How do scientists prevent the nonpolar perfluorocarbons
in oxygent from separating from the water?

Scientists prevent the nonpolar perfluorocarbons

in Oxygent from separating from the water by adding surfactant.

Explanation:

The  collection of oxygen from lungs and transporting it  all those tissues present in the human body and taking carbon dioxide back to lungs are the main functions of the hemoglobin. But, instead of this hemoglobin, When perfluorocarbons , a nonpolar chemical is used to perform the same function for the oxygen transportation, the nonpolar chemical may not mix well with the water when this perfluorocarbons is taken through a water-based saline .

For this purpose an addition of a chemical called surfactant is done. This will enhance the chemical bonding between the non polar chemical and water. The perfluorocarbons  spreads into some droplets and gets coated with this bonding substance. Thus it gets attached to the water.