Reduction of the damping on an AFM cantilever in fluid by the use of micropillars.

In single molecule force measurements with soft atomic force microscope (AFM) cantilevers, the force sensitivity is limited by the Brownian motion of the cantilever. When a cantilever is close to the surface, the hydrodynamic interaction between the cantilever beam and the surface, called the "squeezing effect", becomes significant, and the resonance peak of the thermal oscillation of the cantilever is heavily broadened and shifted to lower frequency which makes it difficult to eliminate the thermal noise by low-pass filtering. In this study, we propose an easy and low-cost method to improve the force sensitivity. We demonstrate that by bringing a tip of a cantilever onto the edge of a micropillar structure a significant reduction of the damping and an enhancement of force sensitivity are achieved.