Abstract
Self-excitation thechnique is known as an effective excitation method for a cantilever probe of the atomic force microscope to measure the surface of a biological sample in a liquid environment. In this research, we deal with a van der Pol type cantilever probe, which is previously proposed to realize the non-contact mode, and experimentally examine the relationships between the response frequency and amplitude and the gap of the cantilever probe and the surface of sample. We examine the natural frequency of the cantilever in liquid. From the result, it is confirmed that the cantilever oscillates with a low amplitude that can detect the surface of the sample without giving damage. While it is difficult to estimate natural frequency of the cantilever under external excitation in liquid, it is easy to estimate it under van der Pol type self-excited oscillation.
