High-speed serial-kinematic AFM scanner: Design and drive considerations

In this paper, we describe the design of a flexure guided, two-axis nanopositioner driven by piezoelectric stack actuators. The scanner is specifically designed for high-speed scanning probe microscope (SPM) applications. A high-speed atomic force microscope (AFM) is required to acquire high resolution, three-dimensional, time-lapse images of fast processes such as the rapid movement of cells and the diffusion of DNA molecules. High-speed scanner designs have been proposed, for example, by Ando and co-workers as well as Schitter and coworkers, for AFM imaging. In the proposed design, the slow and fast scanning axes are serially connected and both axes are flexure-guided to minimize runout. The achievable scan range is 10 x 10 mum. The scanner´s mechanical resonance frequencies were optimized using finite element analysis. Experimental results show a first major resonance, in the slow and fast axis respectively, at approximately 1.5 kHz and 29 kHz. In addition to evaluating the proposed design, this paper also discusses the various tradeoffs between speed, range, and required control hardware. Electrical requirements and scan trajectory design are also considered.