3 years ago

Passive Picoinjection Enables Controlled Crystallization in a Droplet Microfluidic Device

Passive Picoinjection Enables Controlled Crystallization in a Droplet Microfluidic Device
Michael J. McPherson, Fiona C. Meldrum, Muling Zeng, Thembaninkosi Gaule, Shunbo Li
Segmented flow microfluidic devices offer an attractive means of studying crystallization processes. However, while they are widely employed for protein crystallization, there are few examples of their use for sparingly soluble compounds due to problems with rapid device fouling and irreproducibility over longer run-times. This article presents a microfluidic device which overcomes these issues, as this is constructed around a novel design of “picoinjector” that facilitates direct injection into flowing droplets. Exploiting a Venturi junction to reduce the pressure within the droplet, it is shown that passive injection of solution from a side-capillary can be achieved in the absence of an applied electric field. The operation of this device is demonstrated for calcium carbonate, where highly reproducible results are obtained over long run-times at high supersaturations. This compares with conventional devices that use a Y-junction to achieve solution loading, where in-channel precipitation of calcium carbonate occurs even at low supersaturations. This work not only opens the door to the use of microfluidics to study the crystallization of low solubility compounds, but the simple design of a passive picoinjector will find wide utility in areas including multistep reactions and investigation of reaction dynamics. A microfluidic device is presented that enables highly reliable, on-chip analysis of the precipitation of insoluble crystals in flowing droplets. At the heart of the device is a novel design of picoinjector which employs a Venturi junction to achieve injection into surfactant-stabilized droplets. Chip operation is conducted for calcium carbonate, and the many advantages over traditional device designs are demonstrated.

Publisher URL: http://onlinelibrary.wiley.com/resolve/doi

DOI: 10.1002/smll.201702154

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