“一步法”微流控制备大直径复合乳粒中几何尺寸调控规律研究

Controlled size production of large double droplets in one-step microfluidic devices

复合乳粒几何尺寸的精密调控对于实现特定规格参数要求的聚合物空心微球的可控制备具有重要意义。基于"一步法"微流控装置,通过大量的实验获得了以油相与内水相流量比R和连续相毛细管数Ca为变量的复合乳粒构建操作区域图,并在能稳定形成复合乳粒区域范围内探讨了Ca、R以及管道尺寸对大直径复合乳粒几何尺寸的影响规律。实验结果表明:随着连续相毛细管数增大,复合乳粒几何尺寸(内径、外径和壁厚)均减小;随着油相与内水相流量比增大,复合乳粒内径减小,壁厚增大,而外径则呈现先减小后增大的趋势。此外,复合乳粒几何尺寸随管道直径增大而增大,且存在极限尺寸。实验结果可为单分散大直径复合乳粒的定量可控制备提供实验设计依据。

The precise regulation of the composite latex geometry is important for the controllable preparation of polymer hollow microspheres to achieve specific specifications.Based on one-step microfluidic device,extensive experiments for double droplet preparation are conducted and the flow pattern diagram dependent on capillary number of continuous phase,CaW2,and the flow rate ratio of oil phase to inner phase,RO/W1,is obtained,and further the effects of the Ca,RO/W1 and the diameter of external phase tube on the large double droplets size are discussed in this work.As CaW2 increases,the droplet sizes,regarding inner diameter,shell thickness and outer diameter,decrease because of a large drag force generated by a continuous phase.With the RO/W1 increasing,the inner diameter decreases,while the shell thickness increases.However,as for the outer diameter of such double droplet,it initially decreases and then increases.In addition,the droplet sizes increase as the tube diameter increases under the same flow rate of all three phases,but it is always limited by the tube diameter.The present work could provide some guidelines for controllable and precise fabrication of double droplets with large diameter.