(539a) Advancing High-Performance Fully Integrated Humidity Sensors: Magnetic Field Directed Direct Ink Writing of SiC-Fe3O4-Polymer Nanocomposites

Humidity sensors play a crucial role in various applications, ranging from environmental monitoring to healthcare and industrial processes. However, achieving high performance and fully integrated humidity sensors remains a significant challenge due to limitations in material flexibility and conventional manufacturing techniques. Polymer matrix composites have drawn great attention in such humidity sensor applications due to their superior material and chemical properties. Moreover, the addition of micro/nano particles as fillers has been proven to enhance the sensor conductivity, magnetic permeability, and strength. Especially semiconductors like Silicon carbide (SiC) have raised substantial attention because of their high mechanical strength, chemical inertness, and good thermal stability.

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. In this study, we propose a material solution and a manufacturing approach utilizing dynamic ink deposition programming coupled with high-resolution 3D printing technology to fabricate a fully integrated high-performance humidity sensor.

We have developed an innovative magnetic field directed DIW (M-DIW) based 3D printing process for printing multi-layer SiC-polymer composites. High-resolution DIW is leveraged to manufacture the sensor with multi-layer geometric patterns across different scales. However, the DIW process requires careful consideration of the nanocomposite ink to ensure compatibility with the extrusion and deposition process. Thus, 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. We investigate the influence of ink composition, printing resolution, and structural design on sensor performance through comprehensive experimental studies and numerical simulations. Our findings pave the way for the development of next-generation fully integrated humidity sensors with applications in various fields, including IoT devices, wearable electronics, and smart infrastructure.