Rapid AFM imaging of large soft samples in liquid with small forces

This article addresses the reduction of the tip-sample force during rapid Atomic Force Microscope (AFM) imaging of large soft samples in liquid medium. Maintaining a small tip-sample force is critical to avoid sample damage, especially when imaging soft biological samples or polymers. The tip-sample force can be reduced if the AFM-probe can be positioned to follow the sample topography as it is scanned over the surface. However, precision positioning over the sample topography has been challenging when imaging relatively large areas in soft samples. A zoom-out/zoom-in iterative method is proposed to achieve the precision positioning needed to maintain small tip-sample forces during rapid AFM imaging. The method is used to demonstrate rapid imaging of soft hydrogel samples.