The friction forces in single asperity contact acting between such a surface and an AFM tip was measured in air. 
AFM
Frictional behavior of micro-patterned silicon surface.A micro-patterned silicon surface, consisting of depressions with walls having a tilt angle of 30°, was created by photolithography followed by etching. 
photolithography
Frictional behavior of micro-patterned silicon surface.A micro-patterned silicon surface, consisting of depressions with walls having a tilt angle of 30°, was created by photolithography followed by etching. 
etching