Electrospinning nanofibres
Electrospinning is an extensively studied and widely applied method for nanofibre production. It produces long, continuous fibres with diameters ranging from a few nanometres up to several micrometres. Electrospinning has enjoyed significant attention recently because of its ease of lab-scale set-up and its versatility in producing nanofibres from a wide range of materials.
Electrospinning lab set-up
Electrospinning makes use of electrostatic forces to draw a very fine fibre from the liquid droplet at the end of a fine needle and deposit it on a collector plate. The set-up on a small scale is relatively simple.
Nanofibres are nanoscale materials
Nanofibres are an exciting class of nanoscale materials. Individually, nanofibres are so small they’re hard to imagine, but when collected together, they form a tangible nanomaterial. These new nanomaterials are being used in many high-tech industries.
A rediscovered technology
The first patents for electrospinning were issued over a hundred years ago in the USA to JF Cooley (in 1900) and WJ Morton (in 1902). There was, however, little application for the technology at this time. From 1934 to 1944, a series of patents were awarded to Anton Formhals (USA) for a process for producing fine fibres from a cellulose acetate solution. Around the same time in Russia, ND Rozehblum and IV Petryanov-Sokolov were producing electrospun fibres from a cellulose acetate solution to use as smoke filter elements for gas masks. This is the first documented application for electrospun fibres.
Not much else happened in the electrospinning field until the early 1990s. At this time, due to the rapidly growing interest in nanoscience and nanomaterials, the process of electrospinning for producing nanofibres was rediscovered. Several research groups demonstrated that many organic polymers can be electrospun into continuous nanofibres and collected to form a non-woven fabric. It was at this time that the term ‘electrospinning’ became popular.
Set-up
Electrospinning is relatively straightforward to set up at lab scale. It makes use of electrostatic forces to draw very fine fibres from the liquid droplet at the end of a fine needle and deposit it on a collector plate.
The electrospinning process
Simon Feasey and Iain Hosie, Revolution Fibres, explain the process of electrospinning nanofibres.
Jargon alert
Taylor cone: the characteristic droplet shape formed by fluid on the tip of the needle when under the effect of an electric field as in the process of electrospinning.
Electrostatic field: when two objects in each other’s vicinity have different electrical charges, an electrostatic field exists between them.
Collector/collector plate: the surface onto which the electrospun nanofibre is deposited. In this video clip, two collectors are illustrated. The first is a metal disc holding a filter. The disc spins around during the electrospinning process and the nanofibre is deposited over the surface of the filter. In the second example, nanofibres are deposited onto a removable sheet, a roll of material that runs through the Komodo.
UPDATE: In May 2021, Revolution Fibres rebranded to NanoLayr.
The electrospinning process
Simon Feasey and Iain Hosie, Revolution Fibres, explain the process of electrospinning nanofibres.
Jargon alert
Taylor cone: the characteristic droplet shape formed by fluid on the tip of the needle when under the effect of an electric field as in the process of electrospinning.
Electrostatic field: when two objects in each other’s vicinity have different electrical charges, an electrostatic field exists between them.
Collector/collector plate: the surface onto which the electrospun nanofibre is deposited. In this video clip, two collectors are illustrated. The first is a metal disc holding a filter. The disc spins around during the electrospinning process and the nanofibre is deposited over the surface of the filter. In the second example, nanofibres are deposited onto a removable sheet, a roll of material that runs through the Komodo.
UPDATE: In May 2021, Revolution Fibres rebranded to NanoLayr.
Electrospinning is used to produce nanofibres from a wide range of materials. By controlling different factors in the process, the properties of the resulting fibre can be adjusted so that they match the desired end application (for example, an acoustic fabric that targets certain frequencies). This ability to manipulate factors contributing to fibre creation gives a lot of flexibility in experimental design and end-product characteristics. This flexibility contributes to the growing popularity of electrospinning.
Scaling up
At lab scale, the electrospinning process produces small amounts of material. For many applications and research projects, this is enough. However, for researchers who require greater quantities of material or for those who want to commercialise their work, larger production capacity is required. This means taking what works successfully on a small lab-scale set-up and scaling it up on larger equipment to produce larger quantities of material.
There can be challenges taking a successful lab-scale process and scaling it up. Often, processes need to be modified at a larger scale to produce consistent, high-quality materials economically. Currently, there is lots of interest in scaling up electrospinning to industrial capacity so that the applications being discovered in the lab can be successfully commercialised.
Revolution Fibres scaling up
For Revolution Fibres, scaling up their electrospinning technology involved designing and making their own machines. They started by designing a prototype lab scale machine called the Skink. They used this to test, refine and prove feasibility of their electrospinning process. Scaling up then involved two stages: a pilot machine, the Chameleon, to refine processes and prove viability before further investment to develop a commercial machine, the Komodo. The Komodo began commercial production runs in April 2012.
Commercial production on the Komodo
Revolution Fibres designed and made electrospinning machines that successfully scaled up their production. Commercial production runs began on the Komodo in April 2012.
Future
Nanofibres offer immense opportunities for creating products with new or enhanced properties. One of the main limitations for the wider application of nanofibres, however, is scaling up from producing small lab-scale quantities to producing industrial quantities. Of the various processes currently available to produce nanofibres, electrospinning is considered to be the most promising method to meet the requirement for commercial quantities of high-quality nanofibres at affordable prices.
Useful links
For more information on the electrospinning process, this paper is from one of the research groups in the mid-1990s that demonstrated electrospinning of polymer nanofibres and gives clear descriptions and explanations. Doshi, J. and Reneker, D.H. Electrospinning process and applications of electrospun fibres. Journal of Electrostatics. 1995, 35, 151–160. Note that only a summary is freely available.
In May 2021, Revolution Fibres rebranded as NanoLayr.
