T1601-1-2 ファンデルポール型自励発振方式FM-AFMによる液中観察(マイクロナノダイナミクスの計測と制御・マイクロナノメカトロニクス(1))

Abstract

Atomic force microscopy (AFM) is recognized as indispensable for micro-electromechanical systems (MEMS), nanotechnology, and nano-biotechnology. Although observing bio-related samples in a liquid environment using AFM is increasingly important, deformable, uneven, and easily damaged surfaces of biological specimens require establishment of non-contact AFM observation. Contact mode and dynamic mode are AFM's two measurement methods. The latter reproduces the surface shape from variation appearing in the vibrating micro-cantilever's resonance, depending on change in the atomic force acting between the probe and the sample surface during measurement. Because soft irregular bumpy surfaces of biogenic samples are easily damaged, contact-mode AFM is unsuitable for samples of biological origin. Instead, non-contact observation using dynamic-mode AFM must be established. Toward observation of nanometer-scale biological samples in a liquid, this paper reports frequency-modulation atomic force microscopy (FM-AFM). It can avoid both collisions by the probe-cantilever with the sample surface and stops of oscillation by vibrating the probe-cantilever similarly to van der Pol-type self-excited oscillation.