By Hallie Forcinio, writer, Plastics Decorating
The use of plastics in medical applications continues to grow with an overall compound annual growth rate (CAGR) of 5.5%, and some segments like auto-injectors are forecast to reach a 13% CAGR. Driving forces include an aging population, new products and rising demand from developing economies.
“Plastics continue to be the preferred choice in medical devices,” said Keith Ekenseair, president, Pad Printing Technology. Plastics offer a wide range of material options, lower cost versus alternative materials, easy disposability and durability. 1 In addition, he noted, “It’s easy to incorporate decorative design elements and color that is pleasing to the eye.”
Color is particularly significant as it can enhance functionality, according to Len Czuba, president of Czuba Enterprises, Inc., in a presentation at the TopCon and IMDA Symposium (Sept. 16-21, 2021; Edina, Minnesota), hosted by the SPE Decorating & Coatings Division and the In-Mold Decorating Association. Color sends a message, e.g., serves as a size or temperature indicator; enhances appearance; supports brand/product identity; and reflects quality. Color can indicate a product is old (think overripe bananas) or confirm that a sterilization process has been completed. It also can elevate mood and be calming.
A variety of plastics are used for medical applications, and advanced plastics are being developed to address evolving needs. The almost unending array of current applications includes blood bags, tubing, valve connectors, surgical cables, wound dressings, plastic syringes, eyeglass frames, coronary stents, plastic prosthetics, needle housings, catheters, pacemakers, heart valves, eye lenses, prosthetic limbs, surgical gloves, instrument handles, MRI machines and surgical instruments. Many of these devices are injection molded. This process produces colored or transparent precision parts that are tough, lightweight, sterilizable and resistant to bodily or medical fluids. 1
As the use of plastics grows so does the need for plastic decorating technologies. Micah Swett, sales manager at Diversified Printing Technologies, said, “We have definitely seen an increase in the decoration of medical plastics. Catheters are a large part of the medical market that requires decoration. This market seems to be growing, especially in the United States. At-home test kits are on a growth pattern as well.”
Decorating technologies used for medical products include pad printing, screen printing, in-mold decoration, hot stamping and transfer printing. “Some people are exploring laser printing, but it doesn’t offer the contrast most companies seek,” said Chris DeMell, global medical market manager/senior account manager Midwest, IDS, a Division of ITW.
Pad printing seems to be the most widely used decorating technology. “The image quality, repeatability, tolerances and use of irregular shapes and surfaces all contribute to pad printing being the preferred method over other printing applications such as screen printing,” explained Ekenseair.
“Pad printing is very flexible and allows multiple colors,” added DeMell. It also can achieve the tight tolerances (within 0.176 mm/0.0076 in) needed for image placement.
Growth is focused on several areas including larger part sizes (up to 36″ wide), 360-degree decoration and human factor engineering. Ekenseair said, “I am seeing an increase in 360 applications whereby the customers want the artwork/image to go fully around the circumference of their designed part. The pad printing industry has historically perfected this for catheters and syringes. But new product designs by medical customers continue to challenge our industry in 360 applications.”
DeMell is observing growth in decoration beyond standard branding and indication marks. Increasingly, he said, “Decoration is being used for human factor engineering.” These warning signs and instructions make devices easier to use. This information is being incorporated into new devices and also is being added to existing products to increase safety and ease of use for consumers. Another area of activity for pad printing and other decorating technologies is device identification, which enables devices to be traced to their source.
Medical products pose many production and decorating challenges. “In general, medical applications are more stringent,” DeMell said. A clean room environment generally is required, and tolerances on placement, image quality, durability and legibility are tighter than in other industries. Polymers, inks and additives (including colorants) must be medical grade, sterilization-resistant, meet end-user safety requirements and comply with FDA standards for products coming into physical contact with the human body. “Many medical applications require special inks that are safe for the human body,” Swett said, noting Class VI inks meet this qualification.
Meeting medical-grade requirements requires extensive toxicology and extractables/leachables testing of polymers, additives and inks to ensure no deleterious substances will migrate from the device, contaminate the product and cause harm to the user. These tests are costly and time-consuming and can require years to complete. If any input changes, retesting is required. “That’s why once an ink is spec’d, it’s difficult to change it,” DeMell said.
Colorants must be carefully selected and tested. Colorants with heavy metals content must be avoided, especially for Class III implantable medical devices, Czuba told the audience at TopCon. To avoid delays in product introductions and added costs, he recommends testing a colorant to determine its physical, functional, chemical and biological (ISO 10993) attributes.
Other challenges involve ink adhesion. Achieving proper ink adhesion often requires extensive trial-and-error testing. For one customer’s selected plastic substrate, Pad Printing Technology completed 42 different tests to examine different inks and additives along with multiple pre- and post-treatment processes. “At the end, only one combination worked,” Ekenseair said.
Finally, interest in recycled content and the effort to eliminate single-use products and move toward a circular economy continues to expand. However, medical device makers are proceeding with caution in adopting such strategies due to safety concerns. A multiple-use product that isn’t sterilized properly between uses can pose life-threatening hazards to the patient, explained Czuba. Recyclate also tends to be more variable, making parts less consistent. However, he says, devices can be recycled into non-invasive products.
This market seeks equipment with higher speeds and precision. As the market grows, so does the use of automation, particularly for high-volume runs, which offset the cost of tooling, fixtures and changeover more quickly. So, automation technologies such as machine vision inspection and robots or cobots (collaborative robots), play a growing role in the production of medical products. Since production numbers can change quickly depending on market demand, “Scalable automation is key,” Swett explained. He predicts, “Cobots are a big part of the future in medical automation.
Czuba agreed, “With their flexibility and quick implementation, robots are a great tool for this market.” Another advantage of robotic systems is the elimination of people from the clean room. As long as the robot starts out clean, it stays clean, whereas gloved human operators can transfer contamination from anything they touch.
In addition, robots can streamline the production process by taking parts out of the molding machine and orienting them for immediate assembly, thereby eliminating the need to pick a part from a bin and then orient it for assembly.
“It’s a significant savings in time and money to have the part oriented to begin with. These days most molders offer clean room molding and assembly as a value-added service,” Czuba said. Orienting and assembling parts directly from the molding machine take advantage of the fact that parts exiting the molder are clean and sterile, thereby eliminating the need to wash, clean and dry parts before assembly.
Proto Plastics, “6 Benefits of Plastics in the Medical Field,” Blog, Nov. 30, 2020, https://protoplastics.com/plastics-benefits-medical-devices/, accessed April 7, 2023.