Flexibility for Medical Device Design

What is the right material for my medical device?

One question every device engineer needs to ask is: what is the right material for my device? How can I ensure it works regardless of demanding environments for decades to come and most importantly that it delivers functionalities that satisfy end user’s needs?

Biocompatibility regulations worldwide are constantly evolving and have inspired manufacturers of flexible medical components to look for newer and safer substrates. These regulations may restrict the types of materials that can be safely incorporated into class II, III and III medical devices.

The industry continues to use traditional flexible materials such as silicone, natural rubber, soft PVC and polyurethane. However, the European Union and Mainland China are working to permanently ban soft PVC formulations that contain phthalate plasticizers. The migratable plasticizers associated with these substrates are suspected of leaching out of the PVC and into patient’s bodies. 

Other materials also present engineering challenges. For example, silicone, while extremely soft, is hard to bond using adhesives. Latex rubber, while highly elastic, flexible and durable, is highly allergic for some people. So, device manufacturers continue to seek substitute substrates that are biocompatible throughout the world and offer processing and performance advantages.

Relatively new materials, thermoplastics such as TPEs and TPUs, are highly versatile and chemically-inert. Their flexibility can range from gel-like to semi-rigid, their optical properties from opaque to clear. These thermoplastics are available with differing strength, toughness, chemical/UV-resistance and temperature performance, and are recyclable. Despite their higher cost and a reputation for being harder to process and bond, TPEs and TPUs are in demand for medical devices, especially devices that require high flexibility. 

So what substrates should you consider when designing a flexible medical device? To select the best materials for an application, you need to intimately understand the production process for the device and its end use environment. You may need the materials to be: 

You may also want to consider methods to simplify production, reduce costs and manufacture the most robust device possible. In all likelihood, you will assemble small, complex plastic components using adhesives. A designer should consider consulting with an adhesive expert on: 

  • substrate/adhesive combinations and cure requirements
  • surface treatments that can enhance bonds
  • joint designs that will achieve the most robust bonds possible. 

Do you have an application, question or idea, please contact me.

Author Andres Bulto, Regional Business Development Manager and KAM IA Medical