The History of Electrospinning
In the late 1500s Sir. William Gilbert set out to describe the behaviour of magnetic and electrostatic phenomena. He observed that when a suitably electrically charged piece of amber was brought near a droplet of water it would form a cone shape and small droplets would be ejected from the tip of the cone: this is the first recorded observation of electrospraying.
The process of electrospinning was patented by J.F Cooley in February 1902 (U.S. Patent 692,631) and by W.J. Morton in July 1902 (U.S. Patent 705,691).
In 1914 John Zeleny, published work on the behaviour of fluid droplets at the end of metal capillaries. His effort began the attempt to mathematically model the behaviour of fluids under electrostatic forces.
Further developments toward commercialisation were made by Anton Formhals, and described in a sequence of patents from 1934 (U.S. Patent 1,975,504) to 1944 (U.S. Patent 2,349,950) for the fabrication of textile yarns. Electrospinning from a melt rather than a solution was patented by C.L Norton in 1936 (U.S. Patent 2,048,651) using an air-blast to assist fibre formation.
In 1938 N.D Rozenblum and I.V Petryanov-Sokolov, working in Prof. N.A. Fuks' group at the Aerosol Laboratory of the L.Ya Karpov Institute in the USSR, generated electrospun fibres , which they developed into filter materials known as "Petryanov filters". By 1939, this work had led to the establishment of a factory in Tver' for the manufacture of electrospun smoke filter elements for gas masks. The material, dubbed BF (Battlefield Filter) was spun from cellulose acetate in a solvent mixture of dichloroethane and ethanol. By the 1960s output of spun filtration material was claimed as 20 million m2 per annum.
Between 1964 and 1969 Sir Geoffrey Ingram Taylor produced the theoretical underpinning of electrospinning. Taylor’s work contributed to electrospinning by mathematically modelling the shape of the cone formed by the fluid droplet under the effect of an electric field; this characteristic droplet shape is now known as the Taylor cone. He further worked with J. R. Melcher to develop the “leaky dielectric model” for conducting fluids.
In the early 1990s several research groups (notably that of Reneker who popularised the name electrospinning for the process) demonstrated that many organic polymers could be electrospun into nanofibers. Since then, the number of publications about electrospinning has been increasing exponentially every year.
Since 1995 there have been further theoretical developments of the driving mechanisms of the electrospinning process. Reznik et al. (2004) describes extensive work on the shape of the Taylor cone and the subsequent ejection of a fluid jet. The work by Hohman et al. (2001) investigates the relative growth rates of the numerous proposed instabilities in an electrically forced jet once in flight. Also important has been work by Yarin et al. (2001) endeavouring to describe the most important instability to the electrospinning process, the bending (whipping) instability.
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