Effects of sample surface free energy (s) and relative humidity (RH) of the tip-sample environment on image contrast and friction characteristics measured with lateral force microscopy (LFM) have been investigated. Samples having a wide range of surface free energies were fabricated by combining microcontact printing, silane vapor deposition, and UV/O3 treatment. Humidity in the tip-sample environment was controlled using a chamber enclosing the AFM head. The friction difference between two chemically-different domains increases slightly at low RH, reaches a maximum at elevated RH, and then decreases. This friction behavior is proportional to the s difference of the two domains. The LFM image contrast between domains follows closely with their s difference. By optimizing RH, LFM is found to be capable of discerning two domains having a difference in their surface free energy as small as 6.4 mJ/m2. The enhanced image contrast at elevated RHs is attributed to the capillary force, which is a function of surface free energy of the sample.
Proceedings Title: Adhesion Society Meeting
Conference Dates: February 21-24, 2010
Conference Location: Daytona Beach , FL
Pub Type: Conferences
AFM, friction, chemical, humidity, imaging, surface free energy