A nanofiber is a fiber with a diameter of 100 nanometers or less. The nanofibers due to some special properties are being investigated for a myriad of potential applications in the fields of medicine, electronics and other material sciences. Such fibers have a high ratio of surface area to volume. This makes them particularly useful for solar cells, which try to maximize exposure to sunlight. In addition, nanofibers yield materials that are permeable at the small scale, which makes them suited for use as water filters. The fibers, when bound, are also relatively strong.
Some of the most promising applications of this material include capturing individual cancer cells in the blood stream stimulating cartilage production in damaged tissues, delivering therapeutic drugs to diseased cells, developing silicon nanowire and germanium nanowire anodes for battery electrodes allowing for fast charging and current delivery, chemical and biological defence through sensors that can change color when exposed to certain chemical vapors. Earlier research has also showed that coating furniture with carbon nanofibers could serve as a flame retardant.
Reseachers are using nanofibers to delivery thrapeutic drugs. The have developed an elastic material that is embedded with needle like carbon nanofibers. The material is intended to be used as balloons which are inserted next diseased tissue, and then inflated. When the balloon is inflated the carbon nanofibers penetrate diseased cells and delivery therapeutic drugs.
Nano fiber feels forces and hears sounds made by cells
Engineers at the University of California San Diego have developed a miniature device that’s sensitive enough to feel the forces generated by swimming bacteria and hear the beating of heart muscle cells.
The device is a nano-sized optical fiber that’s about 100 times thinner than a human hair. It can detect forces down to 160 femtonewtons — about ten trillion times smaller than a newton — when placed in a solution containing live Helicobacter pylori bacteria, which are swimming bacteria found in the gut. In cultures of beating heart muscle cells from mice, the nano fiber can detect sounds down to -30 decibels — a level that’s one thousand times below the limit of the human ear.
“This work could open up new doors to track small interactions and changes that couldn’t be tracked before,” said nanoengineering professor Donald Sirbuly at the UC San Diego Jacobs School of Engineering, who led the study.
Next generation batteries
Researchers at MIT have used carbon nanofibers to make lithium ion battery electrodes that show four times the storage capacity of current lithium ion batteries. Researchers have turned to using silicon nanowire and germanium nanowire anodes due to their advantages like efficient electron transport and larger surface area that further increases the battery’s power density, allowing for fast charging and current delivery.
A standard lithium-ion battery used in most smartphones is expected to have between 300 to 500 charge cycles in it before it starts to lose a sizeable chunk of capacity. The system designed by doctoral candidate Mya Le Thai can be cycled hundreds of thousands of times without wearing out, which could lead to a battery that never needs to be replaced.
Researchers replaced traditional lithium by gold nanowires which are thousands of times thinner than a human hair, have extremely high conductivity and surface area, making them ideal for the transfer and storage of electrons.
Chemical and biological warfare defence
Researchers are using nanofibers to make sensors that change color as they absorb chemical vapors. They plan to use these sensors to show when the absorbing material in a gas mask becomes saturated.
Chemical, Biological Weapons Resistant Membrane Developed In Russia
Russia’s Saratov State University chemists have developed an air and vapor permeable membrane solution that can defend military personnel from chemical and biological weapons.
The project was ordered by the Fund for Perspective Research. “In cooperation with industrial partners, experimental suits have been made for Defense Ministry and Interior Ministry personnel to wear during a test period.” The university’s president, Leonid Kossovich, was quoted as saying by TASS Friday.
The membrane fabrics are impermeable to water, viruses, bacteria, toxins and allergens. The wearer of the suit is safe from the hazardous effects of chemical and biological agents. Meanwhile, the nanofiber fabric is microporous allowing air and vapor circulation. The technical fabrics were created within the framework of a larger project of the Fund for Perspective Research for creating combat gear of the future. The research began in 2014.
“At the request of a partner in Moscow we are about to start manufacturing a large consignment of the membrane fabric, about seven kilometers in total length,” Kossovich said
Nanowire Fabrics for Military wearables
Researchers from Stanford University in California have developed a cotton fabric embedded with a network of very fine silver nanowires that could heat up when electric power is supplied to the wires. The fabric made of nanofibers and hydrogels developed by Phil Gibson and Calvin Lee have the potential to keep soldiers warm and comfortable when they are working in colder climates.
Taken together, the combination of different composite materials, along with the nanofibers, seem to be the best approach to develop clothing that could provide maximum insulation. By applying as little as 3 volts (V) of energy, which is the typical output of a watch battery, this group of Researchers successfully increased the temperature of a one square inch by 40 ºC.
The hydrogel particles made of polyethylene glycol incorporated in the clothing can absorb sweat thereby preventing the inner layers from becoming wet. Along with cold weather clothing, this fiber based insulation technology could be applied to various other gear for soldiers such as hand wear, sleeping bags, tent liners as well as in other applications related to refrigerators and storage units used for various purposes like food services.
Soldiers will be able to increase or decrease the voltage to keep them warm and comfortable while also having increased mobility due to the lighter and thinner uniforms.
Researchers have developed piezoelectric nanofibers that are flexible enough to be woven into clothing. The fibers can turn normal motion into electricity to power your cell phone and other mobile electronic devices. Flame retardant formed by coating the foam used in furniture with carbon nanofibers.
Several methods have been developed to fabricate nanofibers, such as template, self-assembly, phase separation, melt-blown and electrospinning. Electrospinning is currently the most promising technique to produce continuous nanofibers on a large scale and the fiber diameter can be adjusted from nanometers to microns. Also, electrospinning is a relatively easy and fast process to produce nanofibers.
Advances in the 3D printing of nanofibers
Nanofiber meshes can be used for many applications, including solar cells, body armor, and as part of systems for water filtration. While the potential is apparent in theory, in practice the use of nanofibers on a commercial scale has been hampered by generating sufficiently large volumes of the material of sufficient quality.
Materials scientists based at the Massachusetts Institute of Technology new approach for the 3D printing of nanofiber meshes. nanofibers being produced on a large scale and of good quality, with little variation with the diameters of the fibers produced. Diameter control is important since the performance of the fibers dependent upon their diameter.
The technology behind this has shifted from the manufacturing of fibers where silicon is etched to 3D printing. The process works by fashioning a printer made up of an array of small nozzles. Through the nozzles a special fluid, containing particles of a polymer, are pushed through. An electric field is sued to draw the fluid out into the form of the tiny fibers.
The nozzles of the 3D printer are arranged into two rows. These channels are marginally offset from each other. The offsetting is to produce fibers with a required alignment and so that the nanofibers maintain their relative position once they are collected by a rotating drum. To achieve the arrangement, the research group tested out 70 iterations of the alignment in order to optimize the production process.