Printed Thermoresistive Carbon and PEDOT:PSS Temperature Sensors on Different Substrates

Printed thermoresistive sensors are strongly influenced by the sensing material, substrate, printing process and encapsulation. In this work, PEDOT:PSS temperature sensors were fabricated by inkjet printing on PET and glossy paper, while carbon-based sensors were produced by screen printing on the same substrates. Their morphology, chemical and thermal characteristics, electrical properties, impedance response and thermoresistive performance were systematically compared. PEDOT:PSS exhibited a pronounced substrate dependence: sheet resistance increased from 57.93 ± 13.88 Ω/sq on PET to 5804.75 ± 1732.37 Ω/sq on paper, accompanied by a change from PTC behaviour on PET to NTC behaviour on paper. TCR values changed from +0.176 ± 0.012% °C−1 on PET to −0.594 ± 0.049% °C−1 on paper. In contrast, carbon sensors retained PTC behaviour on both substrates, with TCR values of +1.168 ± 0.093% °C−1 on PET and +1.002 ± 0.097% °C−1 on glossy paper in the unencapsulated condition. Encapsulation reduced the magnitude of the PEDOT:PSS response on both substrates, while for carbon, this effect was directly assessed only on glossy paper, where TCR decreased from +1.002 ± 0.097 to +0.510 ± 0.014% °C−1. The results demonstrate that the combined ink–substrate–printing-process system is decisive in determining the temperature response of printed sensors.