Electrospinning is a simple and versatile method to produce polymer nanofibres by accelerating a charged polymer in a very high electric field. Polymer in solution(or melt) form is loaded in the syringe and is connected to the positive terminal (it also can be negative terminal) of the high voltage power supply. The solution should be pushed at a constant flow rate by the syringe pump. High voltage is used to create an electrically charged jet of polymer solution or melt.


One electrode is connected to the spinning solution/melt and the other attached to the collector. The electric field, positive charge, is concentrated at the tip of the needle that contains a pendant droplet of the solution held by its surface tension. The collector is normally grounded. Charges are induced on the surface of the drop. Mutual charge repulsion and the tendency of the surface charges to move towards the counter electrode, result in an electrostatic force against surface tension.


As the electric field is increased, the hemisperical surface of the fluid at the tip of the caillary tube elongates to form an inverted cone known as the Taylor cone. On increasing the electric field further, at a critial value when the repulsive electrostatic forces overcome the surface tension forces a fine jet of charged polymer solution is ejected from the tip of the cone.


Once the jet comes into the atmosphere, the low boiling point solvent evaporates, leaving behind only the charged polymer strands. This jet is further subjected to elongation process and instabilities, which results in the jet becoming long and thin as they move towards the collector. The polymer strands moving away from each other due to mutual repulsion and ultimately collect on the counter electrode as a random coil of nanofibres. Fibres are obtained as aligned fibres if collected on a rotating drum collector. Different parameters like flow rate, viscosity, surface tension, electric field, rotation speed of collecting drum, etc. affect electrospinning process.





SEM pictures of Electrospun fibres (PMMA-MWCNT composite):


With rotation
Without rotation
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