Dataset associated with Passive Pico-injection Enables Controlled Crystallization in a Droplet Microfluidic Device

Segmented flow microfluidic devices offer an attractive means of studying crystallisation processes. However, while they have been widely employed for protein crystallisation, 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, where this is constructed around a novel design of “pico-injector” that facilitates direct injection into flowing droplets. Exploiting a Venturi junction to reduce the pressure within the droplet, we show 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 was demonstrated for calcium carbonate, where highly reproducible results were 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 occurred even at low supersaturations. This work not only opens the door to the use of microfluidics to study the crystallisation of low solubility compounds, but the simple design of a passive pico-injector will find wide utility in areas including multi-step reactions and investigation of reaction dynamics. And the useful dataset were deposited here.