Novartis AG
Method and apparatus for determining a coefficient of friction at a test site on a surface of a contact lens

Abstract:

The present invention relates to a method and an apparatus (5) for determining a coefficient of friction at a test site (11) on a surface (10) of a contact lens (1). The apparatus comprises: a lens holder (2) arranged at least partially in a receptacle (6); a slide (4) comprising a counter surface (40) made of lapped aluminum for contacting the test site (11); a load generator (7) configured to apply a predetermined normal load (Fn) between the counter surface (40) and the test site; a drive (8) configured to generate a sliding movement between the counter surface (40) and the contact lens in direction located in a plane perpendicular to the normal load (Fn); and a force sensor (9) configured to measure a tangential frictional force (Ft) between the test site and the counter surface (40) along the direction of the sliding movement.