Fig. 2. Protein adsorption on micropatterned substrata. Scanning force microscopy of a micropatterned substratum coated with fibronectin (dots of 1.2 µm square at a distance of 5 µm). (A) Low magnification scan (scan rate 0.5 Hz, total z scale 15 nm) showing that fibronectin is almost exclusively adsorbed to the hydrophobic alkanethiol dots. (B) Higher magnification scan of a fibronectin-coated dot. (C) Bearing histogram of the boxed region in B reveals a mean height difference between the fibronectin-coated area and the surrounding surface of approximately 3 nm. (D) Height profile (line and arrowheads in B; 3x3 µm² scan, scan rate 1.5 Hz) showing that fibronectin is adsorbed mainly as a monolayer, but up to three layers can be measured.