Additive manufacturing technologies (AMT) have gained a lot of interest as potential method for future tool-less manufacturing. The key challenge is to finally print parts whose geometrical as well as mechanical and functional properties are at least as good as those of conventionally (e.g. by polymer injection moulding) manufactured parts. The current dilemma of AMT is the fact that none of the currently available technologies can provide high geometrical quality (surface roughness, precision) and high mechanical qualities (strength, toughness, heat deflection temperature) at the same time. Lithography-based AMT (e.g. stereolithography) have the capability to achieve excellent feature resolution, surface quality and precision, but suffer severely from the fact that the available photopolymers exhibit low toughness and/or low heat deflection temperature.

The goal of this project is to provide a new class of thermoplast-like photopolymers which allow to 3D-print parts with high resolution and precision, and at the same time significantly improved thermomechanical properties, especially an improved fracture toughness. The hypothesis, which will facilitate these improvements compared to the state of the art, assumes that a strongly covalently dominated polymer network will always be brittle, since chemical bonds can only be broken irreversibly. Using a fracture mechanical approach, new monomer formulations will be developed and screened regarding their suitability for lithography-based AM.

Contact: Prof. Jürgen Stampfl (juergen.stampfl@tuwien.ac.at)

© Cubicure GmnbH

Image of a 3D printed heart

Image of a 3D printed heart

Current additive manufacturing technologies (AMTs) are said to allow the production of parts with nearly unlimited freedom of design. However, the real benefit of the typical layer wise production is rarely addressed: within the buildup of a printed part, each volume segment (e.g. voxel) can be accessed. This allows the production of so-called Digital Materials, were each spatial point can carry different material property information. Being limited in either resolution, mechanical properties or throughput, different AMTs need to be combined to fully exploit their specific advantages.

In recent projects we successfully showed how the combination of stereolithography with inkjet printheads can lead to advanced material properties (see Machines BP5). To take this approach to the next level, a hybrid printing system for large scale production is developed together with Cubicure GmbH, opens an external URL in a new window. Using inkjet technology, the functionality of SL-printed parts with high resolution, surface quality and thermo-mechanical performance is expanded. This opens the possibilities to selectively modify the part’s properties, for example color, stiffness or wear resistance. Within this project, new materials and processes are developed.

Gefördert von der Wirtschaftsagentur Wien

Vascularization is the process of formation of blood vessels inside a living tissue. This is particularly important in tissue engineering and regenerative medicine, in order for nutrients to reach the cells in large tissue constructs. Especially for in-vitro models, such as organ-on-chips, a precisely controlled vascularization is fundamental to obtaining a complex and interconnected multi-tissue systems where, besides nutrients, also drugs and hormones can be transported.

We exploit high-resolution 3D printing in order to create defined patterns, helping cells to organise and migrate, and finally produce micro-vascular networks inside a cell-supporting hydrogel matrix. The resulting cell sprouting is referred to as guided vascularization and holds great potential for engineering of 3D tissue models, as well as tissue regeneration.

© Jürgen Stampfl

Picture of the kick-off meeting in Shanghai (Sep 2015) with partners from Shanghai University, TU…

Picture of the kick-off meeting in Shanghai (Sep 2015) with partners from Shanghai University, TU Wien and Lithoz.

Picture of the kick-off meeting in Shanghai (Sep 2015) with partners from Shanghai University, TU Wien and Lithoz.

Hydroceram aims at establishing water-based photopolymers (hydrogels) with ceramic nano-particles as fillers for lithography-based AMT. Two application fields will be explored within this project: (1) Biocompatible and biodegradable hydrogels filled with calcium phosphates as potential implant materials and (2) environmentally friendly, ceramic filled photocurable hydrogels  for the manufacturing of zirconia parts.

The project requires developments in two fields of research: Synthesis and characterization (1) of innovative photocurable monomers based on hydrophilic methacrylates and vinyl esters which are sufficiently reactive for being processed in lithography-based additive manufacturing equipment (e.g. stereolithography). (2) Development of new nano-particulate ceramic particles will allow the formulation of ceramic filled bio-hydrogels as well as zirconia-filled photopolymers for the manufacturing of dense ceramic parts. The targeted nano-particles offer two benefits over traditionally used materials: The required sintering temperature can be lowered significantly, leading to a finer ceramic microstructure and better mechanical properties. Additionally, problems with settlement of particles inside the photocurable formulation can be reduced.

The project is funded by the FFG and involves partners from TU Wien (coordinator Prof. Stampfl), Shanghai University (Prof. Shuai YUAN) and Lithoz GmbH.

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Focus of developments within ToMax

Focus of developments within ToMax

Lithography based additive manufacturing technologies (L-AMT) are capable of fabricating parts with excellent surface quality, good feature resolution and precision. ToMax, opens an external URL in a new window aims at developing integrated lithography-based additive manufacturing systems for the fabrication of ceramic parts with high shape complexity. The focus of the project is to unite industrial know-how in the field of software development, photopolymers and ceramics, high-performance light-sources, system integration, life cycle analysis, industrial exploitation and rewarding end-user cases.

The consortium will provide 3D-printers with high throughput and outstanding materials and energy efficiency. The project is clearly industrially driven, with 8 out of 10 partner being SMEs or industry.

Targeted end-use applications include ceramics for aerospace engineering, medical devices and energy efficient lighting applications. The consortium is aiming to exploit disruptive applications of L-AMT by developing process chains beyond the current state of the art, with the dedicated goal to provide manufacturing technologies for European Factories of the Future.

By relying on L-AMT, ToMax, opens an external URL in a new window the following objectives are targeted:

(1) ToMax will provide methods which are 75% more material efficient with respect to traditional manufacturing

(2) Are 25% more material efficient with respect to current AMT approaches by using computational modelling to optimize geometries and by providing recyclable wash-away supports.

(3) ToMax will provide methods which are 35% more energy efficient that current AMT approaches by developing 50% faster thermal processing procedures.

(4) Incorporate recycling for the first time in L-AMT of engineering ceramics

Overall, the consortium will provide innovative, resource efficient manufacturing processes. ToMax will develop energy-efficient machinery and processes, with a focus on manufacturing of alumina, silicon nitride and cermet parts with high shape complexity.

TU Wien (Prof. Stampfl) is the scientific coordinator of ToMax. The project is funded by the European Union in the programme , opens an external URL in a new windowFactories of the Future., opens an external URL in a new window

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Focus of developments within Addmanu.at

Focus of developments within Addmanu.at

The lead-project AddManu.at, opens an external URL in a new window will form a national research network with an international scientific board in order to find recognition and acceptance within the Austrian economy. Four AM-technologies are brought into focus (Lithography based AM, Fused deposition Modelling - FDM, Inkjet and Selective Laser Melting), which have the largest potential for industrial application and further development. The most important families of engineering materials, i.e. ceramics, polymers and metals are included. Based on longtime expertise of consortium partners and intensive research work, the project will deal with those problems, which can be considered as barriers for further developments and economic use or which have a very high innovation potential. Within AddManu.at, the R&D-activities are divided in four areas: materials development, design and dimensioning, process-specific and application-oriented aspects, each for metals and non-metals. Cross-sectional issues, like system integration are dealed covered in a separate working package.

The most important objectives are:

• Material developments for improved processing and service properties of AM-built components, like new powder materials and hybrids (composites, segmented structures etc.)
• The innovation potential of AM-processes will primarily depend on the designer’s creativity and the use of sophisticated FEM-software packages for light weight design. By adaption of methods like topology and shape optimization to AM-specific issues and coupling with extremely fine lattice structures, novel solutions are generated and new user markets can be generated
• Process developments for AM-technologies, lithography-based AM, fused deposition modelling and inkjet.

The industrial implementation of novel AM-concepts within the fundamental R&D-areas will be done in separate working packages, which are dedicated to the branches mechanical engineering, tooling, automotive engineering, semiconductor industry, refractory industry and aerospace industry. Solutions will be searched, which offer significant competitive advantages,

The most important deliverables and findings will be:

• Development of new materials (metal powders, ceramics, thermoplastic photopolymers) with significantly improved material properties.
• Development of an AM-concept to build hybride components made of metal/ceramics, steel/aluminium
• Development of novel lithography-based AM-processes with significantly improved resolution and higher operational capacity.
• Development of post-processing-methods to improve the surface quality of AM-built products
• Development of new industrial applications taking into account the whole processing chain.

The project management is performed by Montanuniversität Leoben, TU Wien (Prof. Stampfl) is the scientific coordinator. The project is funded by FFG

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The picture shows a 3D printed denture

The picture shows a 3D printed denture

Photopolymers are plastics that harden on exposure to light. In modern dentistry, they are used for fillings, restoratives, inlays and crowns. This project will explore the underlying properties of these materials with the aim of improving performance, for example in relation to curing, shrinkage and controlled removability.

The approach of the laboratory is very broad and covers the entire R&D spectrum of new photo-curing materials: from chemical synthesis, production and processing to process development and material characterization. This breadth is also reflected in the management of the laboratory: Two scientists with different specialties - synthetic chemistry and materials science - working together to develop new materials.

Objectives of the research activities are on the one hand more durable and easier to process materials for restorative purposes (i.e. fillings) as well as materials that have to be made ​​specifically for the patient such as crowns and bridges. For patient-specific contouring, ceramic-based materials are being developed that can be processed with advanced 3D printers. The objective here is to offer materials and processes for esthetic restorations in digital dentistry.

 One of the major problems in relation to restorative applications is limited photoreactivity, which effects material strength and depth of cure. Classically, photopolymers are cured with ultraviolet light; however, UV light is potentially harmful both to the patient and the dentist, which necessitates the use of visible light. The scientists of the laboratory therefore investigate photoinitiators that efficiently absorb at or even beyond 450 nm. The detailed knowledge of the photochemical properties of the initiators and of crosslinking kinetics ensures better performing materials.

Another aim of the project is the development of materials that during curing shrink less than currently used materials. This shrinkage may in fact lead to the formation of microvoids and microcracks and promote the formation of marginal gaps.

Finally, emphasis is placed on improved adhesives for braces, where the material should be easily removed when they are no longer needed. Investigations are being made in both thermal and photochemical methods for controllably debonding the adhesive from the tooth.

Contact: Prof. R. Liska, Prof. J. Stampfl

Funding: Christian Doppler Research Society

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2PP-processed hydrogel structure

2PP-processed hydrogel structure

Traditional 2D cell culture systems used in biology do not accurately reproduce the 3D structure, function, or physiology of living tissue. Resulting behaviour and responses of cells are substantially different from those observed within natural extracellular matrices (ECM). The early designs of 3D cell-culture matrices focused on their bulk properties, while disregarding individual cell environment. However, recent findings indicate that the role of the ECM extends beyond a simple structural support to regulation of cell and tissue function. So far the mechanisms of this regulation are not fully understood, due to technical limitations of available research tools, diversity of tissues and complexity of cell-matrix interactions.

The main goal of this project is to develop a versatile and straightforward method, enabling systematic studies of cell-matrix interactions. 3D CAD matrices will be produced by femtosecond laser-induced polymerization of hydrogels with cells in them. Cell embedment results in a tissue-like intimate cell-matrix contact and appropriate cell densities right from the start.

A unique advantage of the LeBMEC is its capability to alter on demand a multitude of individual properties of produced 3D matrices, including: geometry, stiffness, and cell adhesion properties. It allows us systematically reconstruct and identify the key biomimetic properties of the ECM in vitro. The particular focus of this project is on the role of local mechanical properties of produced hydrogel constructs. It is known that, stem cells on soft 2D substrates differentiate into neurons, stiffer substrates induce bone cells, and intermediate ones result in myoblasts. With LeBMEC, a controlled distribution of site-specific stiffness within the same hydrogel matrix can be achieved in 3D. This way, by rational design of cell-culture matrices initially embedding only stem cells, for realisation of precisely defined 3D multi-tissue constructs, is possible for the first time.

Principal investigator: Prof. Aleksandr Ovsianikov (aleksandr.ovsianikov@tuwien.ac.at)

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picture of the World’s smallest 3D Printer

picture of the World’s smallest 3D Printer

A research project at the TU Wien could turn futuristic 3D-printers into affordable everyday items.

Printers, which can produce three-dimensional objects have been available for years. However, at the TU Wien, a printing device has now been developed, which is much smaller, lighter and cheaper than ordinary 3D-printers. With this kind of printer, everyone could produce small, taylor-made 3D-objects at home, using building plans from the internet – and this could save money for expensive custom-built spare parts.

Several scientific fields have to come together, to design a 3D-printer. The device was assembled by mechanical engineers in the research group of professor Jürgen Stampfl, but also the chemical research by the team of professor Robert Liska was of crucial importance: first, chemists have to determine which special kinds of synthetic material can be used for printing.

Layer for Layer

The basic principle of the 3D-printer is quite simple: The desired object is printed in a small tub filled with synthetic resin. The resin has a very special property: It hardens precisely where it is illuminated with intense beams of light. Layer for layer, the synthetic resin is irradiated at exactly the right spots. When one layer hardens, the next layer can be attached to it, until the object is completed. This method is called “additive manufacturing technology”. “This way, we can even produce complicated geometrical objects with an intricate inner structure, which could never be made using casting techniques”, Klaus Stadlmann explains. He developed the prototype together with Markus Hatzenbichler.

This method is not designed for large-scale production of bulk articles – for that, there are cheaper alternatives. The great advantage of additive manufacturing is the fact that is offers the possibility to produce taylor-made, individually adjusted items. The prototype of the printer is no bigger than a carton of milk, it weighs 1.5 kilograms, and at just 1200 Euros, it was remarkably cheap. “We will continue to reduce the size of the printer, and the price will definitely decrease too, if it is produced in large quantities”, Klaus Stadlmann believes.

LED-Projector for Higher Resolution

The printer’s resolution is excellent: The individual layers hardened by the light beams are just a twentieth of a millimetre thick. Therefore, the printer can be used for applications which require extraordinary precision – such as construction parts for hearing aids. Unlike previous models, the printer at TU Wien uses light emitting diodes, with which high intensities of light can be obtained at very well-defined positions.

The research group for additive manufacturing technologies  at TU Wien is working with a variety of different 3D-techniques and materials. New materials – such as special ceramics or polymers – are constantly being developed for 3D-printing. 3D objects can now even be made from eco-friendly biodegradable substances. In cooperation with biologists and physicians, the scientists could show that the artificial structures created with their 3D-printer technology are perfectly suited to serve as a scaffold that supports natural growth of bone structure in the body.

Remarkable Versatility

No matter whether it is medical parts, adjusted exactly to the patient’s needs, special spare parts which otherwise would have to be shipped around half the globe, or whether it is just some kind of self-designed bling jewellery: with the versatile and cheap devices and materials developed in Vienna, highly complex 3D objects can now be built from a variety of materials with very different mechanical, optical and thermal properties.

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Photos in different enlargement of the fairytale castle on the tip of the pencil

Photos in different enlargement of the fairytale castle on the tip of the pencil

Multiphoton lithography (MPL) or multiphoton processing is an umbrella term for 3D printing methods relying on photochemical reactions triggered by multiphoton absorption (MPA). The most popular approach is the two-photon polymerization (2PP), also sometimes referred to as two-photon-absorbed photopolymerization, two-photon induced polymerization, two-photon lithography, two-photon laser scanning lithography, multiphoton-excited microfabrication, 3D multiphoton lithography, 3D laser lithography or even direct laser writing. Due to multiphoton absorption it allows the realization of complex 3D structures with spatial resolution down to a 100 nm level.

In our most recent effort to demonstrate the capabilities of MPL we have produced a tiny castle (230 µm x 250 µm x 360 µm) directly on a tip of a pencil. Its design was developed in cooperation with Daniela Mitterberger and Tiziano Derme (MäID – FutureRetrospectiveNarrative, opens an external URL in a new window). The Scanning Electron Microscopy (SEM) image of produced structure appeared on the cover of the recent book “Multiphoton Lithography: Techniques, Materials, and Applications, opens an external URL in a new window”.

Multiphoton fabrication

Video explaining fabrication of a tiny castle by multiphoton lithography: https://www.youtube.com/watch?v=mdup3w7DCZE, opens an external URL in a new window

Video: Wolfgang Steiger

Music: Tube by SPCZ (http://freemusicarchive.org/music/SPCZ/)

Voice: Angelika Kubacek

In-vivo-writing

One of the big benefits of 2PP is the possibility to use infrared light for inducing photopolymerization. Since infrared light does not harm living tissue, 2PP facilitates to perform photopolymerization in the presence of living cells or organisms. By using appropriate biophotopolymers 3D-structures can be printed around living tissue, as indicated by this video, where a cellular scaffold is structured around a nematode.

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In-vivo writing in the presence of C. elegans.

In-vivo writing in the presence of C. elegans.

One of the great advantages of multiphoton lithography is the ability to use infrared light to induce photopolymerization. Since infrared light does not damage living tissue, 2PP makes it easier to carry out photopolymerization in the presence of living cells or organisms. By using appropriate biophotopolymers, 3D structures can be printed around living tissue, as shown in this video where a cell scaffold is patterned around a nematode.