ADHESIVE CONTACT OF CYLINDRICAL LENS AND A FLAT SHEET

Methods are developed to estimate the adhesion and surface free energi es 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 complet ely independent of the elastic constants (K) of the materials for sphe rical contacts, the pull-off force for cylindrical contact is proporti onal to K-1/3. Furthermore, for cylindrical contacts the contact width at separation reaches to a value of 39% of the width (a(0)) at zero l oad, whereas the corresponding value is 0.63a(0) for spherical contact . The feasibility of using cylindrical contacts to estimate the surfac e and adhesive energies of polymers was investigated using elastomeric polydimethylsiloxane (PDMS) as a model system. PDMS was used in two w ays: (1) unmodified and (2) with its surface hydrolyzed with dilute hy drochloric acid. Significant hysteresis of adhesion was observed with the hydrolyzed PDMS surfaces due to H-bonding interactions, which appe ared to depend on normal stress.