Nanoparticle Deposition Morphology Adjustments by Effects of Time Integration of Nanoparticle Deposition Kinetics in Drying of a Sessile Nanosuspension Microdroplet.

Nanoparticle deposition from a dried sessile microdroplet has important applications in printing and manufacturing. However, the various morphologies of the nanoparticle depositions in existing experiments could not be fully explained based on the traditional deposition criteria, which neglect the nanoparticle deposition kinetics effect. The mystery is resolved herein by simulating nanosuspension microdroplet evaporation based on the pseudopotential phase-change lattice Boltzmann method, incorporating the impact of the time integration of nanoparticle deposition kinetics and deposition front surface wettability. The simulated morphologies of the four typical deposition patterns ("coffee-ring", "coffee-eye", "dome-like" and uniform) on a hydrophilic surface and the tall conical "pillar" on a hydrophobic surface are shown in agreement with existing experimental data. The morphologies of these four typical nanoparticle deposition patterns formed on a hydrophilic surface are found to be governed by two dimensionless characteristic parameters: Peclet number and a new dimensionless parameter Ti that describes the effects of time-integration of nanoparticle deposition kinetics on the deposition morphologies. A decrease in Ti leads to a more apparent "dome-like" pattern formed inside the deposition; otherwise, a more "uniform" pattern is formed inside the deposition. On the other hand, an increase of Peclet number leads to a higher altitude deposition edge, and with a lower-altitude deposition edge on the contrary. This study also paves the way for adjusting evaporation-induced nanoparticles' self-assembly morphologies at a much lower cost and in an easier approach, without traditionally applying sophisticated external fields or multicomponent additives.