Enhanced imaging of DNA via active quality factor control

Adsorption processes at single molecule level are of fundamental importance for the understanding and development of biomaterials. Atomic force micros copy (AFM) has played a critical role in this field due to its high resolut ion and ability to image in a liquid environment. We present a method that improves the dynamic force sensitivity and the resolution of a conventional AFM. This is achieved via a positive feedback loop that enhances the effec tive quality factor of the cantilever in a liquid environment to values in excess of 300, compared to a nominal value of similar to1. This active qual ity factor enhancement has been used to image DNA and an increase in the he ight of the molecule observed. (C) 2001 Elsevier Science B.V. All rights re served.