Instantaneous 4D micro-particle image velocimetry (µPIV) via multifocal microscopy (MUM)

Area of Science:

• Biophysics
• Fluid Dynamics
• Microscopy

Background:

• Micro-particle image velocimetry (µPIV) is vital for analyzing fluid flow at the microscale.
• Existing methods face limitations in speed and volumetric capture for dynamic biological systems.

Purpose of the Study:

• To adapt multifocal microscopy (MUM) for µPIV applications.
• To reconstruct velocity and shear stress fields around cells with high accuracy and speed.

Main Methods:

• Utilized a diffraction-based multifocal relay to capture images from three axial planes simultaneously.
• Employed an image sharpness metric to determine particle axial positions.
• Applied MUM-µPIV to fixed and live cells under perfusion.

Main Results:

• Achieved velocity accuracy of approximately 0.52 ± 0.19 µm/s.
• Imaged sub-cellular flow perturbations consistent with literature.
• Observed the impact of cell morphology changes on local flow in real-time.
• Demonstrated MUM-µPIV is over 300 times faster than standard confocal microscopy.

Conclusions:

• MUM is a highly effective and rapid technique for µPIV.
• Enables real-time monitoring of cellular responses to external forces in dynamic biological systems.
• Offers significant advantages for studying rapidly evolving biological phenomena.