  Micro-domains of modified surface potential (SP) were created on
hydroxyapatite (HAp) films by direct patterning by midenergy focused electron
beam, typically available as a microprobe of Scanning Electron Microscopes. The
SP distribution of these patterns has been studied on sub-micrometer scale by
the Kelvin Probe Force Microscopy method as well as lysozyme adsorption. Since
the lysozyme is positively charged at physiological pH, it allows us to track
positively and negatively charged areas of the SP patterns. Distribution of the
adsorbed proteins over the domains was in good agreement with the observed SP
patterns.
