Direct Ink Writing of SiC-Fe3O4-Polymer Nanocomposites for Magnetic Humidity Sensors: Rheology Characterization

Abstract This paper presents the 3D printing of novel SiC-Fe3O4 nanocomposites for humidity sensor application via the Direct Ink Writing method. 3D printing is a transformative manufacturing technology that has achieved notable advancements in fabricating complex polymer-ceramic nanocomposite structures that exhibit enhanced properties for various applications. Within the complex framework of additive manufacturing (AM), extrusion-based techniques such as the direct ink writing (DIW) method, significantly contribute to broadening the range of 3D-printable materials with unconventional structures, particularly for sensors. Considering the versatility of the DIW method in developing sensing systems, silicon carbide (SiC)-polymer nanocomposites have garnered substantial attention due to their promising properties for humidity sensing applications. Humidity sensors play a crucial role in human comfort and health, energy efficiency, enhancing product quality by protecting valuable equipment, etc. Therefore, the combination of polymer-ceramic nanocomposites with DIW produces highly sensitive sensors with accurately engineered mechanical properties. However, the DIW process requires careful consideration of the nanocomposite ink to ensure compatibility with the extrusion and deposition process. This study investigates a novel 3D-printable ink based on SiC-polymer nanocomposites for the DIW process. The inks are composed of SiC and magnetite (Fe3O4) particles dispersed within a polyvinyl alcohol (PVA) matrix. The printability including extrudability and viscoelasticity of the inks was thoroughly evaluated for proper flow through the nozzle and rapid shape recovery of the ink after deposition. In addition, DIW process parameters were optimized to print an interdigitated pattern for humidity sensing. It was observed that the same SiC and Fe3O4 ratio provided the best rheological behavior and was successfully 3D printed with high printing accuracy without any defects. Besides the rheological behavior, DIW process parameters were optimized to print an interdigitated pattern for humidity sensing.