Electropun Fibres

An innovative technology that allows the co-electrospinning of nanofibres with porous shells with core fluid that may find a wide variety of applications in fields varying from automotive hydrogen storage to pharmaceutical applications such as drug delivery. STFC currently licenses the technology in the field of hydrogen storage but invites interested partners from various other fields.

 

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DESCRIPTION

The electrospinning process is a very versatile process for the production of micron and nano-scale fibres. Such fibres are suited for applications such as scaffolds for clinical use, particulate filtration, etc. The need for more complex fibres such as those with different core and shell materials, multi-layered fibres, etc. have arisen as they may assist drug delivery, storage, etc. Such process as termed coaxial or co-electrospinning.

This innovative technology provides the method of electrospinning core-shell fibres wherein miscible or semi-miscible solutions for a porous shell while immiscible solutions form a non-porous shell. The latter is reasonably straight forward; hence this description focuses on the production of porous shell fibres.

The core liquid has a higher conductivity than the second shell liquid, preferably around 100 – 1000 times. The shell liquid should preferably have a viscosity greater than the core fluid in order to prevent electro-spraying as well as to allow sufficient instabilities in the core fluid for the purposes of pore generation. Lastly shell-core flow rates should preferably have a ratio of around 2:1.

The setup comprises usually of a nozzle which includes within it one or more ducts through which fluid flows to form a Taylor cone. An electric field is applied between the nozzle and a collector on to which the produced fibres fall. The setup may also be arranged to have multiple nozzles to allow for parallel production of fibres.

A radial electric field is generated when the two fluids issue out of the nozzle as a Taylor cone. The higher conductivity of the core fluid drives mixing of the two fluids in the radial electric field which in turn drives pore generation in the shell of the fibre. This pore generation on further scrutiny is seen to be the result of the electrostatic repulsion between charges built up at the core-shell interface, which causes them to overcome the surface tension and push out into the shell. The pore is thus created by the amplified capillary waves resulting in core-liquid rich regions protruding into the shell and then solidifying or evaporating to leave a pore in the shell. The pores so generated may have dimensions of around 0.1 – 0.05 µm to as low as 0.01 µm diameter, with a minimum achievable porosity of 5%.

The technology may be extended to fibre templating wherein the shell is removed by thermal degradation, sublimation, dissolving, UV or chemical etching. This results in a fibre having protrusions or branches.

 

INNOVATIONS

  • The ability to manufacture a fibre having a porous shell surrounding a core wherein the two fluids are miscible or semi miscible.

  • The pore generation is driven from the inside due to the higher conductivity of the core fluid.

 

ADVANTAGES

  • The process is independent of the surrounding moisture or humidity.

  • Control of the texture of the electrospun core-shell fibres

  • Parallel production easily achievable.

 

DOMAIN OF APPLICATION

  • Storage of hydrogen: By providing a hydride core fluid such as ammonia borane and a polymer shell fluid, hydrogen may be stored in the fibre. The shell would be permeable to hydrogen but not to borazine and borazine type compounds.

  • Pharmaceutical applications: A pharmaceutical drug may be used as the core fluid with a polymer shell. This can be extended to a wound dressing with a pharmaceutical drug release fibre.

  • By reducing the viscosity of the shell fluid, electrospraying of vesicles with porous shell is possible. Such products could find many applications in immobilised enzymes, stationary phase for HPLC and other chromatography systems, electroplating, etc.

Patent Information:
Country Serial No.
United Kingdom 1013315.5
South Korea 10-2013-7005800
Japan 522295/2013
European Patent Office 11748967.4
China 201180048136.4
United States 13/814709
For Information, Contact:
Elizabeth Bain
IP Manager
STFC Innovations
+44 (0) 1925 60 3680
elizabeth.bain@stfc.ac.uk
Keywords:
02.b. Industrial Manufacture
02.g. Materials Technology
03.d. Chemical Tech. & Engg.
04.a. Energy storage and transport
06.b. Biology/Biotechnology
06.d. Micro- & Nanotech. (bioscience)