Frictional behavior on wrinkle patterns of diamond-like carbon films on soft polymer

Frictional behaviors of wrinkle patterns on a diamond-like carbon (DLC) film coated on a soft polymer were investigated. Wrinkle patterns of the DLC layer were formed due to the large difference in elastic moduli between the DLC film and the soft polymer of polydimethylsiloxane (PDMS) as well as high residual compressive stress in the film. The roughness of wrinkled surfaces varied with the thickness of the DLC films, affecting the frictional behaviors. The coefficient of friction significantly reduced as the thickness of the DLC film increased. For lower thicknesses, slip–stick events and surface damages like fish-scales on the wear track were strongly developed. With an increase of sliding distance, a randomly oriented wrinkle pattern was getting worn on its top surfaces, resulting in an increase of the contact area as well as a coefficient of friction (COF). However, for thicker films simple wear was observed with the lower COF due to DLC nature.

► Wrinkling was tuned by tuning the deposition thickness of hard film on polymer.
► Friction was tuned due to wrinkle roughness by tuning deposition thickness.
► Flattening of wrinkle which increases contact area occurred during wear.
► Decrease in friction protects wrinkled surface from the surface wear.