Production of water-in-oil emulsions using a droplet generator chip
Microfluidic generation of droplets has attracted a lot of interest due to the ability of this method to produce highly monodispersed droplets with high frequency (up to hundreds of kHz). Interest in droplet-based microfluidic systems has grown substantially in the past decade as they offer the ability to handle very small volumes (µl to fl) of fluids conveniently, providing better mixing, encapsulation, sorting, sensing as well as suitability for high throughput experiments. Microfluidic-based droplets have many diverse and varied applications such as particle synthesis and chemical analysis. Highly controlled droplet production also makes single cell analysis, or drug testing possible.
Materials and methods
An external pressure source is connected to two Flow EZ pressure pumps that are connected to the microfluidic ChipShop chip via tubing. The tubing passes through Flow units to measure pressure and flow rate. Visualization of the chip channels is performed using an optical microscope. A LINK can connect the Flow EZ module to a PC for monitoring pressure and flow rate in real time
Two 15 mL reservoirs containing water and 2% dSurf are connected to the two inlets of the microfluidic chip via 1/32 in. PEEK tubing of 254 µm inner diameter. The tubing passes through flow units allowing flow rate measurement and control. The length of the tubing from the reservoir to the microfluidic chip is 80 cm. Pressure is applied using the Flow EZs on the reservoirs containing distilled water and dSurf. Water is injected in the inner channel and dSurf is injected in the surrounding channel of the microfluidic device. The pressure applied ranges from 100 to 300 mbar depending on the droplet size and frequency required. Visualization of the chip channels is performed using an optical microscope. A LINK can be connected to the Flow EZ module and a PC for monitoring pressure and flow-rate in real time.
Using this range of flow rates controlled by Flow EZs with the droplet generator from microfluidic ChipShop, it is possible to obtain droplets with a diameter ranging from 80 µm to 160 µm, and with a generation rate ranging from 50 Hz to 250 Hz.
We have demonstrated the use of Fluigent pressure pumps combined with microfluidic ChipShop’s chip for the generation of monodispersed water-in-oil droplets. The versatility of the system allows one to easily produce droplets of different diameters and at several generation rates. Droplets fabricated from this system are suitable for many applications, including those that require biocompatibility.
For additional information regarding the microfluidic chip droplet generator, visit ChipShop website : www.microfluidic-chipshop.com or contact them by mail at inquiries@microfluidic-ChipShop.com
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