Sensing specific molecular interactions with the atomic force microscope

One of the unique features of the atomic force microscope (AFM) is its capacity to measure interactions between tip and sample with high sensitivity and unparalleled spatial resolution. Since the development of methods for the functionalization of the tips, the versatility of the AFM has been expanded to experiments where specific molecular interactions are measured. For illustration, we present measurements of the interaction between complementary strands of DNA. A necessary prerequisite for the quantitative analysis of the interaction force is knowledge of the spring constant of the cantilevers. Here, we compare different techniques that allow for the in situ measurement of the absolute value of the spring constant of cantilevers.