Dual-mode temperature monitoring using high-performance flexible thermocouple sensors based on PEDOT:PSS/CNTs and MXene/Bi2Se3

Due to the limited thermoelectric (TE) performance of polymer materials and the inherent rigidity of inorganic materials, developing low-cost, highly flexible, and high-performance materials for flexible thermocouple sensors (FTCSs) remains challenging. Additionally, dual-mode (contact/non-contact) temperature monitoring in FTCSs is underexplored. This study addresses these issues by using p-type (PEDOT:PSS/CNTs, 2:1) and n-type (MXene/Bi2Se3, 2:1) TE materials applied via screen printing and compression onto a PPSN substrate (paper/PDMS/Si3N4). The resulting FTCSs exhibit excellent TE properties: electrical conductivities of 61,197.88 S/m (n-type) and 55,697.77 S/m (p-type), Seebeck coefficients of 39.88 mu V/K and -29.45 mu V/K, and power factors (PFs) of 97.66 mu W/mK(2) and 55.64 mu W/mK(2), respectively. In contact mode, the sensor shows high-temperature sensitivity (S-T = 379.5 mu V/degrees C), a broad detection range (20-200 degrees C), high resolution (similar to 0.3 degrees C), and fast response (similar to 12.6 ms). In non-contact mode, it maintains good sensitivity (S-Tmax = 52.67 mu V/degrees C), a broad detection range, high resolution (similar to 0.8 degrees C), and even faster response (similar to 9.8 ms). The sensor also demonstrates strong mechanical durability, maintaining stable performance after 1000 bending cycles. When applied to dual-mode temperature monitoring in wearable devices and lithium batteries, the FTCS shows high accuracy and reliability compared to commercial K-type thermocouples, indicating significant potential for advanced medical monitoring systems and smart home technologies.