Bigger Does Not Always Mean Better in the Military

Austin Taylor, Alex Dalrymple, Dahlia Björklund

Author Biographies

Austin Taylor: Austin is a rising senior from the Seattle, Washington area (Snohomish). Austin goes to public school where he runs for the Cross Country and Track teams. Aside from sports, Austin is the President of his school’s NHS, the Vice-President of the Science Club at his school, and a member of the City Youth Council. He likes just about everything in school (besides art) and plans to major in Chemistry in college, and go to medical school to become a surgeon.

Alex Dalrymple: Alex is a rising junior from New Bern, a small town in Eastern North Carolina. Alex attends a high school where she is a member of Science Olympiad, an officer for the Environmental Club, and a varsity volleyball player. In the summers, Alex enjoys participating in undergraduate research in an Inorganics Lab at a near university. Alex is very involved in her local hospital and is currently volunteering with the Oncology Department with hopes to pursue Oncology Research following college.

Dahlia Björklund: Dahlia is a rising senior from London, in the United Kingdom. Dahlia attends a secondary school where she is a member of Economics Society and is part of her school’s fundraising and linking program with the African Science Academy. She also enjoys writing and editing for her school’s magazine, and being head of marketing for the school charity shop. Outside of school Dahlia is very involved in the volunteering tutoring organization that she co-founded with her friends. She is passionate about all of her subjects and hopes to major in both Economics and Physics in college.

Introduction

In a world in which conflict is frequent and devastating, the further development of military clothing is essential to defend troops and limit the loss of life. One avenue to protect soldiers is to integrate nanobiomaterials into the fabric of military clothing to provide both increased strength and antibacterial attributes. Fabrics have been produced that have either great strength and protective qualities or antibacterial benefits, but creating materials that possess both of these qualities would be extremely beneficial for military applications [1].

Nanoparticles have already been implemented into the textile industry through the coating of textile fabrics such as cotton, polyester, and nylon with silver nanoparticle films [2]. Silver nanoparticles have been found to have excellent antibacterial qualities that inhibit the multiplication and growth of bacteria and fungi that cause infection and disease [3]. They have been utilized in fabrics for socks to prohibit the growth of bacteria and are also used in wound dressings for burns, cuts, and skin donor and recipient sites. Carbon nanofibers have also been a source of research in the textile industry [3]. Weaving carbon nanofibers into fabric can allow for increased strength of the fabric [4]. Instead of focusing on the use of nanobiomaterials for regenerative processes, this research focuses on the prevention of possible harm, whether that be from a bullet, an infection, or both. This article will explain the benefits and the defensive opportunities that could be created through a military suit that is able to reduce infection and provide ballistic protection as well as discuss the methods that are available to produce the fabric.

Target of Research

Based on research of the properties of nanomaterials and prior knowledge about them, this research is proposing a fabric that can be infused with nanomaterials to produce a protective armor for defensive purposes. The prospective armor will be made using a fabric that has nanomaterials integrated into its fibers to increase its ballistic protection against bullets. Carbon fibers can be integrated and could also be coated in silver nanoparticles. The purpose of using these nanobiomaterials is that silver nanoparticles contain antibacterial properties, allowing them to stop bacteria from getting in the suit and also help fight possible infection in the case of a bullet puncturing the suit. The goal is to use the findings of previous scientific articles and experiments to propose a body armor that is lightweight and breathable, both nanomaterials properties, that can also be worn under military clothing to increase protection from injury, infection, and disease.

Carbon Nanofiber Strength

When looking at possible materials for fiber integration, many different options were considered. After careful thought, the consensus was that using carbon nanofibers would be the ideal method. Carbon nanofibers have the ability to fortify materials and provide increased strength, even up to 100 times that of steel at one-sixth the weight [5]. The nanofibers are also 17 times stronger than Kevlar®,​ the material traditionally used to fabricate bullet-proof vests​[5]. Carbon nanofibers can be safely and effectively created through electrospinning, in which a carbon polymer solution is passed through a spinneret and is extruded using a high voltage shock to overcome the surface tension of the polymer solution. The result is a mass of long fibers created from a polymer solution, in this case carbon [6]. To maximize strength and produce straight fibers, the carbon nanofibers are pulled along a rotating spool and stretched [7]. The tensile strength of carbon nanotubes is around 80 GPa [6]. To put this into perspective, the pressure inside an average car tire is around 0.0002 GPa. The integration of nanofibers into clothing gives a breathable and lightweight quality, a very attractive feature for the more mobile fields of the military [8]. Carbon nanotubes can also be coated with particles to supply additional qualities such as antibacterial properties.

Use of Silver Nanoparticles to Give Fabrics Antibacterial Qualities

Silver nanoparticles have antibacterial qualities that can help prevent infection and accelerate wound healing, both of which could be of great use to military fabrics [9]. Silver nanoparticles in the size range of 1-100 nm are the most efficient as they have an increased surface area, allowing them to possess greater antibacterial properties [10]. They currently have existing uses as bactericide in sanitizing sprays, toothpastes, and many other antimicrobial consumer goods [11]. The complete details of how silver nanoparticles destroy bacteria are not yet known, but experiments have shown that silver ions arrest the metabolic activity of bacterial cells and inhibit several other cell functions that damage the bacterial cells [10]. Also, when bacterial cells come into contact with silver nanoparticles, nanoparticles accumulate and enter the cells where they generate reactive oxygen species. These reactive oxygen species are released and then attack the bacterial cell itself. Silver is also a soft acid which reacts with the nitrogenous bases to destroy the DNA of a cell, leading to cell death. Silver nanoparticles can adhere to bacterial cell walls and penetrate them, affecting the permeability of the cell membrane and also causing death of bacterial cells (Figure 1) [9]. Wound-healing with silver is attributed to increased death of neutrophils within wounds as well as reduced levels of anti-inflammatory agents. Reducing levels of anti-inflammatory agents within wounds helps accelerate wound healing. Fabrics loaded with silver nanoparticles also possess excellent antibacterial action against E. coli bacteria, as well as other multidrug resistant (MDR) bacteria [11,12].

Carbon nanofibers (CNFs) can be functionalized with silver nanoparticles to then be woven in with Kevlar fibers to make a stronger and more flexible fabric. To create these compounds, the silver ions are deoxidized and dispersed in a solution of ethanol. Silver particles are then formed under pressure in supercritical carbon dioxide (SC CO​) fluid which possesses unique properties such as low viscosity and minimal surface tension. This enables the SC CO​ to deliver the silver nanoparticles to the carbon nanofibers. Higher SC CO​ pressures mean that a larger number of small silver crystals can quickly be deposited onto the CNFs under magnetic stirring and homogeneously coat the fiber, thus avoiding aggregation of the silver nanoparticles. Transmission electron microscopy (TEM) is used to show the morphology of the silver nanoparticles wrapped around the carbon nanofibers (Figure 2) (Figure 3) [6]. This complicated process is only one of many different methods that could be used to functionalize carbon nanofibers with silver nanoparticles, but it is the most effective in this case, as being able to adjust the pressure of the SC CO​means that the nanoparticles can be homogeneously deposited over the material. This is important as the antibacterial qualities of the nanoparticles should be evenly distributed throughout the fabric so that the antibacterial protection is uniform throughout the material.

 

Conclusion

The end result of this research is to manufacture a strong and antibacterial fabric for military use through the creation of protective bodysuits. The proposed method involves carbon nanofibers that are woven into Kevlar​® Fabric to greatly increase the strength of the fabric as carbon nanotubes have 17 times the strength of Kevlar® alone (see Figure 4) [13]. The carbon nanotubes and Kevlar® fabric make this protective clothing more effective at preventing wounds inflicted from bullet as well as make it suited for ballistic conflict. However, the material is not suited for wounds inflicted by cutting the fabric. Therefore, any cuts in the fabric that penetrate the skin will allow the antibacterial qualities of the silver particles wrapped around the carbon nanofibers to be active. The silver nanoparticles will disinfect the wound by killing bacteria cells capable of causing infection, thereby improving defense capabilities on multiple fronts. With multiple applications and defensive capabilities, a protective military bodysuit made out of carbon nanofiber-infused Kevlar® offers a unique and effective means of enhancing survivability of military fabrics.

 

Possible Difficulties

It is important to conduct further research on the properties of silver nanoparticles as well as the mechanism behind the ability of silver nanoparticles to impart antibacterial properties. As stated previously, there are many ways in which scientists believe that silver nanoparticles actively kill bacteria, but it is important to thoroughly understand the mechanism behind the antibacterial quality of silver nanoparticles to explore the longevity of the nanoparticles on this fabric. The amount of nanoparticles on the suit may be reduced over time, leading to a need for bodysuit replacement, or possible re-application of nanoparticles. Further research would be needed to determine the lifespan of silver nanoparticles in the suit. Another issue presented is the heat sensitivity of Kevlar​®​fabrics. These fabrics will not work optimally when exposed to continuous heat. However, the carbon nanofibers that are woven into the Kevlar​®​material can possess thermal properties to prevent heat from affecting the material as severely. Another avenue for further exploration would be the benefits of using carbon nanofibers compared to carbon nanotubes. Research has indicated that both carbon nanofibers and nanotubes are effective for several properties of this military suit such as ballistic protection, additional strength, and the ability to be functionalized with silver nanoparticles. However, nanofibers were chosen in this case as they are very flexible, unlike nanotubes, and can easily be woven into a fabric. They are also easy to produce through electrospinning. Furthermore, as the carbon nanomaterials would be used for such specific purposes, we could test whether carbon nanofibers or carbon nanotubes are the most effective in terms of the specific qualities of this suit that are required such as ballistic protection, flexibility, thermal properties, and breathability.

 

Future Applications and Questions

When studying nanobiomaterials, it can be easy to get caught up in the hypothetical and stray away for what is currently possible. While these ideas are what further science in the present and the future, it remains important to focus on the things that are possible now when considering things like funding from a source like the Department of Defense. That being said, the process of turning an original idea like this into reality is dependent on asking the questions that stimulate achievable answers and solutions.

Without actually receiving funding and running experiments, it is hard to tell what the limitations of this design are. It is believed in this article that the suit would be fit around the whole body, but is that necessarily so? Furthermore, could the fabric even be created in a way that covers the whole body without limiting functionality and flexibility, not to mention all the things soldiers have to carry in the field? Additionally, what preliminary test would have to be run and what results would have to be acquired to garner support from the Department of Defense or other research-funding sources? All of these are questions that would have to be considered in great depth if this idea is ever to become reality, however, none of these questions touch on the principal problem when considering research ideas. This vital problem is simply the cost of producing such a material. While nanomaterial integration does not project as being extremely expensive, scaling up the design of the defensive suit could be costly.

Acknowledgements

As we come to the end of this article and course, we would like to thank our great peers, chill counselors Ana and Hailey, and wonderful professor Jagannath. Two weeks prior to finishing this article, Jagan made a promise to his class that we would walk away from this course with the knowledge and ability to learn any topic in just 14 days. At the time it seemed like quite the statement and possibly hyperbole; however, the style and approach Jagan took to teaching this class made all the difference. By asking the right questions and encouraging us to form original thought, Jagan was able to not only teach us about Nanobiomaterials but how to learn and really excel in anything we set our minds to. Thank you Jagan for creating an environment where learning was enjoyable once again.

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