Capacitive micromachined ultrasonic transducer based integrated actuator for atomic force microscope cantilevers

Abstract

The atomic force microscope (AFM) is a versatile tool for imaging and modifying surfaces on atomic scales. The core of the device is a cantilever beam with a sharp tip. The cantilever usually measures a few hundred microns in length and tens of microns in width. Many imaging or surface modification applications require actuation of this micron scale beam. In this paper, a novel actuation mechanism is introduced. The method uses radiation pressure generated by capacitive micromachined ultrasonic transducers (cMUT). The cMUTs are fabricated on top of the cantilever beams and they operate in the megahertz range generating a DC radiation pressure in the immersion medium such as water or air. The integrated cMUT cantilever system compares favorably with piezoelectric film activated and with non-integrated ultrasonic actuation schemes. The cMUT cantilever does not require any alignment of the actuator to the cantilever. Moreover, it works in air as well as in water and is readily used with parallel cantilever probes. Finally, it is an IC compatible technology solution.