Wide-area scanner for high-speed atomic force microscopy

High-speed atomic force microscopy (HS-AFM) has recently been established. The dynamic processes and structural dynamics of protein molecules in action have been successfully visualized using HS-AFM. However, its maximum scan ranges in the X-and Y-directions have been limited to similar to 1 mu m and similar to 4 mu m, respectively, making it infeasible to observe the dynamics of much larger samples, including live cells. Here, we develop a wide-area scanner with a maximum XY scan range of similar to 46 x 46 mu m(2) by magnifying the displacements of stack piezoelectric actuators using a leverage mechanism. Mechanical vibrations produced by fast displacement of the X-scanner are suppressed by a combination of feed-forward inverse compensation and the use of triangular scan signals with rounded vertices. As a result, the scan speed in the X-direction reaches 6.3 mm/s even for a scan size as large as similar to 40 mu m. The nonlinearity of the X-and Y-piezoelectric actuators' displacements that arises from their hysteresis is eliminated by polynomial-approximation-based open-loop control. The interference between the X-and Y-scanners is also eliminated by the same technique. The usefulness of this wide-area scanner is demonstrated by video imaging of dynamic processes in live bacterial and eukaryotic cells. (C) 2013 AIP Publishing LLC.