The behavior of the liquid drops on the soft surfaces during condensation has been intriguing due to the viscoelastic nature of the substrates. The effects of viscoelastic characteristics during condensation are poorly understood due to the substrate’s deformability, which is influenced by elastic and interfacial tension forces acting at the solid-liquid interface. The rheology of soft substrates plays a significant role during condensation, influencing several processes such as droplet growth, drop coalescence, contact line motion, and wetting ridge dynamics. This study investigated these condensation processes on soft polydimethylsiloxane (PDMS) substrates with varying shear moduli. We observed a higher drop coverage fraction and an average condensate drop size on the soft surface with a low shear modulus magnitude. Regardless of the shear moduli of the PDMS substrates, the relaxation time of coalescing drops follows a linear trend with the drop equilibrium size, with the magnitude being higher for softer substrates.
In addition, coatings of viscous oil or viscoelastic polymer on a rigid surface transform the condensation phenomena differently. When the viscous oil is infused on low-energy rigid surfaces, the surface shows excellent water repellent behavior. On the other hand, the viscoelastic material coating exhibits a high affinity with water drop resulting in more contact angle hysteresis (CAH). We focused on the drop coalescence phenomena during condensation on viscous slippery and viscoelastic coated metallic samples in this work. We observed that the drop coalescence on lubricant infused surfaces (LIS) significantly depends on the viscosity of the lubricant and the stability of droplet interface bilayers between the drops. Coalescence induced motion during condensation was significantly observed in high viscous liquid infused surfaces (50 cst and 500 cst) compared to low viscous liquid infused surface (5 cst). Key findings of this work would be helpful to comprehend the drop coalescence phenomena on viscous slippery and viscoelastic coatings in a detailed manner.