Inks and Materials for 2D/3D Printing and Bioprinting

Novel additive manufacturing processes are currently being worked on in a variety of research fields. Among the established printing techniques, inkjet printing offers a highly attractive technique for creating two-dimensional or three-dimensional structures that are previously designed on a computer.

Our work focuses on the development of suitable ink formulations to process diverse functional components such as hydrogels, nano- and microparticles, proteins and cells.

Services

  • Formulation of aqueous or solvent-based inkjet inks
  • Biofunctional inks
  • Cell-containing inks
  • Nano- and microparticle containing inks
  • UV-curable inks
  • Conductive and semiconductor inks
  • Printing of high-resolution structures
  • Laser printing polymer particles for biomaterial

Applications

  • Production of medical assays, rapid tests
  • Production of tissue models for diagnostic and pharmacological tests
  • Production of personalized implants

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Biological materials for 3D printing

Preparation of functional inks

To adjust the viscosity and surface tension of functional inks, the properties of the functional components are adjusted. Depending on the requirements, aqueous or solvent-based inks are produced. For applications in tissue engineering, for example, initiator-free cross-linking biocompatible hydrogels are developed and biomolecules are equipped with cross-linkable groups or functionalities through chemical modification to control the solubility properties and viscosity.

For optimal printing results, different substrate materials are pre-treated wet-chemically or by means of plasma technology in order to obtain an optimal print image.


The following examples of inks are in our focus:

  • Initiator-free networking two-component systems
  • Modified biomolecules
  • Inks containing cells
  • Suspensions of metallic or oxidic particles
  • Inks containing carbon

Gelatin-based bioink with adjusted viscosity.
© Fraunhofer IGB
Gelatin-based bioink with adjusted viscosity.

Hydrogel-based materials for ink formulation

For 2D/3D printing, Fraunhofer IGB develops e.g. initiator-free crosslinking biocompatible hydrogels and equips biopolymers with crosslinkable groups or functionalities by chemical modification. This allows the solubility properties and viscosity to be controlled and an adaptation to the different requirements of additive processes such as inkjet printing or pneumatic dispensing to be made possible.

We want to enable biopolymers such as gelatin, hyaluronic acid and chondroitin sulfate to modify surfaces and build three-dimensional tissue models. To control the physicochemical properties of biomolecules and hydrogels, we couple chemical functions such as crosslinkable methacrylic groups, thiol groups and benzophenones to the biopolymers and mask functional groups responsible for gelling of the materials.

In cooperation with the IGVP at the University of Stuttgart, we are also developing printable and crosslinkable cell-compatible polyethylene glycols.

Further information

Printable (bio)polymer solutions.
© Fraunhofer IGB
Printable (bio)polymer solutions.
Adaption of the surface tension of inkjet inks.
Adaption of the surface tension of inkjet inks.

Biofunctional and cell-containing inks

If the inks contain biological materials such as biomolecules, cells, tissue preparations or biocompatible materials, the printed structures can perform a biological function. The biomaterial in its non-crosslinked, printable form is referred to as a bioink. The composition of these inks depends on the subsequent application. Thus, bioinks can be formulated with and without cells.

Bioinks for tissue engineering applications are optimized for the printing process and at the same time for the promotion of tissue-specific functions through targeted variation of the composition. We have already successfully produced "bone inks" and "vascularization inks" based on the available material construction kit. Both bioinks are dispersions of biomolecules and tissue-specific cells that can be stably formed into a 3D structure via dispensing processes.

Protein-containing bioinks should be processable while maintaining the native functionality of the proteins. We achieve this by using water-soluble and protein-compatible components. These inks can be used, for example, to make specific areas on a substrate attractive for adhesion of different cell types.

Gedruckte Partikelschichten im Druckwerk des Hochpräzisionsdruckers DMP 3000.
© Fraunhofer IGB
Printed particle layers in the printing unit of the DMP 3000 high-precision printer.

Particulate inks

Nanoparticles have the potential to transport a variety of functions: Both the properties of the particle shell, such as being equipped with certain chemical groups and the loading of the particle core with dyes or active components, which are released after printing, for example in contact with water, can contribute to the systematic design of material properties. We are developing inkjet-compatible formulations at the Fraunhofer IGB, for the targeted and structured application of suspensions of functional nanoparticles. For example, we have developed a water-based ink for coating surfaces with charged nanoparticles. These inks could find their application in the production of sensitive rapid tests based on nucleic acid microarrays.

Generative manufacturing / additive processes

The generative manufacturing of innovative products already plays a major role in research and development on a laboratory scale. For this, Fraunhofer IGB has at its disposal equipment for upscaling and further development in the area of embossing processes as well as of additive processes.

At Fraunhofer IGB, embossing processes can be carried out in a batch process using a hot press, or in continuous roll-to-roll processes.

Inkjet printers and dispensers are available for additive processes. The available process technology is used to respond specifically to the latest requirements.

Printing processes

Cell interacting with microparticle-coated surface.
Cell interacting with microparticle-coated surface.
Gedruckte Partikelschichten im Druckwerk des Hochpräzisionsdruckers DMP 3000.
Gedruckte Partikelschichten im Druckwerk des Hochpräzisionsdruckers DMP 3000.

The development of biomaterials sometimes requires the flexible functionalization of surfaces, for example the coexistence of cell-adhesive and cell-rejecting areas or the combination of hydrophilic and hydrophobic areas in the production of microfluidic test systems. 

With the help of digital printing processes such as inkjet printing or Laser Induced Forward Transfer (LIFT), material layers can be applied to surfaces direct, i.e. without the elaborate manufacturing of masks, in any programmable patterns that are required.

At Fraunhofer IGB we develop inkjet-suitable inks for coating surfaces with biological and biofunctional materials such as proteins or active substance-loaded, degradable particles. The high-precision inkjet printer DMP 3000 (Fujifilm Dimatix, USA) is available to produce functional layers with resolutions in the micrometer range.

For example, we print cross-linkable polymers to produce microstructured hydrogels that form hydrophilic areas and can also fix particles on the surface or serve directly as reservoirs for active substances. FDA-approved dyes are available for inks used to mark medical devices or food products. Cell-adhesive areas can be created by coating them with proteins or simple organic linkers.

 

 

Digital inkjet printing

Novel additive manufacturing processes are currently being worked on in a variety of research fields. Among the established printing techniques, inkjet printing offers a highly attractive technique for creating surface or three-dimensional structures that are previously designed on the computer.

Digital inkjet printing produces small, uniformly sized droplets that can be used as microcomponents. This allows spatially resolved structures of new, but also known materials to be created in an innovative way. Fraunhofer IGB is therefore focusing its research on inkjet printing as a manufacturing tool for the individualization of production processes.

At Fraunhofer IGB, ink formulations for processing a wide range of functional components such as hydrogels, nanoparticles, proteins and conductive materials are being developed.

Two-component reactive printing of polyurethane foams

Reactive printing using a Fujifilm Dimatix inkjet printer.
© Fraunhofer IGB
Reactive printing using a Fujifilm Dimatix inkjet printer.

The combination of inkjet printing and the well-known polyurethane chemistry has great potential for future production of functional materials. At present, we are focusing on the production of polyurethane foams using two-component reactive inkjet printing. Two inks (an isocyanate-functional and, for example, a hydroxy-functional ink), each containing a reactive component, are printed separately in layers.

Biopolymers with adjustable properties

ECM biomolecules are also used in pharmaceutical and cosmetic formulations. As an animal by-product, gelatin has multiple technical applications as well. Fraunhofer IGB offers services in development, consulting and technology transfer.

 

Printing devices

  • Jet-printer (Nanoplotter, GeSiM mbH, D; DMP 3000, Fujifilm, USA)
  • Pneumatic or extrusion based dispenser (Prototype, Unitechnologies, CH; System 30, Hyrel3D, USA)

 

Biomaterials with adjustable properties

  • Gelatin
  • Collagen
  • Hyaluronic acid
  • Chondroitin sulfate
  • Heparin    

 

Chemical modifications

For crosslinking

  • methacrylic functions
  • thio functions
  • benzophenone

For reducing intermolecular interactions (masking)

  • e.g. acetyl groups (DE 10 2012 219 691 B4 2015)    

 

Features and applications

  • Control of viscosity
  • Control of gelling behavior
  • Crosslinked hydrogels with adjusted stiffness, swelling
  • API storage with controlled release
  • Biobased fluids with adjusted flow characteristics
  • Cytocompatible or tissue-specific 3D matrices

 

Analysis

 

Cells and tissues

  • Primary cells isolated from human or mammalian biopsies, e.g. mesenchymal stem cells / chondrocytes, endothelial cells, mature adipocytes, skin cells  
  • 2D and 3D culture
  • Standard (immune)histological techniques and cell culture assays
  • Flow cytometry for characterization of cells and cytokines

Reference projects

 

Printable 3D matrices for the engineering of bioartificial cartilage

 

A promising therapy for cartilage damage is the matrix-associated autologous chondrocyte transplantation (MACT), in which a suitable material (matrix) is seeded with the patient's cartilage cells (chondrocytes) and then implanted into the damaged cartilage.

 

January 2017 – December 2019

Dyna-Implant

Personalized orthopedic implants through biomechanical stimulation of hybrid materials

There is an increasing interest in personalized therapies for the treatment of injuries or age‑related degeneration of cartilage tissue. One solution is the production of individual cartilage implants using additive manufacturing methods. For this purpose, Fraunhofer IGB is developing gelatin‑based hybrid hydrogels that mimic the natural tissue environment of cartilage cells and thus promote the biofunctionality and matrix production of the cells.

 

TRIANKLE

European TRIANKLE project will develop 3D bioprinted personalised scaffolds for tissue regeneration of ankle joint

The Research consortium is composed of 12 partners from 5 European countries and counts with a EU funding of €5.9M. TRIANKLE will provide fabrication of personalized implants for injured tendons or cartilages. Fraunhofer IGB will formulate and develop collagen- and gelatine-based bio-inks needed for 3D printing the personalised implants while the IGVP at the University of Stuttgart will research the bio-ink crosslinking chemistry and 3D-printing of bio-inks.

Reactive inkjet printing of polyurethan foams

 

The combination of inkjet printing and well-known polyurethane chemistry has great potential for the future production of functional materials. We have therefore investigated the production of polyurethane foams using two-component reactive inkjet printing.

MicroPrint – Functional inks for inkjet printing

 

Development of ink formulations for the processing of diverse functional components. In particular, we produce biofunctional inks to make biomolecules available for rapid and automated processing, for example for the production of sensors or medical assays.

ArtiVasc 3D – Flowable tissue models


Integrate different technologies from rapid prototyping and biofunctionalization into a process that enables the construction of vascular vessels in combination with a carrier system.

BioRap – Artificial blood vessel systems

 

The construction of larger tissue constructs has been limited so far because a nutrient supply through a vascular system - comparable to the blood vessel system in the body - is missing. The aim of the project is to develop artificial blood vessel systems.

Laser printed polymer particles for biomaterial applications

 

The use of different toner components ensures that the spatial arrangement of even complex structures is preserved.