Scanning near-field optic/atomic force microscopy in liquids

Abstract

We report the performance of an optical fiber cantilever and the scanning near-field optical microscopy imaging of specimens in liquid. In our scanning near-field optical/atomic force microscope (SNOAM), the scanning of an optical fiber cantilever over the specimen was controlled by dynamic mode atomic force microscopy to reduce damage to the probe and soft specimens. The typical resonant frequency of the optical fiber cantilever was 25.6, while it was 29.5 kHz in the air. The Q factor of the cantilever depended on the vibration amplitude and showed typically 460–590 in the air and 65–270 in water. The relationship between the vibration amplitude and the average sample-probe separation indicated that the cantilever worked in the non-contact mode in water, while it worked in the cyclic-contact mode in the air. Cultured cells in aqueous solutions were visualized by the SNOAM, indicating that the SNOAM is suitable to observe soft specimens.