Herringbone micromixing pack

What is a herringbone micromixer and how is it used?

A herringbone micromixer is a passive microfluidic system that mixes two fluids at the same time by promoting the chaotic advection in a microchannel that is patterned. Its groove geometry with staggered arrangement creates some helical flow patterns that fold and stretch the two fluid streams at a high rate, giving complete homogenisation at the channel outlet. Common uses are immunoassays, in the preparation of PCR solutions, organic and combinatorial chemistry, screening assays, nanoparticle synthesis, and work with hazardous substances at lower concentrations.

Why is staggered herringbone design better than simple micromixer geometries?

Traditional micromixing schemes like T-shaped or Y-shaped channels use diffusion as their main mechanism which is naturally slow at microscopic scale. This is overcome by the staggered herringbone design, which actively creates transverse chaotic flows, which highly exaggerate the interfacial contact area between the two fluids. Studies have demonstrated that herringbone mixers are able to attain the same mixing performance as simple mixer types with a channel length that is 100 times shorter – an important benefit in the case of compact integrated systems.

What is the herringbone micromixer pack?

It includes two microfluidic flow sensors (Galileo, MIC), a flow controller, two 15 mL Falcon reservoir cap, a herringbone micromixer chip (such as the Fluidic 187 of Microfluidic Chipshop), the Galileo user interface software, and other accessories, including tubing, connectors, and filters. Each component has been validated as compatible, so once the experiments are sewn, the researcher can proceed with mixing without any further sourcing or integration effort.

What types of chip materials and channels dimensions are there?

The staggered herringbone chip comes in two materials Polycarbonate (PC) and Cyclo Olefin Copolymer (COP). Standard channel geometry is as follows – channel depth: 200 µm; channel inlet width: 300 µm; mixer and outlet channel width: 600 µm. These dimensions are optimised to the flow rate ranges that the pack supports and they can be discussed with MIC specialists in the event that alternative geometries are needed by a given application.

Which flow rates are supported and what does this mean in relation to nanoparticle production?

The system operates over a wide range of 100 µL/min to 30 mL/min. The broad flow rate range gives the pack a high degree of compatibility with the synthesis of lipid nanoparticle (LNP) and flow rate is a key parameter in the synthesis of particles directly related to their size and polydispersity. The LNP production in the assortment of 60-250 nm is attainable in this pack; the range of sizes is directly pertinent to drug delivery and mRNA encapsulation procedures.

What is microfluidic mixing that is beneficial compared to the traditional bulk mixing techniques?

Microfluidic mixing has a number of practical benefits against traditional methods. It dramatically saves on reagents used per experiment, thereby decreasing cost and waste of chemicals. Tuning Fluid properties on the microscale can be precisely tuned in real time, providing fast reaction kinetics that are important in crystallisation and precipitation processes. Microreactors also ensure near-isothermal conditions because the heat transfer is more efficient, and it increases the consistency of reactions. Lastly, due to the miniaturisation of the herringbone chip it can be easily incorporated into the bigger and more complicated experiment platforms.

What is the mixing efficiency of the herringbone chip?

The two dimensionless parameters that control mixing performance include the Reynolds number, which is a ratio of inertial to viscous forces in the flow, and the Peclet number, which is the relative strength of the advection to diffusion in mass transport. Both rely on the fluid viscosity, flow rate and the channel geometry. If you are not sure of the optimal operating conditions for your specific fluids and applications, please feel free to send us an inquiry.

Is it possible to scale up or scale down the pack and connect with other microfluidic devices?

Yes. There are a number of extensions that are modular. It is possible to add additional pumping channels and flow sensors to the flow controller to increase the complexity of the multi-fluid experiments. An injection device can be added in sequence to form a recirculation loop, with multiple mixing cycles to enhance homogeneity. It can also be fitted with a bubble remover to remove the air bubbles that otherwise can interfere with the performance of mixing or can destroy other sensitive processes down the line. Other mixing methods that the pack can be used with include planar serpentine micromixers.

Is the setup sterilisable for use in biological or pharmaceutical applications?

Yes. MIC has developed a sterilisation and cleaning protocol, which is given together with the user guide. This renders the pack suitable for use under aseptic conditions, e.g., biological assays, cell-based experiments, or the production of injectable nanoparticle formulations, where contamination control is imperative.

How do I personalize or customize the pack?

The pack is still under beta-testing and you will need to undergo a preliminary consultation with our specialists to ensure that you are eligible and what kind of configuration to use, depending on the application. Customization variables are the choice of chip material, the extra flow channels, bubble removing accessories and the combination with the supplementary instruments. Beta programme also allows individual instruments to be accessed individually.