整合製備相轉移材料微膠囊之同心毛細管微流道系統開發研究

Abstract

以雙乳化液滴產生微球膠囊的方法主要分為化學法及物理法兩種。前者以批次合成產生，可大量製備；但有尺寸均勻性較差、製作程序較複雜之缺點；後者則於微流道中以不同流體間之剪切力來產生，在尺寸均勻性及可調變性上皆優於前者，但產生之微球尺寸偏大尚無法達到奈米等級，且在學界尚無法進入量產。受限於微製程技術，目前學界以物理法產生微膠囊仍以平面微流道為主，其有黏壁與不易操作之缺點，故本研究開發了方法以克服上述技術瓶頸。近年來在改善能源運用效率與開發綠色儲能議題中，相轉移材料的可能應用研究備受矚目，本研究將新式同心毛細管微流道及其下游固化與收集系統垂直整合，可成功製備高包覆率及產率的相變微膠囊。 本研究藉由光起始方法將雙乳化液滴快速在流道內固化，以產線式製備相變微膠囊，並提出了兩套同心毛細管微流道製備相變微膠囊技術：1.微二相流同心毛細管流道系統-結合物理的流道產生單乳化液滴並藉由化學的相分離來製備；2. 微三相流同心毛細管流道系統-全物理法，藉由流道產生雙乳化液滴直接製備核殼式包覆的微膠囊。本研究分三個階段來達成，階段一：新式微二相流同心毛細管流道系統開發，可產生尺寸範圍20-500μm且粒徑均一(CV < 3%)之單乳化液滴，並建立一力學模型來描述流量與幾何參數對液滴尺寸之影響，推導出線性回歸方程式可用於預測液滴尺寸與設計微流道幾何尺寸，免去一般微流實驗慣用之耗時耗工的試驗法。階段二：高功率面式UV燈及固化系統開發並將其與同心微流道垂直整合，可將同心微流道產生之MMA液滴於5秒內快速固化成MMA微球。此外也找到與正十六烷相溶程度不同之架橋劑，應用於階段三兩種製備相變微膠囊的系統(方法一使用EGDMA為架橋劑，可使殼材與核材互溶；方法二使用DPHA為架橋劑，可使殼材與核材不相溶)。階段三：(方法一)建立了一新穎的概念，結合化學與物理法以微二相流同心毛細管微流道製備相變微膠囊，可連續式生產最高包覆率達50%之相變微膠囊，且可即時調整微膠囊尺寸範圍由20-500μm(CV< 3%)；(方法二)將微二相流同心流道串聯兩組開發出微三相同心流道，此系統為首例成功以三相流同心流道一次性產生雙乳化液滴來製備相變微膠囊。藉由內中相流量比，可即時調整核殼比製備出不同包覆率之微膠囊；而調整外相流量可即時控制微膠囊尺寸範圍從60-500μm 且均勻度CV ≤ 1.5%。 總結而論本研究所開發之同心毛細管微流道整合系統具有下列特色與優勢：可即時調變微膠囊尺寸(20μm-500μm)且尺寸均勻度(方法一CV < 3%；方法二CV ≤ 1.5%)、可即時調變微膠囊包覆率且包覆率> 70%、流道不需表面改質、流道尺寸不受限於市售套管而可任意製作所需尺寸、不需特定之介面活性劑(所需濃度低)來穩定系統、同心毛細管流道可多組串聯推廣至多乳化液滴製備，最後更可推廣至因應不同材料之包覆，製備出殼層極薄的微膠囊，並應用在各工程領域上。

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.