The electrospinning process is mainly driven by electrostatic forces acting on the surface of a liquid polymer solution or a polymer melt, and this interaction results in the production of fibres. In conventional spinning, the fibre is also subject to:
- tensile forces;
- viscous forces;
- inertial forces;
- aerodynamic forces.
When free charges in the liquid polymer (usually positive ions) move in response to the electric field, they rapidly transfer a force to the polymer liquid. A strong electric field is then applied to the solution, which generates an electrostatic force greater than the above forces, and the result is the formation of a jet that moves towards the opposite electrode.
A stable jet has four regions:
- the base region: the get emerges from the liquid polymer;
- the jet region: zone through which the jet passes;
- broadening region: area in which the jet splits into many fibres;
- collection region: the last region in which the jet is accumulated.
In the last region, the formed fibres are collected on a collector that can have the geometric shapes of:
- a static plane: with the function of collecting a matrix of disordered fibres;
- a cylindrical geometry: to obtain a more ordered collection depending also on the rotation speed (rpm).
It is possible to directly deposit the electrospun nanofibres on objects of different shapes to obtain three-dimensional nanofibre substrates of controlled shape and size. Various types of electrospun fibre scaffolds aligned or randomly oriented can also be manually processed to obtain the desired geometry.
During the process, the material solution is extruded from the spinneret forming a small droplet; high voltage is required to transfer charge with a certain polarity to the surface of the droplet. When the electric field exceeds a critical value, the repulsive electric forces overcome the surface tension forces and the material is accelerated towards the collector (which has opposite polarity) in the form of a fibre.
In this video uploaded by CanalDivulgación we can see the electtrospinning mechanism.