Fig. 5: Static 3D mixers for time-resolved SFX.

a In X-ray microtomography a 180° X-ray projection image series is recorded while potassium iodide contrast agent is flowing through the 3D-printed micromixer at a constant flow rate. b This radiograph series is then reconstructed into a 3D X-ray tomogram with 1.14 μm edge length voxels. By sectioning the 3D tomogram volume into c vertical XZ slices and d horizontal XY slices liquid flow and mixing through the five mixing elements highlighted in the CAD drawing can be extracted. Cross sections upstream, downstream and inside every mixing element are compared for two different liquid flow rate combinations. The black color represents the highly absorbing contrast agent (KI aqueous solution) and white is low absorbing water. As both liquids progress through the mixing elements they intermix into an intermittent gray level downstream (Supplementary Movies 7 and 8). The shade of gray directly represents the relative concentration of KI. The plastic material of the channel wall also appears as white. The mixing blades can be seen as straight lines cutting through circular channel cross-section (white pointer at z = 390 µm). Reconstruction artefacts can appear as dark shadows (black pointer at z = –30). e Mixing was quantified by analyzing pixel intensity distributions for each cross-section (Supplementary Fig. 13). The mixed fraction was insensitive of distance traveled across the mixer for three different flow conditions tested when compared to a matching T-junction without helical blades (see Supplementary Fig. 13D for 10 and 30% concentration envelopes). f Converting traveled distance into residence time based on the measured flow rate revealed the same design to be able to produce mixing timepoints between ~10 and ~50 ms.