Highly stable liquid-phase scanning tunneling microscope with dual modes for imaging biomolecules.

The structure of individual biological molecules can be investigated using scanning tunneling microscopy (STM). The stability and imaging precision of the STM are critically important for visualizing biological molecules, particularly in challenging solution conditions. In this paper, we present a newly constructed liquid-phase STM that features dual imaging modes and high stability, capable of simultaneously achieving high-precision atomic-level imaging via a small piezoelectric tube and large-area morphological imaging via a larger piezoelectric tube. High-quality atomic images of graphite obtained with smaller piezoelectric tube, along with the low drift rates measured under solution conditions, clearly demonstrate the STM's excellent stability and high precision. Furthermore, high-resolution morphologies of plasmid and DNA, as well as the dynamic folding process of nucleosomes, were resolved using the larger piezoelectric tube, highlighting the instrument's capability for investigating active biological molecules. Our results significantly advance the high-resolution STM study of biological samples under liquid conditions.