Micro- and Nanoscale Fabrication Processes
The process of fabrication involves the preparation of uniquely shaped molds from a suitable liquid- or solid-state starting material. The development process begins with a concept or an idea aimed at solving a technical problem, continues with the creation of a new design using a computer (numerical simulations and / or CAD tools) and results in a strategy to translate the design into a physical object using a suitable manufacturing process.
There are many fabrication processes, each with procedural advantages and disadvantages. Laser-based methods, which have unique advantages over others, are used in the subject area "micro-and nanoscale fabrication". Due to non-linear optical effects (multiple photon absorption), it is possible to produce 3-D structures with a high level of resolution, which is not possible with other methods. The optimization of the technical application of the method has also resulted in an optimization of processing time, which allows not only individual structures, but also small batch series to be produced. This method also allows the production of custom-made tools that can be used in the replicative process. Additionally, they are suitable for the large-scale production of nanostructured surfaces (roll-to-roll nanoimprint lithography).
The specific focus of this subject area is placed on the simulation and construction of three-dimensional structures as well as on the application of innovative structuring methods in such diverse technical and scientific areas as photonics, nanotechnology, electronics, bionics or biomimicry and materials science. In addition to the optimization of the structuring methods, the strategic combination of different methods to create a shared technological platform is crucial to construct large-area structured substrates from miniscule structural units. This synergism allows for a comprehensive process, which extends from concept to product development, to stem from a single source and greatly benefit science and the industry.
Fabrication using multiphoton absorption
Multiphoton absorption allows the creation of three-dimensional structures at extremely high resolutions. Both the lithographic hardware and CAD models of the structures to be produced determine the results. This 3D fabrication method has unique technical advantages including high spatial resolution, true 3D capability, unparalleled flexibility of design and high structural surface quality.
Caption: Various interactions determine the different technical possibilities of the structuring process. During the absorption of single photons (left), the entire thickness of the photosensitive material is exposed enabling the two-photon absorption process to create 3D structures within the material
Pioneering lithography methods for the future
Ideas, concepts and discoveries arising during simulations of various physical processes (including optical simulations), in the form of geometric modelling data, can be rapidly implemented in suitable materials by using direct writing methods such as direct laser writing and 3D laser lithography that rely on two- or multiphoton polymerisation or electron beam lithography techniques. In addition, we offer standard methods of lithography for the preparation of master structures such as photolithography and methods for replicating templates (stamps, master patterns) such as nanoimprint lithography and soft lithography. These can be combined with a UV excimer laser-based step-and-repeat process or scaled up for roll-to-roll production in a pilot plant for the production of flexible film substrates in the related field "R2R Processing and Mastering".
Optical Simulations, Computer-Aided Design and Computer-Aided Manufacturing
At the beginning of each developmental process, concepts or ideas are frequently brought into concrete form with the help of computer-based developmental tools. In the field of photonics, we have versatile tools that can be used during the simulation and development of photonic or light engineering problems. The possibilities range from simple optimization of imaging systems to the development of refractive and diffractive micro-optics and on to the simulation of complete optical systems, e.g., lighting and sensor systems. By using appropriate CAD interfaces, useful components can be quickly imported and the processed simulation results for use in production can be exported. The laser-based additive manufacturing methods that are available in-house for use with photopolymers allow the direct translation of simulation models into physical structures.
Design and Manufacture of integrated optical Data Links on printed circuit boards
3D processes of production provide new solutions to technical problems. Using multiphoton laser-based lithography to directly integrate optical data links is an innovative approach that makes the subsequent coupling of the waveguide to components such as lasers and photodiodes superfluous. The assembled PCB is first completely coated with waveguide material that can be structured in a suitable way, whereby the components are fully embedded in the optical layer. Then the component positions are measured to determine the fiber endpoints. In this way, the alignment and coupling of the waveguide becomes a direct part of the manufacturing process. According to the way the waveguide path is defined, the optical link (the core of the waveguide) is written using a laser focus in the optical material. The laser exposure creates a localized increase in the refractive index, while the unexposed portion of the optical layer serves as the waveguide cladding.
Diffractive Optical Structures
Modern optics must function under ever more stringent conditions, such as those related to minimal installation areas and maximum efficiency. Conventional refractive optics easily reach their limits. In contrast, diffractive optical elements (DOE) display very low overall heights, meaning that they can be more easily integrated into optical systems. Likewise, such optics can be readily produced on a large scale by using a roll-to-roll based manufacturing process.
In addition to laser-based direct-write techniques, the process of electron-beam lithography offers another method of producing high-resolution nanostructures by directly drawing structures into suitable material. A focused electron beam is moved in a raster scan pattern over a surface covered with an electron sensitive film called a resist to expose particular regions. After a developing step, the structured resist acts as a template for subsequent etching processes and can be used to transfer the drawn structures on to another substrate (for example, silicon wafers).
Bionics (also called biomimicry or biomimetics) is a highly interdisciplinary field that adapts ideas and concepts taken from nature by understanding the principle of their natural functions and converts these into technical solutions. Structures and their surface properties often play a central role in bionics. Through alterations of structural properties, material properties and functions can be expanded. The related technical adaptations require appropriate structuring methods and materials for applications in areas such as biomimetic surfaces that have stain-resistant, hydrophobic and / or hydrophilic properties or optically refractive and diffractive surfaces, textured chromophoric surfaces and structured electrodes or sensors that are used and optimized in various research projects.