Identification number: 1.1.1.3/1./24/A/077
Type: European Regional Development Fund (ERDF)
Duration: 01.06.2025 - 31.05.2028.
Project Leader: Dr. Juris Purāns, Institute of Solid State Physics University of Latvia (ISSP UL)
Responsible person from ISSP UL: Dr. Juris Purāns, ISSP UL
Project partners: Sidrabe Vacuum Ltd, AGL Technologies Ltd.
Total funding: 651 899 EUR
ERDF funding: 506 249 EUR
Aim:
The objective of this project is to develop and optimize advanced roll-to-roll (R2R) deposition technologies for large-scale production of functional coatings, with a focus on applications in Smart Windows and Antimicrobial Coatings (R2R-SWAC).
Summary:
The project aims to deposit thin films of photochromic yttrium oxyhydride (YHO), photocatalytic zinc ferrite (ZnxFe3−xO4), and hydrophobic mixed metal oxides (e.g., TiO2, ZnO, SnO2) with tailored chemical, structural, and functional properties using scalable magnetron sputtering techniques, including high power impulse magnetron sputtering (HiPIMS). The project targets achieving a Technology Readiness Level (TRL) of 4. Project duration - 36 months.
Expected Outcomes and Deliverables:
Innovative YHO Thin Films: Durable and scalable photochromic coatings for smart windows, demonstrated through prototype production and a scientific publication.
Advanced Antimicrobial Coatings: Ferrite photocatalytic compounds and hydrophobic metal oxides to prevent microbial contamination – scientific publications.
Optimized HiPIMS Technology: Scalable and cost-effective R2R magnetron sputtering for large-area coatings – a patent application
Tasks at ISSP UL:
Preparation of thin-film deposition equipment for both laboratory-scale and large-area Roll-to-Roll (R2R) systems.
Development and optimization of hydrophobic metal oxide (e.g., TiO₂, ZnO, SnO₂) deposition processes at the laboratory scale on glass and polymer substrates, using both pulsed-DCMS and HiPIMS techniques, including adjustment of deposition parameters to modify surface morphology and chemistry.
Development and optimization of photocatalytic ZnxFe₃−xO₄ deposition processes at the laboratory scale on glass and polymer substrates, with tuning of deposition parameters to alter structure and increase surface roughness.
Transfer of the most effective antimicrobial coating deposition process to the R2R system, including optimization of deposition parameters and polymer pre-treatment.
PROJECT PROGRESS
Time period: 01.06.2026. – 31.08.2026.
Photochromic Coatings Research
The fabrication of a new series of laboratory-scale YHO samples is ongoing. The effects of different oxidation conditions and temperatures on the photochromic properties and long-term stability of the resulting films are being systematically investigated. Sample stability is being evaluated in detail using optical microscopy to monitor visual and morphological changes in the films over time.
During this stage of the project, we began the fabrication of R2R-sized YHO samples on the UV80 equipment for (a) a series with an Al protective coating and (b) a series with a variable pumping speed. A study was conducted on the relationship between the film thickness and the effective thickness of the active layer, as well as on the dependence of the darkening process dynamics on the PET substrate side and thickness.
Antimicrobial Coatings Research
The fabrication of ZnO and TiO2-ZnO thin films and the optimisation of their technological parameters are ongoing. TiO2-ZnO heterostructures have been produced, with each layer deposited under previously determined optimal conditions. Methods for controlling the surface structure of the coatings and improving their hydrophobic properties are being investigated. For this purpose, a separate vacuum system has been developed for modifying the coating surfaces using a fluorine-containing compound.
Testing of the antimicrobial performance of the coatings is continuing. Bacterial cells are incubated on the coating surfaces, after which their ability to regrow is evaluated. The development of a new experimental testing method using the luminescent biofilm-forming bacterium Pseudomonas fluorescens has also begun.
Time period: 01.03.2026. - 31.05.2026.
Photochromic Coatings Research
The fabrication of a new series of YHO samples (laboratory scale) has been initiated, systematically varying the thin-film deposition power to evaluate its influence on the physical properties of the material. For each selected power regime, the deposition pressure is also optimised to ensure that the process is carried out under optimal technological conditions. In addition, experiments are being conducted using different substrates and yttrium targets to determine their effect on the stability of the deposited films.
During this stage of the project, series of photochromically active samples were produced on PET substrates using the UV80 deposition system to calibrate optical thickness measurements by profilometry. Additional samples were prepared to evaluate the influence of vacuum chamber exposure to the atmosphere on photochromic properties under different process scenarios. The fabricated samples have been transferred to ISSP UL for further investigation. An aluminium magnetron was also prepared and tested for the deposition of protective coatings.
The YHO samples were characterised by photochromic property measurements, X-ray diffraction (XRD), and UV–Vis–NIR spectroscopy. For selected samples, the chemical composition was determined using the ToF-ERDA method at the Accelerator Laboratory of the University of Helsinki. The long-term stability of the samples is being monitored through periodic optical microscopy measurements.
Antimicrobial Coatings Research
TiO2–ZnO heterostructured thin films were fabricated, with each layer deposited using previously determined optimal technological parameters. The ZnO and TiO2–ZnO samples were characterised by X-ray diffraction (XRD) to analyse their structure, while their optical properties were investigated using UV–Vis–NIR spectrophotometry and spectroscopic ellipsometry.
The contact angles between liquid droplets and the coating surfaces of the ZnO and TiO2–ZnO thin-film samples were measured using a Drop Shape Analyzer. Antimicrobial performance tests of TiO2 and TiO2–ZnO Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) bacterial cells. At the same time, efforts have begun to improve the testing methodology in order to assess the ability of the coatings to inhibit biofilm formation.
Time period: 01.12.2025. - 28.02.2026.
Photochromic Coatings Research
At this stage of the project, experiments were carried out on the UV80 system and series of samples were produced both for determining the operating parameters and for evaluating the repeatability of YHO deposition. A series of samples with a pronounced photochromic effect was fabricated at different working pressures and the samples were transferred to ISSP UL for further investigation. The initial bleaching dynamics of the samples and their interaction with light sources were examined. Darkening of the samples during transmittance measurements was observed, and solutions to eliminate this effect are currently being sought.
At the ISSP UL, the deposited samples were further analysed to determine their structure and optical properties, including their photochromic behaviour. The results show the expected atomic structure and promising photochromic characteristics. Based on these findings, feedback and recommendations on optimal production parameters have been provided back to Sidrabe Vacuum for the preparation of the next series of samples. The stability of the samples is being evaluated using optical microscopy, and these studies are ongoing.
Antimicrobial Coatings Research
Zinc oxide (ZnO) thin film samples have been prepared on glass and PET substrates using reactive magnetron sputtering at different points of the process curves, as well as by performing deposition under an angle. The structure and optical properties of the samples have been studied. The hydrophobicity of TiO2 and ZnO thin films has been evaluated using a Drop Shape Analyzer by measuring the contact angle between the liquid and the film surface. A vacuum system for surface modification (functionalisation) to improve hydrophobicity has been designed, and the first tests have been carried out, showing an improvement in hydrophobicity.
Time period: 01.09.2025. - 30.11.2025.
Photochromic Coatings Research
Test samples of YHO thin films were fabricated on six different flexible polymer substrates using the G500M system, and the film quality was evaluated by optical microscopy. YHO films with an Al2O3 protective layer were produced to assess the influence of the protective layer on changes in chemical composition and photochromic properties over time.
The control system of the UV80 system was upgraded and supplemented with the connections and hardware required for the experiments, and software was developed and tested to ensure efficient plasma emission monitoring. Initial test processes were launched to determine YHO operating regimes and to investigate the dynamics of the reactive process.
Antimicrobial Coatings Research
A feedback control system for the reactive sputtering process was developed to ensure process stability by automatically regulating the reactive gas flow. Fabrication of TiO2 thin-film samples from both ceramic and metallic targets was completed using two different operating modes – pulsed DC and HiPIMS. The samples were prepared at different points of the process curves (hysteresis loops) for each mode. Oblique-angle deposition of the films was performed. The samples were characterised in terms of optical properties and surface tension.
Time period: 01.06.2025. - 31.08.2025.
Photochromic coatings research:
The laboratory system G500M has been prepared for small-scale fabrication of photochromic YHO thin films. The first YHO samples were produced on amorphous quartz substrates and characterised – structure, optical, and photochromic properties were determined. The roll-to-roll (R2R) system UV80 was adapted to specific requirements, the yttrium target was prepared, the gas system optimised, and the equipment performance tested. Both G500M and UV80 are equipped with magnetron sputtering technology. The necessary materials for sample fabrication have been purchased.
Antimicrobial coatings research:
The laboratory system G500M.1 has been prepared for the fabrication of antimicrobial coatings, including modification of the vacuum system and establishment of a control system, which is still in progress. The first TiO2 samples were fabricated under different conditions on glass and PET substrates. Thickness and roughness measurements were performed, as well as determination of surface tension. The necessary materials for sample fabrication and testing have been purchased.