Berlin 2015 – scientific programme

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O: Fachverband Oberflächenphysik

O 31: Tribology

O 31.4: Talk

Tuesday, March 17, 2015, 14:45–15:00, MA 144

Dynamic shear force microscopy of liquids in nanometer confinement — •Marc-Dominik Kraß^1,2, Nitya Nand Gosvami³, Om Prakash Khatri⁴, Robert W. Carpick³, and Roland Bennewitz^1,2 — ¹INM-Leibniz Institute for New Materials, Nanotribology Group, Saarbrücken, Germany — ²Department of Physics, Saarland University, Saarbrücken, Germany — ³Department of Mechanical Engineering and Applied Mechanics, University of Pennsylvania, Philadelphia 19104, USA — ⁴CSIR-Indian Institute of Petroleum, Chemical Science Division, Mohkampur Dehradun 248005, India

We present a new method to measure shear forces of liquids in nanometer confinement. A torsionally oscillating atomic force microscope probe (AFM) is approached to the surface. Direct torsional actuation is achieved by a micrometer-scale magnetic bead attached to the back side of the cantilever which experiences a torque by an alternating magnetic field generated by an integrated solenoid.

Dynamic measurements are conducted in a simple liquid (hexadecane) as well as in halogen-free ionic liquids ([trioctylhexylammonium][bis(salicylato)borate]). The experimental data shows changes in the dynamic signals which correlate with jumps in normal force reflecting molecular layering of the liquid. The changes in amplitude and phase of the lateral tip oscillation indicate respective changes of shear dissipation in the confined liquids.