A design strategy allowing the development of an inexpensive microdevice with a cylindrical section able to work at high pressures is established. The setup combines good optical access, high-pressure resistance, homogeneous operation conditions, fast process control and detection, and the ability to generate a stable two-phase flow. The experiments are conducted in the ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate and supercritical carbon dioxide flow under isothermal conditions. The two-phase flow system is observed with a high-speed camera. An image processing procedure is performed on the films in order to determine the global two-phase flow geometrical characterizations.