What are Nanofibers?

Generally each fiber of less than 100 nm in diameter might be defined a ‘nano’fiber. Since a nanometer is given by one billionth of a meter, nanofibers are many orders of magnitude thinner than a human hair in their diameter. An usual range of fiber diameters which can be produced by our fabrication methods is between 50 nm up to 1 micron, depending on the specific material.

In addition, nanofibers can be produced with various structural shapes and morphologies (from a simple nonwoven web to more complex three-dimensional structures), using a variety of polymers and ceramics. Both synthetic polymers (polycarbonate, polysulfones, nylon) and biological polymers (chitosan, collagen, polylactic acid, polyglycolic compounds) can be used. It is also possible to obtain carbon nanofibers, using high temperatures and specific methodologies.


Why Nanofibers?

Comparing nanofibers to the conventional fibers allows clear advantageous characteristics to be highlighted. Due to their small size, nanofibers exhibit peculiar features such as a ultrahigh surface/volume ratio, meaning an extremely high surface area which is useful for a large variety of applications (catalysis, filtration, medicine, tissue engineering), as well as very high porosity.

In addition, nanofibers properties can be implemented and enhanced by adding specific molecules in the starting polymeric solutions. Dopants can include fluorophores, drugs, graphene, etc.. Each of these class of nanofibers is then usable in different application fields such as health, environment, energy, electronic, automotive, aerospace and many others.


How are Nanofibers produced?

Starting from a polymer solution with sufficient molecular entanglements, it is possible to produce continuous nanofibers using a versatile technique called Electrospinning. Through Electrospinning, polymer solutions or melts can be spun into nanometric fibers by using a high electric field.

The Electrospinning set-up includes pumps for controlled liquid delivery, needles biased at a high voltage (i.e., 5-30 kV) and suitable collecting elements for fiber deposition. Free-standing fiber mats as well as surface coatings can be produced in this way. The pump allows a steady flux of polymer solution to be achieved, that flows through needles. The fluid is deformed into droplets, forming Taylor cones and then jets by the applied voltage. The jet becomes a fiber through the solvent evaporation, occurring before it reaches the collector.




 What are Electrospinning advantages?

The key benefits are the simplicity and versatility of Electrospinning methods, allowing nanofibers to be specifically designed and realized according to custom requirements.

This technique allows us to obtain tens of different species of fibers through the control of the operating parameters (flow rate, voltage, nozzle, source-collector distance, temperature, humidity) and of the solution properties (type of molecule, solvent, concentration, conductivity).

The addition of various additives into the polymer solution leads to produce new nanofibrous materials with a huge variety of desired properties. These may include piezoelectricity, fluorescence, enhanced elasticity, controlled stiffness, enhanced or suppressed surface wetting, self-cleaning properties, catalytic activity, and so on.

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