PIEZOELECTRICAL SHEAR-FORCE DISTANCE CONTROL IN NEAR-FIELD OPTICAL MICROSCOPY FOR BIOLOGICAL APPLICATIONS

We present a piezoelectrical shear-force distance control setup for sc anning near-field optical microscopy. The setup is compact and tip exc hange is easy. The topographical sensitivity is comparable to optical feedback systems. With an acceptable vibration amplitude of 5-10 nm we obtained a topographical resolution of 5 pm/root Hz. Because there is no laser necessary for tip position feedback, there is no extraneous light to interfere with spectroscopic and other low-light level experi ments. Our technique permits measurements of soft biological samples i n aqueous solution, which opens up many possible applications of near- field optical microscopy in biology and medicine. (C) 1998 Elsevier Sc ience B.V. All rights reserved.