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Medical Device Manufacturing: Components Bonding and Joining Techniques

Medical devices whether temporary or permanent, used externally or inside the body, are becoming more complex and more sophisticated both in terms of their performance specification and structural complexity. Medical devices have complex shapes that cannot be molded directly. As a consequence, many devices currently used are multi-component and require methods of assembly in their production.

Many types of medical devices are made of plastics which are required to be joined together in some manner. In these cases, the plastic parts may need to be separately made and joined together. So, Joining and Bonding are critical steps in manufacture of the components from polymers and polymeric composites which are used in manufacturing of Medical Devices.

Medical devices in every aspect of their production demand highest level of quality. Reliability, reproducibility and the assembly of sub components are also critical in manufacturing of Medical products. Non-compatible materials (e.g. Mix-matched polymers) used in the manufacture of medical devices pose difficulties in the assembly process. The bonding and joining technique must not interfere with the function or standards applied to Medical Device.

One of the most prevalent concerns when bonding materials for medical device manufacturing is how to get a strong bond between mismatched substrate surfaces. Generally, when bonding like materials, there are adhesives available that will strongly bond the two surfaces at the interface of the substrates. However, in many medical device manufacturing scenarios, the need to bond different materials with very dissimilar physical and chemical properties frequently arises. For example, a reasonably rigid material such as polycarbonate (PC) may need to be bonded together to a more elastic polyethylene (PE) material. Since the chemical properties of these materials is quite different, they will tend to bond differently to various adhesives. A certain adhesive may bond well to the PC, but not well, if at all, to the PE, and vice versa.

There are methods to chemically treat the surface of one or both of the materials using primers, or other mechanical means to get a strong adhesive bond. While many of these chemical methods work quite well, they require the use of materials that may expose the manufacturer to dangerous or toxic matter. Such materials may also require expensive or time-consuming disposal methods. Most importantly, many toxic or dangerous materials cannot be used in the manufacture of medical devices as they are going to be implanted in the human body.

Nowadays, there are thousands of grades of polymers available at the market for Medical Device Manufacturing. These cover a wide range of properties, from soft to hard, ductile to brittle, and weak to tough. The wide variety of polymers and polymeric composites makes it possible to select and even customize the material to specific application.

As the requirements for the components increase, so do the requirement of joining. Joints in Medical Device Manufacturing are necessary always when; part integration is impossible because of complexity and/or high cost, using different materials in the same component, disassembly is required and repair of damage is needed.

Joining is generally the final step in any fabrication cycle. The effectiveness of joining operation can have a large influence on application of any polymer or composite material used in Medical Device production.

Blood and gas filters, IV spikes, drug delivery systems, surgical tools, diagnostic cassettes, fluidic devices, cardiometry reservoirs, face masks, implantable devices, insulin pumps, surgical gowns, blood donation kits, dialysis tubes, disposable clothing, pump cylinders, blood basins, sensor components, dialysis systems, condiment dispensers and blister packages, are some of the common Medical Products and Components which are using Plastic Joining and Bonding processes in their manufacturing.


The methods for joining plastics and composites can be divided into following major categories: Mechanical Fastening, Adhesive and Solvent Bonding, And Welding.

  1. Mechanical Fastening :

Mechanical fastening has limited applications in Medical Device assembly. Mechanical fastening presumes the use of additional parts such as polymeric screws, bolts and it involves the use of separate fasteners or it relies on integrated design elements such as snap fit or press-fit joints.

Mechanical fastening can be used to join both similar and dissimilar materials.

The one advantage of Mechanical fastening is ease of disassembly. While, Disadvantages include reduced aesthetics, poor hermetic sealing and increased inventory.

  1. Adhesive Bonding And Solvent Bonding :

In Adhesive Bonding, an adhesive is placed between the parts to be bonded where it serves as the material that joins the part and transmits the load through joint. Adhesive bonding involves the use of a polymeric adhesive, which undergoes a chemical or physical reaction, for eventual joint formation.

Adhesive bonding is well regarded in the industry because it does not have the health and safety issues that solvent welding has. In addition, adhesive bonding does not require the high capital equipment costs as do ultrasonic or vibration welding.

No one adhesive technology can fulfill all requirements in bonding disposable medical devices. A balance of adhesive properties is needed to assure successful bonding of medical devices. The types of adhesives commonly used for medical device assembly include cyanoacrylate, lightcurable cyanoacrylate, light-curable acrylics, epoxies, urethanes and dual ultraviolet (UV)/moisture curable silicones.

Many medical devices, including reusable surgical instruments like endoscopes and laparoscopes, are assembled using a variety of biocompatible adhesives. These adhesives must be able to tolerate repeated sterilization cycles that may include steam autoclaving, chemical treatment, and radiation Anaerobic sealants, cyanoacrylates, light-curable acrylics, and silicones are used in diverse lifesaving applications ranging from automotive air-bag sensors to catheters and blood oxygenators.

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