Studies On Preparation Of Calcium Alginate Particles Based On A Centrifugal Microfluidic System

Calcium alginate microparticles possess good biocompatibility. It is of great significance to synthesize calcium alginate particles with precisely controllable size and morphology and apply them in bio-chemical and bio-medical fields. Microfluidic technique has shown considerable advantages in synthesizing functional particles. It provides an efficient and low-cost way to precisely control the uniformity, size and shape of the particles. In this paper, a microfluidic chip was designed used as the centrifugal platform. Sodium alginate solution was flung into calcium chloride solution in the form of droplets under centrifugal force, transforming into particles through cross-linking reaction, thus a centrifugal microfluidic system was established for the preparation of calcium alginate particles.In chapter 1, the preparation methods and development of functional particles using microfluidic techniques were reviewed, including the preparation of polymeric microparticles, metal nanoparticles and Janus particles. Then the properties and preparation methods of calcium alginate particles were introduced. Their applications in bio-chemical analysis and bio-medical science were also briefly summarized. Finally, the purpose and design of this work were proposed.In chapter 2, a novel system for the preparation of calcium alginate particles was established, combining the centrifugal microfluidic technique and the droplet-based template method. Key parameters affecting the size, shape and stability of particles were investigated, including the configuration of microfluidic chip used as the centrifugal platform, rotating speed, the size of channel outlets, the distance between channel outlets and the surface of calcium chloride solution, concentrations of alginate solution and calcium chloride solution, the existence of surfactant, etc. The monodispersity of the particles synthesized in an 8-channel microfluidic chip was investigated by calculating the coefficient of variation. The coefficient of variation of the particle size in each channel was 2.8%～4.8%(n=50). Chips with 48 and 64 micro-channels were designed. The production rates of calcium alginate particles were increased to 6 and 8 times in the 48-channel chip and the 64-channel chip, respectively. The configuration of two channels adjacent closely to each other was designed. Janus calcium alginate particles were prepared by injecting two sodium alginate solutions, which respectively contained two fluorescent beads of different colors, into two adjacent channels. Moreover, magnetic encapsulation was achieved in the Janus calcium alginate particles, preliminarily proving the application potential of the particles prepared by this method in bio-chemical analysis and other areas.In chapter 3, the novel method for preparation of alginate particles based on the centrifugal microfluidic device was summarized and predicted.