The FDmiX platform can be used for a wide range of mixing applications, as the system is extremely robust, delivers short mixing times and nearly provides the same mixing quality over the entire flow range. Thus, the system can be used quite generally for so-called continuous flow chemistry, i.e. for chemical reactions (e.g. precipitation processes) that are not carried out in individual batch productions but in a continuously flowing stream. In addition, the FDmiX platform is suitable for the production of nanoemulsions, i.e. the generation of a stable mixture of otherwise immiscible substances, such as water and oil. Finally, the system can also be used to encapsulate mRNA and other substances in lipid- and polymer-based nanoparticles.

At the heart of the FDmiX platform is an OsciJet nozzle, as shown schematically on the right. ❶ shows an OsciJet nozzle as we would perceive it with the naked eye.  Since the human eye is generally too slow, it seems that the visible spray pattern is apparently no different from that of a flat spray nozzle. However, this is only due to our perception capabilities. If you look at the process in time resolution, you will see that a jet inside the nozzle is positioned on one of the sides in the main chamber ❷. If you follow the jet through the main chamber, you can see that a small part of the jet is deflected into a side channel before leaving the nozzle. At the end of the side channel, this meets the main jet again and pushes it to the other side ❸. As a result, the main jet oscillates continuously from one side to the other. ❹ shows the beam pattern as it looks in time resolution. [more on how it works]

The figure on the left shows an FDmiX mixer/reactor. The mixer consists of a base plate into which an OsciJet nozzle and a mixing chamber are milled and a lid, which we have not shown here. The base and lid are bolted together via eight large holes to withstand even the highest pressures. To the left of the metal plate, the actual mixer is shown schematically.
One of the components to be mixed is introduced into the system at ① and then flows into the OsciJet nozzle. As it flows through the OsciJet nozzle, the component is caused to vibrate. The second component is introduced at ② perpendicular to the mixer and then meets the oscillating jet of the first component at ③. The high-frequency vibration now ensures that the first component interacts quasi abruptly with the second component and is then transported further into the mixing chamber. The mixture then leaves the outlet ④ further downstream of the mixing chamber.

Nanotechnology has seen significant progress in the cosmetic and pharmaceutical industries in recent years. Not least, the pandemic has impressively demonstrated the effectiveness of drug delivery systems based on nanoparticles and sparked the discussion on mRNA-based drugs, revealing considerable potential. In addition to mRNA drugs, other nanosystems (nanoparticles, liposomes, nanoemulsions, nanocrystals, etc.) also show great potential in other fields. Skin creams based on nanoemulsions are also now widely used in the cosmetic field. In many cases, the rapid mixing of fluids is essential for these nanosystems. The quality of the mixing not only determines the quality of the products, but ultimately also their effectiveness. So-called microfluidics are often used for the production of small quantities. These are characterized by small structures in which capillary forces usually dominate. This is accompanied by the fact that in these very small structures, the frictional forces largely determine the inertial forces, which leads to laminar flows, i.e. flows without significant cross-exchange. The lack of cross-exchange makes mixing more difficult. The advantage of this method is that the processes can be controlled very well. The disadvantage is that a mixing process established in this way cannot simply be transferred to a larger scale. Thus, impinging mixers, also known as T- or Y-pieces, in which the mixing mechanism is not primarily based on diffusion, are often used in series production. For substances that do not interact, this can sometimes be neglected, but as soon as chemical processes play a role, the mixing mechanism and the associated time scales are essential for the resulting properties. This highlights the challenges of upscaling in nanosystems production.

These can be circumvented if, in principle, the same mixing mechanism is used for mixing two fluids. As described above, the mixing of the FDmiX platform is based on a scalable principle. The oscillating flow of one substance through the OsciJet meets the flow of the second substance perpendicularly and thus produces a good mixture very quickly. The mixing times here are in the millisecond range and are thus faster than lightning. Since the OsciJet nozzles can be scaled up without any problems, this also makes it easy to scale up a laboratory process. In internal tests, we were thus able to demonstrate that, particularly in lipid nanocapsulation, i.e. the encapsulation of an active ingredient with a lipid shell, the resulting particles are significantly smaller and more homogeneous, and the particle size can even be adjusted. The FDmiX platform is particularly well suited for the production of nanoparticles and -emulsions, in precipitation processes and many other mixing processes.

The videos below show mixing experiments that we performed using the transmitted light method. In the impinging mixer, shown in the video on the left, that the two phases collide and then flow down vertically parallel to each other and concentration differences can be seen quite clearly. The FDmiX mixer on the right, on the other hand, shows a much more homogeneous image.