Study on the Developed Microfluidic Chip for Micro-emulsion Generation

• Main Authors: Chia-HsienYeh, 葉家顯
• Other Authors: Yu-Cheng Lin
• Format: Others
• Language: en_US
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/26100662891249472733

博士 === 國立成功大學 === 工程科學系碩博士班 === 100 === Conventional drug release models include the dump system, oral intake, and injection, etc. These models cause drugs to be quickly absorbed by the human body and cause the drug concentration to be higher in the blood. Patients might not get the optimal efficacy and get side effects. So, the drug control release technique is very important. The objective of the drug controlled release research was to increase the drug efficacy, decrease the medication frequency, and reduce side effects. Because the microcapsule size and distribution have an influence on the clearance rate from the body and ultimately determine the drug dosage, it is important to control the size of the uniform biomaterial microspheres and narrow the size distribution. So, in this study, the developed microfluidic chips were used to generate the uniform emulsions. The gradient-microfluidic droplet generator, the adjustable-microfluidic droplet generator, and the electro-spraying microfluidic chip were successfully developed in this study. First, the gradient-microfluidic droplet generator uses the micro-mixers and flow-focusing devices to generate the different sizes of the droplets with different concentrations simultaneously and applies these microcapsules for drug release. The sizes of these four types of droplet with different concentrations are uniform and can be precisely controlled by adjusting the aqueous phase flow rate and oil phase flow rate. Moreover, Ca-alginate microcapsules with different concentrations of the bovine serum albumin (BSA) are used for drug release, and the Ca-alginate microcapsule size is from 60 to 105 µm in diameter. The gradient-microfluidic droplet generator has the advantages of actively controlling the droplet diameter, simultaneously generating uniform size droplets with different concentrations, and having a simple process and a high throughput. Second, the adjustable-microfluidic droplet generator uses the micro-mixer and flow-focusing device to produce the aqueous droplets with different trypan blue concentrations under the various flow rate ratios of the trypan blue solution (sample phase 1, w1) and the D.I. water (sample phase 2, w2) and applies these microparticles for encapsulating the magnetic nanoparticles. The chitosan emulsions with eleven different concentrations are very uniform, and the chitosan emulsion size can be precisely controlled by adjusting the flow rate of the sample phase sum (w1+w2) and oil phase flow rate. Moreover, chitosan microparticles with different concentrations of the magnetic nanoparticles are used for uniform size, and the chitosan microparticles size is from 44 to 83 µm in diameter. The adjustable-microfluidic droplet generator has the advantages of actively controlling the droplet diameter, generating uniform size droplets with different concentrations, and having a simple process. Third, an electro-spraying microfluidic chip was integrated with a parallel electrode and flow-focusing device to successfully generate uniform emulsions with an electric field. This approach utilizes a high electric field driven by a direct-current voltage to form a stable Taylor cone in the flow-focusing position. The Taylor cone can then generate stable and uniform emulsions that are less than 5 µm in diameter. The emulsion size is controlled by the surfactant concentration, the ratio of the aqueous and oil phase flow rates and the strength of the electric field. When the strength of the electric field increases at a high surfactant concentration and low ratio of flow rates, the Taylor angle decreases, which causes the emulsion size to decrease. In this study, the aqueous emulsion diameter ranged from 1 µm to 98 µm, and the poly(lactic-co-glycolic acid) (PLGA) emulsion size ranged from 7 to 70 µm. The microfluidic chip developed in this work has the advantages of actively controlling the emulsion size and generating uniform emulsions (the relative standard deviation was less than 10%) and represents a new emulsion generation process. These preparation approaches for generating the biomaterial microcapsules of different concentrations and for generating the smaller biomaterial microcapsules size will provide many potential applications for drug delivery and pharmaceutical area.