An already emerging technology in the consumer marketplace, manufacturing with optical grade silicone is starting to awaken the medical device industry to new possibilities. Still in its infancy within the healthcare market, the benefits of optically clear silicones offer some intriguing opportunities, and it is gaining interest for applications such as wearable technologies, endoscopes, optical sensors and instruments, medical lasers, diagnostics, light guides, and other medical device-related applications.
So, why should you consider using this material in your next medical device?
1. Overall design flexibility
Molding with optical grade silicone exhibits the many benefits associated with molding silicone rubber, but offer the added benefit of optical clarity needed for specific applications. Particularly in the medical device market, functionality is absolutely crucial, and with applications that are based around highly precise features, factors such as viscosity and molding parameters can make or break an entire program. The flexibility of optical grade silicone allows for designs with undercuts, negative draft angles, and fine features, and the assembly can be simplified by adding gasketing, sealing, and mounting features directly onto the part without compromising optical characteristics.
2. Ability to mold complex geometries
Most applications using optical grade silicone center on highly precise geometries that are almost impossible to fabricate with current materials and methods, and the low viscosity before cure makes molding optical grade silicone into complex shapes easier than with either glass or organic polymers. The most common application that optically clear silicone is being used for currently is to offer alternatives to polycarbonate, glass, or polymethyl methacrylate (PMMA) in situations where traditional materials are limiting the design or function of the device. Because of the low viscosity of the material, liquid injection molding of optical grade silicone allows for the molding of geometries that would not otherwise be possible with other polymers and glass. More precise features, varying wall thickness, reduced likelihood of sink allowing for thicker walls, small undercuts, negative draft, and difficult parts to fill are all possible with this material, allowing designers to really test their product’s limits.
3. Physical benefits during molding
OEMs and molders have been heading in the optical grade silicone direction because of the physical benefits silicone offers, including bacterial resistance, UV resistance, biocompatibility, low viscosity for molding precise and difficult features, temperature flexibility from -180F to 600F, chemical resistance, and fatigue and compression set resistance. It is also significantly lighter than most plastics and glass, and silicones in general are lighter in weight than traditional optical materials. Because the material is a thermoset, it does not have molded-in stresses like thermoplastic resins do.
4. Cosmetic benefits
Beyond the design and manufacturing benefits, there is a push towards optical grade silicones purely for cosmetic purposes. In the medical device world, quality is held above all else, and anything that appears to be flawed or dirty can be interpreted as a defect. Even if it has no effect on the function of the device, a yellowing or discolored part will be misinterpreted by doctors and patients. Regardless of how old it is or where it has been, optical grade silicone does not lose transparency or discolor with age, or with exposure to UV light, moisture, or heat. It requires no polishing after molding and is resistant to scratches, cracks, and breaks. Optical grade silicone is essentially unaffected by environmental factors and remains attractive throughout the life of the device, never worrying a doctor or patient if something is unsafe.
5. Overall reduction of costs
Due to the elastomeric nature of this material, it can reduce the need for additional parts and secondary operations, lowering tooling and non-recurring engineering (NRE) costs. For example, in a traditional lighting application where optical silicone is not being used, a lens and a seal would be two separate parts. By molding the lens with an optical grade silicone, the seal can be incorporated into the lens, ultimately eliminating an entirely different part and assembly step. This decreasing of the manufacturing process reduces inventory, bill of materials, time-to-market, and overall project cost significantly.
Using optical grade silicone in the healthcare industry is an exciting, albeit challenging opportunity for molders and OEMs. The design options with this material are endless, and due to the flexible nature of optically clear silicone, there is unlimited potential for new innovations and devices. We are starting to see a new wave of product development, silicone tooling, and DFM work being introduced to the marketplace with no intention of slowing down, and when it comes to designing and manufacturing with optical grade silicone, we have literally not scratched the surface.
Contact us today for more information on optical grade silicone!