On the Microencapsulation for Phase Change Material by Concentric Capillary Microfluidic System
Date Issued
2015
Date
2015
Author(s)
Chen, Yi-Ting
Abstract
There are mainly two methods to generate double emulsion micro-capsules, i.e.,chemical and physical method. Most micro-capsules were produced by the former method, which is batch-based production by chemical synthesis. Wide size-distributions of micro-capsules and complicated operation processes are the main issues in this traditional synthesis process. By the latter, double-emulsion can be generated in a microfluidic channel based on the separation mechanisms of flow shearing and brought significant advantages of size uniformity and operation flexibility than the chemical one. However, few studies were focusing on the processes of double emulsion; moreover, most of them used the two-dimensional plane-channels due to the difficulties of traditional micro-manufacturing. By using the plane channel to produce emulsion droplets, it commonly suffers the interactions between the dispersed liquid and wall surfaces and also the complexity of treatments for channel surface. Recently, the phase change materials have drawn significant attentions for the improvement of energy efficiency and the green energy storage. Nevertheless, there is still no study on the fabrication of microencapsulated phase change materials (MPCMs) by microfluidics. Here, in this study is going to develop a new technique for producing micro-capsules of double-emulsions by using non-planar axisymmetric concentric micro-channels with capillary tube . In this study, a new MPCMs fabrication process is developed by microfluidic. The MPCMs of n-hexadecane covered by PMMA shell is fabricated by micro two phase flow for generating microdroplets. This research will control the size of MPCMs by changing flow rate ratio of continuous phase and dispersed phase and control the core/shell ratio by changing the weight ratio of n-octadecane and MMA for dispersed phase. The co-flow geometry is used in the micro two phase flow chip design and a new co-flow chip fabrication is developed.co-flow can avoid wetting problem due to hydrophilic/hydrophobic chip materials. Traditionally, commercial tubes and connectors are used for co-flow chip, but the dimension of channel size and droplets size are limited. The new fabrication can adjust channel size easily and can generate 20-30μm droplets。This study will build a complete and new micro-two phase flow generation and curing system for MPCMs which is different from traditional chemical fabrication. The disadvantages of chemical fabrication are complex operating parameters, time consuming and higher cost. And the new MPCMs fabrication by microfluidic is easy operating parameters, uniform MPCMs size and lower cost for the need of different size and absorb/release ability MPCMs in applications.
Subjects
multiple phase flow
concentric capillary microfluidic System
integrated microfluidic device
double-emulsions
microencapsulation
microPCMs
SDGs
Type
thesis
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