[Popular science knowledge] Application of carbon fiber composites in the field of medical devices

Nov 18, 2022

Carbon fiber composites are more and more widely used in the fields of diagnosis and treatment, health care and related medical devices. With the gradual increase of medical market demand, the relevant carbon fiber medical materials are also expanding and innovating in application ways and forms.
The research of medical carbon fiber materials began in the 1960s, when it was found that carbon fiber materials had excellent anti coagulation properties in the research of anti coagulation materials for artificial blood vessels. After 1970, Bokros proposed to use carbon fiber materials as biomedical devices. According to modern scientific research, carbon fiber materials have good biocompatibility, low irritation to biological tissues, non-toxic, non carcinogenic, small specific gravity, similar elastic modulus to human bone and other advantages, and have potential advantages as the fourth generation implant materials.
Application advantages of carbon fiber composites in medical field
1. Anisotropy and designability
Carbon fiber composite is an anisotropic material. Its properties along the fiber direction and perpendicular to the fiber direction are different, which brings great freedom to the design. The elasticity and strength of the product can be changed by changing the laying mode (such as the laying angle and the laying sequence) to meet the specific use requirements. Medical equipment components often act on different parts of the human body, and the specific performance requirements of different components are different.
2. High X-ray transmittance
The transmissivity of X-ray is related to the element composition, atomic number, density and thickness of the penetrated material. The main elements of carbon fiber composites are C, H and O, with small atomic numbers. The mass absorption coefficient of X-ray is far lower than that of ordinary materials. The X-ray transmittance of 1mm thick aluminum plate and carbon fiber composite plate is 78% and 96% respectively, the scattering and absorption consumption of aluminum plate is 22%, and that of carbon fiber composite plate is only 4%.
3. Good fatigue resistance
Carbon fiber composites contain numerous fiber/resin interfaces. When cracks are generated by excessive external forces, these interfaces can effectively prevent the further expansion of cracks and delay the generation of fatigue damage. Medical devices are reused every day, and the good fatigue resistance of carbon fiber composite material ensures the service life of the instrument.
In the field of medical devices, carbon fiber composite materials are used to manufacture mobile platforms for X-ray detectors by virtue of their full X-ray transmission; With its excellent mechanical properties, CFRP is used to manufacture medical devices for orthopedics and organ transplantation, as well as rehabilitation products such as artificial limbs and orthotics.
Used for CT bed plate, X-ray examination and other equipment and auxiliary equipment
These are the most widely used carbon fiber medical cases in China at present. The representative ones are X-ray, CT and B-ultrasound table panels, head rest for diagnostic tables, high-definition DR plate detector panels, and stents.
The medical CT bed plate mostly adopts insulated electric plate, but its ray transmissivity is low, its mechanical property is poor, and its imaging definition is poor. The absorptivity and scattering rate of carbon fiber composites are much smaller than those of carbon fiber composites, which can correspondingly reduce the X-ray dose, reduce the power of the X-ray machine, prolong the service life of the instrument and save electric energy during diagnosis.
More importantly, the carbon fiber composite material, because of its excellent X-ray transmission performance, allows the ray to shine on the bed plate at any angle without refraction. Only a small dose of ray can obtain clear radiography, thus reducing the harm to patients and medical staff.
Previously, at the Japanese Medical Device Design and Manufacturing Exhibition, Teijin Group displayed its carbon fiber composite application products in the medical field - carbon fiber stents for brain surgery.
Carbon fiber for artificial bone and artificial joint
At present, carbon fiber composites have been widely used in bone internal fixation plate, bone filler, hip joint handle, artificial implant tooth root, skull repair materials and artificial heart materials. The bending strength of human skeleton is about 100Mpa, the bending modulus is 7~20Gpa, the tensile strength is about 150Mpa, and the tensile modulus is about 20Gpa. The bending strength of carbon fiber composites is about 89Mpa, the bending modulus is 27Gpa, the tensile strength is about 43Mpa, and the tensile modulus is about 24Gpa, which is close to or beyond the strength of human bones.
At present, some companies have developed the use of carbon fiber composites to make artificial bones and joints. The bending strength of this artificial bone is closer to the real human bone than that of other biological materials, which is of great significance to orthopedic medicine. The wear resistance of the artificial joint made of it is also higher than that of ultra-high molecular weight polyethylene and metal products.
Invibo is a well-known supplier of medical devices. The short carbon fiber reinforced polyether ether ketone (PEEK) developed by Invibo has excellent mechanical strength and tensile creep, can bear the load required by bone, blood and human tissue, and has good compatibility with human body. The bending strength of this artificial bone is closer to the real human bone than that of artificial bone made of other biological materials, which is of great significance to orthopedics. The wear resistance of the artificial joint made of it is also higher than that of ultra-high molecular weight polyethylene and metal products.
Another company has developed continuous carbon fiber or felt reinforced plastic for bone repair. The resin matrix is polymethyl methacrylate, and the mass fraction of carbon fiber is 20% - 60%. Because of its light weight, no interference to MRI, and good biocompatibility, it has no adverse reaction or rejection reaction to biological tissue, blood, cerebrospinal fluid, etc. after long-term implantation into the organism, so it is suitable for fracture fixation or fracture fixation or bone repair materials.
Dental restoration
In Europe and the United States, non-metallic restorative prefabricated fiber post systems are increasingly used in clinical practice, and are gradually considered to be effective substitutes for traditional metal post core systems to repair residual roots and crowns of teeth. The research on the physical, chemical and biological properties of carbon fiber post shows that the carbon fiber post has more mechanical properties matching with the tooth tissue, and its elastic modulus, which is similar to the dentin, can make the stress more evenly distributed along the post, which is conducive to the protection of the root; At the same time, it has many advantages, such as good biocompatibility and corrosion resistance, easy removal, and convenient secondary repair.
Carbon fiber prosthesis
The connecting part between the artificial limb and the human body is called the receiving cavity, which mainly covers the residual limb and transmits power. This part has high load bearing requirements and cannot be too heavy. Carbon fiber materials can also be used to make this part. The part containing the residual limb can be made of polyethylene sheet, and the support body can be made of carbon fiber frame structure to achieve easy support and transmission of strength.
The linkage of the human ankle and foot plays a key role in the balance and support of the body. The ankle joint made of carbon fiber can realize the jumping function of the human body. In addition, the joint between the ankle and the lower leg prosthesis can also be made of carbon fiber. The product is very beautiful as a whole and performs well in terms of damage safety.
Carbon fiber wheelchair
The density of carbon fiber is only 1.7g/cm3, and the accessories of the same specification are more than half lighter than those made of aluminum alloy, but the strength is much higher. In addition, carbon fiber also has strong corrosion resistance. A considerable proportion of wheelchair patients are faced with problems such as incontinence in urination and defecation and frequent contact with injections. In this case, the accessories made of carbon fiber composite materials show the durability that ordinary metal materials cannot match.
At present, carbon fiber composites are mainly used in handrails, arm supports, foot supports, leg supports, backrests, apron panels, frame tubes and other accessories. Most of these accessories can be adjusted in height. Carbon fiber composites are easy to assemble with the wheelchair as a whole through mechanical connection. The most important thing is that after the use of carbon fiber composites, the overall weight of the wheelchair has been significantly reduced, and as a component with high use frequency, It also becomes more durable.
Carbon fiber composites have excellent performance and have been widely used in civil daily life. After decades of application verification, they are safe and reliable for the environment and human health.
With the continuous progress of medical technology, medical equipment is also constantly innovating and developing. The investment and application of carbon fiber in medical devices represents a new trend and direction, and will certainly usher in a broader application prospect in the future.
Source: Fast Technology
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