Patent ID: 8549660

Claim:
An apparatus, comprising: an optical detector configured to detect an optical beam reflected from a cantilever; an optical fiber probe, wherein the optical fiber probe is affixed to and suspended from the cantilever; a piezotube configured to move a sample substance immersed in a liquid in proximity to the optical fiber probe, wherein the optical fiber probe has a first end that is immersed in the liquid and a second end that is affixed to the cantilever, and the cantilever and the second end of the optical fiber probe are positioned outside of the liquid, and further wherein the cantilever is configured to deflect in response to an interfacial force between the sample substance and the optical fiber probe; a feedback controller communicatively coupled to the optical detector and to a semiconductive circuit element abutting at least one surface of the cantilever, wherein: in response to detecting a movement of the optical beam reflected from the cantilever, the feedback controller is configured to apply a voltage to the semiconductive circuit element; in response to the voltage from the feedback controller, the semiconductive circuit element is configured to reduce deflection of the cantilever; and the voltage applied by the feedback controller is indicative of a strength of the interfacial force between the sample substance and the optical fiber probe.