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Trevor Shimokusu
Trevor Shimokusu

A new and effective technique to create particle separation that was developed by a team, including an undergraduate student from the University of Hawaiʻi at Mānoa College of Engineering, was published in the American Chemical Society’s journal Langmuir.

UH Mānoa Assistant Professor Sangwoo Shin led the team. The project’s lead author, Trevor Shimokusu, who worked on this project as an undergraduate, earned his UH Mānoa mechanical engineering degree in 2019 and is currently pursuing a doctoral degree at Rice University. Co-authors include Vanessa Maybruck from Oak Ridge National Laboratory and Jesse Ault from Brown University.

The paper, “Colloid Separation by CO2-Induced Diffusiophoresis,” describes how suspended particles and droplets can be separated using carbon dioxide (CO2) gas. When CO2 dissolves into the particle suspension, a small amount of electricity is generated that can separate the particles from the solution. This technique functions not only with solid particles, but also in separating nanoscale oil droplets, which are otherwise difficult to manipulate due to their small size. The team used solid particles as carrier vehicles to capture and then separate oil droplets.

“Demonstrating the colloid separation and carrier vehicle techniques using CO2 was exciting, and provided a great opportunity to see some of the theory taught in undergrad put into practice,” said Shimokusu. “It highlighted one of the many benefits I gained from conducting research as an undergraduate student at UH under Dr. Shin’s guidance.”

These results demonstrated a portable method for separating particles in applications including oil extraction, drug delivery and bioseparation. The same technology has previously been proven to be effective at filtering water via energy-efficient means.

Figure showing that CO2 can “push” the particles (green and red) from middle stream to the bottom stream, allowing separation.
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