Manipulating the three-phase contact line of an evaporating particle-laden droplet to get desirable microstructures: A lattice Boltzmann study

The lattice Boltzmann method (LBM) is used to study a novel inkjet printing scheme for making three-dimensional (3D) microstructures from evaporating droplets laden with the nanoparticles. The scheme involves pinning the three-phase contact line (TCL) on the specific points of a chemically heterogeneous pattern, leading to an asymmetric retraction of the TCL and a corresponding particle deposition morphology. A simple isothermal LBM model incorporating diffusion-limited evaporation, contact line pinning, and an Eulerian treatment of particles is employed to study the said scheme. The results show that TCL retraction plays a significant role in determining the final shape of the pattern when the particle concentration is low (<1wt: %), enabling a pure liquid approach to approximate the deposition. For the particle Peclet number greater than one, the coffee-ring effect leads to undesirable non-uniform deposits close to the pinning regions. Increasing the pattern dimensions and the surface energy difference between the pattern and the substrate result in a more stereoscopic morphology. The shape of the pattern and the pinning points can be altered to control the shape and the dimensions of the final 3D microstructure. A premature unpinning of the pure liquid drop is observed at the sharp edges of the pinning points owing to the higher contact line curvature in that region. Published under an exclusive license by AIP Publishing.

Automated summary

The lattice Boltzmann method is used to study a novel inkjet printing scheme for making three-dimensional microstructures, with the ability to control particle deposition patterns by pinning the three-phase contact line at specific points. Low particle concentrations play a significant role in determining the final shape, enabling a pure liquid approach to deposition. The coffee-ring effect and surface energy differences can impact the morphology, with the ability to alter the shape and dimensions of the microstructure by changing the pattern and pinning points.