Automated gluing, casting for medical devices

Features - Adhesives

Closing the gaps within partially automated processes.

ViscoTec’s preeflow eco-PEN for catheter bonding.

One hurdle for medical devices is that they can only come to market once they have complied with all regulatory standards and then, at best, be manufactured automatically, since manual handling is cost intensive.

Best practices are for companies to holistically embed medical device manufacturing processes and systems, accounting for the entire value chain from delivery of raw materials and parts to assembly and finished device delivery.

Adhesive joint advantages

Adhesive bonding technology has become a popular joining method for medical device assembly, a trend that could gradually replace laser welding. The electronics and automotive industries were the pioneers as they recognized the advantages of bonding, and medical technology has now followed suit.

Special attention must be paid to assembly of medical devices because of high regulatory requirements and because the processes often take place in clean room conditions. Bonding benefits include:

  • Thermal load on the joining materials is low or non-existent; preferred materials are UV adhesives or cyanoacrylates; thermally curing adhesives can be used in special cases
  • Surface, microstructure of components being joined remain unchanged during bonding
  • Adhesive bonds can have sealing properties; assembly processes can be streamlined; costs reduced
  • An entire spectrum of component sizes can be bonded
  • Active alignment enables component repositioning during assembly; only UV light hardens the adhesive
Preeflow eco-PEN and eco-DUO dispensers for application of fluids and pastes in the µL range.

Adhesive dispensers

Purely volumetric dispensers, such as ViscoTec and preeflow, allow continuous and pulsation-free dosing to automate joining. The process is gentle and low shear with all materials, regardless of the viscosity of the adhesives being processed.

This is particularly important for medical devices used in the body, which require smooth and sterile surfaces, the bases of which are superimposed over the bonding and subsequent sterilization. The volumetric dosing unit can reverse its conveying direction, allowing precise adhesive thread breakage. In addition to the exact thread breakage, it prevents material from dripping.

The ability of preeflow systems to convey and apply adhesive with ±1% accuracy in the microliter range allows bonding of tiny, difficult-to-assemble medical devices. Without tearing, the smallest amounts of adhesive are applied to the tubes and provide pinpoint accuracy throughout the entire production cycle. The delivery rate can be changed if required by a specific component of the catheter such as balloon, cuffs, or connectors. Systems are usable for automated, semi-automated, and manual processes with one dosing technology. The dispenser is designed for all areas of application.

In fully or partially automated processes, the dispenser can be connected to the higher-level control system via a controller (foot switch). The operators have both hands free, making work more efficient and the process more secure.

“The focus of industrial manufacturers was and still is on precision and the shortest possible cycle times. This know-how was incorporated in the development of dosing solutions for medical devices,” says Annemarie Brandstetter, medical technology engineer and deputy head of the Hygienic Solutions department at ViscoTec.

The corresponding regulatory framework conditions that medical device manufacturing requires was supplemented so manufacturers could have dosing technologies developed and certified specifically for their needs and products.

A U.S. FDA compliant ViscoTec Pharma Dispenser VPHD in Hygienic Design.
The full ViscoTec system.

Sterilization after bonding

In addition to sealing, the right adhesive must allow for sterilization after bonding and must be safe for human use. Finally, the adhesive must be suitable for a fully automated process.

An alternative to bonding is component micro-encapsulation. It insulates and protects components from temperature fluctuations and ensures long-term stability during permanent or selective use in the human body. Whether microencapsulation or bonding, the combination of dosing technology and official approval of the elastomers used forms the basis for reliably serving the medical device market of the future.

Ultimately, when developing new adhesives and application technologies, component qualification and process validation are important. This begins with fluid management and emptying the container in which an adhesive is delivered, including degassing and the technical system for application. With the knowledge of these basic conditions, medical device manufacturers can automate dosing, bonding, and micro-casting, closing a gap in many places from partially automated to fully automated production processes while considering national and global specifications by the relevant authorities.