Numéro |
J. Phys. IV France
Volume 124, Mai 2005
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Page(s) | 129 - 134 | |
DOI | https://doi.org/10.1051/jp4:2005124020 |
J. Phys. IV France 124 (2005) 129-134
DOI: 10.1051/jp4:2005124020
Use of chemically modified AFM tips as a powerful tool for the determination of surface energy of functionalised surfaces
H. Awada, G. Castelein and M. BroglyInstitut de Chimie des Surfaces et Interfaces (ICSI) - UPR 9069, 15 rue Jean Starcky, 68057 Mulhouse Cedex, France,
Abstract
Atomic Force Microscopy (AFM) has been used to determine the
surface energy of chemically modified surfaces at a local scale. To achieve
this goal, it was necessary to graft the AFM tip with the same chemical
functional groups as our analysed surface. Two different chemical
functionalities were used: hydrophilic and hydrophobic. The grafting of tip
is well developed in the literature [1-5], it consists in depositing a layer
of titanium from 3 to 4 nm followed by a 30 nm layer of Au. The thickness of
this layer deposited on the tip is of the same order of magnitude than the
radius of the AFM tip. On the other hand, the deposition of Ti increases the
gold surface roughness. To avoid the use of Ti and to decrease the thickness
of the gold layer, we developed a new way of grafting by using organic
molecules such as the (3 mercaptopropyl)-triethoxysilane (MPS) as coupling
agent [6]. Then we checked this way of grafting and finally we carried out
Deflection-Distance curves (DD) with grafted tips in static mode by using
AFM. Calibration of the various parts of the apparatus [7] and especially of
the cantilever (spring constant and radius) was primordial to reach
quantitative data. Finally, by applying a suitable theory of contact [8,9],
we were able to determine the surface energy of our system.
© EDP Sciences 2005