The scientific and industrial communities that work with micro- and nanoparticles continue to deal with the challenge of how to effectively disperse particles in liquid. It’s commonly accepted that how quickly water repels off a surface—otherwise known as the hydrophobicity of particles—determines their ability for dispersion. Until now, there has been no easy-to-use method to quantitatively determine the hydrophobicity of these tiny particles. A new discovery may have a far-reaching impact on many scientific and industrial applications and disciplines that involve particles.

Yi Zuo, professor in the College of Engineering at the University of Hawaiʻi at Mānoa and adjunct professor of pediatrics at the John A. Burns School of Medicine, has invented a groundbreaking method that allows for easy determination of the surface free energy of particles as a quantitative measure of particle hydrophobicity. The research “An Optical Method for Quantitatively Determining the Surface Free Energy of Micro- and Nanoparticles,” was published in the October 15, 2019, issue of Analytical Chemistry and showcased on the front cover.

“The major advantage of this method resides in its simplicity,” said Zuo. “For the first time, the scientific and industrial community will have access to an inexpensive and easy-to-use method for quantitatively determining the hydrophobicity of particles. Our method relies on a novel measuring principle and common laboratory procedures and equipment such as pipetting and visible-light spectroscopy.”

Zuo has demonstrated the feasibility of this method in determining the surface free energy of various micro- and nanoparticles, such as carbon nanotubes, graphene and polystyrene particles, among others.

“Our method can be used to quantify the hydrophobicity of nanoparticles, which is of crucial importance for the study of potential health risks and biomedical applications of nanomaterials,” Zuo said, “It may also find application in microbial science because the surface free energy of bacterial cells determines the cellular adhesion and proliferation in biofilms.”

This research was supported by a National Science Foundation award. With this grant, as well as with Hawaiʻi Community Foundation support, Zuo is studying the potential health effects of nanomaterials and their biomedical applications using novel experimental techniques developed in Zuo’s Laboratory of Biocolloids and Biointerfaces.