PEEK Micro Moulding for Medical Implants at Micro Systems

PEEK is widely acknowledged as a high-performance thermoplastic engineering material with exceptional advantages in its properties for a wide range of applications, especially in the medical field for bio-compatible applications. Over the years, Micro Systems have been involved in a number of medical PEEK projects, bringing concepts to life for a range of companies from start-ups to global medical OEM’s

What is PEEK?

PEEK, polyether ether ketone, is a colourless organic thermoplastic polymer belonging to the polyaryletherketone (PAEK). PEEK is a semicrystalline thermoplastic that retains its high-temperature mechanical and chemical resistant qualities very well. Due to its remarkable qualities and biocompatibility, medical grade PEEK is a high-performance thermoplastic that is becoming more and more popular in the medical sector, especially for implant applications like orthopaedic implants, dental implants and spinal implants.

PEEK implant of 50 micron wall section, manufactured at Micro Systems, as an electrode housing for a pacemaker.
The advantages of medical grade PEEK

PEEK is one of the few high-performance polymers that are bio-compatible, along with its exceptional mechanical, thermal, and chemical characteristics, making it ideal for medical applications since it is extremely radiation resistant and simple to sterilise.

Biocompatibility: Due to its biocompatibility and status as a validated biomaterial, PEEK is considered safe for use in in vivo applications. PEEK has no cytotoxic, genotoxic, or immunogenetic effects. For more than 20 years, the material has been effectively used, and it can be suitable for long-term applications, with a markedly lower implant rejection rate.

Modulus of elasticity like bone: PEEK shares various characteristics with bones, whilst being lighter and cheaper to process compared to metals such as titanium and steel, and other metal biomaterials. It bends and supports weight in a way that is considerably more similar to bone, hence minimising stress shielding and encouraging the growth of bone. PEEK implants also support weight similarly to that of natural bone and don’t reduce the density of nearby bone and tissues.

Radiolucency: PEEK’s pure radiolucency makes it simple for surgical teams to monitor the location of implants and spot issues on X-rays, CT, and MRI scans. PEEK’s radiolucency is highly helpful since it won’t affect a doctor’s ability to judge a procedure’s initial success and later healing and recovery, and it is also much simpler for doctors to identify and diagnose any postoperative issues on CT, MRI, and X-ray scans.

Lower infection risk: When processed effectively, PEEK can be moulded with minimal surface roughness, which, combined with its’ natural hydrophobic properties, prevents bacterial adherence and infection risk, hence minimising post-procedure infection, which is considered to be one of the most serious complications from implanted medical devices.

Other advantages of PEEK to be used for medical purposes include high strength and stiffness, high heat resistance, lightweight, good chemical resistance and outstanding wear and abrasion resistance. The high mechanical endurance of PEEK with a high fatigue limit and fracture toughness can extend the service lifetimes, which postpone or prevent the need for further surgery.

PEEK bone implants manufactured at Micro Systems to replace titanium implants.
Micro Moulding for PEEK medical implants

Micro moulding is a precise technique that creates parts of tight tolerance, extremely small size and precision. With its advantages in costing, precision, durability and sterilisation, micro moulding is a preferred technique for small medical component production. However, with several challenges in moulding PEEK material, only select micro moulders with extensive experience in micro moulding could take on PEEK projects for medical purposes.

The material characteristics of PEEK are affected by varying cooling rates during injection moulding processes, and the length of time and temperature at which the heat treatment is applied directly affects the PEEK polymers’ crystallinity and, therefore, their mechanical characteristics. Stabilising all pertinent process parameters like temperature control, injection pressure and moisture during micromoulding is crucial to achieving only high-quality components for medical implants throughout an extended manufacturing period.

ISO Class 7 cleanroom facilities with the latest Micro Moulding machines, supported by top-of-the-range Metrology equipment, all manufactured in the UK.

It is possible to solve some of the PEEK moulding process’s issues at the mould design phase. Controlling temperature and preventing thermal expansion are difficult due to the high mould temperature needed to attain crystallinity. Achieving dynamic thermal stability as soon as feasible is the aim. PEEK micro mould designers also need to carefully consider and balance many other factors in the design of their micro moulds. In micro moulding, it is not only the weight and the small size of the final products, but also extreme precision and tolerance of the micro moulds that make it challenging for standard injection moulders. Depending on the PEEK grade and flow length, it is possible to achieve micro components made of PEEK with wall thickness less than 50 µm.

For registration in the US or Europe, medical devices that are intended to come into prolonged contact with bodily tissues must fulfil extremely strict quality standards. Extreme cleanliness during the micro moulding process is required. It is vital to follow strict protocols to eliminate any chance of contamination risks. For example, at Micro Systems, all PEEK micro moulding production is carried out in an ISO Class 7 cleanroom with strict specifications and manufacturing procedures to ensure our PEEK products meet strict global medical requirements.

Over the years Micro Systems have been involved in a number of medical PEEK projects, bringing concepts to life for a range of companies from start-ups to global medical OEM’s. Using PEEK for applications such as orthopaedic screws or bone anchors has allowed Micro Systems to provide efficient mass-production with significant cost savings over traditional titanium-machined components.

Micro Systems has the extensive expertise and capabilities in ultra-precision mould design and manufacture, and injection moulding from prototype to mass production.

PEEK is an expensive material with significant benefits for applications in the medical sector, however, its complexity requires a high level of knowledge during the micro injection moulding process. In order to ensure a successful PEEK medical implant project with maximum efficiency in time and cost, it is crucial to involve an experienced micro injection moulder as early as possible, to assist every step of the way from design for manufacturability (DFM) through to mass production. With more than 20 years of experience in ultra-precision mould manufacture and micro injection moulding, Micro Systems is your unique PEEK medical implant partner, supporting you from DFM design, mould design to
prototype and mass production.

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