Self-modifying percolation governs detachment in soft suction wet adhesion

Area of Science:

• Biophysics
• Fluid Dynamics
• Adhesion Science

Background:

• Aquatic animals like octopuses utilize soft suction cups for wet attachment on rough surfaces.
• Conventional models describe detachment as smooth drainage governed by Reynolds-type pressure gradients.

Purpose of the Study:

• To investigate the fluid dynamics and pressure changes during suction cup detachment.
• To challenge the conventional understanding of wet adhesion and detachment mechanisms.

Main Methods:

• Combining spatiotemporal pressure mapping with confocal imaging of the fluid interface.
• Analyzing the fluid layer between the suction cup and substrate during detachment.

Main Results:

• A two-stage, nonequilibrium pathway for pressure equalization was revealed, challenging the conventional view.
• Suction-induced elastic deformation dynamically remodels the interfacial fluid, creating a self-coupled pressure channel system.
• Stage I involves an invasion-percolation suction front, followed by global network opening and classical Poiseuille drainage in Stage II.

Conclusions:

• The detachment mechanism is a self-modifying percolation where flow remodels its own pathways.
• This finding advances the understanding of biological suction and viscous adhesion.
• The study suggests design principles for durable wet adhesives and hydrogel microfluidics.