Active atomic force microscopy cantilevers for imaging in liquids

We make an atomic force microscopy (AFM) cantilever oscillate by having an ac current circulating along it. When interacting with a permanent magnet, a normal force acts on the magnetic loop formed this way and induces its vibration. By choosing the current frequency at the resonance of the spring, this effect can be used for imaging in fluids in intermittent contact mode as demonstrated by an image of actin filaments in buffer. These active cantilevers can also be used in dc mode to reach a static position; they should be suitable for a parallel control of multiple probes. (C) 2001 American Institute of Physics.