<p>This study demonstrates the implementation of a backlight particle image velocimetry technique for visualizing and quantifying the flow field of high-pressure liquid CO₂ in a channel. High-speed imaging and advanced cross-correlation processing within a micro-PIV 2D2C (two-directional two-component) framework were employed to extract velocity vectors from the flow field. Silver-coated hollow glass microspheres with diameters ranging from 5 to 30 microns were used as tracer particles to enable flow visualization. The experimental setup comprises a CO₂ flow manifold, a K-type thermocouple for temperature measurement, digital pressure transducers, and a backlight illumination arrangement for PIV imaging. The implementation of the backlight PIV technique provides high-resolution velocity measurements while minimizing laser-induced heating effects, making it a suitable approach for studying CO₂ flow dynamics under near-critical and supercritical thermodynamic conditions. This work serves as a crucial step in advancing the understanding of CO₂ flow characteristics and heat transfer mechanisms.</p> Graphical abstract <p></p>