Meeting the challenges of medical cable assembly design

By Avnet Staff   |   April 1, 2025   |   Provided By Avnet

Cable assemblies play a crucial role in the medical industry, providing the essential connection between medical devices, patients and healthcare professionals. These assemblies must meet stringent requirements to ensure patient safety while delivering reliable performance and compliance with industry regulations.

Unlike standard industrial applications, medical cables face unique challenges. The needs for hygiene, biocompatibility and electromagnetic compatibility (EMC) mean that designers must carefully consider the materials and construction of their chosen cable.

Key design challenges

The medical industry imposes stringent requirements on all equipment to ensure the highest levels of safety and performance. Medical cable assemblies must withstand rigorous operational environments, including frequent handling, exposure to harsh sterilization processes, and continuous mechanical stress. In addition to durability, they must ensure the integrity of transmitted signals and power, as even the slightest failure can jeopardize patient health.

The medical industry is also embracing developments in the field of personal electronics. The smartwatch is one example of how technology has led to an expansion in the use of wearable devices. These can be found in many areas of medicine, not only for patient monitoring but also in diagnosis and treatment. Combined with technology such as nebulizers and insulin delivery systems, patients can receive more medical care at home.

The use of advanced technologies, combined with their employment beyond the traditional environments of the hospital or doctor’s office, places even greater demands on durability. Making the right choices at the start of the design process will greatly impact the suitability of the finished product.

Hygiene and sterilization in medical cables

Patient safety must be the primary consideration when designing any device for the healthcare industry. Preventing infection is vital to providing the best outcome for patients. This demands a sterile environment, and the cables used to connect medical devices must be designed to withstand sterilization processes without degradation.

Sterilization is achieved using one of several methods. Heat sterilization takes place in an autoclave reaching temperatures of more than 120°C. This process requires cable materials that can endure high temperatures and resist moisture without compromising structural integrity.

Other methods include the use of Ethylene Oxide (EO or EtO) in gaseous form that does not require the high temperatures of an autoclave. It uses a vacuum-based process that can penetrate surfaces, even allowing the sterilization of devices inside certain packaging materials. This lends itself to single-use, disposable medical devices. 

Some materials often used for commercial cable assemblies are less suited to medical applications. For example, cables commonly use polyvinyl chloride (PVC) in their construction. While PVC is flexible and resistant to abrasion, its operating temperature can be as low as 60°C. Clearly, this is not the correct choice for any device to be placed in an autoclave. Instead, medical cables often use materials like silicone, which can withstand high temperatures and chemical exposure while maintaining flexibility and durability.

Biocompatibility to ensure patient safety

Many medical cables come into direct contact with patients, potentially for long periods. Therefore, biocompatibility is a critical consideration. A biocompatible material prevents adverse reactions, such as irritation, toxicity or an allergic reaction when in contact with human tissue.

The impact of non-biocompatible materials can include everything from product recalls to the consequences of regulatory non-compliance. However, the long-term effects on the patient should be the focus for designers. The ISO 10993-1 standard is responsible for the biological evaluation of medical devices. Not only does it cover how materials are tested and their effects on the patient, but it also addresses the hazards created if devices break.

Electromagnetic compatibility

Our environment is filled with electronic devices that create electromagnetic interference (EMI). This can be intentional, such as the radiation emitted by wireless transmitters, and unintended, such as the interference created by faulty electrical devices. In general applications, this can be inconvenient. However, medical devices often depend on the measurement of very small voltages, such as the electrical brain activity detected by an electroencephalogram (EEG). Ensuring electromagnetic compatibility (EMC) is crucial to prevent interference between devices, patient monitoring systems and surgical instruments.

Effective EMC design requires efficient shielding techniques. Cables can be protected using a combination of conductive foil wrap and woven copper braid under the sheath to contain electromagnetic radiation and prevent signal degradation. Designers must comply with EMC standards such as IEC 60601, which governs the safety and performance of medical electrical equipment.

Compliance and regulatory standards

The medical industry is heavily regulated to ensure the safety and effectiveness of medical devices, including cable assemblies. Regulatory bodies such as the U.S. Food and Drug Administration (FDA), the European Medicines Agency (EMA), and the International Electrotechnical Commission (IEC) impose strict guidelines for material selection, manufacturing processes and performance testing.

Several standards cover the electrical and manufacturing requirements applicable to medical cable assemblies, including:

• IEC 60601: Focuses on electrical safety and EMC for medical devices
• ISO 13485: Specifies quality management system requirements for medical device manufacturers

Compliance with these regulations ensures that medical cables meet the highest safety standards and perform reliably in critical healthcare applications.

Comparision of Plastic Materials for Medical Applications

Materials selection

The selection of materials for medical cable assemblies significantly impacts overall cost. While performance, safety and compliance are paramount, cost-effectiveness is always a consideration.

Here's a breakdown of how material choices influence cost:

• Raw material costs: Different materials have vastly different price points. Commodity plastics like PVC are generally less expensive than high-performance materials such as silicone, TPE, PTFE (Teflon) or PEEK. While PVC might seem like a cost-effective option, its limitations regarding temperature resistance and biocompatibility make it unsuitable for many medical applications. Opting for materials like silicone or TPE, while more expensive, ensures compliance, reduces the risk of product failure and avoids potential recalls, ultimately providing better value.
• Manufacturing complexity: Some materials are easier to process and manufacture than others. For example, PVC is readily extruded and molded, leading to lower manufacturing costs. In contrast, materials like PTFE or PEEK require specialized processing techniques, such as etching or high-temperature molding, which can increase manufacturing complexity and cost.
• Sterilization compatibility: The chosen sterilization method also influences material costs. Materials that can withstand multiple autoclave cycles (e.g., silicone, PTFE, PEEK) may have a higher initial cost but offer long-term value by enabling reusable cable assemblies.
• Shielding requirements: EMC requirements drive material choices and costs. Effective shielding often involves using conductive materials like copper braid or foil. The density and type of shielding affect the cost, with denser braids or double-layer shielding adding to the overall expense. The final choice must balance the level of shielding with the specific EMC requirements.
• Biocompatibility compliance: Materials that meet stringent biocompatibility standards (ISO 10993-1) often come at a premium. Extensive testing and certification processes add to the cost of these materials. However, using biocompatible materials is essential for patient safety and regulatory compliance, making it a non-negotiable aspect of medical cable design.

Lead times are a related factor that should be taken into consideration. The more specialized the materials, the more they may be subject to lead time fluctuation with demand. This may limit the choice of vendors, indirectly leading to higher costs, both in terms of prices and supply chain disruption.

Conclusion

As medical technology continues to advance, the development of innovative cable solutions plays an important role, not only in traditional healthcare environments but in homes and communities. Cables must be designed to deliver high performance to support the evolution of healthcare practices and improve patient outcomes.

Medical cable assemblies face an unusual set of challenges that combine the need for hygiene, biocompatibility, electromagnetic compatibility, regulatory compliance, and economic viability. The choice of sheath material plays an enormous role in deciding its suitability for medical applications.

While opting for the cheapest materials might seem appealing initially, it can lead to compromises in quality, safety, long-term reliability, and total cost of ownership over the life of the assembly.

Avnet Nogales provides interconnect assembly services for critical applications such as medical and military/aerospace. Contact your Avnet rep for more information

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