Adhesive contact of cylindrical lens and a flat sheet

Methods are developed to estimate the adhesion and surface free energies of compliant materials from the contact deformations of cylindrical lenses with flat sheets. Some important differences are found between the cylindrical contact studied here and the widely studied geometry of spherical contact. For example, while the pull-off force is completely independent of the elastic constants (K) of the materials for spherical contacts, the pull-off force for cylindrical contact is proportional to K1/3. Furthermore, for cylindrical contacts the contact width at separation reaches to a value of 39% of the width (a0) at zero load, whereas the corresponding value is 0.63a0 for spherical contact. The feasibility of using cylindrical contacts to estimate the surface and adhesive energies of polymers was investigated using elastomeric polydimethylsiloxane (PDMS) as a model system. PDMS was used in two ways: (1) unmodified and (2) with its surface hydrolyzed with dilute hydrochloric acid. Significant hysteresis of adhesion was observed with the hydrolyzed PDMS surfaces due to H-bonding interactions, which appeared to depend on normal stress.

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