Supercritical miniaturization of turbulence in microsystems.

The onset of turbulence in microsystems remains a fundamental scientific and engineering challenge due to the dominance of viscous forces at small confined scales. This study, therefore, experimentally demonstrates the concept of Turbulence-On-a-Chip by generating and characterizing turbulent-like flow regimes in microconfined environments under high-pressure transcritical conditions, without the addition of any external force or passive strategy. A custom-built microfluidic test rig is developed to operate with CO[Formula: see text] at supercritical pressures and controlled temperature differences. Flow behavior is analyzed through external flow visualization and 2D time-resolved μPIV, revealing distinct laminar and turbulent-like regimes for the conditions evaluated. Laminar-like cases exhibit organized flow patterns and parabolic velocity profiles, while turbulent-like cases display irregular speckle patterns, particle migration, and optical distortions, indicative of flow destabilization through density-gradient effects. Complementary, direct numerical simulations provide deeper insight into the multiscale flow fluctuations, supporting the experimental results. These findings establish a new framework for microconfined turbulence generation, with ground-breaking implications for microfluidic mass transport and energy transfer.