Piezo-resistive behaviour at high strain levels of PEDOT:PSS printed on a flexible polymeric substrate by a novel surface treatment

In this work a conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) thin film was deposited on a treated surface of a flexible substrate using ink-jet printed technique. The novel surface treatment method increased significantly the substrate surface energy (by 45 %) and consequently the thermoplastic polyurethane wettability. SEM and AFM evaluated the thickness uniformity and roughness of the printed ink, respectively. The printed film on the substrate was characterized for the evaluation of its mechanical and electrical properties. The printed substrate presented high flexibility and was able to follow and deform along with the substrate, without breaking or losing adhesion and its conductivity properties at < 60 % strain. The ink piezo-resistive effect was demonstrated and high gauge factors (> 300) were achieved (higher than the typical value for available flexible metallic strain gauges) showing the potential of the material to be used in high strain sensing applications.