Part one of this series focuses on medical-grade silicone’s use in life-critical devices, including how it balances moisture and its importance in wound care and implants. Part two focuses on how to navigate material choices and leverage innovations like pigments and multilayer designs for complex devices.

In a tightly controlled cleanroom environment, a technician oversees the calendering process, a precision method used to produce medical-grade, high-performance silicone sheets with exact thickness and surface consistency. [Photo courtesy of Lubrizol]

Precise, high-quality silicone is increasingly essential for devices like catheters, surgical tools, prosthetics, long-term implants and wearable devices like continuous glucose monitors.

Biocompatible and breathable, medical-grade silicone is ideal for sealing, bonding and creating barriers of elastomeric components. Indeed, it can be a versatile, effective tool in a medical designer’s tool kit. But medical-grade silicone must meet the strictest purity standards to be trusted for life-critical devices.

Let’s explore some of the standards that high-quality silicone should meet, how its properties can provide advantages in some critical applications, and how medical device engineers can apply the material to meet today’s demands.

Getting to know silicone

The raw materials for silicone medical devices are produced by a number of suppliers. NuSil, Dupont, Wacker and Elkem are just a few examples of leading raw material providers, many of which have FDA master files and/or ISO 10993 testing to support their use in medical device applications.

These fine-tipped forceps are gently lifting an ultra-thin medical-grade silicone film —possibly as slim as 0.0005 in. — demonstrating the delicate handling required for this thin and flexible material in both manufacturing and surgical settings. [Photo courtesy of Lubrizol]

From these raw materials, a huge variety of medical devices can be produced, many of which make use of silicone film and sheeting. Medical-grade sheeting from Lubrizol is manufactured per ISO 13485 (QMS requirements) in ISO Class 7 cleanrooms. The resulting material can be cut and shaped to fit just about any need. Precision cutting is handled by die cutting and laser cutting. There are also multilayer options having (typically) two or three silicone layers that add another dimension of versatility.

Device developers also have plenty of options when it comes to thicknesses and configurations. With calendering, you get thicknesses from 0.005 to 0.125 in., while extrusion and knife coating can create ultrathin films as slim as 0.0005 in. The material is available in durometers from 1 to 80 Shore A, meaning it can be as soft as chewing gum or as firm as the sole of a dress shoe, depending on the requirement. It can also be reinforced with mesh for extra strength or foamed for extra softness. Add to that a choice of matte or glossy finishes, as well as a variety of colors, and engineers have a highly customizable material to deploy depending on their specific needs.

This technician is using a handheld gauge to verify thickness of a pigmented medical-grade silicone sheet. [Photo courtesy of Lubrizol]

Silicone also has unique functional properties that make it a go-to material for improving patient outcomes, especially in challenging applications.

Silicone films particularly shine in wound care because they are both gas-permeable and liquid-proof, which protects against bacteria while allowing breathability. Silicone gel sheets used for scar healing, for example, are often worn for a week or more and keep the skin hydrated while allowing water vapor to escape to prevent problems like overly soft skin. And because it is chemically inert, medical-grade silicone won’t cause irritation or allergies.

Carefully controlled manufacturing practices are required to form unvulcanized silicone into sheeting without contamination or flaw. Machines do heavy lifting, but the final stage of calendering is all about the human touch, with technicians teaming up to make sure each sheet is perfect before it moves on. [Photo courtesy of Lubrizol]

Silicone is frequently used as a primary wound dressing placed in direct contact with wounds. The perforated silicone film dressing stays in place for extended periods of time, so secondary wound dressings — used to absorb wound exudate — can be changed without disturbing the delicate healing skin. (Mepitel One manufactured by Mölnlycke Health Care, and Cuticell Contact manufactured by Essity are two examples of this type of product.) Plus, the transparency of the film means you can inspect the wound without removing the dressing, a huge benefit for undisturbed healing and cutting down on the number of changes.

How silicone is overcoming design challenges in critical applications

Reinforced sheeting takes silicone to the next level with embedded materials like polyester or nylon mesh. Depending on the application, meshes of varying thickness and aperture size (open area percentage) can be incorporated. Reinforced sheeting is ideal for devices and components that need to stay flexible but not stretch too far or tear.

A medical-grade silicone sheet winds through the processing line. [Photo courtesy of Lubrizol]

A common use of reinforced sheeting is at suture locations. Without reinforcement, sutures will cut through silicone, causing it to tear. Proper reinforcement makes suture sites stronger than the sutures themselves. Tissue expanders used in breast reconstruction or skin repair, for example, use suture tabs made from reinforced sheeting to ensure they remain in place.

Devices that are implanted in the brain, such as cerebral shunts and electrodes, can also rely on reinforced sheeting to handle physical stresses while being safe for nearby tissues. The silicone encapsulation prevents tissue from growing into the mesh and minimizes trauma to the surrounding tissue if the device moves or must be removed.

The bottom line is that silicone is a trusted material for OEMs because it’s tough when needed but soft enough for delicate uses.

Source：MDO