Rotating drum collectors

Various collectors and methods have been adopted to obtain aligned fibers a dynamic collector such as a rotating drum (Xu et al. 2004) a pair of parallel conducting electrodes to create an electric field so that the electrospun fibers are preferentially aligned across the gap between the electrodes (Li and Xia 2004) and a wire screen (Wang et al. 2005). Tubular electrospun fibers can be fabricated on a rotating tube and the deposited fiber layer subsequently extracted from the tube. 

Figure 10.18. Schematic representation of electrospinning setup equipped with a rotating drum collector [99]...

The tensile properties can be determined only if the cross section of the specimens is known. In the case of electrospun materials that are deposited on a flat metal collector [106], the area density is not uniform. To avoid this problem, a rotating drum with low velocity is suggested. This slow motion does not affect the orientation of fibers, but the structure has a quasi-constant thickness in the direction of rotation [107], And in this case the linear density in the direction of rotation can also be considered constant. The cross section... 

Fig. 4 Modified electrospinner, a Rotating drum collector, and b the produced aligned nanofibers. Adopted from Pham et al. (2006)...

Figure 4.9 Different types of collectors used in electrospinning (a) flat plate collector (KIdoaki et al. 2005) (6) rotating drum (Wannatong et al. 2004), mandrel (Mo and Weber 2004), rotating disc (Zussman et al. 2003) (c) rectangular, triangular, or wire cylinder frame (Katta et al. 2004) (d) electrode pair arrangements (Li, D., et al. 2003b) (e) single or multiple ring electrodes (Dalton et al. 2005) (f) mesh electrode (U.S. patent 6,110,590, Aug. 2000) (g) pair of cone-shaped collectors (Bunyan et al. 2006).

Chew et al. (2005) demonstrated the utility of nanofibers elecirospun fiem copolymers of caprolactone and ethyl ethylene phosphate [P(CL-EEP)] in drug delivery. These were electrospun from 2-12% solutions in CH2CI2 and were loaded with low concentrations ( 1 x 10 " %) of recombinant human P-NGF stabilized in BSA carrier protein. Nanofibers were spun as aligned mats using a rotating drum collector and their BSA-NGF release characteristics were studied over a three-month period. The released protein was shown to be bioactive (using a neurite outgrowth assay on PC-12 cells). 

Collectors used for regulating the fibre collection process (a) rotating roller (b) vibrating plate (c) sharp edged rotating disc (d) frame (e) fork (f) point collector (g) drum. 

The polymer solution was fed at a speed of 2.8 pl/min through needles with an outer diameter of 0.7 mm. A 9 kV voltage was applied between the two needles while the nozzle distance was 10 cm. The tip-to-collector distance was 15 cm. The rotation speed of the drum was changed from 31.5 to 103.5 RPM. The bulk porosity of nanofibre mats was measured by Equations 2.1 and 2.2 ... 

The resultant ink was electrospun from an 18 gauge steel needle at a distance of 150 mm from the ground collector, which was a multiple wire drum rotating at 2 rpm. The electrospinning took place under a potential of 20 kV, while the MWNT - PVA ink was fed by a syringe pump at a constant flow rate of 4 ml/h. After 20 min of electrospinning, a fibrous mat of 300 x 810 mm was fabricated and left to dry for 24 hours. 

Figure 10.14. Electrospinning apparatus which operates with wire electrode [91]. 1 electrospinning solution, 2 take-up drum, 3 wire electrode, 4 electrospinning space, 5 collector, 6 rotating mandrel...

One-dimensional electrospun structures can be created by stretching the nanofibrous fibers during their formation. In the case of the stretching technique, the diameter of the nanofibers can be reduced and excellent orientation can be obtained [98]. A rotating disk or drum [99] (Figure 10.18) can be applied as a collector where fibers axe deposited on... 

Two perpendicular rotating disks can be used as a collector system [104] instead of one. In the case of the two disks, the fibers cannot stick to the first one and the other disk can continuously wind up the yarn. The orientation and twisting of fibers occur between the drums. Potentially infinite twisted yarns can be produced, with relatively high (approx. 10 m/s) haul-off. 

---