Matrix Arrangement of Three-Dimensional Sheath Flow for Multiple Component Nanofibers

Multiple core-sheath flow was realized using matrix arrangement of 3D sheath flows. The sheath flow was hydrodynamically formed in a flow shift area which has symmetrical microgrooves on channel walls. Vertical and horizontal alignments of the sample streams are a key element of matrix configuration. The flow shift areas were connected in parallel to achieve horizontal alignment of the sheath flow. The cascade connection of the flow shift areas is used for vertical alignment of the sheath flow. In order to achieve matrix arrangement of core-sheath flow, combination of the parallel and cascade connections was utilized. In this work, the horizontal and vertical configurations of the 2-sample sheath flow were demonstrated. Two streams of the vertically aligned 2-sample sheath flow were joined horizontally, and, as a result, 4-sample core-sheath flow of matrix configuration was obtained successfully. 1. Introduction Nanofiber is a potentially useful material in various fields [1], and electrospinning is a simple way to fabricate nanofiber. In this method, syringe and needle are commonly used to feed materials in a high electric field. Control of properties of nanofiber, such as physical, chemical, and mechanical properties, is one of the key issues for practical application. Multiple component nanofiber which composed of various kinds of materials with different properties is effective in achieving control of properties. In order to obtain multi-component nanofibers by electrospinning, several kinds of materials should be transferred at the same time to the electric field without mixing. However, it is difficult for a syringe to transfer all the samples separate from each other. Emulsion has been utilized to fabricate bicomponent fibers [2]. However, because of discontinuity of the droplet, the formed bicomponent region is intermittent and, considering multicomponent, it is very difficult to inject multiple kinds of droplets simultaneously to the high electric field. To realize multiple component fibers by using emulsion, the size, position, and timing of each emulsion droplets should be precisely controlled. Microfluidic devices have been used to fabricate nano-/microscale fibers [3–6]. Laminar flow condition in microchannel is effective in transferring several samples at the same time without mixing. Microfluidic chips have been applied to electrospinning, and continuous bicomponent nanofibers are successfully fabricated [5, 6]. For considering biomedical applications, multicomponent nanofibers with a multiple core-shell configuration are preferable. For