PrintHow are conductive elastomers and plastics used in wearable devices to maintain electrical contacts while allowing flexibility?
In a 1 hour LinkedIn Live, Jeff Dirkx, Program Manager at Accumold, and I took questions on the intricacies of selecting the right materials and design strategies to achieve the desired product performance, especially in medical devices.
Conductive Elastomers in Micro Molding
The emerging use of conductive elastomers in wearable devices is significant. Dirkx emphasized these materials are gaining traction due to their flexibility and conductivity, making them particularly useful for creating contacts within devices that need to maintain electrical connections despite movement. “The conductive plastics—and probably more interesting—are the conductive elastomers that have some flex to them, especially for contacts. [It’s] really interesting.”
These elastomers allow for the seamless integration of electrical pathways within the molded components, reducing the need for traditional wiring and enabling more compact and flexible device designs. Dirkx mentioned that while various materials can be used to achieve conductivity—ranging from nickel to carbon fibers—the challenge lies in balancing conductivity with material properties like durometer, which affects the elastomer’s flexibility.
The technical challenge of balancing the elastomer’s durometer, or hardness, with its conductive properties is crucial for ensuring that the elastomer remains flexible enough to conform to the device’s shape while still maintaining a low resistance path for electrical signals.
While high-end conductive materials like silver beads offer superior conductivity, their cost often makes them impractical for large-scale production. Instead, Dirkx directs customers on fine-tuning the composition of these elastomers, optimizing the amount and type of conductive filler to meet specific application needs. This approach allows for the creation of wearable devices that are not only low-profile but also capable of integrating electrical functions directly into their structure, eliminating the need for bulkier, more rigid components.
Challenges in Overmolding and Sealing
Another significant topic was the difficulty of overmolding components, especially when dealing with plated parts like gold, which do not easily bond with other materials. Dirkx pointed out the necessity of using mechanical features or specialized elastomers to create effective seals and ensure the durability of the final product. “If we have an exposed gold surface in the electronics—or in the inside—getting that to seal is pretty difficult.” Dirkx said, “So that’s where we come in with our elastomers, and overmolding the ribs and such, into the component before it’s assembled.” Using elastomers in this way creates a mechanical seal.
This aspect of the discussion was particularly relevant for manufacturers dealing with electronic components, where maintaining a seal against moisture and other environmental factors is critical. Dirkx also discussed the use of ultrasonic and laser welding as effective methods for assembling these intricate components, emphasizing the importance of precise design in ensuring successful welds.