同轴静电纺丝技术及其应用
图中数据表明：
1.2012年发表的电纺丝文献中，同轴静电纺丝相关文献仅占总数的3.54%。
2.在发表的42篇同轴静电纺丝相关文献中，中国有21篇，占50%。说明国内对这一领域的关注度正在提高。
3.以下是对同轴静电纺丝相关文献的摘要及总结，供读者参考。
传统的静电纺丝设备都是使用单一的毛细管状喷头喷丝，因此通常用于制备实心且表面光滑单一组分的纳米纤维，但是这种方法只能得到单一材料的纳米纤维，且存在缺乏表面特异性、力学性能较差、降解速率难以控制等问题，无法得到具有多种功能性结构的复合材料，应用范围较窄，很难应用于生物医学组织工程等领域。于是开始做同轴静电纺丝，它是在传统静电纺丝技术上发展起来的新方法，单步即可制备连续的核—壳和中空结构纳米纤维。同轴静电纺时，将核层和壳层材料的溶液分别装在两个不同的注射器中，喷丝系统由两个同轴但是不同内径的毛细管组成，在高压电场作用下，外层液体流出后与核层液体汇合，固化前两种液体不会混合到一起。壳层液体经高频拉伸，高速喷射时内外层溶液交界面讲产生强大的剪切应力，核层溶液在剪切应力作用下，沿着壳层同轴运动，弯曲甩动变形并固化成为超细同轴复合纳米纤维。若将核层材料通过加热或溶解去掉，留下壳层材料，即得到中空纤维。2002年国外的Loscertales发明了第一台同轴静电喷雾设备，并成功应用该技术将水溶性药物包覆于胶囊里。2003年，孙（SUN）等在国内最早通过同轴静电纺丝技术制备出核—壳结构纳米纤维并指出这种核—壳纤维可以应用于过滤器、光学以及微电子学等领域，这可以说是国内的同轴静电纺丝技术的研究首开先河。随后，各个研究组通过改变溶液、溶液浓度以及喷丝头直径、纺丝条件等，获得了可应用于不同领域的、不同直径的纳米结构纤维，通过查阅各种文献以及自身研究经验，在技术上也有了很大的改进。例如，改变喷丝头结构，由原来的单通道纳米纤维发展到多通道纳米纤维。赵（Zhao）等在原来单根内管的基础上，采用数量连续增加的方法，制备出数量可控的多通道微/纳米管，通道数量可多达5-6个。
近两年，同轴静电纺丝技术制备纳米纤维已成为研究热点，被越来越多用于组织工程、药物控释、太阳能电池等。
夏（Xia）等研究了以矿物油为核层纺丝液，聚乙烯吡咯烷酮和Ti（OiPr）4的乙醇溶液为壳层溶液同轴静电纺丝制得核-壳结构的微/纳米复合纤维，再以辛烷萃取除去核层的矿物油，最后通过500℃高温煅烧除去纤维中的有机成分获得了具有高强度、高刚度的中空TiO2微/纳米纤维。这种中空纤维一般用于人造血管、多组分药物缓释和催化剂等方面。
徐（Xu）等采用同轴静电纺丝技术，制备了大量直径在200-300nm（如下图）之间，表面光滑的CeO2纳米管，并在600℃焙烧后，得到了晶态CeO2纳米管。其具有较高的催化活性，可望作为催化剂用于吸附、分解、降解有害物质等。另外，也可用于制备其它一维管式无机纳米材料的方法。
余（Yu）以水溶性聚合物聚乙烯吡咯烷酮为成纤基材，豆腐果苷为难溶药物模型，采用同轴静电纺丝技术制备具有芯鞘结构的载药纳米纤维型固体分散体。体外溶出实验表明纤维中豆腐果苷在60s内完全释放，载药纳米纤维能明显提高药物溶解度，为难溶药物的速溶、速效、脉冲、多级给药系统研发提供新策略和途径。
表3 同轴静电纺丝被引频次较高的文献两相材料摘要
参考文献：
1. Li, D.; Babel, A.; Jenekhe, S. A.; Xia, Y. N., Nanofibers of conjugated polymers prepared by electrospinning with a two-capillary spinneret. Advanced Materials 2004, 16 (22), 2062-+.
2. Li, D.; McCann, J. T.; Xia, Y. N., Use of electrospinning to directly fabricate hollow nanofibers with functionalized inner and outer surfaces. Small 2005, 1 (1), 83-86.
3. Sun, Z. C.; Zussman, E.; Yarin, A. L.; Wendorff, J. H.; Greiner, A., Compound core-shell polymer nanofibers by co-electrospinning. Advanced Materials 2003, 15 (22), 1929-+.
4. Zhang, Y. Z.; Wang, X.; Feng, Y.; Li, J.; Lim, C. T.; Ramakrishna, S., Coaxial electrospinning of (fluorescein isothiocyanate-conjugated bovine serum albumin)-encapsulated poly(epsilon-caprolactone) nanofibers for sustained release. Biomacromolecules 2006, 7 (4), 1049-1057.
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7. Zhang, Y. Z.; Huang, Z. M.; Xu, X. J.; Lim, C. T.; Ramakrishna, S., Preparation of core-shell structured PCL-r-gelatin Bi-component nanofibers by coaxial electrospinning. Chemistry of Materials 2004, 16 (18), 3406-3409.
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13. McCann, J. T.; Marquez, M.; Xia, Y., Melt coaxial electrospinning: A versatile method for the encapsulation of solid materials and fabrication of phase change nanofibers. Nano Lett. 2006, 6 (12), 2868-2872.
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15. Zeng, J.; Xu, X.; Chen, X.; Liang, Q.; Bian, X.; Yang, L.; Jing, X., Biodegradable electrospun fibers for drug delivery. J. Control. Release 2003, 92 (3), 227-231.
表4 早期和近期同轴静电纺文献两相材料摘要
参考文献：
1. Sun, Z. C.; Zussman, E.; Yarin, A. L.; Wendorff, J. H.; Greiner, A., Compound core-shell polymer nanofibers by co-electrospinning. Advanced Materials 2003, 15 (22), 1929-+.
2. Li, D.; Xia, Y. N., Direct fabrication of composite and ceramic hollow nanofibers by electrospinning. Nano Lett. 2004, 4 (5), 933-938.
3. Li, D.; McCann, J. T.; Xia, Y. N., Use of electrospinning to directly fabricate hollow nanofibers with functionalized inner and outer surfaces. Small 2005, 1 (1), 83-86.
4. Zhang, Y. Z.; Huang, Z. M.; Xu, X. J.; Lim, C. T.; Ramakrishna, S., Preparation of core-shell structured PCL-r-gelatin Bi-component nanofibers by coaxial electrospinning. Chemistry of Materials 2004, 16 (18), 3406-3409.
5. Lu, Y.; Jiang, H. L.; Tu, K. H.; Wang, L. Q., Mild immobilization of diverse macromolecular bioactive agents onto multifunctional fibrous membranes prepared by coaxial electrospinning. Acta Biomater. 2009, 5 (5), 1562-1574.
6. Zhang, Y. X.; Rutledge, G. C., Electrical Conductivity of Electrospun Polyaniline and Polyaniline-Blend Fibers and Mats. Macromolecules 2012, 45 (10), 4238-4246.
7. Dong, H.; Nyame, V.; Macdiarmid, A. G.; Jones, W. E., Polyaniline/poly(methyl methacrylate) coaxial fibers: The fabrication and effects of the solution properties on the morphology of electrospun core fibers. Journal of Polymer Science Part B-Polymer Physics 2004, 42 (21), 3934-3942.
8. He, C.; Huang, Z.; Han, X.; Liu, L.; Fu, Q.; Hu, Y.; 黄争鸣; 韩晓建; 刘玲; 付强; 胡影影, Core-shell ultrafine electrospun fibers for drug release applications. High Technology Letters 2006, 16 (9), 934-938.
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14. Tang, C.; Ozcam, A. E.; Stout, B.; Khan, S. A., Effect of pH on Protein Distribution in Electrospun PVA/BSA Composite Nanofibers. Biomacromolecules 2012, 13 (5), 1269-1278.
15. Yu, D. G.; Chatterton, N. P.; Yang, J. H.; Wang, X.; Liao, Y. Z., Coaxial Electrospinning with Triton X-100 Solutions as Sheath Fluids for Preparing PAN Nanofibers. Macromol. Mater. Eng. 2012, 297 (5), 395-401.
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表3和表4数据说明：
1.静电纺核-壳结构纳米纤维应用最多是生物医学领域，其次是光电及能源领域。
2.在核层和壳层材料的选择方面，性能较好的聚乙烯醇、具有生物可降解性和相容性的聚乳酸是被选用频率比较高的。近期应用较多的是聚己内酯。
