Adhesives are intended for direct contact with another surface to create varying levels of bond. These varying levels of bond, or strength, can be directly attributed to the surface area over which the two materials contact. At the nanometer level an otherwise flat appearing surface may in fact be uneven and rough altering the strength of the adhesive bond. It is for this very reason, using a profilometer, adhesive surface topography should be closely monitored during R&D and quality control to achieve intended adhesive strength.
APPLICATION NOTE: http://www.nanovea.com/Application%20Notes/adhesivetopography.pdf