Related Experiment Video
Updated: Feb 4, 2026

Measuring the Interaction Force Between a Droplet and a Super-hydrophobic Substrate by the Optical Lever Method
Published on: June 14, 2019
Experimental Characterization of Droplet Adhesion: The Ejection Test Method (ETM) Applied to Surfaces with Various
Gabriela Ramos Chagas1, Franck Celestini2, Christophe Raufaste2
1NICE Lab, IMREDD , Université Côte d'Azur , 61-63 Av. Simon Veil , 06200 Nice , France.
Abstract:
We study the wetting and the adhesive behavior of substrates made by electropolymerization of copolymers of pyrene substituted with fluoroalkyl and adamantyl groups. The hydrophobicity and water adhesion properties can be tuned by the molar percentage (mol %) of each pyrene monomer so that the substrate properties can vary from superhydrophobic to parahydrophobic, with respectively low and high water adhesion. The ejection test method (ETM) is proposed as an original tool to discriminate and characterize such substrates. Using a catapult-like apparatus, a droplet initially at rest on the surface is subject to a large acceleration and is subsequently ejected. Depending on the surface properties and initial catapult acceleration, the ejection is more or less efficient and occurs with or without fragmentation of the droplet. The ETM is shown to be a complementary test to the lateral adhesion and hysteresis classical measurements. This work is of importance for the understanding of adhesion phenomena on various surfaces and for a better quantitative characterization of their adhesive properties.
Related Concept Videos
Adhesion
Capillary action is a result of water’s adhesive tendencies. When a narrow...
Surface Tension, Capillary Action, and Viscosity
The various IMFs between identical molecules of a substance are examples of cohesive forces. The molecules within a liquid are surrounded by other molecules and are attracted equally in all directions by the cohesive forces within the liquid. However, the molecules on the surface of a liquid are attracted only by about one-half as many molecules. Because of the unbalanced molecular attractions on the surface molecules, liquids contract to form a shape that minimizes the number...
Cell Adhesion in Plants
Pectins are complex heteropolymers mainly composed of negatively-charged α-D-glucopyranosyl uronic acid and some neutral glycosyl residues such as α-L-rhamnopyranose, α-L-arabinofuranose,...
Surface Tension and Surface Energy
Consider a beaker filled with liquid. The bulk molecules in the liquid experience equal attractive forces on all sides with the surrounding molecules. However, the surface molecules experience a net attractive force downward due to the bulk molecules. The surface of the liquid behaves like a stretched membrane,...
Substitution Rule Applied to Indefinite Integrals
Substitution Rule Applied to Definite Integrals

