Rubber in medical: A marriage of material, design, process and cost

AKRON—Health care provides the kind of demand for rubber that keeps on giving.

And to meet the innovations that go along with this continuous uptick, choosing the correct material for the correct device is sometimes optional, more often unique and always critical.

"Health care is the fastest-growing industry, and every application is critical," said Amalendu Sarkar, vice president of materials technology for Cirtec Medical, a developer and manufacturer of medical components based in Brooklyn Park, Minn. "And choosing the right elastomer is not only important, it is extremely critical as well.

"With the future growth of the industry directly related to the aging population, the criteria for the right elastomer is important."

Such options include polyisoprene rubber or silicone, and then within silicone, HCR or LSR.

"We live in a constantly evolving world," Sarkar told the audience during his May 9 keynote address, kicking off the second day of the Healthcare Elastomers Conference organized by Rubber News. "Khaled (Boqaileh, CEO of LabsCubed) mentioned this yesterday with AI—and health care plays a significant role in the quality of human capital."

By mid-century, Sarkar said, the U.S. will have undergone a seismic change, as 80 million people will be at least 80 years or older.

And personal care for those 85 and older are predicted to increase four times by 2040. Sarkar cited data that forecast there will be about 2.1 billion people across the globe who are 60 years and older by 2050.

"If we don't start now (in planning for medical device demand) we won't be able to catch up with this growth," Sarkar said. "This is a staggering trend that demands our attention."

The U.S. is predicted to double the average of all advanced countries in its health consumption as a measure of per capita spending.

And this is where AI can assist, Sarkar said.

"AI-powered robots are already used in hospitals to assist patients. ... The bottom line is there is tremendous growth potential in the health care industry in the near future," he said.

Because material selection is in the beginning of the medical component development process, the step demands accuracy.

The early accuracy in material selection forms the processing and performance characteristics later.

But the process is not always in agreement.

"Material selection is a key process in the design of medical devices," Sarkar said. "We need to understand this thoroughly."

Defining the application requirements are critical during this step.

"They must be clearly defined, otherwise the end will be incorrect," Sarkar said. "Is biocompatability a requirement? Is it a single-use, select material that meets required performance standards for its intended use?"

Other considerations, among a dizzying array of process development hurdles, include the conditions under which the component will be tasked with operating.

"Is is static? Dynamic? Is the device going to be under any sort of pressure? The component must allow for these tolerances," Sarkar said.

Raw materials commonly used in the medical device realm include organic rubber, such as isoprene, EPDM, nitrile, butyl, halobutyl, SBR, NR, polychloroprene (neoprene) and polyurethane rubbers.

Common inorganic rubbers for use in the medical world include HCR and LSRs, the high-demand silicone group.

"Silicone is prized for its biocompatability," Sarkar said. "The other synthetic organic elastomers are mostly used in non-critical devices."

Clean manufacturing and traceability are just a couple of the select demands placed on medical elastomers, as well as the choice of sterilization technique.

The lowest bar to meet in classes of medical instruments include Class I devices, such as surgical instruments, flex bandages and respiratory aids, while Class II products include infusion pumps and wheelchairs.

Class III products are the most stringent, comprising wearables, under-the-skin devices and devices that exist in the body but are attached to an outside source.

"Making the right material selection can make more effective devices," Sarkar said. "But the cost of testing can be so high that they are not sustainable long term."

OEMs in the health care world count the design phase as one of the most important steps, though they can reach limitations quickly if the material and process are not compatible.

So a customer might then decide to retrace their steps, as the puzzle—with an end-use product that presumably will save lives—must be solved.

"We look at things like media contact—does it come into contact with blood—as well as aesthetics, sterilization methods and cleaning—how many cycles can it be exposed to with cleaning agents?" Sarkar said.

Additional design considerations include regulatory approvals (for its functional requirements), environmental factors (such as humidity and temperature) and coatings (plasma-treated or siliconized).

Finally, collaboration is necessary so that teams can come up with solid plans, Sarkar said.

"Material selection is a critical aspect, as is design, for which a thorough understanding of end-application requirements is necessary," he said. "Collaboration between teams is essential in all phases.

"And testing and analysis are required for the final selection. The chosen material (and design) should meet the required biocompatability standards."

Sarkar likes to see the excitement in younger generations at Cirtec as they work through problems, and he offered praise for the value of the Healthcare Elastomers Conference.

"The more we share our thoughts in a platform like this the better we will be long term," he said.

The cost of failure is important to consider, just as the cost of success—the money put into an iteration that succeeds to market—is important to consider, Sarkar said.

"The guidelines for elastomer material selection is meant to shorten the selection process," he said. "Ensuring biocompatability and testing can be expensive in many cases. But cost should not be the only consideration in material selection."

When considering HCR or LSR for a component, both are silicones, and both are biocompatible with excellent temperature ranges, resistance to ozone and UV light and outstanding aging properties.

"There are pros and cons to both," Sarkar said. "And there are advantages and disadvantages."

Factors affecting molding cost can vary as well, including overhead costs, scrap costs, material costs and profitability. Precision-molded components, for instance, can act as flow control for liquids, but some valves only allow fluid flow in one direction.

Every customer that comes to Cirtec Medical can arrive there at a different point in the development process. While some might have a material in mind, others hand the entire developmental timeline over to Cirtec. And the earlier a customer can get to a vertically integrated company like Cirtec, the better the outcome.

"Different customers have different types of challenges," Sarkar said. "Some have their own materials or their own expert compounder, so they start at different points on the supply chain."

Often a Cirtec expert like Sarkar, who has three decades of experience of material development for the medical and automotive industries, has to educate a customer to see if the material they have in mind has processability.

"Some materials can be good property-wise, but are not good process-wise," Sarkar said. "Sometimes (customers) don't know this because they do not know the entire process. They come with one idea, but they need to know what will work."

Sarkar added that some items—depending on the class and thresholds required—are getting to market more quickly as the ease of 3D printing systems become more prominent. And having the proper tooling in a vertically integrated business is invaluable.

"Doing our own tooling in-house really helps," Sarkar said.

On average, he said, a medical component can take anywhere between six months and three years to come to market.

"Sometimes a customer can be reluctant to switch to an alternative material to move the process along," Sarkar said. "They are hesitant, because it can be a very expensive process. It is very important to make sure the material is sustainable.

"You have to look at cost—which is a driving force —but you have to look at the cost of failure as well."