Effect of Probe Lifting Height in Jumping Mode AFM for Living Cell Imaging

Atomic force microscopy (AFM) is one of the effective methods for imaging the morphological and physical properties of living cells in a near-physiological environment. However, several problems caused by the adhesion of living cells and extension of the cell membranes seriously affect the image quality during living cell imaging, hindering the study of living cells. In this work, jumping mode AFM imaging was used to image living cells at varied probe lifting heights to meet image quality requirements, and image quality related to the probe lifting height is discussed in detail. The jumping mode was divided into three parts based on the varying heights of the lifted probe, namely near-contact mode, half-jumping mode, and full-jumping mode, and the causes of their imaging drawbacks were analyzed. At an appropriate lifting height, the probe can be completely free from the influence of cell adhesion and self-excited oscillation, thus avoiding the occurrence of “trail” phenomena and invalid points in the imaging of living cells and improving the image quality. Additionally, this work provides a new approach to calculating the lateral force through the adhesion of trace and retrace scanning at a low height, which is important for studying the extension characteristics of the cell membrane. Highlights This paper systematically studies the effects of the jumping mode on imaging, which is helpful in obtaining accurate morphological information and shortening the imaging time. The causes of “trail” and invalid points in the jump mode were analyzed. A new method to calculate the vertical and lateral adhesion forces on cell surfaces for studying the extensibility of the cell membrane was proposed.