Emulsion Templating of Poly(lactic acid) Particles: Droplet Formation Behavior (original) (raw)
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Hypothesis: Droplet size in microfluidic devices is affected by wettability of the microfluidic channels. Three-dimensional countercurrent flow focusing using assemblies of chemically inert glass capillaries is expected to minimize wetting of the channel walls by the organic solvent. Experiments: Monodispersed polycaprolactone and poly(lactic acid) particles with a diameter of 18-150 lm were produced by evaporation of solvent (dichloromethane or 1:2 mixture of chloroform and toluene) from oil-in-water or water-in-oil-in-water emulsions produced in three-dimensional flow focusing glass capillary devices. The drop generation behaviour was simulated numerically using the volume of fluid method. Findings: The numerical results showed good agreement with high-speed video recordings. Monodispersed droplets were produced in the dripping regime when the ratio of the continuous phase flow rate to dispersed phase flow rate was 5-20 and the Weber number of the dispersed phase was less than 0.01. The porosity of polycaprolactone particles increased from 8 to 62% when 30 wt% of the water phase was incorporated in the organic phase prior to emulsification. The inner water phase was loaded with 0.156 wt% lidocaine hydrochloride to achieve a sustained drug release. 26% of lidocaine was released after 1 h and more than 93% of the drug was released after 130 h.
2014
Hypothesis: Droplet size in microfluidic devices is affected by wettability of the microfluidic channels. Three-dimensional countercurrent flow focusing using assemblies of chemically inert glass capillaries is expected to minimize wetting of the channel walls by the organic solvent. Experiments: Monodispersed polycaprolactone and poly(lactic acid) particles with a diameter of 18-150 lm were produced by evaporation of solvent (dichloromethane or 1:2 mixture of chloroform and toluene) from oil-in-water or water-in-oil-in-water emulsions produced in three-dimensional flow focusing glass capillary devices. The drop generation behaviour was simulated numerically using the volume of fluid method. Findings: The numerical results showed good agreement with high-speed video recordings. Monodispersed droplets were produced in the dripping regime when the ratio of the continuous phase flow rate to dispersed phase flow rate was 5-20 and the Weber number of the dispersed phase was less than 0.01. The porosity of polycaprolactone particles increased from 8 to 62% when 30 wt% of the water phase was incorporated in the organic phase prior to emulsification. The inner water phase was loaded with 0.156 wt% lidocaine hydrochloride to achieve a sustained drug release. 26% of lidocaine was released after 1 h and more than 93% of the drug was released after 130 h.
Arabian Journal of Chemistry, 2012
In this paper, microspheres were prepared by oil-in-water (o/w) emulsion solvent evaporation method. Biodegradable polymer such as blend of poly (lactic acid) (PLA) and poly(e-caprolactone) (PCL) with certain compositions and characteristics was used to prepare the microspheres with poly(vinyl alcohol) (PVA) as an emulsifier. This study observed the microspheres particle's size distribution at various concentrations of PVA (1%, 1.5%, 2%, and 2.5% PVA). The PVA volume variations effects during the process (50, 100, 150, 200, and 250 mL) were also observed. The blend of PLA and PCL is formed only by physical interaction between them. This can be seen from the FTIR spectrum which shows both PLA and PCL component. The microspheres physical size and appearance were observed by optical microscope (MO). The overall results of this study showed that the formula which used 50-150 mL of 2.5% polyvinyl alcohol produced the microspheres with the most uniform size distribution.
Advanced Materials Research, 2014
Poly (vinyl alcohol) (PVAL) was a common stabilizing agent used in formulate polymeric drug encapsulated micro-/nanoparticles. In preparing poly (lactic acid) (PLA) micro-/nanoparticles by emulsion and solvent evaporation (ESE) technique, the particle size and distribution have shown dependent on PVAL concentration. The focused of this project was to investigate the PVAL function in relation to significant changes in particle size. These studies were relatively important, as it was the basic studies of material usage in ESE fabricating process. The function of PVAL as, either surfactant that able to reduce interfacial tension or stabilizer to provide steric stability was further investigated by measuring the interfacial tension (IFT) of two liquids and zeta potential of the particles. As PVAL concentration increased, the reduction of IFT was only pronounced at the early stage of PVAL incorporation from 16.02 m N/m (absence of PVAL) to 2.0 m N/m (presence of 1 % PVAL), while zeta potential of particles was gradually decreased from -25 mV to -10.2 mV. As conclusion, the presence of PVAL could reduce the interfacial tension. However, to further stabilize the particle (e.g. reduce size and narrow size distribution) in the fabrication process, the steric stabilization provided by PVAL give more significant advantages.
American Journal of Applied Sciences, 2019
Hollow poly(Lactic Acid) (PLA) microcapsules were fabricated using the bubble template method. In this method, microbubbles nucleated inside droplets of a dichloromethane solution of PLA which were located in a continuous phase of poly(vinyl alcohol). PLA-covered microbubbles formed when PLA adsorbed to the bubble surface by physisorption. Then, the coated microbubbles were spontaneously released from the droplet´s interior into the continuous phase. To increase the production yield of hollow microcapsules in this method, ultrasound was applied to enhance bubble nucleation inside the droplets. Thus to attain uniform hollow PLA microcapsules, the optimum PLA concentration with ultrasound was 30 g L −1 , which is higher than that without ultrasound (2 g L −1). At the optimum concentration, the average radius was 0.54 µm, with a polydispersity index of 21.2%. It was found that the equilibrium size of the microbubble template radius was the same with and without ultrasound. The production yield had a tenfold increase when ultrasound was employed.
Production of uniform droplets using membrane, microchannel and microfluidic emulsification devices
Microfluidics and Nanofluidics, 2012
This review provides an overview of major microengineering emulsification techniques for production of monodispersed droplets. The main emphasis has been put on membrane emulsification using Shirasu Porous Glass (SPG) and microsieve membrane, microchannel emulsification using grooved-type and straight-through microchannel plates, microfluidic junctions and flow focusing microfluidic devices. Microfabrication methods for production of planar and 3D poly(dimethylsiloxane) (PDMS) devices, glass capillary microfluidic devices and single crystal silicon microchannel array devices have been described including soft lithography, glass capillary pulling and microforging, hot embossing, anisotropic wet etching and deep reactive ion etching. In addition, fabrication methods for SPG and microseive membranes have been outlined, such as spinodal decomposition, reactive ion etching and ultraviolet LIGA (Lithography, Electroplating, and Moulding) process. The most widespread application of micromachined emulsification devices is in the synthesis of monodispersed particles and vesicles, such as polymeric particles, microgels, solid lipid particles, Janus particles, and functional vesicles (liposomes, polymersomes and collloidosomes). Glass capillary microfluidic devices are very suitable for production of core/shell drops of controllable shell thickness and multiple emulsions containing a controlled number of inner droplets and/or inner droplets of two or more distinct phases. Microchannel emulsification is a 2 very promising technique for production of monodispersed droplets with droplet throughputs of up to 100 litres per hour.
Recent Developments in Manufacturing Micro- and Nanoparticlesfrom Emulsion Droplets
Surfactant Science, 2010
Membrane and microfluidic devices are relatively new tools for highly controlled production of particles. This review focuses on the recent developments in this area, ranging from the production of simple and double emulsions of different types and morphologies (e.g. multiple core-shell structures, outer drops with controlled number of internal droplets, etc) to highly sophisticated functional products such as polymerosomes, asymmetric lipid vesicles, and core-shell particles. Other emerging technologies that extend the capabilities into different membrane materials and operation methods (such as rotating stainless steel membrane with laser drilled pores) and manufacturing approaches (extrusion of pure to-be-dispersed phase or coarsely emulsified feeds) are introduced. The use of microfluidic T-junctions, flow focusing devices and silicon microchannel array devices is also reviewed. The results of experimental work carried out by cited researchers in the field together with those of the current authors are presented in a tabular form in a rigorous and systematic manner. These demonstrate a wide range of products that can be manufactured from emulsions using different solidification techniques.
Self-assembly of latex particles at droplet interface to prepare monodisperse emulsion droplets
Colloids and Surfaces A: Physicochemical and Engineering Aspects, 2007
Monodispersed Pickering emulsion droplets were prepared by self-assembling of sulfonated polystyrene (SPS) latex particles at droplet interface. The stability of emulsion was obviously improved by pre-dispersing the latex particles in oil-water two phase and then mixing them into emulsion. For oil-in-water emulsion, the optimal stability was obtained by pre-dispersing 0.33 weight fraction of the latex particles in oil phase initially. Several parameters were considered during the preparation, including sulfonation time of the SPS latex particles, the dispersed percent of the latex particles in oil-water two phases, the pre-dispersion time of water phase dispersate and oil-water volume ratio. When sulfonation time of the latex particles was close to 60 h, the stability of the particles stabilized emulsion droplets was the best. The increase of pre-dispersion time of water phase dispersate and oil-water volume ratio could obviously decrease the dispersity of emulsion droplets. Finally, monodisperse emulsion droplets were obtained with average droplet diameter 7.4 m and standard deviation 0.37. The emulsion droplets could reassemble into ordered array.