Dynamic Surfaces and Directional Nanoscale Motion Tao Ye, School of Natural Sciences, University of California Merced Au Au (111) AFM frictional mode image of a patterned chemical gradient. The background SAM has low friction (dark), and regions with more charged molecules have higher friction (brighter). The gradient was patterned using AFM nanografting,. Schematic of nanomotors on a dynamic chemical gradient. Left: a negatively charged gold nanoplate is anticipated to move along a gradient of positive charged groups on an alkanethiol self-assembled monolayer (SAM) on gold. Right: The functional groups, such as tetrathiafulavene, can be switched between charged and neutral states using electrochemical control. The cyclic voltammetry of TTF attached to gold shows that the redox chemistry is highly reversible even under an aqueous condition, 0.05M LiClO4. Method of patterning single DNA molecules onto a chemically tailored surface. a) – c) Atomic force microscope tip is used to desorb the SAM. The molecules in solution replace the desorbed molecules to form a highly-ordered structure. d) Representative AFM image of resulting structures. Josephs and Ye, Journal of the American Chemical society (132, 3697–3701).