Pulsed-DC Electrospray for Biopolymer Particle Production
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Pulsed-DC Electrospray for Biopolymer Particle Production Cho-Hui Lim1, Kiersten R. Schierbeek2, and Michael E. Mullins1 Department of Chemical Engineering, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, U.S.A. 2 Department of Biological Sciences, Michigan Technological University, 1400 Townsend Drive, Houghton, MI 49931, U.S.A.
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ABSTRACT PLLA microparticles were successfully fabricated via pulsed-DC electrospray. In this study, we investigated the effect of the pulsed voltage characteristics (e.g. pulse frequency, pulse amplitude and pulse width) on the particle’s size. We found that pulse frequency, pulse amplitude, pulse width, and the combinations of these factors had a statistically significant effect on the particle’s size. The process conditions to obtain smaller particles with uniform shape and size are a low pulse frequency, high pulse amplitude, and long pulse width (or a high duty cycle).
INTRODUCTION The microparticle is of considerable interest for a wide variety of applications in drug encapsulation, coating, DeskJet printers, and painting. It has been prepared in numerous ways based on the nature of the material used. Examples for producing a polymeric particle include emulsion evaporation, emulsion diffusion, nanoprecipitation, salting-out, and electrospray [1-4]. The method adopted will decide the final structure of the particles. A polymeric particle can be classified into two common types: core-shell and sphere [5]. The distinct advantages of using the electrospray technique over other methods are its ability to create both particles in a single step, and prevent the use of a toxic emulsifier. However, the most challenging problem of using this technique is the control the particle’s size and uniformity. The particle’s size significantly influences its usage and is mainly dependent on the voltage applied, the flow rate, and the physical properties of the material and solvent used. To date, most electrospray experiments have been conducted using only direct-current (DC) voltage, while a few were conducted by alternating-current (AC) voltage [6, 7]. In contrast, pulsed electrospray offers a greater control over the voltage variables. We are developing a simple and cost-effective device that allows us to produce monodispersed particles and capsules with controllable size and adjustable sheath thickness on demand. To achieve this goal, we have combined the techniques of dual-capillary electrospray and pulsed electrospray. Here, we will focus on the effect of the pulsed voltage characteristics (e.g. pulse frequency, pulse amplitude, and pulse width) on the electrospray particle morphology and size distribution. Some important parameters such as polymer concentration, organic solvent, feed flow rate, distance between the spray head and the collector, spray head, and the collector were selected based on our previous study on DC electrospray and pulsed electrospray. The results for the techniques utilizing a biodegradable polymer, poly (Llactide) PLLA, which
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