Jumping mode scanning force microscopy: a suitable technique for imaging DNA in liquids

In this work, we introduce jumping mode (JM) scanning force microscopy (SFM) as a suitable technique for imaging soft samples in liquid environment like DNA adsorbed on mica. JM reveals as a non-intrusive technique where shear forces are minimized by performing the scanning motion without tip–sample contact. We find no visible damage on DNA samples and the nominal height of 2 nm of the molecules is achieved when imaging applying a maximum normal force of ∼150 pN. In addition to topographic images, adhesion maps of DNA are simultaneously recorded showing that the minimum adhesion force occurs on top of the DNA molecules.