MEMS-Based Nanopositioning for On-Chip Atomic Force Microscopy

An important component of an atomic force microscope is a nanopositioner that moves the sample, relative to the probe, in a raster pattern. A typical AFM nanopositioner is a large, heavy flexure-guided mechanism machined from a solid block of steel or aluminum, with incorporated actuators and displacement sensors. The most widely used actuation technology for nanopositioning is the piezoelectric stack actuator, which can generate a large amount of force with a small stroke. These actuators suffer from nonlinearities such as hysteresis and creep, which are difficult to address using feedforward methods. Furthermore, from an electrical viewpoint, they are large capacitors that require complex and expensive low-noise, linear amplifiers for their operation. There is significant interest in moving away from using piezoelectric actuators in nanopositioning systems.