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Updated: Sep 26, 2025
Sub-nanometer Resolution Imaging with Amplitude-modulation Atomic Force Microscopy in Liquid
Published on: December 20, 2016
Parameterless detection of liquid-liquid interfaces with sub-micron resolution in single-molecule localization
Dingeman L H van der Haven1, Roderick Prudent Tas2, Pim van der Hoorn3
1Department of Chemical Engineering and Chemistry, Eindhoven University of Technology, The Netherlands; Department of Materials Science & Metallurgy, University of Cambridge, United Kingdom.
Hypothesis:
Knowing the exact location of soft interfaces, such as between water and oil, is essential to the study of nanoscale wetting phenomena. Recently, iPAINT was used to visualize soft interfaces in situ with minimal invasiveness, but computing the exact location of the interface remains challenging. We propose a new method to determine the interface with high accuracy. By modelling the localizations as points generated by two homogeneous Poisson processes, the exact location of the interface can be determined using a maximum likelihood estimator (MLE).
Experiments:
An MLE was constructed to estimate the location of the interface based on the discontinuity in localization density at the interface. To test the MLE, we collected experimental data through iPAINT experiments of oil-water interfaces and generated simulated data using the Monte Carlo method.
Findings:
Simulations show that the interface given by the MLE rapidly converges to the true interface location. The error of the MLE drops below the experimental localization precision. Furthermore, we show that the MLE remains accurate even if the field-of-view is reduced or when one or more particles are on the interface within the field-of-view. This work provides a key step towards the in situ, sub-micron characterization of (nanoparticle-laden) interfaces with minimal invasiveness.
