Analysis of Superfine-Resolution Printing of Polyaniline and Silver Microstructures for Electronic Applications

Additive manufacturing (printing) of micrometer-scale patterns of metal and semiconductor particles is receiving significant attention due to its potential as an inexpensive alternative to the top-down fabrication of silicon microelectronic devices. However, printing of such devices needs an in-depth understanding of physico-chemical interactions between the liquid ink droplets and the substrate used for printing the devices. The paucity of detailed experimental studies in this area warrants a systematic investigation into the challenges involved in printing stable and reliable electronic devices. In this paper, we have analyzed the interactions between the liquid dispersions of polyaniline emeraldine salt (PANI-ES) and silver nanoparticles (Ag NPs) over various substrates such as silicon, glass, indium tin oxide, polyethylene terephthalate, and polyvinyl alcohol surfaces. The analysis has been carried out in terms of concentration of the dispersion, particle size, solvophilic or solvophobic nature of the substrate, evaporation rate of solvents, ambient humidity, and postprocessing. Furthermore, the resistors of various lengths and widths are printed on glass surface via a superfine resolution molecular printing system (MPS) that uses a piezoelectric response from a cantilever to deposit picoliters of Ag NP ink at precise locations. Substantially, low ratios of printed dot feature size to suspended particle size (1 for PANI-ES and 10 for Ag NP) have been obtained, indicating that the MPS can provide a much finer print resolution for flexible and printed electronic circuit components as compared to traditional inkjet, screen, or gravure printing.