Observation and simulation of microdroplet shapes on surface-energy- patterned substrates: Contact line engineering for printed electronics

Abstract

Equilibrium microdroplet shapes on hydrophilic/hydrophobic patterned surfaces were investigated both by experimental observation using an inkjet printing technique and by computer simulation. We demonstrated that the hybrid energy minimization simulation can accurately reproduce the equilibrium shapes of observed microdroplets, including the droplet contact line in the vicinity of a sharp corner in the hydrophilic region. We found that the relative ratio of nonwetting areas by the droplets around a rectangular corner can be used as a useful index to check the reliability of the simulation as well as to estimate the surface-energy distribution within the hydrophilic region. Based on the estimation of the additional local force acting on the contact lines, we discuss the design rules for printed electronics circuits, such as the shapes of the integrated electrode to realize the ideal spreading. © 2013 Author(s).