Low-cost modification of a contact atomic force microscope (AFM) into a sound-activated tapping mode AFM for use in air and liquids

Tapping mode capabilities are successfully implemented on a commercial contact mode atomic force microscope. In our setup, standard Si3N4 cantilevers are vibrated by an acoustic wave from a small piezo speaker. The minor changes needed in the measurement electronics are presented. Experiments performed both in air and under liquid, on hard as well as on soft samples, clearly demonstrate improvements in image quality, contrast, and resolution. Especially on soft biological samples, such as microtubules, the common problems of smearing and irreversible sample damage by scanning seem to be alleviated.