3D Force and Displacement Sensor for SFA and AFM Measurements

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• 作者：Kai Kristiansen ; Patricia McGuiggan ; Greg Carver ; Carl Meinhart ; Jacob Israelachvili
• 刊名：Langmuir
• 出版年：2008
• 出版时间：February 19, 2008
• 年：2008
• 卷：24
• 期：4
• 页码：1541 - 1549
• 全文大小：379K
• 年卷期：v.24,no.4(February 19, 2008)
• ISSN：1520-5827

文摘

A new device has been designed, and a prototype built and tested, that can simultaneously measure the displacementsand/or the components of a force in three orthogonal directions. The "3D sensor" consists of four or eight strain gaugesattached to the four arms of a single cross-shaped force-measuring cantilever spring. Finite element modeling (FEM)was performed to optimize the design configuration to give desired sensitivity of force, displacement, stiffness, andresonant frequency in each direction (x, y, and z) which were tested on a "mesoscale" device and found to agree withthe predicted values to within 4-10%. The device can be fitted into a surface forces apparatus (SFA), and a futuresmaller "microscale" microfabricated version can be fitted into an atomic force microscope (AFM) for simultaneousmeasurements of the normal and lateral (friction) forces between a tip (or colloidal bead probe) and a surface, andthe topography of the surface. Results of the FEM analysis are presented, and approximate equations derived usinglinear elasticity theory are given for the sensitivity in each direction. Initial calibrations and measurements of thinfilm rheology (lubrication forces) using the "mesoscale" prototype show the device to function as expected.