When one is considering utilising nanomaterials in textiles much depends on what functionality is desired and the compatibility of the nanomaterial with the fibre material. The level of functionality is determined both by the specific properties of the material and also how it is incorporated with the fibre. The compatibility is determined in a large part by the surface chemistry of the particles and the production process used to make the nanomaterial.

Manufacturing nanoparticles can be achieved through a wide variety of different routes, some of which have been around for many years, others which are far more recent. In essence there are four generic routes to make your nanoparticles; wet chemical, mechanical, form-in-place and gas phase synthesis. The resultant materials can have significantly different properties depending on the route chosen to fabricate them and some routes are more aligned with the fabrication of certain classes of materials.

Wet chemical processes – these include colloidal chemistry, hydrothermal methods, sol-gels, and other precipitation processes. Essentially solutions of different ions are mixed in well defined quantities and under controlled conditions of heat, temperature and pressure to promote the formation of insoluble compounds which precipitate out of solution. It is possible to control particle size closely and to produce highly monodisperse materials. However, bound water molecules can be a problem when combining with hydrophobic materials and for sol-gel processing especially the yields can be quite low.

Mechanical processes – these include grinding, milling and mechanical alloying techniques. Today the most common processes are either planetary mills or rotating ball mills. These are relatively cheap processes but there can be difficulties such as agglomeration of the powders, broad particle size distributions, contamination from the process equipment itself and it is very difficult to get to the very fine particle sizes. Commonly it is used for inorganics and metals but not organic materials.

Form-in-place processes – these include lithography, vacuum deposition (PVD and CVD) and spray coatings. These processes are more geared to the production of nanostructured layers and coatings, and are not generally used for the fabrication of dry powders although some companies are beginning to exploit these processes.

Gas Phase Synthesis – these include flame pyrolysis, electroexplosion, laser ablation, high temperature evaporation and plasma synthesis techniques. All these techniques rely on heating the feedstock material to above the boiling point to create a vapour and then rapidly quenching it to generate the nanoparticles. They are very suited to volume production and the production of a wide range of functional materials. This means that even highly refractory materials can be processed, however, these processes are not suitable for producing organic materials.

From these production methods materials can be made that provide a range of properties including conductivity, magnetism, piezoelectric effects, colour, water repellency and anti-microbial activity. The incorporation with fibres to produce the functional fibres and hence textiles is often a closely guarded secret. However, processes have been developed to control the surface chemistry to enable the nanomaterials to be either incorporated either into the bulk or onto the surface of the fibre during fibre manufacture, or to coat the surface of existing fibres. Depending on the functionality desired different routes are preferable.

Current and potential applications for fibres and textiles incorporating nanomaterials include stain resistant clothing, anti-odour for sportswear, anti-microbial medical textiles, conducting cloth, water repellent fabrics and textiles that can sense movement and wear, they may also be used to generate power to charge mobile devices. It is also entirely feasible to combine different functionalities in the same fibres, although this needs considerable further development. Many of these concepts are yet to be brought to market and more and more uses for these materials are being identified.

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