Fabrication of Aligned Fibrous Arrays by Magnetic Electrospinning

This Communication demonstrates a method that generates parallel fibers via electrospinning (ES) magnetic-particledoped polymers in a magnetic field. ES is a simple method for generating ultrathin fibers with diameters ranging from tens of nanometers to tens of micrometers. ES possesses several attractive features: comparatively low-cost, relatively high production rate, the ability to generate materials with large surface area-to-volume ratios, and applicability to many types of materials. These features have enabled many applications. During electrospinning, the fibers deposited on the collector are typically randomly oriented in the form of nonwoven mats. It is desirable to generate periodic structures to broaden the applications of ES. For example, in the fabrication of electronic and photonic devices, well-aligned and highly ordered architectures are often required. For application of fiber-reinforced polymer composites, the alignment of fibers can improve mechanical properties. Well-ordered fibers may also be suitable for many applications in tissue engineering. There have been a few approaches to improving the orderliness of electrospun fibers. Matthews et al. used a rotating mandrel as a ground target to collect fibers. By controlling the rotation speed of the mandrel, they obtained collagen fibers aligned along the axis of rotation. Katta et al. employed a macroscopic copper wireframed rotating drum as the collector, and the electrospun fibers collected on the drum as it rotated were parallel to each other. Theron et al. described an electrostatic field-assisted assembly technique using a tapered and grounded wheel-like bobbin to position and align individual nanofibers into parallel arrays. Because the edge of the bobbin was relatively sharp, this technique could not fabricate well-aligned nanofibers over large areas. Li et al. fabricated parallel arrays made of polymeric and ceramic nanofibers using a collector consisting of two pieces of electrically conductive substrate separated by a gap. To sum up, existing strategies for making parallel electrospun fibers include modifying the collectors and manipulating the electrical field. These methods can fabricate more or less aligned fibers; however, they still have some drawbacks. Modifying the collectors, such as rotating drums, is a timeand energy-consuming method; moreover fibers fabricated by this method are poorly aligned and cannot be conveniently transferred to different types of substrates. Methods based on electrical fields do not seem to achieve the fabrication of aligned fibers over large areas. It is therefore necessary to explore new and more reliable methods that generate wellaligned electrospun polymeric fibers over large areas. Herein, we report a facile and effective approach to fabricating well-aligned arrays and multilayer grids by a technique called magnetic electrospinning (MES; Scheme 1), where magnetized fibers are stretched into essentially parallel fibers over large areas (more than 5 cm × 5 cm) in a magnetic field. Compared with other reported methods, MES possesses the following advantages: a) The apparatus is simple and requires only adding two magnets to a conventional setup; b) The C O M M U N IC A TI O N