Organic nanocomposite structure tailored by controlling droplet coalescence during inkjet printing

Inkjet printing offers a low-cost, high-throughput avenue for producing functional organic materials through rapid translation of desktop discoveries to industrial roll-to-roll processes. Here, we report a simple, but effective strategy to control droplet coalescence during inkjet printing, as a major variable, to tailor the nanoscale morphology of organic composite materials produced upon evaporation of all-liquid inks. During deposition, the spacing between ink droplets was controlled to systematically vary the extent of droplet coalescence. Our results show that decreasing coalescence increased the solvent evaporation rate, supersaturation of the solutes, and nucleation density of the precipitating organic crystals. This phenomenon was utilized to tailor the average size of pentaerythritol tetranitrate (PETN) crystals dispersed in an adhesive binder matrix from ~0.2 to upwards of 100 μm. The results suggest that controlling the extent of droplet coalescence can be used as an effective means to tailor the composite morphology of printed organic materials at the nanoscale.