Fiber wobbling method: novel method for measuring rheological properties of molecularly thin liquid films

A novel method for measuring dynamic shear force at a high shear rate with precise gap control has been developed to clarify the rheological properties of confined perfluoropolyether lubricant. We call this new method "fiber wobbling method". In this method, an optical fiber is used as a probe and measuring amplitude and phase shift of the fiber shearing a lubricant film provides the rheological properties. The fiber wobbling method requires highly sensitive force sensing due to the small shear force generated by thin liquid films. In this paper, we present an outline of the fiber wobbling method and a highly sensitive shear force measurement method that can provide a minimum detection force of the order of 10 pN. The method will be a useful in designing head-disk interfaces of high-density hard disk drives.