Recent progress in frequency modulation atomic force microscopy in liquids

Abstract

Recent progress in frequency modulation atomic force microscopy (FM-AFM) working in liquids has allowed us to directly investigate a wide variety of physical, chemical and biological processes at molecular scale, including various “in vivo” biological interactions. In particular, two/three-dimensional (2D/3D) force mapping based on quantitative FM-AFM force measurements has been applied to various solid-liquid interface studies on a molecular scale. In this chapter, after a brief overview of FM-AFM working in liquids, crucial conditions required for quantitative force measurement are described. In addition we show the applications of 2D/3D force mapping to the visualization of molecular-scale hydration structures as well as that of local electric double layer forces. Finally high-resolution FM-AFM images of biological molecules such as double-helix structure of DNA and immunoglobulin G (IgG) antibody molecules obtained in quasi-physiological environments are presented.