In RA A – Optical data storage and exchange, we began investigating alternative processing techniques to fabricate digital luminescence systems, exploring vacuum deposition versus the standard wet processing (spin or blade coating). We identified various small molecule host and guest systems enabling efficient room temperature phosphorescence—the key requirement for the active layer. In parallel, we tested dry-processing techniques for oxygen barrier layers, which proved more challenging, but found two suitable materials showing first indications of the needed barrier properties. We successfully realized a complete PLT entirely via dry processing. All results required for a scientific publication are achieved, expected late 2026; IP application will be evaluated alongside manuscript development. We also focused on adding functionality to our PLT technology through additional absorptive layers for functional contrast, heating elements for controlled deactivation, and mixed active layer composites for activation time control—all developed into projects we follow up on for independent publications. By processing PLTs in oxygen-free environments, we realized a system that is in its on state directly after processing, a study giving insights into PLT working principles, which we currently conclude.
In RA B – Time-domain security, we initially focused on understanding and expanding the parameter space enabling tuneability of digital luminescence systems. As a first fundamental step, we investigated reproducibility via a round-robin test across the entire SLOWTONICS team, where each member repeatedly fabricated PLTs following a common recipe. The outcome is very encouraging: basic PLT characteristics stay within small margins, allowing controlled variations. We then explored emitter concentration, host polymer materials and chain length, oxygen barrier layer thickness, annealing conditions, and RTP emitter molecules. While this work alone does not ground a publication, the insights are essential for all follow-up work. Starting in year 3, we will apply these insights to develop time-domain security features.
In RA C – Sensor systems, we have developed a PLT-based system to determine beam profiles of various light sources in a minimalistic fashion. After sequential optimization steps, we are finalizing the project and expect both IP application and peer-review publication by end of 2026. We fully achieved our objective, notably the ability to scale sensor dimensions from sub-millimeter to double-digit centimeter scale—a clear step beyond the state of the art. We also finalized a study using Digital Luminescence for UV dosimetry sensors.
In RA D – New and sustainable materials, we pursued synthetic materials and natural emitters in parallel. In the synthetic approach, we synthesize new materials based on computational design suggestions; we have already identified multiple new materials and published findings on systematic variation of emitter sub-units. We also identified quinoline alkaloids (quinine being a well-known dye) as effective RTP emitters, and further RTP emitter design series are complete and in final manuscript development. We tested more than 10 biopolymers for active layer host or oxygen barrier use. As proof-of-concept, we developed a PLT-like coating applied to a banana's outer shell that showed full functionality. Additionally, we completed a detailed study combining device parameter variations, careful imaging, and model development for data extraction to determine oxygen diffusion in PLTs.
