Determination of Surface Energy by Means of Home-Made Goniometer and Image Analyzing Software for Contact Angle Measurement

Abstract

ABSTRACT. We report a contact angle goniometer that can be easily assembled and used in high school and general chem-istry experiments. It consists of an LED flash, a sample stand, and a camera fixed on an optical bread board, and the sample area is covered to block light from outside with a box with holes on both sides. ImageJ, free image analyzing software and a JAVA plugin (Drop_analysis) were used to determine the contact angle of liquid drop resting on solid surface. The contact angles of various liquids were successfully measured on various surfaces. The solid surface energies have also been deter-mined using the Owen-Wendt method from the contact angles of H2O and CH2I2. The results reasonably agree with the pre-viously reported values, showing the surface characteristics and modification as well as the dispersive and polar contributions. These contact angle goniometer and method for determination of the contact angle and surface energy can be applied to obser-vation of various surface properties including wettability, hydrophilicity, and water repelling. Students can learn how the sur-face properties are related to the intermolecular interactions and gain experience about the equilibrium between the relate