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Adhesion of particles with sharp edges to air-liquid interfaces
Javed Ally1, Michael Kappl, Hans-Jürgen Butt
1Max Planck Institute for Polymer Research, Mainz, Germany. ally@mpip-mainz.mpg.de
Langmuir : the ACS Journal of Surfaces and Colloids
|July 4, 2012
Summary
Sharp edges on particles significantly alter adhesion to air-liquid interfaces by pinning the contact line. This eliminates contact hysteresis, making adhesion dependent on particle wettability and edge geometry.
Area of Science:
- Colloid and Surface Science
- Materials Science
- Physics of Interfaces
Background:
- Solid particle adhesion to air-liquid interfaces is crucial in various industrial and natural processes.
- The role of particle geometry, particularly sharp edges, in adhesion phenomena is not fully understood.
- Understanding these interactions is key to controlling particle behavior in multiphase systems.
Purpose of the Study:
- To investigate the influence of sharp edges on solid particle adhesion to air-liquid interfaces.
- To quantify the effect of modified particle geometry on adhesion forces and contact angles.
- To elucidate the relationship between particle wettability, edge geometry, and adhesion.
Main Methods:
- Spherical colloidal probes were modified with a circumferential cut using focused ion beam milling.
- The colloidal probe technique was employed to study particle interactions with water drops and bubbles.
- Force curves were analyzed to measure adhesion forces and contact angles.
Main Results:
- The presence of a circumferential cut (sharp edge) on particles caused the contact line to pin at the edge.
- Contact hysteresis between approach and retraction force curves was eliminated for modified particles.
- The contact angle at the edge exhibited a range of values, bounded by the Gibbs inequality.
- Adhesion force was found to be dependent on both particle wettability and the geometry of the introduced edge.
Conclusions:
- Sharp edges fundamentally alter the adhesion mechanics of particles at air-liquid interfaces.
- Edge pinning eliminates contact angle hysteresis, simplifying the adhesion model.
- Adhesion force is a direct consequence of particle wettability and the specific geometric features of the particle's edge.
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