Thousands of centimeters or even millimeter devices have been developed for use in high-cost drug manufacturing, emulsion manufacturing, cytometry, drug identification, drug dosing, cell analysis, cancer analysis, and a variety of specialized diagnostic applications.

Microfluidic devices are characterized by the processing of very small amounts of liquid, either as continuous flow in a stream, storage in microwells or as droplets on a chip; average number of femto- to picoliters (10-15-10-12 L)! Because manufacturing processes for many microfluidic systems were originally developed in the semiconductor industry, they are also suitable for the direct integration of micromachined sensors and actuators: Labs-on-a-Chip!

A clear advantage of the microfluidic approach in diagnostics and pharmaceutical production is the reduced consumption of expensive reagents and catalysts (ie platinum, palladium, rhodium). Similarly, reducing the production of waste products is desirable because disposal can be insignificant and requires complex and energy-intensive processes for non-toxic disposal or special storage.

If microfluidics are reasonably available, costs can be reduced not only for inputs and wastewater, but also for other peripheral process factors, such as capital costs due to reactor modularity, energy efficiency or better process control.

Microfluidic platforms significantly increase the liquid-surface-to-volume ratio and provide a number of process control benefits. One is fast mixing; where two reagent streams are in contact, for example in a T-node, complete and homogeneous mixing occurs faster than in macro-scale mixtures. In many applications, this is critical because imperfectly mixed reagents can prevent unwanted side reactions.

In addition, it allows for fast mixing and a small channel size, allowing for a high level of thermal control. Extremely exothermic or even explosive reactions can be carried out safely because very little absolute heat is generated and is easily absorbed. Constant fluid temperatures will lead to more stable yields in both production and diagnostics.

While microfluidic platforms offer a number of benefits for safety, cost and process control, there are challenges that remain a topic of ongoing research and technological development.

One of these areas is quantifying the impact of production permits. Because the grooves are so small, deviations from the designed cross-sectional profile can have an exceptional effect on factors such as pressure reduction or mixing behavior. Another area that often presents problems is multiphase currents.

In microdroplet generators, two unmixed fluids meet at a node, resulting in multiple droplet size distributions; it is often used in emulsions for encapsulation and drug dosing. Similarly, microbubbles can be used for gas-liquid reactions that require extremely rapid mixing. The solids contained in the stream also allow better process control, for example on the surface of the catalyst production particles as a regulator of diagnostic cells.

The physics of these multiphase microfluidic processes can be extremely complex! Creating the desired droplet or bubble size requires many adjustments to the shape and size of the channel, as well as pressure and flow. Biological cells or catalyst particles can agglomerate or stick to the walls, creating blockages, so it is important to understand the channel and surface properties of the particles and whether flow patterns can reduce adhesion and blockage.

Due to the complexity of these processes, manufacturing and testing physical equipment can be costly and time consuming. Computational modeling, while not a substitute for physical testing, can significantly reduce development time and costs.

Correlation of modeling results with existing experimental data can provide confidence in the criteria of the base model and then help facilitate new design changes.