A versatile interferometric technique for probing the thermophysical properties of complex fluids

Area of Science:

• * Physics and Materials Science
• * Fluid Dynamics and Nanotechnology

Background:

• * Laser-induced thermocapillary deformation is useful for pure fluid characterization.
• * Nanofluids and biofluids present challenges due to laser-induced heating, momentum, and scattering forces, potentially damaging soft tissues.
• * Existing methods struggle with complex fluid systems.

Purpose of the Study:

• * To develop a versatile, rapid, non-contact interferometric technique for complex fluid interface dynamics.
• * To precisely measure thermophysical properties of nanofluids and biofluids below the thermal damage limit.
• * To characterize complex fluids in various configurations, including confined systems.

Main Methods:

• * A pump-probe-based interferometric technique.
• * Non-contact measurement with ~1 nm precision in thick films and 150 pm in thin films.
• * Utilizes different time scales of competing forces for characterization.

Main Results:

• * Successful characterization of nanofluids and biofluids in bottom-heated, top-illuminated, and confined configurations.
• * Quantitatively isolated competing forces in top-illumination setup.
• * Measured nanofluid properties and thermo-mechanical properties of metal in confined setup.
• * Demonstrated investigation of thick-film dynamics in the thin-film regime via heatwave dissipation.

Conclusions:

• * The developed technique offers a general approach for precision measurements of complex nanofluids, biofluids, and optofluidic devices.
• * The method operates below the thermal damage limit, preserving delicate fluid structures.
• * Enables quantitative analysis of competing forces and material properties in diverse fluid systems.