ANALYSIS OF BIOMEDICAL DEVICES
ANALYSIS OF TITANIUM ALLOYS FOR IMPLANTABLE PROSTHESES
The APM laboratory provides advanced analysis services for biomedical devices, with a particular focus on the quality, safety, and compliance of materials used in the production of implantable medical devices. The primary goal is to ensure that these devices meet regulatory standards and required specifications, while also ensuring patient health protection.
APM specializes in a wide range of analyses, including chemical analysis to verify the composition and detect potential contaminants in materials, microstructural analysis to examine the internal structure of materials and ensure there are no defects that could compromise their performance. Additionally, the laboratory performs mechanical property measurements to evaluate the resistance and durability of devices over time, ensuring that they can withstand the stresses they are exposed to in the biological environment.
Another critical aspect of the analyses conducted by APM involves the determination of gaseous impurities such as hydrogen, oxygen, and nitrogen in the alloys used. These impurities can negatively affect the mechanical properties and corrosion resistance of the materials.
With a team of experts and the use of cutting-edge technologies, APM is able to provide a comprehensive and reliable analysis service to ensure that biomedical devices are safe, durable, and compliant with international standards.
CHEMICAL ANALYSIS OF BIOMEDICAL DEVICES
Chemical Analysis of Implantable Medical Devices
Chemical analysis of implantable medical devices is a crucial aspect in ensuring that these products are safe, effective, and compliant with international regulations. Specifically, ISO 10993-18 sets the requirements for the chemical characterization of materials used in medical devices, with the goal of ensuring that they do not pose risks to patient health, particularly concerning biocompatibility.
The standard provides guidelines for the chemical characterization and control of materials, including metals, polymers, ceramics, and composites, and requires specific tests to identify and quantify chemicals that may be released from the devices.
Biocompatibility not only concerns the absence of toxic reactions but also the interaction of the material with biological fluids, tissues, and cells. Substances released into the body via the device must be accurately analyzed to ensure no harmful contaminants, such as heavy metals, solvents, additives, or other chemical impurities, are present. Companies involved in the production, regulation, or evaluation of medical devices therefore understand the need to conduct thorough testing to ensure material quality.
INSTRUMENTAL TECHNIQUES FOR ANALYSIS
Chemical analysis is carried out using various instrumental techniques, chosen based on the type of material (metal, rubber, polymer, ceramic) being tested. Commonly employed techniques include:
MICROSTRUCTURAL ANALYSIS OF BIOMEDICAL DEVICES
Microstructural Analysis of Medical Devices
Microstructural analysis of biomedical devices is a crucial process to ensure that the materials used are suitable for medical device applications, meeting strict biocompatibility and safety requirements. The microstructure of titanium and its alloys must be optimized to offer maximum strength, elasticity, and corrosion resistance—key characteristics for the reliability of implantable devices.
APM specializes in performing thorough microstructural analysis of materials such as titanium and its alloys, which are widely used in the production of orthopedic prostheses and other implantable medical devices.
Moreover, continuous monitoring during the manufacturing process allows for real-time identification and correction of potential issues, reducing the risk of defects in the finished product and improving the overall quality of the implantable device.
HOT WORKING OF TITANIUM AND ITS ALLOYS
Hot working of titanium and its alloys, including processes such as rolling, forging, and molding, is a critical step in shaping the material into the desired form for implantable devices. These processes are essential not only for forming the raw material but also for optimizing the mechanical and biocompatible properties of the finished product. The resulting microstructure is highly dependent on temperature conditions and processing stages.
Even small temperature variations—sometimes just a few degrees Celsius—can significantly affect the structure and mechanical properties of titanium, which is highly sensitive to processing conditions. For example, in the production of titanium orthopedic prostheses, a homogeneous microstructure is essential to ensure the strength and durability of the device over time. Imperfections or irregularities in the microstructure could compromise the safety and functionality of the implant, increasing the risk of failure during use.
METALLOGRAPHIC CONTROL OF THE MICROSTRUCTURE
Metallographic examination is essential to verify that the microstructure of titanium and its alloys meets the required quality standards, as specified in ISO 20160. Microstructural control is conducted at each stage of the manufacturing process, from raw material to finished product, to ensure that each processing phase adheres to the specified requirements.
The metallographic analysis process begins with preparing a specimen of the material. The sample is polished to achieve a mirror-like finish to allow for detailed examination of the microstructure. A selective chemical etching is then applied to clearly highlight structural details such as titanium grains, intermetallic phases, and potential inhomogeneities present in the material. Once the specimen is prepared, it is analyzed using a reflected light metallographic microscope. This microscope allows for high magnification observation, revealing fine surface details and enabling comparison with the reference values set by ISO 20160.
ANALYSIS OF HARDENED COATINGS (TiN/TiCN)
In cases where implantable devices are coated with a hardened layer of titanium nitride or titanium carbonitride (TiN/TiCN), the microstructural analysis becomes even more sophisticated. TiN or TiCN coatings are used to enhance wear resistance, high-temperature stability, and the overall durability of the device.
To perform an accurate analysis of the coating, metallographic analysis is combined with scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) microanalysis. SEM allows for superior detail observation of the coating’s microstructure compared to optical microscopes, while EDS provides precise elemental information about the chemical composition of the materials present. These techniques allow for the measurement of coating thickness and the identification of the chemical nature of surface layers, verifying that the coating meets specifications and that there are no defects such as microcracks or inhomogeneities that could compromise its effectiveness.
MECHANICAL PROPERTY MEASUREMENTS IN BIOMEDICAL DEVICES
Measurement of Mechanical Properties
Measuring the mechanical properties of biomedical devices is crucial for ensuring their reliability, safety, and long-term functionality. For implantable prostheses, it is essential that the mechanical properties of the material used are suitable to withstand the stresses and loads they will be subjected to during use.
All mechanical testing is conducted following international reference standards to ensure the quality and safety of biomedical devices. For example, hardness measurements are typically carried out using the Vickers scale, in accordance with ISO 6507-1.
For tensile testing, which includes evaluating yield strength, breaking load, and elongation at break, the test is performed according to ISO 6892-1, or if required, following ASTM E8/E8M standards. Adopting these international standards ensures that tests are conducted rigorously and that biomedical devices meet safety and performance requirements.
MATERIAL HARDNESS
Hardness is one of the fundamental mechanical properties for evaluating an implantable material, such as an orthopedic prosthesis. It describes the material’s resistance to permanent deformation under load, which is crucial to ensure the device does not suffer damage during use. Hardness measurement is primarily carried out using the Vickers scale, a hardness testing technique in which a diamond pyramid is pressed onto the surface of the sample with a specific force.
The Vickers hardness test is conducted according to ISO 6507-1 and provides an accurate measure of the material’s hardness. The results of this test help determine whether the material chosen for the prosthesis is sufficiently resistant to wear, fatigue, and the pressure applied during daily physical activity.
YIELD STRENGTH
Yield strength is a parameter that indicates the point at which a material, such as a metal alloy used in a prosthesis, begins to undergo permanent plastic deformation under stress. This is a critical data point for the safety of an implant, as insufficient yield strength could lead to deformation or failure of the implantable device, potentially causing harm to the patient.
This property is commonly measured using a tensile test, which determines how a material resists forces that tend to elongate it, providing insight into the material’s behavior at the limit of its elasticity.
UNIT BREAKING LOAD
The unit breaking load represents the maximum force a material can withstand before breaking, and its measurement is crucial for determining the durability of an implantable device, such as a prosthesis. Practically, this test helps establish how much stress the material can resist before failing, which is vital for devices exposed to continuous mechanical stresses within the human body.
ELONGATION AT BREAK
Elongation at break is a parameter that indicates how much a material can stretch before it breaks, directly correlating to its plasticity. Excessive elongation may indicate that the material is too fragile or insufficiently resistant to deformation. On the other hand, a material with good elongation at break is able to absorb stresses without fracturing, an important characteristic for prostheses that must withstand bending or compression forces.
Hydrogen, Oxygen, and Nitrogen Analysis
The determination of hydrogen, oxygen, and nitrogen content in ferroalloys, stainless steels, copper and copper alloys, titanium and titanium alloys, cobalt and cobalt alloys, nickel and nickel alloys is crucial for ensuring material quality and performance. Titanium alloys, in particular, are widely used in the biomedical field due to their exceptional mechanical, chemical, and biocompatible properties.
However, the presence of gaseous impurities such as hydrogen, oxygen, and nitrogen can significantly affect their performance, negatively impacting the quality and longevity of implantable devices. Therefore, precise analysis of these impurities is essential to guarantee the safety, functionality, and durability of biomedical devices.
HYDROGEN ANALYSIS
Hydrogen in titanium alloys can be present in the form of soluble or interstitial hydrogen. Its presence can cause embrittlement of the material and reduce corrosion resistance, a phenomenon known as hydrogen embrittlement. To quantify hydrogen, specific analyzers are used according to ASTM E1447, allowing for precise and sensitive measurements to ensure that the alloy is free from harmful contamination.
OXYGEN ANALYSIS
Oxygen can be present in titanium alloys either as dissolved oxygen or as oxides. Excess oxygen can weaken the mechanical properties of the alloy, causing brittleness and reducing its corrosion resistance. Oxygen analysis is conducted using specific analyzers according to ASTM E1409-13 which enables precise quantification of oxygen content, ensuring that titanium retains its optimal performance.
NITROGEN ANALYSIS
Nitrogen in titanium alloys may be present as a residual impurity or in compounds such as nitride and carbonitride. While nitrogen does not directly affect mechanical strength, its presence can compromise the alloy’s corrosion resistance and workability. Nitrogen analysis is performed using a specific analyzer according to ASTM E1409-13, providing accurate and sensitive quantification of nitrogen content, thereby preventing potential issues related to the longevity and functionality of the device.