Atomic Force Microscopy in Liquid and Its Q Control for Biological Observation

Abstract

The atomic force microscope (AFM) has advantages in creating topographic images of the sample surface at high resolution even in a liquid environment, and has been expected to be used as a powerful tool for observing biological samples under the condition closer to the physiological state. However, in contrast with the advances in AFM imaging under ambient conditions, it is still difficult to obtain clear images of biological samples by AFM in liquid, because the samples are usually very soft and uneven, and easily deformed during AFM operation. In this article, based upon our experience, we showed some techniques suitable for imaging biological soft samples by AFM in a liquid environment. Special attention was paid to the dynamic mode AFM for biological studies in liquid. We also introduced a Q-control technique of dynamic mode AFM in liquid, which is helpful for increasing the image quality of soft biological sample.