Rotating cylinder collectors

Chen et aZ. obtained fibres by using a rotating cylinder as collector at a line speed of 18 m min , with flow-rate 0.1 mL h , 10 kV of voltage and a distance between the needle and the cylinder about 100 mm. They obtained... 

A flat plate collector is the most used to collect the fibers. It may be a metal plate such as a sheet or screen [25]. There are methods that use a rotating cylinder to collect the fibers [26]. A fiber spool can be obtained if the angular velocity of the cylinder is combined with the speed of fiber emission. Usually the random behavior of the jet whipping limits the ability of the fibers aligning completely, causing twists and overlaps. 

Fig. 4.14 Schematic diagrams of different collectors a rotating cylinder collector, b rotating cylinder collector with a back electrode, c rotating disk collector and d wire drum collector. Reproduced from Refs. [ 188, 185, 186, 189], respectively...

The rale of collection of Brownian particles under the influence of interaction forces between the collector surface and the particles is calculated by (a) incorporating the interaction forces in the rate constant of a virtual, first order, chemical reaction taking place on the surface of the collector, and by (b) solving the convective diffusion equation subject to that chemical reaction as a boundary condition. Several geometries (sphere, cylinder, rotating disc) are considered for the collector. 

The Biostream rotationally stabilized free-flow electrophoresis device, based on the Philpot-Harwell design (Figure 4), uses an annular geometry stabilized against radial convection by rotation of the outer cylinder. Carrier buffer and feed are injected at the base of a vertical annulus and move axially upward to fraction collectors at the top. 

Andrady et al. [89] patented a spinneret configuration which also operates with plenty of capillary holes. The scheme can be seen in Figure 10.12. Holes are located on cylinder superficies and the collector is also cylindrical and concentric with the spinneret. The solution can be fed into the spinneret through a conduit or even manually. The flow rate can be regulated by adjusting the rotation speed and/or the pressure within the spinneret tube. High output rates can be achieved, but the collector surface is limited or can be extended only in a complicated way. 

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).

Yarns are continuous fibre bundles with the fibres partially oriented. The preparation of yarn has been based on either an in situ or a postspinning twisting process. The preparation of a continuous nanofibre yam consists of a special deposition system which collect the fibres continuously and twists in sequence so as to form a continuous yarn. A metal cylinder (Ko et al., 2003) and a funnel-like collector (Kim et al., 2003) have been employed for this purpose, and when the nanofibres are electrospun to the inner side of the collector, they are drawn mechanically, or with the aid of vacuum, into a continuous thread, and twisted by rotating the collector or by using an additional twisting system, to form a continuous yam (Fig. 5.9). 

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