Nanoscale Visualization and Contact Angle Analysis of Water Droplets on Ferroelectric Materials

Understanding wetting phenomena at the nanoscale is essential for evaluating interfacial properties of functional materials. However, conventional contact angle measurements lack the resolution required to capture nanoscopic features, while existing nanoscale approaches remain technically complex or indirect. Here, we present a direct visualization method using noncontact atomic force microscopy (AFM) combined with temperature-controlled condensation and pixel-wise contact angle mapping. By inducing the spontaneous formation of stable water droplets on hydrophilic surfaces through controlled stage cooling, we achieve high-resolution imaging and quantitative analysis of contact angles. Applying this method to ferroelectric lithium tantalate (LiTaO₃), we reveal a polarization-dependent contact angle difference at the nanoscale, undetectable by conventional macroscopic sessile methods. We further demonstrate the broader applicability of this approach by visualizing nanoscale water droplets on individual submicron nickel-iron layered double hydroxide (NiFeLDH) catalyst particles. This methodology enhances the precision and generalizability of nanoscale wetting characterization and opens further possibilities for interfacial analysis across a wide range of functional materials.