# Investigating the Reliability and Dynamic Response of Fully 3D-Printed Thermistors
## 3 Results and Discussion  
The thermal index is a key parameter that reflects the measuring capability of thermistors with higher values providing better measurement capability and better temperature stability. The calculated thermal indexes of manufactured thermistors at different temperatures are demonstrated in Table 3 and summarized in Figure 4. Both thermistors exhibited changes in their \(\beta\) values with temperature changes during both heating and cooling, with higher \(\beta\) values recorded at lower temperatures. The highest calculated thermal indexes were 905.64 K and 719.48 K for D1 thermistors and 813.03 K and 691.60 K for D2 sensors, for heating and cooling, respectively. Given that high \(\beta\) values indicate improved temper  
Figure 3: The illustration of the adhesion test specimens. (**a**) The cross-section of the thermistor clearly shows that the sensing layer had direct contact with both the electrode (red circle) and the PC substrate (red rectangle), (**b**) PEDOT:PSS on silver film, and (**c**) PEDOT:PSS on PC substrate. ature stability and measurement capability [39], the proposed thermistors fabricated on substrates fabricated from PC demonstrated a satisfactory level of measurement capability. This is evident when compared to commercial thermistors, which typically achieve \(\beta\) values exceeding 1000 K [39; 41]. Furthermore, with an increase in temperature, there was a decrease in thermal indexes, which was a result of the semiconductor-like nature of PEDOT:PSS that exhibited negative temperature coefficient (NTC) behavior, as previously shown by [PERSON] et al. [8]. Further interpretation of Figure 4 shows that D1 thermistors exhibited slightly better measurement capability compared to D2 thermistors. This can be attributed to their larger sensing area, which enhanced measurement capability. Furthermore, the consistency analysis of \(\beta\) values across temperature intervals reveals notable differences in thermistor behav  
Figure 4: Thermal indexes over temperature. (**a**) D1 and (**b**) D2 thermistors. \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multirow{2}{*}{**Temperature Range**} & \multicolumn{2}{c}{**D1**} & \multicolumn{2}{c}{**D2**} \\ \cline{2-5}  & **Heating** & **Cooling** & **Heating** & **Cooling** \\ \hline
25–27 & 905.64 \(\pm\) 16.20 & 719.48 \(\pm\) 14.75 & 813.03 \(\pm\) 44.00 & 691.60 \(\pm\) 17.40 \\
27–29 & 852.28 \(\pm\) 26.04 & 5  
ior between D1 and D2, as well as between heating and cooling cycles, as demonstrated by the percentage errors presented in Table 4. Overall, thermistors had low inconsistency in the measurement capability during heating compared to cooling. Regardless of the thermal cycle, thermistors were more inconsistent at lower temperatures. For instance, D1 thermistors demonstrated improved consistency after 31 \({}^{\circ}\)C, while D2 thermistors stabilized after approximately 33 \({}^{\circ}\)C. This behavior can be attributed to the initial measurement drift caused by transient conditions as the thermistors equilibrated with the environment [8]. As the temperature increased, these inconsistencies diminished, reflecting a reduction in the influence of environmental and material-related fluctuations. The improved stability at higher temperatures suggests that both thermistors perform more reliably under steady thermal conditions. Similar results have been reported in previous research [42; 43]. The dynamic measurement performance of the thermistors was evaluated over three consecutive heating and cooling cycles by analyzing changes in normalized resistance. The results are presented in Figure 5, depicting the relationship between chamber temperature and normalized resistance variation over time.