A fluid cell with integrated acoustic radiation pressure actuator for atomic force microscopy

Abstract

The development of a fluid cell with an acoustic radiation pressure (ARP) actuator for atomic force microscopy (AFM) is reported. The ARP actuator uses a zinc oxide thin film transducer fabricated on a silicon substrate to generate acoustic waves in the 120–180 MHz range. These waves are coupled to the liquid and are reflected off of the AFM cantilever exerting radiation pressure to move the AFM cantilevers in the dc-MHz frequency range, providing a fast actuation scheme. Since the ARP actuator is remotely located on the fluid cell, it can be used with virtually any type of cantilever. The design, fabrication, and characterization of the AFM fluid cell with an ARP actuator are discussed and the performance of the device is compared with theoretical predictions. ARP actuator electronics and its integration to a commercial AFM system are described. Tapping mode images and molecular adhesion measurements are presented as illustrative examples.