Droplet-train induced spatiotemporal swelling regimes in elastomers

Area of Science:

• Polymer Science
• Materials Science
• Fluid Dynamics

Background:

• Understanding elastomer swelling is crucial for applications involving solvent exposure.
• Droplet impingement dynamics can significantly influence material response.
• Previous studies often focused on single droplet impacts or bulk swelling.

Purpose of the Study:

• To investigate the complex swelling dynamics of elastomers subjected to a train of solvent droplets.
• To establish the relationship between time scales, geometric parameters, and observed swelling behaviors.
• To develop and validate a numerical model for predicting localized elastomer swelling.

Main Methods:

• Combined experimental and numerical analysis.
• Time scale analysis to define spatiotemporal regimes.
• Finite element modeling of local swelling.
• Experimental validation using controlled droplet train impingement.

Main Results:

• Identified six cases of localized swelling based on relative timescales and geometric scaling.
• Observed distinct swelling shapes (mushroom, mesa, cap) dependent on lateral dimensions.
• Demonstrated that swelling extent increases with elastomer thickness.
• Showcased temporary geometric features when absorption and droplet train periods are comparable.

Conclusions:

• Elastomer swelling dynamics are highly sensitive to the interplay of solvent absorption and droplet impact frequency.
• Geometric scaling of the elastomer sample (thickness and lateral dimensions) is a key factor in determining localized swelling morphology.
• The developed finite element model accurately predicts observed swelling behaviors and can be used for further exploration.