Force detection using a fiber-optic cantilever

A force measurement technique has been developed that utilizes a clamped fiber-optic element both as a cantilever and as a highly sensitive probe of the static and dynamic displacement of a sample that is mounted near its free end. Light from a 1.5 mW superluminescent diode coupled into the fiber is used to detect displacement with 6×10^-13m/ Hz sensitivity for frequencies above 40 kHz. This technique has been used to study the interaction between two gold surfaces by simultaneously measuring the interaction force and contact stiffness as a function of the conductance and elongation of the contact. Excellent correspondence between steps in contact stiffness and electrical conductivity was observed.