A high signal-to-noise ratio and high-frequency seesaw cantilever for high-speed atomic force microscopy.

Abstract

The cantilever mediates tip-sample interaction detection in all atomic force microscopes (AFMs). Canonical cantilevers are beams, where length, width, and thickness define the physical properties such as stiffness and resonant frequency, that also mediate laser-reflection to report on cantilever deflection. High-speed AFM (HS-AFM) demands miniaturized cantilevers that are soft and fast, but miniaturized beams reduce laser signal quality. Here, we present a seesaw cantilever with a rigid reflective board oscillating over torsional hinges separating the laser-reflective and mechanical functions. Finite element analysis verified the seesaw mechanism. The board can be optimized for laser-reflection and the shortened distance between tip and hinges enhances the angular sensitivity, while the stiffness is tunable via the hinge dimensions. We detail seesaw cantilever design, fabrication, tip addition, physical equations, and sub-molecular imaging of biological samples. We propose that seesaw cantilevers offer a promising alternative to traditional beam cantilevers for diverse AFM applications.