Aerosol Jet Printing of Superhydrophobic Surfaces.

A method for creating superhydrophobic surfaces is presented by aerosolizing polymer solutions into micrometer‐sized droplets and converting them into microgel particles during spatially controlled deposition using an aerosol jet printer. The polymer solutions are composed of marginally hydrophobic disulfide‐polydimethylsiloxane (DS‐PDMS) in three solvents with varying vapor pressures. The experiments, combined with an analytical model, demonstrate that solvents with high vapor pressures evaporate from the droplets during flight from the printer nozzle to the substrate. This evaporation increases the DS‐PDMS volume fraction in the droplets above the polymer gelation threshold. As a result, the droplets transform into microgel particles. This transformation leads to the formation of rough, superhydrophobic surfaces. Conversely, solvents with lower vapor pressures do not evaporate sufficiently, preventing DS‐PDMS volume fraction from reaching the gelation threshold. These droplets coalesce upon deposition, producing smooth surfaces with hydrophobicity similar to intrinsic DS‐PDMS. Heating the surfaces to 90 °C or above eliminates superhydrophobicity by de‐gelling the DS‐PDMS, allowing droplet coalescence. Potential applications of this method include droplet manipulation, microreactors for reactant mixing, water‐oil separation, and retardation of droplet evaporation. [ABSTRACT FROM AUTHOR]