I mainly study the migration of liquid droplets in microfluidic channels. Currently, I achieve droplet migration by using a special surfactant to change the surface tension of the droplets. This surfactant is initially alkaline, and when it becomes acidic, it loses its activity. Carbonic acid is acidic, so we can indirectly cause droplet migration by introducing carbon dioxide. For example, blowing air into an oil-water mixture will cause the oil to migrate in the opposite direction of the airflow.