3D-AFM: A new technique for the characterization of solid/liquid interfaces
Résumé
Self-assembled or grafted onto organic monolayer on the solid surfaces of a solid-liquid interface can have the role of a sensing layer in biosensors, a protective layer in tribology processes or lab-on-chip systems. Therefore, studying the organization and the behavior of these layers in different environments is very important in order to further understand the application in which they are used. The purpose of our study is the characterization of these interfaces at the nanoscale by 3D-AFM, a newly developed technique for interfacial characterization(1,2). AFM is used for surface characterization where a 2D topographical image of the surface is generated, and also as force spectroscopy where point-by-point (1D) force vs z-distance curves are measured. 3D-AFM is a combination between these two techniques where a 3D image of the phenomena occurring above the surface, i.e. the interface, is generated. In particular, we are interested in gold-thiol layer-liquid interfaces for biosensing and tribological applications. In this work, a 3D-AFM system is implemented in a conventional 2D-AFM apparatus (Park System’s NX10). Four samples were used: pure gold, pure Poly(Acrylic Acid) PAA, pure Poly(Ethylene Glycol) PEG, and 50/50 PAA/PEO. We measured these samples in pure water and in a 0.01M PBS solution. The shifts in the frequency Δf recorded during the 3D-AFM scan were used in a Python program to create a 2D (xz) color coded cross-sectional image of the scanned samples. Our first experiments tend to show that this 3D-AFM method is appropriate to visualize the differences in behavior between the samples caused by different polymer chain-tip interactions during the measurement.
Références :
(1) T. Fukuma, R. Garcia, Atomic- and Molecular-Resolution Mapping of Solid–Liquid Interfaces by 3D Atomic Force Microscopy, ACS Nano, 2018, 12, 11785-11797.
(2) H. Asakawa, S. Yoshioka, K. Nishimura, T. Fukuma, Spatial Distribution of Lipid Headgroups and Water Molecules at Membrane/Water Interfaces Visualized by Three-Dimensional Scanning Force Microscopy, ACS Nano, 2012, 6, 9013-9020.
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