Understanding fluid flow near micro- and nanostructured surfaces is important for improving the performance of (bio)reactors, particularly when mass transport toward and away from surfaces plays a key role. In this work, Timo Merbach and colleagues employ µ-particle tracking velocimetry in a microreactor to experimentally track flow-following tracer particles and resolve three-dimensional, time-dependent velocity fields.
The derived mean velocity profiles agree well with the theoretical predictions for flow over porous walls. Beyond average Eulerian velocities, the Lagrangian approach captures particle trajectories and interactions near the surface, providing detailed insights into microscale flow behaviour.
The analysis of different surface structures demonstrates that rectangular microgrooves increase the contact of tracer particles with the wall, particularly when the flow is oriented perpendicular to the grooves. The method also enables the identification of particle-trapping phenomena and localized recirculation dynamics, offering a more detailed understanding of particle transport near structured surfaces.
The study further demonstrates that nanostructuring surfaces by growing a carbon nanotube forest increases the surface area and modifies local fluid dynamics. These changes can potentially enhance contact with (bio)catalysts functionalized on the nanotubes, opening up possibilities for future applications in (bio)reactor systems.
Timo Merbach, Jan H. Nissen, Fabian Riebesehl, Lukas Rennpferdt, Christoph Wigger, Eike Steuwe, Marko Hoffmann, Hoc Khiem Trieu, Bodo Fiedler, Michael Schlüter, Alexandra v. Kameke and Felix Kexel (2026). Lagrangian µ-Particle Tracking Velocimetry Analysis of Microscale Flow over Structured Surfaces. Industrial & Engineering Chemistry Research (2026).
