Problem: The scientific community requires improved methods for performing and analyzing reactions and interactions between fluid components. Reagents are frequently scarce and there may be the need to conduct tests on only a few nanoliters of sample containing, for example, DNA or cells. Studies of reaction kinetics are limited by inaccuracies in timing, interfacial area and mixing on the macro scale. To improve understanding of the mechanisms involved, greater control is needed over the fluid volumes and the timing of the initial interaction between reactant molecules.

Applications within drug discovery can also be limited by the time taken to set up individual assays to measure the effect of a chemical on biological material. The pharmaceutical industry would therefore benefit from new methods to run increased numbers of tests in a short time, while maintaining consistent experimental conditions throughout.

The requirement to study individual cells and organic matter without undesirable environmental influence remains a key challenge in biochemistry. Experiments would ideally be performed in a nano-scale reaction chamber with dimensions close to those of the material observed. The ability to compartmentalize around very small samples is vital to obtain more accurate results. For instance, during polymerase chain reaction (PCR), artifactal DNA products are derived from the combination of template DNA molecules, an important issue which can only be resolved by reducing the chamber size to accommodate a single DNA molecule.

Solution: Droplet microfluidics creates a series of micro-reactors in a continuous flow stream. This allows high-throughput analysis of discrete reactions with highly controllable experimental conditions. Each droplet, formed when aqueous and organic fluids meet at a junction, may contain precise volumes of chemicals and biological material. These nano-sized vessels are powerful tools for research and can be used in commercial applications for the controlled release and targeting of active ingredients.

Dolomite’s Micro Droplet Systems are capable of producing droplets ranging from 5 to 250μm in diameter, at rates of up to 10,000 droplets per second. Instruments that generate the droplets vary, with technology suitable for almost any liquid sample type. The simplest systems use pulseless fluidic micro-pumps, providing constant and seamless pressure, eliminating dead space and reducing reagent waste. Syringe-based systems permit an extra level of control, boosting workflow efficiency by enabling the refilling of the liquids in the channels of the droplet chip. More advanced droplet systems allow greater control over the liquid stream, providing more sensitive control of the pump pressure and regulating the size and speed at which droplets are generated.

At the core of this technology is the Droplet Junction Chip (Figure 1), containing the droplet junction. This meeting point of the liquid flow channels is the origin of droplet formation. Almost perfectly circular flow channels and smooth surfaces allow the formation of perfectly circular droplets within the carrier fluid. Advanced hydrophobic coating treatments enable water-in-oil droplets to be generated as well as oil-in-water droplets formed in the untreated chips. Stable liquid flow within the junction chip is essential to maintain the droplets in suspension. Chips can be manufactured to form single or double droplet streams, micro droplets less than 5μm across and Janus particles with two distinct halves.

The laboratory applications of the micro droplets are vast and vary from field to field. Micro chemistry enables the reduction of the expense of repeated reaction processes, while providing the opportunity to study reactions on a micro scale, which would otherwise be dangerous. Biochemical applications include analysis of the polymerization of alginate molecules from Pseudomonas bacteria, preparation and encapsulation of individual cells for microscopy, preparation of particles for protein crystallography and the packaging of DNA molecules for sequencing or transfection.

Dolomite’s Micro Droplet Systems offer a workflow solution for the rapid, efficient and cost-effective generation of reagents and compartmentalized biochemical reagents. These allow for accurately timed kinetic studies, and a reduction in the scale and consumption of scarce and expensive reactants.

For more information, visit www.dolomite-microfluidics.com