Conductive fibres production methods

A final method is metallisation11 of fibres, which is most related to the technology described in this chapter. In this method, metal salts are taken up by the fibre and reduced to their metallic conductive form. Metallisation can be achieved in different ways. A first way is by a vacuum metal spray. However, this results in very poor defined metallisation. In addition, galvanic coating is used in the production of conductive fibres, but this type of coating requires a fibre that is already conductive. 

Modem approaches to the production of electrically conducting threads include conductive substrates, metal wires, metallized yams and inherently conductive polymers. It is notable that some of the approaches hark back to the methods used in ancient times. For example, a patent from 2005 describes how an electrically conductive fibre can be wound around an elastic core to produce a yam that can be elongated considerably (Nusco et al., 2005). Cottet et al. (2003) also report the use of copper threads following a helical path. 

Many other opportunities exist due to the enormous flexibility of the preparative method, and the ability to incorporate many different species. Very recently, a great deal of work has been published concerning methods of producing these materials with specific physical forms, such as spheres, discs and fibres. Such possibilities will pave the way to new application areas such as molecular wires, where the silica fibre acts as an insulator, and the inside of the pore is filled with a metal or indeed a conducting polymer, such that nanoscale wires and electronic devices can be fabricated. Initial work on the production of highly porous electrodes has already been successfully carried out, and the extension to uni-directional bundles of wires will no doubt soon follow. 

The sol-gel process for the production of silica is an industrially widely apphed procedure. The process is usually conducted in homogeneous solution, and it is possible to manufacture nano- or micro-sized particles, clear macroscopic silica objects (monoliths), such as fibres or lenses [17]. Sol-gel processing is commonly conducted at quiescent temperature, and no increased pressure is necessary, which makes this method suitable for LLC templating. The starting material for the sol-gel preparation of silica is an orthoester (alkoxide) of the general structure Si(OR)4, which is hydrolysed in order to formally yield silicic acid. The latter undergoes polycondensation into a three-dimensional network of silicon... 

---