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Choosing a Biocompatible Material for a Skin-Contact or Sterilized Part: ISO 10993 at the Material Level
Biocompatibility is decided at two levels, and confusing them is the most common mistake in specifying a medical converted part. The material maker evaluates a specific grade against frameworks such as ISO 10993 and USP Class VI, and the device maker owns the finished-device biocompatibility and regulatory file. A die-cut converter sits in between: it cuts a grade that the maker reports as evaluated for the relevant body contact, to your drawing.
This guide walks the material families that lead for skin-contact, sterilized, wound-care and fluid-path parts, explains how the standards apply at the material level, and ends with a guided selector that returns a cautiously framed material direction.
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The application problem: a material is selected for a contact, not certified for a device
H-O Products is a precision die-cut converter, and every medical and biocompatible part is made to order from sheet, slab, or roll stock cut to a drawing. The concrete problem an engineer faces is that "biocompatible" is not one property and not a single test result. It depends on what the part touches and for how long. ISO 10993-1 classifies a device by contact type (a surface device on intact skin, an external-communicating device, or an implant) and by duration (limited under 24 hours, prolonged from 24 hours to 30 days, or permanent beyond 30 days).
Those two axes set which biological endpoints apply, which in turn narrows the material grade.
A die-cut converter cannot resolve that for the finished device, and should not claim to. What a converter can do is cut a grade that the material maker reports as evaluated for the relevant contact, document what was sourced, and hold the part to a drawing. The selection logic below is the part an engineer actually controls when picking a grade.
Why it is challenging: contact, sterilization, and adhesion pull in different directions
Material selection for a body-contact part is hard because the requirements compete. A grade that is comfortable and breathable against skin for a multi-day wearable is rarely the grade that survives dozens of autoclave cycles on a reusable instrument. A foam that manages wound exudate well is open-cell and through-porous, which is the opposite of the closed-cell seal a moisture barrier needs.
Adding a skin-contact adhesive introduces a separate evaluation, because the adhesive is its own material in contact with skin. On top of that, the chosen sterilization method changes the material: gamma irradiation crosslinks silicone and can raise its modulus and lower elasticity at high dose, while ethylene oxide is broadly compatible across common medical polymers. Get any one of these wrong and the part fails in service even though it looked correct on a datasheet.
The families below are organized around resolving those competing constraints.
Recommended material families
Five material families cover most biocompatible die-cut parts. Each is named here as a material, with cautious framing, and each should be confirmed against the manufacturer's current technical data sheet for the specific grade and its biological-evaluation basis.
Microcellular polyurethane (skin cushion, orthotic soft side)
PORON® Medical microcellular polyurethane is commonly used where a soft, comfortable, breathable cushion sits against intact skin or inside an orthosis. Its controlled force-deflection at low stress and low compression set let it conform without bottoming out and hold cushion over a long wear, which is why it is widely treated as an industry-standard orthotic and prosthetic cushioning material.
Microcellular PU is often specified for single-use or limited-reuse wearables; its tolerance to repeated sterilization is method- and grade-dependent, so verify the cycle on the current TDS.
Medical silicone, solid and closed-cell (skin-contact seals, sterilizable parts)
Platinum-cured medical silicone leads where a part must seal, cushion, or grip and also survive repeated cleaning and sterilization. BISCO® MS-1600 platinum-cured solid silicone holds properties across a wide service range and is reported as evaluated to USP Class VI and ISO 10993 with low migratable silicones and resistance to common hospital sanitizers. SSP-2390 platinum-cured solid silicone is the choice when low extractables and high purity matter in a fluid path, with an FDA composition basis and USP Class VI evaluation reported by its maker.
Where a moisture-resistant gasket, bumper, or seal is needed, a BISCO® MS-80 / MS-96 medical cellular silicone closes the cell structure against fluid ingress. A skin-contact silicone foam is a separate, softer family for comfortable on-body cushions, distinct from the solid grades above.
Reticulated polyurethane (wound-care, NPWT, diagnostic wicks)
Reticulated polyurethane foam is open-cell and through-porous, so it absorbs, wicks, and distributes fluid. It is the canonical absorbent and fluid-distribution layer in wound dressings and negative-pressure wound therapy constructions, where pore grade tunes absorption and flow. Because wound care involves a breached surface, the evaluation is more stringent than for intact skin, so the grade must be one the maker reports as evaluated for that contact.
Crosslinked polyethylene and EVA (durable body padding)
For firm, durable padding and liners in orthotic, prosthetic, and rehab devices, crosslinked polyethylene foam provides a fine-celled, closed-cell base that resists bottoming, while EVA foam adds a softer, resilient layer. A common stack pairs a firm crosslinked PE base with a soft EVA or microcellular PU layer on the skin side for comfort.
FDA-grade foams and films (diagnostic and sterile-barrier parts)
For diagnostic cartridge seals, wicks, spacers, and sterile-barrier or packaging parts, FDA-grade white and FDA-grade translucent materials provide a fluid-contact composition basis (for example a CFR citation such as 21 CFR 177.2600 for repeated-use rubber articles). Translucent grades help where visibility into a fluid path is useful. It is worth being precise here: "FDA-grade" describes a material composition or contact basis, not a finished-device clearance.
How the standards apply at the material level
The frameworks an engineer will see on a material datasheet are test methods the grade has been evaluated against, not guarantees about a finished device. Used precisely, they support a compliance argument that the device maker completes.
| Framework | What it evaluates | Where it applies |
|---|---|---|
| ISO 10993-1 | Classifies the device by contact type and duration; sets which endpoints apply | The starting point for any body-contact part |
| ISO 10993-5 | In vitro cytotoxicity (pass/fail) | One of the "big three" for most surface devices |
| ISO 10993-10 | Skin sensitization | Important for multi-day skin adhesives and cushions |
| ISO 10993-23 | Irritation | Important for any skin or mucosal contact |
| USP Class VI (USP <88>) | Strictest USP in-vivo plastics class: systemic toxicity, intracutaneous, and muscle-implant screens | A common material-level screen for medical plastics and elastomers |
| 21 CFR (e.g. 177.2600) | Composition basis for repeated-use fluid or food contact | The basis behind an "FDA-grade" material |
| ASTM D3574 | Flexible cellular foam properties: density, IFD, compression set, tensile and tear | Characterizing a foam cushion or absorbent layer |
Biocompatible Material Direction Selector
A soft, breathable, low-compression-set cushion for prolonged intact-skin wear. Confirm the grade is evaluated for the relevant ISO 10993 endpoints, and pair it with a skin adhesive evaluated to ISO 10993-10 and -23.
Illustrative only; confirm against current material data and a drawing review. This selector returns a material family direction, not a grade, a performance value, or a finished-device clearance. The specific grade, its biological-evaluation basis (ISO 10993 / USP Class VI / FDA composition), and its sterilization tolerance are confirmed on the manufacturer's current technical data sheet, and the finished-device biocompatibility file is owned by the device maker.
Design and converting considerations
Once the family is chosen, the converted part is usually a stack rather than a single layer. A skin-interface part, from the body outward, is typically a skin-side adhesive, a die-cut cushion foam, and a face film or carrier, all on a release liner. H-O converts the die-cut cushion and the adhesive layers.
Practical decisions that belong in the drawing review include the adhesive choice (silicone, acrylic, or hydrocolloid skin pressure-sensitive adhesives behave differently over a multi-day wear), the liner and any pull-tab for clean placement on a line, and whether the part is die-cut, kiss-cut on the liner, laser or waterjet cut, laminated, slit to width, or kitted as a sub-assembly.
For a fluid-management part, the pore grade of the reticulated foam is the variable that tunes absorption and flow, so it is specified to the job rather than left generic.
Common failure modes
| Failure mode | Mechanism | The fix |
|---|---|---|
| Skin irritation or sensitization | Wrong adhesive or a grade not evaluated for the contact | Use a grade and adhesive evaluated to the relevant ISO 10993 parts (especially -10 and -23) |
| Sterilization degradation | A material the chosen cycle degrades, for example high-dose gamma embrittling silicone | Match the material to the method and verify the cycle and cycle count on the TDS |
| Loss of cushion | Compression set in a reused or long-wear part from the wrong foam | Specify a low-set microcellular PU for the cushion role |
| Extractables in a fluid path | Peroxide-cured silicone can leave by-products | Specify a platinum-cured grade for low-extractable fluid contact |
| Maceration in wound care | Poor exudate management from the wrong absorbency or wicking grade | Select an open-cell reticulated PU grade evaluated for the breached-surface contact |
| Over-claiming a device clearance | Treating a material-level evaluation as a finished-device clearance | Keep the material evaluated by its maker and the device file owned by the device maker |
How H-O Products helps
H-O Products is a precision die-cut converter. Once the contact, duration, and sterilization method are known, we recommend a material family and grade direction across microcellular polyurethane, medical silicone (solid and closed-cell), reticulated polyurethane, crosslinked polyethylene and EVA, and FDA-grade foams and films, then convert the maker's stock to your drawing: die-cut, kiss-cut, laser or waterjet cut, laminated, slit to width, and kitted.
Documentation available on request includes the material technical data sheet, a certificate of conformance, lot traceability, first-article inspection, and the material maker's biological-evaluation basis for the grade, assembled into a customer-specified compliance package, all under our ISO 9001:2015 certified quality management system. We do not produce the raw stock, we do not certify the finished device, and we are an ISO 9001:2015 certified organization, not an ISO 13485 or FDA-registered facility.
Grade properties and biological-evaluation results are confirmed against the manufacturer's current technical data sheet, and the finished-device file belongs to the device maker.
Frequently asked questions
Is ISO 10993 the same as USP Class VI?
No. ISO 10993 is a family of biological-evaluation methods selected by the device's contact type and duration; USP Class VI is the strictest class of the USP in-vivo plastics-reactivity screen. A material datasheet often reports both. Both are material-level evaluations; neither is a finished-device clearance, which the device maker owns.
Which silicone holds up to repeated autoclaving?
Solid and medical cellular silicone (BISCO MS-80 / MS-96)s generally tolerate steam, ethylene oxide, and gamma well, which is why they lead for reusable instrument parts. The caution is gamma at high dose, which crosslinks silicone and can change its elasticity, so the method and cycle count are verified on the current technical data sheet.
What is the difference between platinum-cured and peroxide-cured silicone?
Platinum-cured silicone leaves no peroxide cure by-products, which makes it the lower-extractable choice for a fluid path or a sensitive contact. Peroxide-cured silicone can leave by-products. For low-extractable medical work, platinum-cured grades such as the SSP-2390 and BISCO MS-1600 families are commonly specified.
Can H-O certify that my device is biocompatible?
No. H-O is a die-cut converter and an ISO 9001:2015 certified organization. We cut a grade the material maker reports as evaluated for the relevant contact and provide the supporting documentation on request. The finished-device biocompatibility and regulatory file is owned by the device maker.
Get a biocompatible material recommendation
Tell us the contact type, the duration, the mechanical job, and the sterilization method, and we will recommend a material family and grade direction and convert samples on your footprint.
Samples typically ship in 3 to 5 business days for common die-cut configurations; standard production runs about two weeks; special orders are quoted to the job.
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Last updated · Reviewed by H-O Products engineering (ISO 9001:2015 certified converter, Winsted, CT).
References
- ISO 10993-1, -5, -10 and -23 (biological evaluation of medical devices: evaluation and testing, cytotoxicity, sensitization, irritation). ISO.
- USP <88> (in-vivo biological reactivity, USP Class VI). U.S. Pharmacopeia.
- 21 CFR (fluid-contact composition basis). U.S. FDA.
- ASTM D3574 (flexible cellular foam) and ASTM D2240 (durometer hardness). ASTM International.
- ASTM D3330 (pressure-sensitive adhesive peel). ASTM International.
- Manufacturer technical data sheets: BISCO MS-1600 platinum-cured solid silicone, BISCO MS-80 / MS-96 medical cellular medical silicone, and PORON Medical microcellular polyurethane.
This article cites general engineering principles and published standards (ISO 10993 for biological evaluation, USP <88> for in-vivo biological reactivity / USP Class VI, 21 CFR for fluid-contact composition basis, ASTM D3574 for flexible cellular foam, ASTM D3330 for pressure-sensitive adhesive peel, ASTM D2240 for durometer hardness). Material names refer to material families H-O Products converts.
Biological-evaluation results, durometer ranges, densities, and sterilization doses are grade-specific; confirm all values against the manufacturer's current technical data sheet.
The material maker evaluates the grade against the relevant frameworks; the finished-device biocompatibility and regulatory file is owned by the device maker. All parts are custom manufactured to order and minimum production run quantities apply. H-O is a die-cut converter and an ISO 9001:2015 certified organization, not an ISO 13485 or FDA-registered facility, and does not certify finished devices.