“…In imaging biological materials, TMAFM offers an important advantage over conventional contact-mode AFM: biological molecules and live cells can be imaged directly without the use of any complicated chemical methods to immobilize biological samples onto the substrate and, thus, the structure and function of biomolecules and cells can be studied at the same high level of resolution. Despite the recent success of TMAFM in imaging biological molecules and cells (Henderson, 1994; Hoh, 1994; Lal and John, 1994;Putman et al, 1994;Radmacher et al, 1995;Walivaara et al, 1995;Munoz-Botella et al, 1996;Schabert and Rabe, 1996; You and Lowe, 1996a), there are some basic aspects of TMAFM imaging of biological samples that are still not well understood, for instance, the factors determining the loading force applied to the sample, the deformation of biological samples, and most importantly, the image contrast mechanism(s). Because of the unexpected complexity of TMAFM, there have been few theoretical and experimental studies of the image contrast mechanism(s) (Putman et al, 1994;Hoper et al, 1995;Radmacher et al, 1995;Spatz et al, 1995;Chen et al, 1996;Ho and West, 1996;Howard et al, 1996;Munoz-Botella et al, 1996;Schabert and Rabe, 1996;Tamayo and Garcia, 1996).…”