The development of polymeric nanocomposites for various nanotechnology and biomedical science applications has recently gained interest for its potential use within prosthetics.
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This area of research would innovate the field due to the significant population number being affected.
Research illustrating the enhanced effect of utilizing carbon nanotubes has been incorporated within a novel study to reinforce the natural rubber nanocomposites for application within foot prosthetics. This article will provide an overview of natural rubber nanocomposites for prosthetics.
Natural Rubber Nanocomposites
Natural rubber (NR) is considered to be an important industrial crop and is contained predominantly in the milky sap or latex of a tree known as Hevea brasiliensis, as well as a small amount of nonrubber products including proteins, carbohydrates, lipids and inorganic salts.
The process of creating natural rubber consists of isolation through acid coagulation, which is then washed with water and subsequently processed into sheets. Vulcanization is then used to improve rubber elasticity and strength in the presence of sulfur and other compounding ingredients, which result in a three-dimensional network that natural rubber is inherently known for.
Nanocomposites comprise a multiphase solid material, with one of the phases having dimensions being within the nanoscale with less than 100 nanometers. The structures that make up the material can consist of nanoscale repeat distances between the different phases.
The fabrication of natural rubber nanocomposites includes the combination of natural rubber matrix and nanofillers that aim to improve the mechanical response of the material and electrical and thermal conductivities. Additionally, the reinforcement of fillers allows for significant improvements in strength and stiffness.
The Incorporation of Carbon Nanofillers
While other types of materials have also been researched for the reinforcement of natural rubber, including graphene oxide and zinc oxide nanoparticles, to enhance the interfacial interaction between the polymer matrix and the filler, carbon has also been shown to have great potential.
The use of carbon as a base for rubber nanocomposites enhances the hydrodynamic interactions between rubber and nanofiller surfaces. When investigating the properties of carbon-based rubber nanocomposites, previous studies have reported these to be strongly dependent on, (i) the uniformity and homogeneous dispersion of carbon nanofillers, (ii) the aspect ratio and nanofiller shape, and (iii) the interaction between the carbon nanofiller–rubber matrix as well as the between nanofillers.
The researchers of a novel study, published within Nature, have investigated the addition of carbon nanotubes (CNTs) to reinforce materials such as natural rubber. This inclusion was based on ubiquitous reports of CNTs and their low weight percent, which can enhance the mechanical characteristics of biodegradable polymer composites for applications, including biomedical engineering.
Existing literature has suggested CNTs reinforcing rubber systems demonstrated significantly high levels of filler interlocking and were able to trap rubber even at low loading.
Rubber nanocomposites have been widely used in various industries, from tires to technical parts and consumer goods. Its highly beneficial attribute of elasticity is an important component that enables this material to be highly desired for applications. However, as previously mentioned, it is often compounded with other materials, such as carbon nanotubes, graphene, graphene oxide and graphite nanoplatelets, to enhance its properties, increasing its versatility.
A novel and innovative use for rubber nanocomposites can be for advancement in the critical field of prosthetic implants; these artificial body parts are a great invention that supports the wearer after amputation.
The global prosthetics market size was valued at approximately 6.11 billion USD in 2020 and has been estimated to have an expected compound annual growth rate of 4.2% from 2021 to 2028; this may be the result of an increase in injuries relating to sports, road accidents, diabetes-related amputations, and even osteosarcoma.
There has been a rise in diabetes diagnoses as well as a rise in diabetes-related amputations, with recent investigations concerning diabetes mellitus foot gangrene in western Nigeria. This has uncovered a devastatingly significant rate of amputations of 52.2% as well as a 14.3% mortality rate within a group of diabetic patients with foot ulcers.
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Additionally, with reports from the Centres for Disease Control and Prevention (CDC) of approximately 1.9 million amputees within the US and 185,000 amputation surgeries annually, with 82% being a result of peripheral vascular disease and diabetes, the field of prosthetics and support for this population is critical.
Prosthetic Challenges and Potential Advancements
Prosthetics are significant aid for those who have had an amputated limb and require assistance with movement; however, there are challenges that conventional prosthetics face which reduce their efficacy.
Wearers of poorly fit prosthetics can have a difficult time with motion, and this can cause problems with gait habits and, in turn, long-term sub-optimal gait patterns, resulting in structural changes. Subsequently, it can cause muscular pain and even long-term neurological pain. Back pain can also be a common side effect due to losing a limb and the associated pressure.
The aim of utilizing CNTs to reinforce natural rubber matrix consists of the advancement in creating high-strength but low-weight materials for use as a prosthetic part which would restore the quality of motion and life of amputees that depend on having a foot aid.
This would also address low-income countries and areas, including sub-Saharan African countries like Nigeria, where the diabetic-related amputation statistics are devastatingly high.
Translation of Natural Rubber Carbon Nanotube Nanocomposites
The challenge of incorporating carbon nanotubes and testing of single-walled and multi-walled carbon nanotubes (MWCNTs) resulted in the conclusion that the combination of chemical purification of MWCNTs and mechanical mixing with the matrix phase, in the correct level, subsequently enhanced nanocomposite characteristics.
The optimal NR/MWCNT formulation increased capacity to handle tensile loading, with optimum dimensional stability at ambient conditions as well as being eco-friendly and having a water absorption of approximately 0.1%.
Compared to existing prosthetic foot material, this novel formulation had enhanced wear resistance and the highest capacity to dissipate energy through segmental motion.
While nanomaterials within the prosthesis sector may not be novel, this field is ever-evolving from being used in prosthodontics, such as for dental effects to prosthetic valves for heart disease and finally for enhancing prosthetic foot aids for amputees.
Future work for this research includes aesthetic acceptability via coloring agents, which researchers have hypothesized would not affect the inherent properties of the fillers of nanocomposites.
This effort may be difficult to translate and provide to low-income countries such as Nigeria, but with government-sponsored programs for prosthetics and global aid, universalization may be promising.
Continue reading: NovationSi's Carbon Nanotube-Based Rubber for Medical Applications.
References and Further Reading
Medupin, R., Abubakre, O., Abdulkareem, A., Muriana, R. and Abdulrahman, A., (2019) Carbon Nanotube Reinforced Natural Rubber Nanocomposite for Anthropomorphic Prosthetic Foot Purpose. Scientific Reports, 9(1). Available at: https://doi.org/10.1038/s41598-019-56778-0
Bokobza, L., (2018) Natural Rubber Nanocomposites: A Review. Nanomaterials, 9(1), p.12. Available at: https://doi.org/10.3390/nano9010012
Ghaleb, Z., Jaafar, M. and Rashid, A., (2019) Fabrication Methods of Carbon-Based Rubber Nanocomposites and Their Applications. Carbon-Based Nanofillers and Their Rubber Nanocomposites, pp.49-63. Available at: https://doi.org/10.1016/B978-0-12-817342-8.00003-2
Grandviewresearch.com. 2022. Prosthetics & Orthotics Market Size Report, 2021-2028. [online] Available at: https://www.grandviewresearch.com/industry-analysis/prosthetics-orthotics-market
Jose, J. and Athikalam Paulose, S., (2020) Studies on natural rubber nanocomposites by incorporating zinc oxide modified graphene oxide. Journal of Rubber Research, 23(4), pp.311-321. Available at: https://doi.org/10.1007/s42464-020-00059-3
Lai, J., Schoen, M., Gracia, A., Naidu, D. and Leung, S., *2007). Prosthetic devices: Challenges and implications of robotic implants and biological interfaces. Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 221(2), pp.173-183. Available at: https://doi.org/10.1243/09544119JEIM210
Paran, S., Karimi, M. and Saeb, M., (2019) Fabrication Methods of Carbon-Based Rubber Nanocomposites. Carbon-Based Nanofillers and Their Rubber Nanocomposites, pp.355-380. Available at: https://doi.org/10.1016/B978-0-12-813248-7.00012-2