Stacked Rayleigh-Taylor Instabilities Grow Drops into Soft Stalactitelike Structures

Area of Science:

• Geophysical fluid dynamics
• Materials science
• Soft matter physics

Background:

• Thin film hydrodynamics and solidification create complex natural structures like stalactites and icicles.
• Rayleigh-Taylor instability in Newtonian fluid films on surfaces yields drop lattices.
• The solidification of thin films and its effect on interfacial instabilities are less understood.

Purpose of the Study:

• To investigate pattern formation in solidifying thin elastomer films.
• To explore the iterative coat-flow-cure process for creating novel structures.
• To analyze the structure, shape, arrangement, and deformability of the resulting corrugated structures, termed "flexicles".

Main Methods:

• Coating the underside of a flat surface with liquid elastomer.
• Allowing the liquid film to destabilize and flow under gravity while curing into an elastic solid.
• Iteratively repeating the coat-flow-cure process to build corrugated structures.

Main Results:

• The iterative process generates arrays of solid droplets from initial film destabilization.
• Subsequent iterations lead to the formation of corrugated slender structures named "flexicles" by the authors.
• The study analyzes the interplay of order and chaos in flexicle formation and properties.

Conclusions:

• The coat-flow-cure process offers a method for creating intricate, deformable structures from solidifying thin films.
• Flexicles exhibit a unique combination of order and chaos in their morphology and arrangement.
• Understanding these structures provides insights into geophysical pattern formation and soft matter physics.