Simultaneous measurement of normal and friction forces using a cantilever-based optical interfacial force microscope

Abstract

We measured normal and friction forces simultaneously using a recently developed cantilever-based optical interfacial force microscope technique for studies of interfacial structures and mechanical properties of nanoscale materials. We derived how the forces can be incorporated into the detection signal using the classical Euler equation for beams. A lateral modulation with the amplitude of nanometers was applied to create the friction forces between tip and sample. We demonstrated its capability by measuring normal and friction forces of interfacial water at the molecular scale over all distance ranges.

Imaging stability in force-feedback high-speed atomic force microscopy

“…2(a). The periodicity was calculated to be ~3 nm, possibly suggesting distancedependent structural transition [12,13] of the water meniscus. In contrast, the periodic feature was absent in the force-distance curve on retraction.…”

“…fundamental interfacial interactions at nanometer scales [11][12][13]. The COIFM utilizes a force-feedback technique to avoid the rapid snap-to-contact process associated with AFM measurement.…”

“…By employing a feedback scheme, the spring constant can be considered infinite due to the counter force. It has proven its ability to simultaneously measure normal and friction forces between two surfaces at the nanometer scale in ambient environments using lateral modulation [12,13]. The COIFM was later adapted for high-speed AFM (HSAFM) imaging of large-scale biological specimens through the force-feedback scheme [14].…”

Cantilever-Based Optical Interfacial Force Microscopy

“…The COIFM's unique force profiles related to ambient water structure on a surface have been demonstrated (Bonander & B.I. Kim, 2008;B.I. Kim et al, 2011).…”

Cantilever-based optical interfacial force microscope in liquid using an optical-fiber tip

“…Since its development, the COIFM's improved interfacial force resolution in air has been demonstrated by observing large oscillatory forces generated by interfacial water under lateral modulation between two hydrophilic surfaces. 11,12 The COIFM has also been applied to the investigation of the mechanical properties of soft materials, 13 and its use of force feedback has been applied to high-speed atomic force microscopy to image biofilms at a rate of one frame per second. 14 The force resolution of the COIFM in these measurements was 150 pN, two orders of magnitude better than the 10 nN in IFM.…”