What AM technology is considered capable of today and how it can be applied in many areas of application is shown (representative) by this expert’s view of medical technology.

Status and Perspectives for Human Medicine

Anlagen für die Additive Fertigung

Anlagen Additive Fertigung / 3D-Druck, Kunststoff

Additive Fertigung

Medizintechnik

Anlagen Additive Fertigung / 3D-Druck, Metall

Werkstoffe für additive Verfahren

Andere Werkstoffe

Medical Applications of Additive Manufacturing

Arburg Plastic Freeforming is predestined for the additive manufacturing of medtech components. The associated Freeformer-type additive manufacturing systems process the same plastic pellets that are used in injection molding. That makes the open systems very economical to use.

Medical Product Manufacturers Are Processing Original Materials Using the Freeformer

Anlagen Additive Fertigung / 3D-Druck, andere

Biokunststoffe

Kunststoff Werkstoffe

Medizinprodukte

Arburg Kunststoff Freiformen

Verfahren für die additive Fertigung

Freiraumverfahren

New Possibilities for Use  in the Human Body

In order to minimize the development time for new products, Geberit International AG manufactures many prototypes using 3D printing. Since 2016, the Swiss company uses a Sintratec S1 for design optimization and material testing in its prototyping laboratory. A visit to Switzerland.

Geberit: „Selective Laser Sintering Really Sparks our Imagination“

Anlagen Selektives Lasersintern, Kunststoff

Rapid Prototyping

Sanitary Prototypes with  High Requirements

With K 2016 in Düsseldorf, Germany, and formnext in Frankfurt/Main, Germany, professionals with an interest in additive manufacturing had two opportunities last year to gain a sense of the spirit of innovation in the industry. One issue was particularly prominent: the increase in production efficiency. This improves the economy of using the different 3D printing processes. 

A Diversity of Suppliers and Physical Cross-Linking Make Possible New Business Models and Application Scenarios for Additive Manufacturing  

Steuern, Regeln

Rapid Manufacturing

Selektives Laserschmelzen von Kunststoff, Metall, Keramik

Selektives Lasersintern von Kunststoff, Metall, Keramik

Faserverarbeitung

Spritzgießwerkzeuge

Industrieroboter

Qualitätssicherung

All Elements at a Glance 

Is there a quantum leap on the horizon for 3D printing? The prototype of a newly developed 3D printer is able to process commercial pellets – also those of high-performance plastics such as PEEK, PPS, PSU, PA and PC, with or without fibers. The machine applies the usual strand-deposition process, though with a simply designed print head that includes a radial screw. 

A Novel Type of Print Head Gives Fresh Impetus to the FDM Branch 

Polysulfone / Polysulfide

Kohlenstofffasern / -matten

Faser- und Filamentextrusion

3D-Print with Affordable Pellets 

Much as when injection molding materials were being developed 30 years ago, the current trend in additive production is toward higher melting materials and materials with improved mechanical properties. The latter can be achieved, for example, by fiber embedding. In machine technology, the developments are increasingly aimed at adapting processing times, sensor systems, and quality monitoring to the demands of high-tech companies.  

Materials Manufacturers and Process Developers Face Growing Demands in 3D Printing  

Rapid Tooling

Pulver-Spritzgießen

Schleifen, Polieren

Additive Adolescence 

Besides compounds modified for special applications and lightweight components, sustainable materials are also becoming an increasingly important focus. In the additives sector, too, recyclates, the circular economy, and reprocessing are now playing a key role.

Not only Polymers but also Additives and Masterbatches Must Be Sustainable

Zubehör / Hilfsmittel Wärmebehandlung

Wärmebehandlung

Compound

Thermoplaste

PVC-Additive

Masterbatches

Additive

Vernetzungsmittel

Farbstoffe und Pigmente

Compoundeure

Dienstleistungen

Handel

PVC-weich (Compounds)

Farbkonzentrate (Batches)

Farbstoffe

Verarbeitungshilfsmittel, allgemein

Flammhemmende Mittel, allgemein

Betriebsausrüstung / Betriebsmittel

Verarbeitungshilfmittel

Filamente für additive Verfahren

Flammschutzmittel

Gleitmittel für Kunststoff

Attention to Detail

New developments by the raw material producers are responding to current application trends. Requirements are changing due to the advent of networked and semi-automated electric vehicles and the different mobility infrastructure. Products for digitalization and energy and resource efficiency are also moving center stage.

New Mobility Forms and Digitalization Are Shaping the Development of Engineering and High-Performance Plastics

Polyetherketon

Polyacrylate

Oberflächenbeschichtung

Holz

Hybridwerkstoffe

Polyacetale

Verbundwerkstoffe / Werkstoffverbunde

Polyamide

Oberflächentechnik

Oberflächenveredelung

Lohnfertigung

Polycarbonat

Technology Made Easy

Additive manufacturing processes count as future-oriented manufacturing techniques. Numerous studies and award-winning demonstrators underline the interest of the industry.

Plastic-Metal Hybrid Cuts Costs and Time in Additive Manufacturing

Bleche, Bänder

Metall Werkstoffe

Verbindungstechnik, hybride

Verbindungstechnik Verfahren

3D Printing with Pellet Extruded Plastics on Metal

Ineos Styrolution announced first results of the PolySLS project, which is focused on developing a new energy saving styrenics based material for additive manufacturing, otherwise known as „3D printing“.

Technik Trend

kunststoffe-international.com

Polystyrol

Kunststoff-Erzeugung

Energy Savings with Styrenics Polymer Tailored for 3D Printing

A machine manufacturer is expanding its wide program of cast and blown film lines with a system for water-quenched blown film extrusion. This provides a unique system portfolio for the production of flexible packaging. The article presents these extrusion processes, their specific characteristics and the resulting application areas. 

Blasfolienextrusion

Kunststoff-Verpackungsmaschine

Flachfolien- und Plattenextrusion

Folien

Film Production: System Options for Wafer-Thin Protection 

Utmost cleanliness and maximum precision – this combination is absolutely crucial especially in medical engineering and is achieved with all-electric injection molding machines mainly. Some newly developed technology modules open up marginal areas for all-electric standard machines in terms of applications and create addition potentials in regard to precision and process consistency. 

Spritzgießmaschinen

Precision Injection Molding: The Steepness of Acceleration 

At the Institute of Medical and Polymer Engineering of Technische Universität München, the ongrowth behavior of human fibroblasts on polymer surfaces was investigated in relation to structures with different aspect ratios, a surface treatment with atmospheric plasma and a coating with titania (titanium dioxide). 

Surface Technology: Influence on the Ongrowth Behavior of Tissue Cells 

As in other sectors ever higher throughputs and shorter cycle times are being demanded in medical technology as well. However, existing fast cycling solutions, for example from the packaging industry, cannot be easily implemented in cleanroom applications. At present therefore injection molding machine manufacturers are working intensively on further developing all-electric machine ranges for high performance use in controlled manufacturing environments. 

Spritzgießen

Reinraumsysteme / -technik

Fast Cycling: High Performance in Cleanrooms 

Industrial sterilization of a plastic for disposable medical applications in accordance with scientific criteria usually requires a costly, separate production step. Given the temperature and pressure conditions that obtain in the injection molding process, auto-sterile manufacturing of medical devices would be very efficient. New research results relating to validation of direct sterilization of the injection molding process are now available. 

Medical Technology: Auto-Sterility of Polymer Melts 

New Ways for Production of Plastic Implants by 3D Printing

In no other field the possibilities and advantages of 3D printing are more pronounced than for medical devices. With the right high-performance materials, complex patient-customized implants can be produced that medical doctors are using to push the boundaries of the possible – for the benefit of patients.

It is said that those who know metals choose plastics. The dictum originated in mechanical engineering, where engineers meant that plastics often offer a more convincing alternative to metals. This paradigm change is now also emerging in medical field: innovative specialty materials and new technical possibilities in additive manufacturing are taking high-performance polymers to new heights.

Polymers have a long tradition in implants: ultra-crosslinked polyethylene is routinely used in artificial knees and hips as a tribological partner with metal or ceramics. The high-performance polymer PEEK (polyether ether ketone) has been supplementing titanium as a material for implants since the 1980s. Bioresorbable polylactide-based polymers have been used for more than 30 years in orthopedics as they are degraded naturally by the body, leaving no foreign matter behind.

Until today some challenges in production have been unresolved: standard processes are injection molding and – particularly for patient-specific implants – milling from semi-finished products, in which material losses of up to 80 % may occur.

Additive manufacturing now opens new ways for individualized production. And for implants the advantages are more pronounced than in any other area. A customized product can be produced for every individual patient. The breakthrough for additive manufacturing of plastics is now imminent, with three aspects coming in place:

<ul><li>Suitable materials of assured quality and with the corresponding documentation are available for use as implants.</li><li>Printing technology has improved to the point that high-quality parts can be reliably produced.</li><li>Appropriate for processes for production are set up in line with the quality management standards in the medical sector.</li></ul>

Now, since for the first time the boundary conditions are fulfilled, an alliance between raw material producers, printer manufacturers and medical device companies can bring this technology to a break through.

Evonik is one of the first companies in the world to offer 3D-printable medical-grade filaments for long-term implants. These consist either of the high-performance polymer PEEK, offered under the brand name Vestakeep, or of resorbable polymers of the Resomer brand family, which may contain polylactide as a constituent.

In order to materialize the potential of 3D printing in the medical field the collaboration of all players in the value chain is essential. Over the last few years, for example, Evonik has been working in conjunction with various printer manufacturers, who have succeeded in further improving their equipment for Fused Filament Fabrication (FFF).

An important finding from this collaboration is that printing strategy decisively affects the result (Title figure). Moreover, the bond strength between the individual print layers is crucial to the performance of the implant. This means that users will obtain good results from 3D printing only if producers of materials and equipment work closely together and share information.

Routine clinical practice must also be taken into account, as a collaboration between Evonik and Meditool illustrates. The Shanghai-based company, in which Evonik’s venture capital unit has made a direct investment, uses data from imaging techniques such as computer tomography to print PEEK implants. Its founding team has many years of experience in both medicine and industry; as a result, the joint development work can directly take into consideration requirements in the operating room as well as current academic and clinical research.

In Europe Evonik is collaborating closely with companies such as Apium Additive Technologies GmbH in Karlsruhe, Germany, and Kumovis GmbH in Munich, Germany. In addition to working in the area of implants, Apium is focusing on a possible application of additive manufacturing in dental medicine. Both companies offer dedicated printers for medical technology. Kumovis has developed a novel temperature and cleanliness management system that significantly improves the quality of 3D-printed components particularly in the area of high-performance plastics [1].

In conjunction with its partners, Evonik has been able to show that parts produced by additive manufacturing can now attain equal mechanical values with those of injection molded parts. A thorough understanding of the printing process and the specific features of the part to be printed is necessary to optimally exploit the diverse parameters of 3D printing. Customer feedback also indicates that – apart from the excellent printability – the interlayer bond strength is better for Vestakeep than for other PEEK polymers. Although PEEK is often regarded as a very rigid material, amazingly flexible structures can be produced by 3D printing, such as meshes that may open up new applications, for example in the cardiovascular area (Fig. 1).

In developing Resomer, Evonik has taken care to design the portfolio of bioresorbable molecules to be as versatile as possible. Polylactide (PLA), poly(lactide-co-glycolide) (PLGA), polycaprolactone, and polydioxanone serve as starting materials. In vivo resorption times ranging from a few months to many years can be attained this way. The filament portfolio also includes materials with the mechanical strength necessary for orthopedic applications such as PLA and PLGA (see Fig. 2 for a sample implant) as well as flexible plastics (such as polydioxanone and polycaprolactone) that can be used in regenerative medicine and as soft-tissue substitutes. An overview of the filaments available is given in Table 1.

3D-printed Resomer tensile bars hardly differ in their mechanical properties from their injection molded counterparts. Figure 3 shows some sample results and Figure 4 scanning electron micrographs of the surface. The properties depend decisively on the printing strategy and the equipment used. With a suitable choice of parameters, 3D printed parts achieve strengths similar to conventionally produced parts. Only in February 2020 Evonik launched PrintPowder, a bioresorbable Resomer that is the world’s first powder specifically for SLS (selective laser sintering) to be produced commercially under GMP conditions. This allows laser sintering systems to be used for the first time to produce complex bioresorbable implants for clinical use with precisely tuned mechanical properties.

Additive manufacturing, with its unique possibilities, supplements current conventional production methods. It consumes less material and opens the door to entirely new design possibilities that would not be accessible otherwise. This is evident, for example, in Evonik’s collaboration with the US company FossiLabs, which has developed special software to allow printing of specific porous structures. This produces 3D-printed implants (Fig. 5) on which bone tissue can grow and that therefore accelerate the growth of bone tissue into the implant after surgery, as is desired for example with intervertebral disk replacements in spine surgery or joint replacements.

Research Confirms Advantages of 3D-Printed Implants

An interesting phenomenon has been observed by researchers at the University of Basel, Switzerland [2]. In in vitro tests on parts printed by the FFF technique, it was found that bone-forming cells (osteoblasts) grew significantly better on the natural, rough surface after printing: after only five days, cellular activity on the printed parts was twice as high as on polished parts and three times higher than on sandblasted parts. This suggests that the healing process in the body can be accelerated by selectively modifying the surface properties of implants.

With resorbable materials, biocompatibility presents particular challenges for the 3D printing process because any embedded foreign particles would be released during the degradation of the material in the body. Work done jointly with the University of Hanover, Germany [3] shows that printed Resomer filaments are not cytotoxic and promote cell adhesion to the surface (Fig. 6).

Entirely new possibilities arise in 3D printing by combining different materials, for example by teaming Vestakeep, a permanent material with good mechanical properties, with the naturally bioresorbable Resomer (Fig. 7). Collaboration between raw material producers and printer producers and medical device companies is key here. 3D-printed polymer-based implants are already at the verge of clinical use. The CAMed (Clinical Additive Manufacturing for Medical Applications) research project coordinated by the Medizinische Universität Graz, Austria, in which Evonik is also participating, is preparing the world’s first clinical study in Austria for insertion of 3D-printed PEEK implants in humans. The project, which is being funded until October 2022, is thus an important step on the path to routine use of patient-customized implants produced by additive manufacturing.

1 M. Haerst, St. Leonhardt, L. Strauss, M. Eblenkamp: Hot Printer – dividualized Implants Made from High Performance Polymers via Additive Manufacturing. Kunststoffe internationl 04/2018, pp. 28–31

2 X. Han et al.: An in vitro study of osteoplast response on fused-filemant fabrication 3D printed PEEK for dental and cranio-maxillofacial implants, J. Clin. Med. 2019, 8, 771; DOI: 10.3390/jcm8060771

3 L. Raddatz et al.: Comparison of different three dimensional-printed resorbable materials: In vitro biocompatibility, In vitro degradation rate, and cell differentiation support, J. Biomater Appl. 2018, 33(2), 281–294 DOI: 10.1177/0885328218787219

Evonik Resource Efficiency GmbH  

www.evonik.com

Evonik Nutrition & Care GmbH  

Ausgabenartikel

Sample implants of Vestakeep filaments, printed with a 3D printer from the Chinese startup Meditool

Fig. 1. Flexible lattice structure of Vestakeep, printed with a 3D printer from Apium Additive Technologies

Fig. 2. Sample implant of Resomer filament

Fig. 3. Mechanical properties of printed and injection-molded Resomer materials

Fig. 4. Scanning electron micrograph of printed Resomer filaments based on polycaprolactone

Fig. 5. Microporous structures in a 3D-printed workpiece that accelerate the growth of bone-building cells

Fig. 6. Cell adhesion on the surface of poly(L-lactide) and polycaprolactone [3]

Fig. 7. Combined spinal cage (cage for the intervertebral space) made from the materials Vestakeep (exterior) and Resomer (interior) on the Kumovis printer

Name - kk_Evonik

Dr. Philip Engel is Business Manager Medical Systems at Evonik Resource Efficiency GmbH, Marl, Germany; <a href="mailto:philip.engel@evonik.com">philip.engel@evonik.com</a>

Thomas Perl is Project & Portfolio Manager at Evonik Resource Efficiency GmbH, Darmstadt, Germany; <a href="mailto:thomas.perl@evonik.com">thomas.perl@evonik.com</a>

Dr.-Ing. Cecile Boudot is Head Application Technology Biomaterials Medical Devices at Evonik Nutrition & Care GmbH, Darmstadt, Germany; <a href="mailto:cecile.boudot@evonik.com">cecile.boudot@evonik.com</a>