Flow Focusing Technology Research Articles

Scalable Liposome Synthesis by High Aspect Ratio Microfluidic Flow Focusing.

Microfluidic flow focusing provides an efficient approach to the generation of nanoscale lipid vesicles of tunable size and low size variance. Scalable nanoliposome synthesis over a wide range of production rates can be readily achieved using a high aspect ratio flow focusing device fabricated by widely available additive manufacturing methods. Here we detail methods for the manufacture and operation of a 3D-printed microfluidic flow focusing technology enabling the synthesis of liposomes with modal diameters ranging from ca. 50-200nm at production rates up to several hundred milligrams lipid per hour.

Use of Flow Focusing Technique for Microencapsulation of Myoblasts.

Alginate cell microencapsulation implies the immobilization of cells within a polymeric membrane that allows the bidirectional diffusion of nutrients and oxygen inside the microcapsules and the release of waste and therapeutic molecules outside them. This technology has been applied to several cell types and it has been extensively described with pancreatic islets. However, other cells such as myoblasts are being currently studied and showing high interest. Moreover, different systems and approaches have been developed for cell encapsulation such as electrostatic extrusion and Flow focusing technology. When Flow focusing technology is applied for myoblast encapsulation, several factors should be considered, such as the pressure, the flow of the system, or the diameter size of the nebulizer, which will determine the final diameter size and shape of the microcapsules containing the myoblasts. Finally, viability of encapsulated myoblasts needs to be assessed before further studies are performed.

Pressure-driven microfluidic flow-focusing of air through a surfactant-doped dilute polymer liquid

In this paper, we present experimental results on the formation of air bubbles in a non-Newtonian liquid. Flow-focusing technology with pressure-driven fluid pumping is used to demonstrate and study the bubble production process. The liquid phase consists of aqueous polyacrylamide at concentrations ranging from 0.01 to 0.10 wt%. Additionally, the solution contains sodium lauryl sulfate, an anionic surfactant, at concentrations ranging from 0.01 to 0.10 wt%. We report on bubble production with pressure ratios (dispersed/continuous phases) ranging from 0.6 to 0.9; the range spans from the minimum ratio required to produce bubbles to the pressure ratio required to produce an air jet. Within this range of pressure ratios, the bubbles lengths are polydisperse, a clear deviation from previous studies involving Newtonian continuous phase fluids. Although the continuous phase contains two additives, we deduce that the polymer is mainly responsible for this change in behavior from Newtonian fluids. The addition of surfactant though provides a means of manipulating this behavior for a certain range of polymer concentrations. We characterize the efficiency of the surfactant by performing a mass transport analysis using Schmidt (Sc), Sherwood (Sh), and Reynolds (Re) numbers. Despite this observation, the average bubble lengths follow trends established for Newtonian fluids.

Precision Manufacture of Phase-Change Perfluorocarbon Droplets Using Microfluidics

Liquid perfluorocarbon droplets have been of interest in the medical acoustics community for use as acoustically activated particles for tissue occlusion, imaging and therapeutics. To date, methods to produce liquid perfluorocarbon droplets typically result in a polydisperse size distribution. Because the threshold of acoustic activation is a function of diameter, there would be benefit from a monodisperse population to preserve uniformity in acoustic activation parameters. Through use of a microfluidic device with flow-focusing technology, the production of droplets of perfluoropentane with a uniform size distribution is demonstrated. Stability studies indicate that these droplets are stable in storage for at least two weeks. Acoustic studies illustrate the thresholds of vaporization as a function of droplet diameter, and a logarithmic relationship is observed between acoustic pressure and vaporization threshold within the size ranges studied. Droplets of uniform size have very little variability in acoustic vaporization threshold. Results indicate that microfluidic technology can enable greater manufacturing control of phase-change perfluorocarbons for acoustic droplet vaporization applications.

Drop Production and Tip-Streaming Phenomenon in a Microfluidic Flow-Focusing Device via an Interfacial Chemical Reaction

Microfluidic flow-focusing technology is used to investigate the effect on drop formation due to the production of a surfactant via an interfacial chemical reaction. The reactants are an aqueous solution of sodium hydroxide (NaOH) and a mixture of oleic acid (C(17)H(33)-COOH) and mineral oil, for the dispersed and continuous phase fluids, respectively, at concentration < or = 5 mM. In the absence of a chemical reaction, the drop shapes remain constant from just after breakup into droplets down at the flow-focusing nozzle until the drops exit the channel. In the presence of the chemical reaction, there is modification of the shape depending on the concentration of reactants. The drop speeds, O(10) mm/s, lengths, O(1-100) microm, and relative displacements, O(100-1000) microm, are measured for a variety of flow conditions with observable trends that correlate with the reaction rate, which we rationalize by using the Damkohler number to characterize drop production and transport in these types of flows.

Usefulness of flow focusing technology for producing subsieve-size cell enclosing capsules: Application for agarose capsules production

Flow focusing technology is known to be advantageous for micro- and nanoparticle production. We investigated the applicability of this technology to produce subsieve-size mammalian cell-enclosing capsules of less than 100 μm in diameter. Subsieve-size capsules with a narrow size distribution were obtained via droplets breakup in a water-immiscible co-flowing liquid flow by a flow focusing process. Compared with the production process of non-flow focusing, the capsules could be prepared with less consumption of the water-immiscible fluid of liquid paraffin. No harmful effects resulting from the flow focusing process on the cells enclosed in the capsules were detected in this study. The undamaged percentage of the cells immediately after the enclosing process was 96.6 ± 1.8%, and the cells enclosed in subsieve-size agarose capsules showed mitochondrial activity for over 3 weeks. These results showed that flow focusing is an effective process for producing cell-enclosing subsieve-size capsules.

Towards High‐Throughput Production of Uniformly Encoded Microparticles

Flow-focusing technology: The straightforward, fast production of microparticles of a controlled size (a few micrometers, see Figure) using the combination of a flow-focusing device and a solvent extraction/evaporation process is shown. This strategy relies on the design of microscale systems that possess a high input energy efficiency.