Fabrication of a sensor based on the FDM-printed CNT/PA6 dielectric layer with Hilbert fractal microstructure

The advancements of fused deposition modeling (FDM) technology have been hindered by the limited variety of available materials, subpar mechanical properties, and inadequate functionality of FDM-produced components. This work involved the development of carbon nanotube (CNT)/polyamide 6 (PA6) filaments, and their thermal behaviors were meticulously examined, laying the groundwork for the FDM process. The influence of CNT content on the mechanical attributes of the filaments and the electrical properties of FDM-printed specimens was thoroughly investigated. Furthermore, the sensing application of the FDM-printed CNT/PA6 dielectric layer with Hilbert fractal microstructure was explored. The findings suggest that the integration of CNT significantly alters the mechanical, electrical, and capacitive sensing characteristics. Compared to pure PA6, the tensile strength of CNT/PA6 with 12 wt% CNT increased by 112%, and the resistivity decreased from 2.31 × 1012 Ω sq−1 to 1.13 × 105 Ω sq−1. Moreover, the sensor fabricated with FDM-printed CNT/PA6 dielectric layers demonstrates long-term operational stability (up to 6000 loading/unloading cycles), high sensitivity (0.0319 kPa−1), rapid response time (60 ms), and broad measurement range (0–900 kPa). The effectiveness of these sensors in detecting finger pressure, finger bending, and speech recognition has been confirmed. This study broadens the scope of materials accessible for FDM and lays the groundwork for additional applications of FDM in sensing.