Preparation of Silk Fibroin Nanofibres by Needleless Electrospinning using Formic Acid-Calcium Chloride as the Solvent Nongnut Sasithorn 1,2,a* , Rattanaphol Mongkholrattanasit 2,b* and Lenka Martinová 3,c 1 Department of Nonwovens and Nanofibrous Materials, Faculty of Textile Engineering, Technical University of Liberec, Liberec, Czech Republic 2 Textile Chemical Technology Department, Faculty of Industrial Textiles and Fashion Design, Rajamangala University of Technology Phra Nakhon, Bangkok, Thailand 3 Institute for Nanomaterials, Advanced Technology and Innovation, Technical University of Liberec, Liberec, Czech Republic a nongnut.s@rmutp.ac.th, b rattanaphol.m@rmutp.ac.th, c lenka.martinova@tul.cz Keywords: needleless electrospinning, silk electrospun fibres, formic acid, calcium chloride Abstract. In this study, silk nanofibre sheets were prepared by a needleless electrospinning from silk fibroin in a mixture of formic acid and calcium chloride. The influences of the concentration of calcium chloride on the properties of spinning solution, morphology of the silk electrospun fibres and the spinning performance of the spinning process were examined. The results show that calcium chloride can improve the solubility of silk fibroin in formic acid. The morphology of electrospun fibres was characterized by a scanning electron microscope (SEM), which indicates that the morphology of obtained fibres was influenced by the weight ratio of silk fibre to calcium chloride in the spinning solution. It was observed that the concentration of calcium chloride in the spinning solution influenced the diameter of the silk electrospun fibres, with an increase in the concentration of calcium chloride increasing the diameters of the electrospun fibres. The silk nanofibres had diameters ranging from 440 to 1900 nm. However, increasing the concentration of calcium chloride in the spinning solution had a less influence on the spinning performance of electrospinning process. Introduction Needleless electrospinning systems have been developed recently. In needleless electrospinning, instead of the generation of a polymer jet from the tip of the needle, polymer jets form from the surface of free liquid by self-organization [1-3]. For example, Jirsak et al. [2] invented a needleless electrospinning system using a roller or cylinder as the fibre generator, which was commercialized by Elmarco Co. (Czech Republic) with the brand name “Nanospider.” The roller electrospinning device contains a rotating cylinder electrode, which is partially immersed in a polymer solution reservoir. When the roller slowly rotates, the polymer solution is loaded onto the upper roller surface. Upon applying a high voltage to the electrospinning system, a number of solution jets are simultaneously generated from the surface of the electrode, thereby improving fibre productivity [3]. Silk is a fibrous protein produced by a variety of insects, including the silkworm. It is a candidate material for biomedical applications because it has good biological compatibility, in addition to being biodegradable and having minimal inflammatory reactions. Various forms of silk fibroin, such as gels, powders, and nonwoven membranes can be regenerated by dissolution, followed by recovery [4-6]. In order to regenerate silk fibre, the preliminary dissolution of silk fibre is required to prepare the solution. Silk fibres dissolve only in a limited number of solvents due to a large quantity of glycine and amino acids with hydrocarbon side chains in fibroin. Silk fibroin can be dissolved in concentrated aqueous solutions of acids (phosphoric acid, sulphuric acid and hydrochloric acid) and in high ionic strength aqueous salt solutions such as lithium bromide, calcium chloride, zinc chloride, magnesium chloride [7]. The main disadvantage of a salt-containing aqueous solvent is the long preparation time because aqueous solutions of fibroin have to be dialyzed for several days to remove the salts and to recover the polymer as films, sponges, or powder from the aqueous solution by dry Applied Mechanics and Materials Submitted: 2015-09-06 ISSN: 1662-7482, Vol. 848, pp 203-206 Revised: 2016-01-20 doi:10.4028/www.scientific.net/AMM.848.203 Accepted: 2016-03-24 © 2016 Trans Tech Publications, Switzerland 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, www.ttp.net. (#68404514-01/07/16,17:00:52)