Water Bridge Forces in Ambient Environments Studied by Interfacial Force Microscopy
Faculty Mentor Information
Byung Il Kim
Abstract
Recent advancements in scanning probe microscopy (SPM) allow us to study water bridges formed between two hydrophilic surfaces with extreme high accuracy. Many SPM studies have reported strong attractive forces at the distance of tens nanometers. These forces are due to the formation of water bridges between a probe and a flat substrate in ambient environments. However, the classical condensation theory only predicts the bridge’s formation distance to be around a few nanometers at most. In this study, as a way to fill the gap between the experimental long range force and the classical theory, we measured the force-distance curves with a micrometer size spherical probe on an oxidized silicon surfaces in the ambient humidity, ranging from 3% to 78%, to understand how formation distance changes with the humidity. The experimental data was analyzed using a theoretical force-distance model (J. Chem. Phys. 121, 4414 (2004)) to extract the humidity dependent information regarding 1) the onset distance where the capillary condensation occurs and 2) the free energy difference between vapor phase to liquid water. This study will provide an insight about how a water bridge forms under the presence of two hydrophilic surfaces.
Water Bridge Forces in Ambient Environments Studied by Interfacial Force Microscopy
Recent advancements in scanning probe microscopy (SPM) allow us to study water bridges formed between two hydrophilic surfaces with extreme high accuracy. Many SPM studies have reported strong attractive forces at the distance of tens nanometers. These forces are due to the formation of water bridges between a probe and a flat substrate in ambient environments. However, the classical condensation theory only predicts the bridge’s formation distance to be around a few nanometers at most. In this study, as a way to fill the gap between the experimental long range force and the classical theory, we measured the force-distance curves with a micrometer size spherical probe on an oxidized silicon surfaces in the ambient humidity, ranging from 3% to 78%, to understand how formation distance changes with the humidity. The experimental data was analyzed using a theoretical force-distance model (J. Chem. Phys. 121, 4414 (2004)) to extract the humidity dependent information regarding 1) the onset distance where the capillary condensation occurs and 2) the free energy difference between vapor phase to liquid water. This study will provide an insight about how a water bridge forms under the presence of two hydrophilic surfaces.