Importance of surface integrity in manufacturing biomedical devices

The surface integrity of biomedical devices is crucial to their performance and effectiveness. Biomedical devices, such as orthopaedic implants, surgical instruments, and prosthetics, are often implanted or come in contact with living tissues and bodily fluids. As a result, the surface of these devices must be carefully designed and controlled to ensure biocompatibility, durability, and functionality.

The surface integrity of biomedical devices refers to the physical, chemical, and mechanical properties of their surfaces. These properties include surface topography, roughness, microstructure, and composition. Surface integrity can be affected by various manufacturing processes, such as machining, polishing, coating, and sterilisation. Therefore, it is important to carefully consider the impact of these processes on the surface integrity of biomedical devices.

There are several reasons why surface integrity is important in biomedical devices. First, the surface properties of these devices can affect their biocompatibility. For example, surface roughness can impact the adhesion and proliferation of cells on the device surface, which can affect tissue integration and healing. Similarly, the surface composition can influence the response of the immune system to the device, which can impact the success of the

Second, surface integrity can affect the durability and functionality of biomedical devices. For example, surface roughness can lead to wear and corrosion, which can cause mechanical failure and premature device failure. Similarly, surface defects or cracks can lead to stress concentrations, which can also cause device failure.
Finally, the surface properties of biomedical devices can impact their performance in various applications. For example, surface roughness can affect the friction and wear properties of orthopaedic implants, which can impact their longevity and function. Similarly, surface coatings can be used to enhance the antibacterial properties of surgical instruments, which can reduce the risk of infection.

Machining of such biomedical polymers urges to guarantee parts characterised by high geometrical precision as well as enhanced lifespan. However, conventional cutting fluids produce continuous flow chips that accumulate at the cutting zone, leading to possible degradation of the machined surface integrity. Using liquid nitrogen as a coolant at the cutting zone can achieve better surface integrity and improve the chip flow mechanism. Furthermore, improved surface integrity of the polymer can lower its wear rate against the metal head, therefore increasing the lifetime of the implant.

Cryogenic machining reduces the temperature at the cutting interface, which can help to mitigate the thermal effects of machining. The liquid nitrogen or other cryogenic fluids rapidly cool the cutting tool and workpiece, reducing the heat generated during machining.

The improved surface integrity of biomedical devices achieved through cryogenic machining can lead to several benefits, such as:

Enhanced biocompatibility: Cryogenic machining can help to minimise surface damage and contamination during the manufacturing process, which can improve the biocompatibility of biomedical devices. This can be particularly important for devices that will be implanted in the body, as any adverse reactions or inflammation caused by the device can have serious consequences.

Increased durability: Cryogenic machining can help to reduce the formation of defects such as cracks, voids, and residual stresses on the surface of biomedical devices, which can improve their durability and lifespan. This can be particularly important for devices that will be subjected to repeated stress or wear, such as orthopaedic implants.

Improved functionality: Cryogenic machining can help to produce smoother and more precise surfaces on biomedical devices, which can improve their functionality and performance. This can be particularly important for devices that require a high degree of accuracy, such as surgical instruments or diagnostic tools.

Greater patient safety: By reducing the risk of surface damage and contamination during manufacturing, cryogenic machining can help to improve patient safety by reducing the risk of adverse reactions or complications from biomedical devices.

In conclusion, cryogenic coolant can improve the surface integrity of the polymers because machining at sub-zero temperatures reduces the heat generation at the cutting zone and increases the crystallinity in the polymer, which becomes harder and varies its chip formation mechanism compared to dry cutting conditions.

By Nikhil Teja Sajja

Nikhil Teja Sajja is ESR 12. Nikhil’s project is titled “Cryogenic machining of UHMWPE acetabular cup inserts”.