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Bild: AFM-Ergebnisse einer tröpfchenartigen (a) und miteinander verbundenen (b) Phasenstruktur

Supervisor: J. Stampfl

Co-supervisor: H. Sandtner

Ph.D. student: M.Ahmadi

Objectives: The goal of this PhD project is the development and investigation of methods for providing heterogeneous, 3D-printable photopolymers with thermomechanical properties close to thermoplast like ABS. In polymer-based additive manufacturing, despite the fact that the amorphous photopolymers offer supreme stiffness, strength, and heat deflection temperature, their low toughness and elongation at break restrict their extensive use in 3D-printing engineering applications. These drawbacks stem from the homogeneous nature of amorphous materials, which limits their resistance to crack propagation and makes them susceptible to break. Eliminating this drawback through appropriate toughening mechanisms can open a broad spectrum of innovative applications for 3D-printed parts. The most relevant approach of toughening compliant with characteristics of photo-curable resins and predefined manufacturing is to create heterogeneity in the bulk polymer without using external instrumentation. This is feasible through a process known as Photopolymerization-Induced Phase Separation (PhIPS), which generates heterogeneity into an initially homogeneous system by enabling marginally or completely incompatible components to diffuse with the polymerization progress. The resulted structures offer adjustable mechanical properties based on the interaction of soft and hard phases so that the established domains are able to dissipate the associated energy of crack propagation and increase toughness and elongation at break without sacrificing strength or stiffness of the material.

© A. Otto

Bild: Vorläufige Ergebnisse einer gekoppelten Strömungs- und Festkörpermechanik-Simulation einer einspurigen Schweißspur im Leitungsmodus (Domänenschnitt entlang der Mittellinie der Schweißnaht); zeigt ein flüssiges Schmelzbad, das durch Temperatur und hydrostatische Festkörperspannung gefärbt ist (oben), axiale und vertikale Festkörperverschiebung (unten).

Supervisor: A. Otto

Co-supervisor: I. Miladinovic

Ph.D. student: C.Zenz

Objectives:

Additive manufacturing processes provide the possibility to produce physical parts directly from CAD. Many different processes like e.g. laser powder bed fusion (L-PBF) or laser direct energy deposition (L-DED) have been developed and industrialized in the past years. However, it is still very difficult to find the correct processing parameters for every single part to be produced. The thermal and thermo-mechanical as well as the metallurgical behaviour of a part during the building process are not only strongly influenced by the processing strategy but also by its geometry and material. This often leads to distortion or cracks, to overheated areas and to many other processing failures to be avoided. Thus, producing first-time-right parts, obviously strongly desired by industry, is still an exception and demands for skilled experts.

Process simulations provide the possibility to study the effects that lead to processing failures and are in principle an appropriate tool for supporting the process design. However, those simulations are very demanding as they exhibit both multiscale and metaphysical characteristics:

· Multiscale, both from the temporal and spatial point of view: typical building times for a part with dimensions of a few cubic centimetres are a few hours, typical fluctuation times on the process scale that may also lead to failures are a few microseconds and they take place on the µm-range.

· Multiphysical, as a correct process description involves optics, heat conduction including phase transitions, fluid dynamics, powder physics, solid mechanics, material science and so on.

Currently there are no simulation tools available covering all these multiscale and multiphysical aspects. Thus, a major objective of future research work in this field of additive manufacturing must be the development of tools and strategies that enable the simulation of laser-assisted additive manufacturing processes. This will be the prerequisite for the desired first-time-right production.

Based on previous work at TUW concerning the mechanistic simulation of the L-PBF process the PhD project aims at the implementation of several new features into the existing simulation tool. These include:

· Coupling of the existing model (based on discrete element method and fluid dynamics) and thermo-mechanics.

· Implementation of a grain growth models and other metallurgical aspects.

· Development of a simplified model for L-PBF in order to reduce the simulation time.

· Derivation of strategies to couple the mechanistic and the simplified model.

TU Wien will lead this PhD project by providing supervision and access to the in-house software for simulating laser material processing that has been developed within the last decade. The project will be embedded in the research group “Laser Process Simulation” providing strong expertise in programming and physics with respect to laser material processing.

© C. Hölzl

Bild: Beispiele für TO und Gitterstrukturen

Supervisor: C. Hölzl

Co-Supervisor: J. Stampfl

Ph.D. sStudent: S. Geyer

Objectives:

The goal of this PhD project is to develop algorithms for topologically optimized parts that can be produced by means of SLS and Hot Lithography. Using proven software tools such as SolidWorks for the design of models, Altair Inspire for topology optimization, ANSYS for verification via FEM and both Rhinoceros and Grasshopper for the development of algorithms for structural optimization via non-conformal lattice structures, an easy to use toolchain for part optimization is to be developed. In the scope of the development of algorithms, the potential of using machine learning algorithms will be evaluated and compared with conventional algorithms. For that purpose, components from the open source machine learning library LunchBoxML will be used and adopted.

Both mentioned Additive Manufacturing processes are to be used to produce the optimized parts that in a next step are to be verified via given tools of material testing. Parts produced using the Hot Lithography process additionally have to be optimized in respect of support structures so that no additional support is needed.

The key goal of this project is the development of tailored algorithms that automatically optimize input data from CAD and FEM software under the boundary conditions of design space, fixtures, loads and the soft kill option (SKO) approach, as well as physical parameters specific to the material/fabrication system used, to minimize weight and maximize stiffness of the resulting geometries.

FH Campus Wien will provide software needed to design and optimize part design as well as mentioned fabrication processes. Furthermore, FH Campus Wien will provide supervision for the development of algorithms and machine learning related topics.

TU Wien will provide tools and machinery to verify the optimized and manufactured parts.

© M. Bublin

Curling (a) and coating defects (b) in SLS processes with plastic powder

Supervisor: M. Bublin

Co-Supervisor: A. Otto

Ph.D. student: V. Klamert

Objectives:

There are already many in situ measurement methods, which monitor the process of selective laser sintering (SLS) with polymer powders. However, process monitoring is an important topic for determining the print quality and the mechanical properties of the components and should be improved during the PhD project. The efficiency of SLS processes for polymers increased by non-destructive analysis, since the reject is reduced by using predictive models. In addition, the aim is to replace sample examinations of the components with process monitoring and subsequent modelling of the influences in the event of errors in the process.

Defects in the powder bed, such as coating defects, uneven distribution of the powder over the installation space and uneven temperature distribution over the sintering process have a negative impact on the material properties of the component. This can lead to the fact that the manufactured components cannot be used for their intended purpose. In order to be able to assess the quality of the components after production, in situ measurement methods should be developed and implemented in the SLS system.

Shift errors can be detected using these measuring methods. With sufficient measuring accuracy of the methods, their influences on the subsequent layers of the components should also be determined. For this purpose, powder defects are specifically created, and their influence is determined.

In addition, dummy samples are produced to measure the effects of the errors on the material properties. Standard measuring methods are used to characterize the material properties (determination of tensile strength, bending strength, surface topology ...).

Based on the measurement data and the measurements of the material properties, a model should be created that describes the quality of the component in the SLS process. For this purpose, close coordination with the TUW, which contributes the material simulations, is required.

It is planned that the PhD candidate will continuously define and supervise theses (master and bachelor theses) from the aforementioned subject area during the doctorate.

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Figure: SEM image of microscaffolds (A), agarose micro-well mold for cell seeding (B), illustration of the underlying tissue unit concept (C) and Live/dead staining of 4-weeks old spheroid formed inside BB, with red revealing auto-fluorescent microscaffold (D)

Tissue engineering is a highly interdisciplinary research field with the long-term goal to restore and/or replace defective tissues. In contrast to the two most widespread approaches, namely scaffold-based and a scaffold-free approach, this project aims to develop a radically new strategy combining the advantages of the two approaches.

The concept of this third strategy in tissue engineering (THIRST) relies on multicellular spheroids encaged within robust microscaffolds. By using the right combination of cells within the spheroids and by combining different types of spheroids, different types of tissues can be created by self-assembly and further optimized on a micro level to enable vascularization. The microscaffolds are initially created by means of high-resolution 3D printing (Two-Photon Polymerization) and are subsequently cultivated in combination with the cells to form the final tissue modules.

The main challenges of this project are:

• Increasing the microscaffold fabrication throughput

• Automatic handling of the microscaffolds to scale up tissue unit production

• Developing protocols for functionalization of microscaffolds with according biomolecules

• Establishing protocols for cartilage and bone tissue engineering

Contact: Prof. Dr. Aleksandr Ovsianikov, wwwt.tuwien.ac.at/ovsianikov, opens an external URL in a new window

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In the CD laboratory we are eager to answer two important research questions out of the field of oral maxillofacial surgery, which are materials for the 3D printing of implants and bone adhesives to especially treat comminuted fractures.

In the last decade, considerable progress has been made in the field of 3D printed implants. Significant features of such implants are the possibility to manufacture them on the basis of the patients' individual CT scans and that they actually solely act as scaffolds, which support the regrowth of endogenous bone material, biodegrading simultaneously. Requirements of these functions are that (1) the material and its degradation products are non-toxic, (2) it can be manufactured by 3D printing, (3) the implants have a sufficient mechanical stability but also porosity, and (4) that this porosity can be filled with nutritive solutions with growth factors to promote vascularization, i.e., the ingrowth of blood vessels to support tissue growth. Vinyl ester, as basis for the materials, photopolymerized by the aid of light-sensitive photoinitiators have proved themselves as very promising starting materials. In the framework of the CD laboratory we will characterize the single components as well as final constructs from a biomedical and material science points of view.

Bone adhesives are considered to be applicable, whenever bone fixation with screws and/or plates is impossible, for example in case of comminuted fractures. A maximum adhesive force while possessing porosity and biodegradability are prerequisites for bone adhesives. As for the bone implants it is crucial that the material biodegrades over time, while endogenous bone tissue is regenerated.

In both field we will conduct fundamental material research in order to answer scientific questions, like boundary phase effects, layer inhomogeneities or delamination, which is the detachment of layers in 3D printed parts, as well as the interaction of adhesion and cohesion forces in bone adhesives.

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The desire to replace ivory and copy this treasured and at the same time ethically unjustifiable material is nothing new. Nevertheless, all commercially available replicas are deficient in the most important characteristics, especially the optical properties. Additionally, most of these materials are only available in bulk and not in the desired shape. Carving a replacement part out of either ivory or a bulk substitute can take a lot of time and is in most cases unaffordable.

In the course of this interdisciplinary research project of the TU Wien, Cubicure GmbH, The Department of Art and Preservation of Historical Monuments of the Archdiocese of Vienna and the restoration studio Addison KG, a 3D printable ivory substitute called “Digory” was developed to mimic not only the aesthetic but also the mechanical and haptic properties of ivory. The color and translucency are adjustable to resemble the original shade of individual ivory parts that are to be replaced. Also, the density and hardness values of Digory are comparable to ivory. With proper artistic post-processing the resemblance to natural ivory is additionally enhanced (Figure 1).

To replace, for example, missing column capitals of the shrine of Friedrich III of Austria (Figure 2), 3D printing provides an elegant solution to reproduce the artwork exactly as intended by the original artist. For that, one of the ivory capitals was detached and scanned to create a 3D model of the complex structure, which can now easily be reprinted for each missing column (Figure 3).

Digory offers an elephant-friendly alternative to ivory and rediscovers its aesthetic benefits. On the one hand, it can be used for the high-quality restoration of valuable art objects and, on the other hand, it is suitable for everyday applications, such as jewelry or interior decoration. Digital ivory combines classic beauty with modern design and innovative technology with traditional handicrafts.

Contact: Prof. J. Stampfl, Dipl.-Ing. Thaddäa Rath Funding: FFG: HSRM, Elfenbein3D Link 1: www.sciencedirect.com/science/article/abs/pii/S2352940721000810, opens an external URL in a new window Link 2: www.tuwien.at/tu-wien/aktuelles/news/news/elfenbein-ersatz-aus-dem-3d-drucker, opens an external URL in a new window

© EU

EIT-AddManu will provide hands-on learning nuggets for teaching Additive Manufacturing (AM) in higher academic and industrial education. The targeted course work, which will be made available on the EIT Manufacturing Guided Learning Platform, contains tools for teaching AM in terms of design-tools, screening suitable AM systems and selecting the right material for the job. Questions of regulatory topics together with international and industrial standards will also be addressed. Public as well as private educational institutions from Austria, Finland, the Netherlands and Spain are contributing to EIT-AddManu with innovative and relevant learning nuggets, aiming at motivating and educating the future generation of European AM specialists. (https://eitmanufacturing.eu/additive-manufacturing-teaching-factory/) Contact: Prof. Jürgen Stampfl, Dr Julia Anna Schönherr Funding: eitmanufacturing.eu

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Bioprint can re-create in vitro specific biofilm environment (e.g. chronic lung infection of patients affected by cystic fibrosis), which are then employed for high throughput drug screening. Such in vitro models are useful to understand how bacteria are responding to antibiotic treatments, and to develop better therapeutic modalities.

In March 2020, Dr Guillaume Olivier was granted a FWF stand-alone project, called BREATH.

The aim of the “Biofilm-REsponsive Adjuvant as novel THerapeutic approach” (BREATH) project is to develop 3D models of biofilm using 3D Bioprinting, to mimic cystic fibrosis-lung infection. Because of the presence of a sticky mucous secreted in the lung of CF-patients, bacteria (with Pseudomonas aeruginosa being predominant) will develop rapidly and form a biofilm. The specificity of this biofilm relies in its extracellular polymeric substances (EPS) composition, with high amount of alginate. The presence of alginate, with the other EPS, render the infection extremely, or even impossible to eradicate. As very few antibiotics have been discovered since several decades, the scientific community must focus its effort in optimising the efficacy of the ones currently available, which is the goal of the BREATH project.

A key point of the BREATH project is to develop in vitro a simplified 3D model of biofilm with features and characteristics relevant to mimic CF-lung condition. This model will be used as an in vitro tool to rapidly test antibiotics combined to new adjuvants, which could synergize their efficacy.

To reach the goal of BREATH, this multidisciplinary project gathers scientific expertise in biomaterials, chemistry, microbiology, in biointerface and pharmaceutical sciences. Researchers from TU Wien (Dr. Guillaume O and Prof. Ovsianikov A., Institute of Materials Science and Technology, 3D Printing and Biofabrication Group) in collaboration with the BOKU (Prof. Reimhult E., the Institute for Biologically Inspired Materials) are involved in this project.

If successful, our strategy could be employed to treat not only CF-lung infection but also to develop novel drug delivery systems that could potentially optimize the treatment of other biofilms and chronic infections.

© Cubicure GmnbH

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

© Jürgen Stampfl

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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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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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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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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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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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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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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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.