Abstract:

The preparation of alginate fibers by microfluidic spinning has been recognized in many fields, but the fast gelation reaction limits the flexible regulation of the helical fiber morphology. Regarding this, a series of alginate fibers were prepared in a coaxial capillary microfluidic device. The outer phase was the calcium chloride solution, and the inner phase adopted the mixed aqueous solution of sodium alginate with sodium citrate to reduce the gelation rate. The effects of gelation rate and flow rates of inner and outer phases on the fiber distribution and helical morphology were systematically investigated. The result indicates that the reduction of gelation rate favors the formation of helical fibers and affects the distribution of fibers such as straight, helical, wavy, and blocked. Furthermore, two types of helical fibers, namely thick and thin helical fibers, are recognized. Their morphological characteristics show significant differences in relation to the gelation rate and two-phase flow rates. By comparison, the diameter and pitch of thick helix, and the amplitude of thin helix are more vulnerable to the gelation rate and two-phase flow rates. The gelation rate and shear force are the dominant factors regulating the pitch of thick and thin fibers, respectively. On this basis, the two helical fibers can be well distinguished by the relation of pitch and the inner/outer rate ratio.

Key words: microfluidics, gels, morphology, sodium alginate, helical fiber, morphology regulation

摘要：

微流控纺丝技术制备海藻纤维已在诸多领域得到认可，但快速凝胶反应限制了螺旋纤维形貌的灵活调控。鉴于此，采用同轴环管毛细管微流控装置制备海藻纤维，外相为氯化钙溶液，内相为海藻酸钠溶液，通过添加柠檬酸钠降低凝胶反应速率，并系统考察了凝胶速率和内外相流量对纤维分布和螺旋形貌的影响。结果表明，凝胶速率降低有利于螺旋纤维形成，并影响直线、螺旋、波浪和堵塞等纤维分布。实验发现粗细两种螺旋纤维，其形貌特性与凝胶速率和两相流量的关系存在显著差异。经比较，粗螺旋直径和螺距、细螺旋振幅对凝胶速率和两相流量的影响更为敏感。凝胶速率和剪切力分别是调控粗、细螺旋螺距的主导因素，利用螺距与内外流量比可很好划分两种螺旋纤维。

关键词: 微流体学, 凝胶, 形态学, 海藻酸钠, 螺旋纤维, 形貌调控