wearable self-powered sensor is demonstrated by using n-type Na-x(Ni-ett)(n)/Lycra and PEDOT:PSS/Lycra elements, connected in series by hot pressing, without employing any metal connections, hence preserving good mechanical ductility and ease of processing.