Fabrication of biodegradable poly(lactic acid) particles in flow focusing glass capillary devices

Plenary 1 - Manufacture of Colloidal Systems: M9Poly(dl-lactic acid) (PLA) particles with a diameter in the range from 12 to 100 µm were fabricated in flow focusing glass capillary devices shown in Figure 1. The disperse phase was 5% (w/w) PLA in dichloromethane (DCM) containing small amount of nile red and the continuous phase was 5% (w/w) poly(vinyl alcohol) in milli-Q water. The two immiscible liquids were introduced from the two ends of the same square capillary in opposite directions and both liquids were collected and exit through the inner circular capillary. The disperse phase was hydrodynamically flow focused by the continuous phase in the tapered section of the circular capillary, which caused the disperse phase to break into drops inside the collection tube. PLA particles were formed by DCM evaporation at room temperature. In order to prevent wetting of the collection tube with the disperse phase, the hydrophilicity of the glass surface was enhanced by 2-[methoxy(polyethyleneoxy)propyl]trimethoxysilane. Experimentally, we show that the droplet size is influenced by the operating conditions and orifice size, as shown in Fig. 1. The drop formation occurs near the orifice in the dripping regime (Fig. 1a-b) and farther downstream in the jetting regime (Fig. 1c). The drops formed in the jetting regime are significantly bigger than those formed in the dripping regime and have a broader size distribution.postprintUK Colloids 2011: An International Colloid and Surface Science Symposium, London, U.K., 4-6 July 2011

Control over the shell thickness of core/shell drops in three-phase glass capillary devices

Monodisperse core/shell drops with aqueous core and poly(dimethylsiloxane) (PDMS) shell of controllable thickness have been produced using a glass microcapillary device that combines co-flow and flow-focusing geometries. The throughput of the droplet generation was high, with droplet generation frequency in the range from 1,000 to 10,000 Hz. The size of the droplets can be tuned by changing the flow rate of the continuous phase. The technique enables control over the shell thickness through adjusting the flow rate ratio of the middle to inner phase. As the flow rate of the middle and inner phase increases, the droplet breakup occurs in the dripping-to-jetting transition regime, with each double emulsion droplet containing two monodisperse internal aqueous droplets. The resultant drops can be used subsequently as templates for monodisperse polymer capsules with a single or multiple inner compartments, as well as functional vesicles such as liposomes, polymersomes and colloidosomes. © Springer-Verlag Berlin Heidelberg 2012

Emulsion Templating of Poly(lactic acid) Particles: Droplet Formation Behavior

Monodisperse poly(DL-lactic acid) (PLA) particles of diameters between 11 and 121 mu m were fabricated in flow focusing glass microcapillary devices by evaporation of dichloromethane (DCM) from emulsion droplets at room temperature. The dispersed phase was 5% (w/w) PLA in DCM containing 0.1-2 mM Nile Red and the continuous phase was 5% (w/w) poly(vinyl alcohol) in reverse osmosis water. Particle diameter was 2.7 times smaller than the diameter of the emulsion droplet template, indicating very low particle porosity. Monodisperse droplets have only been produced under dripping regime using a wide range of dispersed phase flow rates (0.002-7.2 cm(3).h(-1)), continuous phase flow rates (0.3-30 cm(3).h(-1)), and orifice diameters (50-237 mu m). In the dripping regime, the ratio of droplet diameter to orifice diameter was inversely proportional to the 0.39 power of the ratio of the continuous phase flow rate to dispersed phase flow rate. Highly uniform droplets with a coefficient of variation (CV) below 2% and a ratio of the droplet diameter to orifice diameter of 0.5-1 were obtained at flow rate ratios of 4-25. Under jetting regime, polydisperse droplets (CV GT 6%) were formed by detachment from relatively long jets (between 4 and 10 times longer than droplet diameter) and a ratio of the droplet size to orifice size of 2-5