By enabling new therapies for patients, better tools for surgeons and physicians, and diagnostics, which are more economical and accurate, new medical device designs propel healthcare forward. While the dimensions, tolerances, drawings, and CAD models for those devices document the idea of the engineer, materials are ultimately what bring that design to life. But, before innovative medical devices can make an impact in a patient’s life, it has to be made out of something.
For many new designs today, that something is a plastic resin. The best resin or combination of resins for a particular product depends a lot on the device’s requirements (i.e. what the device’s function demands of the material). In today’s post, we’ll explain how focusing on three questions can guide OEMs and their contract manufacturing partners towards more optimal material choices for their next medical device product.
Why It’s Critical to Start Designing with the Right Material
Correct material selection early on is critical for two main reasons:
- As this recent article from Plastics Today explains, since each material has its own trade-offs between cost, flexibility, strength, chemical resistance, etc …, a device must be made out of a material well suited for both that device’s intended application and environment.
- It’s costly—and often impractical—to change resins after an injection mold has been fabricated because resins differ in shrinkage rates and corrosiveness.
But how exactly should OEMs pick the right material for their new medical device design? We suggest they ask a few basic questions.
Question 1: What Unmet Need is This Device Satisfying?
There are plenty of niche areas in healthcare waiting for the right device made out of the right material. One polymer which is already filling many such niches is the high-performance thermoplastic polymer PEEK. In addition to being very biocompatible, PEEK can tolerate high temperatures, is stiff (in fact, PEEK’s stiffness is a close match to bone’s), and the polymer is strong enough to be used as a replacement for titanium or stainless steel. These attributes make PEEK a great candidate for medical devices, which need to maintain their high strength even after repeated steam or autoclave sterilization cycles.Question 2: What Performance Demands Does the Design Place on the Material?
Mechanical properties such as rigidity, lubricity, wear resistance, creep, thermal stability, optical characteristics (like transparency or color), electrical resistance and dielectric strength, chemical resistance, and swelling from fluid absorption must meet the demands of the end product.Reusable products, which need to be repeatedly sterilized by multiple methods, must have excellent thermal and chemical resistance. This resistance is why polymers like PSU, PEEK and medical grade PC are good candidates for those applications. Their high melting points also require, however high, melt temperatures and tooling to match. Also, secondary operations that require localized melting like heat staking or ultrasonic welding may not be practical for parts made of these high temperature resins.
On the other hand, diagnostic labware devices that hold tissue, bodily fluids, cultures, or other clinically important substances and are meant for human visual inspection or automated imaging usually require a transparent polymer like medical grade Makrolon (PC). Makrolon is a tough material whose optical clarity can rival that of glass. As an added bonus, Makrolon is also easy to mold, making it well-suited for mass-produced injection molded products.Question 3: What is the Target Cost per Part?
Tooling is paid for once, but an OEM pays raw material costs on every part that’s made. At the end of the day, designing and launching a new medical device is a business decision that an OEM must justify on the basis of revenues exceeding costs. That’s why OEMs must carefully consider the cost of whichever resin their device will be made of, as some resins are a lot more expensive than others.Commodity resins like PS and PP are widely available at low cost and are good choices when high performance, biocompatibility, and the ability to withstand repeated sterilization via chemical agents or heat are not required. Examples of these types of applications include reagent containers, petri dishes, and other disposable products.
When designing a reusable device, or a critical component for an implant, higher material expectations—and higher resin costs—are more appropriate. These higher cost engineering resins include the aforementioned PEEK, UHMWPE, Makrolon, and PSU. Then there are the specialized grades: medical grade, glass-filled, electrically conductive, UV resistant, etc . . .By smartly considering the cost and benefit tradeoffs of the available resins and their grades, medical device OEMs can pick the perfect polymer for their application.
By asking these three questions at the beginning of the design process, OEMs and their molding contract manufacturing partners can develop new high quality medical devices by making smart material choices. As an experienced injection molder focuses on medical devices, we at Crescent Industries have utilized our deep material and tooling engineering knowledge to assist OEMs like you find the right material.