Investigating the reliability and dynamic response of fully 3D-printed thermistors

<p dir="ltr">This paper investigates the measurement capability, dynamic response, and mechanical reliability of all 3D-printed multi-material thermistors. The thermistor design consisted of three main components: a polycarbonate (PC) substrate, a silver (Ag) electrode pair, and a poly(3,4-ethylenedioxythophene):poly(4-styrenesulfonate) (PEDOT:PSS) thermosensitive layer. The thermistors were fabricated using two manufacturing techniques: fused deposition modeling (FDM) for the substrate and micro-dispensing for the Ag and PEDOT:PSS films. Two designs with different sensing areas, D1 (90 mm²) and D2 (54 mm²), were fabricated. As the indicator of measurement capability, the highest thermal indexes were recorded as 905.64 and 813.03 K for D1 and D2 thermistors, respectively. Thermistors exhibited comparable dynamic performance, with normalized resistance variations ranging from 0.96 to 1 for temperature changes between 25 and 45 °C. The sensing area influenced both measurement capability and dynamic performance, where larger sensing areas enhanced measurement capability but extended the time required to complete dynamic cycles, around 400 s for D1 versus 350 s for D2. Adhesion tests revealed a strong bonding between the PEDOT:PSS and Ag layer with less than 5% material removal. However, the adhesion of the PEDOT:PSS to the PC substrate was weak, with over 65% material removal. Morphological analysis indicated that the poor adhesion was caused by suboptimal surface properties of the 3D-printed substrate, even resulting in gaps between these two surfaces. This study demonstrates that our all 3D-printed multi-material thermistors can match reported measurement performance with an acceptable dynamic performance while highlighting the need to improve 3D-printed substrate surface properties to enhance the performance of such multi-material structures.</p>