Substrate stiffness affects particle distribution pattern in a drying suspension droplet

Abstract

The complexities involved in achieving a tailor-made evaporative deposition pattern have remained a challenge. Here, we show that the morphological pattern of drying suspension droplets can be altered by varying substrate elastic modulus E. We find that the particle spot diameter and spacing between the particles scale with substrate stiffness as d s ∼ E - 0.15 and s ∼ E - 1.23, respectively. We show that the larger spot diameter and spacing between particles on a softer substrate are attributed to a higher energy barrier U associated with stronger pinning of the contact line. The particle deposition pattern is characterized in terms of deposition index, I d, whose value is < 0.50 and >0.75 for centralized (multilayer) and uniform (monolayer) deposition patterns observed for stiffer and softer substrates, respectively. The outcome of the present study may find applications in biochemical characterization and analysis of micro-/nanoparticles.