Particle Track and Trace during Membrane Filtration by Direct Observation with a High Speed Camera
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Updated: Dec 24, 2025
Mass-Sensitive Particle Tracking to Characterize Membrane-Associated Macromolecule Dynamics
Published on: February 18, 2022
Mads Koustrup Jørgensen1, Kristian Boe Eriksen1, Morten Lykkegaard Christensen1
1Center for Membrane Technology, Aalborg University, Fredrik Bajers Vej 7H, 9220 Aalborg Øst, Denmark.
Abstract:
A methodology was developed for direct observation and analysis of particle movements near a microfiltration membrane. A high speed camera (1196 frames per second) was mounted on a microscope to record a hollow fiber membrane in a filtration cell with a transparent wall. Filtrations were conducted at varying pressure and crossflow velocities using synthetic core-shell particles (diameter 1.6 μm) of no and high negative surface charge. MATLAB scripts were developed to track the particle positions and calculate velocities of particle movements across and towards the membrane surface. Data showed that the velocity of particles along the membrane increases with distance from the membrane surface which correlates well with a fluid velocity profile obtained from CFD modelling. Particle track and trace was used to calculate the particle count profiles towards the membrane and document a higher concentration of particles near the membrane surface than in the bulk. Calculation of particle velocity towards and away from the membrane showed a region within 3-80 μm from the membrane surface with particle velocities higher than expected from the velocity of water through the membrane, thus the permeation drag underpredicts the actual velocity of particles towards the membrane. Near the membrane, particle velocities shift direction and move away. This is not described in classical filtration theory, but it has been speculated that this is an effect of particle rotation or due to membrane vibration or change in flow pattern close to the membrane.
Insights
Direct observation reveals particle movement near microfiltration membranes is complex. Particle velocities near the membrane deviate from predictions, suggesting factors beyond simple permeation drag influence filtration.
Area of Science:
- Membrane science
- Fluid dynamics
- Particle imaging
Background:
- Understanding particle behavior near microfiltration membranes is crucial for optimizing filtration processes.
- Classical filtration theory often simplifies particle-membrane interactions.
Purpose of the Study:
- To develop and apply a methodology for direct observation and analysis of particle movements near a microfiltration membrane.
- To investigate particle dynamics under varying filtration conditions.
Main Methods:
- High-speed microscopy and camera (1196 fps) for recording particle movement near a hollow fiber membrane.
- MATLAB scripts for particle tracking, velocity calculation, and concentration profiling.
- Computational Fluid Dynamics (CFD) modeling for fluid velocity profiles.
Main Results:
- Particle velocity along the membrane increases with distance, correlating with CFD-predicted fluid velocity profiles.
- Higher particle concentrations were observed near the membrane surface compared to the bulk.
- A distinct region (3-80 μm) showed particle velocities towards the membrane exceeding permeation drag predictions.
Conclusions:
- Permeation drag alone underpredicts particle velocity towards the membrane.
- Observed particle behavior near the membrane, including velocity shifts away from the surface, is not explained by classical filtration theory.
- Potential explanations for anomalous particle behavior include particle rotation, membrane vibration, or altered flow patterns.
