Contact dynamics in the adhesion process between spherical polydimethylsiloxane rubber and glass substrate

Area of Science:

• Soft Matter Physics
• Materials Science
• Surface Science

Background:

• Understanding contact mechanics is crucial for soft materials.
• Micron-scale interactions present unique challenges in adhesion and deformation.
• Existing models require validation for dynamic contact scenarios.

Purpose of the Study:

• To experimentally investigate the contact dynamics of a soft sphere on a rigid substrate at the micron scale.
• To analyze the influence of loading and unloading cycles on contact parameters.
• To validate theoretical models against experimental observations.

Main Methods:

• Simultaneous measurement of contact radius, contact angle, and force during loading/unloading.
• Experimental setup designed for micron-scale soft sphere-rigid substrate interactions.
• Analysis using the extended Johnson-Kendall-Roberts (JKR) theory.

Main Results:

• Contact dynamics showed minimal effect from repeated cycles.
• Contact angle exhibited dynamic changes, with constant advancing and receding angles observed.
• The extended JKR theory accurately predicted force curves when using experimentally derived apparent surface energy.
• Apparent surface energy correlated with contact line velocity, aligning qualitatively with Greenwood-Johnson predictions.

Conclusions:

• The extended JKR theory provides a robust framework for modeling soft sphere-rigid substrate contact.
• Apparent surface energy is a key parameter influenced by contact line velocity.
• Modifications to existing theories may be necessary for scenarios involving changes in contact line velocity direction.