Fast and Environmentally Friendly Microfluidic Technique for the Fabrication of Polymer Microspheres

Abstract

This paper reports on a novel microfluidic technique for the fabrication of microspheres of synthetic polymers including poly(vinyl chloride) (PVC), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), poly(lactic acid) (PLA), and polystyrene (PS). The polymers are dissolved in tetrahydrofuran (THF) and the method is based on the diminished solubility of THF in a 20% (w/v) NaCl solution which allows the formation of droplets of the polymer solution. These polymer solution droplets are generated in a microfluidic system and their desolvation is accomplished within seconds by allowing the droplets to rise by buoyancy through a NaCl solution with a concentration lower than 15%. The size and morphology of the resultant polymer microspheres have been investigated by optical and scanning electron microscopy. Apart from the elimination of the use of highly toxic solvents as in conventional methods for manufacturing of polymer microspheres, the newly developed technique has the advantages of providing faster desolvation of the polymer solution droplets and a higher yield of microspheres compared to emulsification-based techniques.

Microfluidic Fabrication of Micropolymer Inclusion Beads for the Recovery of Gold from Electronic Scrap

“…It was established in an earlier study that a higher NaCl concentration for the desolvation of the polymer solution droplets resulted in polymer microbeads with a smooth surface. 32 Therefore, it was of interest to examine the effect of the NaCl concentration in the desolvation solution on the extraction performance of the resulting μPIBs of theoretical composition of 50% PVC, 40% A336, and 10% TD. The results shown in Figure 5 indicate only a slight decrease in the amount of Au(III) extracted when the NaCl concentration was increased from 5% (m/v) to 15% (m/v).…”

“…The fabrication of the μPIBs was carried out using a surfactant-free microfluidic technique characterized by very fast desolvation compared to conventional surfactant-based emulsion techniques . This technique was implemented in the device, as shown in Figure , which was similar to the one used by us in an earlier study for the fabrication of polymer microspheres .…”

“…The fabrication of the μPIBs was carried out using a surfactant-free microfluidic technique characterized by very fast desolvation compared to conventional surfactant-based emulsion techniques. 32 This technique was implemented in the device, as shown in Figure 1, which was similar to the one used by us in an earlier study for the fabrication of polymer microspheres. 32 In brief, the fabrication procedure included dispensing of a 3% (m/v) μPIB solution and a 20% (m/v) NaCl solution by two syringe pumps (NE-1000, New Era Pump Systems Inc., USA) toward a T-junction in which the μPIB solution was segmented by the stream of NaCl solution to form microdroplets.…”

“…32 This technique was implemented in the device, as shown in Figure 1, which was similar to the one used by us in an earlier study for the fabrication of polymer microspheres. 32 In brief, the fabrication procedure included dispensing of a 3% (m/v) μPIB solution and a 20% (m/v) NaCl solution by two syringe pumps (NE-1000, New Era Pump Systems Inc., USA) toward a T-junction in which the μPIB solution was segmented by the stream of NaCl solution to form microdroplets. The syringe pump (P1) for the delivery of the μPIB solution was equipped with a 5 mL airtight glass syringe, while the pump (P2) for the 20% (m/v) NaCl solution was fitted with a plastic syringe with a volume capacity of 25 mL.…”

“…31 In a recent paper, we reported on the development of a novel microfluidic technique for the fabrication of polymer microspheres (microbeads). 32 Considering the fact that microspheres offer significantly higher specific surface area than membranes of the same mass, thus increasing the rate of associated interfacial mass-transfer processes (e.g., extraction and stripping) and the convenience of using columns for industrial and analytical separation applications, it was of interest to examine if this technique could be adapted to the fabrication of micropolymer inclusion beads (μPIBs) with compositions similar to those of traditional PIMs. Thus, the present paper describes the microfluidic fabrication of such microbeads, composed of PVC as the base polymer, Aliquat 336 as the extractant, and 1-tetradecanol (TD) as a modifier, and their application for the recovery of Au(III) from a simulated aqua regia digest of electronic scrap.…”