An Integrated Magnetic Actuation System for High-Speed Atomic Force Microscopy

High-speed atomic force microscopy enables in situ studies of dynamic phenomena at the nanometer-scale. This paper presents the design, fabrication, and evaluation of an integrated magnetic actuation system for high-speed atomic force microscopy. The proposed system consists of a microcantilever probe with an attached permanent magnet particle and a microactuator for generation of magnetic field. Novel geometries are proposed for the probe, the magnetic particle, and the actuator that together result in a high bandwidth and adequate actuation gain. A lumped parameter model is developed for the probe's dynamics and employed to optimize its design. Subsequently the integrated actuation system has been fabricated and evaluated. The actuator has been shown to generate actuation fields as high as 216 G with associated temperature rise of less than 8 °C. The probe has been evaluated to have an Eigen-frequency of 104 kHz with an actuation gain of 1 nm/G in air. Characterization of the probe in water reveals the reduction in Eigen-frequency to be merely 23%, which is nearly 3-fold less than that of a conventional probe. Finally, the developed actuation system has been employed to perform high-speed dynamic mode imaging of a grating inside aqueous medium at various imaging rates up to 1.25 frames/s.