Formulation of inks

Functional materials are our expertise

Inks for OLEDs, QDs and OPV | Process development

How is a material made printable?

Our services | Equipment and expertise in printing | Project-relevant questions

How does printing work?

Ink formulation and process parameters | Inkjet printing | ESJET printing

Get to know our printing experts

Dr. Christine Boeffel 

Dr. Manuel Gensler

Functional materials are our competence

The research area Functional Materials and Devices at Fraunhofer IAP specializes, among other things, in the solution processing of conductive and semiconductive materials for organic electronics. With years of experience, wide range material knowledge and extensive analysis capabilities, we specialize in making functional materials printable for specific applications.


We develop inks for OLEDs, quantum dots and solar cells.

We benefit from years of expertise in printed organic light-emitting diodes (OLEDs), organic solar cells (OPVs) and quantum materials (quantum dots, QDs). Optimal functionality can only be achieved if all successively printed layers in the device fit together. To this end, we make organic and inorganic materials printable or adapt the printing parameters of commercially available inks. We have a wide selection of industrially relevant print heads at our disposal. With a pilot plant, we also have the emerging technology of electrostatic printing (ESJET) or electrohydrodynamic printing (EHDJET). 


We develop processes

Together with machine builders, we also offer comprehensive process development. Our consulting includes the development of process parameters and the entire production process. Technology transfer takes place on site. For OLED production, we offer complete solutions based on comprehensive expertise from the technology network GOTA - German OLED Technology Alliance.

How is a material made printable?

How do we make materials printable?

We combine material knowledge, analytical expertise and testing capabilities for optimal ink formulation.

Our services

Challenges of the adjustable parameters of an ink 


  • Viscosity, surface tension and density must match the print head
  • Viscoelastic properties: Functional inks in particular tend to show a strong dependence of viscosity on shear rate.
  • Hydrodynamic radius: The particle size of the components contained must match the drop volume
  • Waveform: For optimal printing results, an ink must form uniform and stable droplets to exhibit uniform patterning on the substrate

Dr. Manuel Gensler says:

"In principle, one can make almost any material printable. In most cases, the optimization of one parameter produces undesirable effects with other parameters. This is where we come in with our expertise and look for targeted solutions that fit the desired application."

Equipment and expertise in printing

Our many years of experience and extensive equipment make us the ideal partner in projects aimed at solution processing. In a (300 square meter) clean room as well as in an inert environment, we have six different types of printers and various measuring devices at our disposal.

Our printing farm

Technical facilities


  • Rotary Rheometer
  • Tensiometer
  • LP50 printer - clean room, fume hood and glovebox or inert
  • Dimatix printer 
  • Microdrop
  • Calibrated optical microscope 
  • 3D profilometer (Dektak XT)
  • AFM
  • 4-point measuring station

Questions relevant to the project


  1. Which material is to be made printable?

  2. What are the requirements for the printed layers?
    (e.g. with regard to print image, roughness, thickness, conductivity, stretchability)

  3. Which structures are to be printed?

  4. Which process should be used to print the ink?

  5. What is the temperature stability of the substrate?

  6. How long are the intervals between successive printing processes?

Solution processing challenges

We find the right ink formulation meeting customer-specific and material requirements.

How does printing work?

Ink formulation and process parameters

© Fraunhofer IAP

Inkjet printing

Inkjet is a well established technology in the printing industry and used in a broad range of applications. It is a digital printing technology and enables quick change of layout and designs. As such, also some home-printers make use of piezo instead of heating elements. Inkjet printing is contactless and can be used on almost any substrate, even on sticky or viscous surface coatings. Droplets as small as 1 picoliter are ejected from nozzle chambers inside multi-nozzle printheads by mechanical actuation. The specific movement of a piezo element in every nozzle chamber (the waveform) brings the ink into oscillation. The droplet size is determined by the nozzle orifice. 

There is a huge interest in solution-processing of OLED or QD-LED devices for TV and monitor applications by inkjet printing. Here the advantages are scalability to larger areas, the high degree of possible individualization and savings in materials compared to evaporation technologies. At Fraunhofer IAP, we have experience in inkjet printing of OLED and QD-LED devices and offer process development.

ESJET printing

Electrostatic jet printing (ESJET)
, also known as electrohydrodynamic jet printing (EHDJET) or super inkjet (SIJ), is an emerging new technology for printing very high resolution, high aspect ratio structures. Here, droplets or continuous jets are ejected by applied electric fields instead of mechanical actuation. In this way, inks in a very wide viscosity range from 1 to 10000 cP can be printed: 

  • Low-viscosity inks can be printed through very small nozzle openings of only a few µm in diameter, where mechanical actuation does not apply sufficiently large forces. In this way, droplets and continuous lines with a diameter of 1 - 10 µm can be printed.  
  • Highly viscous inks can be printed through larger nozzle openings of 50 µm - 100 µm diameter. Ink is ejected at the tip of a Taylor cone, which forms due to the forces acting on the meniscus. In this way, much smaller droplets and continuous lines of 10 µm - 100 µm and high aspect ratio are printable. 

So far, only single nozzle ESJET systems are available on the market. Several companies are pushing this technology further to achieve higher throughput and a broader field of application, for example for smartphone or microdisplay applications. At Fraunhofer IAP, we know the specific ink and pattern requirements and develop appropriate processes according to customer needs.

Devices of our printing farm

Rotary rheometer

The analysis of the viscoelastic properties of a material is carried out by measuring the shear effects. The resistance of an ink to shear by a linear or oscillating motion is measured.  Plate/plate, cone/plate and coaxial cylinder measuring system.


The bubble pressure method is used to determine the dynamic surface tension of a liquid. An air bubble with variable velocity is generated via a thin capillary. The maximum internal pressure of the spherical bubble depends on the surface tension.


The Dektak is a tactile profilometer for surface analysis. A fine stylus is used to scan the surface line by line. Both the substrate to be printed and the printed product can be analyzed in this way.

4-point measuring

The 4-point measurement is a method for determining the conductivity of very thin layers. The current is induced via the outer electrodes. The measurement of the potential difference of the middle tips is thus independent of the contact resistance to the measuring tips. 


The Microdrop is a piezo-based microdispenser for volumes from 25 to 500 pl. Single, easily accessible capillaries are used for printing. This makes the device suitable for special developments and highly complicated inks, e.g. nanoparticles with complex geometries. 

LP50 glovebox

The LP50 is a flexible printer platform for a variety of industrially relevant printheads. Inks and printing parameters can be adapted on a laboratory scale. One of the three LP50 printers at the IAP is located in a glovebox to make air-sensitive inks printable as well. 


Our printers are equipped with optical systems and cameras to observe droplet formation from the side view. This allows the shape, speed, direction of spread and volume of the droplets to be determined and measured. 

Dimatix printer

The Dimatix Materials Printer is a widely used laboratory printer for which many manufacturers adapt their inkjet inks. The print heads are quite simple in design and therefore inexpensive. The device is ideal for initial tests of the printability of unknown inks.

Your contacts

Our experts in printing

Christine Boeffel

Contact Press / Media

Dr. Christine Boeffel

printing technologies

Fraunhofer Institute for Applied Polymer Research IAP
Geiselbergstraße 69
14476 Potsdam-Golm, Germany

Phone +49 331 568-1915

Manuel Gensler

Contact Press / Media

Dr. Manuel Gensler

printing technologies

Geiselbergstraße 69
14476 Potsdam-Golm, Germany

Phone +49 331 568-1913