Medical Cable Materials: Biocompatibility and ISO 10993
Quick Answer
Material selection for a medical cable is set by three constraints working together: what the cable touches and for how long, which determines the biological evaluation required under ISO 10993; how it will be sterilised, which rules out certain polymers entirely; and what it will be cleaned with in daily use, which governs how long it survives in the field. All three should be settled before tooling. Changing a jacket material after validation means repeating the evaluation.
Who this is for
Design engineers, R&D and regulatory teams at medical device manufacturers specifying cables and cable assemblies.
Materials selection is a design decision, not a purchasing one
Cable material is often treated as something to optimise late, once the electrical design is settled. In a medical device that sequence causes expensive rework.
The material determines biological evaluation. It determines which sterilisation methods remain available. It determines how the assembly behaves after two years of disinfectant exposure. And once a device has been validated with a given material, substituting it is not a purchasing change — it is a design change, with the verification burden that carries.
The practical consequence: decide the material constraints before tooling, not after. The three inputs below are what a supplier needs in order to recommend anything sensible.
1. What does it touch, and for how long?
ISO 10993 — Biological evaluation of medical devices — structures evaluation around two questions: the nature of body contact and the duration of that contact.
Nature of contact is broadly categorised as:
- Surface devices — contacting intact skin, mucosal membranes, or breached surfaces
- External communicating devices — contacting blood path, tissue or bone indirectly
- Implant devices — in contact with tissue or blood internally
Duration is categorised as limited, prolonged, or long-term contact.
The combination determines which biological endpoints require evaluation. A reusable ECG leadwire contacting intact skin sits in a very different category from a component in an external communicating device, and the evaluation burden differs accordingly.
Why this matters at design stage: the classification is a property of the finished device and its intended use, not of the cable in isolation. A supplier cannot determine it for you. Supply the contact classification and duration with the enquiry, and the material conversation becomes straightforward. Without it, any material recommendation is a guess.
A second point that catches teams out: evaluation applies to the finished assembly, not only to the raw polymer. Processing, additives, colourants and adhesives all form part of what is evaluated. A material certificate for the base polymer does not by itself establish that the finished assembly is suitable.
2. Material families and their trade-offs
Material family comparison
| PVC | TPE / TPU | Silicone | |
|---|---|---|---|
| Flexibility | Good, depends on formulation | Good to excellent | Excellent, retains at low temperature |
| Autoclave compatible | Generally no | Varies; most grades no | Yes |
| EtO compatible | Yes | Yes | Yes |
| Gamma / e-beam | Can discolour and embrittle | Generally acceptable, grade dependent | Generally acceptable |
| Chemical resistance | Moderate | Good | Very good |
| Abrasion resistance | Moderate | Excellent | Lower |
| Flex life | Moderate | Excellent | Good |
| Relative cost | Lowest | Moderate | Highest |
| Typical use | Single-use and cost-sensitive assemblies | Reusable assemblies with high handling | High-temperature or repeated-sterilisation applications |
PVC remains widely used and is the most economical option, particularly for single-patient-use assemblies. Formulation matters considerably — plasticiser selection affects both flexibility and biological evaluation, and this is an area where regulatory expectations have shifted in some markets.
TPE and TPU have become the default for reusable assemblies subject to heavy handling. Flex life and abrasion resistance are the reason: a leadwire coiled and uncoiled several times a day is a mechanical fatigue problem before it is anything else.
Silicone is specified where repeated autoclaving or temperature extremes are involved. It is the most expensive option and has lower abrasion resistance, so it is chosen for a specific reason rather than as a default.
3. Sterilisation method constrains the material
Sterilisation is frequently decided late and then found to have eliminated the preferred material.
Sterilisation method constraints
| Method | Constraint |
|---|---|
| Ethylene oxide (EtO) | Broadly compatible with common cable polymers. Requires aeration; residuals must be managed. |
| Gamma irradiation | Can cause discolouration and embrittlement in some polymers. Effects are cumulative — repeat exposure matters for reusable devices. |
| E-beam | Similar considerations to gamma, with different dose distribution. |
| Steam autoclave | Repeated high-temperature, high-moisture cycles. Silicone handles this well; most PVC and many TPE grades do not. |
| Chemical / low-temperature | Material compatibility depends heavily on the specific agent and the polymer. |
The question to settle early: is the device single-use or reusable, and if reusable, how many sterilisation cycles must it survive? A material that tolerates one gamma cycle may not tolerate fifty.
4. Cleaning chemistry is the slow failure nobody specifies
Sterilisation gets specified. Cleaning usually does not — and in reusable devices, cleaning chemistry is what actually determines service life.
A reusable cable in a hospital is wiped with disinfectant between patients, potentially many times a day, for years. Common agents include quaternary ammonium compounds, sodium hypochlorite, alcohol and hydrogen peroxide formulations. Each interacts differently with each polymer, and the effects are cumulative rather than immediate.
The failure mode is gradual: surface tackiness, stiffening, cracking at flex points, print legibility loss, and eventually jacket splitting at the strain relief. None appears during validation. All appear in the field.
Two things reduce the risk:
- Specify the cleaning agents the device will actually encounter, not only those the IFU will recommend. Hospitals standardise on a disinfectant across a whole facility, and it may not be the one anticipated.
- Where possible, test the assembly against those agents rather than relying on published polymer resistance data, which is generally based on the base material rather than the finished construction.
A field observation worth noting: when a cluster of identical cables fails prematurely in one department but not others, the cause is frequently a local cleaning protocol rather than a manufacturing batch. Cleaning chemistry is a design input.
5. Flex life and mechanical durability
For most reusable medical cables, mechanical fatigue determines service life rather than electrical failure.
The determining factors:
- Conductor construction. Stranding and lay length govern how a conductor tolerates repeated bending. This is the single largest factor in flex life.
- Jacket material and wall thickness. A trade-off — thicker jackets resist abrasion but reduce flexibility and increase bend stress.
- Strain relief design. The transition between cable and connector is where the majority of field failures occur. Strain relief geometry and overmould design are what make the difference here, and they are a design decision rather than a material one.
- Minimum bend radius in real use. Not the specified value, but what happens when a cable is coiled tightly and stored in a drawer, or trapped in a bed rail.
When specifying, state the expected duty cycle. A transport monitor cable coiled and uncoiled a dozen times a day faces a different problem from a fixed installation cable, and the constructions that suit each are different.
What to specify before tooling
The information a supplier needs to recommend a material with any confidence:
Specification checklist before tooling
| # | Specify | Why |
|---|---|---|
| 1 | Patient contact type and duration | Determines the biological evaluation required |
| 2 | Single-use or reusable | Changes almost every other decision |
| 3 | Sterilisation method and number of cycles | Eliminates incompatible materials immediately |
| 4 | Cleaning and disinfection agents in real use | Determines field service life |
| 5 | Expected duty cycle and flex requirement | Drives conductor and jacket construction |
| 6 | Operating environment | Temperature, moisture, chemical exposure |
| 7 | Target markets | Regional regulatory expectations differ |
| 8 | Expected service life | Sets the durability target |
Items 1, 3 and 4 are the ones most often omitted, and they are the three that most constrain the answer.
How Orantech approaches this
Orantech manufactures medical cables and components for patient monitoring systems, providing OEM services that include design contribution and product modification alongside build-to-print manufacturing.
Where a design is still open, material and construction decisions are best made together rather than sequentially — the sterilisation method, the cleaning environment and the flex requirement interact, and optimising one in isolation usually compromises another.
Our lab capabilities page describes testing facilities, and process overview covers how designs move into production. Our article on design for manufacturing addresses the manufacturability side of the same decisions. Related reading: cable assembly best practices, cable assembly optimisation, quality systems, scaling production without compromising quality, and the supplier qualification checklist.
Specifying a new cable assembly? Contact us with the eight items above and we will come back with material and construction options.
Frequently asked questions
What is ISO 10993?
ISO 10993 is the international standard series covering biological evaluation of medical devices. It structures evaluation around the nature of body contact and its duration, which together determine which biological endpoints require assessment.
Does every medical cable require biocompatibility testing?
It depends on whether and how the cable contacts the patient, and for how long. The finished device's classification determines the requirement. A cable with no patient contact is evaluated differently from a reusable leadwire contacting intact skin.
Which material is best for reusable medical cables?
There is no single answer, because the requirements conflict. TPE and TPU are common for reusable assemblies because of flex life and abrasion resistance. Silicone is specified where repeated autoclaving is required. PVC remains widely used where cost matters and sterilisation demands are lower.
Can I change cable material after the device is validated?
Not as a purchasing decision. A material change to a patient-contact component is a design change, typically requiring re-evaluation and re-validation. This is why material constraints should be settled before tooling.
Why do cables fail at the connector?
The transition between cable and connector concentrates bending stress. Strain relief geometry and overmould design are the main determinants of how well an assembly survives repeated handling.
Does cleaning affect cable service life?
Considerably, and it is frequently under-specified. Repeated disinfectant exposure causes cumulative degradation — stiffening, cracking and jacket splitting — that does not appear during validation but determines real service life.
What information does a supplier need to recommend a material?
At minimum: patient contact type and duration, single-use or reusable, sterilisation method and cycle count, cleaning agents used in practice, and expected flex duty cycle.
Key takeaways
- Three constraints set the material: patient contact classification, sterilisation method, and cleaning chemistry in real use.
- Biological evaluation applies to the finished assembly, not only the base polymer. Additives, colourants and adhesives are part of what is assessed.
- Sterilisation method eliminates materials. Settle it before selecting a jacket, not after.
- Cleaning chemistry determines field service life and is the input most often left unspecified.
- Material change after validation is a design change, not a purchasing decision.