AVS 52nd International Symposium
    Applied Surface Science Monday Sessions
       Session AS-MoP

Paper AS-MoP11
Accurate Force Measurements in the AFM: Improvements in the MEMS Electrical Nanobalance Calibration Device

Monday, October 31, 2005, 5:00 pm, Room Exhibit Hall C&D

Session: Aspects of Applied Surface Science Poster Session
Presenter: J. Portoles, National Physical Laboratory and University of Nottingham, UK
Authors: J. Portoles, National Physical Laboratory and University of Nottingham, UK
P.J. Cumpson, National Physical Laboratory, UK
S. Allen, University of Nottingham, UK
S. Tendler, University of Nottingham, UK
P. Williams, University of Nottingham, UK
Correspondent: Click to Email
Since its invention in 1986 the AFM technique has been a powerful imaging tool, and increasingly an instrument to measure forces of the order of pN to nN. These measurements are important in biological research in the context of the study of specific interactions that affect stability and biological function of macromolecules. The accuracy of those measurements relies largely on the determination of the AFM-cantilever spring constant. Several calibration methods have been developed based on different approaches ranging from dimensional measurements of cantilevers, or static loading to dynamic measurements and Finite Elements simulations. All these methods suffer from poor precision arising from different sources (limited manufacturing control in thickness and elastic properties, difficulties in dynamic modelling, etc) Here a different approach is tested, which doesn't rely on the study of the cantilever systems. All the difficulties concerning elastic constant calibration are "transferred" to a reference system, the Electrical Nanobalance device.@footnote 1@ This is designed as a MEMS device in order to provide accurate calibration of its spring constant by a combination of interferometrical measurements and electrical excitation in vacuum. Once calibrated the spring constant of cantilevers of different materials and geometries can be determined by comparison with the nanobalance device through a simple force-distance measurement performed in air. In this poster we present tests of Electrical Nanobalance MEMS devices, in particular examining the so-called corner-loading problem. @FootnoteText@ @footnote 1@ P J Cumpson and J Hedley, Nanotechnology 14 (2003) 1279-1288.