title: Nano-Wilhelmy investigation of dynamic wetting properties of AFM tips through tip-nanobubble interaction.
abstract: The dynamic wetting properties of atomic force microscopy (AFM) tips are of much concern in many AFM-related measurement, fabrication, and manipulation applications. In this study, the wetting properties of silicon and silicon nitride AFM tips are investigated through dynamic contact angle measurement using a nano-Wilhelmy balance based method. This is done by capillary force measurement during extension and retraction motion of AFM tips relative to interfacial nanobubbles. The working principle of the proposed method and mathematic models for dynamic contact angle measurement are presented. Geometric models of AFM tips were constructed using scanning electronic microscopy (SEM) images taken from different view directions. The detailed process of tip-nanobubble interaction was investigated using force-distance curves of AFM on nanobubbles. Several parameters including nanobubble height, adhesion and capillary force between tip and nanobubbles are extracted. The variation of these parameters was studied over nanobubble surfaces. The dynamic contact angles of the AFM tips were calculated from the capillary force measurements. The proposed method provides direct measurement of dynamic contact angles for AFM tips and can also be taken as a general approach for nanoscale dynamic wetting property investigation.
authors.affiliation: Robotics Institute, School of Mechanical Engineering and Automation, Beihang University, Beijing 100191, P.R. China.
authors.forename: Yuliang
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Department of Materials Science and Engineering, The Ohio State University, 2041 College Rd., Columbus, OH 43210, USA.
authors.forename: Huimin
authors.initials: H
authors.lastname: Wang
authors.affiliation: Robotics Institute, School of Mechanical Engineering and Automation, Beihang University, Beijing 100191, P.R. China.
authors.forename: Shusheng
authors.initials: S
authors.lastname: Bi
authors.affiliation: School of Material Science and Engineering, Harbin Institute of Technology, Harbin, 150001, P.R. China.
authors.forename: Bin
authors.initials: B
authors.lastname: Guo