Near-field optical microscopy with a vibrating probe in aqueous solution

We show that with an appropriately configured scanning quartz pipette coate d with aluminum, a near-field scanning optical microscope (NSOM) can be con structed to operate in aqueous solution for applications in biology. Many o f the technical limitations associated with a scanning pipette were circumv ented by introducing a small modulation of the distance between the pipette and the sample. We show that this ac method allows the pipette to be posit ioned very close to the sample surface and is robust in obtaining reproduci ble NSOM images in solution. This approach is also compatible with fluoresc ence imaging and fluorescence resonance energy transfer, and should further facilitate the use of NSOM in various areas of cell biology where high res olution is considered to be critical. (C) 2001 American Institute of Physic s.