Wetting and spreading are interesting phenomena closely related to our daily lives (e.g., rain drops on the window, or dew-drops on a lotus leaf). Despite of its ubiquity, there are fundamental questions (e.g. onset of sliding drops) still lack of a thorough understanding.  Taking the advantage of drop-on-demand (DoD) technology originally developed for inkjet printing, we can tune the volume of a sessil drop on a plane or a liquid bridge between two spherical particles in an accurate, reproducible and non-destructive manner, so as to investigate the dynamics of wetting, and particularly the wetting of granular materials.

The motivation is: From the granulation process in chemical engineering, to the jet-binding technology in additive manufacturing (3D printing), one of the biggest challenges associated with the process is the lack of knowledge on liquid mediated particle-particle interactions, which crucially determine the quality of the final product (e.g. rigidity).

The goal is to take the advantage of DoD technology to understand wetting phenomena.

• Onset of motion of a sliding drop on a tilted plane: Inflation vs. inclination.
  

• Wetting mediated assembly of wet granular particles.