A Belt-like superfine film fabricated by bubble-electrospinning Hao Dou 1,a, Bao-qi Zuo 1

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1 Advanced Materials Research Online: ISSN: , Vol. 843, pp doi: / Trans Tech Publications, Switzerland A Belt-like superfine film fabricated by bubble-electrospinning Hao Dou 1,a, Bao-qi Zuo 1 1 National Engineering Laboratory for Modern Silk, College of Textile and Clothing Engineering, Soochow University, 199 Ren-ai Road, Suzhou, China a douhaosuda@126.com Keywords: bubble-electrospinning, silk fibroin, belt-like structure Abstract. A belt-like superfine silk fibroin film was prepared via bubble-electrospinning from aqueous silk fibroin solution at concentration 15%. The morphology of film structures were characterized by scanning electron microscope (SEM). The average width was 1.17 micronmeters and the thickness was 377 nanometers. Introduction In recent years, much attention has been paid to the electrospinning method for the reason that it can make superfine fibers in the quickest and simplest way and lots of applications benefit from the large specific surface area and high porosity of the electrospun nanofibers[1]. As a derived way, bubble-electrospinning improves the production and enlarges the kinds of electrospun polymers by overcoming the surface tension of a polymer bubble, which offers a promising opportunity for mass production of superfine fibers[2]. As an excellent candidate of abundent and low-cost biomaterials, silk fibroin has been extensively studied due to its distinctive properties such as biocompatibility, degradability and excellent mechanical properties[3].in order to avoid the common use of toxic solvents like hexafluoro-2-propanol (HFIP) and formic acid, different kinds of approaches such as concerntrating high aquous silk fibroin solution(>25%)[4], adjusting ph[5]and incorporating silk fibroin with polyethylene oxide (PEO)[6] have been developed in the electrospinning silk fibroin nanofibers for its fascinating bioapplication. In this research, bubble-electrospinning was introduced to fabricate superfine silk fibroin films with deionized water as a solvent and a flat belt-like film was obtained successfully from such an aqueous solution at a relatively low concentration15%. Experimental Part Materials. Raw silk was degummed three times with 0.5% (w/w) Na 2 CO 3 solution at 100 for 30 min and then washed with distilled water. Degummed silk fibroin (SF) was dissolved in 9.3 mol /L LiBr solution. After dialysis in cellulose tubular membrane (molecular weight cutoff= 8000~14000, Sigma, USA)against distilled water for 3 days and filtration, the final SF aqueous solution with concentration about 3.5% was obtained. Preparation of the spinning solution and the bubble electrospinning process. The aqueous SF solution was heated and concentrated at temperature 45 in order to acquire the concentration 15% used in this study, which was determined by weighing the remaining solid after drying. Then the prepared SF solution was carried out by a bubble electrospinning apparatus developed in our lab under voltage 12kV and distance between nozzle and collector 10 cm. The schematic was shown in Fig.1. Characterization. The morphology of electrospun films were observed with scanning electron microscopy (SEM, S-4800, Hitachi, Tokyo, Japan) at 20 and 60% relative humidity. All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans Tech Publications, (ID: , Pennsylvania State University, University Park, USA-04/03/16,02:53:16)

2 Advanced Materials Research Vol Fig.1The experimental set-up of the bubble-electrospinning Fig.2 SEM of the belt-like superfine fiber(showing the thickness) Fig.3 SEM of the belt-like superfine fiber(showing the width) Results and Discussion. Fig.4 SEM of a 3D spiral superfine fiber According to the SEM photographs shown in Fig.2 and Fig.3, it can be observed that belt-like superfine films with smooth surface were produced by bubble-electrospinning aqueous silk fibroin solution. The average width was 1.17±0.12micronmeter and the thickness was ±95.62

3 84 Frontiers of Nanofiber Fabrication and Applications nanometer. Many researchers [7-9]considered that the elongation of the jet and evaporation rate of the solvent both changed the shape and the charge per unit area carried by the jet, which determind the final morphology of outcomes. The belt-like morphology may resulte from the presence of a thin, mechanically distinct bubble film generated from rupture of polymer bubbles. From Fig.4, a 3D spiral superfine ribbon was found, which seemed to show the moving path of charged liquid jet. It was well known that the instability behavior [10-11]often occurred in the electrospinning process(shown in Fig.5), depending upon the fluid parameters and the operating conditions. In another word, the ribbon-shape films often bent, in a regular way as a result of the electrically driven bending instability. Conclusion. Fig.5 The sketch of instability behavior in the electrospinning Silk fibroin nanofibers has been explored for wide applications, such as high-performance filters and biomaterial scaffolds for vascular grafts or wound dressings. Bubble-electrospun fibers without any chemical solvent provide benefits due to avoiding toxicity toward organisms. Furthermore, since the morphology of a material plays a significant role in properties and applications, belt-like superfine films would open new directions in the future. Acknowledgment The work is supported by Priority Academic Program Development of Jiangsu Higher Education Institutions (PAPD), National Natural Science Foundation of China under grant No and Project for Six Kinds of Top Talents in Jiangsu Province under grant No. ZBZZ-035, Science & Technology Pillar Program of Jiangsu Province under grant No. BE , Natural Science Foundation of the Jiangsu Higher Education Institutions of China under grant No. 12KJB130002, Jiangsu Provincial Natural Science Foundation of China under grant No. BK References [1]B. Nandana,C.K.Subhas, Electrospinning: A fascinating fiber fabrication technique, Biotechnology Advances, 28 (2010) [2] Y. Liu, J.H. He, Bubble electrospinning for mass production of nanofibers, Int J Nonlinear Sci Numer Simulat, 8 (2007) [3] H.Cao,X. Chen, L. Huang, Z.Z. Shao, Electrospinning of reconstituted silk fiber from aqueous silk fibroin solution, Materials Science and Engineering C, 29 (2009) [4] H. Wang, Y.P. Zhang, H.L.Shao, X.C. Hu, Electrospun ultra-fine silk fibroin fibers from aqueous solutions, Journal of Material Science, 40(2005)

4 Advanced Materials Research Vol [5] J.X. Zhu, H.L. Shao, X.C. Hu, Morphology and structure of electrospun mats from regenerated silk fibroin aqueous solutions with adjusting ph, International Journal of Biological Macromolecules, 41 (2007) [6] H.J.Jin, V.F. Sergey, C.R. Gregory, et al. Electrospinning Bombyx mori Silk with Poly(ethylene oxide), Biomacromolecules, 3 (2002) [7] A. Nasim, N. Mahdi, H.K. Mohammad, Effects of Some Electrospinn ing Parameters on Morphology of Natural Silk-Based Nanofibers, Journal of Applied Polymer Science, 113 (2009) [8]N. Yogesh, A.S. Jeffrey, W. Gregg, et al. Electrospinning nanoribbons of a bioengineered silk-elastin-like protein (SELP) from water, Polymer, 50(2009) [9] K. Sureeporn, W.X. Liu, H.R. Darrell, Flat Polymer Ribbons and Other Shapes by Electrospinning, Journal of Polymer Science: Part B: Polymer Physics, 39 (2001) [10] T. Subbiah, G.S. Bhat, R.W. Tock, et al. Electrospinning of Nanofibers, Journal of Applied Polymer Science, 96 (2005) [11] S.A.Theron, E.Zussman, A.L.Yarin, Experimental investigation of the governing parameters in the electrospinning of polymer solutions. Polymer, 45 (2004)

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