In a typical electrospinning process, a voltage of several kilovolts
is applied between a metal capillary feeding a polymer solution
and a grounded collector holding the target substrate. The voltage
results in a strong electric field at the capillary tip which releases
the polymer solution in form of hanging droplets. When the voltage
applied is sufficiently high, the surface charges of the droplet will
eventually overcome the surface tension of the liquid. If the viscosity
of the solution is low, the droplet will explode into multiple
smaller droplets which are then accelerated toward the collector
(method of electrospraying). For high-viscosity liquids like polymer
solutions containing strongly entangled macromolecules, a
coherent jet is formed instead of multiple separate droplets. On
the way to the collector the jet is being extensively stretched by
the forces of the electric field, while at the same time the solvent is
largely evaporating. The continuous polymeric nanofibers formed
have diameters of typically well less than 1 m and deposit on
the substrate on the collector as a non-woven, textile-like coating,
macroscopically resembling a homogeneous compact polymer
film. These porous three-dimensional(3D) membranes excel with a
very large specific surface area, high porosity and good accessibility
for gaseous and liquid analytes. In consequence, electrospun nanomaterials
are highly attractive to multiple applications, including
filtration, sensing applications, drug delivery platforms and tissue
engineering.