Berlin 2018 – scientific programme

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CPP: Fachverband Chemische Physik und Polymerphysik

CPP 25: Interfaces and Thin Films II

CPP 25.5: Talk

Tuesday, March 13, 2018, 10:45–11:00, PC 203

3D Depth Profiles of the Tip-Sample Interaction on Polystyrene Swollen in Chloroform Vapor using Atomic Force Microscopy — •Martin Dehnert and Robert Magerle — Fakultät für Naturwissenschaften, Technische Universität Chemnitz, Germany

In atomic force microscopy (AFM) on soft polymers and liquids, the tip-sample interaction is dominated by long range van der Waals and capillary forces and the tip can indent several tens of nanometers into the surface. Therefore, measuring the unperturbed shape of the soft surface can be challenging. Here, we examine polystyrene droplets swollen in chloroform vapor, where we can adjust the specimens' mechanical properties via the solvent vapor concentration from a stiff solid to a fluid film. With the same AFM tip, we measure three-dimensional (3D) depth profiles of the tip-sample interaction with two different AFM force spectroscopy methods: force-distance (FD) curves and amplitude-phase-distance (APD) curves. The 3D depth profiles reconstructed from FD and APD measurements provide a detailed insight into the tip-sample interaction mechanism with a fluid PS droplet. Furthermore, we discuss how the unperturbed shape of a fluid droplet can be determined from FD and APD depth profiles. We expect that this versatile methodology can also be used for investigating other fluid and gel-like objects on the nanometer scale.