Research highlights from Fraunhofer FEP

Inactivate vaccines more effectively using electron beams

Since as early as the 1950s, toxic chemicals such as formaldehyde have been used to inactivate pathogens for so-called killed vaccines (e.g. to fight influenza, polio or hepatitis A viruses). This procedure, which has barely changed since, marked a miles­tone in infection biology at the time, however it is still subject to various limitations to this day. The chemical treatment, which can last several weeks, also destroys some of the pathogens' surface structures that the immune system could use to recognize and attack following infection. Drugs manufactured in this way either have to be administe­red in high concentrations or have to be boosted at regular intervals in order to offer sufficient protection – a fact that hampers their use in poorer and structurally weak countries.

Scientists at Fraunhofer FEP in conjunction with other partners within the Fraunhofer Gesellschaft have been conducting research for several years on employing elec­tron-beam technology in medical engineering. Low-energy inactivation of pathogens by means of electron beams (LEEI – Low-Energy Electron Irradiation) can also be used for faster manufacture of more effective vaccines. Most vaccinations are based on inactivated vaccines, i.e. vaccines containing viruses that are inhibited from further reproduction. The pathogens can then no longer cause disease in patients. Nevertheless, the immune system still detects them and forms the corresponding antibodies to provide effective protection. Usually the pathogens must be kept in a chemical for several days until they are inactivated. Formaldehyde, for example, needs approximately two weeks in order to neutralize hepatitis A viruses. This expenditure of time is costly and a disadvantage for industry. In addition, formaldehyde attacks the viruses' proteins that the immune system forms the antibodies to. Formal­dehyde thus alters the viruses, thereby reducing the actual effectiveness of the vaccine. The Fraunhofer consortium is very experience in the development of new technologies that use low-energy electron beams. The results of the project have established that the technology is fundamentally viable for a wide range of viruses, such as influenza and Porcine Reproductive and Respiratory Syndrome virus/PRRSV that triggers this syndrome in swine, as well as other types of pathogens like bacteria and parasites. The genetic substance necessary for the viruses to self-replicate is destroyed by the irradiation. However, the surface characteristics of the virus important for the immune system response are retained by LEEI, in contrast to chemical inactivation using toxins like formaldehyde. This allows the body to form antibodies having greater specificity for the pathogen, which provides improved protection. As a result, lower vaccination doses might be able to be employed. Moreover, just a few milliseconds are sufficient to inactivate the viruses or bacteria thanks to this technology, instead of several days or even weeks. An additional advantage of irradiation using low-energy electrons is that it can be carried out in any laboratory. Innovative medical products can likewise be sterilized effectively by low-energy elec­trons. Artificial knee joints with integrated electronics for monitoring deterioration are conceivable for example, or implants like cardiac valves with novel combinations of materials including biological tissue that need to be sterilized before their insertion.

Ultra-thin glass on roll for flexible electronics and novel thin film coating processes

Ultra-thin glass is thinner than paper. It is that flexible, that it could be wound into rolls. Ultra-thin glass can be used as a substrate as well as for encapsulation in many smart products such as smartphones, curved displays, OLED light sources and photovoltaics or glazing.

Fraunhofer FEP is an experienced partner for technological developments, known for testing the limits of new materials and for optimization of those materials with respect to market demands. Moreover, ultra-thin glass has excellent surface properties that considerably exceed the ones of conventional plastic films. Ultra-thin glass offers outstanding possibilities for deposition of transparent, electrically conductive films that are indispensable for numerous applications in high-tech electro­nics.

With its experience and knowledge in the field of ultra-thin glass, Fraunhofer FEP is a leading research partner for sheet-to-sheet and roll-to-roll processes right through to application of this material in organic electronics. The focus of recent activities is on sheet-to-sheet- and role-to-role-deposition to enable the application of those substrates in high-tech-devices. Furthermore concepts to adapt the in-line-vacuum and handling processes of the ultra-thin glass are developed. The machine design is also adjusted in order to safely coat large-area ultra-thin glass. The pretreatment of glass plays an important role in the further coating-process.

Wearable visualization – OLED microdisplays

Smart glasses and wearables are not only a trend but open a wide range of applications in different areas.

As fitness trackers they monitor heart rate, pulse and other vital parameters or remind its user about necessary medications. In the industrial sector data glasses enable to support e.g. construction work by displaying additional information to the user, so that he is not forced to remove hands from work.

Therefore display technology plays an important role for the presentation of this virtual reality. Because of their technological advantages OLED microdisplays come more and more to the fore. Fraunhofer FEP has been working for years on the development and production of OLED microdisplays, based on organic semiconductors. The additional integration of an image sensor directly within the microdisplay enables the tracking e.g. of the eye movement with data glasses or the controlling of display content. With the help of the so-called bi-directional OLED microdisplays (e.g. resolution of 800 x 600 pixels x RGBW), which are developed by Fraunhofer FEP, the function of “wearable displays” and hands-free eye controlled systems are joined together for the usage of for example augmented-reality-glasses or human-ma­chine interaction. Current problem of smart glasses is the short battery runtime. Meantime particularly ultralow-power displays have been developed with an extremely low power consumption. Furthermore large-area OLED microdisplays for augmented and virtual reality applications have been developed, for example for prosthetics for people with impaired vision or bendable displays.

Organic light-emitting diodes (OLEDs) – flexible light source for universal application

Organic semiconductors enable large area components, for example organic light-emitting diodes (OLEDs) on flexible substrates. In contrast to point light sources like LEDs made of inorganic semiconductor crystals, organic light-emitting diodes (OLEDs) are light-emitting surfaces. Their light attains a new level of homogeneity and can be dimmed smoothly. The light does not throw harsh shadows and requires no reflectors, light pipes, or similar optics. This makes OLED light sources efficient and light-weight, and they require no supplemental cooling. OLEDs can be applied to flexible and bendable substrates and arbitrarily shaped, so they establish an entirely new world of design as well as a wide range of new possibilities for special lighting applications e.g. in medical applications for light the­rapy, in architecture or transport sector as a lightweight lighting opportunity.

Devices on thin substrates like metal- and polymer films or ultrathin flexible glass enable to create integrated light sources on curved surfaces. A possible transparency or color variability are also of particular importance.

The organic layers of the OLED are sensitive to oxygen and moisture and needs to be well protected. Flexible ultra-thin glass substrate meets the stringent requirements of a hermetic barrier, free of defects and pinhole freedom for large OLED emissive surfaces. Fraunhofer FEP has had success not only in applying OLEDs to flexible ultra-thin glass, but also in encapsulating the devices using an additional thin glass layer in a single roll-to-roll manufacturing step.

Fraunhofer FEP has an extensive know-how along the entire value chain for the development of flexible OLED-modules: from a bare substrate to an integrated luminaire. We offer our customers and partners R&D services for each step of the value chain up to customized layouts on prototypes for small batch series. The OLED-deposition at Fraunhofer FEP can be done in Roll-to-Roll (R2R) and Sheet-to-Sheet (S2S) processes, based on our line of research. In R2R it is possible to produce endless long stripes with up to 30 lm/W and in S2S high quality OLEDs with a high performance can be produced. As substrates the pilot line mainly uses plastic web and ultra-thin-glass.

Producing wholesome seed product on site

Providing the expanding population with healthy foodstuffs is an enormous challenge whose solution begins very early in the production chain. Besides familiar conventional chemical compounds for seed dressing, an additional process exists for effective destruction of harmful pathogens like fungi and bacteria. The environmentally friendly, purely physical process for disinfection of seed product is based on the germ-killing action of accelerated electrons.

More than 15 years ago Fraunhofer developed a proven method for efficiently freeing seed products and animal feed of pathogens within a matter of seconds. The method uses low energy electrons to permanently kill germs. The method is purely physical - pathogens can hence not develop any resistance. Also, chemical residues are not a problem, meaning, for example, that excess of seed can be readily used as animal feed.

If energetic electrons strike pathogens within the target area, the pathogens are destro­yed effectively. During electron treatment, the electrons are only allowed to penetrate the seed coat to a depth that empirically precludes any influence on the embryo and endosperm within the interior of the seed kernel. Safe, non-chemical dressing of seed product has been proven during long-term development projects with independent institutes and companies. It is used for large volume seed production.

An innovative design for killing pathogens without the use of chemicals in agricultural seed inventories has been developed at Fraunhofer FEP in the year 2016. It uses an innovative concept which employs a toroidal electron source. This approach reduces the energy consumed and increases the econo­mic efficiency of the process compared to others with two electron sources – especially in the case of low throughput. This technology is available for industrial seed dressing in small and medium-sized quantities including for organic agriculture in the year 2017 already.

atmoFlex – technology for thin film coating of plastic films

Because of low specific weight, cost-effective production and simple processing, plastic films are used in many industry sectors. To adapt the foil and its characteristics to its application, volume properties and surface coating have to be modified. Therefore it is possible to provide packaging foils with transparent barrier layers or to cure printing inks and varnishes with low-energy electrons.

Fraunhofer FEP has been pushing the technology development for thin-film coatings on plastic film for years. The basis for these advances has been its roll-to-roll process lines that facilitate the development of coating systems, from lab-scale to prototype samples, up through initial pilot manufacturing for industrial applications. After commissioning and testing during the past year, the new atmoFlex system has come on-line to broa­den Fraunhofer FEP’s capabilities by offering processing at standard atmospheric pressure. Films used for a wide range of applications can be coated with the new process line, from decorative film for furniture to permeation barriers for food packaging and organic electronics. Specialized modifications to the conveyor design permit the utilization of both smooth and textured films so that either high-gloss surfaces or decorative finishes can be produced for furnishings, for example. High temperatures normally necessary for drying coatings can impair very thin substrate films. An alternative drying and curing process is therefore employed in atmoFlex. This new process uses electron beams for curing coatings as well as for surface treatment. The electron beams are even able to penetrate a protective film applied over top and cure the layers beneath. Processing under clean-room conditions to keep layers free of particulates is therefore not necessary.

But the new process line is capable of treating not only plastic films. It is also available for coating other flexible substrates such as metal foil, thin glass, and textiles. Substrates widths up to 1,250 mm can be processed at speeds of up to 150 m/min. The modular character of the process line also offers sufficient adaptability for integra­ting future technological advancements and researching new processes.

In the field of coating of flexible substrates the interrelations­hips of individual technologies are currently being investigated. Especially the fabrication of improved systems of barrier coatings for functional films with PVD layers in combina­tion with varnishes and cured by electron beams. Besides permeation barrier perfor­mance, the research is particularly focusing on optical properties. More sensitive and ultra-thin vacuum coatings could be protected by the new atmoFlex line, for example by coating layers which are applied under standard atmosphere. These combination of layers are reliable applications even in external use.