Fabrication of conductive paths on a fused deposition modeling substrate using inkjet deposition

Purpose-The purpose of this paper is to explore the possibility of integrating inkjet printed circuitry with fused deposition modeling (FDM) structures to produce embedded electronics and smart structures. Several of the challenges of combining these technologies are identified, and potential solutions are developed. Design/methodology/approach-An experimental approach is taken to investigate some of the relevant physical processes for integrating FDM and inkjet deposition, including the printing, drying and sintering processes. Experimental data are collected to assist understanding of the problems, and engineering solutions are proposed and implemented based on the gained understanding of the problems. Findings-Three challenges have been identified, including the discontinuity of the printed lines resulting from the irregular surface of the FDM substrate, the non-conductivity of the printed lines due to the particle segregation during the droplet drying process and the slow drying process caused by the "skinning effect". Two engineering solutions are developed for the discontinuity problem. The non-conductivity issue and the slow drying process are attributed to the motion of the nanoparticles caused by the evaporation flow. The thermally activated drying process for the Cabot ink suggests that the proposed solution is effective. Timescale analysis and experimental data show that the printing conditions do not have a clear influence on the conductivity of the printed lines, and drying and sintering processes are more important. rarch limitations/implications-No quantitative model has yet been developed for simulating the printing, drying and sintering processes sociated with inkjet printing on FDM substrates. Quantitative models can be extremely valuable for improvement in understanding the problems, optimizing the proposed solutions and coming up with better solutions. Practical implications-The research findings in this work have great implications in implementing a hybrid FDM-inkjet deposition machine for fabricating embedded electronics and smart structures. All the proposed engineering solutions for the identified problems can be potentially integrated into one machine. Social implications-The success of the integration of the FDM and inkjet deposition process will enable the design of compact electro-mechanical structures to replace the large heavy electro-mechanical systems. Originality/value-This work represents one of the first attempts for integrating inkjet deposition of silver nanoparticle inks with the FDM process for making compact electro-mechanical structures. Three critical challenges are identified, and corresponding engineering solutions are proposed and implemented based on analysis of the relevant physical processes, including the printing, drying and sintering processes, which has laid the foundation for integrating the FDM and inkjet deposition processes.