Today, millimeter‐sized nonspherical any‐shape particles serve as flexible, functional scaffold material in chemical and biochemical reactors tailoring their hydrodynamic properties and active surface‐to‐volume ratio based on the particle's shape. Decreasing the particle size to smaller than 100 μm would be desired as it increases the surface‐to‐volume ratio and promotes a particle assembly based on surface interactions, allowing the creation of tailored self‐assembling 3D scaffolds. This study demonstrates a continuous high‐throughput fabrication of microscopic 3D particles with complex shape and sub‐micron resolution using continuous two‐photon vertical flow lithography. Evolving from there, in‐channel particle fabrication into a confined microfluidic chamber with a resting fluid enables the precise fabrication of a defined number of particles. 3D assemblies with various particle shapes are fabricated and analyzed regarding their permeability and morphology, representing convective accessibility of the assembly's porosity. Differently shaped particles highlight the importance of contact area regarding particle–particle interactions and the respective hydraulic resistance of an assembly. Finally, cell culture experiments show manifold cell–particle interactions promising applicability as bio‐hybrid tissue. This study pushes the research boundaries of adaptive, responsive, and permeable 3D scaffolds and granular media by demonstrating a high throughput fabrication solution and a precise hydrodynamic analysis method for micro‐particle assemblies.

During soft matter filtration, colloids accumulate in a compressible porous cake layer on top of the membrane surface. The void size between the colloids predominantly defines the cake-specific permeation resistance and the corresponding filtration efficiency. While higher fluxes are beneficial for the process efficiency, they compress the cake and increase permeation resistance. However, it is not fully understood how soft particles behave during cake formation and how their compression influences the overall cake properties. This study visualizes the formation and compression process of soft filter cakes in microfluidic model systems. During cake formation, we analyze single-particle movements inside the filter cake voids and how they interact with the whole filter cake morphology. During cake compression, we visualize reversible and irreversible compression and distinguish the two phenomena. Finally, we confirm the compression phenomena by modeling the soft particle filter cake using a CFD-DEM approach. The results underline the importance of considering the compression history when describing the filter cake morphology and its related properties. Thus, this study links single colloid movements and filter cake compression to the overall cake behavior and narrows the gap between single colloid events and the filtration process.

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The integration of electrodes into microfluidic devices is a prerequisite for several key technologies such as electrophoresis, dielectrophoresis, electrowetting, or analysis and manipulation of biological cells in organ‐on‐a‐chip applications. However, conventional sputtering or metal deposition methods result in electrodes on the top or the bottom of the microfluidic device leading to either an inhomogeneous electrical field or considerable restrictions regarding optical analysis methods. Here, a novel method for integrating electrodes into microfluidic devices based on the deposition of silver films on the sidewalls of microfluidic channels by Tollens reaction is presented. Aldehydes diffuse readily through polydimethylsiloxane walls and reduce noble metal ions such as silver, which in turn precipitate and deposit on the phase border as homogeneous thin layers. The process results in sidewall electrodes that adopt the channel's geometry and offer a highly homogeneous electrical field in the case of a rectangular channel. The electrodes were analyzed by dissipative X‐ray (EDX) and electrical impedance spectroscopy, while the electrical field was visualized by particle image velocimetry. The method can fabricate electrodes in different shapes rendering the process highly promising for a wide range of different electrochemical applications in the field of microfluidics, while simultaneously enable optical analysis methods.

During soft matter filtration, colloids accumulate in a compressible porous cake layer on top of the membrane surface. The void size between the colloids predominantly defines the cake-specific permeation resistance and the corresponding filtration efficiency. While higher fluxes are beneficial for the process efficiency, they compress the cake and increase permeation resistance. However, it is not fully understood how soft particles behave during cake formation and how their compression influences the overall cake properties. This study visualizes the formation and compression process of soft filter cakes in microfluidic model systems. During cake formation, we analyze single-particle movements inside the filter cake voids and how they interact with the whole filter cake morphology. During cake compression, we visualize reversible and irreversible compression and distinguish the two phenomena. Finally, we confirm the compression phenomena by modeling the soft particle filter cake using a CFD-DEM approach. The results underline the importance of considering the compression history when describing the filter cake morphology and its related properties. Thus, this study links single colloid movements and filter cake compression to the overall cake behavior and narrows the gap between single colloid events and the filtration process.