Simple Experiment to Determine Surfactant Critical Micelle Concentrations Using Contact-Angle Measurements

摘要

A simple and reliable didactic laboratory has been developed to illustrate fundamental concepts of hydrophilicity, hydrophobicity, wetting, and spreading phenomena for undergraduate students. The described laboratory includes preparation of surfactant solutions at different concentrations and applying droplets of these solutions on a hydrophobic surface followed by imaging the applied droplets using a cost-effective USB digital microscope connected to a computer. Contact-angle values of droplets were measured using ImageJ, a freely available image-processing software Students constructed surfactant-concentration contact-angle plots to determine the surfactant's critical-micelle-concentration value. The feasibility of the described didactic laboratory and the achievement of the intended learning outcomes (ILOs) were evaluated through complementary assessment tools, including lab reports, homework assignments, and students' feedback. The described laboratory was found to be cost-effective, safe, reproducible, and successful in achieving the ILOs.