Nanofabrics are textiles engineered with small particles that give ordinary materials advantageous properties such as superhydrophobicity (extreme water resistance, also see "Lotus effect"),
Nanoscale
A fiber that has a width of less than 1000
nanometers (1000 nm or 1 μm) is generally defined as a
nanofiber.
A
nanoparticle is defined as a small group of
atoms or
molecules with a
radius of less than 100
nanometers (100 nm).
Particles on the
Nanoscopic scale have a very high
surface area to
volume ratio, whereas this
ratio is much lower for objects on the
macroscopic scale. A high relative
surface area means that a large proportion of a particle's mass exists on its surface, so
nanofibers and
nanoparticles show a greater level of interaction with other materials. The high
surface area to
volume ratio observed in very small particles is what makes it possible to create many special properties exhibited by nanofabrics.
Manufacture
The use of
nanoparticles and
nanofibers to produce specialized nanofabrics became a subject of interest after the
sol-gel and
electrospinning techniques were fully developed in the 1980s.
Since 2000, dramatic increases in global funding have accelerated research efforts in
nanotechnology, including nanofabrics research.
Sol-gel
The
sol-gel process is used to create gel-like solutions which can be applied to textiles as a liquid finish to create nanofabrics with novel properties.
The process begins with dissolving
nanoparticles in a liquid
solvent (often an alcohol). Once dissolved, several chemical reactions take place that cause the
nanoparticles to grow and establish a network throughout the liquid.
The network transforms the solution into a
colloid (a suspension of solid particles in a liquid) with a gelatinous texture. Finally, the
colloid must go through a drying process to remove excess
solvent from the mixture before it can be used to treat fabrics.
The
sol-gel process is used in a similar fashion to make
polymer nanofibers, which are long, ultra-thin chains of
proteins bonded together.
Electrospinning
Electrospinning extracts
nanofibers from
polymer solutions (synthesized by the
sol-gel process) and collects them to form nonwoven nanofabrics.
A strong
electric field is applied to the solution to charge the
polymer strands. The solution is put into a syringe and aimed at an oppositely charged collector plate. When the
force of attraction between the
polymer nanofibers and the collector plate exceed the
surface tension of the solution, the
nanofibers are released from the solution and deposit onto the collector plate. The deposited fibers form a porous nanofabric that can aid in drug delivery and tissue engineering depending on the type of
polymer used.
Applications
Textile Manufacturing
When nanoengineered coatings are applied to fabrics, the
nanoparticles readily form
Chemical bond with the fibers of the material. The high
surface area relative to the
volume of particles increases their chemical reactivity, allowing them to stick to materials more permanently. Fabrics treated with
nanoparticle coatings during manufacturing produce materials that kill bacteria, eliminate moisture and odor, and prevent static electricity.
Polymer nanofiber coatings applied to textiles
Chemical bond to the material at one end of the
polymer, forming a surface of tiny, hair-like structures.
The
polymer "hairs" create a thin layer that prevents liquids from making contact with the actual fabric. Nanofabrics with dirt-proof, stain-proof, and
superhydrophobic properties are possible as a result of the layer formed by
polymer nanofibers.
Development of nanofabrics for use in the clothing and textiles industry is still in its early stages. Some applications such as bacteria-resistant clothing are not yet practical from an economic standpoint. For example, a Cornell University student's prototype for a bactericidal jacket cost $10,000 alone,
Drug Delivery
Nanofabrics used in
medicine can deliver
antibiotics, anticancer drugs,
proteins, and
DNA in precise quantities.
Electrospinning creates porous nanofabrics that can be loaded with the desired drug which are then applied to the tissue of the targeted area. The drug passes through the tissue by
diffusion, a process in which substances move through a
membrane from high to low
concentration. The rate at which the drug is administered can be changed by altering the composition of the nanofabric.
Tissue Engineering
Nonwoven fabrics made by
electrospinning have the potential to assist in the growth of organ tissue,
bone,
neurons,
tendons, and
ligaments.
Polymer nanofabrics can act either as a
scaffold to support damaged tissue or as a synthetic substitute for actual tissue. Depending on the function, the nanofabric can be made of natural or synthetic
polymers, or a combination of both.
Environmental Implications
As
nanotechnology advances, many studies have been conducted to determine the effects nanoengineered materials can have on the environment.
Most
textiles can lose up to 20% of their
mass during their lifetime, so
nanoparticles used in production of nanofabrics are at risk of being released into the air and waterways.
Nano-silver is expected to have as much as 49.5% of its global production taken by the nanotextiles industry due to its antibacterial properties. It is predicted that 20% of the nano-silver used in the nanofabrics industry will be released into waterways which could cause harm to microorganisms. However, more than 90% of nano-silver is removed during treatment at wastewater facilities, so it is likely that the environmental impact will be minimal.
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