Injection Molding for the Biomedical Industry

The Biomedical field is dedicated to development of technologies, medicines,
therapeutics and tools for treating and managing health conditions. It combines engineering,
biology and medicine into a single field.

Injection molding is one of the technologies borrowed from the plastic and polymer
industry that has played a major role in the manufacturing of biomedical tools and devices.
From petri dishes used for growing tissues to implants used in joint replacements.

This article explores how injection molding is applied in the biomedical industry. We look
at the different applications, the types of injection molding technologies used, the
requirements needed to meet in injection molding for the biomedical industry and more.

Injection Molding and Advancement of the Biomedical Industry

In its earlier years, injection molding simply involved ramming plastic melt into a mold
with a plunger. This process patented by John and Isiah Hyatt in 1872 was good enough to
make items like buttons and combs from celluloid. While the parts suited the intended
application, these had nothing close to the sort of precision and repeatability that the
injection molding today achieves.

The advancements in the biomedical field are linked with the advancements in other
fields. As processes like injection molding became more advanced, researchers,
manufacturers and other stakeholders began to explore further possibilities beyond
manufacturing everyday consumer goods.

While the surgeons had the knowledge of how for example a knee joint could be
repaired by inserting an artificial object, fabricating the object by other means could prove
expensive and time consuming. Besides, the precision required might not be possible using
crude methods. Advancement in injection molding that allowed parts to be made to high
precision significantly contributed to the advancement of the biomedical industry.

Healthcare became more accessible to more people as these parts can be mass
produced and made available as needed while still retaining optimal performance.

Requirements for Molded Parts in Biomedical Applications

From materials handling to packaging of the final product. Injection Molding of
biomedical parts needs to adhere to high industry standards. The process employs
precision engineering with advanced tooling and highly efficient process control systems to
monitor process conditions at every step.

The key requirements for biomedical parts include biocompatibility, clean room / sterility
and durability. Other requirements include precision and accuracy, reproducibility, surface
finish, recyclability, cost effectiveness, and meeting regulatory standards.

Specific applications have their respective requirements. For example biocompatibility
requirements vary for different applications and grades of materials. Some grades may be
approved for short term contact such as tubing and sensors. Other materials may be
approved for longer term contacts that can vary from days to weeks such as tissue scaffolds
and screws while others are approved for permanent implants like bone and knee
replacement.

Since these products, if contaminated, pose risk to human health, injection molding for
biomedical application occurs in clean room environments under stringent control. Every
stage of the production must be controlled such that the final product is free of
contamination. For materials that cannot be sterilized every stage of the process must be
executed in the highest level of clean room environment. The relatively high temperature in
which injection molding occurs further aids in preventing contamination as most pathogens
are killed at the processing temperature of many polymers used in biomedical applications.

Biomedical products are often required to meet regulatory standards such as ISO, EU
MDR and US FDA. This often requires tight monitoring, advanced process control and high
traceability of materials, process and personnel. These certifications require stringent
evaluation of the final product as well as the entire manufacturing process.

Existing and emerging application of injection molded parts in Biomedical Industry

As the plastic industry’s mainstay for manufacturing parts in highly reproducible and cost
effective manner, injection molding has been significant in facilitating the biomedical industry
to develop accessible and effective healthcare systems.

Suture anchors, bone plates, bone screws, housing and leads for implantable devices,
dental implants, parts of instruments, handles, and protective gears, are some of the wide
arrays of biomedical products made using injection molding.

These can be categorized into surgical tools, implantable devices, laboratory
equipment, housings and casings for medical devices and equipment, packaging,
consumables and disposables.

Emerging technologies in application of materials with advanced features such as
conductive polymers and [stimuli responsive
polymers](https://www.sciencedirect.com/science/chapter/edited-volume/abs/pii/B978032388
5249000103) pose new challenges for Injection Molding of biomedical parts.

Polymers used for Biomedical Parts

Diverse polymers are used for different applications in the biomedical industry. The
material selection criteria includes factors such as cost effectiveness, availability,
processibility as well as the specific performance parameters for the intended application.
The table below summarizes some polymers and example applications.

Advanced Injection Molding Technologies and complimentary processes for Biomedical Applications

The standard injection molding process is still widely used in the manufacturing of many
biomedical parts. Some products with simple to moderate geometric complexity and wall
thickness can be effectively produced this way. However some products require more
advanced injection molding technologies to achieve the targeted geometry or performance
parameters.

More advanced injection molding technologies used in biomedical applications include;
insert molding, overmolding or two-shot molding, micro injection molding, gas assisted
injection molding, microcellular Injection molding, and thin wall injection molding. Each of
these processes have been described in [previous
blogs](https://www.cavitymold.com/advanced-processing-of-tpu-from-materials-preparation-t
o-quality-control/) on injection molding

Complimentary processes such as machining and 3D printing are sometimes required.
Where injection molding alone cannot completely achieve the final design or performance,
machining can be added as a postprocessing stage. 3D printing is often used for fast
prototyping at design stage for visualization and/or analysis.

Conclusion

Injection molding has been extensively applied in the biomedical industry. A wide range
of medical grade polymers exist for diverse biomedical applications. Biomedical products
must meet the high standards for regulatory approvals and the tight process control, high
precision and repeatability achievable with injection molding processes further makes this
possible.

Mold design is crucial to achieving efficiency and high productivity. Since the same mold
can be used to produce hundreds to thousands of identical parts, this forms a major capital
investment in biomedical injection molding. So if your project ventures into injection molding
for biomedical parts, collaborating with expert mold designer is a crucial step.