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O: Fachverband Oberflächenphysik
O 12: Scanning Probe Techniques: Method Development I
O 12.2: Talk
Monday, March 27, 2023, 15:15–15:30, GER 37
Surface tension measurement of microdroplets using AFM — •Pranav Sudersan1, Mohammad Hormozi2, Maren Müller1, Shuai Li1, Hans-Jürgen Butt1, and Michael Kappl1 — 1Max Planck Institute for Polymer Research, Mainz, Germany — 2Technical University of Darmstadt, Darmstadt, Germany
Surface tension is a physical property which is central to our understanding of wetting phenomena. One could easily measure liquid surface tension using commercially available tensiometers. However, these tensiometers are designed for bulk liquid volumes of the order of millilitres. In order to perform similar measurements on extremely small sample volumes in the range of femtoliters, Atomic Force Microscopy (AFM) is a promising tool. It was previously reported that by fabricating a special 'nanoneedle' shaped cantilever probe, a Wilhelmy-like experiment can be performed with an AFM. In our study, we carried out measurements on microscopic droplets with the AFM, but instead using standard pyramidal cantilever tips. The AFM tips were coated with a hydrophilic polymer brush, which reduced its contact angle hysteresis. Numerical simulations of a liquid drop interacting with a pyramidal geometry were used to calculate surface tension from the experimentally measured force. Our method eliminates the need for specially fabricated 'nanoneedle' tips, thus reducing complexity and cost of measurement, making it more suitable for widespread application.