Nanofibers with self-healing properties are emerging as breakthrough materials for new breakthroughs at the cutting edge of nanotechnology. This article discusses self-healing nanofibers, their background, their applications in various industrial sectors and relevant recent studies.
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Background
Materials scientists have worked to improve several attributes of materials over the decades. Constant research and development has produced materials with improved performance. However, materials still degrade over time and experience operational fatigue, leading to nanocracks and ultimately failure.
Most composites are vulnerable to microcracks which are very difficult to detect or repair, resulting in reduced reliability and shorter life of these materials. The solution to such a problem lies in self-healing nanofibers.
What are self-healing nanofibers?
Self-healing is a relatively new prospect for advanced and reactive materials. Nanomaterials that can heal themselves, such as mimicking the healing of biological organisms, are known as self-healing nanomaterials.
The nanofibers of these materials automatically and instantly repair the damaged area. These materials are used in various applications in scientific fields, including engineering, military, energy harvesting, dentistry, orthopedics, communication, construction, aerospace and automotive.
How are self-healing nanofibers made?
Electrospinning is a unique process used to make nanofibers using an electrostatic field. It is based on the principle of electrohydrodynamics.
In this process, nanofibers are produced by the acceleration of liquid jets with self-healing properties which are subjected to the coupled effects of an electric field on viscous liquids such as melts, dispersions and solutions. . These jets of liquid go through processes of elongation, evaporation and solidification, after which the nanofibers can be collected.
Compared to other nanofiber processing approaches, this technology is not only user-friendly but also relatively economical, thanks to its adaptability in fabricating continuous nanofibers from a wide range of polymers. There are several advantages associated with fabricating nanofibers using this technique, including mass production proficiency, ease of material combination, fiber functionalization, and fine-tuning fiber properties.
Electrospinning methods have undergone significant development over the past two decades, allowing better morphological control of deposited nanofibers and improving fiber production and variety. Over the past two decades, several different electrospinning derivative designs have been developed and patented, including electroblasting, multi-jet electrospinning, near-field electrospinning, fusion electrospinning, bubble electrospinning, coaxial electrospinning and needleless electrospinning.
Recent studies
In a recent study conducted in 2021, scientists were able to design a new composite hydrogel composed of polyaniline (PANI), polyacrylic acid (PAA), and 2,2,6,6-tetramethylpiperidin-1-yl)oxyl (TEMPO )-oxidized cellulose nanofibrils (TOCNF). These scientists studied various properties of this new composite, including sensing, self-healing, conductive and mechanical properties. This hydrogel had an electrical conductivity of 3.95 S m-1a tensile strength of 74.98 and a strain at break of 982%, as well as excellent self-healing properties without applying stimuli.
What are the applications of self-healing nanofibers in various industrial sectors
Self-healing nanofibers have various potential applications in several industrial sectors, including space, electronics, defense, textiles (protective clothing) and biomedical.
Spatial application:
Space is a very hostile place for structural materials due to its environmental conditions. Material damage can be caused by chemical, mechanical, thermal and UV radiation or combinations of these components. In addition, space debris in lower obits is also dangerous to satellites and spacecraft and can damage them. It is therefore imperative to develop self-healing systems that minimize damage before it leads to disastrous breakdowns.
NASA scientists have developed a self-healing material system that can minimize hypervelocity or ballistic impacts like micrometeoroids. This nanomaterial has the ability to self-repair in microseconds over a long temperature range. This system has other uses like MMOD armor liners for aircraft, pneumatic armor, radiation shielding, and fuel tanks.
Electronic application:
Several self-healing nanopolymers have been used to make electronics, such as supercapacitors, smart wearables, batteries, and artificial muscles. New artificial skin-like electronics can sense humidity, temperature and pressure. This self-healing artificial skin is expected to be widely used in wearable devices and soft robotics, greatly reducing costs since these electronic devices can heal themselves.
Request for defense:
Fiber-reinforced self-healing nanopolymers have various applications in the defense sector, including ground vehicles, tactical structures, aviation (helicopters and drones) and armor (vehicles and personal equipment). Repairability and maintainability are of crucial importance in the defense industry. Due to their anti-ballistic, self-healing, and lightweight properties, self-healing nanocomposites are ideal for defense applications such as protecting the fuel tank body from hypervelocity and ballistic damage.
Nanotechnology has made smart uniforms for soldiers possible. These self-healing suits are made by a combination of nanostructures with micro and macro fibers, providing a shield against chemicals, harmful biological agents, grenade fragments and bullets.
Biomedical application:
Recently, in the biomedical sector, self-healing hydrogels have been applied in drug delivery, cell culture and tissue engineering. Self-healing biological hydrogels are used in the treatment of brain injuries due to their adoptive physical, chemical and biological attributes.
For example, type I collagen-based biohydrogels are known for their self-healing abilities, injectability, non-cytotoxicity, and biocompatibility, making them ideal for nerve tissue repair. Moreover, these self-healing biohydrogel scaffolds are of great importance in neuro-regeneration.
Continue reading: Agricultural applications of nanofibers.
References and further reading
Chaudhary, K., & Kandasubramanian, B. (2022). Self-healing nanofibers for engineering applications. Research in industrial and technical chemistry, 61(11), 3789-3816. https://doi.org/10.1021/acs.iecr.1c04602
Jiao, Y., Lu, Y., Lu, K., Yue, Y., Xu, X., Xiao, H., … & Han, J. (2021). Conductive hydrogel mediated by highly stretchable and self-healing cellulose nanofibers for strain sensing application. Journal of Colloid and Interface Science, 597, 171-181. https://doi.org/10.1016/j.jcis.2021.04.001
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