One of the very first tasks of the FABulous Project was the identification of the application-driven requirements for the surface structures to be manufactured during the project and the laser writing process based on the two photon polymerization technique. These requirements were then translated into specifications to guide the further technical developments from both manufacturing and design points of view, prior to the upscaling of the technology and its final demonstration. In this way, the complete definition of process and products specifications were established, together with the collection of all the information required for the environmental benchmarking analysis.
The manufacturing and design technologies were developed in parallel to the definition of the application driven requirements and benchmarking specifications. To this regard, a huge amount of work was devoted to the development of the manufacturing process of nanostructures with lateral sizes within the range of a very few hundred of nanometers, making use of advanced parallelization techniques involving the use of diffractive optics and/or DMDs. The work started with the definition of the optics that would be needed for the fabrication of such structures through the parallel approach, in collaboration with some of the best optical designers and companies from the field. The manufacturing process was developed as well, making particular emphasis on both the development of suitable materials for high resolution and productivity that could, in turn, provide a refractive index high enough to fabricate efficient optical metasurfaces, and the optimization of the productivity of Two photon polymerization through advanced beam shaping techniques while maintaining, and improving, when possible, its resolution. Thus, structures with a metalens-like design where the pillars are varying in height and diameter were fabricated with the developed materials, achieving a control of diameter less than 50 nm and a resolution in Z axis of less than 10 nm. At the same time, several parallelization approaches (making use of Diffractive Optical Elements, Spatial Light Modulators and Digital Micromirror Devices) were at work, fabricating up to 900 pillars at the same time, with a control of the exposure intensity of each individual pixel.
The consortium also focused its effort on the development of models for the design and optimal fabrication of metasurfaces. With respect to the design of the metastructures, physical and data-driven models will be integrated into a software dedicated to the design and simulation of metasurfaces and the correction of proximity effects, combining ray tracing software with the use of electromagnetic solvers for complex physical models in a unique way to optimize the design process without resulting in a prohibitive computational load. For the manufacturing modelling side, FABulous partners developed and verified models for massively parallelized Two photon polymerization. The models supported a fabrication aware design of optical metasurfaces, enabling at the same time 3D proximity correction. A dedicated software architecture was developed to combine four different models with different levels of complexity. The comparisons with experimental data and applications demonstrated the advantages and limitations of the four different approaches
The first steps towards the integration of the technology developed in FABulous in commercial machines was initiated, starting by the analysis of the available possibilities for the deposition of the resin on 3D substrates, as a previous step for 3D metasurfaces fabrication. Several processes like Spray coating, dip coating and resin dispensing were studied, being resin dispensing the most favorable technique so far resin dispensing. Additionally, huge steps were taken into In-situ surface measurement and mapping of the surface, developing the very first prototypes for the fabrication or 3D metastructures on 3D surfaces based on differential confocal sensing. Additionally, the creation of a database containing the data structures to represent all necessary process specifications (laser parameters, wavefront calculation and illumination strategies, part positioning and movement) was carried out, laying out the basis for the fabrication of more efficient parallel nanofabrication based on the use of Spatial Light Modulators. The architecture for such a system projecting the images of the SLM into the resin with a precise control of the projected pattern in terms of definition and positioning was carried out as well. All these developments were integrated into the existing technology platforms, as a first step towards its demonstration with three different use cases.
The first designs of the demonstrators for each corresponding use case were delivered and transferred to the manufacturing partners with the goal of fine tuning the demonstrators design according to the latest advances applied in the existing manufacturing platforms.
