Medical Plastic Data Service Magazine



Our 30th Year of Publication
Page  1 of 1



Why It’s Time to Rethink How You Assemble Plastic Medical Devices and Components

(Courtesy : Emerson Driven by Innovation, Powered by Partnership)


Over the past several decades, there has been a massive shift toward the use of plastics in medical devices, respiratory care systems (oxygen delivery and medical ventilators), kidney dialysis equipment, surgical instruments, personal drug delivery devices like insulin pens, inhalers and, especially recently, in-vitro diagnostic (IVD) testing equipment for big labs, point-of-care (POC) and at-home testing. The COVID-19 pandemic created a surge in demand for personal protective equipment, including masks and respirators.

At the same time, the market as a whole is exploding. A 2021 report from Research and Markets predicts the global medical device market will reach $745 billion by 2030, growing by 5% annually from 2020 to 2030 owing to aging population worldwide, the prevalence of infectious diseases as well as the increasing prevalence of chronic diseases, technological innovation and penetration of healthcare insurance.

However, as production volumes increase, quality requirements become more stringent, and the materials used in devices change, the traditional methods of assembly like gluing, mechanical fasteners, and simple welding techniques like heat-sealing often are no longer adequate.

For Example

Hemodialysis filter housings: Until recently, these cylindrical housings have been made primarily from polycarbonate, an excellent, high-performance plastic, and assembly involved glue and mechanical fasteners. However, the housings also contain a chemical called bisphenol A (BPA) that has been linked to adverse health effects. Consequently, out of an abundance of caution, many dialyzer manufacturers are shifting to polypropylene, a polymer that is nontoxic, tasteless, low density, unaffected by humidity, and relatively inexpensive and easy to process. Unfortunately, its mechanical characteristics make it unsuitable for the glues and screws used with polycarbonate, so manufacturers are turning to ultrasonic and laser welding instead, with excellent results.

Figure 1. Kidney dialysis machines (dialyzers) incorporate a filtering cartridge like this one in lower right. They consist of extremely fine filtration media encased in a plastic hous¬ing. Image courtesy of Emerson.

Respirator flow sensors:

As the name implies, these components measure the flow of oxygen to patients receiving respiratory support. These devices used to be produced in relatively small quantities, and the two molded plastic halves were generally glued to¬gether. Gluing was a slow process, requiring a high level of precision, and rejects were common, but these limitations were accepted until the COVID-19 pandemic and other breathing diseases caused demand for flow sensors — which must be replaced daily — to rise in the millions. To meet this dramati¬cally increased demand and control costs, these flow sensors are increasingly assembled using ultrasonic welding.

Safety syringes:

Single-use syringes have been a ubiquitous element in healthcare, even more so with the millions of COVID-19 vaccine doses being administered. Many nations mandate the use of what are called safety syringes, designed to prevent needlestick injuries and/or reuse. The most common approach has been to include a sheath or hood that is clipped to the syringe so that it can be slid over the needle after use. These clipped-on covers pose a number of manufacturing challenges and units with a spring that automatically retracts the needle into the housing after use have been developed. The spring is retained in the syringe housing by a small plastic ring that is ultrasonically welded to the barrel.

In-vitro diagnostics: The market for IVD devices is growing rapidly in part due to COVID-19 and other infectious disease but also due to the efficiency of being able to diagnose cancers, heart diseases, diabetes and other conditions both in hospital and home settings. Testing devices comprise two clear mating parts that are joined together to form fluid paths. In the past, assembly has been completed us¬ing a costly, time-consuming glue process, but today high-speed laser, together with clear-on-clear laser welding technology enables affordable, repeatable production of high-purity testing articles in the high volumes required in the coming years.

Figure 2. In-vitro diagnostics (IVD) antigen lateral flow test

Surgical instruments:

This is another rapidly expand¬ing application, where gluing and screwing have been used historically. Ultrasonic stud assembly, however, is increasingly preferred because it is rapid and cost effective, and creates a hermetic seal that stands up to sterilization. In addition, by eliminating the need for screws, ultrasonic welding eliminates the tiny recesses where bacteria could accumulate.

Market growth and new application trends — togeth¬er with advancing ultrasonic and laser technology — make it imperative for device manufacturers to re-evaluate how their products are assembled.

The Emerson logo is a trademark and service mark of Emerson Electric Co. Brand logotype are registered trademarks of one of the Emerson family of companies. All other marks are the property of their respective owners.

120 Park Ridge Rd., Brookfield, CT 6804, United States
Phone+1 203 796 0355, Fax+1 203 796 2250

Back | Back to Top  | Previous