Optimization of direct ink writing parameters for carbon-based functional sensors: a study on printability and electrical performance

Purpose The aim of this study is to improve printability by studying the effects of ink’s viscosity, pattern width and length and the process parameters of direct ink write (DIW) technique on the printed carbon patterns for applications in functional sensors and devices. The primary focus is to understand the effects of all the possible parameters, including rheological and geometrical characteristics associated with direct ink writing of conductive carbon and their effects on the performance of the printed pattern, followed by their optimization for desired applications. Moreover, the research work seeks to draw a relationship accounting for the influencing parameters to improve printability and performance. Design/methodology/approach The research performed a comprehensive analysis of ink’s rheological characteristics, geometrical attributes and process parameters on the performance of DIW printed carbon. The rheological characteristics involve the viscosity and shear thinning effects on the process parameters and their fine-tuning. Moreover, the viscosity reduction was carried out to study the effects on printing parameters. Response surface modeling technique was adopted to statistically determine the significant parameters and their effects on the printed patterns. Furthermore, a lab-developed setup was used to realize samples, followed by a detailed study of the effects of each parameter on the pattern width and resistance. The experiments were performed for both pristine and reduced viscosity carbon paste, and the results were compared. Furthermore, the length of the pattern was varied, and the effects were recorded to conclude the study. Findings The research findings concluded establishing a relationship between the ink’s rheological characteristics, geometrical attributes and process parameters of the DIW technique to improve printability and electrical performance of printed functional devices of carbon ink. The statistical analysis carried through highlights extrusion pressure and print speed as the most significant process parameters for a given viscosity, and their optimization is dependent on the required output performance. The viscosity reduction significantly reduced the required extrusion pressure and enhanced print speed without altering the electrical characteristics. It was found experimentally that pattern width is influenced by printing parameters, which are associated with electrical characteristics. Furthermore, the results showed that the printed patterns obey Ohm’s law in terms of increased length at a fixed increment. Originality/value The study provides the very first comprehensive and systematic analysis of the critical impacts of rheological characteristics, geometrical attributes and process parameters of DIW of conductive carbon for applications in functional sensors and devices. The combination of statistical and experimental aspects of the study establishes a definitive, optimized printing window, moving ahead of qualitative aspects, thus providing a quantitative framework for the fabrication of stable, high-performance carbon-based devices via DIW. The printing window will ensure reproducibility and enhancement in the performance of carbon-based sensors fabricated through DIW, thus enabling robustness and cost-effectiveness.