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Fluid Flow Measurements in Nanoslits Using Holographic Microscopy
Siyang Yu1, Jeremy Orosco1, James Friend1
1Medically Advanced Devices Laboratory, Department of Mechanical and Aerospace Engineering, University of California, San Diego, La Jolla, California 92093-0411, United States.
Langmuir : the ACS Journal of Surfaces and Colloids
|February 26, 2025
Summary
Researchers developed a new microscopy method to measure fluid flow in nanofluidics. This technique reveals evaporation-driven flow is 15x slower in nanoslits and quantifies surface acoustic wave-driven flow.
Area of Science:
- Nanofluidics
- Microscopy
- Fluid dynamics
Background:
- Observing and measuring fluid motion at the nanoscale is crucial for developing on-chip biomedical and chemical applications.
- Existing methods face challenges in accurately capturing flow dynamics in confined nanofluidic environments.
Purpose of the Study:
- To introduce a novel high-speed digital holographic microscopy technique for measuring both slow and fast fluid flows in nanofluidics.
- To characterize evaporation-driven and surface acoustic wave-driven flows within nanoslit channels.
Main Methods:
- High-speed digital holographic microscopy was employed to visualize and quantify fluid motion.
- Measurements were conducted in nanoslit channels of 25 nm and 7 nm heights.
- A noise reduction process, including spatial averaging, was developed and applied.
Main Results:
- Evaporation-driven flow in 7 nm and 25 nm nanoslits was found to be approximately 15 times slower than in open atmospheric conditions due to geometric confinement.
- Surface acoustic wave-driven flow was measured at 0.12 m/s in a 25 nm channel, resulting from 39.7 MHz acoustic wave-fluid interaction.
- Spatial averaging proved effective in discerning fluid flow and dewetting phenomena within the nanoslit channels over time.
Conclusions:
- The developed high-speed digital holographic microscopy method enables precise measurement of fluid dynamics in nanofluidics.
- Nanoslit confinement significantly impacts evaporation-driven flow rates.
- Acoustic wave-fluid interactions can drive measurable flow within nanofluidic devices.
